From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 24571 invoked by alias); 30 Dec 2011 11:11:41 -0000 Received: (qmail 24560 invoked by uid 22791); 30 Dec 2011 11:11:39 -0000 X-SWARE-Spam-Status: No, hits=-7.3 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_HI,RP_MATCHES_RCVD,SPF_HELO_PASS X-Spam-Check-By: sourceware.org Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Fri, 30 Dec 2011 11:11:23 +0000 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id pBUBBA80018048 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Fri, 30 Dec 2011 06:11:10 -0500 Received: from host2.jankratochvil.net (ovpn-116-32.ams2.redhat.com [10.36.116.32]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id pBUBB5A4003016 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Fri, 30 Dec 2011 06:11:07 -0500 Date: Fri, 30 Dec 2011 11:25:00 -0000 From: Jan Kratochvil To: Joel Brobecker Cc: Mark Kettenis , gdb-patches@sourceware.org Subject: Re: [patch] Fix gdb.cp/gdb2495.exp regression with gcc-4.7 #3 Message-ID: <20111230111104.GA21767@host2.jankratochvil.net> References: <20111222202047.GA16110@host2.jankratochvil.net> <20111227045606.GE23376@adacore.com> <20111228161208.GB10556@host2.jankratochvil.net> <20111228180148.GA18057@host2.jankratochvil.net> <201112282009.pBSK9LHn029918@glazunov.sibelius.xs4all.nl> <20111229231251.GA27794@host2.jankratochvil.net> <20111230033020.GA20473@adacore.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111230033020.GA20473@adacore.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-IsSubscribed: yes 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 X-SW-Source: 2011-12/txt/msg00903.txt.bz2 On Fri, 30 Dec 2011 04:30:20 +0100, Joel Brobecker wrote: > > not preferred by me TBH. > > I don't understand why, though. ON_STACK seems to be perfect, as > we control exactly what's there, There exist already so many security frameworks in the toolchain and Linux kernel I expect it will have some compatibility problems with them. But I was unable to see any problems at least with RHEl-6.2 SELinux targeted policy and sandbox_t containment and I do not know any other real countercase. > I keep staring at the diff, In this case the diff is not much readable, one should read the patched code IMO. > and I can't figure out how the AT_SYMBOL case is falling through, There was one leftover "break;", thanks. > > + /* FALLTHROUGH */ > > + case AT_ENTRY_POINT: > > Is this really a FALLTHROUGH? It was not, it is now. > I can't remember if you explicitly decided to use the second byte > and then changed your mind, or whether this is a typo from the fact > that the breakpoint instruction on x86 is 1 byte long? Suggest > replacing with: > > Therefore, we adjust the return address by the length > of a breakpoint, guaranteeing that the unwinder finds > the correct function as the caller. I agree my text was wrong. It was instruction length placed there before. It is now breakpoint length in this patch but it was incorrectly described as "byte" (thinking about x86* myself while writing it). Thanks, Jan 2011-12-30 Jan Kratochvil Joel Brobecker Fix regression for gdb.cp/gdb2495.exp with gcc-4.7. * arch-utils.c (displaced_step_at_entry_point): Incrase BP_LEN skip to 3 times. * infcall.c (call_function_by_hand) : Move it upwards and fall through into AT_ENTRY_POINT. (call_function_by_hand) : New variable bp_len. Adjust DUMMY_ADDR with it. * ppc-linux-tdep.c (ppc_linux_displaced_step_location): Increase PPC_INSN_SIZE skip to 3 times. --- a/gdb/arch-utils.c +++ b/gdb/arch-utils.c @@ -86,7 +86,7 @@ displaced_step_at_entry_point (struct gdbarch *gdbarch) We don't want displaced stepping to interfere with those breakpoints, so leave space. */ gdbarch_breakpoint_from_pc (gdbarch, &addr, &bp_len); - addr += bp_len * 2; + addr += bp_len * 3; return addr; } --- a/gdb/infcall.c +++ b/gdb/infcall.c @@ -631,17 +631,6 @@ call_function_by_hand (struct value *function, int nargs, struct value **args) args, nargs, target_values_type, &real_pc, &bp_addr, get_current_regcache ()); break; - case AT_ENTRY_POINT: - { - CORE_ADDR dummy_addr; - - real_pc = funaddr; - dummy_addr = entry_point_address (); - /* A call dummy always consists of just a single breakpoint, so - its address is the same as the address of the dummy. */ - bp_addr = dummy_addr; - break; - } case AT_SYMBOL: /* Some executables define a symbol __CALL_DUMMY_ADDRESS whose address is the location where the breakpoint should be @@ -661,11 +650,39 @@ call_function_by_hand (struct value *function, int nargs, struct value **args) dummy_addr = gdbarch_convert_from_func_ptr_addr (gdbarch, dummy_addr, ¤t_target); + /* A call dummy always consists of just a single breakpoint, + so its address is the same as the address of the dummy. */ + bp_addr = dummy_addr; + break; } - else - dummy_addr = entry_point_address (); - /* A call dummy always consists of just a single breakpoint, - so it's address is the same as the address of the dummy. */ + } + /* FALLTHROUGH */ + case AT_ENTRY_POINT: + { + CORE_ADDR dummy_addr; + int bp_len; + + real_pc = funaddr; + dummy_addr = entry_point_address (); + + /* If the inferior call throws an uncaught C++ exception, + the inferior unwinder tries to unwind all frames, including + our dummy frame. The unwinder determines the address of + the calling instruction by subtracting 1 to the return + address. So, using the entry point's address as the return + address would lead the unwinder to use the unwinding + information of the code immediately preceding the entry + point. This information, if found, is invalid for the dummy + frame, and can potentially crash the inferior's unwinder. + Therefore, we adjust the return address by the length of + a breakpoint, guaranteeing that the unwinder finds the + correct function as the caller. */ + + gdbarch_breakpoint_from_pc (gdbarch, &dummy_addr, &bp_len); + dummy_addr += bp_len; + + /* A call dummy always consists of just a single breakpoint, so + its address is the same as the address of the dummy. */ bp_addr = dummy_addr; break; } --- a/gdb/ppc-linux-tdep.c +++ b/gdb/ppc-linux-tdep.c @@ -1075,7 +1075,7 @@ ppc_linux_displaced_step_location (struct gdbarch *gdbarch) /* Inferior calls also use the entry point as a breakpoint location. We don't want displaced stepping to interfere with those breakpoints, so leave space. */ - ppc_linux_entry_point_addr = addr + 2 * PPC_INSN_SIZE; + ppc_linux_entry_point_addr = addr + 3 * PPC_INSN_SIZE; } return ppc_linux_entry_point_addr;