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[v2] Fix gdbserver crash when doing ftrace commands after detach or process exit

Message ID 1464888683-31530-1-git-send-email-antoine.tremblay@ericsson.com
State New
Headers show

Commit Message

Antoine Tremblay June 2, 2016, 5:31 p.m. UTC
This patch is a v2 of: https://sourceware.org/ml/gdb-patches/2016-03/msg00560.html

For the test to be stable you need to apply this patch over: https://sourceware.org/ml/gdb-patches/2016-06/msg00040.html

I took the approach Yao suggested, protecting tracing commands from current_thread == NULL where needed.

Regarding Pedro's comment here: https://sourceware.org/ml/gdb-patches/2016-04/msg00652.html

I interpreted it as that GDBserver should bail out if current_thread == NULL, and that choosing another thread was not an option, that could be wrong, comments are welcome.

--
This patch fixes a gdbserver crash that is triggered by the following
sequence of events:

 - A process with the in-process agent loaded is debugged under gdbserver.
 - The process is detached or exits with or without stopping the trace before.
 - Commands tstatus, enable/disable, ftrace, tstop, quit with fast tracepoints
   are used.

Using either of tstatus or enable/disable ends up sending the qtstatus
packet to gdbserver.  During the handling of qtstatus, agent_loaded_p ()
returns true, even though the process that once had the agent loaded is
not present anymore.  We end up trying to read memory with
current_thread == NULL, causing a segfault here:

  gdb/gdbserver/linux-low.c:5560(linux_read_memory)[0x43583c]
  gdb/gdbserver/target.c:153(read_inferior_memory)[0x415d78]
  gdb/gdbserver/tracepoint.c:424(read_inferior_uinteger)[0x41c7fb]
  gdb/gdbserver/tracepoint.c:6288(upload_fast_traceframes)[0x425558]
  gdb/gdbserver/tracepoint.c:3645(cmd_qtstatus)[0x420dee]
  gdb/gdbserver/tracepoint.c:4239(handle_tracepoint_query)[0x4222ab]
  gdb/gdbserver/server.c:2543(handle_query)[0x411639]
  gdb/gdbserver/server.c:3910(process_serial_event)[0x413f39]
  gdb/gdbserver/server.c:4347(handle_serial_event)[0x415010]
  gdb/gdbserver/event-loop.c:428(handle_file_event)[0x41bed7]
  gdb/gdbserver/event-loop.c:184(process_event)[0x41b69e]
  gdb/gdbserver/event-loop.c:547(start_event_loop)[0x41c41d]
  gdb/gdbserver/server.c:3723(captured_main)[0x413a53]
  gdb/gdbserver/server.c:3802(main)[0x413c2f]

ftrace, tstop and quit need to be protected from current_thread == NULL in a
similar manner.

This patch adds a test called
gdb.trace/ftrace-commands-after-detach-or-exit.exp.

The test tests both in all-stop and non-stop, it also makes sure that a
gdb quit call works and that gdbserver is still alive after a test by
reconnecting to it after a quit.

No regression on x86-linux { native-gdbserver , native-extended-gdbserver }

gdb/gdbserver/ChangeLog:

	* tracepoint.c (cmd_qtdp): Check for current_thread == NULL.
	(cmd_qtenable_disable): Likewise.
	(cmd_qtstart): Likewise.
	(stop_tracing): Likewise.
	(cmd_qtstop): Likewise.
	(cmd_qtstatus): Likewise.

gdb/testsuite/ChangeLog:

	* gdb.trace/ftrace-commands-after-detach-or-exit.c: New file.
	* gdb.trace/ftrace-commands-after-detach-or-exit.exp: New test.
	* lib/gdbserver-support.exp (gdb_target_cmd): Add support for connection
	timed out error.
---
 gdb/gdbserver/tracepoint.c                         |  36 +++-
 .../ftrace-commands-after-detach-or-exit.c         |  25 +++
 .../ftrace-commands-after-detach-or-exit.exp       | 231 +++++++++++++++++++++
 gdb/testsuite/lib/gdbserver-support.exp            |   4 +
 4 files changed, 295 insertions(+), 1 deletion(-)
 create mode 100644 gdb/testsuite/gdb.trace/ftrace-commands-after-detach-or-exit.c
 create mode 100644 gdb/testsuite/gdb.trace/ftrace-commands-after-detach-or-exit.exp
diff mbox

