From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from simark.ca by simark.ca with LMTP id 0FjbDEgDA2FyTAAAWB0awg (envelope-from ) for ; Thu, 29 Jul 2021 15:36:40 -0400 Received: by simark.ca (Postfix, from userid 112) id 26B471EDFB; Thu, 29 Jul 2021 15:36:40 -0400 (EDT) X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on simark.ca X-Spam-Level: X-Spam-Status: No, score=-1.1 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (server2.sourceware.org [8.43.85.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by simark.ca (Postfix) with ESMTPS id 5FCC41E4A3 for ; Thu, 29 Jul 2021 15:36:39 -0400 (EDT) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id F001E3853C0B for ; Thu, 29 Jul 2021 19:36:38 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org F001E3853C0B DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1627587399; bh=S6TpomGdyAqBU4JOwdFXl1h7ksL6pf5dmTI+MNRpArs=; h=Subject:To:References:Date:In-Reply-To:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To: From; b=VwIsgOP2tN+15qHgO0BkuYcRO0NryCDGYBoBhSnRCFL+lvM8nH+3TfM2XGqjSPjq3 N+a4YxMd51zuRn0TAf20JQUPPWm0Ik09Rbn0VapeZp/hicOGSSiyW8Oxathx+QF5AD I0f9PW4OlfdaSswF+YWam952MdRfaqmun3iwmasY= Received: from smtp.polymtl.ca (smtp.polymtl.ca [132.207.4.11]) by sourceware.org (Postfix) with ESMTPS id AE5E73858C27 for ; Thu, 29 Jul 2021 19:36:18 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org AE5E73858C27 Received: from simark.ca (simark.ca [158.69.221.121]) (authenticated bits=0) by smtp.polymtl.ca (8.14.7/8.14.7) with ESMTP id 16TJaC5L024854 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 29 Jul 2021 15:36:17 -0400 DKIM-Filter: OpenDKIM Filter v2.11.0 smtp.polymtl.ca 16TJaC5L024854 Received: from [10.0.0.11] (192-222-157-6.qc.cable.ebox.net [192.222.157.6]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by simark.ca (Postfix) with ESMTPSA id 81AB31E4A3; Thu, 29 Jul 2021 15:36:12 -0400 (EDT) Subject: Re: [PATCH] Fix displaced stepping watchpoint check order To: Luis Machado , gdb-patches@sourceware.org References: <20210608154230.354202-1-luis.machado@linaro.org> Message-ID: Date: Thu, 29 Jul 2021 15:36:12 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <20210608154230.354202-1-luis.machado@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Poly-FromMTA: (simark.ca [158.69.221.121]) at Thu, 29 Jul 2021 19:36:12 +0000 X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Simon Marchi via Gdb-patches Reply-To: Simon Marchi Errors-To: gdb-patches-bounces+public-inbox=simark.ca@sourceware.org Sender: "Gdb-patches" I think this is ok, but in all honestly I don't completely understand how the interaction between watchpoints and displaced stepping is expected to work. Just some nits: On 2021-06-08 11:42 a.m., Luis Machado via Gdb-patches wrote: > When checking the stopped data address, I noticed, under some circumstances, > that the instruction at PC wasn't the expected one. This happens because the > displaced stepping machinery restores the buffer before checking if the > instruction executed successfully, which in turn calls the watchpoint check. > > I guess this was never noticed because stopped data address checks usually > don't need to fetch the instruction at PC, but AArch64 needs to do it from > now on. Can you clarify what you mean by "from now on"? Can you indicate what change you are referring to? > > We should check if the instruction executed successfully before we restore the > scratchpad contents. > > Regression tested on aarch64-linux/Ubuntu 20.04. > > gdb/ChangeLog: > > YYYY-MM-DD Luis Machado > > * displaced-stepping.c (displaced_step_buffers::finish): Move check > upwards. > --- > gdb/displaced-stepping.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/gdb/displaced-stepping.c b/gdb/displaced-stepping.c > index 59b78c22f6a..06324d523d8 100644 > --- a/gdb/displaced-stepping.c > +++ b/gdb/displaced-stepping.c > @@ -227,6 +227,11 @@ displaced_step_buffers::finish (gdbarch *arch, thread_info *thread, > > ULONGEST len = gdbarch_max_insn_length (arch); > > + /* Check if the execution was successful before restoring the buffer > + contents. */ > + bool instruction_executed_successfully > + = displaced_step_instruction_executed_successfully (arch, sig); Maybe extend the comment to say "why". Right now I think it just states what is in plain sight when looking at the code, I think it would be more useful if it said why it's important to do that. Simon