kexec: support for kexec on panic using new system call

[linux.git] / 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.
 */

#define pr_fmt(fmt)     "kexec: " fmt

#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 <linux/compiler.h>
#include <linux/hugetlb.h>

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

#include <crypto/hash.h>
#include <crypto/sha.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);

/* Flag to indicate we are going to kexec a new kernel */
bool kexec_in_progress = false;

/*
 * Declare these symbols weak so that if architecture provides a purgatory,
 * these will be overridden.
 */
char __weak kexec_purgatory[0];
size_t __weak kexec_purgatory_size = 0;

static int kexec_calculate_store_digests(struct kimage *image);

/* 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
};
struct resource crashk_low_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 copy_user_segment_list(struct kimage *image,
                                  unsigned long nr_segments,
                                  struct kexec_segment __user *segments)
{
        int ret;
        size_t segment_bytes;

        /* Read in the segments */
        image->nr_segments = nr_segments;
        segment_bytes = nr_segments * sizeof(*segments);
        ret = copy_from_user(image->segment, segments, segment_bytes);
        if (ret)
                ret = -EFAULT;

        return ret;
}

static int sanity_check_segment_list(struct kimage *image)
{
        int result, i;
        unsigned long nr_segments = image->nr_segments;

        /*
         * 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))
                        return result;
                if (mend >= KEXEC_DESTINATION_MEMORY_LIMIT)
                        return result;
        }

        /* 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))
                                return result;
                }
        }

        /* 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)
                        return result;
        }

        /*
         * 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.
         */

        if (image->type == KEXEC_TYPE_CRASH) {
                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))
                                return result;
                }
        }

        return 0;
}

static struct kimage *do_kimage_alloc_init(void)
{
        struct kimage *image;

        /* Allocate a controlling structure */
        image = kzalloc(sizeof(*image), GFP_KERNEL);
        if (!image)
                return NULL;

        image->head = 0;
        image->entry = &image->head;
        image->last_entry = &image->head;
        image->control_page = ~0; /* By default this does not apply */
        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->unusable_pages);

        return image;
}

static void kimage_free_page_list(struct list_head *list);

static int kimage_alloc_init(struct kimage **rimage, unsigned long entry,
                             unsigned long nr_segments,
                             struct kexec_segment __user *segments,
                             unsigned long flags)
{
        int ret;
        struct kimage *image;
        bool kexec_on_panic = flags & KEXEC_ON_CRASH;

        if (kexec_on_panic) {
                /* Verify we have a valid entry point */
                if ((entry < crashk_res.start) || (entry > crashk_res.end))
                        return -EADDRNOTAVAIL;
        }

        /* Allocate and initialize a controlling structure */
        image = do_kimage_alloc_init();
        if (!image)
                return -ENOMEM;

        image->start = entry;

        ret = copy_user_segment_list(image, nr_segments, segments);
        if (ret)
                goto out_free_image;

        ret = sanity_check_segment_list(image);
        if (ret)
                goto out_free_image;

         /* Enable the special crash kernel control page allocation policy. */
        if (kexec_on_panic) {
                image->control_page = crashk_res.start;
                image->type = KEXEC_TYPE_CRASH;
        }

        /*
         * 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.
         */
        ret = -ENOMEM;
        image->control_code_page = kimage_alloc_control_pages(image,
                                           get_order(KEXEC_CONTROL_PAGE_SIZE));
        if (!image->control_code_page) {
                pr_err("Could not allocate control_code_buffer\n");
                goto out_free_image;
        }

        if (!kexec_on_panic) {
                image->swap_page = kimage_alloc_control_pages(image, 0);
                if (!image->swap_page) {
                        pr_err("Could not allocate swap buffer\n");
                        goto out_free_control_pages;
                }
        }

        *rimage = image;
        return 0;
out_free_control_pages:
        kimage_free_page_list(&image->control_pages);
out_free_image:
        kfree(image);
        return ret;
}

static int copy_file_from_fd(int fd, void **buf, unsigned long *buf_len)
{
        struct fd f = fdget(fd);
        int ret;
        struct kstat stat;
        loff_t pos;
        ssize_t bytes = 0;

        if (!f.file)
                return -EBADF;

        ret = vfs_getattr(&f.file->f_path, &stat);
        if (ret)
                goto out;

        if (stat.size > INT_MAX) {
                ret = -EFBIG;
                goto out;
        }

        /* Don't hand 0 to vmalloc, it whines. */
        if (stat.size == 0) {
                ret = -EINVAL;
                goto out;
        }

        *buf = vmalloc(stat.size);
        if (!*buf) {
                ret = -ENOMEM;
                goto out;
        }

        pos = 0;
        while (pos < stat.size) {
                bytes = kernel_read(f.file, pos, (char *)(*buf) + pos,
                                    stat.size - pos);
                if (bytes < 0) {
                        vfree(*buf);
                        ret = bytes;
                        goto out;
                }

                if (bytes == 0)
                        break;
                pos += bytes;
        }

        if (pos != stat.size) {
                ret = -EBADF;
                vfree(*buf);
                goto out;
        }

        *buf_len = pos;
out:
        fdput(f);
        return ret;
}

/* Architectures can provide this probe function */
int __weak arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
                                         unsigned long buf_len)
{
        return -ENOEXEC;
}

void * __weak arch_kexec_kernel_image_load(struct kimage *image)
{
        return ERR_PTR(-ENOEXEC);
}

void __weak arch_kimage_file_post_load_cleanup(struct kimage *image)
{
}

/* Apply relocations of type RELA */
int __weak
arch_kexec_apply_relocations_add(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
                                 unsigned int relsec)
{
        pr_err("RELA relocation unsupported.\n");
        return -ENOEXEC;
}

