kexec.c

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

#include <linux/capability.h>
#include <linux/mm.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/kexec.h>
#include <linux/mutex.h>
#include <linux/list.h>
#include <linux/highmem.h>
#include <linux/syscalls.h>
#include <linux/reboot.h>
#include <linux/ioport.h>
#include <linux/hardirq.h>
#include <linux/elf.h>
#include <linux/elfcore.h>
#include <linux/utsname.h>
#include <linux/numa.h>
#include <linux/suspend.h>
#include <linux/device.h>
#include <linux/freezer.h>
#include <linux/pm.h>
#include <linux/cpu.h>
#include <linux/console.h>
#include <linux/vmalloc.h>
#include <linux/swap.h>
#include <linux/syscore_ops.h>

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

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

/* vmcoreinfo stuff */
static unsigned char vmcoreinfo_data[VMCOREINFO_BYTES];
u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
size_t vmcoreinfo_size;
size_t vmcoreinfo_max_size = sizeof(vmcoreinfo_data);

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

int kexec_should_crash(struct task_struct *p)
{
    if (in_interrupt() || !p->pid || is_global_init(p) || panic_on_oops)
        return 1;
    return 0;
}

/*
 * When kexec transitions to the new kernel there is a one-to-one
 * mapping between physical and virtual addresses.  On processors
 * where you can disable the MMU this is trivial, and easy.  For
 * others it is still a simple predictable page table to setup.
 *
 * In that environment kexec copies the new kernel to its final
 * resting place.  This means I can only support memory whose
 * physical address can fit in an unsigned long.  In particular
 * addresses where (pfn << PAGE_SHIFT) > ULONG_MAX cannot be handled.
 * If the assembly stub has more restrictive requirements
 * KEXEC_SOURCE_MEMORY_LIMIT and KEXEC_DEST_MEMORY_LIMIT can be
 * defined more restrictively in <asm/kexec.h>.
 *
 * The code for the transition from the current kernel to the
 * the new kernel is placed in the control_code_buffer, whose size
 * is given by KEXEC_CONTROL_PAGE_SIZE.  In the best case only a single
 * page of memory is necessary, but some architectures require more.
 * Because this memory must be identity mapped in the transition from
 * virtual to physical addresses it must live in the range
 * 0 - TASK_SIZE, as only the user space mappings are arbitrarily
 * modifiable.
 *
 * The assembly stub in the control code buffer is passed a linked list
 * of descriptor pages detailing the source pages of the new kernel,
 * and the destination addresses of those source pages.  As this data
 * structure is not used in the context of the current OS, it must
 * be self-contained.
 *
 * The code has been made to work with highmem pages and will use a
 * destination page in its final resting place (if it happens
 * to allocate it).  The end product of this is that most of the
 * physical address space, and most of RAM can be used.
 *
 * Future directions include:
 *  - allocating a page table with the control code buffer identity
 *    mapped, to simplify machine_kexec and make kexec_on_panic more
 *    reliable.
 */

/*
 * KIMAGE_NO_DEST is an impossible destination address..., for
 * allocating pages whose destination address we do not care about.
 */
#define KIMAGE_NO_DEST (-1UL)

static int kimage_is_destination_range(struct kimage *image,
                       unsigned long start, unsigned long end);
static struct page *kimage_alloc_page(struct kimage *image,
                       gfp_t gfp_mask,
                       unsigned long dest);

static int do_kimage_alloc(struct kimage **rimage, unsigned long entry,
                        unsigned long nr_segments,
                            struct kexec_segment __user *segments)
{
    size_t segment_bytes;
    struct kimage *image;
    unsigned long i;
    int result;

    /* Allocate a controlling structure */
    result = -ENOMEM;
    image = kzalloc(sizeof(*image), GFP_KERNEL);
    if (!image)
        goto out;

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

    /* Initialize the list of control pages */
    INIT_LIST_HEAD(&image->control_pages);

    /* Initialize the list of destination pages */
    INIT_LIST_HEAD(&image->dest_pages);

    /* Initialize the list of unusable pages */
    INIT_LIST_HEAD(&image->unuseable_pages);

    /* Read in the segments */
    image->nr_segments = nr_segments;
    segment_bytes = nr_segments * sizeof(*segments);
    result = copy_from_user(image->segment, segments, segment_bytes);
    if (result) {
        result = -EFAULT;
        goto out;
    }

    /*
     * Verify we have good destination addresses.  The caller is
     * responsible for making certain we don't attempt to load
     * the new image into invalid or reserved areas of RAM.  This
     * just verifies it is an address we can use.
     *
     * Since the kernel does everything in page size chunks ensure
     * the destination addresses are page aligned.  Too many
     * special cases crop of when we don't do this.  The most
     * insidious is getting overlapping destination addresses
     * simply because addresses are changed to page size
     * granularity.
     */
    result = -EADDRNOTAVAIL;
    for (i = 0; i < nr_segments; i++) {
        unsigned long mstart, mend;

        mstart = image->segment[i].mem;
        mend   = mstart + image->segment[i].memsz;
        if ((mstart & ~PAGE_MASK) || (mend & ~PAGE_MASK))
            goto out;
        if (mend >= KEXEC_DESTINATION_MEMORY_LIMIT)
            goto out;
    }

