kexec: split kexec_file syscall code to kexec_file.c

Split kexec_file syscall related code to another file kernel/kexec_file.c
so that the #ifdef CONFIG_KEXEC_FILE in kexec.c can be dropped.

Sharing variables and functions are moved to kernel/kexec_internal.h per
suggestion from Vivek and Petr.

[akpm@linux-foundation.org: fix bisectability]
[akpm@linux-foundation.org: declare the various arch_kexec functions]
[akpm@linux-foundation.org: fix build]
Signed-off-by: Dave Young <dyoung@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Petr Tesarik <ptesarik@suse.cz>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Josh Boyer <jwboyer@fedoraproject.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1045 insertions, 0 deletions

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
new file mode 100644
index 0000000..6a9a3f2
--- /dev/null
+++ b/kernel/kexec_file.c
@@ -0,0 +1,1045 @@
+/*
+ * 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.
+ */
+
+#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 <crypto/hash.h>
+#include <crypto/sha.h>
+#include <linux/syscalls.h>
+#include <linux/vmalloc.h>
+#include "kexec_internal.h"
+
+/*
+ * Declare these symbols weak so that if architecture provides a purgatory,
+ * these will be overridden.
+ */
+char __weak kexec_purgatory[0];
+size_t __weak kexec_purgatory_size = 0;
+
+static int kexec_calculate_store_digests(struct kimage *image);
+
+static int copy_file_from_fd(int fd, void **buf, unsigned long *buf_len)
+{
+	struct fd f = fdget(fd);
+	int ret;
+	struct kstat stat;
+	loff_t pos;
+	ssize_t bytes = 0;
+
+	if (!f.file)
+		return -EBADF;
+
+	ret = vfs_getattr(&f.file->f_path, &stat);
+	if (ret)
+		goto out;
+
+	if (stat.size > INT_MAX) {
+		ret = -EFBIG;
+		goto out;
+	}
+
+	/* Don't hand 0 to vmalloc, it whines. */
+	if (stat.size == 0) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	*buf = vmalloc(stat.size);
+	if (!*buf) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	pos = 0;
+	while (pos < stat.size) {
+		bytes = kernel_read(f.file, pos, (char *)(*buf) + pos,
+				    stat.size - pos);
+		if (bytes < 0) {
+			vfree(*buf);
+			ret = bytes;
+			goto out;
+		}
+
+		if (bytes == 0)
+			break;
+		pos += bytes;
+	}
+
+	if (pos != stat.size) {
+		ret = -EBADF;
+		vfree(*buf);
+		goto out;
+	}
+
+	*buf_len = pos;
+out:
+	fdput(f);
+	return ret;
+}
+
+/* Architectures can provide this probe function */
+int __weak arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
+					 unsigned long buf_len)
+{
+	return -ENOEXEC;
+}
+
+void * __weak arch_kexec_kernel_image_load(struct kimage *image)
+{
+	return ERR_PTR(-ENOEXEC);
+}
+
+int __weak arch_kimage_file_post_load_cleanup(struct kimage *image)
+{
+	return -EINVAL;
+}
+
+int __weak arch_kexec_kernel_verify_sig(struct kimage *image, void *buf,
+					unsigned long buf_len)
+{
+	return -EKEYREJECTED;
+}
+
+/* Apply relocations of type RELA */
+int __weak
+arch_kexec_apply_relocations_add(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
+				 unsigned int relsec)
+{
+	pr_err("RELA relocation unsupported.\n");
+	return -ENOEXEC;
+}
+
+/* Apply relocations of type REL */
+int __weak
+arch_kexec_apply_relocations(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
+			     unsigned int relsec)
+{
+	pr_err("REL relocation unsupported.\n");
+	return -ENOEXEC;
+}
+
+/*
+ * Free up memory used by kernel, initrd, and 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;
+
+	ret = copy_file_from_fd(kernel_fd, &image->kernel_buf,
+				&image->kernel_buf_len);
+	if (ret)
+		return ret;
+
+	/* Call arch image probe handlers */
+	ret = arch_kexec_kernel_image_probe(image, image->kernel_buf,
