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 X-Spam-Level: X-Spam-Status: No, score=-8.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B9FCACA9EA0 for ; Tue, 22 Oct 2019 05:10:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8149C20B7C for ; Tue, 22 Oct 2019 05:10:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="d18epoJO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731136AbfJVFKd (ORCPT ); Tue, 22 Oct 2019 01:10:33 -0400 Received: from mail-qt1-f196.google.com ([209.85.160.196]:33790 "EHLO mail-qt1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725907AbfJVFKd (ORCPT ); Tue, 22 Oct 2019 01:10:33 -0400 Received: by mail-qt1-f196.google.com with SMTP id r5so24991998qtd.0 for ; Mon, 21 Oct 2019 22:10:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=+w/qzEw27aMbdNSzTHsuyi7AE3I1PGTPr3i5czPeWmY=; b=d18epoJOJ0/pv+lNYQywjIqfTmBcEV4Xe9ZM1R+1nkVFJ0k39xTxxsxkYvdimN1u8D wGdPIPRG6vg8TmeWT28uyJqs9P4kJKkzWrm9Lf1bhLFqtspGApUJsUHOeu/bHSxbKoQR FsB3F8RutqugqF0xleQHdXDJYvlYqjUVNuUIEA6BHdXkFFHCUpqfPeoFnWDOMF1UDdRu o2EgcCB1dGjn3jgIN33ra19bKI3mtq52W9jdEdB1pK1aTvcS+itAW8EmBTlQIKJG4KA2 mRZWNZi+hDcDLcQPhJRVPCCVUtetWXz512HyX1AIo4968BWHUD5H0LIR2F6EkM7c4w5c WNeA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=+w/qzEw27aMbdNSzTHsuyi7AE3I1PGTPr3i5czPeWmY=; b=th7NcgVLphAO9zMxLP5LzTDAN2BlCr6setVVDYEpKzx7M7t7OUAUuImNNxgabSqaKl eEcSEh0zzuCnOG2gIuIiAGQa3qNzPhQq8sTaFrOpjGxWr0WsO677hMMZwqplqc4fxJkL z/fuwGaC6YRhFtiiVgAmCfzOi32yI8Mm4W8Iqz18I3X6x2x28OJNiCbVQmyk37cOs5Z8 rRRd15k9moXg/WE5E5JUP5/TLx8sBaYosc+KnQEFySMCVGZ3oxA9DnRRsgvrVdYPpMUy nWUMlbtY3ZXQgq42PweB6/VnOXandxT8ZZS5YPu6NFpbv7eSoSMl78YCEU6Rm1Kux6uQ 8dAA== X-Gm-Message-State: APjAAAUtqeYeMq972YYD8xfqpoCl0LAqCv+qJWyxmGieMF/dHtB/ZC9E ifSfBcntZKv09O3v5IGF0mXXEw== X-Google-Smtp-Source: APXvYqwUVrs5nyGdBFsOdfVGQj0yuFetc/Nm7EOzMo+7I/93O+mEndLG3kY9gALAfx/Mv4QZVHGLfQ== X-Received: by 2002:ac8:28c4:: with SMTP id j4mr1506947qtj.303.1571721031756; Mon, 21 Oct 2019 22:10:31 -0700 (PDT) Received: from leoy-ThinkPad-X240s (li937-157.members.linode.com. [45.56.119.157]) by smtp.gmail.com with ESMTPSA id z70sm5313857qkb.60.2019.10.21.22.10.25 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 21 Oct 2019 22:10:29 -0700 (PDT) Date: Tue, 22 Oct 2019 13:10:20 +0800 From: Leo Yan To: Mathieu Poirier Cc: Arnaldo Carvalho de Melo , Suzuki K Poulose , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Mike Leach , Coresight ML , Peter Zijlstra , Ingo Molnar Subject: Re: [PATCH v3 1/6] perf cs-etm: Fix unsigned variable comparison to zero Message-ID: <20191022051020.GC32731@leoy-ThinkPad-X240s> References: <20191005091614.11635-1-leo.yan@linaro.org> <20191005091614.11635-2-leo.yan@linaro.org> <20191011201606.GC13688@xps15> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191011201606.GC13688@xps15> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mathieu, On Fri, Oct 11, 2019 at 02:16:06PM -0600, Mathieu Poirier wrote: > On Sat, Oct 05, 2019 at 05:16:09PM +0800, Leo Yan wrote: > > If the u64 variable 'offset' is a negative integer, comparison it with > > bigger than zero is always going to be true because it is unsigned. > > Fix this by using s64 type for variable 'offset'. > > > > Signed-off-by: Leo Yan > > --- > > tools/perf/util/cs-etm.