From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 32741 invoked by alias); 26 Jan 2004 16:21:05 -0000 Mailing-List: contact gdb-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sources.redhat.com Received: (qmail 32617 invoked from network); 26 Jan 2004 16:21:03 -0000 Received: from unknown (HELO localhost.redhat.com) (66.30.197.194) by sources.redhat.com with SMTP; 26 Jan 2004 16:21:03 -0000 Received: from gnu.org (localhost [127.0.0.1]) by localhost.redhat.com (Postfix) with ESMTP id 086C72B8F; Mon, 26 Jan 2004 11:21:01 -0500 (EST) Message-ID: <40153E6D.2050805@gnu.org> Date: Mon, 26 Jan 2004 16:21:00 -0000 From: Andrew Cagney User-Agent: Mozilla/5.0 (X11; U; NetBSD macppc; en-US; rv:1.0.2) Gecko/20030820 MIME-Version: 1.0 To: Mark Kettenis Cc: gdb@sources.redhat.com Subject: Re: [RFC] Non-executable stack on SPARC References: <200401252350.i0PNoB1O021806@elgar.kettenis.dyndns.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-SW-Source: 2004-01/txt/msg00303.txt.bz2 > A while ago, I established that getting inferior function calls on > SPARC working with a non-executable stack is remarkably simple. Just > acknowledging that breakpoint instructions may cause SIGSEGV, as per > the attached patch, is enough. However, some people were afraid that > blindly applying this patch might cause some problems on other > targets. I think there are two alternatives: I thought the original patch was already committed? :-( > 1. Only check for SIGSEGV if the target in question uses "ON_STACK" > for its call_dummy_location. A more robust check would be to confirm that a breakpoint is at that address (naturally ignoring decr pc after break :-). However, does later code check exactly that - confirming that the breakpoint explains the stop reason? > 2. Add a new method to the architecture vector to check whether a > particular signal may have been the result of a breakpoint > instruction. Suggested name & signature: > > int breakpoint_signal_p (struct gdbarch *gdbarch, int signal) For this, that would be wrong. The target, in combination with the breakpoint code, determines if a breakpoint leads to a sigsegv. Ex: breakpoint code uses the target to unmap code segment, the target indicates that a segment isn't executable, ... > Preferences? > > I'd like to get this sorted before 6.1, since OpenBSD/sparc has a > non-executable stack, and some people are running SPARC Solaris with a > non-executable stack too. Assuming that for VLIW gdb replaces the entire instruction bundle with a breakpoint, a breakpoint instruction can only ever generate a sigtrap (et.al.) (if executed) or sigsegv (if not accessible) so provided there is a breakpoint at the PC I don't think there is any possability of confusion (but again ignore decr pc after break :-). Andrew