[PATCH 8/14] kexec: kexec-generic

[Eric W. Biederman]

Here is the architecture independent part of kexec.

diff -uNr linux-2.6.8.1-mm2-e820-64bit.x86_64/MAINTAINERS linux-2.6.8.1-mm2-kexec-generic/MAINTAINERS
--- linux-2.6.8.1-mm2-e820-64bit.x86_64/MAINTAINERS	Fri Aug 20 09:56:45 2004
+++ linux-2.6.8.1-mm2-kexec-generic/MAINTAINERS	Fri Aug 20 10:43:51 2004
@@ -1244,6 +1244,17 @@
 W:	http://www.cse.unsw.edu.au/~neilb/patches/linux-devel/
 S:	Maintained
 
+KEXEC
+P:	Eric Biederman
+P:	Randy Dunlap
+M:	ebiederm@xxxxxxxxxxxx
+M:	rddunlap@xxxxxxxx
+W:	http://www.xmission.com/~ebiederm/files/kexec/
+W:	http://developer.osdl.org/rddunlap/kexec/
+L:	linux-kernel@xxxxxxxxxxxxxxx
+L:	fastboot@xxxxxxxx
+S:	Maintained
+
 LANMEDIA WAN CARD DRIVER
 P:	Andrew Stanley-Jones
 M:	asj@xxxxxxxxxxxx
diff -uNr linux-2.6.8.1-mm2-e820-64bit.x86_64/include/linux/kexec.h linux-2.6.8.1-mm2-kexec-generic/include/linux/kexec.h
--- linux-2.6.8.1-mm2-e820-64bit.x86_64/include/linux/kexec.h	Wed Dec 31 17:00:00 1969
+++ linux-2.6.8.1-mm2-kexec-generic/include/linux/kexec.h	Fri Aug 20 10:43:51 2004
@@ -0,0 +1,56 @@
+#ifndef LINUX_KEXEC_H
+#define LINUX_KEXEC_H
+
+#if CONFIG_KEXEC
+#include <linux/types.h>
+#include <linux/list.h>
+#include <asm/kexec.h>
+
+/*
+ * This structure is used to hold the arguments that are used when loading
+ * kernel binaries.
+ */
+
+typedef unsigned long kimage_entry_t;
+#define IND_DESTINATION  0x1
+#define IND_INDIRECTION  0x2
+#define IND_DONE         0x4
+#define IND_SOURCE       0x8
+
+#define KEXEC_SEGMENT_MAX 8
+struct kexec_segment {
+	void *buf;
+	size_t bufsz;
+	void *mem;
+	size_t memsz;
+};
+
+struct kimage {
+	kimage_entry_t head;
+	kimage_entry_t *entry;
+	kimage_entry_t *last_entry;
+
+	unsigned long destination;
+
+	unsigned long start;
+	struct page *control_code_page;
+
+	unsigned long nr_segments;
+	struct kexec_segment segment[KEXEC_SEGMENT_MAX];
+
+	struct list_head control_pages;
+	struct list_head dest_pages;
+	struct list_head unuseable_pages;
+};
+
+
+/* kexec interface functions */
+extern void machine_kexec(struct kimage *image);
+extern int machine_kexec_prepare(struct kimage *image);
+extern void machine_kexec_cleanup(struct kimage *image);
+extern asmlinkage long sys_kexec(unsigned long entry, long nr_segments,
+	struct kexec_segment *segments);
+extern struct page *kimage_alloc_control_pages(struct kimage *image, unsigned int order);
+extern struct kimage *kexec_image;
+#endif
+#endif /* LINUX_KEXEC_H */
diff -uNr linux-2.6.8.1-mm2-e820-64bit.x86_64/include/linux/reboot.h linux-2.6.8.1-mm2-kexec-generic/include/linux/reboot.h
--- linux-2.6.8.1-mm2-e820-64bit.x86_64/include/linux/reboot.h	Thu Jul 15 07:27:45 2004
+++ linux-2.6.8.1-mm2-kexec-generic/include/linux/reboot.h	Fri Aug 20 10:43:51 2004
@@ -51,6 +51,8 @@
 extern void machine_halt(void);
 extern void machine_power_off(void);
 
+extern void machine_shutdown(void);
+
 #endif
 
 #endif /* _LINUX_REBOOT_H */
diff -uNr linux-2.6.8.1-mm2-e820-64bit.x86_64/kernel/Makefile linux-2.6.8.1-mm2-kexec-generic/kernel/Makefile