    /* Verify our destination addresses do not overlap.
     * If we alloed overlapping destination addresses
     * through very weird things can happen with no
     * easy explanation as one segment stops on another.
     */
    result = -EINVAL;
    for (i = 0; i < nr_segments; i++) {
        unsigned long mstart, mend;
        unsigned long j;

        mstart = image->segment[i].mem;
        mend   = mstart + image->segment[i].memsz;
        for (j = 0; j < i; j++) {
            unsigned long pstart, pend;
            pstart = image->segment[j].mem;
            pend   = pstart + image->segment[j].memsz;
            /* Do the segments overlap ? */
            if ((mend > pstart) && (mstart < pend))
                goto out;
        }
    }

    /* Ensure our buffer sizes are strictly less than
     * our memory sizes.  This should always be the case,
     * and it is easier to check up front than to be surprised
     * later on.
     */
    result = -EINVAL;
    for (i = 0; i < nr_segments; i++) {
        if (image->segment[i].bufsz > image->segment[i].memsz)
            goto out;
    }

    result = 0;
out:
    if (result == 0)
        *rimage = image;
    else
        kfree(image);

    return result;

}

static int kimage_normal_alloc(struct kimage **rimage, unsigned long entry,
                unsigned long nr_segments,
                struct kexec_segment __user *segments)
{
    int result;
    struct kimage *image;

    /* Allocate and initialize a controlling structure */
    image = NULL;
    result = do_kimage_alloc(&image, entry, nr_segments, segments);
    if (result)
        goto out;

    *rimage = image;

    /*
     * Find a location for the control code buffer, and add it
     * the vector of segments so that it's pages will also be
     * counted as destination pages.
     */
    result = -ENOMEM;
    image->control_code_page = kimage_alloc_control_pages(image,
                       get_order(KEXEC_CONTROL_PAGE_SIZE));
    if (!image->control_code_page) {
        printk(KERN_ERR "Could not allocate control_code_buffer\n");
        goto out;
    }

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

    result = 0;
 out:
    if (result == 0)
        *rimage = image;
    else
        kfree(image);

    return result;
}

static int kimage_crash_alloc(struct kimage **rimage, unsigned long entry,
                unsigned long nr_segments,
                struct kexec_segment __user *segments)
{
    int result;
    struct kimage *image;
    unsigned long i;

    image = NULL;
    /* Verify we have a valid entry point */
    if ((entry < crashk_res.start) || (entry > crashk_res.end)) {
        result = -EADDRNOTAVAIL;
        goto out;
    }

    /* Allocate and initialize a controlling structure */
    result = do_kimage_alloc(&image, entry, nr_segments, segments);
    if (result)
        goto out;

    /* Enable the special crash kernel control page
     * allocation policy.
     */
    image->control_page = crashk_res.start;
    image->type = KEXEC_TYPE_CRASH;

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

        mstart = image->segment[i].mem;
        mend = mstart + image->segment[i].memsz - 1;
        /* Ensure we are within the crash kernel limits */
        if ((mstart < crashk_res.start) || (mend > crashk_res.end))
            goto out;
    }

    /*
     * Find a location for the control code buffer, and add
     * the vector of segments so that it's pages will also be
     * counted as destination pages.
     */
    result = -ENOMEM;
    image->control_code_page = kimage_alloc_control_pages(image,
                       get_order(KEXEC_CONTROL_PAGE_SIZE));
    if (!image->control_code_page) {
        printk(KERN_ERR "Could not allocate control_code_buffer\n");
        goto out;
    }

    result = 0;
out:
    if (result == 0)
        *rimage = image;
    else
        kfree(image);

    return result;
}

static int kimage_is_destination_range(struct kimage *image,
                    unsigned long start,
                    unsigned long end)
{
    unsigned long i;

    for (i = 0; i < image->nr_segments; i++) {
        unsigned long mstart, mend;

        mstart = image->segment[i].mem;
        mend = mstart + image->segment[i].memsz;
        if ((end > mstart) && (start < mend))
            return 1;
    }

    return 0;
}

static struct page *kimage_alloc_pages(gfp_t gfp_mask, unsigned int order)
{
    struct page *pages;

    pages = alloc_pages(gfp_mask, order);
    if (pages) {
        unsigned int count, i;
        pages->mapping = NULL;
        set_page_private(pages, order);
        count = 1 << order;
        for (i = 0; i < count; i++)
            SetPageReserved(pages + i);
    }

    return pages;
}

static void kimage_free_pages(struct page *page)
{
    unsigned int order, count, i;

    order = page_private(page);
    count = 1 << order;
    for (i = 0; i < count; i++)
        ClearPageReserved(page + i);
    __free_pages(page, order);
}

static void kimage_free_page_list(struct list_head *list)
{
    struct list_head *pos, *next;

    list_for_each_safe(pos, next, list) {
        struct page *page;

        page = list_entry(pos, struct page, lru);
        list_del(&page->lru);
        kimage_free_pages(page);
    }
}

static struct page *kimage_alloc_normal_control_pages(struct kimage *image,
                            unsigned int order)
{
    /* Control pages are special, they are the intermediaries
     * that are needed while we copy the rest of the pages
     * to their final resting place.  As such they must
     * not conflict with either the destination addresses
     * or memory the kernel is already using.
     *
     * The only case where we really need more than one of
     * these are for architectures where we cannot disable
     * the MMU and must instead generate an identity mapped
     * page table for all of the memory.
     *
     * At worst this runs in O(N) of the image size.
     */
    struct list_head extra_pages;
    struct page *pages;
    unsigned int count;

    count = 1 << order;
    INIT_LIST_HEAD(&extra_pages);

