diff options
| -rw-r--r-- | include/linux/livepatch.h | 19 | ||||
| -rw-r--r-- | kernel/livepatch/core.c | 72 |
2 files changed, 41 insertions, 50 deletions
diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index 31db7a05dd36..b60e8abab0ab 100644 --- a/include/linux/livepatch.h +++ b/include/linux/livepatch.h @@ -37,8 +37,9 @@ enum klp_state { * struct klp_func - function structure for live patching * @old_name: name of the function to be patched * @new_func: pointer to the patched function code - * @old_addr: a hint conveying at what address the old function - * can be found (optional, vmlinux patches only) + * @old_sympos: a hint indicating which symbol position the old function + * can be found (optional) + * @old_addr: the address of the function being patched * @kobj: kobject for sysfs resources * @state: tracks function-level patch application state * @stack_node: list node for klp_ops func_stack list @@ -48,16 +49,16 @@ struct klp_func { const char *old_name; void *new_func; /* - * The old_addr field is optional and can be used to resolve - * duplicate symbol names in the vmlinux object. If this - * information is not present, the symbol is located by name - * with kallsyms. If the name is not unique and old_addr is - * not provided, the patch application fails as there is no - * way to resolve the ambiguity. + * The old_sympos field is optional and can be used to resolve + * duplicate symbol names in livepatch objects. If this field is zero, + * it is expected the symbol is unique, otherwise patching fails. If + * this value is greater than zero then that occurrence of the symbol + * in kallsyms for the given object is used. */ - unsigned long old_addr; + unsigned long old_sympos; /* internal */ + unsigned long old_addr; struct kobject kobj; enum klp_state state; struct list_head stack_node; diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index db545cbcdb89..e416f96e938d 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -135,13 +135,8 @@ struct klp_find_arg { const char *objname; const char *name; unsigned long addr; - /* - * If count == 0, the symbol was not found. If count == 1, a unique - * match was found and addr is set. If count > 1, there is - * unresolvable ambiguity among "count" number of symbols with the same - * name in the same object. - */ unsigned long count; + unsigned long pos; }; static int klp_find_callback(void *data, const char *name, @@ -158,37 +153,48 @@ static int klp_find_callback(void *data, const char *name, if (args->objname && strcmp(args->objname, mod->name)) return 0; - /* - * args->addr might be overwritten if another match is found - * but klp_find_object_symbol() handles this and only returns the - * addr if count == 1. - */ args->addr = addr; args->count++; + /* + * Finish the search when the symbol is found for the desired position + * or the position is not defined for a non-unique symbol. + */ + if ((args->pos && (args->count == args->pos)) || + (!args->pos && (args->count > 1))) + return 1; + return 0; } static int klp_find_object_symbol(const char *objname, const char *name, - unsigned long *addr) + unsigned long sympos, unsigned long *addr) { struct klp_find_arg args = { .objname = objname, .name = name, .addr = 0, - .count = 0 + .count = 0, + .pos = sympos, }; mutex_lock(&module_mutex); kallsyms_on_each_symbol(klp_find_callback, &args); mutex_unlock(&module_mutex); - if (args.count == 0) + /* + * Ensure an address was found. If sympos is 0, ensure symbol is unique; + * otherwise ensure the symbol position count matches sympos. + */ + if (args.addr == 0) pr_err("symbol '%s' not found in symbol table\n", name); - else if (args.count > 1) + else if (args.count > 1 && sympos == 0) { pr_err("unresolvable ambiguity (%lu matches) on symbol '%s' in object '%s'\n", args.count, name, objname); - else { + } else if (sympos != args.count && sympos > 0) { + pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n", + sympos, name, objname ? objname : "vmlinux"); + } else { *addr = args.addr; return 0; } @@ -236,27 +242,6 @@ static int klp_verify_vmlinux_symbol(const char *name, unsigned long addr) return 0; } -static int klp_find_verify_func_addr(struct klp_object *obj, - struct klp_func *func) -{ - int ret; - -#if defined(CONFIG_RANDOMIZE_BASE) - /* If KASLR has been enabled, adjust old_addr accordingly */ - if (kaslr_enabled() && func->old_addr) - func->old_addr += kaslr_offset(); -#endif - - if (!func->old_addr || klp_is_module(obj)) - ret = klp_find_object_symbol(obj->name, func->old_name, - &func->old_addr); - else - ret = klp_verify_vmlinux_symbol(func->old_name, - func->old_addr); - - return ret; -} - /* * external symbols are located outside the parent object (where the parent * object is either vmlinux or the kmod being patched). @@ -276,8 +261,11 @@ static int klp_find_external_symbol(struct module *pmod, const char *name, } preempt_enable(); - /* otherwise check if it's in another .o within the patch module */ - return klp_find_object_symbol(pmod->name, name, addr); + /* + * Check if it's in another .o within the patch module. This also + * checks that the external symbol is unique. + */ + return klp_find_object_symbol(pmod->name, name, 0, addr); } static int klp_write_object_relocations(struct module *pmod, @@ -313,7 +301,7 @@ static int klp_write_object_relocations(struct module *pmod, else ret = klp_find_object_symbol(obj->mod->name, reloc->name, - &reloc->val); + 0, &reloc->val); if (ret) return ret; } @@ -756,7 +744,9 @@ static int klp_init_object_loaded(struct klp_patch *patch, } klp_for_each_func(obj, func) { - ret = klp_find_verify_func_addr(obj, func); + ret = klp_find_object_symbol(obj->name, func->old_name, + func->old_sympos, + &func->old_addr); if (ret) return ret; } |