--- linux-2.6.8.1-mm2-e820-64bit.x86_64/kernel/Makefile	Fri Aug 20 09:56:45 2004
+++ linux-2.6.8.1-mm2-kexec-generic/kernel/Makefile	Fri Aug 20 10:43:51 2004
@@ -18,6 +18,7 @@
 obj-$(CONFIG_KALLSYMS) += kallsyms.o
 obj-$(CONFIG_PM) += power/
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
+obj-$(CONFIG_KEXEC) += kexec.o
 obj-$(CONFIG_COMPAT) += compat.o
 obj-$(CONFIG_IKCONFIG) += configs.o
 obj-$(CONFIG_IKCONFIG_PROC) += configs.o
diff -uNr linux-2.6.8.1-mm2-e820-64bit.x86_64/kernel/kexec.c linux-2.6.8.1-mm2-kexec-generic/kernel/kexec.c
--- linux-2.6.8.1-mm2-e820-64bit.x86_64/kernel/kexec.c	Wed Dec 31 17:00:00 1969
+++ linux-2.6.8.1-mm2-kexec-generic/kernel/kexec.c	Fri Aug 20 10:43:51 2004
@@ -0,0 +1,640 @@
+/*
+ * kexec.c - kexec system call
+ * Copyright (C) 2002-2004 Eric Biederman  <ebiederm@xxxxxxxxxxxx>
+ *
+ * This source code is licensed under the GNU General Public License,
+ * Version 2.  See the file COPYING for more details.
+ */
+
+#include <linux/mm.h>
+#include <linux/file.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/kexec.h>
+#include <linux/spinlock.h>
+#include <linux/list.h>
+#include <linux/highmem.h>
+#include <net/checksum.h>
+#include <asm/page.h>
+#include <asm/uaccess.h>
+#include <asm/io.h>
+#include <asm/system.h>
+
+/*
+ * When kexec transitions to the new kernel there is a one-to-one
+ * mapping between physical and virtual addresses.  On processors
+ * where you can disable the MMU this is trivial, and easy.  For
+ * others it is still a simple predictable page table to setup.
+ *
+ * In that environment kexec copies the new kernel to its final
+ * resting place.  This means I can only support memory whose
+ * physical address can fit in an unsigned long.  In particular
+ * addresses where (pfn << PAGE_SHIFT) > ULONG_MAX cannot be handled.
+ * If the assembly stub has more restrictive requirements
+ * KEXEC_SOURCE_MEMORY_LIMIT and KEXEC_DEST_MEMORY_LIMIT can be
+ * defined more restrictively in <asm/kexec.h>.
+ *
+ * The code for the transition from the current kernel to the
+ * the new kernel is placed in the control_code_buffer, whose size
+ * is given by KEXEC_CONTROL_CODE_SIZE.  In the best case only a single
+ * page of memory is necessary, but some architectures require more.
+ * Because this memory must be identity mapped in the transition from
+ * virtual to physical addresses it must live in the range
+ * 0 - TASK_SIZE, as only the user space mappings are arbitrarily
+ * modifiable.
+ *
+ * The assembly stub in the control code buffer is passed a linked list
+ * of descriptor pages detailing the source pages of the new kernel,
+ * and the destination addresses of those source pages.  As this data
+ * structure is not used in the context of the current OS, it must
+ * be self-contained.
+ *
+ * The code has been made to work with highmem pages and will use a
+ * destination page in its final resting place (if it happens
+ * to allocate it).  The end product of this is that most of the
+ * physical address space, and most of RAM can be used.
