Initial Spring 2016 commit.

2015-12-23 00:50:04 +00:00
commit cafa9f5690
732 changed files with 92195 additions and 0 deletions
--- a/userland/sbin/Makefile
+++ b/userland/sbin/Makefile
@@ -0,0 +1,10 @@
+#
+# Makefile for src/sbin (sources for programs installed in /sbin)
+#
+
+TOP=../..
+.include "$(TOP)/mk/os161.config.mk"
+
+SUBDIRS=reboot halt poweroff mksfs dumpsfs sfsck
+
+.include "$(TOP)/mk/os161.subdir.mk"
--- a/userland/sbin/dumpsfs/Makefile
+++ b/userland/sbin/dumpsfs/Makefile
@@ -0,0 +1,15 @@
+# Makefile for dumpsfs
+
+TOP=../../..
+.include "$(TOP)/mk/os161.config.mk"
+
+PROG=dumpsfs
+SRCS=dumpsfs.c ../mksfs/disk.c ../mksfs/support.c
+CFLAGS+=-I../mksfs
+HOST_CFLAGS+=-I../mksfs
+BINDIR=/sbin
+HOSTBINDIR=/hostbin
+
+
+.include "$(TOP)/mk/os161.prog.mk"
+.include "$(TOP)/mk/os161.hostprog.mk"
--- a/userland/sbin/dumpsfs/dumpsfs.c
+++ b/userland/sbin/dumpsfs/dumpsfs.c
@@ -0,0 +1,607 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009, 2014
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/types.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <limits.h>
+#include <err.h>
+
+#include "support.h"
+#include "kern/sfs.h"
+
+
+#ifdef HOST
+/*
+ * OS/161 runs natively on a big-endian platform, so we can
+ * conveniently use the byteswapping functions for network byte order.
+ */
+#include <netinet/in.h> // for arpa/inet.h
+#include <arpa/inet.h>  // for ntohl
+#include "hostcompat.h"
+#define SWAP64(x) ntohll(x)
+#define SWAP32(x) ntohl(x)
+#define SWAP16(x) ntohs(x)
+
+extern const char *hostcompat_progname;
+
+#else
+
+#define SWAP64(x) (x)
+#define SWAP32(x) (x)
+#define SWAP16(x) (x)
+
+#endif
+
+#include "disk.h"
+
+#define ARRAYCOUNT(a) (sizeof(a) / sizeof((a)[0]))
+#define DIVROUNDUP(a, b) (((a) + (b) - 1) / (b))
+
+static bool dofiles, dodirs;
+static bool doindirect;
+static bool recurse;
+
+////////////////////////////////////////////////////////////
+// printouts
+
+static unsigned dumppos;
+
+static
+void
+dumpval(const char *desc, const char *val)
+{
+	size_t dlen, vlen, used;
+
+	dlen = strlen(desc);
+	vlen = strlen(val);
+
+	printf("    ");
+
+	printf("%s: %s", desc, val);
+
+	used = dlen + 2 + vlen;
+	for (; used < 36; used++) {
+		putchar(' ');
+	}
+
+	if (dumppos % 2 == 1) {
+		printf("\n");
+	}
+	dumppos++;
+}
+
+static
+void
+dumpvalf(const char *desc, const char *valf, ...)
+{
+	va_list ap;
+	char buf[128];
+
+	va_start(ap, valf);
+	vsnprintf(buf, sizeof(buf), valf, ap);
+	va_end(ap);
+	dumpval(desc, buf);
+}
+
+static
+void
+dumplval(const char *desc, const char *lval)
+{
+	if (dumppos % 2 == 1) {
+		printf("\n");
+		dumppos++;
+	}
+	printf("    %s: %s\n", desc, lval);
+	dumppos += 2;
+}
+
+////////////////////////////////////////////////////////////
+// fs structures
+
+static void dumpinode(uint32_t ino, const char *name);
+
+static
+uint32_t
+readsb(void)
+{
+	struct sfs_superblock sb;
+
+	diskread(&sb, SFS_SUPER_BLOCK);
+	if (SWAP32(sb.sb_magic) != SFS_MAGIC) {
+		errx(1, "Not an sfs filesystem");
+	}
+	return SWAP32(sb.sb_nblocks);
+}
+
+static
+void
+dumpsb(void)
+{
+	struct sfs_superblock sb;
+	unsigned i;
+
+	diskread(&sb, SFS_SUPER_BLOCK);
+	sb.sb_volname[sizeof(sb.sb_volname)-1] = 0;
+
+	printf("Superblock\n");
+	printf("----------\n");
+	dumpvalf("Magic", "0x%8x", SWAP32(sb.sb_magic));
+	dumpvalf("Size", "%u blocks", SWAP32(sb.sb_nblocks));
+	dumpvalf("Freemap size", "%u blocks",
+		 SFS_FREEMAPBLOCKS(SWAP32(sb.sb_nblocks)));
+	dumpvalf("Block size", "%u bytes", SFS_BLOCKSIZE);
+	dumplval("Volume name", sb.sb_volname);
+
+	for (i=0; i<ARRAYCOUNT(sb.reserved); i++) {
+		if (sb.reserved[i] != 0) {
+			printf("    Word %u in reserved area: 0x%x\n",
+			       i, SWAP32(sb.reserved[i]));
+		}
+	}
+	printf("\n");
+}
+
+static
+void
+dumpfreemap(uint32_t fsblocks)
+{
+	uint32_t freemapblocks = SFS_FREEMAPBLOCKS(fsblocks);
+	uint32_t i, j, k, bn;
+	uint8_t data[SFS_BLOCKSIZE], mask;
+	char tmp[16];
+
+	printf("Free block bitmap\n");
+	printf("-----------------\n");
+	for (i=0; i<freemapblocks; i++) {
+		diskread(data, SFS_FREEMAP_START+i);
+		printf("    Freemap block #%u in disk block %u: blocks %u - %u"
+		       " (0x%x - 0x%x)\n",
+		       i, SFS_FREEMAP_START+i,
+		       i*SFS_BITSPERBLOCK, (i+1)*SFS_BITSPERBLOCK - 1,
+		       i*SFS_BITSPERBLOCK, (i+1)*SFS_BITSPERBLOCK - 1);
+		for (j=0; j<SFS_BLOCKSIZE; j++) {
+			if (j % 8 == 0) {
+				snprintf(tmp, sizeof(tmp), "0x%x",
+					 i*SFS_BITSPERBLOCK + j*8);
+				printf("%-7s ", tmp);
+			}
+			for (k=0; k<8; k++) {
+				bn = i*SFS_BITSPERBLOCK + j*8 + k;
+				mask = 1U << k;
+				if (bn >= fsblocks) {
+					if (data[j] & mask) {
+						putchar('x');
+					}
+					else {
+						putchar('!');
+					}
+				}
+				else {
+					if (data[j] & mask) {
+						putchar('*');
+					}
+					else {
+						putchar('.');
+					}
+				}
+			}
+			if (j % 8 == 7) {
+				printf("\n");
+			}
+			else {
+				printf(" ");
+			}
+		}
+	}
+	printf("\n");
+}
+
+static
+void
+dumpindirect(uint32_t block)
+{
+	uint32_t ib[SFS_BLOCKSIZE/sizeof(uint32_t)];
+	char tmp[128];
+	unsigned i;
+
+	if (block == 0) {
+		return;
+	}
+	printf("Indirect block %u\n", block);
+
+	diskread(ib, block);
+	for (i=0; i<ARRAYCOUNT(ib); i++) {
+		if (i % 4 == 0) {
+			printf("@%-3u   ", i);
+		}
+		snprintf(tmp, sizeof(tmp), "%u (0x%x)",
+			 SWAP32(ib[i]), SWAP32(ib[i]));
+		printf("  %-16s", tmp);
+		if (i % 4 == 3) {
+			printf("\n");
+		}
+	}
+}
+
+static
+uint32_t
+traverse_ib(uint32_t fileblock, uint32_t numblocks, uint32_t block,
+	    void (*doblock)(uint32_t, uint32_t))
+{
+	uint32_t ib[SFS_BLOCKSIZE/sizeof(uint32_t)];
+	unsigned i;
+
+	if (block == 0) {
+		memset(ib, 0, sizeof(ib));
+	}
+	else {
+		diskread(ib, block);
+	}
+	for (i=0; i<ARRAYCOUNT(ib) && fileblock < numblocks; i++) {
+		doblock(fileblock++, SWAP32(ib[i]));
+	}
+	return fileblock;
+}
+
+static
+void
+traverse(const struct sfs_dinode *sfi, void (*doblock)(uint32_t, uint32_t))
+{
+	uint32_t fileblock;
+	uint32_t numblocks;
+	unsigned i;
+
+	numblocks = DIVROUNDUP(SWAP32(sfi->sfi_size), SFS_BLOCKSIZE);
+
+	fileblock = 0;
+	for (i=0; i<SFS_NDIRECT && fileblock < numblocks; i++) {
+		doblock(fileblock++, SWAP32(sfi->sfi_direct[i]));
+	}
+	if (fileblock < numblocks) {
+		fileblock = traverse_ib(fileblock, numblocks,
+					SWAP32(sfi->sfi_indirect), doblock);
+	}
+	assert(fileblock == numblocks);
+}
+
+static
+void
+dumpdirblock(uint32_t fileblock, uint32_t diskblock)
+{
+	struct sfs_direntry sds[SFS_BLOCKSIZE/sizeof(struct sfs_direntry)];
+	int nsds = SFS_BLOCKSIZE/sizeof(struct sfs_direntry);
+	int i;
+
+	(void)fileblock;
+	if (diskblock == 0) {
+		printf("    [block %u - empty]\n", diskblock);
+		return;
+	}
+	diskread(&sds, diskblock);
+
+	printf("    [block %u]\n", diskblock);
+	for (i=0; i<nsds; i++) {
+		uint32_t ino = SWAP32(sds[i].sfd_ino);
+		if (ino==SFS_NOINO) {
+			printf("        [free entry]\n");
+		}
+		else {
+			sds[i].sfd_name[SFS_NAMELEN-1] = 0; /* just in case */
+			printf("        %u %s\n", ino, sds[i].sfd_name);
+		}
+	}
+}
+
+static
+void
+dumpdir(uint32_t ino, const struct sfs_dinode *sfi)
+{
+	int nentries;
+
+	nentries = SWAP32(sfi->sfi_size) / sizeof(struct sfs_direntry);
+	if (SWAP32(sfi->sfi_size) % sizeof(struct sfs_direntry) != 0) {
+		warnx("Warning: dir size is not a multiple of dir entry size");
+	}
+	printf("Directory contents for inode %u: %d entries\n", ino, nentries);
+	traverse(sfi, dumpdirblock);
+}
+
+static
+void
+recursedirblock(uint32_t fileblock, uint32_t diskblock)
+{
+	struct sfs_direntry sds[SFS_BLOCKSIZE/sizeof(struct sfs_direntry)];
+	int nsds = SFS_BLOCKSIZE/sizeof(struct sfs_direntry);
+	int i;
+
+	(void)fileblock;
+	if (diskblock == 0) {
+		return;
+	}
+	diskread(&sds, diskblock);
+
+	for (i=0; i<nsds; i++) {
+		uint32_t ino = SWAP32(sds[i].sfd_ino);
+		if (ino==SFS_NOINO) {
+			continue;
+		}
+		sds[i].sfd_name[SFS_NAMELEN-1] = 0; /* just in case */
+		dumpinode(ino, sds[i].sfd_name);
+	}
+}
+
+static
+void
+recursedir(uint32_t ino, const struct sfs_dinode *sfi)
+{
+	int nentries;
+
+	nentries = SWAP32(sfi->sfi_size) / sizeof(struct sfs_direntry);
+	printf("Reading files in directory %u: %d entries\n", ino, nentries);
+	traverse(sfi, recursedirblock);
+	printf("Done with directory %u\n", ino);
+}
+
+static
+void dumpfileblock(uint32_t fileblock, uint32_t diskblock)
+{
+	uint8_t data[SFS_BLOCKSIZE];
+	unsigned i, j;
+	char tmp[128];
+
+	if (diskblock == 0) {
+		printf("    0x%6x  [sparse]\n", fileblock * SFS_BLOCKSIZE);
+		return;
+	}
+
+	diskread(data, diskblock);
+	for (i=0; i<SFS_BLOCKSIZE; i++) {
+		if (i % 16 == 0) {
+			snprintf(tmp, sizeof(tmp), "0x%x",
+				 fileblock * SFS_BLOCKSIZE + i);
+			printf("%8s", tmp);
+		}
+		if (i % 8 == 0) {
+			printf("  ");
+		}
+		else {
+			printf(" ");
+		}
+		printf("%02x", data[i]);
+		if (i % 16 == 15) {
+			printf("  ");
+			for (j = i-15; j<=i; j++) {
+				if (data[j] < 32 || data[j] > 126) {
+					putchar('.');
+				}
+				else {
+					putchar(data[j]);
+				}
+			}
+			printf("\n");
+		}
+	}
+}
+
+static
+void
+dumpfile(uint32_t ino, const struct sfs_dinode *sfi)
+{
+	printf("File contents for inode %u:\n", ino);
+	traverse(sfi, dumpfileblock);
+}
+
+static
+void
+dumpinode(uint32_t ino, const char *name)
+{
+	struct sfs_dinode sfi;
+	const char *typename;
+	char tmp[128];
+	unsigned i;
+
+	diskread(&sfi, ino);
+
+	printf("Inode %u", ino);
+	if (name != NULL) {
+		printf(" (%s)", name);
+	}
+	printf("\n");
+	printf("--------------\n");
+
+	switch (SWAP16(sfi.sfi_type)) {
+	    case SFS_TYPE_FILE: typename = "regular file"; break;
+	    case SFS_TYPE_DIR: typename = "directory"; break;
+	    default: typename = "invalid"; break;
+	}
+	dumpvalf("Type", "%u (%s)", SWAP16(sfi.sfi_type), typename);
+	dumpvalf("Size", "%u", SWAP32(sfi.sfi_size));
+	dumpvalf("Link count", "%u", SWAP16(sfi.sfi_linkcount));
+	printf("\n");
+
+        printf("    Direct blocks:\n");
+        for (i=0; i<SFS_NDIRECT; i++) {
+		if (i % 4 == 0) {
+			printf("@%-2u    ", i);
+		}
+		/*
+		 * Assume the disk size might be > 64K sectors (which
+		 * would be 32M) but is < 1024K sectors (512M) so we
+		 * need up to 5 hex digits for a block number. And
+		 * assume it's actually < 1 million sectors so we need
+		 * only up to 6 decimal digits. The complete block
+		 * number print then needs up to 16 digits.
