From patchwork Tue Aug 13 19:49:06 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Sam James X-Patchwork-Id: 13762442 X-Patchwork-Delegate: bpf@iogearbox.net Received: from smtp.gentoo.org (woodpecker.gentoo.org [140.211.166.183]) (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 18C961C287; Tue, 13 Aug 2024 19:49:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=140.211.166.183 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723578597; cv=none; b=hb29Vxo3ihUD2J3Xneko1rPBCQ1VdILwlVSQfsLZzvinLfVi74X2efQIF35t7pZgk7+UBksx68EukksNgBQ8GXPNFix52UjuslkFIN2toD99DvqegC/Dp+pRQZpGj1oxKD/p+4x11H7ZxG8euWcbMSjf2yplF+xOshXlI4jWWIo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723578597; c=relaxed/simple; bh=PLrFcNU7ckpOpLk686/xgxDVMbFxUHcGvJjGQOjsC2w=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=msZ6Q09j/3cy81DfL/pT4cQykR+NMpITnrQymWs842U0bXWcc1DBpdzlQrv5RbDxgFS4vX6GU9BaqunAvOjnuYQMx1aTaTUTRQ9Izz7YP3BanadDA2nsleKCMmeYavPX8whciYYwKAO/pztSSsMEnwKgO8vrsvOCp26Gn+hMaqM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gentoo.org; spf=pass smtp.mailfrom=gentoo.org; arc=none smtp.client-ip=140.211.166.183 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gentoo.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gentoo.org From: Sam James To: Andrii Nakryiko , Eduard Zingerman , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa Cc: "Jose E . Marchesi" , Andrew Pinski , =?utf-8?b?S2FjcGVyIFPFgm9tacWE?= =?utf-8?b?c2tp?= , =?utf-8?q?Arsen_Arsenovi?= =?utf-8?q?=C4=87?= , Sam James , bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v4] libbpf: workaround -Wmaybe-uninitialized false positive Date: Tue, 13 Aug 2024 20:49:06 +0100 Message-ID: <14ec488a1cac02794c2fa2b83ae0cef1bce2cb36.1723578546.git.sam@gentoo.org> X-Mailer: git-send-email 2.45.2 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 `elf_close`, we get this with GCC 15 -O3 (at least): ``` In function ‘elf_close’, inlined from ‘elf_close’ at elf.c:53:6, inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2: elf.c:57:9: warning: ‘elf_fd.elf’ may be used uninitialized [-Wmaybe-uninitialized] 57 | elf_end(elf_fd->elf); | ^~~~~~~~~~~~~~~~~~~~ elf.c: In function ‘elf_find_func_offset_from_file’: elf.c:377:23: note: ‘elf_fd.elf’ was declared here 377 | struct elf_fd elf_fd; | ^~~~~~ In function ‘elf_close’, inlined from ‘elf_close’ at elf.c:53:6, inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2: elf.c:58:9: warning: ‘elf_fd.fd’ may be used uninitialized [-Wmaybe-uninitialized] 58 | close(elf_fd->fd); | ^~~~~~~~~~~~~~~~~ elf.c: In function ‘elf_find_func_offset_from_file’: elf.c:377:23: note: ‘elf_fd.fd’ was declared here 377 | struct elf_fd elf_fd; | ^~~~~~ ``` In reality, our use is fine, it's just that GCC doesn't model errno here (see linked GCC bug). Suppress -Wmaybe-uninitialized accordingly by initializing elf_fd.fd to -1 and elf_fd.elf to NULL. I've done this in two other functions as well given it could easily occur there too (same access/use pattern). Link: https://gcc.gnu.org/PR114952 Signed-off-by: Sam James --- v4: Initialize elf and fd members in elf_open to avoid meddling with callers. tools/lib/bpf/elf.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c index c92e02394159e..b5ab1cb13e5ea 100644 --- a/tools/lib/bpf/elf.c +++ b/tools/lib/bpf/elf.c @@ -28,6 +28,9 @@ int elf_open(const char *binary_path, struct elf_fd *elf_fd) int fd, ret; Elf *elf; + elf_fd->elf = NULL; + elf_fd->fd = -1; + if (elf_version(EV_CURRENT) == EV_NONE) { pr_warn("elf: failed to init libelf for %s\n", binary_path); return -LIBBPF_ERRNO__LIBELF;