    /* Loop while I can allocate a page and the page allocated
     * is a destination page.
     */
    do {
        unsigned long pfn, epfn, addr, eaddr;

        pages = kimage_alloc_pages(GFP_KERNEL, order);
        if (!pages)
            break;
        pfn   = page_to_pfn(pages);
        epfn  = pfn + count;
        addr  = pfn << PAGE_SHIFT;
        eaddr = epfn << PAGE_SHIFT;
        if ((epfn >= (KEXEC_CONTROL_MEMORY_LIMIT >> PAGE_SHIFT)) ||
                  kimage_is_destination_range(image, addr, eaddr)) {
            list_add(&pages->lru, &extra_pages);
            pages = NULL;
        }
    } while (!pages);

    if (pages) {
        /* Remember the allocated page... */
        list_add(&pages->lru, &image->control_pages);

        /* Because the page is already in it's destination
         * location we will never allocate another page at
         * that address.  Therefore kimage_alloc_pages
         * will not return it (again) and we don't need
         * to give it an entry in image->segment[].
         */
    }
    /* Deal with the destination pages I have inadvertently allocated.
     *
     * Ideally I would convert multi-page allocations into single
     * page allocations, and add everything to image->dest_pages.
     *
     * For now it is simpler to just free the pages.
     */
    kimage_free_page_list(&extra_pages);

    return pages;
}

static struct page *kimage_alloc_crash_control_pages(struct kimage *image,
                              unsigned int order)
{
    /* Control pages are special, they are the intermediaries
     * that are needed while we copy the rest of the pages
     * to their final resting place.  As such they must
     * not conflict with either the destination addresses
     * or memory the kernel is already using.
     *
     * Control pages are also the only pags we must allocate
     * when loading a crash kernel.  All of the other pages
     * are specified by the segments and we just memcpy
     * into them directly.
     *
     * The only case where we really need more than one of
     * these are for architectures where we cannot disable
     * the MMU and must instead generate an identity mapped
     * page table for all of the memory.
     *
     * Given the low demand this implements a very simple
     * allocator that finds the first hole of the appropriate
     * size in the reserved memory region, and allocates all
     * of the memory up to and including the hole.
     */
    unsigned long hole_start, hole_end, size;
    struct page *pages;

    pages = NULL;
    size = (1 << order) << PAGE_SHIFT;
    hole_start = (image->control_page + (size - 1)) & ~(size - 1);
    hole_end   = hole_start + size - 1;
    while (hole_end <= crashk_res.end) {
        unsigned long i;

        if (hole_end > KEXEC_CRASH_CONTROL_MEMORY_LIMIT)
            break;
        if (hole_end > crashk_res.end)
            break;
        /* See if I overlap any of the segments */
        for (i = 0; i < image->nr_segments; i++) {
            unsigned long mstart, mend;

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

    return pages;
}


struct page *kimage_alloc_control_pages(struct kimage *image,
                     unsigned int order)
{
    struct page *pages = NULL;

    switch (image->type) {
    case KEXEC_TYPE_DEFAULT:
        pages = kimage_alloc_normal_control_pages(image, order);
        break;
    case KEXEC_TYPE_CRASH:
        pages = kimage_alloc_crash_control_pages(image, order);
        break;
    }

    return pages;
}

static int kimage_add_entry(struct kimage *image, kimage_entry_t entry)
{
    if (*image->entry != 0)
        image->entry++;

    if (image->entry == image->last_entry) {
        kimage_entry_t *ind_page;
        struct page *page;

        page = kimage_alloc_page(image, GFP_KERNEL, KIMAGE_NO_DEST);
        if (!page)
            return -ENOMEM;

        ind_page = page_address(page);
        *image->entry = virt_to_phys(ind_page) | IND_INDIRECTION;
        image->entry = ind_page;
        image->last_entry = ind_page +
                      ((PAGE_SIZE/sizeof(kimage_entry_t)) - 1);
    }
    *image->entry = entry;
    image->entry++;
    *image->entry = 0;

    return 0;
}

static int kimage_set_destination(struct kimage *image,
                   unsigned long destination)
{
    int result;

    destination &= PAGE_MASK;
    result = kimage_add_entry(image, destination | IND_DESTINATION);
    if (result == 0)
        image->destination = destination;

    return result;
}


static int kimage_add_page(struct kimage *image, unsigned long page)
{
    int result;

    page &= PAGE_MASK;
    result = kimage_add_entry(image, page | IND_SOURCE);
    if (result == 0)
        image->destination += PAGE_SIZE;

    return result;
}


static void kimage_free_extra_pages(struct kimage *image)
{
    /* Walk through and free any extra destination pages I may have */
    kimage_free_page_list(&image->dest_pages);