+		 */
+		snprintf(tmp, sizeof(tmp), "%u (0x%x)",
+			 SWAP32(sfi.sfi_direct[i]), SWAP32(sfi.sfi_direct[i]));
+		printf("  %-16s", tmp);
+		if (i % 4 == 3) {
+			printf("\n");
+		}
+	}
+	if (i % 4 != 0) {
+		printf("\n");
+	}
+	printf("    Indirect block: %u (0x%x)\n",
+	       SWAP32(sfi.sfi_indirect), SWAP32(sfi.sfi_indirect));
+	for (i=0; i<ARRAYCOUNT(sfi.sfi_waste); i++) {
+		if (sfi.sfi_waste[i] != 0) {
+			printf("    Word %u in waste area: 0x%x\n",
+			       i, SWAP32(sfi.sfi_waste[i]));
+		}
+	}
+
+	if (doindirect) {
+		dumpindirect(SWAP32(sfi.sfi_indirect));
+	}
+
+	if (SWAP16(sfi.sfi_type) == SFS_TYPE_DIR && dodirs) {
+		dumpdir(ino, &sfi);
+	}
+	if (SWAP16(sfi.sfi_type) == SFS_TYPE_FILE && dofiles) {
+		dumpfile(ino, &sfi);
+	}
+	if (SWAP16(sfi.sfi_type) == SFS_TYPE_DIR && recurse) {
+		recursedir(ino, &sfi);
+	}
+}
+
+////////////////////////////////////////////////////////////
+// main
+
+static
+void
+usage(void)
+{
+	warnx("Usage: dumpsfs [options] device/diskfile");
+	warnx("   -s: dump superblock");
+	warnx("   -b: dump free block bitmap");
+	warnx("   -i ino: dump specified inode");
+	warnx("   -I: dump indirect blocks");
+	warnx("   -f: dump file contents");
+	warnx("   -d: dump directory contents");
+	warnx("   -r: recurse into directory contents");
+	warnx("   -a: equivalent to -sbdfr -i 1");
+	errx(1, "   Default is -i 1");
+}
+
+int
+main(int argc, char **argv)
+{
+	bool dosb = false;
+	bool dofreemap = false;
+	uint32_t dumpino = 0;
+	const char *dumpdisk = NULL;
+
+	int i, j;
+	uint32_t nblocks;
+
+#ifdef HOST
+	/* Don't do this; it frobs the tty and you can't pipe to less */
+	/*hostcompat_init(argc, argv);*/
+	hostcompat_progname = argv[0];
+#endif
+
+	for (i=1; i<argc; i++) {
+		if (argv[i][0] == '-') {
+			for (j=1; argv[i][j]; j++) {
+				switch (argv[i][j]) {
+				    case 's': dosb = true; break;
+				    case 'b': dofreemap = true; break;
+				    case 'i':
+					if (argv[i][j+1] == 0) {
+						dumpino = atoi(argv[++i]);
+					}
+					else {
+						dumpino = atoi(argv[i]+j+1);
+						j = strlen(argv[i]);
+					}
+					/* XXX ugly */
+					goto nextarg;
+				    case 'I': doindirect = true; break;
+				    case 'f': dofiles = true; break;
+				    case 'd': dodirs = true; break;
+				    case 'r': recurse = true; break;
+				    case 'a':
+					dosb = true;
+					dofreemap = true;
+					if (dumpino == 0) {
+						dumpino = SFS_ROOTDIR_INO;
+					}
+					doindirect = true;
+					dofiles = true;
+					dodirs = true;
+					recurse = true;
+					break;
+				    default:
+					usage();
+					break;
+				}
+			}
+		}
+		else {
+			if (dumpdisk != NULL) {
+				usage();
+			}
+			dumpdisk = argv[i];
+		}
+	 nextarg:
+		;
+	}
+	if (dumpdisk == NULL) {
+		usage();
+	}
+
+	if (!dosb && !dofreemap && dumpino == 0) {
+		dumpino = SFS_ROOTDIR_INO;
+	}
+
+	opendisk(dumpdisk);
+	nblocks = readsb();
+
+	if (dosb) {
+		dumpsb();
+	}
+	if (dofreemap) {
+		dumpfreemap(nblocks);
+	}
+	if (dumpino != 0) {
+		dumpinode(dumpino, NULL);
+	}
+
+	closedisk();
+
+	return 0;
+}
--- a/userland/sbin/halt/Makefile
+++ b/userland/sbin/halt/Makefile
@@ -0,0 +1,12 @@
+# Makefile for halt
+
+TOP=../../..
+.include "$(TOP)/mk/os161.config.mk"
+
+PROG=halt
+SRCS=halt.c
+BINDIR=/sbin
+
+
+.include "$(TOP)/mk/os161.prog.mk"
+
--- a/userland/sbin/halt/halt.c
+++ b/userland/sbin/halt/halt.c
@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <unistd.h>
+
+/*
+ * halt - shut down system, do not reboot, do not turn off power.
+ * Usage: halt
+ *
+ * Just calls reboot() with the RB_HALT flag.
+ */
+
+int
+main(void)
+{
+	reboot(RB_HALT);
+	return 0;
+}
--- a/userland/sbin/mksfs/Makefile
+++ b/userland/sbin/mksfs/Makefile
@@ -0,0 +1,13 @@
+# Makefile for mksfs
+
+TOP=../../..
+.include "$(TOP)/mk/os161.config.mk"
+
+PROG=mksfs
+SRCS=mksfs.c disk.c support.c
+BINDIR=/sbin
+HOSTBINDIR=/hostbin
+
+
+.include "$(TOP)/mk/os161.prog.mk"
+.include "$(TOP)/mk/os161.hostprog.mk"
--- a/userland/sbin/mksfs/disk.c
+++ b/userland/sbin/mksfs/disk.c
@@ -0,0 +1,200 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <assert.h>
+#include <stdint.h>
+#include <string.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <err.h>
+
+#include "support.h"
+#include "disk.h"
+
+#define HOSTSTRING "System/161 Disk Image"
+#define BLOCKSIZE  512
+
+#ifndef EINTR
+#define EINTR 0
+#endif
+
+static int fd=-1;
+static uint32_t nblocks;
+
+/*
+ * Open a disk. If we're built for the host OS, check that it's a
+ * System/161 disk image, and then ignore the header block.
+ */
+void
+opendisk(const char *path)
+{
+	struct stat statbuf;
+
+	assert(fd<0);
+	fd = open(path, O_RDWR);
+	if (fd<0) {
+		err(1, "%s", path);
+	}
+	if (fstat(fd, &statbuf)) {
+		err(1, "%s: fstat", path);
+	}
+
+	nblocks = statbuf.st_size / BLOCKSIZE;
+
+#ifdef HOST
+	nblocks--;
+
+	{
+		char buf[64];
+		int len;
+
+		do {
+			len = read(fd, buf, sizeof(buf)-1);
+			if (len < 0 && (errno==EINTR || errno==EAGAIN)) {
+				continue;
+			}
+		} while (0);
+
+		buf[len] = 0;
+		buf[strlen(HOSTSTRING)] = 0;
+
+		if (strcmp(buf, HOSTSTRING)) {
+			errx(1, "%s: Not a System/161 disk image", path);
+		}
+	}
+#endif
+}
+
+/*
+ * Return the block size. (This is fixed, but still...)
+ */
+uint32_t
+diskblocksize(void)
+{
+	assert(fd>=0);
+	return BLOCKSIZE;
+}
+
+/*
+ * Return the device/image size in blocks.
+ */
+uint32_t
+diskblocks(void)
+{
+	assert(fd>=0);
+	return nblocks;
+}
+
+/*
+ * Write a block.
+ */
+void
+diskwrite(const void *data, uint32_t block)
+{
+	const char *cdata = data;
+	uint32_t tot=0;
+	int len;
+
+	assert(fd>=0);
+
+#ifdef HOST
+	// skip over disk file header
+	block++;
+#endif
+
+	if (lseek(fd, block*BLOCKSIZE, SEEK_SET)<0) {
+		err(1, "lseek");
+	}
+
+	while (tot < BLOCKSIZE) {
+		len = write(fd, cdata + tot, BLOCKSIZE - tot);
+		if (len < 0) {
+			if (errno==EINTR || errno==EAGAIN) {
+				continue;
+			}
+			err(1, "write");
+		}
+		if (len==0) {
+			err(1, "write returned 0?");
+		}
+		tot += len;
+	}
+}
+
+/*
+ * Read a block.
+ */
+void
+diskread(void *data, uint32_t block)
+{
+	char *cdata = data;
+	uint32_t tot=0;
+	int len;
+
+	assert(fd>=0);
+
+#ifdef HOST
+	// skip over disk file header
+	block++;
+#endif
+
+	if (lseek(fd, block*BLOCKSIZE, SEEK_SET)<0) {
+		err(1, "lseek");
+	}
+
+	while (tot < BLOCKSIZE) {
+		len = read(fd, cdata + tot, BLOCKSIZE - tot);
+		if (len < 0) {
+			if (errno==EINTR || errno==EAGAIN) {
+				continue;
+			}
+			err(1, "read");
+		}
+		if (len==0) {
+			err(1, "unexpected EOF in mid-sector");
+		}
+		tot += len;
+	}
+}
+
+/*
+ * Close the disk.
+ */
+void
+closedisk(void)
+{
+	assert(fd>=0);
+	if (close(fd)) {
+		err(1, "close");
+	}
+	fd = -1;
+}
--- a/userland/sbin/mksfs/disk.h
+++ b/userland/sbin/mksfs/disk.h
@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+void opendisk(const char *path);
+
+uint32_t diskblocksize(void);
+uint32_t diskblocks(void);
+
+void diskwrite(const void *data, uint32_t block);
+void diskread(void *data, uint32_t block);
+
+void closedisk(void);
--- a/userland/sbin/mksfs/mksfs.c
+++ b/userland/sbin/mksfs/mksfs.c
@@ -0,0 +1,240 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009, 2014
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/types.h>
+#include <stdint.h>
+#include <string.h>
+#include <assert.h>
+#include <limits.h>
+#include <err.h>
+
+#include "support.h"
+#include "kern/sfs.h"
+
+
+#ifdef HOST
+
+#include <netinet/in.h> // for arpa/inet.h
+#include <arpa/inet.h>  // for ntohl
+#include "hostcompat.h"
+#define SWAP64(x) ntohll(x)
+#define SWAP32(x) ntohl(x)
+#define SWAP16(x) ntohs(x)
+
+#else
+
+#define SWAP64(x) (x)
+#define SWAP32(x) (x)
+#define SWAP16(x) (x)
+
+#endif
+
+#include "disk.h"
+
+/* Maximum size of freemap we support */
+#define MAXFREEMAPBLOCKS 32
+
+/* Free block bitmap */
+static char freemapbuf[MAXFREEMAPBLOCKS * SFS_BLOCKSIZE];
+
+/*
+ * Assert that the on-disk data structures are correctly sized.
+ */
+static
+void
+check(void)
+{
+	assert(sizeof(struct sfs_superblock)==SFS_BLOCKSIZE);
+	assert(sizeof(struct sfs_dinode)==SFS_BLOCKSIZE);
+	assert(SFS_BLOCKSIZE % sizeof(struct sfs_direntry) == 0);
+}
+
+/*
+ * Mark a block allocated.
+ */
+static
+void
+allocblock(uint32_t block)
+{
+	uint32_t mapbyte = block/CHAR_BIT;
+	unsigned char mask = (1<<(block % CHAR_BIT));
+
+	assert((freemapbuf[mapbyte] & mask) == 0);
+	freemapbuf[mapbyte] |= mask;
+}
+
+/*
+ * Initialize the free block bitmap.
+ */
+static
+void
+initfreemap(uint32_t fsblocks)
+{
+	uint32_t freemapbits = SFS_FREEMAPBITS(fsblocks);
+	uint32_t freemapblocks = SFS_FREEMAPBLOCKS(fsblocks);
+	uint32_t i;
+
+	if (freemapblocks > MAXFREEMAPBLOCKS) {
+		errx(1, "Filesystem too large -- "
+		     "increase MAXFREEMAPBLOCKS and recompile");
+	}
+
+	/* mark the superblock and root inode in use */
+	allocblock(SFS_SUPER_BLOCK);
+	allocblock(SFS_ROOTDIR_INO);
+
+	/* the freemap blocks must be in use */
+	for (i=0; i<freemapblocks; i++) {
+		allocblock(SFS_FREEMAP_START + i);
+	}
+
+	/* all blocks in the freemap but past the volume end are "in use" */
+	for (i=fsblocks; i<freemapbits; i++) {
+		allocblock(i);
+	}
+}
+
+/*
+ * Initialize and write out the superblock.