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c > > index 4ba0f871f086..4bc2d9709d4f 100644 > > --- a/tools/perf/util/cs-etm.c > > +++ b/tools/perf/util/cs-etm.c > > @@ -940,7 +940,7 @@ u64 cs_etm__last_executed_instr(const struct cs_etm_packet *packet) > > static inline u64 cs_etm__instr_addr(struct cs_etm_queue *etmq, > > u64 trace_chan_id, > > const struct cs_etm_packet *packet, > > - u64 offset) > > + s64 offset) > > In Suzuki's reply there was two choices, 1) move the while(offset > 0) to > while (offset) or change the type of @offset to an s64. Here we know offset > can't be negative because of the > tidq->period_instructions >= etm->instructions_sample_period > > in function cs_etm__sample(). As such I think option #1 is the right way to > deal with this rather than changing the type of the variable. I took sometime to use formulas to prove that 'offset' is possible to be a negative value :) Just paste the updated commit log at here for review: Pi: period_instructions Ie: instrs_executed Io: instrs_over Ip: instructions_sample_period Pi' = Pi + Ie -> New period_instructions equals to the old period_instructions + instrs_executed Io = Pi' - Ip -> period_instructions - instructions_sample_period offset = Ie - Io - 1 = Ie - (Pi' - Ip) -1 = Ie - (Pi + Ie - Ip) -1 = Ip - Pi - 1 In theory, if Ip (instructions_sample_period) is small enough and Pi (period_instructions) is bigger than Ip, then it will lead to the negative value for 'offset'. So let's see below command: perf inject --itrace=i1il128 -i perf.data -o perf.data.new With this command, 'offset' is very easily to be a negative value when handling packets; this is because if use the inject option 'i1', then instructions_sample_period equals to 1; so: offset = 1 - Pi - 1 = -Pi Any Pi bigger than zero leads 'offset' to a negative value. Thanks, Leo Yan > > { > > if (packet->isa == CS_ETM_ISA_T32) { > > u64 addr = packet->start_addr; > > @@ -1372,7 +1372,7 @@ static int cs_etm__sample(struct cs_etm_queue *etmq, > > * sample is reported as though instruction has just been > > * executed, but PC has not advanced to next instruction) > > */ > > - u64 offset = (instrs_executed - instrs_over - 1); > > + s64 offset = (instrs_executed - instrs_over - 1); > > u64 addr = cs_etm__instr_addr(etmq, trace_chan_id, > > tidq->packet, offset); > > > > -- > > 2.17.1 > > 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 X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4724DCA9EA0 for ; Tue, 22 Oct 2019 05:10:37 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 078BA20B7C for ; Tue, 22 Oct 2019 05:10:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="OLH3JFum"; dkim=fail reason="signature verification failed" (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="d18epoJO" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 