+ *
+ * Future directions include:
+ *  - allocating a page table with the control code buffer identity
+ *    mapped, to simplify machine_kexec and make kexec_on_panic more
+ *    reliable.
+ */
+
+/*
+ * KIMAGE_NO_DEST is an impossible destination address..., for
+ * allocating pages whose destination address we do not care about.
+ */
+#define KIMAGE_NO_DEST (-1UL)
+
+static int kimage_is_destination_range(
+	struct kimage *image, unsigned long start, unsigned long end);
+static struct page *kimage_alloc_page(struct kimage *image, unsigned int gfp_mask, unsigned long dest);
+
+
+static int kimage_alloc(struct kimage **rimage,
+	unsigned long nr_segments, struct kexec_segment *segments)
+{
+	int result;
+	struct kimage *image;
+	size_t segment_bytes;
+	unsigned long i;
+
+	/* Allocate a controlling structure */
+	result = -ENOMEM;
+	image = kmalloc(sizeof(*image), GFP_KERNEL);
+	if (!image) {
+		goto out;
+	}
+	memset(image, 0, sizeof(*image));
+	image->head = 0;
+	image->entry = &image->head;
+	image->last_entry = &image->head;
+
+	/* Initialize the list of control pages */
+	INIT_LIST_HEAD(&image->control_pages);
+
+	/* Initialize the list of destination pages */
+	INIT_LIST_HEAD(&image->dest_pages);
+
+	/* Initialize the list of unuseable pages */
+	INIT_LIST_HEAD(&image->unuseable_pages);
+
+	/* Read in the segments */
+	image->nr_segments = nr_segments;
+	segment_bytes = nr_segments * sizeof*segments;
+	result = copy_from_user(image->segment, segments, segment_bytes);
+	if (result)
+		goto out;
+
+	/*
+	 * Verify we have good destination addresses.  The caller is
+	 * responsible for making certain we don't attempt to load
+	 * the new image into invalid or reserved areas of RAM.  This
+	 * just verifies it is an address we can use.
+	 */
+	result = -EADDRNOTAVAIL;
+	for (i = 0; i < nr_segments; i++) {
+		unsigned long mend;
+		mend = ((unsigned long)(image->segment[i].mem)) +
+			image->segment[i].memsz;
+		if (mend >= KEXEC_DESTINATION_MEMORY_LIMIT)
+			goto out;
+	}
+
+	/*
+	 * Find a location for the control code buffer, and add it
+	 * the vector of segments so that it's pages will also be
+	 * counted as destination pages.
+	 */
+	result = -ENOMEM;
+	image->control_code_page = kimage_alloc_control_pages(image,
+		get_order(KEXEC_CONTROL_CODE_SIZE));
+	if (!image->control_code_page) {
+		printk(KERN_ERR "Could not allocate control_code_buffer\n");
+		goto out;
+	}
+
+	result = 0;
+ out:
+	if (result == 0) {
+		*rimage = image;
+	} else {
+		kfree(image);
+	}
+	return result;
+}
+
+static int kimage_is_destination_range(
+	struct kimage *image, unsigned long start, unsigned long end)
+{
+	unsigned long i;
+
+	for (i = 0; i < image->nr_segments; i++) {
+		unsigned long mstart, mend;
+		mstart = (unsigned long)image->segment[i].mem;
+		mend   = mstart + image->segment[i].memsz;
+		if ((end > mstart) && (start < mend)) {
+			return 1;
+		}
+	}
+	return 0;
+}
+
+static struct page *kimage_alloc_pages(unsigned int gfp_mask, unsigned int order)
+{
+	struct page *pages;
+	pages = alloc_pages(gfp_mask, order);
+	if (pages) {
+		unsigned int count, i;
+		pages->mapping = NULL;
+		pages->private = order;
+		count = 1 << order;
+		for(i = 0; i < count; i++) {
+			SetPageReserved(pages + i);
+		}
+	}
+	return pages;
+}
+
+static void kimage_free_pages(struct page *page)
+{
+	unsigned int order, count, i;
+	order = page->private;
+	count = 1 << order;
+	for(i = 0; i < count; i++) {
+		ClearPageReserved(page + i);
+	}
+	__free_pages(page, order);
+}
+
+static void kimage_free_page_list(struct list_head *list)
+{
+	struct list_head *pos, *next;
+	list_for_each_safe(pos, next, list) {
+		struct page *page;
+
+		page = list_entry(pos, struct page, lru);
+		list_del(&page->lru);
+
+		kimage_free_pages(page);
+	}
+}
+		
+struct page *kimage_alloc_control_pages(struct kimage *image, unsigned int order)
+{
+	/* Control pages are special, they are the intermediaries
+	 * that are needed while we copy the rest of the pages
+	 * to their final resting place.  As such they must
+	 * not conflict with either the destination addresses
+	 * or memory the kernel is already using.
