From: Philipp Rudo <prudo@xxxxxxxxxxxxxxxxxx> Subject: kernel/kexec_file.c: use read-only sections in arch_kexec_apply_relocations* When the relocations are applied to the purgatory only the section the relocations are applied to is writable. The other sections, i.e. the symtab and .rel/.rela, are in read-only kexec_purgatory. Highlight this by marking the corresponding variables as 'const'. While at it also change the signatures of arch_kexec_apply_relocations* to take section pointers instead of just the index of the relocation section. This removes the second lookup and sanity check of the sections in arch code. Link: http://lkml.kernel.org/r/20180321112751.22196-6-prudo@xxxxxxxxxxxxxxxxxx Signed-off-by: Philipp Rudo <prudo@xxxxxxxxxxxxxxxxxx> Acked-by: Dave Young <dyoung@xxxxxxxxxx> Cc: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx> Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxxxxxxx> Cc: Vivek Goyal <vgoyal@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/x86/kernel/machine_kexec_64.c | 56 ++++++++---------------- include/linux/kexec.h | 13 +++-- kernel/kexec_file.c | 63 ++++++++++++++++++--------- 3 files changed, 71 insertions(+), 61 deletions(-) diff -puN arch/x86/kernel/machine_kexec_64.c~kexec_file-use-read-only-sections-in-arch_kexec_apply_relocations arch/x86/kernel/machine_kexec_64.c --- a/arch/x86/kernel/machine_kexec_64.c~kexec_file-use-read-only-sections-in-arch_kexec_apply_relocations +++ a/arch/x86/kernel/machine_kexec_64.c @@ -382,52 +382,36 @@ void *arch_kexec_kernel_image_load(struc /* * Apply purgatory relocations. * - * ehdr: Pointer to elf headers - * sechdrs: Pointer to section headers. - * relsec: section index of SHT_RELA section. + * @pi: Purgatory to be relocated. + * @section: Section relocations applying to. + * @relsec: Section containing RELAs. + * @symtabsec: Corresponding symtab. * * TODO: Some of the code belongs to generic code. Move that in kexec.c. */ -int arch_kexec_apply_relocations_add(const Elf64_Ehdr *ehdr, - Elf64_Shdr *sechdrs, unsigned int relsec) +int arch_kexec_apply_relocations_add(struct purgatory_info *pi, + Elf_Shdr *section, const Elf_Shdr *relsec, + const Elf_Shdr *symtabsec) { unsigned int i; Elf64_Rela *rel; Elf64_Sym *sym; void *location; - Elf64_Shdr *section, *symtabsec; unsigned long address, sec_base, value; const char *strtab, *name, *shstrtab; + const Elf_Shdr *sechdrs; - /* - * ->sh_offset has been modified to keep the pointer to section - * contents in memory - */ - rel = (void *)sechdrs[relsec].sh_offset; - - /* Section to which relocations apply */ - section = &sechdrs[sechdrs[relsec].sh_info]; - - pr_debug("Applying relocate section %u to %u\n", relsec, - sechdrs[relsec].sh_info); - - /* Associated symbol table */ - symtabsec = &sechdrs[sechdrs[relsec].sh_link]; - - /* String table */ - if (symtabsec->sh_link >= ehdr->e_shnum) { - /* Invalid strtab section number */ - pr_err("Invalid string table section index %d\n", - symtabsec->sh_link); - return -ENOEXEC; - } + /* String & section header string table */ + sechdrs = (void *)pi->ehdr + pi->ehdr->e_shoff; + strtab = (char *)pi->ehdr + sechdrs[symtabsec->sh_link].sh_offset; + shstrtab = (char *)pi->ehdr + sechdrs[pi->ehdr->e_shstrndx].sh_offset; - strtab = (char *)sechdrs[symtabsec->sh_link].sh_offset; + rel = (void *)pi->ehdr + relsec->sh_offset; - /* section header string table */ - shstrtab = (char *)sechdrs[ehdr->e_shstrndx].sh_offset; + pr_debug("Applying relocate section %s to %u\n", + shstrtab + relsec->sh_name, relsec->sh_info); - for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) { + for (i = 0; i < relsec->sh_size / sizeof(*rel); i++) { /* * rel[i].r_offset contains byte offset from beginning @@ -450,8 +434,8 @@ int arch_kexec_apply_relocations_add(con * to apply. ELF64_R_SYM() and ELF64_R_TYPE() macros get * these respectively. */ - sym = (Elf64_Sym *)symtabsec->sh_offset + - ELF64_R_SYM(rel[i].r_info); + sym = (void *)pi->ehdr + symtabsec->sh_offset; + sym += ELF64_R_SYM(rel[i].r_info); if (sym->st_name) name = strtab + sym->st_name; @@ -474,12 +458,12 @@ int arch_kexec_apply_relocations_add(con if (sym->st_shndx == SHN_ABS) sec_base = 0; - else if (sym->st_shndx >= ehdr->e_shnum) { + else if (sym->st_shndx >= pi->ehdr->e_shnum) { pr_err("Invalid section %d for symbol %s\n", sym->st_shndx, name); return -ENOEXEC; } else - sec_base = sechdrs[sym->st_shndx].sh_addr; + sec_base = pi->sechdrs[sym->st_shndx].sh_addr; value = sym->st_value; value += sec_base; diff -puN include/linux/kexec.h~kexec_file-use-read-only-sections-in-arch_kexec_apply_relocations include/linux/kexec.h --- a/include/linux/kexec.h~kexec_file-use-read-only-sections-in-arch_kexec_apply_relocations +++ a/include/linux/kexec.h @@ -171,6 +171,15 @@ struct kexec_buf { bool top_down; }; +int __weak arch_kexec_apply_relocations_add(struct purgatory_info *pi, + Elf_Shdr *section, + const Elf_Shdr *relsec, + const Elf_Shdr *symtab); +int __weak arch_kexec_apply_relocations(struct purgatory_info *pi, + Elf_Shdr *section, + const Elf_Shdr *relsec, + const Elf_Shdr *symtab); + int __weak arch_kexec_walk_mem(struct kexec_buf *kbuf, int (*func)(struct resource *, void *)); extern int kexec_add_buffer(struct kexec_buf *kbuf); @@ -304,10 +313,6 @@ int crash_shrink_memory(unsigned long ne size_t crash_get_memory_size(void); void crash_free_reserved_phys_range(unsigned long begin, unsigned long end); -int __weak arch_kexec_apply_relocations_add(const Elf_Ehdr *ehdr, - Elf_Shdr *sechdrs, unsigned int relsec); -int __weak arch_kexec_apply_relocations(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, - unsigned int relsec); void arch_kexec_protect_crashkres(void); void arch_kexec_unprotect_crashkres(void); diff -puN kernel/kexec_file.c~kexec_file-use-read-only-sections-in-arch_kexec_apply_relocations kernel/kexec_file.c --- a/kernel/kexec_file.c~kexec_file-use-read-only-sections-in-arch_kexec_apply_relocations +++ a/kernel/kexec_file.c @@ -110,19 +110,35 @@ int __weak arch_kexec_kernel_verify_sig( } #endif -/* Apply relocations of type RELA */ +/* + * arch_kexec_apply_relocations_add - apply relocations of type RELA + * @pi: Purgatory to be relocated. + * @section: Section relocations applying to. + * @relsec: Section containing RELAs. + * @symtab: Corresponding symtab. + * + * Return: 0 on success, negative errno on error. + */ int __weak -arch_kexec_apply_relocations_add(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, - unsigned int relsec) +arch_kexec_apply_relocations_add(struct purgatory_info *pi, Elf_Shdr *section, + const Elf_Shdr *relsec, const Elf_Shdr *symtab) { pr_err("RELA relocation unsupported.\n"); return -ENOEXEC; } -/* Apply relocations of type REL */ +/* + * arch_kexec_apply_relocations - apply relocations of type REL + * @pi: Purgatory to be relocated. + * @section: Section relocations applying to. + * @relsec: Section containing RELs. + * @symtab: Corresponding symtab. + * + * Return: 0 on success, negative errno on error. + */ int __weak -arch_kexec_apply_relocations(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, - unsigned int relsec) +arch_kexec_apply_relocations(struct purgatory_info *pi, Elf_Shdr *section, + const Elf_Shdr *relsec, const Elf_Shdr *symtab) { pr_err("REL relocation unsupported.\n"); return -ENOEXEC; @@ -879,14 +895,19 @@ static int kexec_apply_relocations(struc { int i, ret; struct purgatory_info *pi = &image->purgatory_info; - Elf_Shdr *sechdrs = pi->sechdrs; + const Elf_Shdr *sechdrs; + + sechdrs = (void *)pi->ehdr + pi->ehdr->e_shoff; - /* Apply relocations */ for (i = 0; i < pi->ehdr->e_shnum; i++) { - Elf_Shdr *section, *symtab; + const Elf_Shdr *relsec; + const Elf_Shdr *symtab; + Elf_Shdr *section; + + relsec = sechdrs + i; - if (sechdrs[i].sh_type != SHT_RELA && - sechdrs[i].sh_type != SHT_REL) + if (relsec->sh_type != SHT_RELA && + relsec->sh_type != SHT_REL) continue; /* @@ -895,12 +916,12 @@ static int kexec_apply_relocations(struc * 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) + if (relsec->sh_info >= pi->ehdr->e_shnum || + relsec->sh_link >= pi->ehdr->e_shnum) return -ENOEXEC; - section = &sechdrs[sechdrs[i].sh_info]; - symtab = &sechdrs[sechdrs[i].sh_link]; + section = pi->sechdrs + relsec->sh_info; + symtab = sechdrs + relsec->sh_link; if (!(section->sh_flags & SHF_ALLOC)) continue; @@ -917,12 +938,12 @@ static int kexec_apply_relocations(struc * 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 (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; } _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