078BA20B7C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=cj09crPy5qKIJpSiLkoIRXSPk0n92l5AWHvYCFt/Hfk=; b=OLH3JFumnQ2Pbi Ns/1ZmzeMQOKuGjC2ElftKfBU6d5sNFHcHwW6TpnchdFH6NlimZe81SHa+5zYGaEE3dzcH2wAtYHr 2yF/egIIXqh877i3VBsFlihpqUp2ZAQh+vDw/WTn5/zh9zKXdZABYonz7uEwuXmUFZTGjIDsKkiwF LW1z12DmHAxfjwfZmyqOsGJOMfuH/e7/7OEsZi5ShWvjpaimL2PJb+/yfkYYTiEZHLF2bIvt/c0HW 2lsJPUwWr3GnRpVT9ecbaDMN8rEaZ/fZW/NGSJkssey24USv+O5mKBzZmyKIwpzuLAWfzoF4+MM6Q o7ttCET+ZqfP3QxkSICQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iMmRH-0003Vb-Ll; Tue, 22 Oct 2019 05:10:35 +0000 Received: from mail-qt1-x842.google.com ([2607:f8b0:4864:20::842]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iMmRE-0003V5-Nn for linux-arm-kernel@lists.infradead.org; Tue, 22 Oct 2019 05:10:34 +0000 Received: by mail-qt1-x842.google.com with SMTP id e14so5153957qto.1 for ; Mon, 21 Oct 2019 22:10:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=+w/qzEw27aMbdNSzTHsuyi7AE3I1PGTPr3i5czPeWmY=; b=d18epoJOJ0/pv+lNYQywjIqfTmBcEV4Xe9ZM1R+1nkVFJ0k39xTxxsxkYvdimN1u8D wGdPIPRG6vg8TmeWT28uyJqs9P4kJKkzWrm9Lf1bhLFqtspGApUJsUHOeu/bHSxbKoQR FsB3F8RutqugqF0xleQHdXDJYvlYqjUVNuUIEA6BHdXkFFHCUpqfPeoFnWDOMF1UDdRu o2EgcCB1dGjn3jgIN33ra19bKI3mtq52W9jdEdB1pK1aTvcS+itAW8EmBTlQIKJG4KA2 mRZWNZi+hDcDLcQPhJRVPCCVUtetWXz512HyX1AIo4968BWHUD5H0LIR2F6EkM7c4w5c WNeA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=+w/qzEw27aMbdNSzTHsuyi7AE3I1PGTPr3i5czPeWmY=; b=SB1/hkhCtxMw1TqA8nWs3z3fiXGlpzfZ00ko09VWXn8sZPkbLDRmfd44YXXF9PzyIE Js5y+GJAatXZqDJoh9gRFJtzVb2C3e7k+V8axPTeklQxFCGPkbv/H868G2PDcqCSj4GM eNar9TI3OtxFGay0GG6sILLiFYgJaM3/EP0HrMDOiBeqTlcJLjTwAbWwpc0H3H0ncheu HHQkd6HooRysnNJz7HC7jnUsby4i1M71kIEPXusTowPyrhFbfm8wJGhPhadsLLI8SHB5 gdwlYJmuHGtKagS6f+LFIvhP07URDdJaMx8Fqfn9+A8oO8eIkCTKC+YI7faO0CKk4Gvf cOBA== X-Gm-Message-State: APjAAAXveahiEzaAvx14iAfL4tIAUK4H3jwWwF7ur4ko6dPl1mHxL3h1 LjQvK7VZJWubvqiVMQAhIlDP9g== X-Google-Smtp-Source: APXvYqwUVrs5nyGdBFsOdfVGQj0yuFetc/Nm7EOzMo+7I/93O+mEndLG3kY9gALAfx/Mv4QZVHGLfQ== X-Received: by 2002:ac8:28c4:: with SMTP id j4mr1506947qtj.303.1571721031756; Mon, 21 Oct 2019 22:10:31 -0700 (PDT) Received: from leoy-ThinkPad-X240s (li937-157.members.linode.com. [45.56.119.157]) by smtp.gmail.com with ESMTPSA id z70sm5313857qkb.60.2019.10.21.22.10.25 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 21 Oct 2019 22:10:29 -0700 (PDT) Date: Tue, 22 Oct 2019 13:10:20 +0800 From: Leo Yan To: Mathieu Poirier Subject: Re: [PATCH v3 1/6] perf cs-etm: Fix unsigned variable comparison to zero Message-ID: <20191022051020.GC32731@leoy-ThinkPad-X240s> References: <20191005091614.11635-1-leo.yan@linaro.org> <20191005091614.11635-2-leo.yan@linaro.org> <20191011201606.GC13688@xps15> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191011201606.GC13688@xps15> User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191021_221032_778552_168AA57D X-CRM114-Status: GOOD ( 23.40 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Suzuki K Poulose , Alexander Shishkin , Coresight ML , linux-kernel@vger.kernel.org, Arnaldo Carvalho de Melo , Peter Zijlstra , Ingo Molnar , Namhyung Kim , Jiri Olsa , linux-arm-kernel@lists.infradead.org, Mike Leach Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Mathieu, On Fri, Oct 11, 2019 at 02:16:06PM -0600, Mathieu Poirier wrote: > On Sat, Oct 05, 2019 at 05:16:09PM +0800, Leo Yan wrote: > > If the u64 variable 'offset' is a negative integer, comparison it with > > bigger than zero is always going to be true because it is unsigned. > > Fix this by using s64 type for variable 'offset'. > > > > Signed-off-by: Leo Yan > > --- > > tools/perf/util/cs-etm.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c > > index 4ba0f871f086..4bc2d9709d4f 100644 > > --- a/tools/perf/util/cs-etm.c > > +++ b/tools/perf/util/cs-etm.c > > @@ -940,7 +940,7 @@ u64 cs_etm__last_executed_instr(const struct cs_etm_packet *packet) > > static inline u64 cs_etm__instr_addr(struct cs_etm_queue *etmq, > > u64 trace_chan_id, > > const struct cs_etm_packet *packet, > > - u64 offset) > > + s64 offset) > > In Suzuki's reply there was two choices, 1) move the while(offset > 0) to > while (offset) or change the type of @offset to an s64. Here we know offset > can't be negative because of the > tidq->period_instructions >= etm->instructions_sample_period > > in function cs_etm__sample(). As such I think option #1 is the right way to > deal with this rather than changing the type of the variable. I took sometime to use formulas to prove that 'offset' is possible to be a negative value :) Just paste the updated commit log at here for review: Pi: period_instructions Ie: instrs_executed Io: instrs_over Ip: instructions_sample_period Pi' = Pi + Ie -> New period_instructions equals to the old period_instructions + instrs_executed Io = Pi' - Ip -> period_instructions - instructions_sample_period offset = Ie - Io - 1 = Ie - (Pi' - Ip) -1 = Ie - (Pi + Ie - Ip) -1 = Ip - Pi - 1 In theory, if Ip (instructions_sample_period) is small enough and Pi (period_instructions) is bigger than Ip, then it will lead to the negative value for 'offset'. So let's see below command: perf inject --itrace=i1il128 -i perf.data -o perf.data.new With this command, 'offset' is very easily to be a negative value when handling packets; this is because if use the inject option 'i1', then instructions_sample_period equals to 1; so: offset = 1 - Pi - 1 = -Pi Any Pi bigger than zero leads 'offset' to a negative value. Thanks, Leo Yan > > { > > if (packet->isa == CS_ETM_ISA_T32) { > > u64 addr = packet->start_addr; > > @@ -1372,7 +1372,7 @@ static int cs_etm__sample(struct cs_etm_queue *etmq, > > * sample is reported as though instruction has just been > > * executed, but PC has not advanced to next instruction) > > */ > > - u64 offset = (instrs_executed - instrs_over - 1); > > + s64 offset = (instrs_executed - instrs_over - 1); > > u64 addr = cs_etm__instr_addr(etmq, trace_chan_id, > > tidq->packet, offset); > > > > -- > > 2.17.1 > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel