Fix non executable stack handling when calling functions in the inferior.

When gdb creates a dummy frame to execute a function in the inferior,
the process may generate a SIGSEGV, SIGTRAP or SIGILL because the stack
is non executable. If the signal handler set in gdb has option print
or stop enabled for these signals gdb handles this correctly.

However, in the case of noprint and nostop the signal is short-circuited
and the inferior process is sent the signal directly. This causes the
inferior to crash because of gdb.

This patch adds a check for SIGSEGV, SIGTRAP or SIGILL so that these
signals are sent to gdb rather than short-circuited in the inferior.
gdb then handles them properly and the inferior process does not
crash.

This patch also fixes the same behavior in gdbserver.

Also added a small testcase to test the issue called catch-gdb-caused-signals.

This applies to Linux only, tested on Linux.

gdb/ChangeLog:
	PR breakpoints/16812
	* linux-nat.c (linux_nat_filter_event): Report SIGTRAP,SIGILL,SIGSEGV.
	* nat/linux-ptrace.c (linux_wstatus_maybe_breakpoint): Add.
	* nat/linux-ptrace.h: Add linux_wstatus_maybe_breakpoint.

gdb/gdbserver/ChangeLog:
	PR breakpoints/16812
	* linux-low.c (wstatus_maybe_breakpoint): Remove.
	(linux_low_filter_event): Update wstatus_maybe_breakpoint name.
	(linux_wait_1): Report SIGTRAP,SIGILL,SIGSEGV.

gdb/testsuite/ChangeLog:
	PR breakpoints/16812
	* gdb.base/catch-gdb-caused-signals.c: New file.
	* gdb.base/catch-gdb-caused-signals.exp: New file.

1 files changed, 63 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.base/catch-gdb-caused-signals.exp b/gdb/testsuite/gdb.base/catch-gdb-caused-signals.exp
new file mode 100644
index 00000000000..8ba3be5499c
--- /dev/null
+++ b/gdb/testsuite/gdb.base/catch-gdb-caused-signals.exp
@@ -0,0 +1,63 @@
+# This testcase is part of GDB, the GNU debugger.
+
+# Copyright 2015 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/>.
+
+# Test that checks if we handle a SIGSEGV,SIGILL caused by gdb in the inferior
+# even if we have noprint,nostop options set in handle SIGSEV,SIGILL
+# See PR breakpoints/16812
+
+standard_testfile
+
+# Some targets can't call functions, so don't even bother with this
+# test.
+if [target_info exists gdb,cannot_call_functions] {
+    unsupported "cannot call functions"
+    return
+}
+
+set dp_location [gdb_get_line_number "set dprintf here"]
+set bp_location [gdb_get_line_number "set breakpoint here"]
+
+if {[prepare_for_testing $testfile.exp $testfile $srcfile debug]} {
+    return -1
+}
+
+if ![runto_main] {
+    fail "Can't run to main to make the tests"
+    return -1
+}
+
+gdb_test "handle SIGSEGV nostop noprint" \
+    "Signal\[ \t\]+Stop\[ \t\]+Print\[ \t\]+Pass to program\[ \t\]+Description\r\nSIGSEGV\[ \t\]+No\[ \t\]+No\[ \t\]+Yes\[ \t\].*"
+gdb_test "handle SIGILL nostop noprint" \
+    "Signal\[ \t\]+Stop\[ \t\]+Print\[ \t\]+Pass to program\[ \t\]+Description\r\nSIGILL\[ \t\]+No\[ \t\]+No\[ \t\]+Yes\[ \t\].*"
+
+gdb_test "print return_one()" " = 1"
+
+if ![target_info exists gdb,noinferiorio] {
+
+    # Clean up the breakpoint state.
+    delete_breakpoints
+
+    gdb_breakpoint $bp_location
+
+    gdb_test_no_output "set dprintf-style call"
+
+    # Also test with dprintf since the original bug was noticed using dprintf.
+    gdb_test "dprintf $dp_location,\"testdprintf\\n\"" "Dprintf .*"
+
+    gdb_test "continue" "testdprintf.*"
+}