/*
   * kexec.c - kexec system call
   * Copyright (C) 2002-2004 Eric Biederman  <ebiederm@xmission.com>
   *
   * This source code is licensed under the GNU General Public License,
   * Version 2.  See the file COPYING for more details.
   */

  #include <linux/capability.h>

  #include <linux/mm.h>
  #include <linux/file.h>
  #include <linux/slab.h>
  #include <linux/fs.h>
  #include <linux/kexec.h>

  #include <linux/mutex.h>

  #include <linux/list.h>
  #include <linux/highmem.h>
  #include <linux/syscalls.h>
  #include <linux/reboot.h>

  #include <linux/ioport.h>

  #include <linux/hardirq.h>

  #include <linux/elf.h>
  #include <linux/elfcore.h>

  #include <generated/utsrelease.h>

  #include <linux/utsname.h>
  #include <linux/numa.h>

  #include <linux/suspend.h>
  #include <linux/device.h>

  #include <linux/freezer.h>
  #include <linux/pm.h>
  #include <linux/cpu.h>
  #include <linux/console.h>

  #include <linux/vmalloc.h>

  #include <linux/swap.h>

  #include <linux/kmsg_dump.h>

  #include <asm/page.h>
  #include <asm/uaccess.h>
  #include <asm/io.h>
  #include <asm/system.h>

  #include <asm/sections.h>

  /* Per cpu memory for storing cpu states in case of system crash. */

  note_buf_t __percpu *crash_notes;

  /* vmcoreinfo stuff */

  static unsigned char vmcoreinfo_data[VMCOREINFO_BYTES];

  u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];

  size_t vmcoreinfo_size;
  size_t vmcoreinfo_max_size = sizeof(vmcoreinfo_data);

  /* Location of the reserved area for the crash kernel */
  struct resource crashk_res = {
  	.name  = "Crash kernel",
  	.start = 0,
  	.end   = 0,
  	.flags = IORESOURCE_BUSY | IORESOURCE_MEM
  };

  int kexec_should_crash(struct task_struct *p)
  {

  	if (in_interrupt() || !p->pid || is_global_init(p) || panic_on_oops)

  		return 1;
  	return 0;
  }

  /*
   * 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_PAGE_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,

  				       gfp_t gfp_mask,

  				       unsigned long dest);

  
  static int do_kimage_alloc(struct kimage **rimage, unsigned long entry,

  	                    unsigned long nr_segments,
                              struct kexec_segment __user *segments)

  {
  	size_t segment_bytes;
  	struct kimage *image;
  	unsigned long i;
  	int result;
  
  	/* Allocate a controlling structure */
  	result = -ENOMEM;

  	image = kzalloc(sizeof(*image), GFP_KERNEL);

  	if (!image)

  		goto out;

  	image->head = 0;
  	image->entry = &image->head;
  	image->last_entry = &image->head;
  	image->control_page = ~0; /* By default this does not apply */
  	image->start = entry;
  	image->type = KEXEC_TYPE_DEFAULT;
  
  	/* 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) {
  		result = -EFAULT;

  		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.
  	 *
  	 * Since the kernel does everything in page size chunks ensure

  	 * the destination addresses are page aligned.  Too many

  	 * special cases crop of when we don't do this.  The most
  	 * insidious is getting overlapping destination addresses
  	 * simply because addresses are changed to page size
  	 * granularity.
  	 */
  	result = -EADDRNOTAVAIL;
  	for (i = 0; i < nr_segments; i++) {
  		unsigned long mstart, mend;

  		mstart = image->segment[i].mem;
  		mend   = mstart + image->segment[i].memsz;
  		if ((mstart & ~PAGE_MASK) || (mend & ~PAGE_MASK))
  			goto out;
  		if (mend >= KEXEC_DESTINATION_MEMORY_LIMIT)
  			goto out;
  	}
  
  	/* Verify our destination addresses do not overlap.
  	 * If we alloed overlapping destination addresses
  	 * through very weird things can happen with no
  	 * easy explanation as one segment stops on another.
  	 */
  	result = -EINVAL;

  	for (i = 0; i < nr_segments; i++) {

  		unsigned long mstart, mend;
  		unsigned long j;

  		mstart = image->segment[i].mem;
  		mend   = mstart + image->segment[i].memsz;

  		for (j = 0; j < i; j++) {

  			unsigned long pstart, pend;
  			pstart = image->segment[j].mem;
  			pend   = pstart + image->segment[j].memsz;
  			/* Do the segments overlap ? */
  			if ((mend > pstart) && (mstart < pend))
  				goto out;
  		}
  	}
  