/* Apply relocations of type REL */
int __weak
arch_kexec_apply_relocations(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
                             unsigned int relsec)
{
        pr_err("REL relocation unsupported.\n");
        return -ENOEXEC;
}

/*
 * Free up memory used by kernel, initrd, and comand line. This is temporary
 * memory allocation which is not needed any more after these buffers have
 * been loaded into separate segments and have been copied elsewhere.
 */
static void kimage_file_post_load_cleanup(struct kimage *image)
{
        struct purgatory_info *pi = &image->purgatory_info;

        vfree(image->kernel_buf);
        image->kernel_buf = NULL;

        vfree(image->initrd_buf);
        image->initrd_buf = NULL;

        kfree(image->cmdline_buf);
        image->cmdline_buf = NULL;

        vfree(pi->purgatory_buf);
        pi->purgatory_buf = NULL;

        vfree(pi->sechdrs);
        pi->sechdrs = NULL;

        /* See if architecture has anything to cleanup post load */
        arch_kimage_file_post_load_cleanup(image);

        /*
         * Above call should have called into bootloader to free up
         * any data stored in kimage->image_loader_data. It should
         * be ok now to free it up.
         */
        kfree(image->image_loader_data);
        image->image_loader_data = NULL;
}

/*
 * In file mode list of segments is prepared by kernel. Copy relevant
 * data from user space, do error checking, prepare segment list
 */
static int
kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
                             const char __user *cmdline_ptr,
                             unsigned long cmdline_len, unsigned flags)
{
        int ret = 0;
        void *ldata;

        ret = copy_file_from_fd(kernel_fd, &image->kernel_buf,
                                &image->kernel_buf_len);
        if (ret)
                return ret;

        /* Call arch image probe handlers */
        ret = arch_kexec_kernel_image_probe(image, image->kernel_buf,
                                            image->kernel_buf_len);

        if (ret)
                goto out;

        /* It is possible that there no initramfs is being loaded */
        if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
                ret = copy_file_from_fd(initrd_fd, &image->initrd_buf,
                                        &image->initrd_buf_len);
                if (ret)
                        goto out;
        }

        if (cmdline_len) {
                image->cmdline_buf = kzalloc(cmdline_len, GFP_KERNEL);
                if (!image->cmdline_buf) {
                        ret = -ENOMEM;
                        goto out;
                }

                ret = copy_from_user(image->cmdline_buf, cmdline_ptr,
                                     cmdline_len);
                if (ret) {
                        ret = -EFAULT;
                        goto out;
                }

                image->cmdline_buf_len = cmdline_len;

                /* command line should be a string with last byte null */
                if (image->cmdline_buf[cmdline_len - 1] != '\0') {
                        ret = -EINVAL;
                        goto out;
                }
        }

        /* Call arch image load handlers */
        ldata = arch_kexec_kernel_image_load(image);

        if (IS_ERR(ldata)) {
                ret = PTR_ERR(ldata);
                goto out;
        }

        image->image_loader_data = ldata;
out:
        /* In case of error, free up all allocated memory in this function */
        if (ret)
                kimage_file_post_load_cleanup(image);
        return ret;
}

static int
kimage_file_alloc_init(struct kimage **rimage, int kernel_fd,
                       int initrd_fd, const char __user *cmdline_ptr,
                       unsigned long cmdline_len, unsigned long flags)
{
        int ret;
        struct kimage *image;
        bool kexec_on_panic = flags & KEXEC_FILE_ON_CRASH;

        image = do_kimage_alloc_init();
        if (!image)
                return -ENOMEM;

        image->file_mode = 1;

        if (kexec_on_panic) {
                /* Enable special crash kernel control page alloc policy. */
                image->control_page = crashk_res.start;
                image->type = KEXEC_TYPE_CRASH;
        }

        ret = kimage_file_prepare_segments(image, kernel_fd, initrd_fd,
                                           cmdline_ptr, cmdline_len, flags);
        if (ret)
                goto out_free_image;

        ret = sanity_check_segment_list(image);
        if (ret)
                goto out_free_post_load_bufs;

        ret = -ENOMEM;
        image->control_code_page = kimage_alloc_control_pages(image,
                                           get_order(KEXEC_CONTROL_PAGE_SIZE));
        if (!image->control_code_page) {
                pr_err("Could not allocate control_code_buffer\n");
                goto out_free_post_load_bufs;
        }

        if (!kexec_on_panic) {
                image->swap_page = kimage_alloc_control_pages(image, 0);
                if (!image->swap_page) {
                        pr_err(KERN_ERR "Could not allocate swap buffer\n");
                        goto out_free_control_pages;
                }
        }

        *rimage = image;
        return 0;
out_free_control_pages:
        kimage_free_page_list(&image->control_pages);
out_free_post_load_bufs:
        kimage_file_post_load_cleanup(image);
out_free_image:
        kfree(image);
        return ret;
}

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;
                /* 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->unusable_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);

        /*
         * Free up any temporary buffers allocated. This might hit if
         * error occurred much later after buffer allocation.
         */
        if (image->file_mode)
                kimage_file_post_load_cleanup(image);

