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kexec.c

/*
 * 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/spinlock.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 <linux/utsrelease.h>
#include <linux/utsname.h>
#include <linux/numa.h>

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

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

/* vmcoreinfo stuff */
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_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,
                               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)
            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 addreses 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_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_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_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 = 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 int kimage_terminate(struct kimage *image)
{
      if (*image->entry != 0)
            image->entry++;

      *image->entry = IND_DONE;

      return 0;
}

#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.
                   */
                  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 */
            memset(ptr, 0, PAGE_SIZE);
            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 = (result < 0) ? result : -EIO;
                  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 = (result < 0) ? result : -EIO;
                  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;
/*
 * A home grown binary mutex.
 * Nothing can wait so this mutex is safe to use
 * in interrupt context :)
 */
static int kexec_lock;

asmlinkage long sys_kexec_load(unsigned long entry, unsigned long nr_segments,
                        struct kexec_segment __user *segments,
                        unsigned long flags)
{
      struct kimage **dest_image, *image;
      int locked;
      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.
       */
      locked = xchg(&kexec_lock, 1);
      if (locked)
            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;

            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;
            }
            result = kimage_terminate(image);
            if (result)
                  goto out;
      }
      /* Install the new kernel, and  Uninstall the old */
      image = xchg(dest_image, image);

out:
      locked = xchg(&kexec_lock, 0); /* Release the mutex */
      BUG_ON(!locked);
      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)
{
      int locked;


      /* Take the kexec_lock 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...
       */
      locked = xchg(&kexec_lock, 1);
      if (!locked) {
            if (kexec_crash_image) {
                  struct pt_regs fixed_regs;
                  crash_setup_regs(&fixed_regs, regs);
                  crash_save_vmcoreinfo();
                  machine_crash_shutdown(&fixed_regs);
                  machine_kexec(kexec_crash_image);
            }
            locked = xchg(&kexec_lock, 0);
            BUG_ON(!locked);
      }
}

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_CPUS))
            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_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\n");
            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\n");
                  return -EINVAL;
            }
            cur = tmp;
            if (*cur != '-') {
                  pr_warning("crashkernel: '-' expected\n");
                  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\n");
                        return -EINVAL;
                  }
                  cur = tmp;
                  if (end <= start) {
                        pr_warning("crashkernel: end <= start\n");
                        return -EINVAL;
                  }
            }

            if (*cur != ':') {
                  pr_warning("crashkernel: ':' expected\n");
                  return -EINVAL;
            }
            cur++;

            size = memparse(cur, &tmp);
            if (cur == tmp) {
                  pr_warning("Memory value expected\n");
                  return -EINVAL;
            }
            cur = tmp;
            if (size >= system_ram) {
                  pr_warning("crashkernel: invalid size\n");
                  return -EINVAL;
            }

            /* match ? */
            if (system_ram >= start && system_ram <= end) {
                  *crash_size = size;
                  break;
            }
      } while (*cur++ == ',');

      if (*crash_size > 0) {
            while (*cur != ' ' && *cur != '@')
                  cur++;
            if (*cur == '@') {
                  cur++;
                  *crash_base = memparse(cur, &tmp);
                  if (cur == tmp) {
                        pr_warning("Memory value expected "
                                    "after '@'\n");
                        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\n");
            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_append_str("OSRELEASE=%s\n", init_uts_ns.name.release);
      vmcoreinfo_append_str("PAGESIZE=%ld\n", PAGE_SIZE);

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

#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_SIZE(mem_section);
      VMCOREINFO_OFFSET(mem_section, section_mem_map);
#endif
      VMCOREINFO_SIZE(page);
      VMCOREINFO_SIZE(pglist_data);
      VMCOREINFO_SIZE(zone);
      VMCOREINFO_SIZE(free_area);
      VMCOREINFO_SIZE(list_head);
      VMCOREINFO_TYPEDEF_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_LENGTH(zone.free_area, MAX_ORDER);
      VMCOREINFO_LENGTH(free_area.free_list, MIGRATE_TYPES);
      VMCOREINFO_NUMBER(NR_FREE_PAGES);

      arch_crash_save_vmcoreinfo();

      return 0;
}

module_init(crash_save_vmcoreinfo_init)

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