Patch

diff --git a/gdb/gdbserver/tracepoint.c b/gdb/gdbserver/tracepoint.c
index c07e525..d80e0c98 100644
--- a/gdb/gdbserver/tracepoint.c
+++ b/gdb/gdbserver/tracepoint.c
@@ -2488,6 +2488,13 @@  cmd_qtdp (char *own_buf)
   char *actparm;
   char *packet = own_buf;
 
+  /* Can't do this command without a pid attached.  */
+  if (current_thread == NULL)
+    {
+      write_enn (packet);
+      return;
+    }
+
   packet += strlen ("QTDP:");
 
   /* A hyphen at the beginning marks a packet specifying actions for a
@@ -2752,6 +2759,13 @@  cmd_qtenable_disable (char *own_buf, int enable)
   ULONGEST num, addr;
   struct tracepoint *tp;
 
+  /* Can't do this command without a pid attached.  */
+  if (current_thread == NULL)
+    {
+      write_enn (packet);
+      return;
+    }
+
   packet += strlen (enable ? "QTEnable:" : "QTDisable:");
   packet = unpack_varlen_hex (packet, &num);
   ++packet; /* skip a colon */
@@ -3202,6 +3216,13 @@  cmd_qtstart (char *packet)
   struct tracepoint *tpoint, *prev_ftpoint, *prev_stpoint;
   CORE_ADDR tpptr = 0, prev_tpptr = 0;
 
+  /* Can't do this command without a pid attached.  */
+  if (current_thread == NULL)
+    {
+      write_enn (packet);
+      return;
+    }
+
   trace_debug ("Starting the trace");
 
   /* Pause all threads temporarily while we patch tracepoints.  */
@@ -3420,6 +3441,12 @@  stop_tracing (void)
       return;
     }
 
+  if (current_thread == NULL)
+    {
+      trace_debug ("Current thread null, can't stop threads");
+      return;
+    }
+
   trace_debug ("Stopping the trace");
 
   /* Pause all threads before removing fast jumps from memory,
@@ -3532,6 +3559,13 @@  flush_trace_buffer_handler (CORE_ADDR addr)
 static void
 cmd_qtstop (char *packet)
 {
+  /* Can't do this command without a pid attached.  */
+  if (current_thread == NULL)
+    {
+      write_enn (packet);
+      return;
+    }
+
   stop_tracing ();
   write_ok (packet);
 }
@@ -3650,7 +3684,7 @@  cmd_qtstatus (char *packet)
   trace_debug ("Returning trace status as %d, stop reason %s",
 	       tracing, tracing_stop_reason);
 
-  if (agent_loaded_p ())
+  if (current_thread != NULL && agent_loaded_p ())
     {
       pause_all (1);
 