+					    image->kernel_buf_len);
+
+	if (ret)
+		goto out;
+
+#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.\n");
+		goto out;
+	}
+	pr_debug("kernel signature verification successful.\n");
+#endif
+	/* It is possible that there no initramfs is being loaded */
+	if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
+		ret = copy_file_from_fd(initrd_fd, &image->initrd_buf,
+					&image->initrd_buf_len);
+		if (ret)
+			goto out;
+	}
+
+	if (cmdline_len) {
+		image->cmdline_buf = kzalloc(cmdline_len, GFP_KERNEL);
+		if (!image->cmdline_buf) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		ret = copy_from_user(image->cmdline_buf, cmdline_ptr,
+				     cmdline_len);
+		if (ret) {
+			ret = -EFAULT;
+			goto out;
+		}
+
+		image->cmdline_buf_len = cmdline_len;
+
+		/* command line should be a string with last byte null */
+		if (image->cmdline_buf[cmdline_len - 1] != '\0') {
+			ret = -EINVAL;
+			goto out;
+		}
+	}
+
+	/* Call arch image load handlers */
+	ldata = arch_kexec_kernel_image_load(image);
+
+	if (IS_ERR(ldata)) {
+		ret = PTR_ERR(ldata);
+		goto out;
+	}
+
+	image->image_loader_data = ldata;
+out:
+	/* In case of error, free up all allocated memory in this function */
+	if (ret)
+		kimage_file_post_load_cleanup(image);
+	return ret;
+}
+
+static int
+kimage_file_alloc_init(struct kimage **rimage, int kernel_fd,
+		       int initrd_fd, const char __user *cmdline_ptr,
+		       unsigned long cmdline_len, unsigned long flags)
+{
+	int ret;
+	struct kimage *image;
+	bool kexec_on_panic = flags & KEXEC_FILE_ON_CRASH;
+
+	image = do_kimage_alloc_init();
+	if (!image)
+		return -ENOMEM;
+
+	image->file_mode = 1;
+
+	if (kexec_on_panic) {
+		/* Enable special crash kernel control page alloc policy. */
+		image->control_page = crashk_res.start;
+		image->type = KEXEC_TYPE_CRASH;
+	}
+
+	ret = kimage_file_prepare_segments(image, kernel_fd, initrd_fd,
+					   cmdline_ptr, cmdline_len, flags);
+	if (ret)
+		goto out_free_image;
+
+	ret = sanity_check_segment_list(image);
+	if (ret)
+		goto out_free_post_load_bufs;
+
+	ret = -ENOMEM;
+	image->control_code_page = kimage_alloc_control_pages(image,
+					   get_order(KEXEC_CONTROL_PAGE_SIZE));
+	if (!image->control_code_page) {
+		pr_err("Could not allocate control_code_buffer\n");
+		goto out_free_post_load_bufs;
+	}
+
+	if (!kexec_on_panic) {
+		image->swap_page = kimage_alloc_control_pages(image, 0);
+		if (!image->swap_page) {
+			pr_err("Could not allocate swap buffer\n");
+			goto out_free_control_pages;
+		}
+	}
+
+	*rimage = image;
+	return 0;
+out_free_control_pages:
+	kimage_free_page_list(&image->control_pages);
+out_free_post_load_bufs:
+	kimage_file_post_load_cleanup(image);
+out_free_image:
+	kfree(image);
+	return ret;
+}
+
+SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
+		unsigned long, cmdline_len, const char __user *, cmdline_ptr,
+		unsigned long, flags)
+{
+	int ret = 0, i;
+	struct kimage **dest_image, *image;
+
+	/* We only trust the superuser with rebooting the system. */
+	if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
+		return -EPERM;
+
+	/* Make sure we have a legal set of flags */
+	if (flags != (flags & KEXEC_FILE_FLAGS))
+		return -EINVAL;
+
+	image = NULL;
+
+	if (!mutex_trylock(&kexec_mutex))
+		return -EBUSY;
+
+	dest_image = &kexec_image;
+	if (flags & KEXEC_FILE_ON_CRASH)
+		dest_image = &kexec_crash_image;
+
+	if (flags & KEXEC_FILE_UNLOAD)
+		goto exchange;
+
+	/*
+	 * In case of crash, new kernel gets loaded in reserved region. It is
+	 * same memory where old crash kernel might be loaded. Free any
+	 * current crash dump kernel before we corrupt it.