        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->unusable_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;
        size_t ubytes, mbytes;
        int result;
        unsigned char __user *buf = NULL;
        unsigned char *kbuf = NULL;

        result = 0;
        if (image->file_mode)
                kbuf = segment->kbuf;
        else
                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 = min_t(size_t, mbytes,
                                PAGE_SIZE - (maddr & ~PAGE_MASK));
                uchunk = min(ubytes, mchunk);

                /* For file based kexec, source pages are in kernel memory */
                if (image->file_mode)
                        memcpy(ptr, kbuf, uchunk);
                else
                        result = copy_from_user(ptr, buf, uchunk);
                kunmap(page);
                if (result) {
                        result = -EFAULT;
                        goto out;
                }
                ubytes -= uchunk;
                maddr  += mchunk;
                if (image->file_mode)
                        kbuf += mchunk;
                else
                        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;
        size_t ubytes, mbytes;
        int result;
        unsigned char __user *buf = NULL;
        unsigned char *kbuf = NULL;

        result = 0;
        if (image->file_mode)
                kbuf = segment->kbuf;
        else
                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 = min_t(size_t, mbytes,
                                PAGE_SIZE - (maddr & ~PAGE_MASK));
                uchunk = min(ubytes, mchunk);
                if (mchunk > uchunk) {
                        /* Zero the trailing part of the page */
                        memset(ptr + uchunk, 0, mchunk - uchunk);
                }

                /* For file based kexec, source pages are in kernel memory */
                if (image->file_mode)
                        memcpy(ptr, kbuf, uchunk);
                else
                        result = copy_from_user(ptr, buf, uchunk);
                kexec_flush_icache_page(page);
                kunmap(page);
                if (result) {
                        result = -EFAULT;
                        goto out;
                }
                ubytes -= uchunk;
                maddr  += mchunk;
                if (image->file_mode)
                        kbuf += mchunk;
                else
                        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 then 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;
int kexec_load_disabled;

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) || kexec_load_disabled)
                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_alloc_init(&image, entry, nr_segments,
                                                   segments, flags);
                /* 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_alloc_init(&image, entry, nr_segments,
                                                   segments, flags);
                        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
COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
                       compat_ulong_t, nr_segments,
                       struct compat_kexec_segment __user *, segments,
                       compat_ulong_t, 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

SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
                unsigned long, cmdline_len, const char __user *, cmdline_ptr,
                unsigned long, flags)
{
        int ret = 0, i;
        struct kimage **dest_image, *image;

        /* We only trust the superuser with rebooting the system. */
        if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
                return -EPERM;

        /* Make sure we have a legal set of flags */
        if (flags != (flags & KEXEC_FILE_FLAGS))
                return -EINVAL;

        image = NULL;

        if (!mutex_trylock(&kexec_mutex))
                return -EBUSY;

        dest_image = &kexec_image;
        if (flags & KEXEC_FILE_ON_CRASH)
                dest_image = &kexec_crash_image;

        if (flags & KEXEC_FILE_UNLOAD)
                goto exchange;

        /*
         * In case of crash, new kernel gets loaded in reserved region. It is
         * same memory where old crash kernel might be loaded. Free any
         * current crash dump kernel before we corrupt it.
         */
        if (flags & KEXEC_FILE_ON_CRASH)
                kimage_free(xchg(&kexec_crash_image, NULL));

        ret = kimage_file_alloc_init(&image, kernel_fd, initrd_fd, cmdline_ptr,
                                     cmdline_len, flags);
        if (ret)
                goto out;

        ret = machine_kexec_prepare(image);
        if (ret)
                goto out;

        ret = kexec_calculate_store_digests(image);
        if (ret)
                goto out;

        for (i = 0; i < image->nr_segments; i++) {
                struct kexec_segment *ksegment;

                ksegment = &image->segment[i];
                pr_debug("Loading segment %d: buf=0x%p bufsz=0x%zx mem=0x%lx memsz=0x%zx\n",
                         i, ksegment->buf, ksegment->bufsz, ksegment->mem,
                         ksegment->memsz);

                ret = kimage_load_segment(image, &image->segment[i]);
                if (ret)
                        goto out;
        }

        kimage_terminate(image);

        /*
         * Free up any temporary buffers allocated which are not needed
         * after image has been loaded
         */
        kimage_file_post_load_cleanup(image);
exchange:
        image = xchg(dest_image, image);
out:
        mutex_unlock(&kexec_mutex);
        kimage_free(image);
        return ret;
}

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)
                free_reserved_page(pfn_to_page(addr >> PAGE_SHIFT));
}

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) {
                pr_warn("Kexec: Memory allocation for saving cpu register states failed\n");
                return -ENOMEM;
        }
        return 0;
}
subsys_initcall(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_warn("crashkernel: Memory value expected\n");
                        return -EINVAL;
                }
                cur = tmp;
                if (*cur != '-') {
                        pr_warn("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_warn("crashkernel: Memory value expected\n");
                                return -EINVAL;
                        }
                        cur = tmp;
                        if (end <= start) {
                                pr_warn("crashkernel: end <= start\n");
                                return -EINVAL;
                        }
                }

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

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

        if (*cur == '@')
                *crash_base = memparse(cur+1, &cur);
        else if (*cur != ' ' && *cur != '\0') {
                pr_warn("crashkernel: unrecognized char\n");
                return -EINVAL;
        }

        return 0;
}

#define SUFFIX_HIGH 0
#define SUFFIX_LOW  1
#define SUFFIX_NULL 2
static __initdata char *suffix_tbl[] = {
        [SUFFIX_HIGH] = ",high",
        [SUFFIX_LOW]  = ",low",
        [SUFFIX_NULL] = NULL,
};

