<https://sourceware.org/ml/gdb-patches/2014-09/msg00398.html>

  Message-Id: <1410525085-29172-1-git-send-email-emachado@linux.vnet.ibm.com>

commit 9d9bf2df89db515958b429a1aeb1db38884ba488

Author: Edjunior Barbosa Machado <emachado@linux.vnet.ibm.com>

Date:   Fri Sep 12 09:20:25 2014 -0300

    PR tdep/17379: Fix internal-error when stack pointer is invalid.

    The problem is that rs6000_frame_cache attempts to read the stack backchain via

    read_memory_unsigned_integer, which throws an exception if the stack pointer is

    invalid.  With this patch, it calls safe_read_memory_integer instead, which

    doesn't throw an exception and allows for safe handling of that situation.

    gdb/ChangeLog

    2014-09-12  Edjunior Barbosa Machado  <emachado@linux.vnet.ibm.com>

    	    Ulrich Weigand  <uweigand@de.ibm.com>

    	PR tdep/17379

    	* rs6000-tdep.c (rs6000_frame_cache): Use safe_read_memory_integer

    	instead of read_memory_unsigned_integer.

    gdb/testcase/ChangeLog

    2014-09-12  Edjunior Barbosa Machado  <emachado@linux.vnet.ibm.com>

    	PR tdep/17379

    	* gdb.arch/powerpc-stackless.S: New file.

    	* gdb.arch/powerpc-stackless.exp: New file.

Index: gdb-7.6.1/gdb/rs6000-tdep.c

===================================================================

--- gdb-7.6.1.orig/gdb/rs6000-tdep.c

+++ gdb-7.6.1/gdb/rs6000-tdep.c

@@ -3241,9 +3241,14 @@ rs6000_frame_cache (struct frame_info *t

     }

   if (!fdata.frameless)

-    /* Frameless really means stackless.  */

-    cache->base

-      = read_memory_unsigned_integer (cache->base, wordsize, byte_order);

+    {

+      /* Frameless really means stackless.  */

+      LONGEST backchain;

+

+      if (safe_read_memory_integer (cache->base, wordsize,

+				    byte_order, &backchain))

+        cache->base = (CORE_ADDR) backchain;

+    }

   trad_frame_set_value (cache->saved_regs,

 			gdbarch_sp_regnum (gdbarch), cache->base);

Index: gdb-7.6.1/gdb/testsuite/gdb.arch/powerpc-stackless.S

===================================================================

--- /dev/null

+++ gdb-7.6.1/gdb/testsuite/gdb.arch/powerpc-stackless.S

@@ -0,0 +1,24 @@

+/* This testcase is part of GDB, the GNU debugger.

+

+   Copyright 2014 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 <http://www.gnu.org/licenses/>.  */

+

+#include <ppc-asm.h>

+

+FUNC_START(main)

+        li      sp,0

+        mtlr    sp

+        blr

+FUNC_END(main)

Index: gdb-7.6.1/gdb/testsuite/gdb.arch/powerpc-stackless.exp

===================================================================

--- /dev/null

+++ gdb-7.6.1/gdb/testsuite/gdb.arch/powerpc-stackless.exp

@@ -0,0 +1,42 @@

+# Copyright 2014 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 2 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 <http://www.gnu.org/licenses/>.

+

+# Testcase for PR tdep/17379.

+

+if {![istarget "powerpc*-*-*"]} then {

+    verbose "Skipping powerpc-stackless.exp"

+    return

+}

+

+standard_testfile .S

+

+if { [prepare_for_testing $testfile.exp $testfile $srcfile] } {

+    untested powerpc-stackless.exp

+    return -1

+}

+

+# Run until SIGSEGV.

+gdb_run_cmd

+

+set test "run until SIGSEGV"

+gdb_test_multiple "" $test {

+    -re "Program received signal SIGSEGV.*$gdb_prompt $" {

+  pass $test

+    }

+}

+

+# Ensure that 'info registers' works properly and does not generate

+# an internal-error.

+gdb_test "info registers" "r0.*" "info registers"