+	 */
+	if (flags & KEXEC_FILE_ON_CRASH)
+		kimage_free(xchg(&kexec_crash_image, NULL));
+
+	ret = kimage_file_alloc_init(&image, kernel_fd, initrd_fd, cmdline_ptr,
+				     cmdline_len, flags);
+	if (ret)
+		goto out;
+
+	ret = machine_kexec_prepare(image);
+	if (ret)
+		goto out;
+
+	ret = kexec_calculate_store_digests(image);
+	if (ret)
+		goto out;
+
+	for (i = 0; i < image->nr_segments; i++) {
+		struct kexec_segment *ksegment;
+
+		ksegment = &image->segment[i];
+		pr_debug("Loading segment %d: buf=0x%p bufsz=0x%zx mem=0x%lx memsz=0x%zx\n",
+			 i, ksegment->buf, ksegment->bufsz, ksegment->mem,
+			 ksegment->memsz);
+
+		ret = kimage_load_segment(image, &image->segment[i]);
+		if (ret)
+			goto out;
+	}
+
+	kimage_terminate(image);
+
+	/*
+	 * Free up any temporary buffers allocated which are not needed
+	 * after image has been loaded
+	 */
+	kimage_file_post_load_cleanup(image);
+exchange:
+	image = xchg(dest_image, image);
+out:
+	mutex_unlock(&kexec_mutex);
+	kimage_free(image);
+	return ret;
+}
+
+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);
+}
+
+/*
+ * Helper function for placing a buffer in a kexec segment. This assumes
+ * that kexec_mutex is held.
+ */
+int kexec_add_buffer(struct kimage *image, char *buffer, unsigned long bufsz,
+		     unsigned long memsz, unsigned long buf_align,
+		     unsigned long buf_min, unsigned long buf_max,
+		     bool top_down, unsigned long *load_addr)
+{
+
+	struct kexec_segment *ksegment;
+	struct kexec_buf buf, *kbuf;
+	int ret;
+
+	/* Currently adding segment this way is allowed only in file mode */
+	if (!image->file_mode)
+		return -EINVAL;
+
+	if (image->nr_segments >= KEXEC_SEGMENT_MAX)
+		return -EINVAL;
+
+	/*
+	 * Make sure we are not trying to add buffer after allocating
+	 * control pages. All segments need to be placed first before
+	 * any control pages are allocated. As control page allocation
+	 * logic goes through list of segments to make sure there are
+	 * no destination overlaps.