  	/* Ensure our buffer sizes are strictly less than
  	 * our memory sizes.  This should always be the case,
  	 * and it is easier to check up front than to be surprised
  	 * later on.
  	 */
  	result = -EINVAL;

  	for (i = 0; i < nr_segments; i++) {

  		if (image->segment[i].bufsz > image->segment[i].memsz)
  			goto out;
  	}

  	result = 0;

  out:
  	if (result == 0)

  		*rimage = image;

  	else

  		kfree(image);

  	return result;
  
  }
  
  static int kimage_normal_alloc(struct kimage **rimage, unsigned long entry,

  				unsigned long nr_segments,
  				struct kexec_segment __user *segments)

  {
  	int result;
  	struct kimage *image;
  
  	/* Allocate and initialize a controlling structure */
  	image = NULL;
  	result = do_kimage_alloc(&image, entry, nr_segments, segments);

  	if (result)

  		goto out;

  	*rimage = image;
  
  	/*
  	 * 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_PAGE_SIZE));

  	if (!image->control_code_page) {
  		printk(KERN_ERR "Could not allocate control_code_buffer
  ");
  		goto out;
  	}

  	image->swap_page = kimage_alloc_control_pages(image, 0);
  	if (!image->swap_page) {
  		printk(KERN_ERR "Could not allocate swap buffer
  ");
  		goto out;
  	}

  	result = 0;
   out:

  	if (result == 0)

  		*rimage = image;

  	else

  		kfree(image);

  	return result;
  }
  
  static int kimage_crash_alloc(struct kimage **rimage, unsigned long entry,

  				unsigned long nr_segments,

  				struct kexec_segment __user *segments)

  {
  	int result;
  	struct kimage *image;
  	unsigned long i;
  
  	image = NULL;
  	/* Verify we have a valid entry point */
  	if ((entry < crashk_res.start) || (entry > crashk_res.end)) {
  		result = -EADDRNOTAVAIL;
  		goto out;
  	}
  
  	/* Allocate and initialize a controlling structure */
  	result = do_kimage_alloc(&image, entry, nr_segments, segments);

  	if (result)

  		goto out;

  
  	/* Enable the special crash kernel control page
  	 * allocation policy.
  	 */
  	image->control_page = crashk_res.start;
  	image->type = KEXEC_TYPE_CRASH;
  
  	/*
  	 * Verify we have good destination addresses.  Normally
  	 * the caller is responsible for making certain we don't
  	 * attempt to load the new image into invalid or reserved
  	 * areas of RAM.  But crash kernels are preloaded into a
  	 * reserved area of ram.  We must ensure the addresses
  	 * are in the reserved area otherwise preloading the
  	 * kernel could corrupt things.
  	 */
  	result = -EADDRNOTAVAIL;
  	for (i = 0; i < nr_segments; i++) {
  		unsigned long mstart, mend;

  		mstart = image->segment[i].mem;

  		mend = mstart + image->segment[i].memsz - 1;

  		/* Ensure we are within the crash kernel limits */
  		if ((mstart < crashk_res.start) || (mend > crashk_res.end))
  			goto out;
  	}

  	/*
  	 * Find a location for the control code buffer, and add
  	 * 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_PAGE_SIZE));

  	if (!image->control_code_page) {
  		printk(KERN_ERR "Could not allocate control_code_buffer
  ");
  		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 = 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(gfp_t gfp_mask, unsigned int order)

  {
  	struct page *pages;

  	pages = alloc_pages(gfp_mask, order);
  	if (pages) {
  		unsigned int count, i;
  		pages->mapping = NULL;

  		set_page_private(pages, 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(page);

  	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);
  	}
  }

  static struct page *kimage_alloc_normal_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 struct page *kimage_alloc_crash_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.
  	 *
  	 * Control pages are also the only pags we must allocate
  	 * when loading a crash kernel.  All of the other pages
  	 * are specified by the segments and we just memcpy
  	 * into them directly.
  	 *
  	 * 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.
  	 *
  	 * Given the low demand this implements a very simple
  	 * allocator that finds the first hole of the appropriate
  	 * size in the reserved memory region, and allocates all
  	 * of the memory up to and including the hole.
  	 */
  	unsigned long hole_start, hole_end, size;
  	struct page *pages;

  	pages = NULL;
  	size = (1 << order) << PAGE_SHIFT;
  	hole_start = (image->control_page + (size - 1)) & ~(size - 1);
  	hole_end   = hole_start + size - 1;

  	while (hole_end <= crashk_res.end) {

  		unsigned long i;

  
  		if (hole_end > KEXEC_CONTROL_MEMORY_LIMIT)

  			break;

  		if (hole_end > crashk_res.end)

  			break;