    /* Walk through and free any unusable pages I have cached */
    kimage_free_page_list(&image->unuseable_pages);

}
static void kimage_terminate(struct kimage *image)
{
    if (*image->entry != 0)
        image->entry++;

    *image->entry = IND_DONE;
}

#define for_each_kimage_entry(image, ptr, entry) \
    for (ptr = &image->head; (entry = *ptr) && !(entry & IND_DONE); \
        ptr = (entry & IND_INDIRECTION)? \
            phys_to_virt((entry & PAGE_MASK)): ptr +1)

static void kimage_free_entry(kimage_entry_t entry)
{
    struct page *page;

    page = pfn_to_page(entry >> PAGE_SHIFT);
    kimage_free_pages(page);
}

static void kimage_free(struct kimage *image)
{
    kimage_entry_t *ptr, entry;
    kimage_entry_t ind = 0;

    if (!image)
        return;

    kimage_free_extra_pages(image);
    for_each_kimage_entry(image, ptr, entry) {
        if (entry & IND_INDIRECTION) {
            /* Free the previous indirection page */
            if (ind & IND_INDIRECTION)
                kimage_free_entry(ind);
            /* Save this indirection page until we are
             * done with it.
             */
            ind = entry;
        }
        else if (entry & IND_SOURCE)
            kimage_free_entry(entry);
    }
    /* Free the final indirection page */
    if (ind & IND_INDIRECTION)
        kimage_free_entry(ind);

    /* Handle any machine specific cleanup */
    machine_kexec_cleanup(image);

    /* Free the kexec control pages... */
    kimage_free_page_list(&image->control_pages);
    kfree(image);
}

static kimage_entry_t *kimage_dst_used(struct kimage *image,
                    unsigned long page)
{
    kimage_entry_t *ptr, entry;
    unsigned long destination = 0;

    for_each_kimage_entry(image, ptr, entry) {
        if (entry & IND_DESTINATION)
            destination = entry & PAGE_MASK;
        else if (entry & IND_SOURCE) {
            if (page == destination)
                return ptr;
            destination += PAGE_SIZE;
        }
    }

    return NULL;
}

static struct page *kimage_alloc_page(struct kimage *image,
                    gfp_t gfp_mask,
                    unsigned long destination)
{
    /*
     * Here we implement safeguards to ensure that a source page
     * is not copied to its destination page before the data on
     * the destination page is no longer useful.
     *
     * To do this we maintain the invariant that a source page is
     * either its own destination page, or it is not a
     * destination page at all.
     *
     * That is slightly stronger than required, but the proof
     * that no problems will not occur is trivial, and the
     * implementation is simply to verify.
     *
     * When allocating all pages normally this algorithm will run
     * in O(N) time, but in the worst case it will run in O(N^2)
     * time.   If the runtime is a problem the data structures can
     * be fixed.
     */
    struct page *page;
    unsigned long addr;

    /*
     * Walk through the list of destination pages, and see if I
     * have a match.
     */
    list_for_each_entry(page, &image->dest_pages, lru) {
        addr = page_to_pfn(page) << PAGE_SHIFT;
        if (addr == destination) {
            list_del(&page->lru);
            return page;
        }
    }
    page = NULL;
    while (1) {
        kimage_entry_t *old;

        /* Allocate a page, if we run out of memory give up */
        page = kimage_alloc_pages(gfp_mask, 0);
        if (!page)
            return NULL;
        /* If the page cannot be used file it away */
        if (page_to_pfn(page) >
                (KEXEC_SOURCE_MEMORY_LIMIT >> PAGE_SHIFT)) {
            list_add(&page->lru, &image->unuseable_pages);
            continue;
        }
        addr = page_to_pfn(page) << PAGE_SHIFT;

        /* If it is the destination page we want use it */
        if (addr == destination)
            break;

        /* If the page is not a destination page use it */
        if (!kimage_is_destination_range(image, addr,
                          addr + PAGE_SIZE))
            break;

        /*
         * I know that the page is someones destination page.
         * See if there is already a source page for this
         * destination page.  And if so swap the source pages.
         */
        old = kimage_dst_used(image, addr);
        if (old) {
            /* If so move it */
            unsigned long old_addr;
            struct page *old_page;

            old_addr = *old & PAGE_MASK;
            old_page = pfn_to_page(old_addr >> PAGE_SHIFT);
            copy_highpage(page, old_page);
            *old = addr | (*old & ~PAGE_MASK);

            /* The old page I have found cannot be a
             * destination page, so return it if it's
             * gfp_flags honor the ones passed in.
             */
            if (!(gfp_mask & __GFP_HIGHMEM) &&
                PageHighMem(old_page)) {
                kimage_free_pages(old_page);
                continue;
            }
            addr = old_addr;
            page = old_page;
            break;
        }
        else {
            /* Place the page on the destination list I
             * will use it later.
             */
            list_add(&page->lru, &image->dest_pages);
        }
    }

    return page;
}

static int kimage_load_normal_segment(struct kimage *image,
                     struct kexec_segment *segment)
{
    unsigned long maddr;
    unsigned long ubytes, mbytes;
    int result;
    unsigned char __user *buf;

