From mboxrd@z Thu Jan 1 00:00:00 1970 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 C6F2A22F0D for ; Sat, 2 Mar 2024 16:50:47 +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=1709398249; cv=none; b=RHAD4nczh6UUF97d5Tyv0WAzQsIlhHVM8gzvx9gOKWGanukzBPuc10EXEARwb2kvjygJzSFxNrhDsagpdKXCnred1Nplen6XDgAfVPmk0qpP5sTWgi4kQ+QT+a+R8a0mU2QBbrI8TVXSZtda6mbfFqU6fCOVUhQOXyYbiu5Q2wY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709398249; c=relaxed/simple; bh=BhYRMw/JbHPDeiLEkih1Uj7FeJ6A2IBeH3+doHNoIwU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dsxuSJ58ykRqwZwr3YV3L8D+993d1AmKaNR8MOTAiNj4JA+1YeEv0mrmLVsUQK/vICxdbZoulljJx2/FFeO04RSMUbnd6C+odo0Y+hFPs5nBhUBRUiWBHMffINaOzRLVO+DpBsuGQWtDzqAyfqbyDsg2Yimjaz1ajbN8FCVw0Y0= 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 4D3D711F1241; Sat, 2 Mar 2024 08:50:38 -0800 (PST) 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 4/4] selftests/bpf: Fix possible kprobe_multi_bench_attach test failure with LTO kernel Date: Sat, 2 Mar 2024 08:50:38 -0800 Message-ID: <20240302165038.1628632-1-yonghong.song@linux.dev> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240302165017.1627295-1-yonghong.song@linux.dev> References: <20240302165017.1627295-1-yonghong.song@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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_op= ts unexpected error: -3 #114/1 kprobe_multi_bench_attach/kernel:FAIL There are multiple symbols in /sys/kernel/debug/tracing/available_filter_= functions are renamed in 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. 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: #114/1 kprobe_multi_bench_attach/kernel:OK Signed-off-by: Yonghong Song --- tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c | 7 +++++++ 1 file changed, 7 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..2aad5f9cdb84 100644 --- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c +++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c @@ -341,10 +341,15 @@ static int get_syms(char ***symsp, size_t *cntp, bo= ol kernel) size_t cap =3D 0, cnt =3D 0, i; char *name =3D NULL, **syms =3D NULL; struct hashmap *map; + bool lto_kernel; char buf[256]; FILE *f; int err =3D 0; =20 + lto_kernel =3D kernel && check_lto_kernel() =3D=3D 1; + if (lto_kernel && !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 +398,8 @@ static int get_syms(char ***symsp, size_t *cntp, bool= kernel) if (!strncmp(name, "__ftrace_invalid_address__", sizeof("__ftrace_invalid_address__") - 1)) continue; + if (lto_kernel && ksym_get_addr(name) =3D=3D 0) + continue; =20 err =3D hashmap__add(map, name, 0); if (err =3D=3D -EEXIST) { --=20 2.43.0