  		/* See if I overlap any of the segments */

  		for (i = 0; i < image->nr_segments; i++) {

  			unsigned long mstart, mend;

  			mstart = image->segment[i].mem;
  			mend   = mstart + image->segment[i].memsz - 1;
  			if ((hole_end >= mstart) && (hole_start <= mend)) {
  				/* Advance the hole to the end of the segment */
  				hole_start = (mend + (size - 1)) & ~(size - 1);
  				hole_end   = hole_start + size - 1;
  				break;
  			}
  		}
  		/* If I don't overlap any segments I have found my hole! */
  		if (i == image->nr_segments) {
  			pages = pfn_to_page(hole_start >> PAGE_SHIFT);
  			break;
  		}
  	}

  	if (pages)

  		image->control_page = hole_end;

  	return pages;
  }

  struct page *kimage_alloc_control_pages(struct kimage *image,
  					 unsigned int order)

  {
  	struct page *pages = NULL;

  
  	switch (image->type) {

  	case KEXEC_TYPE_DEFAULT:
  		pages = kimage_alloc_normal_control_pages(image, order);
  		break;
  	case KEXEC_TYPE_CRASH:
  		pages = kimage_alloc_crash_control_pages(image, order);
  		break;
  	}

  	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 void kimage_terminate(struct kimage *image)

  {

  	if (*image->entry != 0)

  		image->entry++;

  	*image->entry = IND_DONE;

  }
  
  #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 NULL;

  }

  static struct page *kimage_alloc_page(struct kimage *image,

  					gfp_t 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 NULL;

  		/* 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 if it's
  			 * gfp_flags honor the ones passed in.

  			 */

  			if (!(gfp_mask & __GFP_HIGHMEM) &&
  			    PageHighMem(old_page)) {
  				kimage_free_pages(old_page);
  				continue;
  			}

  			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_normal_segment(struct kimage *image,

  					 struct kexec_segment *segment)

  {
  	unsigned long maddr;
  	unsigned long ubytes, mbytes;
  	int result;

  	unsigned char __user *buf;

  
  	result = 0;
  	buf = segment->buf;
  	ubytes = segment->bufsz;
  	mbytes = segment->memsz;
  	maddr = segment->mem;
  
  	result = kimage_set_destination(image, maddr);

  	if (result < 0)

  		goto out;

  
  	while (mbytes) {

  		struct page *page;
  		char *ptr;
  		size_t uchunk, mchunk;

  		page = kimage_alloc_page(image, GFP_HIGHUSER, maddr);

  		if (!page) {

  			result  = -ENOMEM;
  			goto out;
  		}

  		result = kimage_add_page(image, page_to_pfn(page)
  								<< PAGE_SHIFT);
  		if (result < 0)

  			goto out;

  		ptr = kmap(page);
  		/* Start with a clear page */

  		clear_page(ptr);

  		ptr += maddr & ~PAGE_MASK;
  		mchunk = PAGE_SIZE - (maddr & ~PAGE_MASK);

  		if (mchunk > mbytes)

  			mchunk = mbytes;

  		uchunk = mchunk;

  		if (uchunk > ubytes)

  			uchunk = ubytes;

  		result = copy_from_user(ptr, buf, uchunk);
  		kunmap(page);
  		if (result) {

  			result = -EFAULT;

  			goto out;
  		}
  		ubytes -= uchunk;
  		maddr  += mchunk;
  		buf    += mchunk;
  		mbytes -= mchunk;
  	}

  out:

  	return result;
  }
  
  static int kimage_load_crash_segment(struct kimage *image,

  					struct kexec_segment *segment)

