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.

2 files changed, 66 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.arch/powerpc-stackless.S b/gdb/testsuite/gdb.arch/powerpc-stackless.S
new file mode 100644
index 0000000..bbf92bb
--- /dev/null
+++ b/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)
diff --git a/gdb/testsuite/gdb.arch/powerpc-stackless.exp b/gdb/testsuite/gdb.arch/powerpc-stackless.exp
new file mode 100644
index 0000000..420bcbc
--- /dev/null
+++ b/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"