/*
 * That function parses "suffix"  crashkernel command lines like
 *
 *      crashkernel=size,[high|low]
 *
 * It returns 0 on success and -EINVAL on failure.
 */
static int __init parse_crashkernel_suffix(char *cmdline,
                                           unsigned long long   *crash_size,
                                           unsigned long long   *crash_base,
                                           const char *suffix)
{
        char *cur = cmdline;

        *crash_size = memparse(cmdline, &cur);
        if (cmdline == cur) {
                pr_warn("crashkernel: memory value expected\n");
                return -EINVAL;
        }

        /* check with suffix */
        if (strncmp(cur, suffix, strlen(suffix))) {
                pr_warn("crashkernel: unrecognized char\n");
                return -EINVAL;
        }
        cur += strlen(suffix);
        if (*cur != ' ' && *cur != '\0') {
                pr_warn("crashkernel: unrecognized char\n");
                return -EINVAL;
        }

        return 0;
}

static __init char *get_last_crashkernel(char *cmdline,
                             const char *name,
                             const char *suffix)
{
        char *p = cmdline, *ck_cmdline = NULL;

        /* find crashkernel and use the last one if there are more */
        p = strstr(p, name);
        while (p) {
                char *end_p = strchr(p, ' ');
                char *q;

                if (!end_p)
                        end_p = p + strlen(p);

                if (!suffix) {
                        int i;

                        /* skip the one with any known suffix */
                        for (i = 0; suffix_tbl[i]; i++) {
                                q = end_p - strlen(suffix_tbl[i]);
                                if (!strncmp(q, suffix_tbl[i],
                                             strlen(suffix_tbl[i])))
                                        goto next;
                        }
                        ck_cmdline = p;
                } else {
                        q = end_p - strlen(suffix);
                        if (!strncmp(q, suffix, strlen(suffix)))
                                ck_cmdline = p;
                }
next:
                p = strstr(p+1, name);
        }

        if (!ck_cmdline)
                return NULL;

        return ck_cmdline;
}

static int __init __parse_crashkernel(char *cmdline,
                             unsigned long long system_ram,
                             unsigned long long *crash_size,
                             unsigned long long *crash_base,
                             const char *name,
                             const char *suffix)
{
        char    *first_colon, *first_space;
        char    *ck_cmdline;

        BUG_ON(!crash_size || !crash_base);
        *crash_size = 0;
        *crash_base = 0;

        ck_cmdline = get_last_crashkernel(cmdline, name, suffix);

        if (!ck_cmdline)
                return -EINVAL;

        ck_cmdline += strlen(name);

        if (suffix)
                return parse_crashkernel_suffix(ck_cmdline, crash_size,
                                crash_base, suffix);
        /*
         * 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);

        return parse_crashkernel_simple(ck_cmdline, crash_size, crash_base);
}

/*
 * 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)
{
        return __parse_crashkernel(cmdline, system_ram, crash_size, crash_base,
                                        "crashkernel=", NULL);
}

int __init parse_crashkernel_high(char *cmdline,
                             unsigned long long system_ram,
                             unsigned long long *crash_size,
                             unsigned long long *crash_base)
{
        return __parse_crashkernel(cmdline, system_ram, crash_size, crash_base,
                                "crashkernel=", suffix_tbl[SUFFIX_HIGH]);
}

int __init parse_crashkernel_low(char *cmdline,
                             unsigned long long system_ram,
                             unsigned long long *crash_size,
                             unsigned long long *crash_base)
{
        return __parse_crashkernel(cmdline, system_ram, crash_size, crash_base,
                                "crashkernel=", suffix_tbl[SUFFIX_LOW]);
}

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];
        size_t r;

        va_start(args, fmt);
        r = vscnprintf(buf, sizeof(buf), fmt, args);
        va_end(args);

        r = min(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 __weak arch_crash_save_vmcoreinfo(void)
{}

unsigned long __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(vmap_area_list);

#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(page, _mapcount);
        VMCOREINFO_OFFSET(page, private);
        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(vmap_area, va_start);
        VMCOREINFO_OFFSET(vmap_area, list);
        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);
        VMCOREINFO_NUMBER(PG_slab);
#ifdef CONFIG_MEMORY_FAILURE
        VMCOREINFO_NUMBER(PG_hwpoison);
#endif
        VMCOREINFO_NUMBER(PG_head_mask);
        VMCOREINFO_NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE);
#ifdef CONFIG_HUGETLBFS
        VMCOREINFO_SYMBOL(free_huge_page);
#endif

        arch_crash_save_vmcoreinfo();
        update_vmcoreinfo_note();

        return 0;
}

subsys_initcall(crash_save_vmcoreinfo_init);

static int __kexec_add_segment(struct kimage *image, char *buf,
                               unsigned long bufsz, unsigned long mem,
                               unsigned long memsz)
{
        struct kexec_segment *ksegment;

        ksegment = &image->segment[image->nr_segments];
        ksegment->kbuf = buf;
        ksegment->bufsz = bufsz;
        ksegment->mem = mem;
        ksegment->memsz = memsz;
        image->nr_segments++;

        return 0;
}

static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
                                    struct kexec_buf *kbuf)
{
        struct kimage *image = kbuf->image;
        unsigned long temp_start, temp_end;

        temp_end = min(end, kbuf->buf_max);
        temp_start = temp_end - kbuf->memsz;

        do {
                /* align down start */
                temp_start = temp_start & (~(kbuf->buf_align - 1));

                if (temp_start < start || temp_start < kbuf->buf_min)
                        return 0;

                temp_end = temp_start + kbuf->memsz - 1;