  {
  	/* For crash dumps kernels we simply copy the data from
  	 * user space to it's destination.
  	 * We do things a page at a time for the sake of kmap.
  	 */
  	unsigned long maddr;
  	unsigned long ubytes, mbytes;
  	int result;

  	unsigned char __user *buf;

  
  	result = 0;
  	buf = segment->buf;
  	ubytes = segment->bufsz;
  	mbytes = segment->memsz;
  	maddr = segment->mem;

  	while (mbytes) {

  		struct page *page;
  		char *ptr;
  		size_t uchunk, mchunk;

  		page = pfn_to_page(maddr >> PAGE_SHIFT);

  		if (!page) {

  			result  = -ENOMEM;
  			goto out;
  		}
  		ptr = kmap(page);
  		ptr += maddr & ~PAGE_MASK;
  		mchunk = PAGE_SIZE - (maddr & ~PAGE_MASK);

  		if (mchunk > mbytes)

  			mchunk = mbytes;

  		uchunk = mchunk;
  		if (uchunk > ubytes) {
  			uchunk = ubytes;
  			/* Zero the trailing part of the page */
  			memset(ptr + uchunk, 0, mchunk - uchunk);
  		}
  		result = copy_from_user(ptr, buf, uchunk);

  		kexec_flush_icache_page(page);

  		kunmap(page);
  		if (result) {

  			result = -EFAULT;

  			goto out;
  		}
  		ubytes -= uchunk;
  		maddr  += mchunk;
  		buf    += mchunk;
  		mbytes -= mchunk;
  	}

  out:

  	return result;
  }
  
  static int kimage_load_segment(struct kimage *image,

  				struct kexec_segment *segment)

  {
  	int result = -ENOMEM;

  
  	switch (image->type) {

  	case KEXEC_TYPE_DEFAULT:
  		result = kimage_load_normal_segment(image, segment);
  		break;
  	case KEXEC_TYPE_CRASH:
  		result = kimage_load_crash_segment(image, segment);
  		break;
  	}

  	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;
  struct kimage *kexec_crash_image;

  
  static DEFINE_MUTEX(kexec_mutex);

  SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
  		struct kexec_segment __user *, segments, unsigned long, flags)

  {
  	struct kimage **dest_image, *image;

  	int result;
  
  	/* We only trust the superuser with rebooting the system. */
  	if (!capable(CAP_SYS_BOOT))
  		return -EPERM;
  
  	/*
  	 * Verify we have a legal set of flags
  	 * This leaves us room for future extensions.
  	 */
  	if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
  		return -EINVAL;
  
  	/* Verify we are on the appropriate architecture */
  	if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) &&
  		((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT))

  		return -EINVAL;

  
  	/* Put an artificial cap on the number
  	 * of segments passed to kexec_load.
  	 */
  	if (nr_segments > KEXEC_SEGMENT_MAX)
  		return -EINVAL;
  
  	image = NULL;
  	result = 0;
  
  	/* Because we write directly to the reserved memory
  	 * region when loading crash kernels we need a mutex here to
  	 * prevent multiple crash  kernels from attempting to load
  	 * simultaneously, and to prevent a crash kernel from loading
  	 * over the top of a in use crash kernel.
  	 *
  	 * KISS: always take the mutex.
  	 */

  	if (!mutex_trylock(&kexec_mutex))

  		return -EBUSY;

  	dest_image = &kexec_image;

  	if (flags & KEXEC_ON_CRASH)

  		dest_image = &kexec_crash_image;

  	if (nr_segments > 0) {
  		unsigned long i;

  		/* Loading another kernel to reboot into */

  		if ((flags & KEXEC_ON_CRASH) == 0)
  			result = kimage_normal_alloc(&image, entry,
  							nr_segments, segments);

  		/* Loading another kernel to switch to if this one crashes */
  		else if (flags & KEXEC_ON_CRASH) {
  			/* Free any current crash dump kernel before
  			 * we corrupt it.
  			 */
  			kimage_free(xchg(&kexec_crash_image, NULL));

  			result = kimage_crash_alloc(&image, entry,
  						     nr_segments, segments);

  		}

  		if (result)

  			goto out;

  		if (flags & KEXEC_PRESERVE_CONTEXT)
  			image->preserve_context = 1;

  		result = machine_kexec_prepare(image);

  		if (result)

  			goto out;

  
  		for (i = 0; i < nr_segments; i++) {

  			result = kimage_load_segment(image, &image->segment[i]);

  			if (result)

  				goto out;

  		}

  		kimage_terminate(image);

  	}
  	/* Install the new kernel, and  Uninstall the old */
  	image = xchg(dest_image, image);

  out:

  	mutex_unlock(&kexec_mutex);

  	kimage_free(image);

  	return result;
  }
  
  #ifdef CONFIG_COMPAT
  asmlinkage long compat_sys_kexec_load(unsigned long entry,

  				unsigned long nr_segments,
  				struct compat_kexec_segment __user *segments,
  				unsigned long flags)