+	 *
+	 * The only case where we really need more than one of
+	 * these are for architectures where we cannot disable
+	 * the MMU and must instead generate an identity mapped
+	 * page table for all of the memory.
+	 *
+	 * At worst this runs in O(N) of the image size.
+	 */
+	struct list_head extra_pages;
+	struct page *pages;
+	unsigned int count;
+
+	count = 1 << order;
+	INIT_LIST_HEAD(&extra_pages);
+
+	/* Loop while I can allocate a page and the page allocated
+	 * is a destination page.
+	 */
+	do {
+		unsigned long pfn, epfn, addr, eaddr;
+		pages = kimage_alloc_pages(GFP_KERNEL, order);
+		if (!pages)
+			break;
+		pfn   = page_to_pfn(pages);
+		epfn  = pfn + count;
+		addr  = pfn << PAGE_SHIFT;
+		eaddr = epfn << PAGE_SHIFT;
+		if ((epfn >= (KEXEC_CONTROL_MEMORY_LIMIT >> PAGE_SHIFT)) ||
+			kimage_is_destination_range(image, addr, eaddr))
+		{
+			list_add(&pages->lru, &extra_pages);
+			pages = NULL;
+		}
+	} while(!pages);
+	if (pages) {
+		/* Remember the allocated page... */
+		list_add(&pages->lru, &image->control_pages);
+
+		/* Because the page is already in it's destination
+		 * location we will never allocate another page at
+		 * that address.  Therefore kimage_alloc_pages
+		 * will not return it (again) and we don't need
+		 * to give it an entry in image->segment[].
+		 */
+	}
+	/* Deal with the destination pages I have inadvertently allocated.
+	 *
+	 * Ideally I would convert multi-page allocations into single
+	 * page allocations, and add everyting to image->dest_pages.
+	 * 
+	 * For now it is simpler to just free the pages.
+	 */
+	kimage_free_page_list(&extra_pages);
+	return pages;
+	
+}
+
+static int kimage_add_entry(struct kimage *image, kimage_entry_t entry)
+{
+	if (*image->entry != 0) {
+		image->entry++;
+	}
+	if (image->entry == image->last_entry) {
+		kimage_entry_t *ind_page;
+		struct page *page;
+		page = kimage_alloc_page(image, GFP_KERNEL, KIMAGE_NO_DEST);
+		if (!page) {
+			return -ENOMEM;
+		}
+		ind_page = page_address(page);
+		*image->entry = virt_to_phys(ind_page) | IND_INDIRECTION;
+		image->entry = ind_page;
+		image->last_entry =
+			ind_page + ((PAGE_SIZE/sizeof(kimage_entry_t)) - 1);
+	}
+	*image->entry = entry;
+	image->entry++;
+	*image->entry = 0;
+	return 0;
+}
+
+static int kimage_set_destination(
+	struct kimage *image, unsigned long destination)
+{
+	int result;
+
+	destination &= PAGE_MASK;
+	result = kimage_add_entry(image, destination | IND_DESTINATION);
+	if (result == 0) {
+		image->destination = destination;
+	}
+	return result;
+}
+
+
+static int kimage_add_page(struct kimage *image, unsigned long page)
+{
+	int result;
+
+	page &= PAGE_MASK;
+	result = kimage_add_entry(image, page | IND_SOURCE);
+	if (result == 0) {
+		image->destination += PAGE_SIZE;
+	}
+	return result;
+}
+
+
+static void kimage_free_extra_pages(struct kimage *image)
+{
+	/* Walk through and free any extra destination pages I may have */