+	 */
+	if (!list_empty(&image->control_pages)) {
+		WARN_ON(1);
+		return -EINVAL;
+	}
+
+	memset(&buf, 0, sizeof(struct kexec_buf));
+	kbuf = &buf;
+	kbuf->image = image;
+	kbuf->buffer = buffer;
+	kbuf->bufsz = bufsz;
+
+	kbuf->memsz = ALIGN(memsz, PAGE_SIZE);
+	kbuf->buf_align = max(buf_align, PAGE_SIZE);
+	kbuf->buf_min = buf_min;
+	kbuf->buf_max = buf_max;
+	kbuf->top_down = top_down;
+
+	/* Walk the RAM ranges and allocate a suitable range for the buffer */
+	if (image->type == KEXEC_TYPE_CRASH)
+		ret = walk_iomem_res("Crash kernel",
+				     IORESOURCE_MEM | IORESOURCE_BUSY,
+				     crashk_res.start, crashk_res.end, kbuf,
+				     locate_mem_hole_callback);
+	else
+		ret = walk_system_ram_res(0, -1, kbuf,
+					  locate_mem_hole_callback);
+	if (ret != 1) {
+		/* A suitable memory range could not be found for buffer */
+		return -EADDRNOTAVAIL;
+	}
+
+	/* Found a suitable memory range */
+	ksegment = &image->segment[image->nr_segments];
+	ksegment->kbuf = kbuf->buffer;
+	ksegment->bufsz = kbuf->bufsz;
+	ksegment->mem = kbuf->mem;
+	ksegment->memsz = kbuf->memsz;
+	image->nr_segments++;
+	*load_addr = ksegment->mem;
+	return 0;
+}
+
+/* Calculate and store the digest of segments */
+static int kexec_calculate_store_digests(struct kimage *image)
+{
+	struct crypto_shash *tfm;
+	struct shash_desc *desc;
+	int ret = 0, i, j, zero_buf_sz, sha_region_sz;
+	size_t desc_size, nullsz;
+	char *digest;
+	void *zero_buf;
+	struct kexec_sha_region *sha_regions;
+	struct purgatory_info *pi = &image->purgatory_info;
+
+	zero_buf = __va(page_to_pfn(ZERO_PAGE(0)) << PAGE_SHIFT);
+	zero_buf_sz = PAGE_SIZE;
+
+	tfm = crypto_alloc_shash("sha256", 0, 0);
+	if (IS_ERR(tfm)) {
+		ret = PTR_ERR(tfm);
+		goto out;
+	}
+
+	desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
+	desc = kzalloc(desc_size, GFP_KERNEL);
+	if (!desc) {
+		ret = -ENOMEM;
+		goto out_free_tfm;
+	}
+
+	sha_region_sz = KEXEC_SEGMENT_MAX * sizeof(struct kexec_sha_region);
+	sha_regions = vzalloc(sha_region_sz);
+	if (!sha_regions)
+		goto out_free_desc;
+
+	desc->tfm   = tfm;
+	desc->flags = 0;
+
+	ret = crypto_shash_init(desc);
+	if (ret < 0)
+		goto out_free_sha_regions;
+
+	digest = kzalloc(SHA256_DIGEST_SIZE, GFP_KERNEL);
+	if (!digest) {
+		ret = -ENOMEM;
+		goto out_free_sha_regions;
+	}
+
+	for (j = i = 0; i < image->nr_segments; i++) {
+		struct kexec_segment *ksegment;
+
+		ksegment = &image->segment[i];
+		/*
+		 * Skip purgatory as it will be modified once we put digest
+		 * info in purgatory.
+		 */
+		if (ksegment->kbuf == pi->purgatory_buf)
+			continue;
+
+		ret = crypto_shash_update(desc, ksegment->kbuf,
+					  ksegment->bufsz);
+		if (ret)
+			break;
+
+		/*
+		 * Assume rest of the buffer is filled with zero and
+		 * update digest accordingly.
+		 */
+		nullsz = ksegment->memsz - ksegment->bufsz;
+		while (nullsz) {
+			unsigned long bytes = nullsz;
+
+			if (bytes > zero_buf_sz)
+				bytes = zero_buf_sz;
+			ret = crypto_shash_update(desc, zero_buf, bytes);
+			if (ret)
+				break;
+			nullsz -= bytes;
+		}
+
+		if (ret)
+			break;
+
+		sha_regions[j].start = ksegment->mem;
+		sha_regions[j].len = ksegment->memsz;
+		j++;
+	}
+
+	if (!ret) {
+		ret = crypto_shash_final(desc, digest);
+		if (ret)
+			goto out_free_digest;
+		ret = kexec_purgatory_get_set_symbol(image, "sha_regions",
+						sha_regions, sha_region_sz, 0);
+		if (ret)
+			goto out_free_digest;
+
+		ret = kexec_purgatory_get_set_symbol(image, "sha256_digest",
+						digest, SHA256_DIGEST_SIZE, 0);
+		if (ret)
+			goto out_free_digest;
+	}
+
+out_free_digest:
+	kfree(digest);
+out_free_sha_regions:
+	vfree(sha_regions);
+out_free_desc:
+	kfree(desc);
+out_free_tfm:
+	kfree(tfm);
+out:
+	return ret;
+}
+
+/* Actually load purgatory. Lot of code taken from kexec-tools */
+static int __kexec_load_purgatory(struct kimage *image, unsigned long min,
+				  unsigned long max, int top_down)
+{
+	struct purgatory_info *pi = &image->purgatory_info;
+	unsigned long align, buf_align, bss_align, buf_sz, bss_sz, bss_pad;
+	unsigned long memsz, entry, load_addr, curr_load_addr, bss_addr, offset;
+	unsigned char *buf_addr, *src;
+	int i, ret = 0, entry_sidx = -1;
+	const Elf_Shdr *sechdrs_c;
+	Elf_Shdr *sechdrs = NULL;
+	void *purgatory_buf = NULL;
+
+	/*
+	 * sechdrs_c points to section headers in purgatory and are read
+	 * only. No modifications allowed.
