From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752630AbbKLRAJ (ORCPT ); Thu, 12 Nov 2015 12:00:09 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:42129 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750824AbbKLRAH (ORCPT ); Thu, 12 Nov 2015 12:00:07 -0500 From: Chris J Arges To: live-patching@vger.kernel.org Cc: jeyu@redhat.com, Chris J Arges , Josh Poimboeuf , Seth Jennings , Jiri Kosina , Vojtech Pavlik , linux-kernel@vger.kernel.org Subject: [PATCH 1/4 v5] livepatch: add old_sympos as disambiguator field to klp_func Date: Thu, 12 Nov 2015 10:59:50 -0600 Message-Id: <1447347595-30728-2-git-send-email-chris.j.arges@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1447347595-30728-1-git-send-email-chris.j.arges@canonical.com> References: <1447259366-7055-1-git-send-email-chris.j.arges@canonical.com> <1447347595-30728-1-git-send-email-chris.j.arges@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In cases of duplicate symbols, old_sympos will be used to disambiguate instead of old_addr. By default old_sympos will be 0, and patching will only succeed if the symbol is unique. Specifying a positive value will ensure that occurrence of the symbol in kallsyms for the patched object will be used for patching if it is valid. In addition, make old_addr an internal structure field not to be specified by the user. Finally, remove klp_find_verify_func_addr as it can be replaced by klp_find_object_symbol directly. Signed-off-by: Chris J Arges --- include/linux/livepatch.h | 20 ++++++++------- kernel/livepatch/core.c | 65 ++++++++++++++++++++--------------------------- 2 files changed, 38 insertions(+), 47 deletions(-) diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index 31db7a0..3d18dff 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 @@ -47,17 +48,18 @@ struct klp_func { /* external */ 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 6e53441..479d75e 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, @@ -159,36 +154,46 @@ static int klp_find_callback(void *data, const char *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. + * Increment and assign the address. Return 1 when the desired symbol + * position is found or the search for a unique symbol fails. */ args->addr = addr; args->count++; + if (((args->pos > 0) && (args->count == args->pos)) || + ((args->pos == 0) && (args->count > 1))) + return 1; return 0; } static int klp_find_object_symbol(const char *objname, const char *name, - unsigned long *addr) + unsigned long *addr, unsigned long sympos) { 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 +241,6 @@ 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). @@ -277,7 +261,7 @@ 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); + return klp_find_object_symbol(pmod->name, name, addr, 0); } static int klp_write_object_relocations(struct module *pmod, @@ -307,7 +291,7 @@ static int klp_write_object_relocations(struct module *pmod, else ret = klp_find_object_symbol(obj->mod->name, reloc->name, - &reloc->val); + &reloc->val, 0); if (ret) return ret; } @@ -749,8 +733,13 @@ static int klp_init_object_loaded(struct klp_patch *patch, return ret; } + /* + * Verify the symbol, find old_addr, and write it to the structure. + */ 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_addr, + func->old_sympos); if (ret) return ret; } -- 1.9.1