+	kimage_free_page_list(&image->dest_pages);
+
+	/* Walk through and free any unuseable pages I have cached */
+	kimage_free_page_list(&image->unuseable_pages);
+
+}
+static int kimage_terminate(struct kimage *image)
+{
+	int result;
+
+	result = kimage_add_entry(image, IND_DONE);
+	if (result == 0) {
+		/* Point at the terminating element */
+		image->entry--;
+		kimage_free_extra_pages(image);
+	}
+	return result;
+}
+
+#define for_each_kimage_entry(image, ptr, entry) \
+	for (ptr = &image->head; (entry = *ptr) && !(entry & IND_DONE); \
+		ptr = (entry & IND_INDIRECTION)? \
+			phys_to_virt((entry & PAGE_MASK)): ptr +1)
+
+static void kimage_free_entry(kimage_entry_t entry)
+{
+	struct page *page;
+
+	page = pfn_to_page(entry >> PAGE_SHIFT);
+	kimage_free_pages(page);
+}
+
+static void kimage_free(struct kimage *image)
+{
+	kimage_entry_t *ptr, entry;
+	kimage_entry_t ind = 0;
+
+	if (!image)
+		return;
+	kimage_free_extra_pages(image);
+	for_each_kimage_entry(image, ptr, entry) {
+		if (entry & IND_INDIRECTION) {
+			/* Free the previous indirection page */
+			if (ind & IND_INDIRECTION) {
+				kimage_free_entry(ind);
+			}
+			/* Save this indirection page until we are
+			 * done with it.
+			 */
+			ind = entry;
+		}
+		else if (entry & IND_SOURCE) {
+			kimage_free_entry(entry);
+		}
+	}
+	/* Free the final indirection page */
+	if (ind & IND_INDIRECTION) {
+		kimage_free_entry(ind);
+	}
+
+	/* Handle any machine specific cleanup */
+	machine_kexec_cleanup(image);
+
+	/* Free the kexec control pages... */
+	kimage_free_page_list(&image->control_pages);
+	kfree(image);
+}
+
+static kimage_entry_t *kimage_dst_used(struct kimage *image, unsigned long page)
+{
+	kimage_entry_t *ptr, entry;
+	unsigned long destination = 0;
+
+	for_each_kimage_entry(image, ptr, entry) {
+		if (entry & IND_DESTINATION) {
+			destination = entry & PAGE_MASK;
+		}
+		else if (entry & IND_SOURCE) {
+			if (page == destination) {
+				return ptr;
+			}
+			destination += PAGE_SIZE;
+		}
+	}
+	return 0;
+}
+
+static struct page *kimage_alloc_page(struct kimage *image, unsigned int gfp_mask, unsigned long destination)
+{
+	/*
+	 * Here we implement safeguards to ensure that a source page
+	 * is not copied to its destination page before the data on
+	 * the destination page is no longer useful.
+	 *
+	 * To do this we maintain the invariant that a source page is
+	 * either its own destination page, or it is not a
+	 * destination page at all.
+	 *
+	 * That is slightly stronger than required, but the proof
+	 * that no problems will not occur is trivial, and the
+	 * implementation is simply to verify.
+	 *
+	 * When allocating all pages normally this algorithm will run
+	 * in O(N) time, but in the worst case it will run in O(N^2)
+	 * time.   If the runtime is a problem the data structures can
+	 * be fixed.
+	 */
+	struct page *page;
+	unsigned long addr;
+
+	/*
+	 * Walk through the list of destination pages, and see if I
+	 * have a match.