+ */
+static
+void
+writesuper(const char *volname, uint32_t nblocks)
+{
+	struct sfs_superblock sb;
+
+	/* The cast is required on some outdated host systems. */
+	bzero((void *)&sb, sizeof(sb));
+
+	if (strlen(volname) >= SFS_VOLNAME_SIZE) {
+		errx(1, "Volume name %s too long", volname);
+	}
+
+	/* Initialize the superblock structure */
+	sb.sb_magic = SWAP32(SFS_MAGIC);
+	sb.sb_nblocks = SWAP32(nblocks);
+	strcpy(sb.sb_volname, volname);
+
+	/* and write it out. */
+	diskwrite(&sb, SFS_SUPER_BLOCK);
+}
+
+/*
+ * Write out the free block bitmap.
+ */
+static
+void
+writefreemap(uint32_t fsblocks)
+{
+	uint32_t freemapblocks;
+	char *ptr;
+	uint32_t i;
+
+	/* Write out each of the blocks in the free block bitmap. */
+	freemapblocks = SFS_FREEMAPBLOCKS(fsblocks);
+	for (i=0; i<freemapblocks; i++) {
+		ptr = freemapbuf + i*SFS_BLOCKSIZE;
+		diskwrite(ptr, SFS_FREEMAP_START+i);
+	}
+}
+
+/*
+ * Write out the root directory inode.
+ */
+static
+void
+writerootdir(void)
+{
+	struct sfs_dinode sfi;
+
+	/* Initialize the dinode */
+	bzero((void *)&sfi, sizeof(sfi));
+	sfi.sfi_size = SWAP32(0);
+	sfi.sfi_type = SWAP16(SFS_TYPE_DIR);
+	sfi.sfi_linkcount = SWAP16(1);
+
+	/* Write it out */
+	diskwrite(&sfi, SFS_ROOTDIR_INO);
+}
+
+/*
+ * Main.
+ */
+int
+main(int argc, char **argv)
+{
+	uint32_t size, blocksize;
+	char *volname, *s;
+
+#ifdef HOST
+	hostcompat_init(argc, argv);
+#endif
+
+	if (argc!=3) {
+		errx(1, "Usage: mksfs device/diskfile volume-name");
+	}
+
+	check();
+
+	volname = argv[2];
+
+	/* Remove one trailing colon from volname, if present */
+	s = strchr(volname, ':');
+	if (s != NULL) {
+		if (strlen(s)!=1) {
+			errx(1, "Illegal volume name %s", volname);
+		}
+		*s = 0;
+	}
+
+	/* Don't allow slashes */
+	s = strchr(volname, '/');
+	if (s != NULL) {
+		errx(1, "Illegal volume name %s", volname);
+	}
+
+	opendisk(argv[1]);
+	blocksize = diskblocksize();
+
+	if (blocksize!=SFS_BLOCKSIZE) {
+		errx(1, "Device has wrong blocksize %u (should be %u)\n",
+		     blocksize, SFS_BLOCKSIZE);
+	}
+	size = diskblocks();
+
+	/* Write out the on-disk structures */
+	initfreemap(size);
+	writesuper(volname, size);
+	writefreemap(size);
+	writerootdir();
+
+	closedisk();
+
+	return 0;
+}
--- a/userland/sbin/mksfs/support.c
+++ b/userland/sbin/mksfs/support.c
@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * This file doesn't actually do anything any more, but I'm going to
+ * leave it here for now (and leave the mechanisms in place for building
+ * it) in case it's wanted again later on.
+ */
--- a/userland/sbin/mksfs/support.h
+++ b/userland/sbin/mksfs/support.h
@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+
+#ifdef __osf__
+/* Digital Unix (aka Compaq Tru64) */
+#define HAS_NO_SIZED_TYPES
+#endif
+
+#if defined(__sun__) && defined(__svr4__)
+/* Solaris */
+#define HAS_NO_SIZED_TYPES
+#endif
+
+/*
+ * Some systems don't have uint32_t, uint16_t, or uint8_t.
+ * (Sometime this should be changed so it gets probed by the configure script.)
+ */
+
+#ifdef HAS_NO_SIZED_TYPES
+
+#if defined(__alpha__) || defined(__alpha)
+/* Alpha processor: lp64 */
+typedef unsigned int uint32_t;
+typedef unsigned short uint16_t;
+typedef unsigned char uint8_t;
+
+#elif defined(__sparc__)
+/* Sparc processor: 32-bit or lp64 */
+typedef unsigned int uint32_t;
+typedef unsigned short uint16_t;
+typedef unsigned char uint8_t;
+
+#else
+#error "HAS_NO_SIZED_TYPES defined and I don't know what the sizes should be"
+#endif
+
+#endif
--- a/userland/sbin/poweroff/Makefile
+++ b/userland/sbin/poweroff/Makefile
@@ -0,0 +1,11 @@
+# Makefile for poweroff
+
+TOP=../../..
+.include "$(TOP)/mk/os161.config.mk"
+
+PROG=poweroff
+SRCS=poweroff.c
+BINDIR=/sbin
+
+.include "$(TOP)/mk/os161.prog.mk"
+
--- a/userland/sbin/poweroff/poweroff.c
+++ b/userland/sbin/poweroff/poweroff.c
@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <unistd.h>
+
+/*
+ * poweroff - shut down system and turn off power.
+ * Usage: poweroff
+ *
+ * Just calls reboot() with the RB_POWEROFF flag.
+ */
+
+int
+main(void)
+{
+	reboot(RB_POWEROFF);
+	return 0;
+}
--- a/userland/sbin/reboot/Makefile
+++ b/userland/sbin/reboot/Makefile
@@ -0,0 +1,11 @@
+# Makefile for reboot
+
+TOP=../../..
+.include "$(TOP)/mk/os161.config.mk"
+
+PROG=reboot
+SRCS=reboot.c
+BINDIR=/sbin
+
+.include "$(TOP)/mk/os161.prog.mk"
+
--- a/userland/sbin/reboot/reboot.c
+++ b/userland/sbin/reboot/reboot.c
@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <unistd.h>
+
+/*
+ * reboot - shut down system and reboot it.
+ * Usage: reboot
+ *
+ * Just calls reboot() with the RB_REBOOT flag.
+ */
+
+int
+main(void)
+{
+	reboot(RB_REBOOT);
+	return 0;
+}
--- a/userland/sbin/sfsck/Makefile
+++ b/userland/sbin/sfsck/Makefile
@@ -0,0 +1,18 @@
+# Makefile for sfsck
+
+TOP=../../..
+.include "$(TOP)/mk/os161.config.mk"
+
+PROG=sfsck
+SRCS=\
+	main.c pass1.c pass2.c \
+	inode.c freemap.c sb.c \
+	sfs.c utils.c \
+	../mksfs/disk.c ../mksfs/support.c
+CFLAGS+=-I../mksfs
+HOST_CFLAGS+=-I../mksfs
+BINDIR=/sbin
+HOSTBINDIR=/hostbin
+
+.include "$(TOP)/mk/os161.prog.mk"
+.include "$(TOP)/mk/os161.hostprog.mk"
--- a/userland/sbin/sfsck/compat.h
+++ b/userland/sbin/sfsck/compat.h
@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef SFSCK_H
+#define SFSCK_H
+
+/*
+ * Compat definitions.
+ */
+
+/* get uint32_t and friends */
+#include <stdint.h>
+
+/* get the additional compat stuff shared with mksfs */
+#include "support.h"
+
+#ifdef HOST
+/*
+ * OS/161 runs natively on a big-endian platform, so we can
+ * conveniently use the byteswapping functions for network byte order.
+ */
+#include <netinet/in.h> // for arpa/inet.h
+#include <arpa/inet.h>  // for ntohl
+#include "hostcompat.h"
+#define SWAP64(x) ntohll(x)
+#define SWAP32(x) ntohl(x)
+#define SWAP16(x) ntohs(x)
+
+#else
+
+#define SWAP64(x) (x)
+#define SWAP32(x) (x)
+#define SWAP16(x) (x)
+#define NO_REALLOC
+
+#endif /* HOST */
+
+#endif /* SFSCK_H */
--- a/userland/sbin/sfsck/freemap.c
+++ b/userland/sbin/sfsck/freemap.c
@@ -0,0 +1,310 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013, 2014
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/types.h>	/* for CHAR_BIT */
+#include <limits.h>	/* also for CHAR_BIT */
+#include <stdint.h>
+#include <stdio.h>
+#include <assert.h>
+#include <err.h>
+
+#include "compat.h"
+#include <kern/sfs.h>
+
+#include "utils.h"
+#include "sfs.h"
+#include "sb.h"
+#include "freemap.h"
+#include "main.h"
+
+static unsigned long blocksinuse = 0;
+static uint8_t *freemapdata;
+static uint8_t *tofreedata;
+
+/*
+ * Allocate space to keep track of the free block bitmap. This is
+ * called after the superblock is loaded so we can ask how big the
+ * volume is.
+ */
+void
+freemap_setup(void)
+{
+	size_t i, mapbytes;
+	uint32_t fsblocks, mapblocks;
+
+	fsblocks = sb_totalblocks();
+	mapblocks = sb_freemapblocks();
+	mapbytes = mapblocks * SFS_BLOCKSIZE;
+
+	freemapdata = domalloc(mapbytes * sizeof(uint8_t));
+	tofreedata = domalloc(mapbytes * sizeof(uint8_t));
+	for (i=0; i<mapbytes; i++) {
+		freemapdata[i] = tofreedata[i] = 0;
+	}
+
+	/* Mark off what's in the freemap but past the volume end. */
+	for (i=fsblocks; i < mapblocks*SFS_BITSPERBLOCK; i++) {
+		freemap_blockinuse(i, B_PASTEND, 0);
+	}
+
+	/* Mark the superblock block and the freemap blocks in use */
+	freemap_blockinuse(SFS_SUPER_BLOCK, B_SUPERBLOCK, 0);
+	for (i=0; i < mapblocks; i++) {
+		freemap_blockinuse(SFS_FREEMAP_START+i, B_FREEMAPBLOCK, i);
+	}
+}
+
+/*
+ * Return a string for a blockusage; used for printing errors.
+ */
+static
+const char *
+blockusagestr(blockusage_t how, uint32_t howdesc)
+{
+	static char rv[256];
+	switch (how) {
+	    case B_SUPERBLOCK:
+		return "superblock";
+	    case B_FREEMAPBLOCK:
+		snprintf(rv, sizeof(rv), "freemap block %lu",
+			 (unsigned long) howdesc);
+		break;
+	    case B_INODE:
+		snprintf(rv, sizeof(rv), "inode %lu",
+			 (unsigned long) howdesc);
+		break;
+	    case B_IBLOCK:
+		snprintf(rv, sizeof(rv), "indirect block of inode %lu",
+			 (unsigned long) howdesc);
+		break;
+	    case B_DIRDATA:
+		snprintf(rv, sizeof(rv), "directory data from inode %lu",
+			 (unsigned long) howdesc);
+		break;
+	    case B_DATA:
+		snprintf(rv, sizeof(rv), "file data from inode %lu",
+			 (unsigned long) howdesc);
+		break;
+	    case B_PASTEND:
+		return "past the end of the fs";
+	}
+	return rv;
+}
+
+/*
+ * Mark block BLOCK in use. HOW and HOWDESC describe how it was found
+ * to be in use, so we can print a useful message if it's wrong.
+ *
+ * FUTURE: this should not produce unrecoverable errors.
+ */
+void
+freemap_blockinuse(uint32_t block, blockusage_t how, uint32_t howdesc)
+{
+	unsigned index = block/8;
+	uint8_t mask = ((uint8_t)1)<<(block%8);
+
+	if (tofreedata[index] & mask) {
+		/* really using the block, don't free it */
+		tofreedata[index] &= ~mask;
+	}
+
+	if (freemapdata[index] & mask) {
+		warnx("Block %lu (used as %s) already in use! (NOT FIXED)",
+		      (unsigned long) block, blockusagestr(how, howdesc));
+		setbadness(EXIT_UNRECOV);
+	}
+
+	freemapdata[index] |= mask;
+
+	if (how != B_PASTEND) {
+		blocksinuse++;
+	}
+}
+
+/*
+ * Mark a block free. This is specifically for blocks that we are
+ * freeing, that might be marked allocated in the on-disk freemap. If
+ * the block has been found in use, assume the reference that's in use
+ * is valid. This can be caused by freeing a block, reallocating it
+ * somewhere else and then dying without erasing all of the original
+ * usage on disk; most such cases will just show the block in use
+ * twice, which is (not) handled above, but it's possible for the
+ * original usage to be something we are dropping, e.g. if a truncate
+ * (to a nonzero length > INOMAX_D) got partially completed.
+ */
+void
+freemap_blockfree(uint32_t block)
+{
+	unsigned index = block/8;
+	uint8_t mask = ((uint8_t)1)<<(block%8);
+
+	if (tofreedata[index] & mask) {
+		/* already marked to free once, ignore */
+		return;
+	}
+	if (freemapdata[index] & mask) {
+		/* block is used elsewhere, ignore */
+		return;
+	}
+	tofreedata[index] |= mask;
+}
+
+/*
+ * Count the number of bits set.
+ */
+static
+int
+countbits(uint8_t val)
+{
+	uint8_t x;
+	int ct=0;
+
+	for (x=1; x; x<<=1) {
+		if (val & x) ct++;
+	}
+	return ct;
+}
+
+/*
+ * Print a complaint about freemap bits being wrong.
+ *
+ * FREEMAPBLOCK is the block number within the freemap; BYTE is the
+ * byte offset within that block; VAL is the byte value; WHAT is a
+ * string indicating what happened.
+ */
+static
+void
+reportfreemap(uint32_t mapblock, uint32_t byte, uint8_t val, const char *what)
+{
+	uint8_t x, y;
+	uint32_t blocknum;
+
+	for (x=1, y=0; x; x<<=1, y++) {
+		if (val & x) {
+			blocknum = mapblock*SFS_BITSPERBLOCK +
+				byte*CHAR_BIT + y;
+			warnx("Block %lu erroneously shown %s in freemap",
+			      (unsigned long) blocknum, what);
+		}
+	}
+}
+
+/*
+ * Scan the freemap.
