diff options
| -rw-r--r-- | include/linux/livepatch.h | 14 | ||||
| -rw-r--r-- | kernel/livepatch/core.c | 137 | ||||
| -rw-r--r-- | kernel/module.c | 10 |
3 files changed, 106 insertions, 55 deletions
diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index e894e74905f3..c4302e9a5905 100644 --- a/include/linux/livepatch.h +++ b/include/linux/livepatch.h @@ -234,6 +234,11 @@ void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor); struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id); struct klp_state *klp_get_prev_state(unsigned long id); +int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs, + const char *shstrtab, const char *strtab, + unsigned int symindex, unsigned int secindex, + const char *objname); + #else /* !CONFIG_LIVEPATCH */ static inline int klp_module_coming(struct module *mod) { return 0; } @@ -242,6 +247,15 @@ static inline bool klp_patch_pending(struct task_struct *task) { return false; } static inline void klp_update_patch_state(struct task_struct *task) {} static inline void klp_copy_process(struct task_struct *child) {} +static inline +int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs, + const char *shstrtab, const char *strtab, + unsigned int symindex, unsigned int secindex, + const char *objname) +{ + return 0; +} + #endif /* CONFIG_LIVEPATCH */ #endif /* _LINUX_LIVEPATCH_H_ */ diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index 40cfac8156fd..c02791e5c75b 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -191,12 +191,12 @@ static int klp_find_object_symbol(const char *objname, const char *name, return -EINVAL; } -static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod) +static int klp_resolve_symbols(Elf64_Shdr *sechdrs, const char *strtab, + unsigned int symndx, Elf_Shdr *relasec) { int i, cnt, vmlinux, ret; char objname[MODULE_NAME_LEN]; char symname[KSYM_NAME_LEN]; - char *strtab = pmod->core_kallsyms.strtab; Elf_Rela *relas; Elf_Sym *sym; unsigned long sympos, addr; @@ -216,7 +216,7 @@ static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod) relas = (Elf_Rela *) relasec->sh_addr; /* For each rela in this klp relocation section */ for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) { - sym = pmod->core_kallsyms.symtab + ELF_R_SYM(relas[i].r_info); + sym = (Elf64_Sym *)sechdrs[symndx].sh_addr + ELF_R_SYM(relas[i].r_info); if (sym->st_shndx != SHN_LIVEPATCH) { pr_err("symbol %s is not marked as a livepatch symbol\n", strtab + sym->st_name); @@ -246,54 +246,59 @@ static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod) return 0; } -static int klp_write_object_relocations(struct module *pmod, - struct klp_object *obj) +/* + * At a high-level, there are two types of klp relocation sections: those which + * reference symbols which live in vmlinux; and those which reference symbols + * which live in other modules. This function is called for both types: + * + * 1) When a klp module itself loads, the module code calls this function to + * write vmlinux-specific klp relocations (.klp.rela.vmlinux.* sections). + * These relocations are written to the klp module text to allow the patched + * code/data to reference unexported vmlinux symbols. They're written as + * early as possible to ensure that other module init code (.e.g., + * jump_label_apply_nops) can access any unexported vmlinux symbols which + * might be referenced by the klp module's special sections. + * + * 2) When a to-be-patched module loads -- or is already loaded when a + * corresponding klp module loads -- klp code calls this function to write + * module-specific klp relocations (.klp.rela.{module}.* sections). These + * are written to the klp module text to allow the patched code/data to + * reference symbols which live in the to-be-patched module or one of its + * module dependencies. Exported symbols are supported, in addition to + * unexported symbols, in order to enable late module patching, which allows + * the to-be-patched module to be loaded and patched sometime *after* the + * klp module is loaded. + */ +int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs, + const char *shstrtab, const char *strtab, + unsigned int symndx, unsigned int secndx, + const char *objname) { - int i, cnt, ret = 0; - const char *objname, *secname; + int cnt, ret; char sec_objname[MODULE_NAME_LEN]; - Elf_Shdr *sec; + Elf_Shdr *sec = sechdrs + secndx; - if (WARN_ON(!klp_is_object_loaded(obj))) + /* + * Format: .klp.rela.sec_objname.section_name + * See comment in klp_resolve_symbols() for an explanation + * of the selected field width value. + */ + cnt = sscanf(shstrtab + sec->sh_name, ".klp.rela.