                /*
                 * Make sure this does not conflict with any of existing
                 * segments
                 */
                if (kimage_is_destination_range(image, temp_start, temp_end)) {
                        temp_start = temp_start - PAGE_SIZE;
                        continue;
                }

                /* We found a suitable memory range */
                break;
        } while (1);

        /* If we are here, we found a suitable memory range */
        __kexec_add_segment(image, kbuf->buffer, kbuf->bufsz, temp_start,
                            kbuf->memsz);

        /* Success, stop navigating through remaining System RAM ranges */
        return 1;
}

static int locate_mem_hole_bottom_up(unsigned long start, unsigned long end,
                                     struct kexec_buf *kbuf)
{
        struct kimage *image = kbuf->image;
        unsigned long temp_start, temp_end;

        temp_start = max(start, kbuf->buf_min);

        do {
                temp_start = ALIGN(temp_start, kbuf->buf_align);
                temp_end = temp_start + kbuf->memsz - 1;

                if (temp_end > end || temp_end > kbuf->buf_max)
                        return 0;
                /*
                 * Make sure this does not conflict with any of existing
                 * segments
                 */
                if (kimage_is_destination_range(image, temp_start, temp_end)) {
                        temp_start = temp_start + PAGE_SIZE;
                        continue;
                }

                /* We found a suitable memory range */
                break;
        } while (1);

        /* If we are here, we found a suitable memory range */
        __kexec_add_segment(image, kbuf->buffer, kbuf->bufsz, temp_start,
                            kbuf->memsz);

        /* Success, stop navigating through remaining System RAM ranges */
        return 1;
}

static int locate_mem_hole_callback(u64 start, u64 end, void *arg)
{
        struct kexec_buf *kbuf = (struct kexec_buf *)arg;
        unsigned long sz = end - start + 1;

        /* Returning 0 will take to next memory range */
        if (sz < kbuf->memsz)
                return 0;

        if (end < kbuf->buf_min || start > kbuf->buf_max)
                return 0;

        /*
         * Allocate memory top down with-in ram range. Otherwise bottom up
         * allocation.
         */
        if (kbuf->top_down)
                return locate_mem_hole_top_down(start, end, kbuf);
        return locate_mem_hole_bottom_up(start, end, kbuf);
}

/*
 * Helper function for placing a buffer in a kexec segment. This assumes
 * that kexec_mutex is held.
 */
int kexec_add_buffer(struct kimage *image, char *buffer, unsigned long bufsz,
                     unsigned long memsz, unsigned long buf_align,
                     unsigned long buf_min, unsigned long buf_max,
                     bool top_down, unsigned long *load_addr)
{

        struct kexec_segment *ksegment;
        struct kexec_buf buf, *kbuf;
        int ret;

        /* Currently adding segment this way is allowed only in file mode */
        if (!image->file_mode)
                return -EINVAL;

        if (image->nr_segments >= KEXEC_SEGMENT_MAX)
                return -EINVAL;

        /*
         * Make sure we are not trying to add buffer after allocating
         * control pages. All segments need to be placed first before
         * any control pages are allocated. As control page allocation
         * logic goes through list of segments to make sure there are
         * no destination overlaps.
         */
        if (!list_empty(&image->control_pages)) {
                WARN_ON(1);
                return -EINVAL;
        }

        memset(&buf, 0, sizeof(struct kexec_buf));
        kbuf = &buf;
        kbuf->image = image;
        kbuf->buffer = buffer;
        kbuf->bufsz = bufsz;

        kbuf->memsz = ALIGN(memsz, PAGE_SIZE);
        kbuf->buf_align = max(buf_align, PAGE_SIZE);
        kbuf->buf_min = buf_min;
        kbuf->buf_max = buf_max;
        kbuf->top_down = top_down;

        /* Walk the RAM ranges and allocate a suitable range for the buffer */
        if (image->type == KEXEC_TYPE_CRASH)
                ret = walk_iomem_res("Crash kernel",
                                     IORESOURCE_MEM | IORESOURCE_BUSY,
                                     crashk_res.start, crashk_res.end, kbuf,
                                     locate_mem_hole_callback);
        else
                ret = walk_system_ram_res(0, -1, kbuf,
                                          locate_mem_hole_callback);
        if (ret != 1) {
                /* A suitable memory range could not be found for buffer */
                return -EADDRNOTAVAIL;
        }

        /* Found a suitable memory range */
        ksegment = &image->segment[image->nr_segments - 1];
        *load_addr = ksegment->mem;
        return 0;
}

