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 000000000000..6a9a3f2a0e8e
--- /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;
+}