// SPDX-License-Identifier: GPL-2.0-only
/*
 * kexec: kexec_file_load system call
 *
 * Copyright (C) 2014 Red Hat Inc.
 * Authors:
 *      Vivek Goyal <vgoyal@redhat.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/kexec.h>
#include <linux/memblock.h>
#include <linux/mutex.h>
#include <linux/list.h>
#include <linux/fs.h>
#include <linux/ima.h>
#include <crypto/hash.h>
#include <crypto/sha2.h>
#include <linux/elf.h>
#include <linux/elfcore.h>
#include <linux/kernel.h>
#include <linux/kernel_read_file.h>
#include <linux/syscalls.h>
#include <linux/vmalloc.h>
#include "kexec_internal.h"

#ifdef CONFIG_KEXEC_SIG
static bool sig_enforce = IS_ENABLED(CONFIG_KEXEC_SIG_FORCE);

void set_kexec_sig_enforced(void)
{
        sig_enforce = true;
}
#endif

static int kexec_calculate_store_digests(struct kimage *image);

/* Maximum size in bytes for kernel/initrd files. */
#define KEXEC_FILE_SIZE_MAX     min_t(s64, 4LL << 30, SSIZE_MAX)

/*
 * Currently this is the only default function that is exported as some
 * architectures need it to do additional handlings.
 * In the future, other default functions may be exported too if required.
 */
int kexec_image_probe_default(struct kimage *image, void *buf,
                              unsigned long buf_len)
{
        const struct kexec_file_ops * const *fops;
        int ret = -ENOEXEC;

        for (fops = &kexec_file_loaders[0]; *fops && (*fops)->probe; ++fops) {
                ret = (*fops)->probe(buf, buf_len);
                if (!ret) {
                        image->fops = *fops;
                        return ret;
                }
        }

        return ret;
}

static void *kexec_image_load_default(struct kimage *image)
{
        if (!image->fops || !image->fops->load)
                return ERR_PTR(-ENOEXEC);

        return image->fops->load(image, image->kernel_buf,
                                 image->kernel_buf_len, image->initrd_buf,
                                 image->initrd_buf_len, image->cmdline_buf,
                                 image->cmdline_buf_len);
}

int kexec_image_post_load_cleanup_default(struct kimage *image)
{
        if (!image->fops || !image->fops->cleanup)
                return 0;

        return image->fops->cleanup(image->image_loader_data);
}

/*
 * 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;

#ifdef CONFIG_IMA_KEXEC
        vfree(image->ima_buffer);
        image->ima_buffer = NULL;
#endif /* CONFIG_IMA_KEXEC */

        /* 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;
}

#ifdef CONFIG_KEXEC_SIG
#ifdef CONFIG_SIGNED_PE_FILE_VERIFICATION
int kexec_kernel_verify_pe_sig(const char *kernel, unsigned long kernel_len)
{
        int ret;

        ret = verify_pefile_signature(kernel, kernel_len,
                                      VERIFY_USE_SECONDARY_KEYRING,
                                      VERIFYING_KEXEC_PE_SIGNATURE);
        if (ret == -ENOKEY && IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING)) {
                ret = verify_pefile_signature(kernel, kernel_len,
                                              VERIFY_USE_PLATFORM_KEYRING,
                                              VERIFYING_KEXEC_PE_SIGNATURE);
        }
        return ret;
}
#endif

static int kexec_image_verify_sig(struct kimage *image, void *buf,
                                  unsigned long buf_len)
{
        if (!image->fops || !image->fops->verify_sig) {
                pr_debug("kernel loader does not support signature verification.\n");
                return -EKEYREJECTED;
        }

        return image->fops->verify_sig(buf, buf_len);
}

static int
kimage_validate_signature(struct kimage *image)
{
        int ret;

        ret = kexec_image_verify_sig(image, image->kernel_buf,
                                     image->kernel_buf_len);
        if (ret) {

                if (sig_enforce) {
                        pr_notice("Enforced kernel signature verification failed (%d).\n", ret);
                        return ret;
                }