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

    result = kimage_set_destination(image, maddr);
    if (result < 0)
        goto out;

    while (mbytes) {
        struct page *page;
        char *ptr;
        size_t uchunk, mchunk;

        page = kimage_alloc_page(image, GFP_HIGHUSER, maddr);
        if (!page) {
            result  = -ENOMEM;
            goto out;
        }
        result = kimage_add_page(image, page_to_pfn(page)
                                << PAGE_SHIFT);
        if (result < 0)
            goto out;

        ptr = kmap(page);
        /* Start with a clear page */
        clear_page(ptr);
        ptr += maddr & ~PAGE_MASK;
        mchunk = PAGE_SIZE - (maddr & ~PAGE_MASK);
        if (mchunk > mbytes)
            mchunk = mbytes;

        uchunk = mchunk;
        if (uchunk > ubytes)
            uchunk = ubytes;

        result = copy_from_user(ptr, buf, uchunk);
        kunmap(page);
        if (result) {
            result = -EFAULT;
            goto out;
        }
        ubytes -= uchunk;
        maddr  += mchunk;
        buf    += mchunk;
        mbytes -= mchunk;
    }
out:
    return result;
}

static int kimage_load_crash_segment(struct kimage *image,
                    struct kexec_segment *segment)
{
    /* For crash dumps kernels we simply copy the data from
     * user space to it's destination.
     * We do things a page at a time for the sake of kmap.
     */
    unsigned long maddr;
    unsigned long ubytes, mbytes;
    int result;
    unsigned char __user *buf;

    result = 0;
    buf = segment->buf;
    ubytes = segment->bufsz;
    mbytes = segment->memsz;
    maddr = segment->mem;
    while (mbytes) {
        struct page *page;
        char *ptr;
        size_t uchunk, mchunk;

        page = pfn_to_page(maddr >> PAGE_SHIFT);
        if (!page) {
            result  = -ENOMEM;
            goto out;
        }
        ptr = kmap(page);
        ptr += maddr & ~PAGE_MASK;
        mchunk = PAGE_SIZE - (maddr & ~PAGE_MASK);
        if (mchunk > mbytes)
            mchunk = mbytes;

        uchunk = mchunk;
        if (uchunk > ubytes) {
            uchunk = ubytes;
            /* Zero the trailing part of the page */
            memset(ptr + uchunk, 0, mchunk - uchunk);
        }
        result = copy_from_user(ptr, buf, uchunk);
        kexec_flush_icache_page(page);
        kunmap(page);
        if (result) {
            result = -EFAULT;
            goto out;
        }
        ubytes -= uchunk;
        maddr  += mchunk;
        buf    += mchunk;
        mbytes -= mchunk;
    }
out:
    return result;
}

static int kimage_load_segment(struct kimage *image,
                struct kexec_segment *segment)
{
    int result = -ENOMEM;

    switch (image->type) {
    case KEXEC_TYPE_DEFAULT:
        result = kimage_load_normal_segment(image, segment);
        break;
    case KEXEC_TYPE_CRASH:
        result = kimage_load_crash_segment(image, segment);
        break;
    }

    return result;
}

/*
 * Exec Kernel system call: for obvious reasons only root may call it.
 *
 * This call breaks up into three pieces.
 * - A generic part which loads the new kernel from the current
 *   address space, and very carefully places the data in the
 *   allocated pages.
 *
 * - A generic part that interacts with the kernel and tells all of
 *   the devices to shut down.  Preventing on-going dmas, and placing
 *   the devices in a consistent state so a later kernel can
 *   reinitialize them.
 *
 * - A machine specific part that includes the syscall number
 *   and the copies the image to it's final destination.  And
 *   jumps into the image at entry.
 *
 * kexec does not sync, or unmount filesystems so if you need
 * that to happen you need to do that yourself.
 */
struct kimage *kexec_image;
struct kimage *kexec_crash_image;

static DEFINE_MUTEX(kexec_mutex);

SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
        struct kexec_segment __user *, segments, unsigned long, flags)
{
    struct kimage **dest_image, *image;
    int result;

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

    /*
     * Verify we have a legal set of flags
     * This leaves us room for future extensions.
     */
    if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
        return -EINVAL;

    /* Verify we are on the appropriate architecture */
    if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) &&
        ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT))
        return -EINVAL;

    /* Put an artificial cap on the number
     * of segments passed to kexec_load.
     */
    if (nr_segments > KEXEC_SEGMENT_MAX)
        return -EINVAL;

    image = NULL;
    result = 0;

    /* Because we write directly to the reserved memory
     * region when loading crash kernels we need a mutex here to
     * prevent multiple crash  kernels from attempting to load
     * simultaneously, and to prevent a crash kernel from loading
     * over the top of a in use crash kernel.
     *
     * KISS: always take the mutex.
     */
    if (!mutex_trylock(&kexec_mutex))
        return -EBUSY;

    dest_image = &kexec_image;
    if (flags & KEXEC_ON_CRASH)
        dest_image = &kexec_crash_image;
    if (nr_segments > 0) {
        unsigned long i;

