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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * kexec.c - kexec system call core code.
  * Copyright (C) 2002-2004 Eric Biederman  <ebiederm@xmission.com>
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " 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/panic_notifier.h>
 #include <linux/pm.h>
 #include <linux/cpu.h>
 #include <linux/uaccess.h>
 #include <linux/io.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 <linux/objtool.h>
 #include <linux/kmsg_dump.h>
 
 #include <asm/page.h>
 #include <asm/sections.h>
 
 #include <crypto/hash.h>
 #include "kexec_internal.h"
 
 DEFINE_MUTEX(kexec_mutex);
 
 /* Per cpu memory for storing cpu states in case of system crash. */
 note_buf_t __percpu *crash_notes;
 
 /* Flag to indicate we are going to kexec a new kernel */
 bool kexec_in_progress = false;
 
 
 /* Location of the reserved area for the crash kernel */
 struct resource crashk_res = {
     .name  = "Crash kernel",
     .start = 0,
     .end   = 0,
     .flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM,
     .desc  = IORES_DESC_CRASH_KERNEL
 };
 struct resource crashk_low_res = {
     .name  = "Crash kernel",
     .start = 0,
     .end   = 0,
     .flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM,
     .desc  = IORES_DESC_CRASH_KERNEL
 };
 
 int kexec_should_crash(struct task_struct *p)
 {
     /*
      * If crash_kexec_post_notifiers is enabled, don't run
      * crash_kexec() here yet, which must be run after panic
      * notifiers in panic().
      */
     if (crash_kexec_post_notifiers)
         return 0;
     /*
      * There are 4 panic() calls in make_task_dead() path, each of which
      * corresponds to each of these 4 conditions.
      */
     if (in_interrupt() || !p->pid || is_global_init(p) || panic_on_oops)
         return 1;
     return 0;
 }
 
 int kexec_crash_loaded(void)
 {
     return !!kexec_crash_image;
 }
 EXPORT_SYMBOL_GPL(kexec_crash_loaded);
 
 /*
  * 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
  * 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)
 #define PAGE_COUNT(x) (((x) + PAGE_SIZE - 1) >> PAGE_SHIFT)
 
 static struct page *kimage_alloc_page(struct kimage *image,
                        gfp_t gfp_mask,
                        unsigned long dest);
 
 int sanity_check_segment_list(struct kimage *image)
 {
     int i;
     unsigned long nr_segments = image->nr_segments;
     unsigned long total_pages = 0;
     unsigned long nr_pages = totalram_pages();
 
     /*
      * 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.
      */
     for (i = 0; i < nr_segments; i++) {
         unsigned long mstart, mend;
 
         mstart = image->segment[i].mem;
         mend   = mstart + image->segment[i].memsz;
         if (mstart > mend)
             return -EADDRNOTAVAIL;
         if ((mstart & ~PAGE_MASK) || (mend & ~PAGE_MASK))
             return -EADDRNOTAVAIL;
         if (mend >= KEXEC_DESTINATION_MEMORY_LIMIT)
             return -EADDRNOTAVAIL;
     }
 
     /* 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.
      */
     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 -EINVAL;
         }
     }
 
     /* 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.
      */
     for (i = 0; i < nr_segments; i++) {
         if (image->segment[i].bufsz > image->segment[i].memsz)
             return -EINVAL;
     }
 
     /*
      * Verify that no more than half of memory will be consumed. If the
      * request from userspace is too large, a large amount of time will be
      * wasted allocating pages, which can cause a soft lockup.
      */
     for (i = 0; i < nr_segments; i++) {
         if (PAGE_COUNT(image->segment[i].memsz) > nr_pages / 2)
             return -EINVAL;
 
         total_pages += PAGE_COUNT(image->segment[i].memsz);
     }
 
     if (total_pages > nr_pages / 2)
         return -EINVAL;
 