                /*
                 * If IMA is guaranteed to appraise a signature on the kexec
                 * image, permit it even if the kernel is otherwise locked
                 * down.
                 */
                if (!ima_appraise_signature(READING_KEXEC_IMAGE) &&
                    security_locked_down(LOCKDOWN_KEXEC))
                        return -EPERM;

                pr_debug("kernel signature verification failed (%d).\n", ret);
        }

        return 0;
}
#endif

/*
 * 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)
{
        ssize_t ret;
        void *ldata;

        ret = kernel_read_file_from_fd(kernel_fd, 0, &image->kernel_buf,
                                       KEXEC_FILE_SIZE_MAX, NULL,
                                       READING_KEXEC_IMAGE);
        if (ret < 0)
                return ret;
        image->kernel_buf_len = 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_SIG
        ret = kimage_validate_signature(image);

        if (ret)
                goto out;
#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, 0, &image->initrd_buf,
                                               KEXEC_FILE_SIZE_MAX, NULL,
                                               READING_KEXEC_INITRAMFS);
                if (ret < 0)
                        goto out;
                image->initrd_buf_len = ret;
                ret = 0;
        }

        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;
                }

                ima_kexec_cmdline(kernel_fd, image->cmdline_buf,
                                  image->cmdline_buf_len - 1);
        }

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

        /* Call image load handler */
        ldata = kexec_image_load_default(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 image_type = (flags & KEXEC_FILE_ON_CRASH) ?
                         KEXEC_TYPE_CRASH : KEXEC_TYPE_DEFAULT;
        struct kimage **dest_image, *image;
        int ret = 0, i;

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

        /* Make sure we have a legal set of flags */
        if (flags != (flags & KEXEC_FILE_FLAGS))
                return -EINVAL;

        image = NULL;

        if (!kexec_trylock())
                return -EBUSY;

        if (image_type == KEXEC_TYPE_CRASH) {
                dest_image = &kexec_crash_image;
                if (kexec_crash_image)
                        arch_kexec_unprotect_crashkres();
        } else {
                dest_image = &kexec_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;

        /*
         * 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\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);

        ret = machine_kexec_post_load(image);
        if (ret)
                goto out;

        /*
         * 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();

        kexec_unlock();
        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(struct resource *res, void *arg)
{
        struct kexec_buf *kbuf = (struct kexec_buf *)arg;
        u64 start = res->start, end = res->end;
        unsigned long sz = end - start + 1;

        /* Returning 0 will take to next memory range */

        /* Don't use memory that will be detected and handled by a driver. */
        if (res->flags & IORESOURCE_SYSRAM_DRIVER_MANAGED)
                return 0;

        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);
}

#ifdef CONFIG_ARCH_KEEP_MEMBLOCK
static int kexec_walk_memblock(struct kexec_buf *kbuf,
                               int (*func)(struct resource *, void *))
{
        int ret = 0;
        u64 i;
        phys_addr_t mstart, mend;
        struct resource res = { };

        if (kbuf->image->type == KEXEC_TYPE_CRASH)
                return func(&crashk_res, kbuf);

        /*
         * Using MEMBLOCK_NONE will properly skip MEMBLOCK_DRIVER_MANAGED. See
         * IORESOURCE_SYSRAM_DRIVER_MANAGED handling in
         * locate_mem_hole_callback().
         */
        if (kbuf->top_down) {
                for_each_free_mem_range_reverse(i, NUMA_NO_NODE, MEMBLOCK_NONE,
                                                &mstart, &mend, NULL) {
                        /*
                         * In memblock, end points to the first byte after the
                         * range while in kexec, end points to the last byte
                         * in the range.
                         */
                        res.start = mstart;
                        res.end = mend - 1;
                        ret = func(&res, kbuf);
                        if (ret)
                                break;
                }
        } else {
                for_each_free_mem_range(i, NUMA_NO_NODE, MEMBLOCK_NONE,
                                        &mstart, &mend, NULL) {
                        /*
                         * In memblock, end points to the first byte after the
                         * range while in kexec, end points to the last byte
                         * in the range.
                         */
                        res.start = mstart;
                        res.end = mend - 1;
                        ret = func(&res, kbuf);
                        if (ret)
                                break;
                }
        }

        return ret;
}
#else
static int kexec_walk_memblock(struct kexec_buf *kbuf,
                               int (*func)(struct resource *, void *))
{
        return 0;
}
#endif

/**
 * kexec_walk_resources - 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.
 */
static int kexec_walk_resources(struct kexec_buf *kbuf,
                                int (*func)(struct resource *, 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;

        /* Arch knows where to place */
        if (kbuf->mem != KEXEC_BUF_MEM_UNKNOWN)
                return 0;

        if (!IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))
                ret = kexec_walk_resources(kbuf, locate_mem_hole_callback);
        else
                ret = kexec_walk_memblock(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_lock 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 = arch_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;

        if (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_KEXEC_PURGATORY))
                return 0;

        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) {
                ret = -ENOMEM;
                goto out_free_desc;
        }

        desc->tfm   = tfm;

        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;

#ifdef CONFIG_CRASH_HOTPLUG
                /* Exclude elfcorehdr segment to allow future changes via hotplug */
                if (j == image->elfcorehdr_index)
                        continue;
#endif

                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;
}

#ifdef CONFIG_ARCH_SUPPORTS_KEXEC_PURGATORY
/*
 * kexec_purgatory_setup_kbuf - prepare buffer to load purgatory.
 * @pi:         Purgatory to be loaded.
 * @kbuf:       Buffer to setup.
 *
 * Allocates the memory needed for the buffer. Caller is responsible to free
 * the memory after use.
 *
 * Return: 0 on success, negative errno on error.
 */
static int kexec_purgatory_setup_kbuf(struct purgatory_info *pi,
                                      struct kexec_buf *kbuf)
{
        const Elf_Shdr *sechdrs;
        unsigned long bss_align;
        unsigned long bss_sz;
        unsigned long align;
        int i, ret;

        sechdrs = (void *)pi->ehdr + pi->ehdr->e_shoff;
        kbuf->buf_align = bss_align = 1;
        kbuf->bufsz = 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 {
                        if (bss_align < align)
                                bss_align = align;
                        bss_sz = ALIGN(bss_sz, align);
                        bss_sz += sechdrs[i].sh_size;
                }
        }
        kbuf->bufsz = ALIGN(kbuf->bufsz, bss_align);
        kbuf->memsz = kbuf->bufsz + bss_sz;
        if (kbuf->buf_align < bss_align)
                kbuf->buf_align = bss_align;

        kbuf->buffer = vzalloc(kbuf->bufsz);
        if (!kbuf->buffer)
                return -ENOMEM;
        pi->purgatory_buf = kbuf->buffer;

        ret = kexec_add_buffer(kbuf);
        if (ret)
                goto out;

        return 0;
out:
        vfree(pi->purgatory_buf);
        pi->purgatory_buf = NULL;
        return ret;
}

/*
 * kexec_purgatory_setup_sechdrs - prepares the pi->sechdrs buffer.
 * @pi:         Purgatory to be loaded.
 * @kbuf:       Buffer prepared to store purgatory.
 *
 * Allocates the memory needed for the buffer. Caller is responsible to free
 * the memory after use.
 *
 * Return: 0 on success, negative errno on error.
 */
static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi,
                                         struct kexec_buf *kbuf)
{
        unsigned long bss_addr;
        unsigned long offset;
        size_t sechdrs_size;
        Elf_Shdr *sechdrs;
        int i;

        /*
         * The section headers in kexec_purgatory are read-only. In order to
         * have them modifiable make a temporary copy.
         */
        sechdrs_size = array_size(sizeof(Elf_Shdr), pi->ehdr->e_shnum);
        sechdrs = vzalloc(sechdrs_size);
        if (!sechdrs)
                return -ENOMEM;
        memcpy(sechdrs, (void *)pi->ehdr + pi->ehdr->e_shoff, sechdrs_size);
        pi->sechdrs = sechdrs;

        offset = 0;
        bss_addr = kbuf->mem + kbuf->bufsz;
        kbuf->image->start = pi->ehdr->e_entry;

        for (i = 0; i < pi->ehdr->e_shnum; i++) {
                unsigned long align;
                void *src, *dst;

                if (!(sechdrs[i].sh_flags & SHF_ALLOC))
                        continue;

                align = sechdrs[i].sh_addralign;
                if (sechdrs[i].sh_type == SHT_NOBITS) {
                        bss_addr = ALIGN(bss_addr, align);
                        sechdrs[i].sh_addr = bss_addr;
                        bss_addr += sechdrs[i].sh_size;
                        continue;
                }

                offset = ALIGN(offset, align);

                /*
                 * Check if the segment contains the entry point, if so,
                 * calculate the value of image->start based on it.
                 * If the compiler has produced more than one .text section
                 * (Eg: .text.hot), they are generally after the main .text
                 * section, and they shall not be used to calculate
                 * image->start. So do not re-calculate image->start if it
                 * is not set to the initial value, and warn the user so they
                 * have a chance to fix their purgatory's linker script.
                 */
                if (sechdrs[i].sh_flags & SHF_EXECINSTR &&
                    pi->ehdr->e_entry >= sechdrs[i].sh_addr &&
                    pi->ehdr->e_entry < (sechdrs[i].sh_addr
                                         + sechdrs[i].sh_size) &&
                    !WARN_ON(kbuf->image->start != pi->ehdr->e_entry)) {
                        kbuf->image->start -= sechdrs[i].sh_addr;
                        kbuf->image->start += kbuf->mem + offset;
                }

