[binutils-gdb] Fix non executable stack handling when calling functions in the inferior.

[Antoine Tremblay <hexa at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=c9587f88230e9df836f17c195181aaf50c3a1117

commit c9587f88230e9df836f17c195181aaf50c3a1117
Author: Antoine Tremblay <antoine.tremblay@ericsson.com>
Date:   Thu Feb 12 14:55:08 2015 -0500

    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.

Diff:
---
 gdb/ChangeLog                                      |  7 +++
 gdb/gdbserver/ChangeLog                            |  7 +++
 gdb/gdbserver/linux-low.c                          | 21 ++------
 gdb/linux-nat.c                                    |  6 ++-
 gdb/nat/linux-ptrace.c                             | 13 +++++
 gdb/nat/linux-ptrace.h                             |  1 +
 gdb/testsuite/ChangeLog                            |  6 +++
 gdb/testsuite/gdb.base/catch-gdb-caused-signals.c  | 36 +++++++++++++
 .../gdb.base/catch-gdb-caused-signals.exp          | 63 ++++++++++++++++++++++
 9 files changed, 142 insertions(+), 18 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 5c5b75a..303bb96 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2015-02-19  Antoine Tremblay  <antoine.tremblay@ericsson.com>
+
+	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.
+
 2015-02-19  David Taylor  <dtaylor@emc.com>
 
 	* common/ax.def (setv): Fix consumed entry in setv DEFOP.
diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 4badd9e..06848e0 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,10 @@
+2015-02-19  Antoine Tremblay  <antoine.tremblay@ericsson.com>
+
+	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.
+
 2015-02-10  Antoine Tremblay <antoine.tremblay@ericsson.com>
 
 	PR breakpoints/15956
diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index eff940d..1869857 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -1738,19 +1738,6 @@ dequeue_one_deferred_signal (struct lwp_info *lwp, int *wstat)
   return 0;
 }
 
-/* Return true if the event in LP may be caused by breakpoint.  */
-
-static int
-wstatus_maybe_breakpoint (int wstatus)
-{
-  return (WIFSTOPPED (wstatus)
-	  && (WSTOPSIG (wstatus) == SIGTRAP
-	      /* SIGILL and SIGSEGV are also treated as traps in case a
-		 breakpoint is inserted at the current PC.  */
-	      || WSTOPSIG (wstatus) == SIGILL
-	      || WSTOPSIG (wstatus) == SIGSEGV));
-}
-
 /* Fetch the possibly triggered data watchpoint info and store it in
    CHILD.
 
@@ -1898,7 +1885,7 @@ linux_low_filter_event (int lwpid, int wstat)
   if (WIFSTOPPED (wstat) && WSTOPSIG (wstat) == SIGTRAP
       && check_stopped_by_watchpoint (child))
     ;
-  else if (WIFSTOPPED (wstat) && wstatus_maybe_breakpoint (wstat))
+  else if (WIFSTOPPED (wstat) && linux_wstatus_maybe_breakpoint (wstat))
     {
       if (check_stopped_by_breakpoint (child))
 	have_stop_pc = 1;
@@ -2739,7 +2726,8 @@ linux_wait_1 (ptid_t ptid,
      any that GDB specifically requested we ignore.  But never ignore
      SIGSTOP if we sent it ourselves, and do not ignore signals when
      stepping - they may require special handling to skip the signal
-     handler.  */
+     handler. Also never ignore signals that could be caused by a
+     breakpoint.  */
   /* FIXME drow/2002-06-09: Get signal numbers from the inferior's
      thread library?  */
   if (WIFSTOPPED (w)
@@ -2753,7 +2741,8 @@ linux_wait_1 (ptid_t ptid,
 #endif
 	  (pass_signals[gdb_signal_from_host (WSTOPSIG (w))]
 	   && !(WSTOPSIG (w) == SIGSTOP
-		&& current_thread->last_resume_kind == resume_stop))))
+		&& current_thread->last_resume_kind == resume_stop)
+	   && !linux_wstatus_maybe_breakpoint (w))))
     {
       siginfo_t info, *info_p;
 
diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 169188a..ed007bd 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -3070,9 +3070,11 @@ linux_nat_filter_event (int lwpid, int status)
 	}
 
       /* When using hardware single-step, we need to report every signal.
-	 Otherwise, signals in pass_mask may be short-circuited.  */
+	 Otherwise, signals in pass_mask may be short-circuited
+	 except signals that might be caused by a breakpoint.  */
       if (!lp->step
-	  && WSTOPSIG (status) && sigismember (&pass_mask, WSTOPSIG (status)))
+	  && WSTOPSIG (status) && sigismember (&pass_mask, WSTOPSIG (status))
+	  && !linux_wstatus_maybe_breakpoint (status))
 	{
 	  linux_resume_one_lwp (lp, lp->step, signo);
 	  if (debug_linux_nat)
diff --git a/gdb/nat/linux-ptrace.c b/gdb/nat/linux-ptrace.c
index 0ce258f..1c67819 100644
--- a/gdb/nat/linux-ptrace.c
+++ b/gdb/nat/linux-ptrace.c
@@ -621,3 +621,16 @@ linux_is_extended_waitstatus (int wstat)
 {
   return (linux_ptrace_get_extended_event (wstat) != 0);
 }
+
+/* Return true if the event in LP may be caused by breakpoint.  */
+
+int
+linux_wstatus_maybe_breakpoint (int wstat)
+{
+  return (WIFSTOPPED (wstat)
+	  && (WSTOPSIG (wstat) == SIGTRAP
+	      /* SIGILL and SIGSEGV are also treated as traps in case a
+		 breakpoint is inserted at the current PC.  */
+	      || WSTOPSIG (wstat) == SIGILL
+	      || WSTOPSIG (wstat) == SIGSEGV));
+}
diff --git a/gdb/nat/linux-ptrace.h b/gdb/nat/linux-ptrace.h
index 137b61a..c5b0f14 100644
--- a/gdb/nat/linux-ptrace.h
+++ b/gdb/nat/linux-ptrace.h
@@ -107,5 +107,6 @@ extern int linux_supports_tracesysgood (void);
 extern void linux_ptrace_set_additional_flags (int);
 extern int linux_ptrace_get_extended_event (int wstat);
 extern int linux_is_extended_waitstatus (int wstat);
+extern int linux_wstatus_maybe_breakpoint (int wstat);
 
 #endif /* COMMON_LINUX_PTRACE_H */
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 2fae080..a7f876e 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2015-02-19  Antoine Tremblay  <antoine.tremblay@ericsson.com>
+
+	PR breakpoints/16812
+	* gdb.base/catch-gdb-caused-signals.c: New file.
+	* gdb.base/catch-gdb-caused-signals.exp: New file.
+
 2015-02-18  Jose E. Marchesi  <jose.marchesi@oracle.com>
 
 	* configure: Regenerated.
diff --git a/gdb/testsuite/gdb.base/catch-gdb-caused-signals.c b/gdb/testsuite/gdb.base/catch-gdb-caused-signals.c
new file mode 100644
index 0000000..769858c
--- /dev/null
+++ b/gdb/testsuite/gdb.base/catch-gdb-caused-signals.c
@@ -0,0 +1,36 @@
+/* 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/>.  */
+
+/* This program is intended to be a simple dummy program for gdb to read.  */
+
+#include <unistd.h>
+#include <stdio.h>
+
+int
+main (void)
+{
+  int i = 0;
+
+  i++; /* set dprintf here */
+  return 0; /* set breakpoint here */
+}
+
+int
+return_one (void)
+{
+  return 1;
+}
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 0000000..8ba3be5
--- /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.*"
+}