     /*
      * 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) {
         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 < phys_to_boot_phys(crashk_res.start)) ||
                 (mend > phys_to_boot_phys(crashk_res.end)))
                 return -EADDRNOTAVAIL;
         }
     }
 
     return 0;
 }
 
 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;
 }
 
 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;
 
     if (fatal_signal_pending(current))
         return NULL;
     pages = alloc_pages(gfp_mask & ~__GFP_ZERO, 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);
 
         arch_kexec_post_alloc_pages(page_address(pages), count,
                         gfp_mask);
 
         if (gfp_mask & __GFP_ZERO)
             for (i = 0; i < count; i++)
                 clear_highpage(pages + i);
     }
 
     return pages;
 }
 
 static void kimage_free_pages(struct page *page)
 {
     unsigned int order, count, i;
 
     order = page_private(page);
     count = 1 << order;
 
     arch_kexec_pre_free_pages(page_address(page), count);
 
     for (i = 0; i < count; i++)
         ClearPageReserved(page + i);
     __free_pages(page, order);
 }
 
 void kimage_free_page_list(struct list_head *list)
 {
     struct page *page, *next;
 
     list_for_each_entry_safe(page, next, list, 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(KEXEC_CONTROL_MEMORY_GFP, order);
         if (!pages)
             break;
         pfn   = page_to_boot_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;
 
         cond_resched();
 
         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);
             image->control_page = hole_end;
             break;
         }
     }
 
     /* Ensure that these pages are decrypted if SME is enabled. */
     if (pages)
         arch_kexec_post_alloc_pages(page_address(pages), 1 << order, 0);
 
     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;
 }
 
 int kimage_crash_copy_vmcoreinfo(struct kimage *image)
 {
     struct page *vmcoreinfo_page;
     void *safecopy;
 
     if (image->type != KEXEC_TYPE_CRASH)
         return 0;
 
     /*
      * For kdump, allocate one vmcoreinfo safe copy from the
      * crash memory. as we have arch_kexec_protect_crashkres()
      * after kexec syscall, we naturally protect it from write
      * (even read) access under kernel direct mapping. But on
      * the other hand, we still need to operate it when crash
      * happens to generate vmcoreinfo note, hereby we rely on
      * vmap for this purpose.
      */
     vmcoreinfo_page = kimage_alloc_control_pages(image, 0);
     if (!vmcoreinfo_page) {
         pr_warn("Could not allocate vmcoreinfo buffer\n");
         return -ENOMEM;
     }
     safecopy = vmap(&vmcoreinfo_page, 1, VM_MAP, PAGE_KERNEL);
     if (!safecopy) {
         pr_warn("Could not vmap vmcoreinfo buffer\n");
         return -ENOMEM;
     }
 
     image->vmcoreinfo_data_copy = safecopy;
     crash_update_vmcoreinfo_safecopy(safecopy);
 
     return 0;
 }
 
 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_boot_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);
 
     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);
 
     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);
 
 }
 
 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) ? \
             boot_phys_to_virt((entry & PAGE_MASK)) : ptr + 1)
 
 static void kimage_free_entry(kimage_entry_t entry)
 {
     struct page *page;
 
     page = boot_pfn_to_page(entry >> PAGE_SHIFT);
     kimage_free_pages(page);
 }
 
 void kimage_free(struct kimage *image)
 {
     kimage_entry_t *ptr, entry;
     kimage_entry_t ind = 0;
 
     if (!image)
         return;
 
     if (image->vmcoreinfo_data_copy) {
         crash_update_vmcoreinfo_safecopy(NULL);
         vunmap(image->vmcoreinfo_data_copy);
     }
 
     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_boot_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_boot_pfn(page) >
                 (KEXEC_SOURCE_MEMORY_LIMIT >> PAGE_SHIFT)) {
             list_add(&page->lru, &image->unusable_pages);
             continue;
         }
         addr = page_to_boot_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 = boot_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;
             }
             page = old_page;
             break;
         }
         /* Place the page on the destination list, to be used 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;
 
     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_boot_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;
 
         cond_resched();
     }
 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 = boot_pfn_to_page(maddr >> PAGE_SHIFT);
         if (!page) {
             result  = -ENOMEM;
             goto out;
         }
         arch_kexec_post_alloc_pages(page_address(page), 1, 0);
         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);
         arch_kexec_pre_free_pages(page_address(page), 1);
         if (result) {
             result = -EFAULT;
             goto out;
         }
         ubytes -= uchunk;
         maddr  += mchunk;
         if (image->file_mode)
             kbuf += mchunk;
         else
             buf += mchunk;
         mbytes -= mchunk;
 
         cond_resched();
     }
 out:
     return result;
 }
 
 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;
 }
 
 struct kimage *kexec_image;
 struct kimage *kexec_crash_image;
 int kexec_load_disabled;
 #ifdef CONFIG_SYSCTL
 static struct ctl_table kexec_core_sysctls[] = {
     {
         .procname   = "kexec_load_disabled",
         .data       = &kexec_load_disabled,
         .maxlen     = sizeof(int),
         .mode       = 0644,
         /* only handle a transition from default "0" to "1" */
         .proc_handler   = proc_dointvec_minmax,
         .extra1     = SYSCTL_ONE,
         .extra2     = SYSCTL_ONE,
     },
     { }
 };
 
 static int __init kexec_core_sysctl_init(void)
 {
     register_sysctl_init("kernel", kexec_core_sysctls);
     return 0;
 }
 late_initcall(kexec_core_sysctl_init);
 #endif
 