                src = (void *)pi->ehdr + sechdrs[i].sh_offset;
                dst = pi->purgatory_buf + offset;
                memcpy(dst, src, sechdrs[i].sh_size);

                sechdrs[i].sh_addr = kbuf->mem + offset;
                sechdrs[i].sh_offset = offset;
                offset += sechdrs[i].sh_size;
        }

        return 0;
}

static int kexec_apply_relocations(struct kimage *image)
{
        int i, ret;
        struct purgatory_info *pi = &image->purgatory_info;
        const Elf_Shdr *sechdrs;

        sechdrs = (void *)pi->ehdr + pi->ehdr->e_shoff;

        for (i = 0; i < pi->ehdr->e_shnum; i++) {
                const Elf_Shdr *relsec;
                const Elf_Shdr *symtab;
                Elf_Shdr *section;

                relsec = sechdrs + i;

                if (relsec->sh_type != SHT_RELA &&
                    relsec->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 (relsec->sh_info >= pi->ehdr->e_shnum ||
                    relsec->sh_link >= pi->ehdr->e_shnum)
                        return -ENOEXEC;

                section = pi->sechdrs + relsec->sh_info;
                symtab = sechdrs + relsec->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 (relsec->sh_type == SHT_RELA)
                        ret = arch_kexec_apply_relocations_add(pi, section,
                                                               relsec, symtab);
                else if (relsec->sh_type == SHT_REL)
                        ret = arch_kexec_apply_relocations(pi, section,
                                                           relsec, symtab);
                if (ret)
                        return ret;
        }

        return 0;

}

/*
 * kexec_load_purgatory - Load and relocate the purgatory object.
 * @image:      Image to add the purgatory to.
 * @kbuf:       Memory parameters to use.
 *
 * Allocates the memory needed for image->purgatory_info.sechdrs and
 * image->purgatory_info.purgatory_buf/kbuf->buffer. Caller is responsible
 * to free the memory after use.
 *
 * Return: 0 on success, negative errno on error.
 */
int kexec_load_purgatory(struct kimage *image, struct kexec_buf *kbuf)
{
        struct purgatory_info *pi = &image->purgatory_info;
        int ret;

        if (kexec_purgatory_size <= 0)
                return -EINVAL;

        pi->ehdr = (const Elf_Ehdr *)kexec_purgatory;

        ret = kexec_purgatory_setup_kbuf(pi, kbuf);
        if (ret)
                return ret;

        ret = kexec_purgatory_setup_sechdrs(pi, kbuf);
        if (ret)
                goto out_free_kbuf;

        ret = kexec_apply_relocations(image);
        if (ret)
                goto out;

        return 0;
out:
        vfree(pi->sechdrs);
        pi->sechdrs = NULL;
out_free_kbuf:
        vfree(pi->purgatory_buf);
        pi->purgatory_buf = NULL;
        return ret;
}

/*
 * kexec_purgatory_find_symbol - find a symbol in the purgatory
 * @pi:         Purgatory to search in.
 * @name:       Name of the symbol.
 *
 * Return: pointer to symbol in read-only symtab on success, NULL on error.
 */
static const Elf_Sym *kexec_purgatory_find_symbol(struct purgatory_info *pi,
                                                  const char *name)
{
        const Elf_Shdr *sechdrs;
        const Elf_Ehdr *ehdr;
        const Elf_Sym *syms;
        const char *strtab;
        int i, k;

        if (!pi->ehdr)
                return NULL;

        ehdr = pi->ehdr;
        sechdrs = (void *)ehdr + ehdr->e_shoff;

        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 = (void *)ehdr + sechdrs[sechdrs[i].sh_link].sh_offset;
                syms = (void *)ehdr + 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;
        const 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)
{
        struct purgatory_info *pi = &image->purgatory_info;
        const Elf_Sym *sym;
        Elf_Shdr *sec;
        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;
        }

        sec = pi->sechdrs + sym->st_shndx;

        if (sec->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 = (char *)pi->purgatory_buf + sec->sh_offset + sym->st_value;

        if (get_value)
                memcpy((void *)buf, sym_buf, size);
        else
                memcpy((void *)sym_buf, buf, size);

        return 0;
}
#endif /* CONFIG_ARCH_SUPPORTS_KEXEC_PURGATORY */