Now using static buffers (and protecting with a semaphore) for kernel secprintf.

We have to do this because we need secure output in kmalloc.

common/libtest161/secure.c

@@ -44,35 +44,25 @@ static int did_random = 0;
 #define MSEC_PER_SEC 1000ULL
 #endif
 
+// Both userspace and the kernel are using the temp buffers now.
 static void * _alloc(size_t size)
 {
-#ifdef _KERNEL
-	// Compiler
-	(void)temp_buffers;
-	(void)buf_num;
-
-	return kmalloc(size);
-#else
 	(void)size;
 	void *ptr = temp_buffers[buf_num];
 	buf_num++;
 	buf_num = buf_num % NUM_BUFFERS;
 	return ptr;
-#endif
 }
 
 static void _free(void *ptr)
 {
-#ifdef _KERNEL
-	kfree(ptr);
-#else
 	(void)ptr;
-#endif
 }
 
 /*
  * hamc_sha256 follows FIPS 198-1 HMAC using sha256.
  * See http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.180-4.pdf for details.
+ * NOTE: This is only thread-safe if called from within secprintf()!!!
  */
 static int hmac_sha256(const char *msg, size_t msg_len, const char *key, size_t key_len, 
 		unsigned char output[SHA256_OUTPUT_SIZE])
@@ -189,6 +179,7 @@ int hmac(const char *msg, size_t msg_len, const char *key, size_t key_len,
 	return 0;
 }
 
+// NOTE: This is only thread-safe if called from within secprintf()!!!
 int hmac_salted(const char *msg, size_t msg_len, const char *key, size_t key_len, 
 		char **hash_str, char **salt_str)
 {

common/libtest161/test161.c

@@ -3,6 +3,7 @@
 #ifdef _KERNEL
 #include <types.h>
 #include <lib.h>
+#include <synch.h>
 #include <kern/errno.h>
 #include <kern/secure.h>
 #include <kern/test161.h>
@@ -17,31 +18,32 @@
 #include <test161/secure.h>
 #endif
 
-// Hack for allocating userspace memory without malloc.
-#define BUFFER_SIZE 4096
+// Hack for allocating userspace memory without malloc, and for
+// allowing secprintf in kmalloc when we're out of memory.
+#define BUFFER_SIZE 1024
+
+static char temp_buffer[BUFFER_SIZE];
 
 #ifndef _KERNEL
-static char temp_buffer[BUFFER_SIZE];
 static char write_buffer[BUFFER_SIZE];
 #endif
 
-static inline void * _alloc(size_t size)
-{
 #ifdef _KERNEL
-	return kmalloc(size);
-#else
-	(void)size;
-	return temp_buffer;
+// secprintf needs to be synchronized in the kernel because multiple threads
+// may be trying to secprintf at the same time.
+static struct semaphore *test161_sem;
 #endif
+
+// For now, allocating just passes a reference to our static temp buffer, and
+// free does nothing.
+static inline void * _alloc()
+{
+	return temp_buffer;
 }
 
 static inline void _free(void *ptr)
 {
-#ifdef _KERNEL
-	kfree(ptr);
-#else
 	(void)ptr;
-#endif
 }
 
 /*
@@ -106,19 +108,29 @@ secprintf(const char * secret, const char * msg, const char * name)
 	int res;
 	size_t len;
 
+#ifdef _KERNEL
+	if (test161_sem == NULL) {
+		panic("test161_sem is NULL. Your kernel is missing test161_bootstrap.");
+	}
+	P(test161_sem);
+#endif
+
 	hash = salt = fullmsg = NULL;
 
 	// test161 expects "name: msg"
 	len = strlen(name) + strlen(msg) + 3;	// +3 for " :" and null terminator
 	fullmsg = (char *)_alloc(len);
 	if (fullmsg == NULL) {
-		return -ENOMEM;
+		res = -ENOMEM;
+		goto out;
 	}
 	snprintf(fullmsg, len, "%s: %s", name, msg);
 
 	res = hmac_salted(fullmsg, len-1, secret, strlen(secret), &hash, &salt);
-	if (res)
-		return -res;
+	if (res) {
+		res = -res;
+		goto out;
+	}
 
 #ifdef _KERNEL
 	res = kprintf("(%s, %s, %s, %s: %s)\n", name, hash, salt, name, msg);
@@ -126,11 +138,27 @@ secprintf(const char * secret, const char * msg, const char * name)
 	res = say("(%s, %s, %s, %s: %s)\n", name, hash, salt, name, msg);
 #endif
 
+out:
+	// These may be NULL, but that's OK
 	_free(hash);
 	_free(salt);
 	_free(fullmsg);
 
+#ifdef _KERNEL
+	V(test161_sem);
+#endif
+
 	return res;
 }
 
 #endif
+
+#ifdef _KERNEL
+void test161_bootstrap()
+{
+	test161_sem = sem_create("test161", 1);
+	if (test161_sem == NULL) {
+		panic("Failed to create test161 secprintf semaphore");
+	}
+}
+#endif

kern/include/kern/test161.h

@@ -39,4 +39,8 @@ int success(int, const char *, const char *);
 int secprintf(const char *secret, const char *msg, const char *name);
 int partial_credit(const char *secret, const char *name, int scored, int total);
 
+#ifdef _KERNEL
+void test161_bootstrap(void);
+#endif
+
 #endif /* _KERN_TEST161_H_ */

kern/main/main.c

@@ -48,6 +48,7 @@
 #include <device.h>
 #include <syscall.h>
 #include <test.h>
+#include <kern/test161.h>
 #include <version.h>
 #include "autoconf.h"  // for pseudoconfig
 
@@ -127,6 +128,7 @@ boot(void)
 	vm_bootstrap();
 	kprintf_bootstrap();
 	thread_start_cpus();
+	test161_bootstrap();
 
 	/* Default bootfs - but ignore failure, in case emu0 doesn't exist */
 	vfs_setbootfs("emu0");