Initial Spring 2016 commit.

kern/arch/mips/vm/ram.c

@@ -0,0 +1,153 @@
+/*
+ * 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 <types.h>
+#include <lib.h>
+#include <vm.h>
+#include <mainbus.h>
+
+
+vaddr_t firstfree;   /* first free virtual address; set by start.S */
+
+static paddr_t firstpaddr;  /* address of first free physical page */
+static paddr_t lastpaddr;   /* one past end of last free physical page */
+
+/*
+ * Called very early in system boot to figure out how much physical
+ * RAM is available.
+ */
+void
+ram_bootstrap(void)
+{
+	size_t ramsize;
+
+	/* Get size of RAM. */
+	ramsize = mainbus_ramsize();
+
+	/*
+	 * This is the same as the last physical address, as long as
+	 * we have less than 512 megabytes of memory. If we had more,
+	 * we wouldn't be able to access it all through kseg0 and
+	 * everything would get a lot more complicated. This is not a
+	 * case we are going to worry about.
+	 */
+	if (ramsize > 512*1024*1024) {
+		ramsize = 512*1024*1024;
+	}
+
+	lastpaddr = ramsize;
+
+	/*
+	 * Get first free virtual address from where start.S saved it.
+	 * Convert to physical address.
+	 */
+	firstpaddr = firstfree - MIPS_KSEG0;
+
+	kprintf("%uk physical memory available\n",
+		(lastpaddr-firstpaddr)/1024);
+}
+
+/*
+ * This function is for allocating physical memory prior to VM
+ * initialization.
+ *
+ * The pages it hands back will not be reported to the VM system when
+ * the VM system calls ram_getsize(). If it's desired to free up these
+ * pages later on after bootup is complete, some mechanism for adding
+ * them to the VM system's page management must be implemented.
+ * Alternatively, one can do enough VM initialization early so that
+ * this function is never needed.
+ *
+ * Note: while the error return value of 0 is a legal physical address,
+ * it's not a legal *allocatable* physical address, because it's the
+ * page with the exception handlers on it.
+ *
+ * This function should not be called once the VM system is initialized,
+ * so it is not synchronized.
+ */
+paddr_t
+ram_stealmem(unsigned long npages)
+{
+	size_t size;
+	paddr_t paddr;
+
+	size = npages * PAGE_SIZE;
+
+	if (firstpaddr + size > lastpaddr) {
+		return 0;
+	}
+
+	paddr = firstpaddr;
+	firstpaddr += size;
+
+	return paddr;
+}
+
+/*
+ * This function is intended to be called by the VM system when it
+ * initializes in order to find out what memory it has available to
+ * manage. Physical memory begins at physical address 0 and ends with
+ * the address returned by this function. We assume that physical
+ * memory is contiguous. This is not universally true, but is true on
+ * the MIPS platforms we intend to run on.
+ *
+ * lastpaddr is constant once set by ram_bootstrap(), so this function
+ * need not be synchronized.
+ *
+ * It is recommended, however, that this function be used only to
+ * initialize the VM system, after which the VM system should take
+ * charge of knowing what memory exists.
+ */
+paddr_t
+ram_getsize(void)
+{
+	return lastpaddr;
+}
+
+/*
+ * This function is intended to be called by the VM system when it
+ * initializes in order to find out what memory it has available to
+ * manage.
+ *
+ * It can only be called once, and once called ram_stealmem() will
+ * no longer work, as that would invalidate the result it returned
+ * and lead to multiple things using the same memory.
+ *
+ * This function should not be called once the VM system is initialized,
+ * so it is not synchronized.
+ */
+paddr_t
+ram_getfirstfree(void)
+{
+	paddr_t ret;
+
+	ret = firstpaddr;
+	firstpaddr = lastpaddr = 0;
+	return ret;
+}