From patchwork Thu Mar 21 20:01:19 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yonghong Song X-Patchwork-Id: 13599327 X-Patchwork-Delegate: bpf@iogearbox.net Received: from 69-171-232-181.mail-mxout.facebook.com (69-171-232-181.mail-mxout.facebook.com [69.171.232.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3A06F13443B for ; Thu, 21 Mar 2024 20:01:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=69.171.232.181 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711051292; cv=none; b=MW3Z/k4Hrac9peR1Eoxb07mVRewDpz9uUKXFHD3XJeJFL2J11YsIR62k3xC4x1mKsuFpFZeCYo2MYP7YqCMF89Lm/QaBkd6WHiZuKdisFPCdnzsXqNqdAGSd3ABofhTwT3Yw45uBcGLgGmmjTry1Vs/xqhCejHPjhPNVCh+OslI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711051292; c=relaxed/simple; bh=I8cHHkO582AlMXZEe/J+OllEfpdNGNHr16UWvH57zzk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=EM4SmoELvFykJFQZYp2Ada79vWOZGiboxXNo1+HGGxsEatA2VzMKJ3YL9EJZmbhR2DvYN3iNOxVDO1S1ySZn+eTNJXpu+r8cn6OeyY0NgjA3zLDoonqzePJsTOH8m11TDsrxK3Lff7gQFnLXqhcaLm+AApmLvnBis6oUvA6YEGg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev; spf=fail smtp.mailfrom=linux.dev; arc=none smtp.client-ip=69.171.232.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=linux.dev Received: by devbig309.ftw3.facebook.com (Postfix, from userid 128203) id 2A4852219097; Thu, 21 Mar 2024 13:01:19 -0700 (PDT) From: Yonghong Song To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , kernel-team@fb.com, Martin KaFai Lau Subject: [PATCH bpf-next v2 4/5] selftests/bpf: Fix kprobe_multi_bench_attach test failure with LTO kernel Date: Thu, 21 Mar 2024 13:01:19 -0700 Message-ID: <20240321200119.2220027-1-yonghong.song@linux.dev> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240321200058.2218328-1-yonghong.song@linux.dev> References: <20240321200058.2218328-1-yonghong.song@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net In my locally build clang LTO kernel (enabling CONFIG_LTO and CONFIG_LTO_CLANG_THIN), kprobe_multi_bench_attach/kernel subtest failed like: test_kprobe_multi_bench_attach:PASS:get_syms 0 nsec test_kprobe_multi_bench_attach:PASS:kprobe_multi_empty__open_and_load 0 nsec libbpf: prog 'test_kprobe_empty': failed to attach: No such process test_kprobe_multi_bench_attach:FAIL:bpf_program__attach_kprobe_multi_opts unexpected error: -3 #117/1 kprobe_multi_bench_attach/kernel:FAIL There are multiple symbols in /sys/kernel/debug/tracing/available_filter_functions are renamed in /proc/kallsyms due to cross file inlining. One example is for static function __access_remote_vm in mm/memory.c. In a non-LTO kernel, we have the following call stack: ptrace_access_vm (global, kernel/ptrace.c) access_remote_vm (global, mm/memory.c) __access_remote_vm (static, mm/memory.c) With LTO kernel, it is possible that access_remote_vm() is inlined by ptrace_access_vm(). So we end up with the following call stack: ptrace_access_vm (global, kernel/ptrace.c) __access_remote_vm (static, mm/memory.c) The compiler renames __access_remote_vm to __access_remote_vm.llvm. to prevent potential name collision. The kernel bpf_kprobe_multi_link_attach() and ftrace_lookup_symbols() try to find addresses based on /proc/kallsyms, hence the current test failed with LTO kenrel. This patch removed __access_remote_vm and other similar functions from kprobe_multi_attach by checking if the symbol like __access_remote_vm does not exist in kallsyms with LTO kernel. The test succeeded after this change: #117/1 kprobe_multi_bench_attach/kernel:OK Signed-off-by: Yonghong Song Acked-by: Jiri Olsa --- .../selftests/bpf/prog_tests/kprobe_multi_test.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c index 05000810e28e..f6130f4f3d88 100644 --- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c +++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c @@ -345,6 +345,9 @@ static int get_syms(char ***symsp, size_t *cntp, bool kernel) FILE *f; int err = 0; + if (!ASSERT_OK(load_kallsyms(), "load_kallsyms")) + return -EINVAL; + /* * The available_filter_functions contains many duplicates, * but other than that all symbols are usable in kprobe multi @@ -393,6 +396,15 @@ static int get_syms(char ***symsp, size_t *cntp, bool kernel) if (!strncmp(name, "__ftrace_invalid_address__", sizeof("__ftrace_invalid_address__") - 1)) continue; + /* + * In certain cases, e.g., clang lto kernel, the 'name' here + * may be different from the one in /proc/kallsyms due to + * /proc/kallsyms name might be ".llvm." instead + * of "". Exclude these 'name's since they will cause + * later kprobe_multi_attach failure. + */ + if (ksym_get_addr(name) == 0) + continue; err = hashmap__add(map, name, 0); if (err == -EEXIST) {