  {
  	struct compat_kexec_segment in;
  	struct kexec_segment out, __user *ksegments;
  	unsigned long i, result;
  
  	/* Don't allow clients that don't understand the native
  	 * architecture to do anything.
  	 */

  	if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)

  		return -EINVAL;

  	if (nr_segments > KEXEC_SEGMENT_MAX)

  		return -EINVAL;

  
  	ksegments = compat_alloc_user_space(nr_segments * sizeof(out));
  	for (i=0; i < nr_segments; i++) {
  		result = copy_from_user(&in, &segments[i], sizeof(in));

  		if (result)

  			return -EFAULT;

  
  		out.buf   = compat_ptr(in.buf);
  		out.bufsz = in.bufsz;
  		out.mem   = in.mem;
  		out.memsz = in.memsz;
  
  		result = copy_to_user(&ksegments[i], &out, sizeof(out));

  		if (result)

  			return -EFAULT;

  	}
  
  	return sys_kexec_load(entry, nr_segments, ksegments, flags);
  }
  #endif

  void crash_kexec(struct pt_regs *regs)

  {

  	/* Take the kexec_mutex here to prevent sys_kexec_load

  	 * running on one cpu from replacing the crash kernel
  	 * we are using after a panic on a different cpu.
  	 *
  	 * If the crash kernel was not located in a fixed area
  	 * of memory the xchg(&kexec_crash_image) would be
  	 * sufficient.  But since I reuse the memory...
  	 */

  	if (mutex_trylock(&kexec_mutex)) {

  		if (kexec_crash_image) {

  			struct pt_regs fixed_regs;

  
  			kmsg_dump(KMSG_DUMP_KEXEC);

  			crash_setup_regs(&fixed_regs, regs);

  			crash_save_vmcoreinfo();

  			machine_crash_shutdown(&fixed_regs);

  			machine_kexec(kexec_crash_image);

  		}

  		mutex_unlock(&kexec_mutex);

  	}
  }

  size_t crash_get_memory_size(void)
  {

  	size_t size = 0;

  	mutex_lock(&kexec_mutex);

  	if (crashk_res.end != crashk_res.start)
  		size = crashk_res.end - crashk_res.start + 1;

  	mutex_unlock(&kexec_mutex);
  	return size;
  }
  
  static void free_reserved_phys_range(unsigned long begin, unsigned long end)
  {
  	unsigned long addr;
  
  	for (addr = begin; addr < end; addr += PAGE_SIZE) {
  		ClearPageReserved(pfn_to_page(addr >> PAGE_SHIFT));
  		init_page_count(pfn_to_page(addr >> PAGE_SHIFT));
  		free_page((unsigned long)__va(addr));
  		totalram_pages++;
  	}
  }
  
  int crash_shrink_memory(unsigned long new_size)
  {
  	int ret = 0;
  	unsigned long start, end;
  
  	mutex_lock(&kexec_mutex);
  
  	if (kexec_crash_image) {
  		ret = -ENOENT;
  		goto unlock;
  	}
  	start = crashk_res.start;
  	end = crashk_res.end;
  
  	if (new_size >= end - start + 1) {
  		ret = -EINVAL;
  		if (new_size == end - start + 1)
  			ret = 0;
  		goto unlock;
  	}
  
  	start = roundup(start, PAGE_SIZE);
  	end = roundup(start + new_size, PAGE_SIZE);
  
  	free_reserved_phys_range(end, crashk_res.end);

  	if ((start == end) && (crashk_res.parent != NULL))

  		release_resource(&crashk_res);

  	crashk_res.end = end - 1;

  
  unlock:
  	mutex_unlock(&kexec_mutex);
  	return ret;
  }

  static u32 *append_elf_note(u32 *buf, char *name, unsigned type, void *data,
  			    size_t data_len)
  {
  	struct elf_note note;
  
  	note.n_namesz = strlen(name) + 1;
  	note.n_descsz = data_len;
  	note.n_type   = type;
  	memcpy(buf, &note, sizeof(note));
  	buf += (sizeof(note) + 3)/4;
  	memcpy(buf, name, note.n_namesz);
  	buf += (note.n_namesz + 3)/4;
  	memcpy(buf, data, note.n_descsz);
  	buf += (note.n_descsz + 3)/4;
  
  	return buf;
  }
  
  static void final_note(u32 *buf)
  {
  	struct elf_note note;
  
  	note.n_namesz = 0;
  	note.n_descsz = 0;
  	note.n_type   = 0;
  	memcpy(buf, &note, sizeof(note));
  }
  
  void crash_save_cpu(struct pt_regs *regs, int cpu)
  {
  	struct elf_prstatus prstatus;
  	u32 *buf;

  	if ((cpu < 0) || (cpu >= nr_cpu_ids))

  		return;
  