+	 */
+	sechdrs_c = (void *)pi->ehdr + pi->ehdr->e_shoff;
+
+	/*
+	 * We can not modify sechdrs_c[] and its fields. It is read only.
+	 * Copy it over to a local copy where one can store some temporary
+	 * data and free it at the end. We need to modify ->sh_addr and
+	 * ->sh_offset fields to keep track of permanent and temporary
+	 * locations of sections.
+	 */
+	sechdrs = vzalloc(pi->ehdr->e_shnum * sizeof(Elf_Shdr));
+	if (!sechdrs)
+		return -ENOMEM;
+
+	memcpy(sechdrs, sechdrs_c, pi->ehdr->e_shnum * sizeof(Elf_Shdr));
+
+	/*
+	 * We seem to have multiple copies of sections. First copy is which
+	 * is embedded in kernel in read only section. Some of these sections
+	 * will be copied to a temporary buffer and relocated. And these
+	 * sections will finally be copied to their final destination at
+	 * segment load time.
+	 *
+	 * Use ->sh_offset to reflect section address in memory. It will
+	 * point to original read only copy if section is not allocatable.
+	 * Otherwise it will point to temporary copy which will be relocated.
+	 *
+	 * Use ->sh_addr to contain final address of the section where it
+	 * will go during execution time.
+	 */
+	for (i = 0; i < pi->ehdr->e_shnum; i++) {
+		if (sechdrs[i].sh_type == SHT_NOBITS)
+			continue;
+
+		sechdrs[i].sh_offset = (unsigned long)pi->ehdr +
+						sechdrs[i].sh_offset;
+	}
+
+	/*
+	 * Identify entry point section and make entry relative to section
+	 * start.
+	 */
+	entry = pi->ehdr->e_entry;
+	for (i = 0; i < pi->ehdr->e_shnum; i++) {
+		if (!(sechdrs[i].sh_flags & SHF_ALLOC))
+			continue;
+
+		if (!(sechdrs[i].sh_flags & SHF_EXECINSTR))
+			continue;
+
+		/* Make entry section relative */
+		if (sechdrs[i].sh_addr <= pi->ehdr->e_entry &&
+		    ((sechdrs[i].sh_addr + sechdrs[i].sh_size) >
+		     pi->ehdr->e_entry)) {
+			entry_sidx = i;
+			entry -= sechdrs[i].sh_addr;
+			break;
+		}
+	}
+
+	/* Determine how much memory is needed to load relocatable object. */
+	buf_align = 1;
+	bss_align = 1;
+	buf_sz = 0;
+	bss_sz = 0;
+
+	for (i = 0; i < pi->ehdr->e_shnum; i++) {
+		if (!(sechdrs[i].sh_flags & SHF_ALLOC))
+			continue;
+
+		align = sechdrs[i].sh_addralign;
+		if (sechdrs[i].sh_type != SHT_NOBITS) {
+			if (buf_align < align)
+				buf_align = align;
+			buf_sz = ALIGN(buf_sz, align);
+			buf_sz += sechdrs[i].sh_size;
+		} else {
+			/* bss section */
+			if (bss_align < align)
+				bss_align = align;
+			bss_sz = ALIGN(bss_sz, align);
+			bss_sz += sechdrs[i].sh_size;
+		}
+	}
+
+	/* Determine the bss padding required to align bss properly */
+	bss_pad = 0;
+	if (buf_sz & (bss_align - 1))
+		bss_pad = bss_align - (buf_sz & (bss_align - 1));
+
+	memsz = buf_sz + bss_pad + bss_sz;
+
+	/* Allocate buffer for purgatory */
+	purgatory_buf = vzalloc(buf_sz);