+	 */
+	list_for_each_entry(page, &image->dest_pages, lru) {
+		addr = page_to_pfn(page) << PAGE_SHIFT;
+		if (addr == destination) {
+			list_del(&page->lru);
+			return page;
+		}
+	}
+	page = NULL;
+	while (1) {
+		kimage_entry_t *old;
+
+		/* Allocate a page, if we run out of memory give up */
+		page = kimage_alloc_pages(gfp_mask, 0);
+		if (!page) {
+			return 0;
+		}
+		/* If the page cannot be used file it away */
+		if (page_to_pfn(page) > (KEXEC_SOURCE_MEMORY_LIMIT >> PAGE_SHIFT)) {
+			list_add(&page->lru, &image->unuseable_pages);
+			continue;
+		}
+		addr = page_to_pfn(page) << PAGE_SHIFT;
+
+		/* If it is the destination page we want use it */
+		if (addr == destination)
+			break;
+
+		/* If the page is not a destination page use it */
+		if (!kimage_is_destination_range(image, addr, addr + PAGE_SIZE))
+			break;
+
+		/*
+		 * I know that the page is someones destination page.
+		 * See if there is already a source page for this
+		 * destination page.  And if so swap the source pages.
+		 */
+		old = kimage_dst_used(image, addr);
+		if (old) {
+			/* If so move it */
+			unsigned long old_addr;
+			struct page *old_page;
+
+			old_addr = *old & PAGE_MASK;
+			old_page = pfn_to_page(old_addr >> PAGE_SHIFT);
+			copy_highpage(page, old_page);
+			*old = addr | (*old & ~PAGE_MASK);
+
+			/* The old page I have found cannot be a
+			 * destination page, so return it.
+			 */
+			addr = old_addr;
+			page = old_page;
+			break;
+		}
+		else {
+			/* Place the page on the destination list I
+			 * will use it later.
+			 */
+			list_add(&page->lru, &image->dest_pages);
+		}
+	}
+	return page;
+}
+
+static int kimage_load_segment(struct kimage *image,
+	struct kexec_segment *segment)
+{
+	unsigned long mstart;
+	int result;
+	unsigned long offset;
+	unsigned long offset_end;
+	unsigned char *buf;
+
+	result = 0;
+	buf = segment->buf;
+	mstart = (unsigned long)segment->mem;
+
+	offset_end = segment->memsz;
+
+	result = kimage_set_destination(image, mstart);
+	if (result < 0) {
+		goto out;
+	}
+	for (offset = 0;  offset < segment->memsz; offset += PAGE_SIZE) {
+		struct page *page;
+		char *ptr;
+		size_t size, leader;
+		page = kimage_alloc_page(image, GFP_HIGHUSER, mstart + offset);
+		if (page == 0) {
+			result  = -ENOMEM;
+			goto out;
+		}
+		result = kimage_add_page(image, page_to_pfn(page) << PAGE_SHIFT);
+		if (result < 0) {
+			goto out;
+		}
+		ptr = kmap(page);
+		if (segment->bufsz < offset) {
+			/* We are past the end zero the whole page */
+			memset(ptr, 0, PAGE_SIZE);
+			kunmap(page);
+			continue;
+		}
+		size = PAGE_SIZE;
+		leader = 0;
+		if ((offset == 0)) {
+			leader = mstart & ~PAGE_MASK;
+		}
+		if (leader) {
+			/* We are on the first page zero the unused portion */
+			memset(ptr, 0, leader);
+			size -= leader;
+			ptr += leader;
+		}
+		if (size > (segment->bufsz - offset)) {
+			size = segment->bufsz - offset;
+		}
+		if (size < (PAGE_SIZE - leader)) {
+			/* zero the trailing part of the page */
+			memset(ptr + size, 0, (PAGE_SIZE - leader) - size);
+		}
+		result = copy_from_user(ptr, buf + offset, size);
+		kunmap(page);
+		if (result) {
+			result = (result < 0) ? result : -EIO;
+			goto out;
+		}
+	}
+ out:
+	return result;
+}
+
+/*
+ * Exec Kernel system call: for obvious reasons only root may call it.
