From patchwork Wed Aug 7 22:05:13 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Song Liu X-Patchwork-Id: 13756809 X-Patchwork-Delegate: mhiramat@kernel.org Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A20DF146599; Wed, 7 Aug 2024 22:06:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723068405; cv=none; b=CUiqDHP8nwW8oXQCPDH3dnO5dlZzNIzV8UoZlNsvs7wOOP/aKGmjJ9Q3WTOD3A2vKGW4iawllpIKkSk/vptbMgkZw6/vT8784FINcaA/FzxvakTGrlKmbrqJNmT+iRdpSZcpBUWD+45+KIpPgovrKdu3EAHp7zVMsIffuhZJRWo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723068405; c=relaxed/simple; bh=mo5cCI52YxBS4frh3l+KA2nX1q9ZcrMkE2ErnP/Qf8A=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PVQc+8cpWE1vexu5+9oNY6LKS1xOV50/MfoFgWJWYXZBZrHYzrIMZ0fjtm6VKfw8B0P9GXmVCgGPkXGWmfenJddB7ZGuLNlD+pZRtaiybT5iS3cdH3Q4WbXJetNO6VL1fegTnswaklpC19wM5DX/V3EhmFEW/aQ3iI41HHTsIWk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=anquUQfp; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="anquUQfp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B6E2DC32782; Wed, 7 Aug 2024 22:06:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1723068405; bh=mo5cCI52YxBS4frh3l+KA2nX1q9ZcrMkE2ErnP/Qf8A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=anquUQfp0kf6tx02UCWUPtvNh6GCGXtww2I9YTVz824oDuszPrePU2Ji49Ubulszx 3tx66uabjRqSP0u4NFANSYV4WE2EoVVy7pLGr63IC+ZdnXygWavMvmcqgSygvwyCDp so2pPGsXW0vEcBE0N6iEM+YXWPy38u+DcwqHJMikJhN1SsluzTSdITk+uXXtuylF4d xHRv4mrtm7AfPSFwiMBpmNbWA75O7EqYlZR3TVhpcsL7cTKxlPkPwtce4KoEJciy0D eExbV41HlFt7fA7JPJt1EOXYhMLTDXXquA9QxC6Dbfn4YX/goeTOwjmArqRU1K+zBQ s7pNICnJ6h5Tg== From: Song Liu To: live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: jpoimboe@kernel.org, jikos@kernel.org, mbenes@suse.cz, pmladek@suse.com, joe.lawrence@redhat.com, nathan@kernel.org, morbo@google.com, justinstitt@google.com, mcgrof@kernel.org, thunder.leizhen@huawei.com, kees@kernel.org, kernel-team@meta.com, song@kernel.org, mmaurer@google.com, samitolvanen@google.com, mhiramat@kernel.org, rostedt@goodmis.org Subject: [PATCH v3 2/2] kallsyms: Match symbols exactly with CONFIG_LTO_CLANG Date: Wed, 7 Aug 2024 15:05:13 -0700 Message-ID: <20240807220513.3100483-3-song@kernel.org> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20240807220513.3100483-1-song@kernel.org> References: <20240807220513.3100483-1-song@kernel.org> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 With CONFIG_LTO_CLANG=y, the compiler may add .llvm. suffix to function names to avoid duplication. APIs like kallsyms_lookup_name() and kallsyms_on_each_match_symbol() tries to match these symbol names without the .llvm. suffix, e.g., match "c_stop" with symbol c_stop.llvm.17132674095431275852. This turned out to be problematic for use cases that require exact match, for example, livepatch. Fix this by making the APIs to match symbols exactly. Also cleanup kallsyms_selftests accordingly. Signed-off-by: Song Liu --- kernel/kallsyms.c | 55 +++++--------------------------------- kernel/kallsyms_selftest.c | 22 +-------------- 2 files changed, 7 insertions(+), 70 deletions(-) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index fb2c77368d18..a9a0ca605d4a 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -160,38 +160,6 @@ unsigned long kallsyms_sym_address(int idx) return kallsyms_relative_base - 1 - kallsyms_offsets[idx]; } -static void cleanup_symbol_name(char *s) -{ - char *res; - - if (!IS_ENABLED(CONFIG_LTO_CLANG)) - return; - - /* - * LLVM appends various suffixes for local functions and variables that - * must be promoted to global scope as part of LTO. This can break - * hooking of static functions with kprobes. '.' is not a valid - * character in an identifier in C. Suffixes only in LLVM LTO observed: - * - foo.llvm.