+	if (!purgatory_buf) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	if (buf_align < bss_align)
+		buf_align = bss_align;
+
+	/* Add buffer to segment list */
+	ret = kexec_add_buffer(image, purgatory_buf, buf_sz, memsz,
+				buf_align, min, max, top_down,
+				&pi->purgatory_load_addr);
+	if (ret)
+		goto out;
+
+	/* Load SHF_ALLOC sections */
+	buf_addr = purgatory_buf;
+	load_addr = curr_load_addr = pi->purgatory_load_addr;
+	bss_addr = load_addr + buf_sz + bss_pad;
+
+	for (i = 0; i < pi->ehdr->e_shnum; i++) {
+		if (!(sechdrs[i].sh_flags & SHF_ALLOC))
+			continue;
+
+		align = sechdrs[i].sh_addralign;
+		if (sechdrs[i].sh_type != SHT_NOBITS) {
+			curr_load_addr = ALIGN(curr_load_addr, align);
+			offset = curr_load_addr - load_addr;
+			/* We already modifed ->sh_offset to keep src addr */
+			src = (char *) sechdrs[i].sh_offset;
+			memcpy(buf_addr + offset, src, sechdrs[i].sh_size);
+
+			/* Store load address and source address of section */
+			sechdrs[i].sh_addr = curr_load_addr;
+
+			/*
+			 * This section got copied to temporary buffer. Update
+			 * ->sh_offset accordingly.
+			 */
+			sechdrs[i].sh_offset = (unsigned long)(buf_addr + offset);
+
+			/* Advance to the next address */
+			curr_load_addr += sechdrs[i].sh_size;
+		} else {
+			bss_addr = ALIGN(bss_addr, align);
+			sechdrs[i].sh_addr = bss_addr;
+			bss_addr += sechdrs[i].sh_size;
+		}
+	}
+
+	/* Update entry point based on load address of text section */
+	if (entry_sidx >= 0)
+		entry += sechdrs[entry_sidx].sh_addr;
+
+	/* Make kernel jump to purgatory after shutdown */
+	image->start = entry;
+
+	/* Used later to get/set symbol values */
+	pi->sechdrs = sechdrs;
+
+	/*
+	 * Used later to identify which section is purgatory and skip it
+	 * from checksumming.
+	 */
+	pi->purgatory_buf = purgatory_buf;
+	return ret;
+out:
+	vfree(sechdrs);
+	vfree(purgatory_buf);
+	return ret;
+}
+
+static int kexec_apply_relocations(struct kimage *image)
+{
+	int i, ret;
+	struct purgatory_info *pi = &image->purgatory_info;
+	Elf_Shdr *sechdrs = pi->sechdrs;
+
+	/* Apply relocations */
+	for (i = 0; i < pi->ehdr->e_shnum; i++) {
+		Elf_Shdr *section, *symtab;
+
+		if (sechdrs[i].sh_type != SHT_RELA &&
+		    sechdrs[i].sh_type != SHT_REL)
+			continue;
+
+		/*
+		 * For section of type SHT_RELA/SHT_REL,
+		 * ->sh_link contains section header index of associated
+		 * symbol table. And ->sh_info contains section header
+		 * index of section to which relocations apply.
+		 */
+		if (sechdrs[i].sh_info >= pi->ehdr->e_shnum ||
+		    sechdrs[i].sh_link >= pi->ehdr->e_shnum)
+			return -ENOEXEC;
+
+		section = &sechdrs[sechdrs[i].sh_info];
+		symtab = &sechdrs[sechdrs[i].sh_link];
+
+		if (!(section->sh_flags & SHF_ALLOC))
+			continue;
+
+		/*
+		 * symtab->sh_link contain section header index of associated
+		 * string table.