/* Calculate and store the digest of segments */
static int kexec_calculate_store_digests(struct kimage *image)
{
        struct crypto_shash *tfm;
        struct shash_desc *desc;
        int ret = 0, i, j, zero_buf_sz, sha_region_sz;
        size_t desc_size, nullsz;
        char *digest;
        void *zero_buf;
        struct kexec_sha_region *sha_regions;
        struct purgatory_info *pi = &image->purgatory_info;

        zero_buf = __va(page_to_pfn(ZERO_PAGE(0)) << PAGE_SHIFT);
        zero_buf_sz = PAGE_SIZE;

        tfm = crypto_alloc_shash("sha256", 0, 0);
        if (IS_ERR(tfm)) {
                ret = PTR_ERR(tfm);
                goto out;
        }

        desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
        desc = kzalloc(desc_size, GFP_KERNEL);
        if (!desc) {
                ret = -ENOMEM;
                goto out_free_tfm;
        }

        sha_region_sz = KEXEC_SEGMENT_MAX * sizeof(struct kexec_sha_region);
        sha_regions = vzalloc(sha_region_sz);
        if (!sha_regions)
                goto out_free_desc;

        desc->tfm   = tfm;
        desc->flags = 0;

        ret = crypto_shash_init(desc);
        if (ret < 0)
                goto out_free_sha_regions;

        digest = kzalloc(SHA256_DIGEST_SIZE, GFP_KERNEL);
        if (!digest) {
                ret = -ENOMEM;
                goto out_free_sha_regions;
        }

        for (j = i = 0; i < image->nr_segments; i++) {
                struct kexec_segment *ksegment;

                ksegment = &image->segment[i];
                /*
                 * Skip purgatory as it will be modified once we put digest
                 * info in purgatory.
                 */
                if (ksegment->kbuf == pi->purgatory_buf)
                        continue;

                ret = crypto_shash_update(desc, ksegment->kbuf,
                                          ksegment->bufsz);
                if (ret)
                        break;

                /*
                 * Assume rest of the buffer is filled with zero and
                 * update digest accordingly.
                 */
                nullsz = ksegment->memsz - ksegment->bufsz;
                while (nullsz) {
                        unsigned long bytes = nullsz;

                        if (bytes > zero_buf_sz)
                                bytes = zero_buf_sz;
                        ret = crypto_shash_update(desc, zero_buf, bytes);
                        if (ret)
                                break;
                        nullsz -= bytes;
                }

                if (ret)
                        break;

                sha_regions[j].start = ksegment->mem;
                sha_regions[j].len = ksegment->memsz;
                j++;
        }

        if (!ret) {
                ret = crypto_shash_final(desc, digest);
                if (ret)
                        goto out_free_digest;
                ret = kexec_purgatory_get_set_symbol(image, "sha_regions",
                                                sha_regions, sha_region_sz, 0);
                if (ret)
                        goto out_free_digest;

                ret = kexec_purgatory_get_set_symbol(image, "sha256_digest",
                                                digest, SHA256_DIGEST_SIZE, 0);
                if (ret)
                        goto out_free_digest;
        }

out_free_digest:
        kfree(digest);
out_free_sha_regions:
        vfree(sha_regions);
out_free_desc:
        kfree(desc);
out_free_tfm:
        kfree(tfm);
out:
        return ret;
}

/* Actually load purgatory. Lot of code taken from kexec-tools */
static int __kexec_load_purgatory(struct kimage *image, unsigned long min,
                                  unsigned long max, int top_down)
{
        struct purgatory_info *pi = &image->purgatory_info;
        unsigned long align, buf_align, bss_align, buf_sz, bss_sz, bss_pad;
        unsigned long memsz, entry, load_addr, curr_load_addr, bss_addr, offset;
        unsigned char *buf_addr, *src;
        int i, ret = 0, entry_sidx = -1;
        const Elf_Shdr *sechdrs_c;
        Elf_Shdr *sechdrs = NULL;
        void *purgatory_buf = NULL;

        /*
         * sechdrs_c points to section headers in purgatory and are read
         * only. No modifications allowed.
         */
        sechdrs_c = (void *)pi->ehdr + pi->ehdr->e_shoff;

        /*
         * We can not modify sechdrs_c[] and its fields. It is read only.
         * Copy it over to a local copy where one can store some temporary
         * data and free it at the end. We need to modify ->sh_addr and
         * ->sh_offset fields to keep track of permanent and temporary
         * locations of sections.
         */
        sechdrs = vzalloc(pi->ehdr->e_shnum * sizeof(Elf_Shdr));
        if (!sechdrs)
                return -ENOMEM;

        memcpy(sechdrs, sechdrs_c, pi->ehdr->e_shnum * sizeof(Elf_Shdr));

        /*
         * We seem to have multiple copies of sections. First copy is which
         * is embedded in kernel in read only section. Some of these sections
         * will be copied to a temporary buffer and relocated. And these
         * sections will finally be copied to their final destination at
         * segment load time.
         *
         * Use ->sh_offset to reflect section address in memory. It will
         * point to original read only copy if section is not allocatable.
         * Otherwise it will point to temporary copy which will be relocated.
         *
         * Use ->sh_addr to contain final address of the section where it
         * will go during execution time.
         */
        for (i = 0; i < pi->ehdr->e_shnum; i++) {
                if (sechdrs[i].sh_type == SHT_NOBITS)
                        continue;

                sechdrs[i].sh_offset = (unsigned long)pi->ehdr +
                                                sechdrs[i].sh_offset;
        }

        /*
         * Identify entry point section and make entry relative to section
         * start.
         */
        entry = pi->ehdr->e_entry;
        for (i = 0; i < pi->ehdr->e_shnum; i++) {
                if (!(sechdrs[i].sh_flags & SHF_ALLOC))
                        continue;

                if (!(sechdrs[i].sh_flags & SHF_EXECINSTR))
                        continue;