  	/* Using ELF notes here is opportunistic.
  	 * I need a well defined structure format
  	 * for the data I pass, and I need tags
  	 * on the data to indicate what information I have
  	 * squirrelled away.  ELF notes happen to provide
  	 * all of that, so there is no need to invent something new.
  	 */
  	buf = (u32*)per_cpu_ptr(crash_notes, cpu);
  	if (!buf)
  		return;
  	memset(&prstatus, 0, sizeof(prstatus));
  	prstatus.pr_pid = current->pid;

  	elf_core_copy_kernel_regs(&prstatus.pr_reg, regs);

  	buf = append_elf_note(buf, KEXEC_CORE_NOTE_NAME, NT_PRSTATUS,
  		      	      &prstatus, sizeof(prstatus));

  	final_note(buf);
  }

  static int __init crash_notes_memory_init(void)
  {
  	/* Allocate memory for saving cpu registers. */
  	crash_notes = alloc_percpu(note_buf_t);
  	if (!crash_notes) {
  		printk("Kexec: Memory allocation for saving cpu register"
  		" states failed
  ");
  		return -ENOMEM;
  	}
  	return 0;
  }
  module_init(crash_notes_memory_init)

  
  /*
   * parsing the "crashkernel" commandline
   *
   * this code is intended to be called from architecture specific code
   */
  
  
  /*
   * This function parses command lines in the format
   *
   *   crashkernel=ramsize-range:size[,...][@offset]
   *
   * The function returns 0 on success and -EINVAL on failure.
   */
  static int __init parse_crashkernel_mem(char 			*cmdline,
  					unsigned long long	system_ram,
  					unsigned long long	*crash_size,
  					unsigned long long	*crash_base)
  {
  	char *cur = cmdline, *tmp;
  
  	/* for each entry of the comma-separated list */
  	do {
  		unsigned long long start, end = ULLONG_MAX, size;
  
  		/* get the start of the range */
  		start = memparse(cur, &tmp);
  		if (cur == tmp) {
  			pr_warning("crashkernel: Memory value expected
  ");
  			return -EINVAL;
  		}
  		cur = tmp;
  		if (*cur != '-') {
  			pr_warning("crashkernel: '-' expected
  ");
  			return -EINVAL;
  		}
  		cur++;
  
  		/* if no ':' is here, than we read the end */
  		if (*cur != ':') {
  			end = memparse(cur, &tmp);
  			if (cur == tmp) {
  				pr_warning("crashkernel: Memory "
  						"value expected
  ");
  				return -EINVAL;
  			}
  			cur = tmp;
  			if (end <= start) {
  				pr_warning("crashkernel: end <= start
  ");
  				return -EINVAL;
  			}
  		}
  
  		if (*cur != ':') {
  			pr_warning("crashkernel: ':' expected
  ");
  			return -EINVAL;
  		}
  		cur++;
  
  		size = memparse(cur, &tmp);
  		if (cur == tmp) {
  			pr_warning("Memory value expected
  ");
  			return -EINVAL;
  		}
  		cur = tmp;
  		if (size >= system_ram) {
  			pr_warning("crashkernel: invalid size
  ");
  			return -EINVAL;
  		}
  
  		/* match ? */

  		if (system_ram >= start && system_ram < end) {

  			*crash_size = size;
  			break;
  		}
  	} while (*cur++ == ',');
  
  	if (*crash_size > 0) {

  		while (*cur && *cur != ' ' && *cur != '@')

  			cur++;
  		if (*cur == '@') {
  			cur++;
  			*crash_base = memparse(cur, &tmp);
  			if (cur == tmp) {
  				pr_warning("Memory value expected "
  						"after '@'
  ");
  				return -EINVAL;
  			}
  		}
  	}
  
  	return 0;
  }
  
  /*
   * That function parses "simple" (old) crashkernel command lines like
   *
   * 	crashkernel=size[@offset]
   *
   * It returns 0 on success and -EINVAL on failure.
   */
  static int __init parse_crashkernel_simple(char 		*cmdline,
  					   unsigned long long 	*crash_size,
  					   unsigned long long 	*crash_base)
  {
  	char *cur = cmdline;
  
