Testcase for detaching while stepping over breakpoint
This adds a testcase that exercises detaching while GDB is stepping
over a breakpoint, in all combinations of:
- maint target non-stop off/on
- set non-stop on/off
- displaced stepping on/off
This exercises the bugs fixed in the previous 8 patches.
gdb/testsuite/ChangeLog:
* gdb.threads/detach-step-over.c: New file.
* gdb.threads/detach-step-over.exp: New file.
diff --git a/gdb/testsuite/gdb.threads/detach-step-over.c b/gdb/testsuite/gdb.threads/detach-step-over.c
new file mode 100644
index 0000000..13db9f6
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/detach-step-over.c
@@ -0,0 +1,112 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2021 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/>. */
+
+#define _GNU_SOURCE
+#include <assert.h>
+#include <pthread.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#include <signal.h>
+
+/* Number of threads we'll create. */
+int n_threads = 10;
+
+int mypid;
+
+static void
+setup_done (void)
+{
+}
+
+/* Entry point for threads. Loops forever. */
+
+void *
+thread_func (void *arg)
+{
+ /* Avoid setting the breakpoint at an instruction that wouldn't
+ require a fixup phase, like a branch/jump. In such a case, even
+ if GDB manages to detach the inferior with an incomplete
+ displaced step, GDB inferior may still not crash. A breakpoint
+ at a line that increments a variable is good bet that we end up
+ setting a breakpoint at an instruction that will require a fixup
+ phase to move the PC from the scratch pad to the instruction
+ after the breakpoint. */
+ volatile unsigned counter = 0;
+
+ while (1)
+ {
+ counter++; /* Set breakpoint here. */
+ counter++;
+ counter++;
+ }
+
+ return NULL;
+}
+
+/* Allow for as much timeout as DejaGnu wants, plus a bit of
+ slack. */
+#define SECONDS (TIMEOUT + 20)
+
+/* We'll exit after this many seconds. */
+unsigned int seconds_left = SECONDS;
+
+/* GDB sets this whenever it's about to start a new detach/attach
+ sequence. We react by resetting the seconds-left counter. */
+volatile int again = 0;
+
+int
+main (int argc, char **argv)
+{
+ int i;
+
+ signal (SIGUSR1, SIG_IGN);
+
+ mypid = getpid ();
+ setup_done ();
+
+ if (argc > 1)
+ n_threads = atoi (argv[1]);
+
+ /* Spawn the test threads. */
+ for (i = 0; i < n_threads; ++i)
+ {
+ pthread_t child;
+ int rc;
+
+ rc = pthread_create (&child, NULL, thread_func, NULL);
+ assert (rc == 0);
+ }
+
+ /* Exit after a while if GDB is gone/crashes. But wait long enough
+ for one attach/detach sequence done by the .exp file. */
+ while (--seconds_left > 0)
+ {
+ sleep (1);
+
+ if (again)
+ {
+ /* GDB should be reattaching soon. Restart the timer. */
+ again = 0;
+ seconds_left = SECONDS;
+ }
+ }
+
+ printf ("timeout, exiting\n");
+ return 0;
+}
diff --git a/gdb/testsuite/gdb.threads/detach-step-over.exp b/gdb/testsuite/gdb.threads/detach-step-over.exp
new file mode 100644
index 0000000..3298c5b
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/detach-step-over.exp
@@ -0,0 +1,290 @@
+# Copyright 2021 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 detaching from a process that is running and has threads
+# constantly hitting a breakpoint and stepping over it, in all
+# combinations of:
+#
+# - maint target non-stop off/on
+# - set non-stop on/off
+# - displaced stepping on/off
+#
+# This stresses the edge cases of detaching while a displaced step or
+# an in-line step over are in progress.
+#
+# A fail mode is that the inferior process dies after being detached.
+# This can happen because e.g.:
+#
+# - GDB leaves a breakpoint installed behind, or
+#
+# - GDB leaves a thread running in the displaced step scratch buffer.
+# With no debugger around to run the finish step, the thread runs
+# off of the scratch buffer, with undefined results.
+#
+# To exercise this, the testcase reattaches to the process shortly
+# after detaching, ensuring the process is still alive and well.