                /* Make entry section relative */
                if (sechdrs[i].sh_addr <= pi->ehdr->e_entry &&
                    ((sechdrs[i].sh_addr + sechdrs[i].sh_size) >
                     pi->ehdr->e_entry)) {
                        entry_sidx = i;
                        entry -= sechdrs[i].sh_addr;
                        break;
                }
        }

        /* Determine how much memory is needed to load relocatable object. */
        buf_align = 1;
        bss_align = 1;
        buf_sz = 0;
        bss_sz = 0;

        for (i = 0; i < pi->ehdr->e_shnum; i++) {
                if (!(sechdrs[i].sh_flags & SHF_ALLOC))
                        continue;

                align = sechdrs[i].sh_addralign;
                if (sechdrs[i].sh_type != SHT_NOBITS) {
                        if (buf_align < align)
                                buf_align = align;
                        buf_sz = ALIGN(buf_sz, align);
                        buf_sz += sechdrs[i].sh_size;
                } else {
                        /* bss section */
                        if (bss_align < align)
                                bss_align = align;
                        bss_sz = ALIGN(bss_sz, align);
                        bss_sz += sechdrs[i].sh_size;
                }
        }

        /* Determine the bss padding required to align bss properly */
        bss_pad = 0;
        if (buf_sz & (bss_align - 1))
                bss_pad = bss_align - (buf_sz & (bss_align - 1));

        memsz = buf_sz + bss_pad + bss_sz;

        /* Allocate buffer for purgatory */
        purgatory_buf = vzalloc(buf_sz);
        if (!purgatory_buf) {
                ret = -ENOMEM;
                goto out;
        }

        if (buf_align < bss_align)
                buf_align = bss_align;

        /* Add buffer to segment list */
        ret = kexec_add_buffer(image, purgatory_buf, buf_sz, memsz,
                                buf_align, min, max, top_down,
                                &pi->purgatory_load_addr);
        if (ret)
                goto out;

        /* Load SHF_ALLOC sections */
        buf_addr = purgatory_buf;
        load_addr = curr_load_addr = pi->purgatory_load_addr;
        bss_addr = load_addr + buf_sz + bss_pad;

        for (i = 0; i < pi->ehdr->e_shnum; i++) {
                if (!(sechdrs[i].sh_flags & SHF_ALLOC))
                        continue;

                align = sechdrs[i].sh_addralign;
                if (sechdrs[i].sh_type != SHT_NOBITS) {
                        curr_load_addr = ALIGN(curr_load_addr, align);
                        offset = curr_load_addr - load_addr;
                        /* We already modifed ->sh_offset to keep src addr */
                        src = (char *) sechdrs[i].sh_offset;
                        memcpy(buf_addr + offset, src, sechdrs[i].sh_size);

                        /* Store load address and source address of section */
                        sechdrs[i].sh_addr = curr_load_addr;

                        /*
                         * This section got copied to temporary buffer. Update
                         * ->sh_offset accordingly.
                         */
                        sechdrs[i].sh_offset = (unsigned long)(buf_addr + offset);

                        /* Advance to the next address */
                        curr_load_addr += sechdrs[i].sh_size;
                } else {
                        bss_addr = ALIGN(bss_addr, align);
                        sechdrs[i].sh_addr = bss_addr;
                        bss_addr += sechdrs[i].sh_size;
                }
        }

        /* Update entry point based on load address of text section */
        if (entry_sidx >= 0)
                entry += sechdrs[entry_sidx].sh_addr;

        /* Make kernel jump to purgatory after shutdown */
        image->start = entry;

        /* Used later to get/set symbol values */
        pi->sechdrs = sechdrs;

        /*
         * Used later to identify which section is purgatory and skip it
         * from checksumming.
         */
        pi->purgatory_buf = purgatory_buf;
        return ret;
out:
        vfree(sechdrs);
        vfree(purgatory_buf);
        return ret;
}

static int kexec_apply_relocations(struct kimage *image)
{
        int i, ret;
        struct purgatory_info *pi = &image->purgatory_info;
        Elf_Shdr *sechdrs = pi->sechdrs;

        /* Apply relocations */
        for (i = 0; i < pi->ehdr->e_shnum; i++) {
                Elf_Shdr *section, *symtab;

                if (sechdrs[i].sh_type != SHT_RELA &&
                    sechdrs[i].sh_type != SHT_REL)
                        continue;

                /*
                 * For section of type SHT_RELA/SHT_REL,
                 * ->sh_link contains section header index of associated
                 * symbol table. And ->sh_info contains section header
                 * index of section to which relocations apply.
                 */
                if (sechdrs[i].sh_info >= pi->ehdr->e_shnum ||
                    sechdrs[i].sh_link >= pi->ehdr->e_shnum)
                        return -ENOEXEC;

                section = &sechdrs[sechdrs[i].sh_info];
                symtab = &sechdrs[sechdrs[i].sh_link];

                if (!(section->sh_flags & SHF_ALLOC))
                        continue;

                /*
                 * symtab->sh_link contain section header index of associated
                 * string table.
                 */
                if (symtab->sh_link >= pi->ehdr->e_shnum)
                        /* Invalid section number? */
                        continue;