  	*crash_size = memparse(cmdline, &cur);
  	if (cmdline == cur) {
  		pr_warning("crashkernel: memory value expected
  ");
  		return -EINVAL;
  	}
  
  	if (*cur == '@')
  		*crash_base = memparse(cur+1, &cur);
  
  	return 0;
  }
  
  /*
   * That function is the entry point for command line parsing and should be
   * called from the arch-specific code.
   */
  int __init parse_crashkernel(char 		 *cmdline,
  			     unsigned long long system_ram,
  			     unsigned long long *crash_size,
  			     unsigned long long *crash_base)
  {
  	char 	*p = cmdline, *ck_cmdline = NULL;
  	char	*first_colon, *first_space;
  
  	BUG_ON(!crash_size || !crash_base);
  	*crash_size = 0;
  	*crash_base = 0;
  
  	/* find crashkernel and use the last one if there are more */
  	p = strstr(p, "crashkernel=");
  	while (p) {
  		ck_cmdline = p;
  		p = strstr(p+1, "crashkernel=");
  	}
  
  	if (!ck_cmdline)
  		return -EINVAL;
  
  	ck_cmdline += 12; /* strlen("crashkernel=") */
  
  	/*
  	 * if the commandline contains a ':', then that's the extended
  	 * syntax -- if not, it must be the classic syntax
  	 */
  	first_colon = strchr(ck_cmdline, ':');
  	first_space = strchr(ck_cmdline, ' ');
  	if (first_colon && (!first_space || first_colon < first_space))
  		return parse_crashkernel_mem(ck_cmdline, system_ram,
  				crash_size, crash_base);
  	else
  		return parse_crashkernel_simple(ck_cmdline, crash_size,
  				crash_base);
  
  	return 0;
  }

  void crash_save_vmcoreinfo(void)
  {
  	u32 *buf;
  
  	if (!vmcoreinfo_size)
  		return;

  	vmcoreinfo_append_str("CRASHTIME=%ld", get_seconds());

  
  	buf = (u32 *)vmcoreinfo_note;
  
  	buf = append_elf_note(buf, VMCOREINFO_NOTE_NAME, 0, vmcoreinfo_data,
  			      vmcoreinfo_size);
  
  	final_note(buf);
  }
  
  void vmcoreinfo_append_str(const char *fmt, ...)
  {
  	va_list args;
  	char buf[0x50];
  	int r;
  
  	va_start(args, fmt);
  	r = vsnprintf(buf, sizeof(buf), fmt, args);
  	va_end(args);
  
  	if (r + vmcoreinfo_size > vmcoreinfo_max_size)
  		r = vmcoreinfo_max_size - vmcoreinfo_size;
  
  	memcpy(&vmcoreinfo_data[vmcoreinfo_size], buf, r);
  
  	vmcoreinfo_size += r;
  }
  
  /*
   * provide an empty default implementation here -- architecture
   * code may override this
   */
  void __attribute__ ((weak)) arch_crash_save_vmcoreinfo(void)
  {}
  
  unsigned long __attribute__ ((weak)) paddr_vmcoreinfo_note(void)
  {
  	return __pa((unsigned long)(char *)&vmcoreinfo_note);
  }
  
  static int __init crash_save_vmcoreinfo_init(void)
  {

  	VMCOREINFO_OSRELEASE(init_uts_ns.name.release);
  	VMCOREINFO_PAGESIZE(PAGE_SIZE);

  	VMCOREINFO_SYMBOL(init_uts_ns);
  	VMCOREINFO_SYMBOL(node_online_map);
  	VMCOREINFO_SYMBOL(swapper_pg_dir);
  	VMCOREINFO_SYMBOL(_stext);

  	VMCOREINFO_SYMBOL(vmlist);

  
  #ifndef CONFIG_NEED_MULTIPLE_NODES

  	VMCOREINFO_SYMBOL(mem_map);
  	VMCOREINFO_SYMBOL(contig_page_data);

  #endif
  #ifdef CONFIG_SPARSEMEM

  	VMCOREINFO_SYMBOL(mem_section);
  	VMCOREINFO_LENGTH(mem_section, NR_SECTION_ROOTS);

  	VMCOREINFO_STRUCT_SIZE(mem_section);

  	VMCOREINFO_OFFSET(mem_section, section_mem_map);

  #endif

  	VMCOREINFO_STRUCT_SIZE(page);
  	VMCOREINFO_STRUCT_SIZE(pglist_data);
  	VMCOREINFO_STRUCT_SIZE(zone);
  	VMCOREINFO_STRUCT_SIZE(free_area);
  	VMCOREINFO_STRUCT_SIZE(list_head);
  	VMCOREINFO_SIZE(nodemask_t);

