From patchwork Wed Dec 18 22:52:46 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yonghong Song X-Patchwork-Id: 13914226 X-Patchwork-Delegate: bpf@iogearbox.net Received: from 69-171-232-180.mail-mxout.facebook.com (69-171-232-180.mail-mxout.facebook.com [69.171.232.180]) (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 CEE3F1BDC3 for ; Wed, 18 Dec 2024 22:52:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=69.171.232.180 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734562385; cv=none; b=epbcCrkCwRbrcTaZ/UjAwolYWaPRTNfN26uTESk9P2/3HCP+QEZkwGH/yFA+uplcFzqsgEwS5oHxz4BvmYl1fHZcSfglZTcAkgYZdl+9bXl8SI3+M+oP8xvqEUWQlUhA09kgxfCS39RuQRDRzemrsHdfSsUVoGbfPRRJjx7BDEg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734562385; c=relaxed/simple; bh=CtQQ/MyIgXV859VB3hLsJHAElLDX6UHrPtcmvjMcMSo=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=EVp7tjdTF/+lsokQXOBdj79gOZj7+k+GniIlYJENOoWUnychW0jBHEki5fY6tizmUNdh5c5aW1j+PI03TGe+6Tx4Y39WaEiYJB4kIGcmtuouutW7XtbCv9tlzmnRInDkZ+1KU7m6DRoc2kR9Br0rfIefM003d0M709VwviReT24= 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=69.171.232.180 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 276B6C2A69C6; Wed, 18 Dec 2024 14:52:46 -0800 (PST) From: Yonghong Song To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , kernel-team@fb.com, Martin KaFai Lau , Jordan Rome Subject: [PATCH bpf-next 1/2] libbpf: Add unique_match option for multi kprobe Date: Wed, 18 Dec 2024 14:52:46 -0800 Message-ID: <20241218225246.3170300-1-yonghong.song@linux.dev> X-Mailer: git-send-email 2.43.5 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 Jordan reported an issue in Meta production environment where func try_to_wake_up() is renamed to try_to_wake_up.llvm.() by clang compiler at lto mode. The original 'kprobe/try_to_wake_up' does not work any more since try_to_wake_up() does not match the actual func name in /proc/kallsyms. There are a couple of ways to resolve this issue. For example, in attach_kprobe(), we could do lookup in /proc/kallsyms so try_to_wake_up() can be replaced by try_to_wake_up.llvm.(). Or we can force users to use bpf_program__attach_kprobe() where they need to lookup /proc/kallsyms to find out try_to_wake_up.llvm.(). But these two approaches requires extra work by either libbpf or user. Luckily, suggested by Andrii, multi kprobe already supports wildcard ('*') for symbol matching. In the above example, 'try_to_wake_up*' can match to try_to_wake_up() or try_to_wake_up.llvm.() and this allows bpf prog works for different kernels as some kernels may have try_to_wake_up() and some others may have try_to_wake_up.llvm.(). The original intention is to kprobe try_to_wake_up() only, so an optional field unique_match is added to struct bpf_kprobe_multi_opts. If the field is set to true, the number of matched functions must be one. Otherwise, the attachment will fail. In the above case, multi kprobe with 'try_to_wake_up*' and unique_match preserves user functionality. Reported-by: Jordan Rome Suggested-by: Andrii Nakryiko Signed-off-by: Yonghong Song --- tools/lib/bpf/libbpf.c | 10 +++++++++- tools/lib/bpf/libbpf.h | 4 +++- 2 files changed, 12 insertions(+), 2 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 66173ddb5a2d..649c6e92972a 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -11522,7 +11522,7 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog, struct bpf_link *link = NULL; const unsigned long *addrs; int err, link_fd, prog_fd; - bool retprobe, session; + bool retprobe, session, unique_match; const __u64 *cookies; const char **syms; size_t cnt; @@ -11558,6 +11558,14 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog, err = libbpf_available_kallsyms_parse(&res); if (err) goto error; + + unique_match = OPTS_GET(opts, unique_match, false); + if (unique_match && res.cnt != 1) { + pr_warn("prog '%s': failed to find unique match: cnt %lu\n", + prog->name, res.cnt); + return libbpf_err_ptr(-EINVAL); + } + addrs = res.addrs; cnt = res.cnt; } diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index d45807103565..3020ee45303a 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -552,10 +552,12 @@ struct bpf_kprobe_multi_opts { bool retprobe; /* create session kprobes */ bool session; + /* enforce unique match */ + bool unique_match; size_t :0; }; -#define bpf_kprobe_multi_opts__last_field session +#define bpf_kprobe_multi_opts__last_field unique_match LIBBPF_API struct bpf_link * bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,