                /*
                 * Respective archicture needs to provide support for applying
                 * relocations of type SHT_RELA/SHT_REL.
                 */
                if (sechdrs[i].sh_type == SHT_RELA)
                        ret = arch_kexec_apply_relocations_add(pi->ehdr,
                                                               sechdrs, i);
                else if (sechdrs[i].sh_type == SHT_REL)
                        ret = arch_kexec_apply_relocations(pi->ehdr,
                                                           sechdrs, i);
                if (ret)
                        return ret;
        }

        return 0;
}

/* Load relocatable purgatory object and relocate it appropriately */
int kexec_load_purgatory(struct kimage *image, unsigned long min,
                         unsigned long max, int top_down,
                         unsigned long *load_addr)
{
        struct purgatory_info *pi = &image->purgatory_info;
        int ret;

        if (kexec_purgatory_size <= 0)
                return -EINVAL;

        if (kexec_purgatory_size < sizeof(Elf_Ehdr))
                return -ENOEXEC;

        pi->ehdr = (Elf_Ehdr *)kexec_purgatory;

        if (memcmp(pi->ehdr->e_ident, ELFMAG, SELFMAG) != 0
            || pi->ehdr->e_type != ET_REL
            || !elf_check_arch(pi->ehdr)
            || pi->ehdr->e_shentsize != sizeof(Elf_Shdr))
                return -ENOEXEC;

        if (pi->ehdr->e_shoff >= kexec_purgatory_size
            || (pi->ehdr->e_shnum * sizeof(Elf_Shdr) >
            kexec_purgatory_size - pi->ehdr->e_shoff))
                return -ENOEXEC;

        ret = __kexec_load_purgatory(image, min, max, top_down);
        if (ret)
                return ret;

        ret = kexec_apply_relocations(image);
        if (ret)
                goto out;

        *load_addr = pi->purgatory_load_addr;
        return 0;
out:
        vfree(pi->sechdrs);
        vfree(pi->purgatory_buf);
        return ret;
}

static Elf_Sym *kexec_purgatory_find_symbol(struct purgatory_info *pi,
                                            const char *name)
{
        Elf_Sym *syms;
        Elf_Shdr *sechdrs;
        Elf_Ehdr *ehdr;
        int i, k;
        const char *strtab;

        if (!pi->sechdrs || !pi->ehdr)
                return NULL;

        sechdrs = pi->sechdrs;
        ehdr = pi->ehdr;

        for (i = 0; i < ehdr->e_shnum; i++) {
                if (sechdrs[i].sh_type != SHT_SYMTAB)
                        continue;

                if (sechdrs[i].sh_link >= ehdr->e_shnum)
                        /* Invalid strtab section number */
                        continue;
                strtab = (char *)sechdrs[sechdrs[i].sh_link].sh_offset;
                syms = (Elf_Sym *)sechdrs[i].sh_offset;

                /* Go through symbols for a match */
                for (k = 0; k < sechdrs[i].sh_size/sizeof(Elf_Sym); k++) {
                        if (ELF_ST_BIND(syms[k].st_info) != STB_GLOBAL)
                                continue;

                        if (strcmp(strtab + syms[k].st_name, name) != 0)
                                continue;

                        if (syms[k].st_shndx == SHN_UNDEF ||
                            syms[k].st_shndx >= ehdr->e_shnum) {
                                pr_debug("Symbol: %s has bad section index %d.\n",
                                                name, syms[k].st_shndx);
                                return NULL;
                        }

                        /* Found the symbol we are looking for */
                        return &syms[k];
                }
        }

        return NULL;
}

void *kexec_purgatory_get_symbol_addr(struct kimage *image, const char *name)
{
        struct purgatory_info *pi = &image->purgatory_info;
        Elf_Sym *sym;
        Elf_Shdr *sechdr;

        sym = kexec_purgatory_find_symbol(pi, name);
        if (!sym)
                return ERR_PTR(-EINVAL);

        sechdr = &pi->sechdrs[sym->st_shndx];

        /*
         * Returns the address where symbol will finally be loaded after
         * kexec_load_segment()
         */
        return (void *)(sechdr->sh_addr + sym->st_value);
}

/*
 * Get or set value of a symbol. If "get_value" is true, symbol value is
 * returned in buf otherwise symbol value is set based on value in buf.
 */
int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name,
                                   void *buf, unsigned int size, bool get_value)
{
        Elf_Sym *sym;
        Elf_Shdr *sechdrs;
        struct purgatory_info *pi = &image->purgatory_info;
        char *sym_buf;

        sym = kexec_purgatory_find_symbol(pi, name);
        if (!sym)
                return -EINVAL;

        if (sym->st_size != size) {
                pr_err("symbol %s size mismatch: expected %lu actual %u\n",
                       name, (unsigned long)sym->st_size, size);
                return -EINVAL;
        }

        sechdrs = pi->sechdrs;

        if (sechdrs[sym->st_shndx].sh_type == SHT_NOBITS) {
                pr_err("symbol %s is in a bss section. Cannot %s\n", name,
                       get_value ? "get" : "set");
                return -EINVAL;
        }

        sym_buf = (unsigned char *)sechdrs[sym->st_shndx].sh_offset +
                                        sym->st_value;

        if (get_value)
                memcpy((void *)buf, sym_buf, size);
        else
                memcpy((void *)sym_buf, buf, size);

        return 0;
}

/*
 * 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
        {
                kexec_in_progress = true;
                kernel_restart_prepare(NULL);
                migrate_to_reboot_cpu();

                /*
                 * migrate_to_reboot_cpu() disables CPU hotplug assuming that
                 * no further code needs to use CPU hotplug (which is true in
                 * the reboot case). However, the kexec path depends on using
                 * CPU hotplug again; so re-enable it here.
                 */
                cpu_hotplug_enable();
                pr_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;
}