 /*
  * No panic_cpu check version of crash_kexec().  This function is called
  * only when panic_cpu holds the current CPU number; this is the only CPU
  * which processes crash_kexec routines.
  */
 void __noclone __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);
     }
 }
 STACK_FRAME_NON_STANDARD(__crash_kexec);
 
 void crash_kexec(struct pt_regs *regs)
 {
     int old_cpu, this_cpu;
 
     /*
      * Only one CPU is allowed to execute the crash_kexec() code as with
      * panic().  Otherwise parallel calls of panic() and crash_kexec()
      * may stop each other.  To exclude them, we use panic_cpu here too.
      */
     this_cpu = raw_smp_processor_id();
     old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu);
     if (old_cpu == PANIC_CPU_INVALID) {
         /* This is the 1st CPU which comes here, so go ahead. */
         __crash_kexec(regs);
 
         /*
          * Reset panic_cpu to allow another panic()/crash_kexec()
          * call.
          */
         atomic_set(&panic_cpu, PANIC_CPU_INVALID);
     }
 }
 
 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;
 }
 
 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_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_SYSTEM_RAM;
     ram_res->name = "System RAM";
 
     crashk_res.end = end - 1;
 
     insert_resource(&iomem_resource, ram_res);
 
 unlock:
     mutex_unlock(&kexec_mutex);
     return ret;
 }
 
 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.common.pr_pid = current->pid;
     elf_core_copy_regs(&prstatus.pr_reg, regs);
     buf = append_elf_note(buf, KEXEC_CORE_NOTE_NAME, NT_PRSTATUS,
                   &prstatus, sizeof(prstatus));
     final_note(buf);
 }
 
 static int __init crash_notes_memory_init(void)
 {
     /* Allocate memory for saving cpu registers. */
     size_t size, align;
 
     /*
      * crash_notes could be allocated across 2 vmalloc pages when percpu
      * is vmalloc based . vmalloc doesn't guarantee 2 continuous vmalloc
      * pages are also on 2 continuous physical pages. In this case the
      * 2nd part of crash_notes in 2nd page could be lost since only the
      * starting address and size of crash_notes are exported through sysfs.
      * Here round up the size of crash_notes to the nearest power of two
      * and pass it to __alloc_percpu as align value. This can make sure
      * crash_notes is allocated inside one physical page.
      */
     size = sizeof(note_buf_t);
     align = min(roundup_pow_of_two(sizeof(note_buf_t)), PAGE_SIZE);
 
     /*
      * Break compile if size is bigger than PAGE_SIZE since crash_notes
      * definitely will be in 2 pages with that.
      */
     BUILD_BUG_ON(size > PAGE_SIZE);
 
     crash_notes = __alloc_percpu(size, align);
     if (!crash_notes) {
         pr_warn("Memory allocation for saving cpu register states failed\n");
         return -ENOMEM;
     }
     return 0;
 }
 subsys_initcall(crash_notes_memory_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) {
         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 = suspend_disable_secondary_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("kexec reboot");
         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_notice("Starting new kernel\n");
         machine_shutdown();
     }
 
     kmsg_dump(KMSG_DUMP_SHUTDOWN);
     machine_kexec(kexec_image);
 
 #ifdef CONFIG_KEXEC_JUMP
     if (kexec_image->preserve_context) {
         syscore_resume();
  Enable_irqs:
         local_irq_enable();
  Enable_cpus:
         suspend_enable_secondary_cpus();
         dpm_resume_start(PMSG_RESTORE);
  Resume_devices:
         dpm_resume_end(PMSG_RESTORE);
  Resume_console:
         resume_console();
         thaw_processes();
  Restore_console:
         pm_restore_console();
     }
 #endif
 
  Unlock:
     mutex_unlock(&kexec_mutex);
     return error;
 }

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