FreeBSD/Linux Kernel Cross Reference
sys/kernel/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/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 <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/syscore_ops.h>
    
    #include <asm/page.h>
    #include <asm/uaccess.h>
    #include <asm/io.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 unusable 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\n");
                   goto out;
           }
   
           image->swap_page = kimage_alloc_control_pages(image, 0);
           if (!image->swap_page) {
                   printk(KERN_ERR "Could not allocate swap 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_PAGE_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 everything 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_CRASH_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 unusable 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);
                           crash_map_reserved_pages();
                  }
                  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);
                  if (flags & KEXEC_ON_CRASH)
                          crash_unmap_reserved_pages();
          }
          /* Install the new kernel, and  Uninstall the old */
          image = xchg(dest_image, image);
  
  out:
          mutex_unlock(&kexec_mutex);
          kimage_free(image);
  
          return result;
  }
  
  /*
   * Add and remove page tables for crashkernel memory
   *
   * Provide an empty default implementation here -- architecture
   * code may override this
   */
  void __weak crash_map_reserved_pages(void)
  {}
  
  void __weak crash_unmap_reserved_pages(void)
  {}
  
  #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;
  
                          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 = resource_size(&crashk_res);
          mutex_unlock(&kexec_mutex);
          return size;
  }
  
  void __weak crash_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;
          unsigned long old_size;
          struct resource *ram_res;
  
          mutex_lock(&kexec_mutex);
  
          if (kexec_crash_image) {
                  ret = -ENOENT;
                  goto unlock;
          }
          start = crashk_res.start;
          end = crashk_res.end;
          old_size = (end == 0) ? 0 : end - start + 1;
          if (new_size >= old_size) {
                  ret = (new_size == old_size) ? 0 : -EINVAL;
                  goto unlock;
          }
  
          ram_res = kzalloc(sizeof(*ram_res), GFP_KERNEL);
          if (!ram_res) {
                  ret = -ENOMEM;
                  goto unlock;
          }
  
          start = roundup(start, KEXEC_CRASH_MEM_ALIGN);
          end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN);
  
          crash_map_reserved_pages();
          crash_free_reserved_phys_range(end, crashk_res.end);
  
          if ((start == end) && (crashk_res.parent != NULL))
                  release_resource(&crashk_res);
  
          ram_res->start = end;
          ram_res->end = crashk_res.end;
          ram_res->flags = IORESOURCE_BUSY | IORESOURCE_MEM;
          ram_res->name = "System RAM";
  
          crashk_res.end = end - 1;
  
          insert_resource(&iomem_resource, ram_res);
          crash_unmap_reserved_pages();
  
  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\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 != '@')
                          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);
          else if (*cur != ' ' && *cur != '\0') {
                  pr_warning("crashkernel: unrecognized char\n");
                  return -EINVAL;
          }
  
          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;
  }
  
  
  static void update_vmcoreinfo_note(void)
  {
          u32 *buf = vmcoreinfo_note;
  
          if (!vmcoreinfo_size)
                  return;
          buf = append_elf_note(buf, VMCOREINFO_NOTE_NAME, 0, vmcoreinfo_data,
                                vmcoreinfo_size);
          final_note(buf);
  }
  
  void crash_save_vmcoreinfo(void)
  {
          vmcoreinfo_append_str("CRASHTIME=%ld\n", get_seconds());
          update_vmcoreinfo_note();
  }
  
  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);
  #ifdef CONFIG_MMU
          VMCOREINFO_SYMBOL(swapper_pg_dir);
  #endif
          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();
          update_vmcoreinfo_note();
  
          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) {
                  lock_system_sleep();
                  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_end(). We *must* call
                   * dpm_suspend_end() 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_end(PMSG_FREEZE);
                  if (error)
                          goto Resume_devices;
                  error = disable_nonboot_cpus();
                  if (error)
                          goto Enable_cpus;
                  local_irq_disable();
                  error = syscore_suspend();
                  if (error)
                          goto Enable_irqs;
          } else
  #endif
          {
                  kernel_restart_prepare(NULL);
                  printk(KERN_EMERG "Starting new kernel\n");
                  machine_shutdown();
          }
  
          machine_kexec(kexec_image);
  
  #ifdef CONFIG_KEXEC_JUMP
          if (kexec_image->preserve_context) {
                  syscore_resume();
   Enable_irqs:
                  local_irq_enable();
   Enable_cpus:
                  enable_nonboot_cpus();
                  dpm_resume_start(PMSG_RESTORE);
   Resume_devices:
                  dpm_resume_end(PMSG_RESTORE);
   Resume_console:
                  resume_console();
                  thaw_processes();
   Restore_console:
                  pm_restore_console();
                  unlock_system_sleep();
          }
  #endif
  
   Unlock:
          mutex_unlock(&kexec_mutex);
          return error;
  }

Cache object: afa80b3177d2fa77d29ef744a2b7f0d4