+ *
+ * This is called after (at the end of) pass 1, when we've recursively
+ * found all the reachable blocks and marked them.
+ */
+void
+freemap_check(void)
+{
+	uint8_t actual[SFS_BLOCKSIZE], *expected, *tofree, tmp;
+	uint32_t alloccount=0, freecount=0, i, j;
+	int bchanged;
+	uint32_t bitblocks;
+
+	bitblocks = sb_freemapblocks();
+
+	for (i=0; i<bitblocks; i++) {
+		sfs_readfreemapblock(i, actual);
+		expected = freemapdata + i*SFS_BLOCKSIZE;
+		tofree = tofreedata + i*SFS_BLOCKSIZE;
+		bchanged = 0;
+
+		for (j=0; j<SFS_BLOCKSIZE; j++) {
+			/* we shouldn't have blocks marked both ways */
+			assert((expected[j] & tofree[j])==0);
+
+			/* what's there is what should be there */
+			if (actual[j] == expected[j]) {
+				continue;
+			}
+
+			/* what's there is what should be there modulo frees */
+			if (actual[j] == (expected[j] | tofree[j])) {
+				actual[j] = expected[j];
+				bchanged = 1;
+				continue;
+			}
+
+			/* oops, it doesn't match... */
+
+			/* free the ones we're freeing (don't report these) */
+			actual[j] &= ~tofree[j];
+
+			/* are we short any? */
+			if ((actual[j] & expected[j]) != expected[j]) {
+				tmp = expected[j] & ~actual[j];
+				alloccount += countbits(tmp);
+				if (tmp != 0) {
+					reportfreemap(i, j, tmp, "free");
+				}
+			}
+
+			/* do we have any extra? */
+			if ((actual[j] & expected[j]) != actual[j]) {
+				tmp = actual[j] & ~expected[j];
+				freecount += countbits(tmp);
+				if (tmp != 0) {
+					reportfreemap(i, j, tmp, "allocated");
+				}
+			}
+
+			/* set it to what it should be */
+			actual[j] = expected[j];
+			bchanged = 1;
+		}
+
+		/* write the block back if necessary */
+		if (bchanged) {
+			sfs_writefreemapblock(i, actual);
+		}
+	}
+
+	if (alloccount > 0) {
+		warnx("%lu blocks erroneously shown free in freemap (fixed)",
+		      (unsigned long) alloccount);
+		setbadness(EXIT_RECOV);
+	}
+	if (freecount > 0) {
+		warnx("%lu blocks erroneously shown used in freemap (fixed)",
+		      (unsigned long) freecount);
+		setbadness(EXIT_RECOV);
+	}
+}
+
+/*
+ * Return the total number of blocks in use, which we count during
+ * pass 1.
+ */
+unsigned long
+freemap_blocksused(void)
+{
+	return blocksinuse;
+}
--- a/userland/sbin/sfsck/freemap.h
+++ b/userland/sbin/sfsck/freemap.h
@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef FREEMAP_H
+#define FREEMAP_H
+
+/*
+ * The freemap module accumulates information about the free block
+ * bitmap as other checks are made, and then uses that information
+ * to check and correct it.
+ */
+
+#include <stdint.h>
+
+typedef enum {
+	B_SUPERBLOCK,	/* Block that is the superblock */
+	B_FREEMAPBLOCK,	/* Block used by free-block bitmap */
+	B_INODE,	/* Block that is an inode */
+	B_IBLOCK,	/* Indirect (or doubly-indirect etc.) block */
+	B_DIRDATA,	/* Data block of a directory */
+	B_DATA,		/* Data block */
+	B_PASTEND,	/* Block off the end of the fs */
+} blockusage_t;
+
+/* Call this after loading the superblock but before doing any checks. */
+void freemap_setup(void);
+
+/* Call this to note that a block has been found in use. */
+void freemap_blockinuse(uint32_t block, blockusage_t how, uint32_t howdesc);
+
+/* Note that a block has been found where it should be dropped. */
+void freemap_blockfree(uint32_t block);
+
+/* Call this after all checks that call freemap_block{inuse,free}. */
+void freemap_check(void);
+
+/* Return the number of blocks in use. Valid after freemap_check(). */
+unsigned long freemap_blocksused(void);
+
+
+#endif /* FREEMAP_H */
--- a/userland/sbin/sfsck/ibmacros.h
+++ b/userland/sbin/sfsck/ibmacros.h
@@ -0,0 +1,159 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef IBMACROS_H
+#define IBMACROS_H
+
+/*
+ * Indirect block access macros
+ *
+ * These are macros for working with the direct and indirect block
+ * pointers in the inode. The scheme here supports a range of possible
+ * configurations, because sometimes adding large file support to SFS
+ * is part of an assignment; there is and should be no obligation to
+ * pick any particular layout, and we'd like sfsck to build and run
+ * seamlessly provided that the values declared in kern/sfs.h are
+ * correct.
+ *
+ * SFS_NDIRECT, SFS_NINDIRECT, SFS_NDINDIRECT, and SFS_NTINDIRECT
+ * should always be defined. If zero, no corresponding field is
+ * assumed to exist in the inode. If one, the field is assumed to
+ * be a single value and not an array. If greater than one, the
+ * field is assumed to be an array.
+ */
+
+#ifndef SFS_NDIRECT
+#error "SFS_NDIRECT not defined"
+#endif
+#ifndef SFS_NINDIRECT
+#error "SFS_NINDIRECT not defined"
+#endif
+#ifndef SFS_NDINDIRECT
+#error "SFS_NDINDIRECT not defined"
+#endif
+#ifndef SFS_NTINDIRECT
+#error "SFS_NTINDIRECT not defined"
+#endif
+
+/*
+ * For x in D, I, II, III (direct, indirect, 2x/3x indirect) we
+ * provide:
+ *
+ *    NUM_x	the number of blocks of this type
+ *    GET_x	retrieve the i'th block of this type
+ *    SET_x	lvalue for the i'th block of this type
+ *    RANGE_x	size of the block range mapped with one block of this type
+ *    INOMAX_x	maximum block number mapped by using this type in the inode
+ *
+ * It is important that the accessor macros (SET_x/GET_x) not refer to
+ * a nonexistent field of the inode in the case where there are zero
+ * blocks of that type, as that will lead to compile failure. Hence the
+ * lengthy definitions. So far I haven't thought any useful cpp hackery
+ * to make them more concise.
+ */
+
+/* numbers */
+
+#define NUM_D   		SFS_NDIRECT
+#define NUM_I			SFS_NINDIRECT
+#define NUM_II			SFS_NDINDIRECT
+#define NUM_III			SFS_NTINDIRECT
+
+/* blocks */
+
+#if NUM_D == 0
+#define GET_D(sfi, i)		GET0_x(sfi, sfi_direct, i)
+#define SET_D(sfi, i)		SET0_x(sfi, sfi_direct, i)
+#elif NUM_D == 1
+#define GET_D(sfi, i)		GET1_x(sfi, sfi_direct, i)
+#define SET_D(sfi, i)		SET1_x(sfi, sfi_direct, i)
+#else
+#define GET_D(sfi, i)		GETN_x(sfi, sfi_direct, i)
+#define SET_D(sfi, i)		SETN_x(sfi, sfi_direct, i)
+#endif
+
+#if NUM_I == 0
+#define GET_I(sfi, i)		GET0_x(sfi, sfi_indirect, i)
+#define SET_I(sfi, i)		SET0_x(sfi, sfi_indirect, i)
+#elif NUM_I == 1
+#define GET_I(sfi, i)		GET1_x(sfi, sfi_indirect, i)
+#define SET_I(sfi, i)		SET1_x(sfi, sfi_indirect, i)
+#else
+#define GET_I(sfi, i)		GETN_x(sfi, sfi_indirect, i)
+#define SET_I(sfi, i)		SETN_x(sfi, sfi_indirect, i)
+#endif
+
+#if NUM_II == 0
+#define GET_II(sfi, i)		GET0_x(sfi, sfi_dindirect, i)
+#define SET_II(sfi, i)		SET0_x(sfi, sfi_dindirect, i)
+#elif NUM_II == 1
+#define GET_II(sfi, i)		GET1_x(sfi, sfi_dindirect, i)
+#define SET_II(sfi, i)		SET1_x(sfi, sfi_dindirect, i)
+#else
+#define GET_II(sfi, i)		GETN_x(sfi, sfi_dindirect, i)
+#define SET_II(sfi, i)		SETN_x(sfi, sfi_dindirect, i)
+#endif
+
+#if NUM_III == 0
+#define GET_III(sfi, i)		GET0_x(sfi, sfi_tindirect, i)
+#define SET_III(sfi, i)		SET0_x(sfi, sfi_tindirect, i)
+#elif NUM_III == 1
+#define GET_III(sfi, i)		GET1_x(sfi, sfi_tindirect, i)
+#define SET_III(sfi, i)		SET1_x(sfi, sfi_tindirect, i)
+#else
+#define GET_III(sfi, i)		GETN_x(sfi, sfi_tindirect, i)
+#define SET_III(sfi, i)		SETN_x(sfi, sfi_tindirect, i)
+#endif
+
+/* the generic forms of the block macros */
+
+#define GET0_x(sfi, field, i)	((void)(i), (void)(sfi), 0)
+#define GET1_x(sfi, field, i)	((void)(i), (sfi)->field)
+#define GETN_x(sfi, field, i)	((sfi)->field[(i)])
+
+#define SET0_x(sfi, field, i)	(*((void)(i), (void)(sfi), (uint32_t *)NULL))
+#define SET1_x(sfi, field, i)	(*((void)(i), &(sfi)->field))
+#define SETN_x(sfi, field, i)	((sfi)->field[(i)])
+
+/* region sizes */
+
+#define RANGE_D		1
+#define RANGE_I		(RANGE_D * SFS_DBPERIDB)
+#define RANGE_II	(RANGE_I * SFS_DBPERIDB)
+#define RANGE_III	(RANGE_II * SFS_DBPERIDB)
+
+/* max blocks */
+
+#define INOMAX_D 	NUM_D
+#define INOMAX_I 	(INOMAX_D + SFS_DBPERIDB * NUM_I)
+#define INOMAX_II	(INOMAX_I + SFS_DBPERIDB * NUM_II)
+#define INOMAX_III	(INOMAX_II + SFS_DBPERIDB * NUM_III)
+
+
+#endif /* IBMACROS_H */
--- a/userland/sbin/sfsck/inode.c
+++ b/userland/sbin/sfsck/inode.c
@@ -0,0 +1,266 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <err.h>
+
+#include "compat.h"
+#include <kern/sfs.h>
+
+#include "utils.h"
+#include "sfs.h"
+#include "freemap.h"
+#include "inode.h"
+#include "main.h"
+
+/*
+ * Stuff we remember about inodes.
+ * FUTURE: should count the number of blocks allocated to this inode
+ */
+struct inodeinfo {
+	uint32_t ino;
+	uint32_t linkcount;	/* files only */
+	int visited;		/* dirs only */
+	int type;
+};
+
+/* Table of inodes found. */
+static struct inodeinfo *inodes = NULL;
+static unsigned ninodes = 0, maxinodes = 0;
+
+/* Whether the table is sorted and can be looked up with binary search. */
+static int inodes_sorted = 0;
+
+////////////////////////////////////////////////////////////
+// inode table ops
+
+/*
+ * Add an entry to the inode table, realloc'ing it if needed.
+ */
+static
+void
+inode_addtable(uint32_t ino, int type)
+{
+	unsigned newmax;
+
+	assert(ninodes <= maxinodes);
+	if (ninodes == maxinodes) {
+		newmax = maxinodes ? maxinodes * 2 : 4;
+		inodes = dorealloc(inodes, maxinodes * sizeof(inodes[0]),
+				   newmax * sizeof(inodes[0]));
+		maxinodes = newmax;
+	}
+	inodes[ninodes].ino = ino;
+	inodes[ninodes].linkcount = 0;
+	inodes[ninodes].visited = 0;
+	inodes[ninodes].type = type;
+	ninodes++;
+	inodes_sorted = 0;
+}
+
+/*
+ * Compare function for inodes.
+ */
+static
+int
+inode_compare(const void *av, const void *bv)
+{
+	const struct inodeinfo *a = av;
+	const struct inodeinfo *b = bv;
+
+	if (a->ino < b->ino) {
+		return -1;
+	}
+	if (a->ino > b->ino) {
+		return 1;
+	}
+	/*
+	 * There should be no duplicates in the table! But C99 makes
+	 * no guarantees about whether the implementation of qsort can
+	 * ask us to compare an element to itself. Assert that this is
+	 * what happened.
+	 */
+	assert(av == bv);
+	return 0;
+}
+
+/*
+ * After pass1, we sort the inode table for faster access.
+ */
+void
+inode_sorttable(void)
+{
+	qsort(inodes, ninodes, sizeof(inodes[0]), inode_compare);
+	inodes_sorted = 1;
+}
+
+/*
+ * Find an inode by binary search.
+ *
+ * This will error out if asked for an inode not in the table; that's
+ * not supposed to happen. (This might need to change; if we improve
+ * the handling of crosslinked directories as suggested in comments in
+ * pass2.c, we'll need to be able to ask if an inode number is valid
+ * and names a directory.)