+#
+# In addition, since GDB may pause threads of all processes for
+# stepping over a breakpoint, it needs to re-resume all threads if it
+# detaches from the process that was just stepping over the
+# breakpoint. To ensure that, the testcase actually runs a second
+# process at the same time as the one that is used to test detaching.
+# After the first process is detached, the testcase sends a SIGUSR1 to
+# the second process. If threads failed to be resumed, then the
+# SIGUSR1 is never reported to the user, resulting in timeout. The
+# threads of this second process will also be constantly stepping over
+# a breakpoint, which has helped with exposing further corner case
+# bugs.
+
+if {![can_spawn_for_attach]} {
+ return 0
+}
+
+standard_testfile
+
+set bp_lineno [gdb_get_line_number "Set breakpoint here"]
+
+# The test proper. See description above.
+proc test {condition_eval target_non_stop non_stop displaced} {
+ global binfile srcfile
+ global gdb_prompt
+ global decimal
+ global bp_lineno
+ global GDBFLAGS
+
+ # Number of threads started by the program.
+ set n_threads 10
+
+ save_vars { GDBFLAGS } {
+ append GDBFLAGS " -ex \"maint set target-non-stop $target_non_stop\""
+ append GDBFLAGS " -ex \"set non-stop $non_stop\""
+ append GDBFLAGS " -ex \"set displaced $displaced\""
+ append GDBFLAGS " -ex \"set schedule-multiple on\""
+ clean_restart $binfile
+ }
+
+ set test_spawn_id [spawn_wait_for_attach $binfile]
+ set testpid [spawn_id_get_pid $test_spawn_id]
+
+ set any "\[^\r\n\]*"
+
+ gdb_test "add-inferior" "Added inferior 2.*"
+ gdb_test "inferior 2" "Switching to .*"
+
+ gdb_load $binfile
+ if ![runto setup_done] then {
+ fail "can't run to setup_done"
+ kill_wait_spawned_process $test_spawn_id
+ return
+ }
+
+ gdb_test_no_output "set breakpoint condition-evaluation $condition_eval"
+
+ # Get the PID of the test process.
+ set pid_inf2 ""
+ gdb_test_multiple "p mypid" "get pid of inferior 2" {
+ -re " = ($decimal)\r\n$gdb_prompt $" {
+ set pid_inf2 $expect_out(1,string)
+ pass $gdb_test_name
+ }
+ }
+
+ set attempts 3
+ for {set attempt 1} { $attempt <= $attempts } { incr attempt } {
+ with_test_prefix "iter $attempt" {
+ gdb_test "inferior 1" "Switching to .*"
+
+ set attached 0
+ set eperm 0
+ set test "attach"
+ gdb_test_multiple "attach $testpid" $test {
+ -re "new threads in iteration" {
+ # Seen when "set debug libthread_db" is on.
+ exp_continue
+ }
+ -re "is a zombie - the process has already terminated.*$gdb_prompt " {
+ fail $gdb_test_name
+ }
+ -re "Unable to attach: .*$gdb_prompt " {
+ fail $gdb_test_name
+ }
+ -re "Attaching to program.*process $testpid.*$gdb_prompt " {
+ pass $test
+ set attached 1
+ }
+ }
+
+ if {!$attached} {
+ kill_wait_spawned_process $test_spawn_id
+ return
+ }
+
+ if {$non_stop} {
+ # In non-stop, we will see one stop per thread after
+ # the prompt.
+ set stops 0
+ set tid_re "$::decimal\.$::decimal"
+ set test "seen all stops"
+ for {set thread 1} { $thread <= $n_threads } { incr thread } {
+ if {[gdb_test_multiple "" $test {
+ -re "Thread ${tid_re} ${any} stopped" {
+ incr stops
+ }
+ }] != 0} {
+ break
+ }
+ }
+
+ # This we haven't seen all stops, then the
+ # gdb_test_multiple in the loop above will have
+ # already issued a FAIL.
+ if {$stops != $n_threads} {
+ kill_wait_spawned_process $test_spawn_id
+ return
+ }
+ pass $test
+ }
+
+ # Set threads stepping over a breakpoint continuously.
+ gdb_test "break $srcfile:$bp_lineno if 0" "Breakpoint.*" \
+ "break LOC if 0"
+
+ if {$attempt < $attempts} {
+ # Kick the time out timer for another round.