diff --git a/gdb/testsuite/gdb.trace/ftrace-commands-after-detach-or-exit.c b/gdb/testsuite/gdb.trace/ftrace-commands-after-detach-or-exit.c
new file mode 100644
index 0000000..9f93b9b
--- /dev/null
+++ b/gdb/testsuite/gdb.trace/ftrace-commands-after-detach-or-exit.c
@@ -0,0 +1,25 @@ 
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2016 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 "trace-common.h"
+
+int
+main (void)
+{
+  FAST_TRACEPOINT_LABEL(set_point);
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.trace/ftrace-commands-after-detach-or-exit.exp b/gdb/testsuite/gdb.trace/ftrace-commands-after-detach-or-exit.exp
new file mode 100644
index 0000000..b68f9db
--- /dev/null
+++ b/gdb/testsuite/gdb.trace/ftrace-commands-after-detach-or-exit.exp
@@ -0,0 +1,231 @@ 
+# Copyright 2016 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/>.
+
+load_lib "trace-support.exp"
+
+standard_testfile
+set executable $testfile
+set expfile $testfile.exp
+
+# Some targets have leading underscores on assembly symbols.
+set options [list debug [gdb_target_symbol_prefix_flags]]
+
+# Check that the target supports trace.
+if { [gdb_compile "$srcdir/$subdir/$srcfile" $binfile executable $options] != "" } {
+    untested "Couldn't compile test program"
+    return -1
+}
+
+clean_restart ${testfile}
+
+if ![runto_main] {
+    fail "Can't run to main to check for trace support"
+    return -1
+}
+
+if $use_gdb_stub {
+    # This test is about testing commands after detaching from a process or
+    # after letting a process exit, so it doesn't make sense to run it if the
+    # target is stub-like.
+    unsupported "This test is not supported for GDB stub targets."
+    return -1
+}
+
+if ![gdb_target_supports_trace] {
+    unsupported "target does not support trace"
+    return -1
+}
+
+# Compile the test case with the in-process agent library.
+set libipa [get_in_proc_agent]
+set remote_libipa [gdb_load_shlib $libipa]
+
+lappend options shlib=$libipa
+
+if { [gdb_compile "$srcdir/$subdir/$srcfile" $binfile executable $options] != "" } {
+    untested "Couldn't compile test program with in-process agent library"
+    return -1
+}
+
+clean_restart ${testfile}
+
+if ![runto_main] {
+    fail "Can't run to main to check for trace support"
+    return -1
+}
+
+if { [gdb_test "info sharedlibrary" ".*${remote_libipa}.*" "IPA loaded"] != 0 } {
+    untested "Could not find IPA lib loaded"
+    return 1
+}
+
+# This test makes sure that gdbserver doesn't crash when doing a tstatus
+# after detaching from a previously traced process.
+proc test_tstatus_after_detach { } {
+    with_test_prefix "tstatus after detach" {
+	gdbserver_startup
+	global binfile decimal
+	gdb_test "ftrace set_point" "Fast tracepoint .*"
+	gdb_test_no_output "tstart"
+	gdb_test_no_output "tstop"
+	gdb_test "detach" "Detaching from program: $binfile, process $decimal"
+	gdb_test "tstatus" "Trace stopped by a tstop command ()\..*"
+	test_gdbserver_still_alive
+    }
+}
+
+# This test makes sure that gdbserver doesn't crash when doing a tstatus
+# after a previously traced process has exited.
+proc test_tstatus_after_exit { } {
+    with_test_prefix "tstatus after exit" {
+	gdbserver_startup
+	gdb_test "ftrace set_point" "Fast tracepoint .*"
+	gdb_test_no_output "tstart"
+	gdb_test_no_output "tstop"
+	gdb_continue_to_end
+	gdb_test "tstatus" "Trace stopped by a tstop command ()\..*"
+	test_gdbserver_still_alive
+    }
+}
+
+# This test makes sure that gdbserver doesn't crash when doing a enable
+# or disable after detaching from a previously traced process.
+proc test_enabledisable_after_detach { } {
+    with_test_prefix "enable/disable after detach" {
+	gdbserver_startup
+	global binfile decimal
+	gdb_test "ftrace set_point" "Fast tracepoint .*"
+	gdb_test_no_output "tstart"
+	gdb_test_no_output "tstop"
+	gdb_test "detach" "Detaching from program: $binfile, process $decimal"
+	gdb_test_no_output "disable"
+	gdb_test_no_output "enable"
+	test_gdbserver_still_alive
+    }
+}
+
+# This test makes sure that gdbserver doesn't crash when doing a enable
+# or disable after a previously traced process has exited.
