/*
   * kexec: kexec_file_load system call
   *
   * Copyright (C) 2014 Red Hat Inc.
   * Authors:
   *      Vivek Goyal <vgoyal@redhat.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) KBUILD_MODNAME ": " fmt

  #include <linux/capability.h>
  #include <linux/mm.h>
  #include <linux/file.h>
  #include <linux/slab.h>
  #include <linux/kexec.h>
  #include <linux/mutex.h>
  #include <linux/list.h>

  #include <linux/fs.h>

  #include <linux/ima.h>

  #include <crypto/hash.h>
  #include <crypto/sha.h>
  #include <linux/syscalls.h>
  #include <linux/vmalloc.h>
  #include "kexec_internal.h"

  static int kexec_calculate_store_digests(struct kimage *image);

  /* 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);
  }
  
  int __weak arch_kimage_file_post_load_cleanup(struct kimage *image)
  {
  	return -EINVAL;
  }

  #ifdef CONFIG_KEXEC_VERIFY_SIG

  int __weak arch_kexec_kernel_verify_sig(struct kimage *image, void *buf,
  					unsigned long buf_len)
  {
  	return -EKEYREJECTED;
  }

  #endif

  
  /* 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.
  ");
  	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.
  ");
  	return -ENOEXEC;
  }
  
  /*
   * Free up memory used by kernel, initrd, and command 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.
   */
  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;

  	loff_t size;

  	ret = kernel_read_file_from_fd(kernel_fd, &image->kernel_buf,
  				       &size, INT_MAX, READING_KEXEC_IMAGE);

  	if (ret)
  		return ret;

  	image->kernel_buf_len = size;

  	/* IMA needs to pass the measurement list to the next kernel. */
  	ima_add_kexec_buffer(image);

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

  	if (ret)
  		goto out;
  
  #ifdef CONFIG_KEXEC_VERIFY_SIG
  	ret = arch_kexec_kernel_verify_sig(image, image->kernel_buf,
  					   image->kernel_buf_len);
  	if (ret) {
  		pr_debug("kernel signature verification failed.
  ");
  		goto out;
  	}
  	pr_debug("kernel signature verification successful.
  ");
  #endif
  	/* It is possible that there no initramfs is being loaded */
  	if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {

  		ret = kernel_read_file_from_fd(initrd_fd, &image->initrd_buf,
  					       &size, INT_MAX,
  					       READING_KEXEC_INITRAMFS);

  		if (ret)
  			goto out;

  		image->initrd_buf_len = size;

  	}
  
  	if (cmdline_len) {

  		image->cmdline_buf = memdup_user(cmdline_ptr, cmdline_len);
  		if (IS_ERR(image->cmdline_buf)) {
  			ret = PTR_ERR(image->cmdline_buf);
  			image->cmdline_buf = NULL;

  			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
  ");
  		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("Could not allocate swap buffer
  ");
  			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;
  }
  
  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 (kexec_crash_image)
  			arch_kexec_unprotect_crashkres();
  	}

  
  	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;

  	/*
  	 * Some architecture(like S390) may touch the crash memory before
  	 * machine_kexec_prepare(), we must copy vmcoreinfo data after it.
  	 */
  	ret = kimage_crash_copy_vmcoreinfo(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
  ",
  			 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:

  	if ((flags & KEXEC_FILE_ON_CRASH) && kexec_crash_image)
  		arch_kexec_protect_crashkres();

  	mutex_unlock(&kexec_mutex);
  	kimage_free(image);
  	return ret;
  }
  
  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 */
  	kbuf->mem = temp_start;
  
  	/* 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 */
  	kbuf->mem = temp_start;
  
  	/* 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);
  }

  /**
   * arch_kexec_walk_mem - call func(data) on free memory regions
   * @kbuf:	Context info for the search. Also passed to @func.
   * @func:	Function to call for each memory region.
   *
   * Return: The memory walk will stop when func returns a non-zero value
   * and that value will be returned. If all free regions are visited without
   * func returning non-zero, then zero will be returned.
   */
  int __weak arch_kexec_walk_mem(struct kexec_buf *kbuf,
  			       int (*func)(u64, u64, void *))
  {
  	if (kbuf->image->type == KEXEC_TYPE_CRASH)
  		return walk_iomem_res_desc(crashk_res.desc,
  					   IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY,
  					   crashk_res.start, crashk_res.end,
  					   kbuf, func);
  	else
  		return walk_system_ram_res(0, ULONG_MAX, kbuf, func);
  }

