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a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=tromey.com; s=default; h=Content-Type:MIME-Version:Message-ID:In-Reply-To:Date:References :Subject:Cc:To:From:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=C8A4lu93K1TZzGmChHtJT+u9lftoSjYMcX/Bfpo4ZoI=; b=Cs7MRaJ2WQtQJsK7b8yBSCM882 9PipR70K5hzOE3v4uWGyhI+i1gN6aeJp8Swt3lH69YObPxw+wUdKjZAe8nrpZYo0Gv4GADWBhwgNi HHzlU9gP2Td7b/syYqVwdc6BE; Received: from 75-166-128-165.hlrn.qwest.net ([75.166.128.165]:55938 helo=murgatroyd) by box5379.bluehost.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1nCmdp-002jBW-V9; Wed, 26 Jan 2022 11:03:34 -0700 From: Tom Tromey To: Kevin Buettner via Gdb-patches Subject: Re: [PATCH] Fix GDB internal error by using text (instead of data) section offset References: <20220125230429.3329876-1-kevinb@redhat.com> X-Attribution: Tom Date: Wed, 26 Jan 2022 11:03:33 -0700 In-Reply-To: <20220125230429.3329876-1-kevinb@redhat.com> (Kevin Buettner via Gdb-patches's message of "Tue, 25 Jan 2022 16:04:29 -0700") Message-ID: <87r18u9xxm.fsf@tromey.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - box5379.bluehost.com X-AntiAbuse: Original Domain - sourceware.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - tromey.com X-BWhitelist: no X-Source-IP: 75.166.128.165 X-Source-L: No X-Exim-ID: 1nCmdp-002jBW-V9 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: 75-166-128-165.hlrn.qwest.net (murgatroyd) [75.166.128.165]:55938 X-Source-Auth: tom+tromey.com X-Email-Count: 1 X-Source-Cap: ZWx5bnJvYmk7ZWx5bnJvYmk7Ym94NTM3OS5ibHVlaG9zdC5jb20= X-Local-Domain: yes 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: , Errors-To: gdb-patches-bounces+public-inbox=simark.ca@sourceware.org Sender: "Gdb-patches" Kevin> #3 0x000000000097c630 in stap_probe::get_relocated_address (this=0xa1a17a0, Kevin> objfile=0x4fa48f0) Kevin> at gdb/stap-probe.c:1341 One oddity here is that get_relocated_address calls this->get_address(), which returns m_address, which is documented as: /* The address where the probe is inserted, relative to SECT_OFF_TEXT. */ CORE_ADDR m_address; So using SECT_OFF_DATA here seems wrong in the first place. Kevin> The obvious solution is to use some other section offset instead - as Kevin> I recall, on Linux, the section offsets (for those sections which Kevin> exist) will all be the same. Is this a Linux thing or an ELF thing? I don't know. Kevin> So, what happens if there's no .text section? Not probe-related but this is already a way to crash gdb: https://sourceware.org/bugzilla/show_bug.cgi?id=19342 https://sourceware.org/bugzilla/show_bug.cgi?id=25678 ... which is why I was curious about the ELF thing. Like perhaps this could all be made more robust somehow. Your patch seems fine to me, though I don't have any idea if the dtrace part is correct. Tom