+ */
+static
+struct inodeinfo *
+inode_find(uint32_t ino)
+{
+	unsigned min, max, i;
+
+	assert(inodes_sorted);
+	assert(ninodes > 0);
+
+	min = 0;
+	max = ninodes;
+	while (1) {
+		assert(min <= max);
+		if (min == max) {
+			errx(EXIT_UNRECOV, "FATAL: inode %u wasn't found in my inode table", ino);
+		}
+		i = min + (max - min)/2;
+		if (inodes[i].ino < ino) {
+			min = i + 1;
+		}
+		else if (inodes[i].ino > ino) {
+			max = i;
+		}
+		else {
+			assert(inodes[i].ino == ino);
+			return &inodes[i];
+		}
+	}
+	/* NOTREACHED */
+}
+
+////////////////////////////////////////////////////////////
+// inode ops
+
+/*
+ * Add an inode; returns 1 if we've already seen it.
+ *
+ * Uses linear search because we only sort the table for faster access
+ * after all inodes have been added. In the FUTURE this could be
+ * changed to a better data structure.
+ */
+int
+inode_add(uint32_t ino, int type)
+{
+	unsigned i;
+
+	for (i=0; i<ninodes; i++) {
+		if (inodes[i].ino==ino) {
+			assert(inodes[i].linkcount == 0);
+			assert(inodes[i].type == type);
+			return 1;
+		}
+	}
+
+	inode_addtable(ino, type);
+
+	return 0;
+}
+
+/*
+ * Mark an inode (directories only, because that's all the caller
+ * does) visited. Returns nonzero if already visited.
+ *
+ * Note that there is no way to clear the visited flag for now because
+ * it's only used once (by pass2).
+ */
+int
+inode_visitdir(uint32_t ino)
+{
+	struct inodeinfo *inf;
+
+	inf = inode_find(ino);
+	assert(inf->type == SFS_TYPE_DIR);
+	assert(inf->linkcount == 0);
+	if (inf->visited) {
+		return 1;
+	}
+	inf->visited = 1;
+	return 0;
+}
+
+/*
+ * Count a link. Only for regular files because that's what the caller
+ * does. (And that, in turn, is because the link count of a directory
+ * is a local property.)
+ */
+void
+inode_addlink(uint32_t ino)
+{
+	struct inodeinfo *inf;
+
+	inf = inode_find(ino);
+	assert(inf->type == SFS_TYPE_FILE);
+	assert(inf->visited == 0);
+	inf->linkcount++;
+}
+
+/*
+ * Correct link counts. This is effectively pass3. (FUTURE: change the
+ * name accordingly.)
+ */
+void
+inode_adjust_filelinks(void)
+{
+	struct sfs_dinode sfi;
+	unsigned i;
+
+	for (i=0; i<ninodes; i++) {
+		if (inodes[i].type == SFS_TYPE_DIR) {
+			/* directory */
+			continue;
+		}
+		assert(inodes[i].type == SFS_TYPE_FILE);
+
+		/* because we've seen it, there must be at least one link */
+		assert(inodes[i].linkcount > 0);
+
+		sfs_readinode(inodes[i].ino, &sfi);
+		assert(sfi.sfi_type == SFS_TYPE_FILE);
+
+		if (sfi.sfi_linkcount != inodes[i].linkcount) {
+			warnx("File %lu link count %lu should be %lu (fixed)",
+			      (unsigned long) inodes[i].ino,
+			      (unsigned long) sfi.sfi_linkcount,
+			      (unsigned long) inodes[i].linkcount);
+			sfi.sfi_linkcount = inodes[i].linkcount;
+			setbadness(EXIT_RECOV);
+			sfs_writeinode(inodes[i].ino, &sfi);
+		}
+	}
+}
+
--- a/userland/sbin/sfsck/inode.h
+++ b/userland/sbin/sfsck/inode.h
@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef INODE_H
+#define INODE_H
+
+/*
+ * The inode module accumulates non-local information about files and
+ * directories as other checks are made, and then updates inodes
+ * accordingly after the other checks are done.
+ */
+
+/* Add an inode. Returns 1 if we've seen this inode before. */
+int inode_add(uint32_t ino, int type);
+
+/* Sort the inode table for faster lookup once all inode_add() done. */
+void inode_sorttable(void);
+
+/*
+ * Remember that we've seen a particular directory. Returns nonzero if
+ * we've seen this directory before, which means the directory is
+ * crosslinked. Requires inode_sorttable() first.
+ */
+int inode_visitdir(uint32_t ino);
+
+/*
+ * Count a link to a regular file. (Not called for directories.)
+ * Requires inode_sorttable() first.
+ */
+void inode_addlink(uint32_t ino);
+
+/*
+ * Correct the link counts of regular files, once all inode_addlink()
+ * done.
+ */
+void inode_adjust_filelinks(void);
+
+
+#endif /* INODE_H */
--- a/userland/sbin/sfsck/main.c
+++ b/userland/sbin/sfsck/main.c
@@ -0,0 +1,118 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <assert.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <err.h>
+
+#include "compat.h"
+
+#include "disk.h"
+#include "sfs.h"
+#include "sb.h"
+#include "freemap.h"
+#include "inode.h"
+#include "passes.h"
+#include "main.h"
+
+static int badness=0;
+
+/*
+ * Update the badness state. (codes are in main.h)
+ *
+ * The badness state only gets worse, and is ultimately the process
+ * exit code.
+ */
+void
+setbadness(int code)
+{
+	if (badness < code) {
+		badness = code;
+	}
+}
+
+/*
+ * Main.
+ */
+int
+main(int argc, char **argv)
+{
+#ifdef HOST
+	hostcompat_init(argc, argv);
+#endif
+
+	/* FUTURE: add -n option */
+	if (argc!=2) {
+		errx(EXIT_USAGE, "Usage: sfsck device/diskfile");
+	}
+
+	opendisk(argv[1]);
+
+	sfs_setup();
+	sb_load();
+	sb_check();
+	freemap_setup();
+
+	printf("Phase 1 -- check blocks and sizes\n");
+	pass1();
+	freemap_check();
+
+	printf("Phase 2 -- check directory tree\n");
+	inode_sorttable();
+	pass2();
+
+	printf("Phase 3 -- check reference counts\n");
+	inode_adjust_filelinks();
+
+	closedisk();
+
+	warnx("%lu blocks used (of %lu); %lu directories; %lu files",
+	      freemap_blocksused(), (unsigned long)sb_totalblocks(),
+	      pass1_founddirs(), pass1_foundfiles());
+
+	switch (badness) {
+	    case EXIT_USAGE:
+	    case EXIT_FATAL:
+	    default:
+		/* not supposed to happen here */
+		assert(0);
+		break;
+	    case EXIT_UNRECOV:
+		warnx("WARNING - unrecoverable errors. Maybe try again?");
+		break;
+	    case EXIT_RECOV:
+		warnx("Caution - filesystem modified. Run again for luck.");
+		break;
+	    case EXIT_CLEAN:
+		break;
+	}
+
+	return badness;
+}
--- a/userland/sbin/sfsck/main.h
+++ b/userland/sbin/sfsck/main.h
@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef MAIN_H
+#define MAIN_H
+
+/*
+ * Levels of problems that we can encounter.
+ *
+ * setbadness() records the maximum level seen so far; this is
+ * the ultimate exit code of sfsck.
+ */
+
+#define EXIT_USAGE    4
+#define EXIT_FATAL    3
+#define EXIT_UNRECOV  2
+#define EXIT_RECOV    1
+#define EXIT_CLEAN    0
+
+void setbadness(int code);
+
+#endif /* MAIN_H */
--- a/userland/sbin/sfsck/pass1.c
+++ b/userland/sbin/sfsck/pass1.c
@@ -0,0 +1,496 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <err.h>
+
+#include "compat.h"
+#include <kern/sfs.h>
+
+#include "disk.h"
+#include "utils.h"
+#include "ibmacros.h"
+#include "sfs.h"
+#include "sb.h"
+#include "freemap.h"
+#include "inode.h"
+#include "passes.h"
+#include "main.h"
+
+static unsigned long count_dirs=0, count_files=0;
+
+/*
+ * State for checking indirect blocks.
+ */
+struct ibstate {
+	uint32_t ino;		/* inode we're doing (constant) */
+	uint32_t curfileblock;	/* current block offset in the file */
+	uint32_t fileblocks;	/* file size in blocks (constant) */
+	uint32_t volblocks;	/* volume size in blocks (constant) */
+	unsigned pasteofcount;	/* number of blocks found past eof */
+	blockusage_t usagetype;	/* how to call freemap_blockinuse() */
+};
+
+/*
+ * Traverse an indirect block, recording blocks that are in use,
+ * dropping any entries that are past EOF, and clearing any entries
+ * that point outside the volume.
+ *
+ * XXX: this should be extended to be able to recover from crosslinked
+ * blocks. Currently it just complains in freemap.c and sets
+ * EXIT_UNRECOV.
+ *
+ * The traversal is recursive; the state is maintained in IBS (as
+ * described above). IENTRY is a pointer to the entry in the parent
+ * indirect block (or the inode) that names the block we're currently
+ * scanning. IECHANGEDP should be set to 1 if *IENTRY is changed.
+ * INDIRECTION is the indirection level of this block (1, 2, or 3).
+ */
+static
+void
+check_indirect_block(struct ibstate *ibs, uint32_t *ientry, int *iechangedp,
+		     int indirection)
+{
+	uint32_t entries[SFS_DBPERIDB];
+	uint32_t i, ct;
+	uint32_t coveredblocks;
+	int localchanged = 0;
+	int j;
+
+	if (*ientry > 0 && *ientry < ibs->volblocks) {
+		sfs_readindirect(*ientry, entries);
+		freemap_blockinuse(*ientry, B_IBLOCK, ibs->ino);
+	}
+	else {
+		if (*ientry >= ibs->volblocks) {
+			setbadness(EXIT_RECOV);
+			warnx("Inode %lu: indirect block pointer (level %d) "
+			      "for block %lu outside of volume: %lu "
+			      "(cleared)\n",
+			      (unsigned long)ibs->ino, indirection,
+			      (unsigned long)ibs->curfileblock,
+			      (unsigned long)*ientry);
+			*ientry = 0;
+			*iechangedp = 1;
+		}
+		coveredblocks = 1;
+		for (j=0; j<indirection; j++) {
+			coveredblocks *= SFS_DBPERIDB;
+		}
+		ibs->curfileblock += coveredblocks;
+		return;
+	}
+
+	if (indirection > 1) {
+		for (i=0; i<SFS_DBPERIDB; i++) {
+			check_indirect_block(ibs, &entries[i], &localchanged,
+					     indirection-1);
+		}
+	}
+	else {
+		assert(indirection==1);
+
+		for (i=0; i<SFS_DBPERIDB; i++) {
+			if (entries[i] >= ibs->volblocks) {
+				setbadness(EXIT_RECOV);
+				warnx("Inode %lu: direct block pointer for "
+				      "block %lu outside of volume: %lu "
+				      "(cleared)\n",
+				      (unsigned long)ibs->ino,
+				      (unsigned long)ibs->curfileblock,
+				      (unsigned long)entries[i]);
+				entries[i] = 0;
+				localchanged = 1;
+			}
+			else if (entries[i] != 0) {
+				if (ibs->curfileblock < ibs->fileblocks) {
+					freemap_blockinuse(entries[i],
+							  ibs->usagetype,
+							  ibs->ino);
+				}
+				else {
+					setbadness(EXIT_RECOV);
+					ibs->pasteofcount++;
+					freemap_blockfree(entries[i]);
+					entries[i] = 0;
+					localchanged = 1;
+				}
+			}
+			ibs->curfileblock++;
+		}
+	}
+
+	ct=0;
+	for (i=ct=0; i<SFS_DBPERIDB; i++) {
+		if (entries[i]!=0) ct++;
+	}
+	if (ct==0) {
+		if (*ientry != 0) {
+			setbadness(EXIT_RECOV);
+			/* this is not necessarily correct */
+			/*ibs->pasteofcount++;*/
+			*iechangedp = 1;
+			freemap_blockfree(*ientry);
+			*ientry = 0;
+		}
+	}
+	else {
+		assert(*ientry != 0);
+		if (localchanged) {
+			sfs_writeindirect(*ientry, entries);
+		}
+	}
+}
+
+/*
+ * Check the blocks belonging to inode INO, whose inode has already
+ * been loaded into SFI. ISDIR is a shortcut telling us if the inode
+ * is a directory.
+ *
+ * Returns nonzero if SFI has been modified and needs to be written
+ * back.
+ */
+static
+int
+check_inode_blocks(uint32_t ino, struct sfs_dinode *sfi, int isdir)
+{
+	struct ibstate ibs;
+	uint32_t size, datablock;
+	int changed;
+	int i;
+
+	size = SFS_ROUNDUP(sfi->sfi_size, SFS_BLOCKSIZE);
+
+	ibs.ino = ino;
+	/*ibs.curfileblock = 0;*/
+	ibs.fileblocks = size/SFS_BLOCKSIZE;
+	ibs.volblocks = sb_totalblocks();
+	ibs.pasteofcount = 0;
+	ibs.usagetype = isdir ? B_DIRDATA : B_DATA;
+
+	changed = 0;
+
+	for (ibs.curfileblock=0; ibs.curfileblock<NUM_D; ibs.curfileblock++) {
+		datablock = GET_D(sfi, ibs.curfileblock);
+		if (datablock >= ibs.volblocks) {
+			setbadness(EXIT_RECOV);
+			warnx("Inode %lu: direct block pointer for "
+			      "block %lu outside of volume: %lu "
+			      "(cleared)\n",
+			      (unsigned long)ibs.ino,
+			      (unsigned long)ibs.curfileblock,
+			      (unsigned long)datablock);
+			SET_D(sfi, ibs.curfileblock) = 0;
+			changed = 1;
+		}
+		else if (datablock > 0) {
+			if (ibs.curfileblock < ibs.fileblocks) {
+				freemap_blockinuse(datablock, ibs.usagetype,
+						   ibs.ino);
+			}
+			else {
+				setbadness(EXIT_RECOV);
+				ibs.pasteofcount++;
+				changed = 1;
+				freemap_blockfree(datablock);
+				SET_D(sfi, ibs.curfileblock) = 0;
+			}
+		}
+	}
+
+	for (i=0; i<NUM_I; i++) {
+		check_indirect_block(&ibs, &SET_I(sfi, i), &changed, 1);
+	}
+	for (i=0; i<NUM_II; i++) {
+		check_indirect_block(&ibs, &SET_II(sfi, i), &changed, 2);
+	}
+	for (i=0; i<NUM_III; i++) {
+		check_indirect_block(&ibs, &SET_III(sfi, i), &changed, 3);
+	}
+
+	if (ibs.pasteofcount > 0) {
+		warnx("Inode %lu: %u blocks after EOF (freed)",
+		     (unsigned long) ibs.ino, ibs.pasteofcount);
+		setbadness(EXIT_RECOV);
+	}
+
+	return changed;
+}
+
+/*
+ * Do the pass1 inode-level checks on inode INO, which has already
+ * been loaded into SFI. Note that sfi_type has already been
+ * validated.
