diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/kexec.c | 544 |
1 files changed, 543 insertions, 1 deletions
diff --git a/kernel/kexec.c b/kernel/kexec.c index 9b46219254dd..669e331aa9ec 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -42,6 +42,9 @@ #include <asm/io.h> #include <asm/sections.h> +#include <crypto/hash.h> +#include <crypto/sha.h> + /* Per cpu memory for storing cpu states in case of system crash. */ note_buf_t __percpu *crash_notes; @@ -54,6 +57,15 @@ size_t vmcoreinfo_max_size = sizeof(vmcoreinfo_data); /* Flag to indicate we are going to kexec a new kernel */ bool kexec_in_progress = false; +/* + * 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); + /* Location of the reserved area for the crash kernel */ struct resource crashk_res = { .name = "Crash kernel", @@ -404,6 +416,24 @@ void __weak arch_kimage_file_post_load_cleanup(struct kimage *image) { } +/* 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 comand line. This is temporary * memory allocation which is not needed any more after these buffers have @@ -411,6 +441,8 @@ void __weak arch_kimage_file_post_load_cleanup(struct kimage *image) */ static void kimage_file_post_load_cleanup(struct kimage *image) { + struct purgatory_info *pi = &image->purgatory_info; + vfree(image->kernel_buf); image->kernel_buf = NULL; @@ -420,6 +452,12 @@ static void kimage_file_post_load_cleanup(struct kimage *image) 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); } @@ -1105,7 +1143,7 @@ static int kimage_load_crash_segment(struct kimage *image, } ubytes -= uchunk; maddr += mchunk; - buf += mchunk; + buf += mchunk; mbytes -= mchunk; } out: @@ -1340,6 +1378,10 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd, 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; @@ -2092,6 +2134,506 @@ int kexec_add_buffer(struct kimage *image, char *buffer, unsigned long bufsz, 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 archicture 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; +} /* * Move into place and start executing a preloaded standalone |