From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 15139 invoked by alias); 22 Apr 2013 06:19:19 -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 15127 invoked by uid 89); 22 Apr 2013 06:19:18 -0000 X-Spam-SWARE-Status: No, score=-6.7 required=5.0 tests=AWL,BAYES_00,KHOP_RCVD_UNTRUST,RCVD_IN_DNSWL_HI,RCVD_IN_HOSTKARMA_W,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.1 Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.84/v0.84-167-ge50287c) with ESMTP; Mon, 22 Apr 2013 06:19:11 +0000 Received: from int-mx02.intmail.prod.int.phx2.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r3M6J9X3010158 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 22 Apr 2013 02:19:10 -0400 Received: from psique (ovpn-113-115.phx2.redhat.com [10.3.113.115]) by int-mx02.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id r3M6J63M028660 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Mon, 22 Apr 2013 02:19:08 -0400 From: Sergio Durigan Junior To: GDB Patches Cc: Andrew Haley , Tom Tromey Subject: Re: [PATCH] Fix ARM sign-extension on PC when using 64-bit BFD References: X-URL: http://www.redhat.com Date: Mon, 22 Apr 2013 13:32:00 -0000 In-Reply-To: (Sergio Durigan Junior's message of "Wed, 17 Apr 2013 01:56:19 -0300") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-SW-Source: 2013-04/txt/msg00655.txt.bz2 On Wednesday, April 17 2013, I wrote: Ping. > Andrew Haley found a bug on GDB running on ARM when using > --enable-64-bit-bfd. Basically the issue happens when dealing with "bl" > instructions: GDB does branch destination calculation and (wrongly) > sign-extends the PC. Here is a piece of his original message explaining > the problem: > >> next_pc = arm_get_next_pc (frame, get_frame_pc (frame)); >> >> /* The Linux kernel offers some user-mode helpers in a high page. We can >> not read this page (as of 2.6.23), and even if we could then we couldn't >> set breakpoints in it, and even if we could then the atomic operations >> would fail when interrupted. They are all called as functions and return >> to the address in LR, so step to there instead. */ >> if (next_pc > 0xffff0000) >> next_pc = get_frame_register_unsigned (frame, ARM_LR_REGNUM); >> >> arm_insert_single_step_breakpoint (gdbarch, aspace, next_pc); >> >> Unfortunately, branch destination addresses are SIGN EXTENDED to 64 >> bits. So, >> >> (top-gdb) p/x next_pc >> $14 = 0xffffffffb6df2864 >> >> Which triggers the next_pc = get_frame_register_unsigned(), and we >> cannot step into any branches because the destination PC is wrong. > > Anyway, the fix is simple and Andrew himself provided it for us. It > took a while for me to figure out how to trigger the bug (in order to > write a testcase for it), but I finally made it. > > The attached patch fixes the problem (by casting to `unsigned long' > instead of just `long'), and also includes a testcase to reproduce the > issue. > > OK to apply? BTW, I guess this is trivial enough to be included in 7.6 > as well, do you agree? > > Thanks, > > -- > Sergio > > gdb/ > 2013-04-11 Andrew Haley > > * arm-tdep.c (BranchDest): Cast result as "unsigned long", > instead of "long". > > gdb/testsuite > 2013-04-11 Sergio Durigan Junior > > * gdb.arch/arm-bl-branch-dest.c: New file. > * gdb.arch/arm-bl-branch-dest.exp: Likewise. > > diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c > index 2a11890..16cb488 100644 > --- a/gdb/arm-tdep.c > +++ b/gdb/arm-tdep.c > @@ -521,7 +521,7 @@ skip_prologue_function (struct gdbarch *gdbarch, CORE_ADDR pc, int is_thumb) > #define sbits(obj,st,fn) \ > ((long) (bits(obj,st,fn) | ((long) bit(obj,fn) * ~ submask (fn - st)))) > #define BranchDest(addr,instr) \ > - ((CORE_ADDR) (((long) (addr)) + 8 + (sbits (instr, 0, 23) << 2))) > + ((CORE_ADDR) (((unsigned long) (addr)) + 8 + (sbits (instr, 0, 23) << 2))) > > /* Extract the immediate from instruction movw/movt of encoding T. INSN1 is > the first 16-bit of instruction, and INSN2 is the second 16-bit of > diff --git a/gdb/testsuite/gdb.arch/arm-bl-branch-dest.c b/gdb/testsuite/gdb.arch/arm-bl-branch-dest.c > new file mode 100644 > index 0000000..98269d0 > --- /dev/null > +++ b/gdb/testsuite/gdb.arch/arm-bl-branch-dest.c > @@ -0,0 +1,29 @@ > +/* This testcase is part of GDB, the GNU debugger. > + > + Copyright 2013 Free Software Foundation, Inc. > + > + This program is free software; you can redistribute it and/or modify > + it under the terms of the GNU General Public License as published by > + the Free Software Foundation; either version 3 of the License, or > + (at your option) any later version. > + > + This program is distributed in the hope that it will be useful, > + but WITHOUT ANY WARRANTY; without even the implied warranty of > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + GNU General Public License for more details. > + > + You should have received a copy of the GNU General Public License > + along with this program. If not, see . */ > + > +static void > +foo (int a) > +{ > + ++a; > +} > + > +int > +main (int argc, char *argv[]) > +{ > + foo (10); > + return 0; > +} > diff --git a/gdb/testsuite/gdb.arch/arm-bl-branch-dest.exp b/gdb/testsuite/gdb.arch/arm-bl-branch-dest.exp > new file mode 100644 > index 0000000..1e433f3 > --- /dev/null > +++ b/gdb/testsuite/gdb.arch/arm-bl-branch-dest.exp > @@ -0,0 +1,37 @@ > +# Copyright (C) 2013 Free Software Foundation, Inc. > +# > +# This program is free software; you can redistribute it and/or modify > +# it under the terms of the GNU General Public License as published by > +# the Free Software Foundation; either version 3 of the License, or > +# (at your option) any later version. > +# > +# This program is distributed in the hope that it will be useful, > +# but WITHOUT ANY WARRANTY; without even the implied warranty of > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > +# GNU General Public License for more details. > +# > +# You should have received a copy of the GNU General Public License > +# along with this program. If not, see .+ > +if { ![istarget "arm*-*-*"] } { > + verbose "Skipping ${testfile}." > + return > +} > + > +standard_testfile > + > +# We need to load the text segment in a high address. This is because > +# the bug we are dealing with happened when GDB sign-extended the PC > +# on ARM, causing the PC to acquire a wrong value. That's why we use > +# the "-Wl,-Ttext-segment" option compile the binary. > + > +if { [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile} \ > + [list debug ldflags=-Wl,-Ttext-segment=0xb0000000]] } { > + return -1 > +} > + > +if { ![runto_main] } { > + return -1 > +} > + > +gdb_test "next" "\[0-9\]+\\s+return 0;" -- Sergio