+ *
+ * Returns nonzero if SFI has been modified and needs to be written
+ * back.
+ */
+static
+int
+pass1_inode(uint32_t ino, struct sfs_dinode *sfi, int alreadychanged)
+{
+	int changed = alreadychanged;
+	int isdir = sfi->sfi_type == SFS_TYPE_DIR;
+
+	if (inode_add(ino, sfi->sfi_type)) {
+		/* Already been here. */
+		assert(changed == 0);
+		return 1;
+	}
+
+	freemap_blockinuse(ino, B_INODE, ino);
+
+	if (checkzeroed(sfi->sfi_waste, sizeof(sfi->sfi_waste))) {
+		warnx("Inode %lu: sfi_waste section not zeroed (fixed)",
+		      (unsigned long) ino);
+		setbadness(EXIT_RECOV);
+		changed = 1;
+	}
+
+	if (check_inode_blocks(ino, sfi, isdir)) {
+		changed = 1;
+	}
+
+	if (changed) {
+		sfs_writeinode(ino, sfi);
+	}
+	return 0;
+}
+
+/*
+ * Check the directory entry in SFD. INDEX is its offset, and PATH is
+ * its name; these are used for printing messages.
+ */
+static
+int
+pass1_direntry(const char *path, uint32_t index, struct sfs_direntry *sfd)
+{
+	int dchanged = 0;
+	uint32_t nblocks;
+
+	nblocks = sb_totalblocks();
+
+	if (sfd->sfd_ino == SFS_NOINO) {
+		if (sfd->sfd_name[0] != 0) {
+			setbadness(EXIT_RECOV);
+			warnx("Directory %s entry %lu has name but no file",
+			      path, (unsigned long) index);
+			sfd->sfd_name[0] = 0;
+			dchanged = 1;
+		}
+	}
+	else if (sfd->sfd_ino >= nblocks) {
+		setbadness(EXIT_RECOV);
+		warnx("Directory %s entry %lu has out of range "
+		      "inode (cleared)",
+		      path, (unsigned long) index);
+		sfd->sfd_ino = SFS_NOINO;
+		sfd->sfd_name[0] = 0;
+		dchanged = 1;
+	}
+	else {
+		if (sfd->sfd_name[0] == 0) {
+			/* XXX: what happens if FSCK.n.m already exists? */
+			snprintf(sfd->sfd_name, sizeof(sfd->sfd_name),
+				 "FSCK.%lu.%lu",
+				 (unsigned long) sfd->sfd_ino,
+				 (unsigned long) uniqueid());
+			setbadness(EXIT_RECOV);
+			warnx("Directory %s entry %lu has file but "
+			      "no name (fixed: %s)",
+			      path, (unsigned long) index,
+			      sfd->sfd_name);
+			dchanged = 1;
+		}
+		if (checknullstring(sfd->sfd_name, sizeof(sfd->sfd_name))) {
+			setbadness(EXIT_RECOV);
+			warnx("Directory %s entry %lu not "
+			      "null-terminated (fixed)",
+			      path, (unsigned long) index);
+			dchanged = 1;
+		}
+		if (checkbadstring(sfd->sfd_name)) {
+			setbadness(EXIT_RECOV);
+			warnx("Directory %s entry %lu contains invalid "
+			      "characters (fixed)",
+			      path, (unsigned long) index);
+			dchanged = 1;
+		}
+	}
+	return dchanged;
+}
+
+/*
+ * Check a directory. INO is the inode number; PATHSOFAR is the path
+ * to this directory. This traverses the volume directory tree
+ * recursively.
+ */
+static
+void
+pass1_dir(uint32_t ino, const char *pathsofar)
+{
+	struct sfs_dinode sfi;
+	struct sfs_direntry *direntries;
+	uint32_t ndirentries, i;
+	int ichanged=0, dchanged=0;
+
+	sfs_readinode(ino, &sfi);
+
+	if (sfi.sfi_size % sizeof(struct sfs_direntry) != 0) {
+		setbadness(EXIT_RECOV);
+		warnx("Directory %s has illegal size %lu (fixed)",
+		      pathsofar, (unsigned long) sfi.sfi_size);
+		sfi.sfi_size = SFS_ROUNDUP(sfi.sfi_size,
+					   sizeof(struct sfs_direntry));
+		ichanged = 1;
+	}
+	count_dirs++;
+
+	if (pass1_inode(ino, &sfi, ichanged)) {
+		/* been here before; crosslinked dir, sort it out in pass 2 */
+		return;
+	}
+
+	ndirentries = sfi.sfi_size/sizeof(struct sfs_direntry);
+	direntries = domalloc(sfi.sfi_size);
+
+	sfs_readdir(&sfi, direntries, ndirentries);
+
+	for (i=0; i<ndirentries; i++) {
+		if (pass1_direntry(pathsofar, i, &direntries[i])) {
+			dchanged = 1;
+		}
+	}
+
+	for (i=0; i<ndirentries; i++) {
+		if (direntries[i].sfd_ino == SFS_NOINO) {
+			/* nothing */
+		}
+		else if (!strcmp(direntries[i].sfd_name, ".")) {
+			/* nothing */
+		}
+		else if (!strcmp(direntries[i].sfd_name, "..")) {
+			/* nothing */
+		}
+		else {
+			char path[strlen(pathsofar)+SFS_NAMELEN+1];
+			struct sfs_dinode subsfi;
+			uint32_t subino;
+
+			subino = direntries[i].sfd_ino;
+			sfs_readinode(subino, &subsfi);
+			snprintf(path, sizeof(path), "%s/%s",
+				 pathsofar, direntries[i].sfd_name);
+
+			switch (subsfi.sfi_type) {
+			    case SFS_TYPE_FILE:
+				if (pass1_inode(subino, &subsfi, 0)) {
+					/* been here before */
+					break;
+				}
+				count_files++;
+				break;
+			    case SFS_TYPE_DIR:
+				pass1_dir(subino, path);
+				break;
+			    default:
+				setbadness(EXIT_RECOV);
+				warnx("Object %s: Invalid inode type %u "
+				      "(removed)", path, subsfi.sfi_type);
+				direntries[i].sfd_ino = SFS_NOINO;
+				direntries[i].sfd_name[0] = 0;
+				dchanged = 1;
+				break;
+			}
+		}
+	}
+
+	if (dchanged) {
+		sfs_writedir(&sfi, direntries, ndirentries);
+	}
+
+	free(direntries);
+}
+
+/*
+ * Check the root directory, and implicitly everything under it.
+ */
+static
+void
+pass1_rootdir(void)
+{
+	struct sfs_dinode sfi;
+	char path[SFS_VOLNAME_SIZE + 2];
+
+	sfs_readinode(SFS_ROOTDIR_INO, &sfi);
+
+	switch (sfi.sfi_type) {
+	    case SFS_TYPE_DIR:
+		break;
+	    case SFS_TYPE_FILE:
+		warnx("Root directory inode is a regular file (fixed)");
+		goto fix;
+	    default:
+		warnx("Root directory inode has invalid type %lu (fixed)",
+		      (unsigned long) sfi.sfi_type);
+	    fix:
+		setbadness(EXIT_RECOV);
+		sfi.sfi_type = SFS_TYPE_DIR;
+		sfs_writeinode(SFS_ROOTDIR_INO, &sfi);
+		break;
+	}
+
+	snprintf(path, sizeof(path), "%s:", sb_volname());
+	pass1_dir(SFS_ROOTDIR_INO, path);
+}
+
+////////////////////////////////////////////////////////////
+// public interface
+
+void
+pass1(void)
+{
+	pass1_rootdir();
+}
+
+unsigned long
+pass1_founddirs(void)
+{
+	return count_dirs;
+}
+
+unsigned long
+pass1_foundfiles(void)
+{
+	return count_files;
+}
--- a/userland/sbin/sfsck/pass2.c
+++ b/userland/sbin/sfsck/pass2.c
@@ -0,0 +1,325 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <err.h>
+
+#include "compat.h"
+#include <kern/sfs.h>
+
+#include "disk.h"
+#include "utils.h"
+#include "ibmacros.h"
+#include "sfs.h"
+#include "sb.h"
+#include "freemap.h"
+#include "inode.h"
+#include "passes.h"
+#include "main.h"
+
+/*
+ * Process a directory. INO is the inode number; PARENTINO is the
+ * parent's inode number; PATHSOFAR is the path to this directory.
+ *
+ * Recursively checks its subdirs.
+ *
+ * In the FUTURE we might want to improve the handling of crosslinked
+ * directories so it picks the parent that the .. entry points to,
+ * instead of the first entry we recursively find. Beware of course
+ * that the .. entry might not point to anywhere valid at all...
+ */
+static
+int
+pass2_dir(uint32_t ino, uint32_t parentino, const char *pathsofar)
+{
+	struct sfs_dinode sfi;
+	struct sfs_direntry *direntries;
+	int *sortvector;
+	uint32_t dirsize, ndirentries, maxdirentries, subdircount, i;
+	int ichanged=0, dchanged=0, dotseen=0, dotdotseen=0;
+
+	if (inode_visitdir(ino)) {
+		/* crosslinked dir; tell parent to remove the entry */
+		return 1;
+	}
+
+	/* Load the inode. */
+	sfs_readinode(ino, &sfi);
+
+	/*
+	 * Load the directory. If there is any leftover room in the
+	 * last block, allocate space for it in case we want to insert
+	 * entries.
+	 */
+
+	ndirentries = sfi.sfi_size/sizeof(struct sfs_direntry);
+	maxdirentries = SFS_ROUNDUP(ndirentries,
+				    SFS_BLOCKSIZE/sizeof(struct sfs_direntry));
+	dirsize = maxdirentries * sizeof(struct sfs_direntry);
+	direntries = domalloc(dirsize);
+
+	sortvector = domalloc(ndirentries * sizeof(int));
+
+	sfs_readdir(&sfi, direntries, ndirentries);
+	for (i=ndirentries; i<maxdirentries; i++) {
+		direntries[i].sfd_ino = SFS_NOINO;
+		bzero(direntries[i].sfd_name, sizeof(direntries[i].sfd_name));
+	}
+
+	/*
+	 * Sort by name and check for duplicate names.
+	 */
+
+	sfsdir_sort(direntries, ndirentries, sortvector);
+
+	/* don't use ndirentries-1 here, in case ndirentries == 0 */
+	for (i=0; i+1<ndirentries; i++) {
+		struct sfs_direntry *d1 = &direntries[sortvector[i]];
+		struct sfs_direntry *d2 = &direntries[sortvector[i+1]];
+		assert(d1 != d2);
+
+		if (d1->sfd_ino == SFS_NOINO || d2->sfd_ino == SFS_NOINO) {
+			/* sfsdir_sort puts these last */
+			continue;
+		}
+
+		if (!strcmp(d1->sfd_name, d2->sfd_name)) {
+			if (d1->sfd_ino == d2->sfd_ino) {
+				setbadness(EXIT_RECOV);
+				warnx("Directory %s: Duplicate entries for "
+				      "%s (merged)",
+				      pathsofar, d1->sfd_name);
+				d1->sfd_ino = SFS_NOINO;
+				d1->sfd_name[0] = 0;
+			}
+			else {
+				/* XXX: what if FSCK.n.m already exists? */
+				snprintf(d1->sfd_name, sizeof(d1->sfd_name),
+					 "FSCK.%lu.%lu",
+					 (unsigned long) d1->sfd_ino,
+					 (unsigned long) uniqueid());
+				setbadness(EXIT_RECOV);
+				warnx("Directory %s: Duplicate names %s "
+				      "(one renamed: %s)",
+				      pathsofar, d2->sfd_name, d1->sfd_name);
+			}
+			dchanged = 1;
+		}
+	}
+
+	/*
+	 * Look for the . and .. entries.
+	 */
+
+	for (i=0; i<ndirentries; i++) {
+		if (!strcmp(direntries[i].sfd_name, ".")) {
+			if (direntries[i].sfd_ino != ino) {
+				setbadness(EXIT_RECOV);
+				warnx("Directory %s: Incorrect `.' entry "
+				      "(fixed)", pathsofar);
+				direntries[i].sfd_ino = ino;
+				dchanged = 1;
+			}
+			/* duplicates are checked above -> only one . here */
+			assert(dotseen==0);
+			dotseen = 1;
+		}
+		else if (!strcmp(direntries[i].sfd_name, "..")) {
+			if (direntries[i].sfd_ino != parentino) {
+				setbadness(EXIT_RECOV);
+				warnx("Directory %s: Incorrect `..' entry "
+				      "(fixed)", pathsofar);
+				direntries[i].sfd_ino = parentino;
+				dchanged = 1;
+			}
+			/* duplicates are checked above -> only one .. here */
+			assert(dotdotseen==0);
+			dotdotseen = 1;
+		}
+	}
+
+	/*
+	 * If no . entry, try to insert one.