+		 */
+		if (symtab->sh_link >= pi->ehdr->e_shnum)
+			/* Invalid section number? */
+			continue;
+
+		/*
+		 * Respective 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);
+	vfree(pi->purgatory_buf);
+	return ret;
+}
+
+static Elf_Sym *kexec_purgatory_find_symbol(struct purgatory_info *pi,
+					    const char *name)
+{
+	Elf_Sym *syms;
+	Elf_Shdr *sechdrs;
+	Elf_Ehdr *ehdr;
+	int i, k;
+	const char *strtab;
+
+	if (!pi->sechdrs || !pi->ehdr)
+		return NULL;
+
+	sechdrs = pi->sechdrs;
+	ehdr = pi->ehdr;
+
+	for (i = 0; i < ehdr->e_shnum; i++) {
+		if (sechdrs[i].sh_type != SHT_SYMTAB)
+			continue;
+
+		if (sechdrs[i].sh_link >= ehdr->e_shnum)
+			/* Invalid strtab section number */
+			continue;
+		strtab = (char *)sechdrs[sechdrs[i].sh_link].sh_offset;
+		syms = (Elf_Sym *)sechdrs[i].sh_offset;
+
+		/* Go through symbols for a match */
+		for (k = 0; k < sechdrs[i].sh_size/sizeof(Elf_Sym); k++) {
+			if (ELF_ST_BIND(syms[k].st_info) != STB_GLOBAL)
+				continue;
+
+			if (strcmp(strtab + syms[k].st_name, name) != 0)
+				continue;
+
+			if (syms[k].st_shndx == SHN_UNDEF ||
+			    syms[k].st_shndx >= ehdr->e_shnum) {
+				pr_debug("Symbol: %s has bad section index %d.\n",
+						name, syms[k].st_shndx);
+				return NULL;
+			}
+
+			/* Found the symbol we are looking for */
+			return &syms[k];
+		}
+	}
+
+	return NULL;
+}
+
+void *kexec_purgatory_get_symbol_addr(struct kimage *image, const char *name)
+{
+	struct purgatory_info *pi = &image->purgatory_info;
+	Elf_Sym *sym;
+	Elf_Shdr *sechdr;
+
+	sym = kexec_purgatory_find_symbol(pi, name);
+	if (!sym)
+		return ERR_PTR(-EINVAL);
+
+	sechdr = &pi->sechdrs[sym->st_shndx];
+
+	/*
+	 * Returns the address where symbol will finally be loaded after
+	 * kexec_load_segment()
+	 */
+	return (void *)(sechdr->sh_addr + sym->st_value);
+}
+
+/*
+ * Get or set value of a symbol. If "get_value" is true, symbol value is
+ * returned in buf otherwise symbol value is set based on value in buf.
+ */
+int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name,
+				   void *buf, unsigned int size, bool get_value)
+{
+	Elf_Sym *sym;
+	Elf_Shdr *sechdrs;
+	struct purgatory_info *pi = &image->purgatory_info;
+	char *sym_buf;
+
+	sym = kexec_purgatory_find_symbol(pi, name);
+	if (!sym)
+		return -EINVAL;
+
+	if (sym->st_size != size) {
+		pr_err("symbol %s size mismatch: expected %lu actual %u\n",
+		       name, (unsigned long)sym->st_size, size);
+		return -EINVAL;
+	}
+
+	sechdrs = pi->sechdrs;
+
+	if (sechdrs[sym->st_shndx].sh_type == SHT_NOBITS) {
+		pr_err("symbol %s is in a bss section. Cannot %s\n", name,
+		       get_value ? "get" : "set");
+		return -EINVAL;
+	}
+
+	sym_buf = (unsigned char *)sechdrs[sym->st_shndx].sh_offset +
+					sym->st_value;
+
+	if (get_value)
+		memcpy((void *)buf, sym_buf, size);
+	else
+		memcpy((void *)sym_buf, buf, size);
+
+	return 0;
+}