From nobody Wed Apr 15 04:15:15 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 40675C04A68 for ; Tue, 26 Jul 2022 22:09:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232198AbiGZWJg (ORCPT ); Tue, 26 Jul 2022 18:09:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57906 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229550AbiGZWJe (ORCPT ); Tue, 26 Jul 2022 18:09:34 -0400 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BA43C357F8 for ; Tue, 26 Jul 2022 15:09:33 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-31e89d6bea7so118695347b3.10 for ; Tue, 26 Jul 2022 15:09:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc; bh=61ygh8X7OQQWmmobWyLHSxPrOS1I/DRVXUaMo8TVVqI=; b=gqHT0I163ggdkBpzgekg1P3z1Owbv0KgTUlCBNz6KTUPjUVzEdgWV/78MN7KEJFvAS u9mJA1+KTwKXz77J7ct+7SaLrsrmc5dfV++JY+ccBSXog/u2AaPWhX81vEXSeS4ET1Xx fywi68p20oM9tVx8oXHty5YZb/f3QFk46Wo8XHZYEK4EsQDZICnkXEJZEcne12OLURNa weaRnuPpahTuDYvUJ/oEWVadZmyU5GkfPp97wiamLVknZWcYOz1u5C1d3OudRN9je7qq /wEFwfYtsR5qtrkz19P1Vbun8MshuGYNATcqb9r+4tOOz1ef0oyqQLziDdImctFPXVyF 2vKA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=61ygh8X7OQQWmmobWyLHSxPrOS1I/DRVXUaMo8TVVqI=; b=G1rOJMK5tbpJbzX6Y/jVoKrclAAzGfJXM7iq35TBZt0euQxeE+LzawmKrUbdovTNwL vOP3eIk/j+On4TCcyQbiiZk496fIPmGOehHrldBnE/AhVmRXj2UfZYa0DPANL+n5WUe7 FIIsg+QTc4pGl0ZPSMQkQsMGFivMfTwehiPlOpOnwXYq2OAXWpAVUnfsUvVfyOzBXrjn a34Gf1dpVnMZc4yseY5o1basKUQsQ/EOTCg0/ql68ALwtiLNpPWlbvdhNMGqazT13Bd/ pQIpTifBg32koyIVnAt1PPcztfTQJ0Q+hxc1MwCW3sVZfapeEcT11GIlsy9YHFIz3mbf Lj6A== X-Gm-Message-State: AJIora97DTS9MalP9iKEtWUOz8944QraFP0JYJqkrbENDrR2oZB4VsSc ZFNTkwS10gEkknv/yisj/nelbxSa4zyz X-Google-Smtp-Source: AGRyM1tnePqm3Dn8R4WJBqDYeFadFCYz69lsbiCMtw+mCfRf1FbWN2PvCm2fn7EpRTb5fa0x2HF9e6LdpnZR X-Received: from irogers.svl.corp.google.com ([2620:15c:2d4:203:256:6b1d:50b:fa5a]) (user=irogers job=sendgmr) by 2002:a81:8d08:0:b0:317:a4cd:d65d with SMTP id d8-20020a818d08000000b00317a4cdd65dmr16308668ywg.329.1658873373047; Tue, 26 Jul 2022 15:09:33 -0700 (PDT) Date: Tue, 26 Jul 2022 15:09:21 -0700 Message-Id: <20220726220921.2567761-1-irogers@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.37.1.359.gd136c6c3e2-goog Subject: [PATCH] perf bpf: Remove undefined behavior from bpf_perf_object__next From: Ian Rogers To: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Nathan Chancellor , Nick Desaulniers , Tom Rix , Andrii Nakryiko , Christy Lee , Alexei Starovoitov , Miaoqian Lin , Ian Rogers , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, llvm@lists.linux.dev Cc: Stephane Eranian Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" bpf_perf_object__next folded the last element in the list test with the empty list test. However, this meant that offsets were computed against null and that a struct list_head was compared against a struct bpf_perf_object. Working around this with clang's undefined behavior sanitizer required -fno-sanitize=3Dnull and -fno-sanitize=3Dobject-size. Remove the undefined behavior by using the regular Linux list APIs and handling the starting case separately from the end testing case. Looking at uses like bpf_perf_object__for_each, as the constant NULL or non-NULL argument can be constant propagated the code is no less efficient. Signed-off-by: Ian Rogers --- tools/perf/util/bpf-loader.c | 18 +++++++----------- 1 file changed, 7 insertions(+), 11 deletions(-) diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c index f8ad581ea247..cdd6463a5b68 100644 --- a/tools/perf/util/bpf-loader.c +++ b/tools/perf/util/bpf-loader.c @@ -63,20 +63,16 @@ static struct hashmap *bpf_map_hash; static struct bpf_perf_object * bpf_perf_object__next(struct bpf_perf_object *prev) { - struct bpf_perf_object *next; - - if (!prev) - next =3D list_first_entry(&bpf_objects_list, - struct bpf_perf_object, - list); - else - next =3D list_next_entry(prev, list); + if (!prev) { + if (list_empty(&bpf_objects_list)) + return NULL; =20 - /* Empty list is noticed here so don't need checking on entry. */ - if (&next->list =3D=3D &bpf_objects_list) + return list_first_entry(&bpf_objects_list, struct bpf_perf_object, list); + } + if (list_is_last(&prev->list, &bpf_objects_list)) return NULL; =20 - return next; + return list_next_entry(prev, list); } =20 #define bpf_perf_object__for_each(perf_obj, tmp) \ --=20 2.37.1.359.gd136c6c3e2-goog