[0-9a-f]+ - */ - res = strstr(s, ".llvm."); - if (res) - *res = '\0'; - - return; -} - -static int compare_symbol_name(const char *name, char *namebuf) -{ - /* The kallsyms_seqs_of_names is sorted based on names after - * cleanup_symbol_name() (see scripts/kallsyms.c) if clang lto is enabled. - * To ensure correct bisection in kallsyms_lookup_names(), do - * cleanup_symbol_name(namebuf) before comparing name and namebuf. - */ - cleanup_symbol_name(namebuf); - return strcmp(name, namebuf); -} - static unsigned int get_symbol_seq(int index) { unsigned int i, seq = 0; @@ -219,7 +187,7 @@ static int kallsyms_lookup_names(const char *name, seq = get_symbol_seq(mid); off = get_symbol_offset(seq); kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf)); - ret = compare_symbol_name(name, namebuf); + ret = strcmp(name, namebuf); if (ret > 0) low = mid + 1; else if (ret < 0) @@ -236,7 +204,7 @@ static int kallsyms_lookup_names(const char *name, seq = get_symbol_seq(low - 1); off = get_symbol_offset(seq); kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf)); - if (compare_symbol_name(name, namebuf)) + if (strcmp(name, namebuf)) break; low--; } @@ -248,7 +216,7 @@ static int kallsyms_lookup_names(const char *name, seq = get_symbol_seq(high + 1); off = get_symbol_offset(seq); kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf)); - if (compare_symbol_name(name, namebuf)) + if (strcmp(name, namebuf)) break; high++; } @@ -407,8 +375,7 @@ static int kallsyms_lookup_buildid(unsigned long addr, if (modbuildid) *modbuildid = NULL; - ret = strlen(namebuf); - goto found; + return strlen(namebuf); } /* See if it's in a module or a BPF JITed image. */ @@ -422,8 +389,6 @@ static int kallsyms_lookup_buildid(unsigned long addr, ret = ftrace_mod_address_lookup(addr, symbolsize, offset, modname, namebuf); -found: - cleanup_symbol_name(namebuf); return ret; } @@ -450,8 +415,6 @@ const char *kallsyms_lookup(unsigned long addr, int lookup_symbol_name(unsigned long addr, char *symname) { - int res; - symname[0] = '\0'; symname[KSYM_NAME_LEN - 1] = '\0'; @@ -462,16 +425,10 @@ int lookup_symbol_name(unsigned long addr, char *symname) /* Grab name */ kallsyms_expand_symbol(get_symbol_offset(pos), symname, KSYM_NAME_LEN); - goto found; + return 0; } /* See if it's in a module. */ - res = lookup_module_symbol_name(addr, symname); - if (res) - return res; - -found: - cleanup_symbol_name(symname); - return 0; + return lookup_module_symbol_name(addr, symname); } /* Look up a kernel symbol and return it in a text buffer. */ diff --git a/kernel/kallsyms_selftest.c b/kernel/kallsyms_selftest.c index 2f84896a7bcb..873f7c445488 100644 --- a/kernel/kallsyms_selftest.c +++ b/kernel/kallsyms_selftest.c @@ -187,31 +187,11 @@ static void test_perf_kallsyms_lookup_name(void) stat.min, stat.max, div_u64(stat.sum, stat.real_cnt)); } -static bool match_cleanup_name(const char *s, const char *name) -{ - char *p; - int len; - - if (!IS_ENABLED(CONFIG_LTO_CLANG)) - return false; - - p = strstr(s, ".llvm."); - if (!p) - return false; - - len = strlen(name); - if (p - s != len) - return false; - - return !strncmp(s, name, len); -} - static int find_symbol(void *data, const char *name, unsigned long addr) { struct test_stat *stat = (struct test_stat *)data; - if (strcmp(name, stat->name) == 0 || - (!stat->perf && match_cleanup_name(name, stat->name))) { + if (!strcmp(name, stat->name)) { stat->real_cnt++; stat->addr = addr;