From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 48751 invoked by alias); 11 Mar 2019 17:24:36 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 45868 invoked by uid 89); 11 Mar 2019 17:24:27 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-6.1 required=5.0 tests=AWL,BAYES_00,SPF_PASS autolearn=ham version=3.3.1 spammy=arrange, interest, HContent-Transfer-Encoding:8bit, H*UA:Macintosh X-HELO: mx2.freebsd.org Received: from mx2.freebsd.org (HELO mx2.freebsd.org) (8.8.178.116) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 11 Mar 2019 17:24:16 +0000 Received: from mx1.freebsd.org (mx1.freebsd.org [96.47.72.80]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (Client CN "mx1.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx2.freebsd.org (Postfix) with ESMTPS id D19C7A10D8; Mon, 11 Mar 2019 17:24:09 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Received: from smtp.freebsd.org (smtp.freebsd.org [96.47.72.83]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "smtp.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 223FE712F7; Mon, 11 Mar 2019 17:24:09 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Received: from John-Baldwins-MacBook-Pro-3.local (ralph.baldwin.cx [66.234.199.215]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client did not present a certificate) (Authenticated sender: jhb) by smtp.freebsd.org (Postfix) with ESMTPSA id A041216434; Mon, 11 Mar 2019 17:24:08 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Subject: Re: [RFC 5/6] Introduce thread-safe way to handle SIGSEGV To: Tom Tromey , gdb-patches@sourceware.org References: <20190309172300.2764-1-tom@tromey.com> <20190309172300.2764-6-tom@tromey.com> From: John Baldwin Openpgp: preference=signencrypt Message-ID: Date: Mon, 11 Mar 2019 17:24:00 -0000 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:60.0) Gecko/20100101 Thunderbird/60.5.3 MIME-Version: 1.0 In-Reply-To: <20190309172300.2764-6-tom@tromey.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 223FE712F7 X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org X-Spamd-Result: default: False [-2.97 / 15.00]; local_wl_from(0.00)[FreeBSD.org]; NEURAL_HAM_MEDIUM(-1.00)[-0.996,0]; NEURAL_HAM_SHORT(-0.98)[-0.979,0]; ASN(0.00)[asn:11403, ipnet:96.47.64.0/20, country:US]; NEURAL_HAM_LONG(-1.00)[-1.000,0] X-IsSubscribed: yes X-SW-Source: 2019-03/txt/msg00223.txt.bz2 On 3/9/19 9:22 AM, Tom Tromey wrote: > The gdb demangler installs a SIGSEGV handler in order to protect gdb > from demangler bugs. However, this is not thread-safe, as signal > handlers are global to the process. > > This patch changes gdb to always install a global SIGSEGV handler, and > then lets thread indicate their interest in handling the signal by > setting a thread-local variable. > > This patch then arranges for the demangler code to use this; being > sure to arrange for calls to warning and the like to be done on the > main thread. The one downside of always having a handler is that the $_siginfo after a "normal" sig11 in GDB won't be valid anymore (it will have SI_USER set now instead and si_addr won't be valid, etc.). We could "fix" this by having signal frames supply $_siginfo though I'm not sure what the most intuitive model of that would be. -- John Baldwin