%55[^.]", + sec_objname); + if (cnt != 1) { + pr_err("section %s has an incorrectly formatted name\n", + shstrtab + sec->sh_name); return -EINVAL; + } - objname = klp_is_module(obj) ? obj->name : "vmlinux"; - - /* For each klp relocation section */ - for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) { - sec = pmod->klp_info->sechdrs + i; - secname = pmod->klp_info->secstrings + sec->sh_name; - if (!(sec->sh_flags & SHF_RELA_LIVEPATCH)) - continue; - - /* - * Format: .klp.rela.sec_objname.section_name - * See comment in klp_resolve_symbols() for an explanation - * of the selected field width value. - */ - cnt = sscanf(secname, ".klp.rela.%55[^.]", sec_objname); - if (cnt != 1) { - pr_err("section %s has an incorrectly formatted name\n", - secname); - ret = -EINVAL; - break; - } - - if (strcmp(objname, sec_objname)) - continue; - - ret = klp_resolve_symbols(sec, pmod); - if (ret) - break; + if (strcmp(objname ? objname : "vmlinux", sec_objname)) + return 0; - ret = apply_relocate_add(pmod->klp_info->sechdrs, - pmod->core_kallsyms.strtab, - pmod->klp_info->symndx, i, pmod); - if (ret) - break; - } + ret = klp_resolve_symbols(sechdrs, strtab, symndx, sec); + if (ret) + return ret; - return ret; + return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod); } /* @@ -730,6 +735,28 @@ void __weak arch_klp_init_object_loaded(struct klp_patch *patch, { } +int klp_apply_object_relocs(struct klp_patch *patch, struct klp_object *obj) +{ + int i, ret; + struct klp_modinfo *info = patch->mod->klp_info; + + for (i = 1; i < info->hdr.e_shnum; i++) { + Elf_Shdr *sec = info->sechdrs + i; + + if (!(sec->sh_flags & SHF_RELA_LIVEPATCH)) + continue; + + ret = klp_apply_section_relocs(patch->mod, info->sechdrs, + info->secstrings, + patch->mod->core_kallsyms.strtab, + info->symndx, i, obj->name); + if (ret) + return ret; + } + + return 0; +} + /* parts of the initialization that is done only when the object is loaded */ static int klp_init_object_loaded(struct klp_patch *patch, struct klp_object *obj) @@ -738,18 +765,26 @@ static int klp_init_object_loaded(struct klp_patch *patch, int ret; mutex_lock(&text_mutex); - module_disable_ro(patch->mod); - ret = klp_write_object_relocations(patch->mod, obj); - if (ret) { - module_enable_ro(patch->mod, true); - mutex_unlock(&text_mutex); - return ret; + + if (klp_is_module(obj)) { + /* + * Only write module-specific relocations here + * (.klp.rela.{module}.*). vmlinux-specific relocations were + * written earlier during the initialization of the klp module + * itself. + */ + ret = klp_apply_object_relocs(patch, obj); + if (ret) { + module_enable_ro(patch->mod, true); + mutex_unlock(&text_mutex); + return ret; + } } arch_klp_init_object_loaded(patch, obj); - module_enable_ro(patch->mod, true); + module_enable_ro(patch->mod, true); mutex_unlock(&text_mutex); klp_for_each_func(obj, func) { diff --git a/kernel/module.c b/kernel/module.c index 646f1e2330d2..fdd9f6970e9a 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -2334,11 +2334,13 @@ static int apply_relocations(struct module *mod, const struct load_info *info) if (!(info->sechdrs[infosec].sh_flags & SHF_ALLOC)) continue; - /* Livepatch relocation sections are applied by livepatch */ if (info->sechdrs[i].sh_flags & SHF_RELA_LIVEPATCH) - continue; - - if (info->sechdrs[i].sh_type == SHT_REL) + err = klp_apply_section_relocs(mod, info->sechdrs, + info->secstrings, + info->strtab, + info->index.sym, i, + NULL); + else if (info->sechdrs[i].sh_type == SHT_REL) err = apply_relocate(info->sechdrs, info->strtab, info->index.sym, i, mod); else if (info->sechdrs[i].sh_type == SHT_RELA) |