diff options
| -rw-r--r-- | Documentation/ABI/testing/sysfs-kernel-livepatch | 6 | ||||
| -rw-r--r-- | include/linux/livepatch.h | 24 | ||||
| -rw-r--r-- | kernel/livepatch/core.c | 164 |
3 files changed, 74 insertions, 120 deletions
diff --git a/Documentation/ABI/testing/sysfs-kernel-livepatch b/Documentation/ABI/testing/sysfs-kernel-livepatch index 5bf42a840b22..da87f43aec58 100644 --- a/Documentation/ABI/testing/sysfs-kernel-livepatch +++ b/Documentation/ABI/testing/sysfs-kernel-livepatch @@ -33,7 +33,7 @@ Description: The object directory contains subdirectories for each function that is patched within the object. -What: /sys/kernel/livepatch/<patch>/<object>/<function> +What: /sys/kernel/livepatch/<patch>/<object>/<function,sympos> Date: Nov 2014 KernelVersion: 3.19.0 Contact: live-patching@vger.kernel.org @@ -41,4 +41,8 @@ Description: The function directory contains attributes regarding the properties and state of the patched function. + The directory name contains the patched function name and a + sympos number corresponding to the nth occurrence of the symbol + name in kallsyms for the patched object. + There are currently no such attributes. diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index 31db7a05dd36..a8828652f794 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; @@ -66,8 +67,7 @@ struct klp_func { /** * struct klp_reloc - relocation structure for live patching * @loc: address where the relocation will be written - * @val: address of the referenced symbol (optional, - * vmlinux patches only) + * @sympos: position in kallsyms to disambiguate symbols (optional) * @type: ELF relocation type * @name: name of the referenced symbol (for lookup/verification) * @addend: offset from the referenced symbol @@ -75,7 +75,7 @@ struct klp_func { */ struct klp_reloc { unsigned long loc; - unsigned long val; + unsigned long sympos; unsigned long type; const char *name; int addend; diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index db545cbcdb89..94893e844e44 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; } @@ -197,66 +203,6 @@ static int klp_find_object_symbol(const char *objname, const char *name, return -EINVAL; } -struct klp_verify_args { - const char *name; - const unsigned long addr; -}; - -static int klp_verify_callback(void *data, const char *name, - struct module *mod, unsigned long addr) -{ - struct klp_verify_args *args = data; - - if (!mod && - !strcmp(args->name, name) && - args->addr == addr) - return 1; - - return 0; -} - -static int klp_verify_vmlinux_symbol(const char *name, unsigned long addr) -{ - struct klp_verify_args args = { - .name = name, - .addr = addr, - }; - int ret; - - mutex_lock(&module_mutex); - ret = kallsyms_on_each_symbol(klp_verify_callback, &args); - mutex_unlock(&module_mutex); - - if (!ret) { - pr_err("symbol '%s' not found at specified address 0x%016lx, kernel mismatch?\n", - name, addr); - return -EINVAL; - } - - 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). @@ -276,14 +222,18 @@ 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, struct klp_object *obj) { int ret; + unsigned long val; struct klp_reloc *reloc; if (WARN_ON(!klp_is_object_loaded(obj))) @@ -293,35 +243,27 @@ static int klp_write_object_relocations(struct module *pmod, return -EINVAL; for (reloc = obj->relocs; reloc->name; reloc++) { - if (!klp_is_module(obj)) { - -#if defined(CONFIG_RANDOMIZE_BASE) - /* If KASLR has been enabled, adjust old value accordingly */ - if (kaslr_enabled()) - reloc->val += kaslr_offset(); -#endif - ret = klp_verify_vmlinux_symbol(reloc->name, - reloc->val); - if (ret) - return ret; - } else { - /* module, reloc->val needs to be discovered */ - if (reloc->external) - ret = klp_find_external_symbol(pmod, - reloc->name, - &reloc->val); - else - ret = klp_find_object_symbol(obj->mod->name, - reloc->name, - &reloc->val); - if (ret) - return ret; - } + /* discover the address of the referenced symbol */ + if (reloc->external) { + if (reloc->sympos > 0) { + pr_err("non-zero sympos for external reloc symbol '%s' is not supported\n", + reloc->name); + return -EINVAL; + } + ret = klp_find_external_symbol(pmod, reloc->name, &val); + } else + ret = klp_find_object_symbol(obj->name, + reloc->name, + reloc->sympos, + &val); + if (ret) + return ret; + ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc, - reloc->val + reloc->addend); + val + reloc->addend); if (ret) { pr_err("relocation failed for symbol '%s' at 0x%016lx (%d)\n", - reloc->name, reloc->val, ret); + reloc->name, val, ret); return ret; } } @@ -593,7 +535,7 @@ EXPORT_SYMBOL_GPL(klp_enable_patch); * /sys/kernel/livepatch/<patch> * /sys/kernel/livepatch/<patch>/enabled * /sys/kernel/livepatch/<patch>/<object> - * /sys/kernel/livepatch/<patch>/<object>/<func> + * /sys/kernel/livepatch/<patch>/<object>/<function,sympos> */ static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr, @@ -738,8 +680,14 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func) INIT_LIST_HEAD(&func->stack_node); func->state = KLP_DISABLED; + /* The format for the sysfs directory is <function,sympos> where sympos + * is the nth occurrence of this symbol in kallsyms for the patched + * object. If the user selects 0 for old_sympos, then 1 will be used + * since a unique symbol will be the first occurrence. + */ return kobject_init_and_add(&func->kobj, &klp_ktype_func, - &obj->kobj, "%s", func->old_name); + &obj->kobj, "%s,%lu", func->old_name, + func->old_sympos ? func->old_sympos : 1); } /* parts of the initialization that is done only when the object is loaded */ @@ -756,7 +704,9 @@ 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; } |