        /* Loading another kernel to reboot into */
        if ((flags & KEXEC_ON_CRASH) == 0)
            result = kimage_normal_alloc(&image, entry,
                            nr_segments, segments);
        /* Loading another kernel to switch to if this one crashes */
        else if (flags & KEXEC_ON_CRASH) {
            /* Free any current crash dump kernel before
             * we corrupt it.
             */
            kimage_free(xchg(&kexec_crash_image, NULL));
            result = kimage_crash_alloc(&image, entry,
                             nr_segments, segments);
            crash_map_reserved_pages();
        }
        if (result)
            goto out;

        if (flags & KEXEC_PRESERVE_CONTEXT)
            image->preserve_context = 1;
        result = machine_kexec_prepare(image);
        if (result)
            goto out;

        for (i = 0; i < nr_segments; i++) {
            result = kimage_load_segment(image, &image->segment[i]);
            if (result)
                goto out;
        }
        kimage_terminate(image);
        if (flags & KEXEC_ON_CRASH)
            crash_unmap_reserved_pages();
    }
    /* Install the new kernel, and  Uninstall the old */
    image = xchg(dest_image, image);

out:
    mutex_unlock(&kexec_mutex);
    kimage_free(image);

    return result;
}

/*
 * Add and remove page tables for crashkernel memory
 *
 * Provide an empty default implementation here -- architecture
 * code may override this
 */
void __weak crash_map_reserved_pages(void)
{}

void __weak crash_unmap_reserved_pages(void)
{}

#ifdef CONFIG_COMPAT
asmlinkage long compat_sys_kexec_load(unsigned long entry,
                unsigned long nr_segments,
                struct compat_kexec_segment __user *segments,
                unsigned long flags)
{
    struct compat_kexec_segment in;
    struct kexec_segment out, __user *ksegments;
    unsigned long i, result;

    /* Don't allow clients that don't understand the native
     * architecture to do anything.
     */
    if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)
        return -EINVAL;

    if (nr_segments > KEXEC_SEGMENT_MAX)
        return -EINVAL;

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

        out.buf   = compat_ptr(in.buf);
        out.bufsz = in.bufsz;
        out.mem   = in.mem;
        out.memsz = in.memsz;

        result = copy_to_user(&ksegments[i], &out, sizeof(out));
        if (result)
            return -EFAULT;
    }

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

void crash_kexec(struct pt_regs *regs)
{
    /* Take the kexec_mutex here to prevent sys_kexec_load
     * running on one cpu from replacing the crash kernel
     * we are using after a panic on a different cpu.
     *
     * If the crash kernel was not located in a fixed area
     * of memory the xchg(&kexec_crash_image) would be
     * sufficient.  But since I reuse the memory...
     */
    if (mutex_trylock(&kexec_mutex)) {
        if (kexec_crash_image) {
            struct pt_regs fixed_regs;

            crash_setup_regs(&fixed_regs, regs);
            crash_save_vmcoreinfo();
            machine_crash_shutdown(&fixed_regs);
            machine_kexec(kexec_crash_image);
        }
        mutex_unlock(&kexec_mutex);
    }
}

size_t crash_get_memory_size(void)
{
    size_t size = 0;
    mutex_lock(&kexec_mutex);
    if (crashk_res.end != crashk_res.start)
        size = resource_size(&crashk_res);
    mutex_unlock(&kexec_mutex);
    return size;
}

void __weak crash_free_reserved_phys_range(unsigned long begin,
                       unsigned long end)
{
    unsigned long addr;

    for (addr = begin; addr < end; addr += PAGE_SIZE) {
        ClearPageReserved(pfn_to_page(addr >> PAGE_SHIFT));
        init_page_count(pfn_to_page(addr >> PAGE_SHIFT));
        free_page((unsigned long)__va(addr));
        totalram_pages++;
    }
}

int crash_shrink_memory(unsigned long new_size)
{
    int ret = 0;
    unsigned long start, end;
    unsigned long old_size;
    struct resource *ram_res;

    mutex_lock(&kexec_mutex);

    if (kexec_crash_image) {
        ret = -ENOENT;
        goto unlock;
    }
    start = crashk_res.start;
    end = crashk_res.end;
    old_size = (end == 0) ? 0 : end - start + 1;
    if (new_size >= old_size) {
        ret = (new_size == old_size) ? 0 : -EINVAL;
        goto unlock;
    }

    ram_res = kzalloc(sizeof(*ram_res), GFP_KERNEL);
    if (!ram_res) {
        ret = -ENOMEM;
        goto unlock;
    }

    start = roundup(start, KEXEC_CRASH_MEM_ALIGN);
    end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN);

    crash_map_reserved_pages();
    crash_free_reserved_phys_range(end, crashk_res.end);

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

    ram_res->start = end;
    ram_res->end = crashk_res.end;
    ram_res->flags = IORESOURCE_BUSY | IORESOURCE_MEM;
    ram_res->name = "System RAM";

    crashk_res.end = end - 1;

    insert_resource(&iomem_resource, ram_res);
    crash_unmap_reserved_pages();