+ *
+ * This call breaks up into three pieces.
+ * - A generic part which loads the new kernel from the current
+ *   address space, and very carefully places the data in the
+ *   allocated pages.
+ *
+ * - A generic part that interacts with the kernel and tells all of
+ *   the devices to shut down.  Preventing on-going dmas, and placing
+ *   the devices in a consistent state so a later kernel can
+ *   reinitialize them.
+ *
+ * - A machine specific part that includes the syscall number
+ *   and the copies the image to it's final destination.  And
+ *   jumps into the image at entry.
+ *
+ * kexec does not sync, or unmount filesystems so if you need
+ * that to happen you need to do that yourself.
+ */
+struct kimage *kexec_image = NULL;
+
+asmlinkage long sys_kexec_load(unsigned long entry, unsigned long nr_segments,
+	struct kexec_segment *segments, unsigned long flags)
+{
+	struct kimage *image;
+	int result;
+
+	/* We only trust the superuser with rebooting the system. */
+	if (!capable(CAP_SYS_BOOT))
+		return -EPERM;
+
+	/*
+	 * In case we need just a little bit of special behavior for
+	 * reboot on panic.
+	 */
+	if (flags != 0)
+		return -EINVAL;
+
+	if (nr_segments > KEXEC_SEGMENT_MAX)
+		return -EINVAL;
+
+	image = NULL;
+	result = 0;
+
+	if (nr_segments > 0) {
+		unsigned long i;
+		result = kimage_alloc(&image, nr_segments, segments);
+		if (result) {
+			goto out;
+		}
+		result = machine_kexec_prepare(image);
+		if (result) {
+			goto out;
+		}
+		image->start = entry;
+		for (i = 0; i < nr_segments; i++) {
+			result = kimage_load_segment(image, &image->segment[i]);
+			if (result) {
+				goto out;
+			}
+		}
+		result = kimage_terminate(image);
+		if (result) {
+			goto out;
+		}
+	}
+
+	image = xchg(&kexec_image, image);
+
+ out:
+	kimage_free(image);
+	return result;
+}
diff -uNr linux-2.6.8.1-mm2-e820-64bit.x86_64/kernel/sys.c linux-2.6.8.1-mm2-kexec-generic/kernel/sys.c
--- linux-2.6.8.1-mm2-e820-64bit.x86_64/kernel/sys.c	Fri Aug 20 09:56:45 2004
+++ linux-2.6.8.1-mm2-kexec-generic/kernel/sys.c	Fri Aug 20 10:43:51 2004
@@ -17,6 +17,8 @@
 #include <linux/init.h>
 #include <linux/highuid.h>
 #include <linux/fs.h>
+#include <linux/kernel.h>
+#include <linux/kexec.h>
 #include <linux/workqueue.h>
 #include <linux/device.h>
 #include <linux/times.h>
@@ -225,6 +227,7 @@
 cond_syscall(sys_lookup_dcookie)
 cond_syscall(sys_swapon)
 cond_syscall(sys_swapoff)
+cond_syscall(sys_kexec_load)
 cond_syscall(sys_init_module)
 cond_syscall(sys_delete_module)
 cond_syscall(sys_socketpair)
@@ -510,6 +513,24 @@
 		machine_restart(buffer);
 		break;
 
+#ifdef CONFIG_KEXEC
+	case LINUX_REBOOT_CMD_KEXEC:
+	{
+		struct kimage *image;
+		image = xchg(&kexec_image, 0);
+		if (!image) {
+			unlock_kernel();
+			return -EINVAL;
+		}
+		notifier_call_chain(&reboot_notifier_list, SYS_RESTART, NULL);
+		system_state = SYSTEM_BOOTING;
+		device_shutdown();
+		printk(KERN_EMERG "Starting new kernel\n");
+		machine_shutdown();
+		machine_kexec(image);
+		break;
+	}
+#endif
 #ifdef CONFIG_SOFTWARE_SUSPEND
 	case LINUX_REBOOT_CMD_SW_SUSPEND:
 		{
-
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