  	VMCOREINFO_OFFSET(page, flags);
  	VMCOREINFO_OFFSET(page, _count);
  	VMCOREINFO_OFFSET(page, mapping);
  	VMCOREINFO_OFFSET(page, lru);
  	VMCOREINFO_OFFSET(pglist_data, node_zones);
  	VMCOREINFO_OFFSET(pglist_data, nr_zones);

  #ifdef CONFIG_FLAT_NODE_MEM_MAP

  	VMCOREINFO_OFFSET(pglist_data, node_mem_map);

  #endif

  	VMCOREINFO_OFFSET(pglist_data, node_start_pfn);
  	VMCOREINFO_OFFSET(pglist_data, node_spanned_pages);
  	VMCOREINFO_OFFSET(pglist_data, node_id);
  	VMCOREINFO_OFFSET(zone, free_area);
  	VMCOREINFO_OFFSET(zone, vm_stat);
  	VMCOREINFO_OFFSET(zone, spanned_pages);
  	VMCOREINFO_OFFSET(free_area, free_list);
  	VMCOREINFO_OFFSET(list_head, next);
  	VMCOREINFO_OFFSET(list_head, prev);

  	VMCOREINFO_OFFSET(vm_struct, addr);

  	VMCOREINFO_LENGTH(zone.free_area, MAX_ORDER);

  	log_buf_kexec_setup();

  	VMCOREINFO_LENGTH(free_area.free_list, MIGRATE_TYPES);

  	VMCOREINFO_NUMBER(NR_FREE_PAGES);

  	VMCOREINFO_NUMBER(PG_lru);
  	VMCOREINFO_NUMBER(PG_private);
  	VMCOREINFO_NUMBER(PG_swapcache);

  
  	arch_crash_save_vmcoreinfo();
  
  	return 0;
  }
  
  module_init(crash_save_vmcoreinfo_init)

  /*
   * Move into place and start executing a preloaded standalone
   * executable.  If nothing was preloaded return an error.

   */
  int kernel_kexec(void)
  {
  	int error = 0;

  	if (!mutex_trylock(&kexec_mutex))

  		return -EBUSY;
  	if (!kexec_image) {
  		error = -EINVAL;
  		goto Unlock;
  	}

  #ifdef CONFIG_KEXEC_JUMP

  	if (kexec_image->preserve_context) {

  		mutex_lock(&pm_mutex);
  		pm_prepare_console();
  		error = freeze_processes();
  		if (error) {
  			error = -EBUSY;
  			goto Restore_console;
  		}
  		suspend_console();

  		error = dpm_suspend_start(PMSG_FREEZE);

  		if (error)
  			goto Resume_console;

  		/* At this point, dpm_suspend_start() has been called,
  		 * but *not* dpm_suspend_noirq(). We *must* call
  		 * dpm_suspend_noirq() now.  Otherwise, drivers for

  		 * some devices (e.g. interrupt controllers) become
  		 * desynchronized with the actual state of the
  		 * hardware at resume time, and evil weirdness ensues.
  		 */

  		error = dpm_suspend_noirq(PMSG_FREEZE);

  		if (error)

  			goto Resume_devices;
  		error = disable_nonboot_cpus();
  		if (error)
  			goto Enable_cpus;

  		local_irq_disable();

  		/* Suspend system devices */
  		error = sysdev_suspend(PMSG_FREEZE);
  		if (error)

  			goto Enable_irqs;

  	} else

  #endif

  	{

  		kernel_restart_prepare(NULL);

  		printk(KERN_EMERG "Starting new kernel
  ");
  		machine_shutdown();
  	}
  
  	machine_kexec(kexec_image);

  #ifdef CONFIG_KEXEC_JUMP

  	if (kexec_image->preserve_context) {

  		sysdev_resume();

   Enable_irqs:

  		local_irq_enable();

   Enable_cpus:

  		enable_nonboot_cpus();

  		dpm_resume_noirq(PMSG_RESTORE);

   Resume_devices:

  		dpm_resume_end(PMSG_RESTORE);

   Resume_console:
  		resume_console();
  		thaw_processes();
   Restore_console:
  		pm_restore_console();
  		mutex_unlock(&pm_mutex);

  	}

  #endif

  
   Unlock:

  	mutex_unlock(&kexec_mutex);

  	return error;
  }