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

static u32 *append_elf_note(u32 *buf, char *name, unsigned type, void *data,
                size_t data_len)
{
    struct elf_note note;

    note.n_namesz = strlen(name) + 1;
    note.n_descsz = data_len;
    note.n_type   = type;
    memcpy(buf, &note, sizeof(note));
    buf += (sizeof(note) + 3)/4;
    memcpy(buf, name, note.n_namesz);
    buf += (note.n_namesz + 3)/4;
    memcpy(buf, data, note.n_descsz);
    buf += (note.n_descsz + 3)/4;

    return buf;
}

static void final_note(u32 *buf)
{
    struct elf_note note;

    note.n_namesz = 0;
    note.n_descsz = 0;
    note.n_type   = 0;
    memcpy(buf, &note, sizeof(note));
}

void crash_save_cpu(struct pt_regs *regs, int cpu)
{
    struct elf_prstatus prstatus;
    u32 *buf;

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

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

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


/*
 * parsing the "crashkernel" commandline
 *
 * this code is intended to be called from architecture specific code
 */


/*
 * This function parses command lines in the format
 *
 *   crashkernel=ramsize-range:size[,...][@offset]
 *
 * The function returns 0 on success and -EINVAL on failure.
 */
static int __init parse_crashkernel_mem(char            *cmdline,
                    unsigned long long  system_ram,
                    unsigned long long  *crash_size,
                    unsigned long long  *crash_base)
{
    char *cur = cmdline, *tmp;

    /* for each entry of the comma-separated list */
    do {
        unsigned long long start, end = ULLONG_MAX, size;

        /* get the start of the range */
        start = memparse(cur, &tmp);
        if (cur == tmp) {
            pr_warning("crashkernel: Memory value expected\n");
            return -EINVAL;
        }
        cur = tmp;
        if (*cur != '-') {
            pr_warning("crashkernel: '-' expected\n");
            return -EINVAL;
        }
        cur++;

        /* if no ':' is here, than we read the end */
        if (*cur != ':') {
            end = memparse(cur, &tmp);
            if (cur == tmp) {
                pr_warning("crashkernel: Memory "
                        "value expected\n");
                return -EINVAL;
            }
            cur = tmp;
            if (end <= start) {
                pr_warning("crashkernel: end <= start\n");
                return -EINVAL;
            }
        }

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

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

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

    if (*crash_size > 0) {
        while (*cur && *cur != ' ' && *cur != '@')
            cur++;
        if (*cur == '@') {
            cur++;
            *crash_base = memparse(cur, &tmp);
            if (cur == tmp) {
                pr_warning("Memory value expected "
                        "after '@'\n");
                return -EINVAL;
            }
        }
    }

    return 0;
}

/*
 * That function parses "simple" (old) crashkernel command lines like
 *
 *  crashkernel=size[@offset]
 *
 * It returns 0 on success and -EINVAL on failure.
 */
static int __init parse_crashkernel_simple(char         *cmdline,
                       unsigned long long   *crash_size,
                       unsigned long long   *crash_base)
{
    char *cur = cmdline;

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

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

    return 0;
}

/*
 * That function is the entry point for command line parsing and should be
 * called from the arch-specific code.
 */
int __init parse_crashkernel(char        *cmdline,
                 unsigned long long system_ram,
                 unsigned long long *crash_size,
                 unsigned long long *crash_base)
{
    char    *p = cmdline, *ck_cmdline = NULL;
    char    *first_colon, *first_space;

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

    /* find crashkernel and use the last one if there are more */
    p = strstr(p, "crashkernel=");
    while (p) {
        ck_cmdline = p;
        p = strstr(p+1, "crashkernel=");
    }

    if (!ck_cmdline)
        return -EINVAL;

    ck_cmdline += 12; /* strlen("crashkernel=") */

    /*
     * if the commandline contains a ':', then that's the extended
     * syntax -- if not, it must be the classic syntax
     */
    first_colon = strchr(ck_cmdline, ':');
    first_space = strchr(ck_cmdline, ' ');
    if (first_colon && (!first_space || first_colon < first_space))
        return parse_crashkernel_mem(ck_cmdline, system_ram,
                crash_size, crash_base);
    else
        return parse_crashkernel_simple(ck_cmdline, crash_size,
                crash_base);

    return 0;
}


static void update_vmcoreinfo_note(void)
{
    u32 *buf = vmcoreinfo_note;

    if (!vmcoreinfo_size)
        return;
    buf = append_elf_note(buf, VMCOREINFO_NOTE_NAME, 0, vmcoreinfo_data,
                  vmcoreinfo_size);
    final_note(buf);
}

void crash_save_vmcoreinfo(void)
{
    vmcoreinfo_append_str("CRASHTIME=%ld\n", get_seconds());
    update_vmcoreinfo_note();
}

void vmcoreinfo_append_str(const char *fmt, ...)
{
    va_list args;
    char buf[0x50];
    int r;

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

    if (r + vmcoreinfo_size > vmcoreinfo_max_size)
        r = vmcoreinfo_max_size - vmcoreinfo_size;

    memcpy(&vmcoreinfo_data[vmcoreinfo_size], buf, r);

    vmcoreinfo_size += r;
}

/*
 * provide an empty default implementation here -- architecture
 * code may override this
 */
void __attribute__ ((weak)) arch_crash_save_vmcoreinfo(void)
{}

unsigned long __attribute__ ((weak)) paddr_vmcoreinfo_note(void)
{
    return __pa((unsigned long)(char *)&vmcoreinfo_note);
}

static int __init crash_save_vmcoreinfo_init(void)
{
    VMCOREINFO_OSRELEASE(init_uts_ns.name.release);
    VMCOREINFO_PAGESIZE(PAGE_SIZE);