  /**

   * kexec_locate_mem_hole - find free memory for the purgatory or the next kernel
   * @kbuf:	Parameters for the memory search.
   *
   * On success, kbuf->mem will have the start address of the memory region found.
   *
   * Return: 0 on success, negative errno on error.
   */
  int kexec_locate_mem_hole(struct kexec_buf *kbuf)
  {
  	int ret;
  
  	ret = arch_kexec_walk_mem(kbuf, locate_mem_hole_callback);
  
  	return ret == 1 ? 0 : -EADDRNOTAVAIL;
  }
  
  /**

   * kexec_add_buffer - place a buffer in a kexec segment
   * @kbuf:	Buffer contents and memory parameters.
   *
   * This function assumes that kexec_mutex is held.
   * On successful return, @kbuf->mem will have the physical address of
   * the buffer in memory.
   *
   * Return: 0 on success, negative errno on error.

   */

  int kexec_add_buffer(struct kexec_buf *kbuf)

  {
  
  	struct kexec_segment *ksegment;

  	int ret;
  
  	/* Currently adding segment this way is allowed only in file mode */

  	if (!kbuf->image->file_mode)

  		return -EINVAL;

  	if (kbuf->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(&kbuf->image->control_pages)) {

  		WARN_ON(1);
  		return -EINVAL;
  	}

  	/* Ensure minimum alignment needed for segments. */
  	kbuf->memsz = ALIGN(kbuf->memsz, PAGE_SIZE);
  	kbuf->buf_align = max(kbuf->buf_align, PAGE_SIZE);

  
  	/* Walk the RAM ranges and allocate a suitable range for the buffer */

  	ret = kexec_locate_mem_hole(kbuf);
  	if (ret)
  		return ret;

  
  	/* Found a suitable memory range */

  	ksegment = &kbuf->image->segment[kbuf->image->nr_segments];

  	ksegment->kbuf = kbuf->buffer;
  	ksegment->bufsz = kbuf->bufsz;
  	ksegment->mem = kbuf->mem;
  	ksegment->memsz = kbuf->memsz;

  	kbuf->image->nr_segments++;

  	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, "purgatory_sha_regions",
  						     sha_regions, sha_region_sz, 0);

  		if (ret)
  			goto out_free_digest;

  		ret = kexec_purgatory_get_set_symbol(image, "purgatory_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, bss_align, bss_sz, bss_pad;
  	unsigned long 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;

  	struct kexec_buf kbuf = { .image = image, .bufsz = 0, .buf_align = 1,
  				  .buf_min = min, .buf_max = max,
  				  .top_down = top_down };

  
  	/*
  	 * 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. */

  	bss_align = 1;

  	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 (kbuf.buf_align < align)
  				kbuf.buf_align = align;
  			kbuf.bufsz = ALIGN(kbuf.bufsz, align);
  			kbuf.bufsz += 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 (kbuf.bufsz & (bss_align - 1))
  		bss_pad = bss_align - (kbuf.bufsz & (bss_align - 1));

  	kbuf.memsz = kbuf.bufsz + bss_pad + bss_sz;

  
  	/* Allocate buffer for purgatory */

  	kbuf.buffer = vzalloc(kbuf.bufsz);
  	if (!kbuf.buffer) {

  		ret = -ENOMEM;
  		goto out;
  	}

  	if (kbuf.buf_align < bss_align)
  		kbuf.buf_align = bss_align;

  
  	/* Add buffer to segment list */

  	ret = kexec_add_buffer(&kbuf);

  	if (ret)
  		goto out;

  	pi->purgatory_load_addr = kbuf.mem;

  
  	/* Load SHF_ALLOC sections */

  	buf_addr = kbuf.buffer;

  	load_addr = curr_load_addr = pi->purgatory_load_addr;

  	bss_addr = load_addr + kbuf.bufsz + 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 = kbuf.buffer;

  	return ret;
  out:
  	vfree(sechdrs);

  	vfree(kbuf.buffer);

  	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 architecture 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);

  	pi->sechdrs = NULL;

  	vfree(pi->purgatory_buf);

  	pi->purgatory_buf = NULL;

  	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.
  ",
  						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
  ",
  		       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
  ", 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;
  }