kexec_file.c 25.4 KB
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/*
 * 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.
 */

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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

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#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>
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#include <linux/fs.h>
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#include <linux/ima.h>
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#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;
}

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#ifdef CONFIG_KEXEC_VERIFY_SIG
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int __weak arch_kexec_kernel_verify_sig(struct kimage *image, void *buf,
					unsigned long buf_len)
{
	return -EKEYREJECTED;
}
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#endif
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/* 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;
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	loff_t size;
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	ret = kernel_read_file_from_fd(kernel_fd, &image->kernel_buf,
				       &size, INT_MAX, READING_KEXEC_IMAGE);
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	if (ret)
		return ret;
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	image->kernel_buf_len = size;
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	/* IMA needs to pass the measurement list to the next kernel. */
	ima_add_kexec_buffer(image);

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	/* 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)) {
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		ret = kernel_read_file_from_fd(initrd_fd, &image->initrd_buf,
					       &size, INT_MAX,
					       READING_KEXEC_INITRAMFS);
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		if (ret)
			goto out;
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		image->initrd_buf_len = size;
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	}

	if (cmdline_len) {
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		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;
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			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;
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	if (flags & KEXEC_FILE_ON_CRASH) {
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		dest_image = &kexec_crash_image;
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		if (kexec_crash_image)
			arch_kexec_unprotect_crashkres();
	}
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	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;

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	/*
	 * 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;

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

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	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);
}

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/**
 * 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);
}

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/**
 * 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;
}

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/**
 * 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.
477
 */
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int kexec_add_buffer(struct kexec_buf *kbuf)
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{

	struct kexec_segment *ksegment;
	int ret;

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

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	if (kbuf->image->nr_segments >= KEXEC_SEGMENT_MAX)
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		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.
	 */
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	if (!list_empty(&kbuf->image->control_pages)) {
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		WARN_ON(1);
		return -EINVAL;
	}

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	/* Ensure minimum alignment needed for segments. */
	kbuf->memsz = ALIGN(kbuf->memsz, PAGE_SIZE);
	kbuf->buf_align = max(kbuf->buf_align, PAGE_SIZE);
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	/* Walk the RAM ranges and allocate a suitable range for the buffer */
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	ret = kexec_locate_mem_hole(kbuf);
	if (ret)
		return ret;
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	/* Found a suitable memory range */
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	ksegment = &kbuf->image->segment[kbuf->image->nr_segments];
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	ksegment->kbuf = kbuf->buffer;
	ksegment->bufsz = kbuf->bufsz;
	ksegment->mem = kbuf->mem;
	ksegment->memsz = kbuf->memsz;
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	kbuf->image->nr_segments++;
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	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;
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		ret = kexec_purgatory_get_set_symbol(image, "purgatory_sha_regions",
						     sha_regions, sha_region_sz, 0);
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		if (ret)
			goto out_free_digest;

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		ret = kexec_purgatory_get_set_symbol(image, "purgatory_sha256_digest",
						     digest, SHA256_DIGEST_SIZE, 0);
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		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;
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	unsigned long align, bss_align, bss_sz, bss_pad;
	unsigned long entry, load_addr, curr_load_addr, bss_addr, offset;
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	unsigned char *buf_addr, *src;
	int i, ret = 0, entry_sidx = -1;
	const Elf_Shdr *sechdrs_c;
	Elf_Shdr *sechdrs = NULL;
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	struct kexec_buf kbuf = { .image = image, .bufsz = 0, .buf_align = 1,
				  .buf_min = min, .buf_max = max,
				  .top_down = top_down };
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	/*
	 * 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) {
723 724 725 726
			if (kbuf.buf_align < align)
				kbuf.buf_align = align;
			kbuf.bufsz = ALIGN(kbuf.bufsz, align);
			kbuf.bufsz += sechdrs[i].sh_size;
727 728 729 730 731 732 733 734 735 736 737
		} 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;
738 739
	if (kbuf.bufsz & (bss_align - 1))
		bss_pad = bss_align - (kbuf.bufsz & (bss_align - 1));
740

741
	kbuf.memsz = kbuf.bufsz + bss_pad + bss_sz;
742 743

	/* Allocate buffer for purgatory */
744 745
	kbuf.buffer = vzalloc(kbuf.bufsz);
	if (!kbuf.buffer) {
746 747 748 749
		ret = -ENOMEM;
		goto out;
	}

750 751
	if (kbuf.buf_align < bss_align)
		kbuf.buf_align = bss_align;
752 753

	/* Add buffer to segment list */
754
	ret = kexec_add_buffer(&kbuf);
755 756
	if (ret)
		goto out;
757
	pi->purgatory_load_addr = kbuf.mem;
758 759

	/* Load SHF_ALLOC sections */
760
	buf_addr = kbuf.buffer;
761
	load_addr = curr_load_addr = pi->purgatory_load_addr;
762
	bss_addr = load_addr + kbuf.bufsz + bss_pad;
763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807

	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.
	 */
808
	pi->purgatory_buf = kbuf.buffer;
809 810 811
	return ret;
out:
	vfree(sechdrs);
812
	vfree(kbuf.buffer);
813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909
	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);
910 911
	pi->sechdrs = NULL;

912
	vfree(pi->purgatory_buf);
913
	pi->purgatory_buf = NULL;
914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023
	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;
}