    VMCOREINFO_SYMBOL(init_uts_ns);
    VMCOREINFO_SYMBOL(node_online_map);
#ifdef CONFIG_MMU
    VMCOREINFO_SYMBOL(swapper_pg_dir);
#endif
    VMCOREINFO_SYMBOL(_stext);
    VMCOREINFO_SYMBOL(vmlist);

#ifndef CONFIG_NEED_MULTIPLE_NODES
    VMCOREINFO_SYMBOL(mem_map);
    VMCOREINFO_SYMBOL(contig_page_data);
#endif
#ifdef CONFIG_SPARSEMEM
    VMCOREINFO_SYMBOL(mem_section);
    VMCOREINFO_LENGTH(mem_section, NR_SECTION_ROOTS);
    VMCOREINFO_STRUCT_SIZE(mem_section);
    VMCOREINFO_OFFSET(mem_section, section_mem_map);
#endif
    VMCOREINFO_STRUCT_SIZE(page);
    VMCOREINFO_STRUCT_SIZE(pglist_data);
    VMCOREINFO_STRUCT_SIZE(zone);
    VMCOREINFO_STRUCT_SIZE(free_area);
    VMCOREINFO_STRUCT_SIZE(list_head);
    VMCOREINFO_SIZE(nodemask_t);
    VMCOREINFO_OFFSET(page, flags);
    VMCOREINFO_OFFSET(page, _count);
    VMCOREINFO_OFFSET(page, mapping);
    VMCOREINFO_OFFSET(page, lru);
    VMCOREINFO_OFFSET(pglist_data, node_zones);
    VMCOREINFO_OFFSET(pglist_data, nr_zones);
#ifdef CONFIG_FLAT_NODE_MEM_MAP
    VMCOREINFO_OFFSET(pglist_data, node_mem_map);
#endif
    VMCOREINFO_OFFSET(pglist_data, node_start_pfn);
    VMCOREINFO_OFFSET(pglist_data, node_spanned_pages);
    VMCOREINFO_OFFSET(pglist_data, node_id);
    VMCOREINFO_OFFSET(zone, free_area);
    VMCOREINFO_OFFSET(zone, vm_stat);
    VMCOREINFO_OFFSET(zone, spanned_pages);
    VMCOREINFO_OFFSET(free_area, free_list);
    VMCOREINFO_OFFSET(list_head, next);
    VMCOREINFO_OFFSET(list_head, prev);
    VMCOREINFO_OFFSET(vm_struct, addr);
    VMCOREINFO_LENGTH(zone.free_area, MAX_ORDER);
    log_buf_kexec_setup();
    VMCOREINFO_LENGTH(free_area.free_list, MIGRATE_TYPES);
    VMCOREINFO_NUMBER(NR_FREE_PAGES);
    VMCOREINFO_NUMBER(PG_lru);
    VMCOREINFO_NUMBER(PG_private);
    VMCOREINFO_NUMBER(PG_swapcache);

    arch_crash_save_vmcoreinfo();
    update_vmcoreinfo_note();

    return 0;
}

module_init(crash_save_vmcoreinfo_init)

/*
 * Move into place and start executing a preloaded standalone
 * executable.  If nothing was preloaded return an error.
 */
int kernel_kexec(void)
{
    int error = 0;

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

#ifdef CONFIG_KEXEC_JUMP
    if (kexec_image->preserve_context) {
        lock_system_sleep();
        pm_prepare_console();
        error = freeze_processes();
        if (error) {
            error = -EBUSY;
            goto Restore_console;
        }
        suspend_console();
        error = dpm_suspend_start(PMSG_FREEZE);
        if (error)
            goto Resume_console;
        /* At this point, dpm_suspend_start() has been called,
         * but *not* dpm_suspend_end(). We *must* call
         * dpm_suspend_end() now.  Otherwise, drivers for
         * some devices (e.g. interrupt controllers) become
         * desynchronized with the actual state of the
         * hardware at resume time, and evil weirdness ensues.
         */
        error = dpm_suspend_end(PMSG_FREEZE);
        if (error)
            goto Resume_devices;
        error = disable_nonboot_cpus();
        if (error)
            goto Enable_cpus;
        local_irq_disable();
        error = syscore_suspend();
        if (error)
            goto Enable_irqs;
    } else
#endif
    {
        kernel_restart_prepare(NULL);
        printk(KERN_EMERG "Starting new kernel\n");
        machine_shutdown();
    }

    machine_kexec(kexec_image);

#ifdef CONFIG_KEXEC_JUMP
    if (kexec_image->preserve_context) {
        syscore_resume();
 Enable_irqs:
        local_irq_enable();
 Enable_cpus:
        enable_nonboot_cpus();
        dpm_resume_start(PMSG_RESTORE);
 Resume_devices:
        dpm_resume_end(PMSG_RESTORE);
 Resume_console:
        resume_console();
        thaw_processes();
 Restore_console:
        pm_restore_console();
        unlock_system_sleep();
    }
#endif

 Unlock:
    mutex_unlock(&kexec_mutex);
    return error;
}