+proc test_enabledisable_after_exit { } {
+    with_test_prefix "enable/disable after exit" {
+	gdbserver_startup
+	gdb_test "ftrace set_point" "Fast tracepoint .*"
+	gdb_test_no_output "tstart"
+	gdb_test_no_output "tstop"
+	gdb_continue_to_end
+	gdb_test_no_output "disable"
+	gdb_test_no_output "enable"
+	test_gdbserver_still_alive
+    }
+}
+
+# This test makes sure that gdbserver doesn't crash when doing an ftrace
+# after detaching from a previously traced process.
+proc test_ftrace_after_detach { } {
+    with_test_prefix "ftrace after detach" {
+	gdbserver_startup
+	global binfile decimal
+	gdb_test "ftrace set_point" "Fast tracepoint .*"
+	gdb_test_no_output "tstart"
+	gdb_test_no_output "set confirm off"
+	gdb_test "detach" "Detaching from program: $binfile, process $decimal"
+	gdb_test "ftrace set_point" ".*Fast tracepoint \[0-9]+ at.*"
+	test_gdbserver_still_alive
+    }
+}
+
+# This test makes sure that gdbserver doesn't crash when doing an ftrace
+# or disable after a previously traced process has exited.
+proc test_ftrace_after_exit { } {
+    with_test_prefix "ftrace after exit" {
+	gdbserver_startup
+	gdb_test "ftrace set_point" "Fast tracepoint .*"
+	gdb_test_no_output "tstart"
+	gdb_continue_to_end
+	gdb_test "ftrace set_point" ".*Target returns error code \'01\'\..*"
+	test_gdbserver_still_alive
+    }
+}
+
+# This test makes sure that gdbserver doesn't crash when doing an tstop
+# after detaching from a previously traced process.
+proc test_tstop_after_detach { } {
+    with_test_prefix "tstop after detach" {
+	gdbserver_startup
+	global binfile decimal
+	gdb_test "ftrace set_point" "Fast tracepoint .*"
+	gdb_test_no_output "tstart"
+	gdb_test_no_output "set confirm off"
+	gdb_test "detach" "Detaching from program: $binfile, process $decimal"
+	gdb_test "tstop" "Target returns error code \'01\'\..*"
+	test_gdbserver_still_alive
+    }
+}
+
+# This test makes sure that gdbserver doesn't crash when doing a tstop
+# after a previously traced process has exited.
+proc test_tstop_after_exit { } {
+    with_test_prefix "tstop after exit" {
+	gdbserver_startup
+	gdb_test "ftrace set_point" "Fast tracepoint .*"
+	gdb_test_no_output "tstart"
+	gdb_continue_to_end
+	gdb_test "tstop" "Target returns error code \'01\'\..*"
+	test_gdbserver_still_alive
+    }
+}
+
+# Initialize gdbserver in reconnectable mode to be able to test if it's still
+# alive after a full test (including gdb exit procedure)
+proc gdbserver_startup { } {
+    global executable gdbserver_reconnect_p
+    set gdbserver_reconnect_p 1
+    clean_restart ${executable}
+
+    if ![runto_main] {
+	fail "Can't run to main."
+	return -1
+    }
+}
+
+# Test if gdbserver is still alive by reconnecting to it and asking for a
+# trace status.
+proc test_gdbserver_still_alive { } {
+    gdb_test_no_output "set confirm off"
+    gdb_test "disconnect" "Ending remote debugging\\."
+    set test "reconnect to GDBserver"
+    if { [gdb_reconnect] == 0 } {
+	pass $test
+    } else {
+	fail $test
+	return 0
+    }
+}
+
+foreach nonstop { "off" "on" } {
+    save_vars { GDBFLAGS } {
+        append GDBFLAGS " -ex \"set non-stop $nonstop\""
+
+        with_test_prefix "non-stop=$nonstop" {
+	    test_tstatus_after_detach
+	    test_tstatus_after_exit
+	    test_enabledisable_after_detach
+	    test_enabledisable_after_exit
+	    test_ftrace_after_detach
+	    test_ftrace_after_exit
+	    test_tstop_after_detach
+	    test_tstop_after_exit
+        }
+    }
+}
diff --git a/gdb/testsuite/lib/gdbserver-support.exp b/gdb/testsuite/lib/gdbserver-support.exp
index 951afe5..1017889 100644
--- a/gdb/testsuite/lib/gdbserver-support.exp
+++ b/gdb/testsuite/lib/gdbserver-support.exp
@@ -90,6 +90,10 @@  proc gdb_target_cmd { targetname serialport } {
 	    -re "Timeout reading from remote system.*$gdb_prompt $" {
 		verbose "Got timeout error from gdb."
 	    }
+	    -re ".*Connection timed out.*$gdb_prompt $" {
+		verbose "Got timeout error from gdb."
+	    }
+
 	    -notransfer -re "Remote debugging using .*\r\n> $" {
 		# We got an unexpected prompt while creating the target.
 		# Leave it there for the test to diagnose.