+ gdb_test "print again = 1" " = 1" "reset timer in the inferior"
+ # Show the time we had left in the logs, in case
+ # something goes wrong.
+ gdb_test "print seconds_left" " = .*"
+ }
+
+ if {$non_stop} {
+ set cont_cmd "continue -a &"
+ } else {
+ set cont_cmd "continue &"
+ }
+
+ set cont_cmd_re [string_to_regexp $cont_cmd]
+ gdb_test_multiple $cont_cmd "" {
+ -re "^$cont_cmd_re\r\nContinuing\.\r\n$gdb_prompt " {
+ pass $gdb_test_name
+ }
+ }
+
+ # Wait a bit, to give time for the threads to hit the
+ # breakpoint.
+ sleep 1
+
+ set running_count 0
+ set interrupted 0
+ gdb_test_multiple "info threads" "all threads running" {
+ -re "\\(running\\)" {
+ incr running_count
+ exp_continue
+ }
+ -re "Cannot execute this command while the target is running.*$gdb_prompt $" {
+ # Testing against a remote server that doesn't do
+ # non-stop mode. Explicitly interrupt. This
+ # doesn't test the same code paths in GDB, but
+ # it's still something.
+ set interrupted 1
+ gdb_test_multiple "interrupt" "" {
+ -re "$gdb_prompt " {
+ gdb_test_multiple "" $gdb_test_name {
+ -re "received signal SIGINT, Interrupt" {
+ pass $gdb_test_name
+ }
+ }
+ }
+ }
+ }
+ -re "$gdb_prompt $" {
+ gdb_assert {$running_count == ($n_threads + 1) * 2} $gdb_test_name
+ }
+ }
+
+ gdb_test "detach" "Detaching from.*"
+
+ if {!$interrupted} {
+ # Now test whether inferior 2's thread were really left
+ # running. Currently an inline step-over stops all
+ # threads of all processes. If detach aborts such a step
+ # over, then threads of other inferiors should be
+ # re-resumed. Test for that by sending a signal to
+ # inferior 2.
+ remote_exec target "kill -SIGUSR1 ${pid_inf2}"
+
+ gdb_test_multiple "" "stop with SIGUSR1" {
+ -re "received signal SIGUSR1" {
+ pass $gdb_test_name
+ }
+ }
+ }
+
+ delete_breakpoints
+ }
+ }
+ kill_wait_spawned_process $test_spawn_id
+}
+
+# The test program exits after a while, in case GDB crashes. Make it
+# wait at least as long as we may wait before declaring a time out
+# failure.
+set options { "additional_flags=-DTIMEOUT=$timeout" debug pthreads }
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile $options] == -1} {
+ return -1
+}
+
+if ![runto_main] {
+ return -1
+}
+
+# Probe support for "set breakpoint condition-evaluation target".
+# This setting influences who steps over the breakpoint, the (remote)
+# target (e.g. gdbserver) or gdb, thus exposing issues on either the
+# target or gdb.
+set supports_condition_eval_target 1
+set cmd "set breakpoint condition-evaluation target"
+gdb_test_multiple $cmd "probe condition-evaluation target support" {
+ -re "warning: Target does not support breakpoint condition evaluation.\r\nUsing host evaluation mode instead.\r\n$gdb_prompt $" {
+ # Target doesn't support breakpoint condition evaluation on
+ # its side.
+ set supports_condition_eval_target 0
+ pass $gdb_test_name
+ }
+ -re "^$cmd\r\n$gdb_prompt $" {
+ pass $gdb_test_name
+ }
+}
+
+foreach_with_prefix breakpoint-condition-evaluation {"host" "target"} {
+ if {!$supports_condition_eval_target && ${breakpoint-condition-evaluation} == "target"} {
+ continue
+ }
+
+ foreach_with_prefix target-non-stop {"off" "on"} {
+ foreach_with_prefix non-stop {"off" "on"} {
+ if {${non-stop} && !${target-non-stop}} {
+ # "set non-stop" overrides "maint set
+ # target-non-stop", no use testing this combination.
+ continue
+ }
+
+ foreach_with_prefix displaced {"off" "auto"} {
+ test ${breakpoint-condition-evaluation} ${target-non-stop} ${non-stop} ${displaced}
+ }
+ }
+ }
+}
