From mboxrd@z Thu Jan 1 00:00:00 1970 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 2AD26C433FE for ; Mon, 31 Jan 2022 10:34:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1358252AbiAaKeY (ORCPT ); Mon, 31 Jan 2022 05:34:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37050 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1358240AbiAaKeW (ORCPT ); Mon, 31 Jan 2022 05:34:22 -0500 Received: from mail-ej1-x649.google.com (mail-ej1-x649.google.com [IPv6:2a00:1450:4864:20::649]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1D85CC061714 for ; Mon, 31 Jan 2022 02:34:22 -0800 (PST) Received: by mail-ej1-x649.google.com with SMTP id mp5-20020a1709071b0500b0069f2ba47b20so4756679ejc.19 for ; Mon, 31 Jan 2022 02:34:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=/V9lGjda+sqhZSBIJFUSQvnNkRukniydQDjwMIcq1AU=; b=HaftrDy8RRZtNqvnRpslsmbCqV9LiDFdIpZqwMNom/SjfzRRxA6W+AJHeY6gS2Zo3T iBdb9aP19dtekWTVyG+Z26xhKT8yJwf7LQ4sX3CMKmnQX/ViGS/wXhqE2YBaLz15N37y bg9wPGARvypQGeT4E3W0tJojbhLNpDaCaQ3hDEqq4AYnwHGuaIpXtemH/yFRIwvFgda3 xxW9JhdJqyZTIjc9ZhwrCd5tCcSLzH7fQvStpRThe6rgOFOxk72d30vdOTNjsZ4V9NiI Jv9m5QgRAhBu+5T8HSLDFW2BTD0MxoShbuhAoXjL1V062FUPlQ0HnuNbPbWrO0w080Sp MElg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=/V9lGjda+sqhZSBIJFUSQvnNkRukniydQDjwMIcq1AU=; b=oXt+uMu8yvV77k8Mg1zXmjmS/zEopKj0bZU+L1C7znMeyT+h5RFHotXkI+uNbnIaSK Zb0UBVQrqMntne+O5ajxhTscOAZFE/yTpEV9VqWg9FAW8paH5DwpHVgkI5IfG5ZI37g9 lIHCmeVVihdQVcIxCoQsfywm9Ld9ounfvqOehT0tZLKIMprVU7lcVYdiILpQDqQvivw6 hT0ZNbXLCQBUYzRocgQnZyx7lK2BRDkG9rdZr+MHoKn9/kznDhehjrPSUjLAWQRtmNj7 0SvmWDgF0IpnfgXzYRaUE7Rc3XL9Yigu4vYmJcF3BSZjjFzX0Exs3x4BBw/uSx/42UuS KTHg== X-Gm-Message-State: AOAM532m4GVFQryw5gquQ0MhCS9uVlvcu98K0VYt4fsmtHm2tCFk0On0 gDYAZDpnIpx3Q4xbHhnFJ6xxwVGNiw== X-Google-Smtp-Source: ABdhPJwRojx1P2rs4U2N3TIrdML9KdiEdQ8wjzMzd5TadS0x2DyuDnvNCCtu1KgU/wviVFpEDMSC7iy2pQ== X-Received: from elver.muc.corp.google.com ([2a00:79e0:15:13:76:dcf3:95f9:db8b]) (user=elver job=sendgmr) by 2002:a17:907:d28:: with SMTP id gn40mr12058531ejc.750.1643625260505; Mon, 31 Jan 2022 02:34:20 -0800 (PST) Date: Mon, 31 Jan 2022 11:34:07 +0100 In-Reply-To: <20220131103407.1971678-1-elver@google.com> Message-Id: <20220131103407.1971678-3-elver@google.com> Mime-Version: 1.0 References: <20220131103407.1971678-1-elver@google.com> X-Mailer: git-send-email 2.35.0.rc2.247.g8bbb082509-goog Subject: [PATCH 3/3] perf: uapi: Document perf_event_attr::sig_data truncation on 32 bit architectures From: Marco Elver To: elver@google.com, Peter Zijlstra Cc: Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Dmitry Vyukov , linux-perf-users@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Due to the alignment requirements of siginfo_t, as described in 3ddb3fd8cdb0 ("signal, perf: Fix siginfo_t by avoiding u64 on 32-bit architectures"), siginfo_t::si_perf_data is limited to an unsigned long. However, perf_event_attr::sig_data is an u64, to avoid having to deal with compat conversions. Due to being an u64, it may not immediately be clear to users that sig_data is truncated on 32 bit architectures. Add a comment to explicitly point this out, and hopefully help some users save time by not having to deduce themselves what's happening. Reported-by: Dmitry Vyukov Signed-off-by: Marco Elver --- include/uapi/linux/perf_event.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h index 1b65042ab1db..82858b697c05 100644 --- a/include/uapi/linux/perf_event.h +++ b/include/uapi/linux/perf_event.h @@ -465,6 +465,8 @@ struct perf_event_attr { /* * User provided data if sigtrap=1, passed back to user via * siginfo_t::si_perf_data, e.g. to permit user to identify the event. + * Note, siginfo_t::si_perf_data is long-sized, and sig_data will be + * truncated accordingly on 32 bit architectures. */ __u64 sig_data; }; -- 2.35.0.rc2.247.g8bbb082509-goog