+	 */
+
+	if (!dotseen) {
+		if (sfsdir_tryadd(direntries, ndirentries, ".", ino)==0) {
+			setbadness(EXIT_RECOV);
+			warnx("Directory %s: No `.' entry (added)",
+			      pathsofar);
+			dchanged = 1;
+		}
+		else if (sfsdir_tryadd(direntries, maxdirentries, ".",
+				       ino)==0) {
+			setbadness(EXIT_RECOV);
+			warnx("Directory %s: No `.' entry (added)",
+			      pathsofar);
+			ndirentries++;
+			dchanged = 1;
+			sfi.sfi_size += sizeof(struct sfs_direntry);
+			ichanged = 1;
+		}
+		else {
+			setbadness(EXIT_UNRECOV);
+			warnx("Directory %s: No `.' entry (NOT FIXED)",
+			      pathsofar);
+		}
+	}
+
+	/*
+	 * If no .. entry, try to insert one.
+	 */
+
+	if (!dotdotseen) {
+		if (sfsdir_tryadd(direntries, ndirentries, "..",
+				  parentino)==0) {
+			setbadness(EXIT_RECOV);
+			warnx("Directory %s: No `..' entry (added)",
+			      pathsofar);
+			dchanged = 1;
+		}
+		else if (sfsdir_tryadd(direntries, maxdirentries, "..",
+				    parentino)==0) {
+			setbadness(EXIT_RECOV);
+			warnx("Directory %s: No `..' entry (added)",
+			      pathsofar);
+			ndirentries++;
+			dchanged = 1;
+			sfi.sfi_size += sizeof(struct sfs_direntry);
+			ichanged = 1;
+		}
+		else {
+			setbadness(EXIT_UNRECOV);
+			warnx("Directory %s: No `..' entry (NOT FIXED)",
+			      pathsofar);
+		}
+	}
+
+	/*
+	 * Now load each inode in the directory.
+	 *
+	 * For regular files, count the number of links we see; for
+	 * directories, recurse. Count the number of subdirs seen
+	 * so we can correct our own link count if necessary.
+	 */
+
+	subdircount=0;
+	for (i=0; i<ndirentries; i++) {
+		if (direntries[i].sfd_ino == SFS_NOINO) {
+			/* nothing */
+		}
+		else if (!strcmp(direntries[i].sfd_name, ".")) {
+			/* nothing */
+		}
+		else if (!strcmp(direntries[i].sfd_name, "..")) {
+			/* nothing */
+		}
+		else {
+			char path[strlen(pathsofar)+SFS_NAMELEN+1];
+			struct sfs_dinode subsfi;
+
+			sfs_readinode(direntries[i].sfd_ino, &subsfi);
+			snprintf(path, sizeof(path), "%s/%s",
+				 pathsofar, direntries[i].sfd_name);
+
+			switch (subsfi.sfi_type) {
+			    case SFS_TYPE_FILE:
+				inode_addlink(direntries[i].sfd_ino);
+				break;
+			    case SFS_TYPE_DIR:
+				if (pass2_dir(direntries[i].sfd_ino,
+					      ino,
+					      path)) {
+					setbadness(EXIT_RECOV);
+					warnx("Directory %s: Crosslink to "
+					      "other directory (removed)",
+					      path);
+					direntries[i].sfd_ino = SFS_NOINO;
+					direntries[i].sfd_name[0] = 0;
+					dchanged = 1;
+				}
+				else {
+					subdircount++;
+				}
+				break;
+			    default:
+				setbadness(EXIT_RECOV);
+				warnx("Object %s: Invalid inode type %u "
+				      "(removed)", path, subsfi.sfi_type);
+				direntries[i].sfd_ino = SFS_NOINO;
+				direntries[i].sfd_name[0] = 0;
+				dchanged = 1;
+				break;
+			}
+		}
+	}
+
+	/*
+	 * Fix up the link count if needed.
+	 */
+
+	if (sfi.sfi_linkcount != subdircount+2) {
+		setbadness(EXIT_RECOV);
+		warnx("Directory %s: Link count %lu should be %lu (fixed)",
+		      pathsofar, (unsigned long) sfi.sfi_linkcount,
+		      (unsigned long) subdircount+2);
+		sfi.sfi_linkcount = subdircount+2;
+		ichanged = 1;
+	}
+
+	/*
+	 * Write back anything that changed, clean up, and return.
+	 */
+
+	if (dchanged) {
+		sfs_writedir(&sfi, direntries, ndirentries);
+	}
+
+	if (ichanged) {
+		sfs_writeinode(ino, &sfi);
+	}
+
+	free(direntries);
+	free(sortvector);
+
+	return 0;
+}
+
+void
+pass2(void)
+{
+	char path[SFS_VOLNAME_SIZE + 2];
+
+	snprintf(path, sizeof(path), "%s:", sb_volname());
+	pass2_dir(SFS_ROOTDIR_INO, SFS_ROOTDIR_INO, path);
+}
--- a/userland/sbin/sfsck/passes.h
+++ b/userland/sbin/sfsck/passes.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef PASSES_H
+#define PASSES_H
+
+/*
+ * Pass 1 scans the filesystem starting at the root directory, finding
+ * all reachable directories, files, and blocks, and correcting gross
+ * local errors. The results are used to fix the free block bitmap.
+ *
+ * Pass 2 scans the filesystem starting at the root directory,
+ * checking for crosslinked and malformed directories and accumulating
+ * link count information. Because it runs after we've fixed the free
+ * block bitmap, we can (cautiously) allocate blocks if we need to.
+ */
+
+void pass1(void);
+void pass2(void);
+
+/* After pass1 is done, return the number of dirs and files on the volume. */
+unsigned long pass1_founddirs(void);
+unsigned long pass1_foundfiles(void);
+
+#endif /* PASSES_H */
--- a/userland/sbin/sfsck/sb.c
+++ b/userland/sbin/sfsck/sb.c
@@ -0,0 +1,124 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/types.h>	/* for CHAR_BIT */
+#include <limits.h>	/* also for CHAR_BIT */
+#include <stdint.h>
+#include <assert.h>
+#include <err.h>
+
+#include "compat.h"
+#include <kern/sfs.h>
+
+#include "utils.h"
+#include "sfs.h"
+#include "sb.h"
+#include "freemap.h"
+#include "main.h"
+
+static struct sfs_superblock sb;
+
+/*
+ * Load the superblock.
+ */
+void
+sb_load(void)
+{
+	sfs_readsb(SFS_SUPER_BLOCK, &sb);
+	if (sb.sb_magic != SFS_MAGIC) {
+		errx(EXIT_FATAL, "Not an sfs filesystem");
+	}
+
+	assert(sb.sb_nblocks > 0);
+	assert(SFS_FREEMAPBLOCKS(sb.sb_nblocks) > 0);
+}
+
+/*
+ * Validate the superblock.
+ */
+void
+sb_check(void)
+{
+	int schanged=0;
+
+	/*
+	 * FUTURE: should we check sb.sb_nblocks against diskblocks()?
+	 */
+
+	/* Check the superblock fields */
+
+	if (checknullstring(sb.sb_volname, sizeof(sb.sb_volname))) {
+		warnx("Volume name not null-terminated (fixed)");
+		setbadness(EXIT_RECOV);
+		schanged = 1;
+	}
+	if (checkbadstring(sb.sb_volname)) {
+		warnx("Volume name contains illegal characters (fixed)");
+		setbadness(EXIT_RECOV);
+		schanged = 1;
+	}
+	if (checkzeroed(sb.reserved, sizeof(sb.reserved))) {
+		warnx("Reserved section of superblock not zeroed (fixed)");
+		setbadness(EXIT_RECOV);
+		schanged = 1;
+	}
+
+	/* Write the superblock back if necessary */
+	if (schanged) {
+		sfs_writesb(SFS_SUPER_BLOCK, &sb);
+	}
+}
+
+/*
+ * Return the total number of blocks in the volume.
+ */
+uint32_t
+sb_totalblocks(void)
+{
+	return sb.sb_nblocks;
+}
+
+/*
+ * Return the number of freemap blocks.
+ * (this function probably ought to go away)
+ */
+uint32_t
+sb_freemapblocks(void)
+{
+	return SFS_FREEMAPBLOCKS(sb.sb_nblocks);
+}
+
+/*
+ * Return the volume name.
+ */
+const char *
+sb_volname(void)
+{
+	return sb.sb_volname;
+}
--- a/userland/sbin/sfsck/sb.h
+++ b/userland/sbin/sfsck/sb.h
@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef SB_H
+#define SB_H
+
+/*
+ * The superblock module checks the superblock and provides
+ * information from the superblock to other modules.
+ */
+
+#include <stdint.h>
+
+/* Load the superblock. Should be done before virtually anything else. */
+void sb_load(void);
+
+/* After the superblock is loaded: return volume size. */
+uint32_t sb_totalblocks(void);
+
+/* After the superblock is loaded: return number of freemap blocks. */
+uint32_t sb_freemapblocks(void);
+
+/* After the superblock is loaded: return volume name. */
+const char *sb_volname(void);
+
+/* Check the superblock. Must load it first. */
+void sb_check(void);
+
+#endif /* SB_H */
--- a/userland/sbin/sfsck/sfs.c
+++ b/userland/sbin/sfsck/sfs.c
@@ -0,0 +1,464 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <err.h>
+
+#include "compat.h"
+#include <kern/sfs.h>
+
+#include "disk.h"
+#include "utils.h"
+#include "ibmacros.h"
+#include "sfs.h"
+#include "main.h"
+
+////////////////////////////////////////////////////////////
+// global setup
+
+void
+sfs_setup(void)
+{
+	assert(sizeof(struct sfs_superblock)==SFS_BLOCKSIZE);
+	assert(sizeof(struct sfs_dinode)==SFS_BLOCKSIZE);
+	assert(SFS_BLOCKSIZE % sizeof(struct sfs_direntry) == 0);
+}
+
+////////////////////////////////////////////////////////////
+// byte-swap functions
+
+static
+void
+swapsb(struct sfs_superblock *sb)
+{
+	sb->sb_magic = SWAP32(sb->sb_magic);
+	sb->sb_nblocks = SWAP32(sb->sb_nblocks);
+}
+
+static
+void
+swapbits(uint8_t *bits)
+{
+	/* nothing to do */
+	(void)bits;
+}
+
+static
+void
+swapinode(struct sfs_dinode *sfi)
+{
+	int i;
+
+	sfi->sfi_size = SWAP32(sfi->sfi_size);
+	sfi->sfi_type = SWAP16(sfi->sfi_type);
+	sfi->sfi_linkcount = SWAP16(sfi->sfi_linkcount);
+
+	for (i=0; i<NUM_D; i++) {
+		SET_D(sfi, i) = SWAP32(GET_D(sfi, i));
+	}
+
+	for (i=0; i<NUM_I; i++) {
+		SET_I(sfi, i) = SWAP32(GET_I(sfi, i));
+	}
+
+	for (i=0; i<NUM_II; i++) {
+		SET_II(sfi, i) = SWAP32(GET_II(sfi, i));
+	}
+
+	for (i=0; i<NUM_III; i++) {
+		SET_III(sfi, i) = SWAP32(GET_III(sfi, i));
+	}
+}
+
+static
+void
+swapdir(struct sfs_direntry *sfd)
+{
+	sfd->sfd_ino = SWAP32(sfd->sfd_ino);
+}
+
+static
+void
+swapindir(uint32_t *entries)
+{
+	int i;
+	for (i=0; i<SFS_DBPERIDB; i++) {
+		entries[i] = SWAP32(entries[i]);
+	}
+}
+
+////////////////////////////////////////////////////////////
+// bmap()
+
+/*
+ * Indirect block bmap: in indirect block IBLOCK, read the entry at
+ * block OFFSET from the first file block mapped by this indirect
+ * block.
+ *
+ * ENTRYSIZE is how many blocks each entry describes; for a
+ * singly-indirect block this is 1. For a multiply-indirect block,
+ * it is more than 1; in this case recurse.
+ */
+static
+uint32_t
+ibmap(uint32_t iblock, uint32_t offset, uint32_t entrysize)
+{
+	uint32_t entries[SFS_DBPERIDB];
+
+	if (iblock == 0) {
+		return 0;
+	}
+
+	diskread(entries, iblock);
+	swapindir(entries);
+
+	if (entrysize > 1) {
+		uint32_t index = offset / entrysize;
+		offset %= entrysize;
+		return ibmap(entries[index], offset, entrysize/SFS_DBPERIDB);
+	}
+	else {
+		assert(offset < SFS_DBPERIDB);
+		return entries[offset];
+	}
+}
+
+/*
+ * bmap() for SFS.
+ *
+ * Given an inode and a file block, returns a disk block.
+ */
+static
+uint32_t
+bmap(const struct sfs_dinode *sfi, uint32_t fileblock)
+{
+	uint32_t iblock, offset;
+
+	if (fileblock < INOMAX_D) {
+		return GET_D(sfi, fileblock);
+	}
+	else if (fileblock < INOMAX_I) {
+		iblock = (fileblock - INOMAX_D) / RANGE_I;
+		offset = (fileblock - INOMAX_D) % RANGE_I;
+		return ibmap(GET_I(sfi, iblock), offset, RANGE_D);
+	}
+	else if (fileblock < INOMAX_II) {
+		iblock = (fileblock - INOMAX_I) / RANGE_II;
+		offset = (fileblock - INOMAX_I) % RANGE_II;
+		return ibmap(GET_II(sfi, iblock), offset, RANGE_I);
+	}
+	else if (fileblock < INOMAX_III) {
+		iblock = (fileblock - INOMAX_II) / RANGE_III;
+		offset = (fileblock - INOMAX_II) % RANGE_III;
+		return ibmap(GET_III(sfi, iblock), offset, RANGE_II);
+	}
+	return 0;
+}
+
+////////////////////////////////////////////////////////////
+// superblock, free block bitmap, and inode I/O
+
+/*
+ *  superblock - blocknum is a disk block number.
+ */
+
+void
+sfs_readsb(uint32_t blocknum, struct sfs_superblock *sb)
+{
+	diskread(sb, blocknum);
+	swapsb(sb);
+}
+
+void
+sfs_writesb(uint32_t blocknum, struct sfs_superblock *sb)
+{
+	swapsb(sb);
+	diskwrite(sb, blocknum);
+	swapsb(sb);
+}
+
+/*
+ * freemap blocks - whichblock is a block number within the free block
+ * bitmap.
+ */
+
+void
+sfs_readfreemapblock(uint32_t whichblock, uint8_t *bits)
+{
+	diskread(bits, SFS_FREEMAP_START + whichblock);
+	swapbits(bits);
+}
+
+void
+sfs_writefreemapblock(uint32_t whichblock, uint8_t *bits)
+{
+	swapbits(bits);
+	diskwrite(bits, SFS_FREEMAP_START + whichblock);
+	swapbits(bits);
+}
+
+/*
+ *  inodes - ino is an inode number, which is a disk block number.
+ */
+
+void
+sfs_readinode(uint32_t ino, struct sfs_dinode *sfi)
+{
+	diskread(sfi, ino);
+	swapinode(sfi);
+}
+
+void
+sfs_writeinode(uint32_t ino, struct sfs_dinode *sfi)
+{
+	swapinode(sfi);
+	diskwrite(sfi, ino);
+	swapinode(sfi);
+}
+
+/*
+ *  indirect blocks - blocknum is a disk block number.
+ */
+
+void
+sfs_readindirect(uint32_t blocknum, uint32_t *entries)
+{
+	diskread(entries, blocknum);
+	swapindir(entries);
+}
+
+void
+sfs_writeindirect(uint32_t blocknum, uint32_t *entries)
+{
+	swapindir(entries);
+	diskwrite(entries, blocknum);
+	swapindir(entries);
+}
+
+////////////////////////////////////////////////////////////
+// directory I/O
+
+/*
+ * Read the directory block at DISKBLOCK into D.
+ */
+static
+void
+sfs_readdirblock(struct sfs_direntry *d, uint32_t diskblock)
+{
+	const unsigned atonce = SFS_BLOCKSIZE/sizeof(struct sfs_direntry);
+	unsigned j;
+
+	if (diskblock != 0) {
+		diskread(d, diskblock);
+		for (j=0; j<atonce; j++) {
+			swapdir(&d[j]);
+		}
+	}
+	else {
+		warnx("Warning: sparse directory found");
+		bzero(d, SFS_BLOCKSIZE);
+	}
+}
+
+/*
+ * Read in a directory, from the inode SFI, into D, which is a buffer
+ * with ND slots. The caller is assumed to have figured out the right
+ * number of slots.
+ */
+void
+sfs_readdir(struct sfs_dinode *sfi, struct sfs_direntry *d, unsigned nd)
+{
+	const unsigned atonce = SFS_BLOCKSIZE/sizeof(struct sfs_direntry);
+	unsigned nblocks = SFS_ROUNDUP(nd, atonce) / atonce;
+	unsigned i, j;
+	unsigned left, thismany;
+	struct sfs_direntry buffer[atonce];
+	uint32_t diskblock;
+
+	left = nd;
+	for (i=0; i<nblocks; i++) {
+		diskblock = bmap(sfi, i);
+		if (left < atonce) {
+			thismany = left;
+			sfs_readdirblock(buffer, diskblock);
+			for (j=0; j<thismany; j++) {
+				d[i*atonce + j] = buffer[j];
+			}
+		}
+		else {
+			thismany = atonce;
+			sfs_readdirblock(d + i*atonce, diskblock);
+		}
+		left -= thismany;
+	}
+	assert(left == 0);
+}
+
+/*
+ * Write the directory block D to DISKBLOCK.
+ */
+static
+void
+sfs_writedirblock(struct sfs_direntry *d, uint32_t diskblock)
+{
+	const unsigned atonce = SFS_BLOCKSIZE/sizeof(struct sfs_direntry);
+	unsigned j, bad;
+
+	if (diskblock != 0) {
+		for (j=0; j<atonce; j++) {
+			swapdir(&d[j]);
+		}
+		diskwrite(d, diskblock);
+	}
+	else {
+		for (j=bad=0; j<atonce; j++) {
+			if (d[j].sfd_ino != SFS_NOINO ||
+			    d[j].sfd_name[0] != 0) {
+				bad = 1;
+			}
+		}
+		if (bad) {
+			warnx("Cannot write to missing block in "
+			      "sparse directory (ERROR)");
+			setbadness(EXIT_UNRECOV);
+		}
+	}
+}
+
+/*
+ * Write out a directory, from the inode SFI, using D, which is a
+ * buffer with ND slots. The caller is assumed to have set the inode
+ * size accordingly.
+ */
+void
+sfs_writedir(const struct sfs_dinode *sfi, struct sfs_direntry *d, unsigned nd)
+{
+	const unsigned atonce = SFS_BLOCKSIZE/sizeof(struct sfs_direntry);
+	unsigned nblocks = SFS_ROUNDUP(nd, atonce) / atonce;
+	unsigned i, j;
+	unsigned left, thismany;
+	struct sfs_direntry buffer[atonce];
+	uint32_t diskblock;
+
+	left = nd;
+	for (i=0; i<nblocks; i++) {
+		diskblock = bmap(sfi, i);
+		if (left < atonce) {
+			thismany = left;
+			for (j=0; j<thismany; j++) {
+				buffer[j] = d[i*atonce + j];
+			}
+			for (; j<atonce; j++) {
+				memset(&buffer[j], 0, sizeof(buffer[j]));
+			}
+			sfs_writedirblock(buffer, diskblock);
+		}
+		else {
+			thismany = atonce;
+			sfs_writedirblock(d + i*atonce, diskblock);
+		}
+		left -= thismany;
+	}
+	assert(left == 0);
+}
+
+////////////////////////////////////////////////////////////
+// directory utilities
+
+/* this exists because qsort() doesn't pass a context pointer through */
+static struct sfs_direntry *global_sortdirs;
+
+/*
+ * Compare function for the permutation vector produced by
+ * sfsdir_sort().
+ */
+static
+int
+dirsortfunc(const void *aa, const void *bb)
+{
+	const int *a = (const int *)aa;
+	const int *b = (const int *)bb;
+	const struct sfs_direntry *ad = &global_sortdirs[*a];
+	const struct sfs_direntry *bd = &global_sortdirs[*b];
+
+	/* Sort unallocated entries last */
+	if (ad->sfd_ino == SFS_NOINO && bd->sfd_ino == SFS_NOINO) {
+		return 0;
+	}
+	if (ad->sfd_ino == SFS_NOINO) {
+		return 1;
+	}
+	if (bd->sfd_ino == SFS_NOINO) {
+		return -1;
+	}
+
+	return strcmp(ad->sfd_name, bd->sfd_name);
+}
+
+/*
+ * Sort the directory contents in D (with ND entries) by producing a
+ * permutation vector into VECTOR, which should be allocated to hold
+ * ND ints.
+ */
+void
+sfsdir_sort(struct sfs_direntry *d, unsigned nd, int *vector)
+{
+	unsigned i;
+
+	for (i=0; i<nd; i++) {
+		vector[i] = i;
+	}
+
+	global_sortdirs = d;
+	qsort(vector, nd, sizeof(int), dirsortfunc);
+}
+
+/*
+ * Try to add an entry NAME/INO to D (which has ND entries) by
+ * finding an empty slot. Cannot allocate new space.
+ *
+ * Returns 0 on success and nonzero on failure.
+ */
+int
+sfsdir_tryadd(struct sfs_direntry *d, int nd, const char *name, uint32_t ino)
+{
+	int i;
+	for (i=0; i<nd; i++) {
+		if (d[i].sfd_ino==SFS_NOINO) {
+			d[i].sfd_ino = ino;
+			assert(strlen(name) < sizeof(d[i].sfd_name));
+			strcpy(d[i].sfd_name, name);
+			return 0;
+		}
+	}
+	return -1;
+}
--- a/userland/sbin/sfsck/sfs.h
+++ b/userland/sbin/sfsck/sfs.h
@@ -0,0 +1,81 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef SFS_H
+#define SFS_H
+
+/*
+ * SFS operations. This module provides functions for reading and
+ * writing SFS structures, and knows under the covers how to byte-swap
+ * them. It also provides utility operations on the SFS structures.
+ */
+
+#include <stdint.h>
+
+struct sfs_superblock;
+struct sfs_dinode;
+struct sfs_direntry;
+
+/* Call this before anything else in this module */
+void sfs_setup(void);
+
+/*
+ * Read and write ops for SFS structures
+ */
+
+/* superblock */
+void sfs_readsb(uint32_t blocknum, struct sfs_superblock *sb);
+void sfs_writesb(uint32_t blocknum, struct sfs_superblock *sb);
+
+/* freemap blocks; whichblock is the freemap block number (starts at 0) */
+void sfs_readfreemapblock(uint32_t whichblock, uint8_t *bits);
+void sfs_writefreemapblock(uint32_t whichblock, uint8_t *bits);
+
+/* inode */
+void sfs_readinode(uint32_t inum, struct sfs_dinode *sfi);
+void sfs_writeinode(uint32_t inum, struct sfs_dinode *sfi);
+
+/* indirect block (any indirection level) */
+void sfs_readindirect(uint32_t blocknum, uint32_t *entries);
+void sfs_writeindirect(uint32_t blocknum, uint32_t *entries);
+
+/* directory - ND should be the number of directory entries D points to */
+void sfs_readdir(struct sfs_dinode *sfi, struct sfs_direntry *d, unsigned nd);
+void sfs_writedir(const struct sfs_dinode *sfi,
+		  struct sfs_direntry *d, unsigned nd);
+
+/* Try to add an entry to a directory. */
+int sfsdir_tryadd(struct sfs_direntry *d, int nd,
+		  const char *name, uint32_t ino);
+
+/* Sort a directory by creating a permutation vector. */
+void sfsdir_sort(struct sfs_direntry *d, unsigned nd, int *vector);
+
+
+#endif /* SFS_H */
--- a/userland/sbin/sfsck/utils.c
+++ b/userland/sbin/sfsck/utils.c
@@ -0,0 +1,144 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <err.h>
+
+#include "compat.h"
+#include "utils.h"
+#include "main.h"
+
+/*
+ * Wrapper around malloc.
+ */
+void *
+domalloc(size_t len)
+{
+	void *x;
+	x = malloc(len);
+	if (x==NULL) {
+		errx(EXIT_FATAL, "Out of memory");
+	}
+	return x;
+}
+
+/*
+ * Wrapper around realloc. OSZ is the old block size, which we need if
+ * we're going to emulate realloc with malloc.
+ */
+void *
+dorealloc(void *op, size_t osz, size_t nsz)
+{
+	void *np;
+#ifdef NO_REALLOC
+	size_t copysz;
+
+	np = domalloc(nsz);
+	if (op != NULL) {
+		copysz = osz < nsz ? osz : nsz;
+		memcpy(np, op, copysz);
+		free(op);
+	}
+#else
+	(void)osz;
+	np = realloc(op, nsz);
+	if (np == NULL) {
+		errx(EXIT_FATAL, "Out of memory");
+	}
+#endif
+	return np;
+}
+
+/*
+ * Get a unique id number. (unique as in for this run of sfsck...)
+ */
+uint32_t
+uniqueid(void)
+{
+	static uint32_t uniquecounter;
+
+	return uniquecounter++;
+}
+
+/*
+ * Check if BUF, a string field of length MAXLEN, contains a null
+ * terminator. If not, slam one in and return 1.
+ */
+int
+checknullstring(char *buf, size_t maxlen)
+{
+	size_t i;
+	for (i=0; i<maxlen; i++) {
+		if (buf[i]==0) {
+			return 0;
+		}
+	}
+	buf[maxlen-1] = 0;
+	return 1;
+}
+
+/*
+ * Check if BUF contains characters not allowed in file and volume
+ * names. If so, stomp them and return 1.
+ */
+int
+checkbadstring(char *buf)
+{
+	size_t i;
+	int rv = 0;
+
+	for (i=0; buf[i]; i++) {
+		if (buf[i]==':' || buf[i]=='/') {
+			buf[i] = '_';
+			rv = 1;
+		}
+	}
+	return rv;
+}
+
+/*
+ * Check if BUF, of size LEN, is zeroed. If not, zero it and return 1.
+ */
+int
+checkzeroed(void *vbuf, size_t len)
+{
+	char *buf = vbuf;
+	size_t i;
+	int rv = 0;
+
+	for (i=0; i < len; i++) {
+		if (buf[i] != 0) {
+			buf[i] = 0;
+			rv = 1;
+		}
+	}
+	return rv;
+}
--- a/userland/sbin/sfsck/utils.h
+++ b/userland/sbin/sfsck/utils.h
@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef UTILS_H
+#define UTILS_H
+
+#include <sys/types.h>	/* for size_t */
+#include <stdint.h>	/* for uint32_t */
+
+/* non-failing wrapper around malloc */
+void *domalloc(size_t len);
+void *dorealloc(void *op, size_t osz, size_t nsz);
+
+/* return a fresh id number */
+uint32_t uniqueid(void);
+
+/* ensure that BUF (of size MAXLEN) is terminated; return 1 if changed */
+int checknullstring(char *buf, size_t maxlen);
+
+/* check for illegal filename characters; if found, zap them and return 1 */
+int checkbadstring(char *buf);
+
+/* check for nonzero bytes in a zeroed area; if found, zap and return 1 */
+int checkzeroed(void *buf, size_t len);
+
+#endif /* UTILS_H */