old-cross-binutils/gdb/testsuite/gdb.threads/stepi-random-signal.exp

110 lines
3 KiB
Text
Raw Normal View History

# Copyright 2013-2016 Free Software Foundation, Inc.
[gdb/16062] stepi sometimes doesn't make progress I noticed something odd while doing "stepi" over a fork syscall: ... (gdb) set disassemble-next-line on ... (gdb) si 0x000000323d4ba7c2 131 pid = ARCH_FORK (); 0x000000323d4ba7a4 <__libc_fork+132>: 64 4c 8b 04 25 10 00 00 00 mov %fs:0x10,%r8 0x000000323d4ba7ad <__libc_fork+141>: 31 d2 xor %edx,%edx 0x000000323d4ba7af <__libc_fork+143>: 4d 8d 90 d0 02 00 00 lea 0x2d0(%r8),%r10 0x000000323d4ba7b6 <__libc_fork+150>: 31 f6 xor %esi,%esi 0x000000323d4ba7b8 <__libc_fork+152>: bf 11 00 20 01 mov $0x1200011,%edi 0x000000323d4ba7bd <__libc_fork+157>: b8 38 00 00 00 mov $0x38,%eax => 0x000000323d4ba7c2 <__libc_fork+162>: 0f 05 syscall 0x000000323d4ba7c4 <__libc_fork+164>: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax 0x000000323d4ba7ca <__libc_fork+170>: 0f 87 2b 01 00 00 ja 0x323d4ba8fb <__libc_fork+475> (gdb) si 0x000000323d4ba7c4 131 pid = ARCH_FORK (); 0x000000323d4ba7a4 <__libc_fork+132>: 64 4c 8b 04 25 10 00 00 00 mov %fs:0x10,%r8 0x000000323d4ba7ad <__libc_fork+141>: 31 d2 xor %edx,%edx 0x000000323d4ba7af <__libc_fork+143>: 4d 8d 90 d0 02 00 00 lea 0x2d0(%r8),%r10 0x000000323d4ba7b6 <__libc_fork+150>: 31 f6 xor %esi,%esi 0x000000323d4ba7b8 <__libc_fork+152>: bf 11 00 20 01 mov $0x1200011,%edi 0x000000323d4ba7bd <__libc_fork+157>: b8 38 00 00 00 mov $0x38,%eax 0x000000323d4ba7c2 <__libc_fork+162>: 0f 05 syscall => 0x000000323d4ba7c4 <__libc_fork+164>: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax 0x000000323d4ba7ca <__libc_fork+170>: 0f 87 2b 01 00 00 ja 0x323d4ba8fb <__libc_fork+475> (gdb) si 0x000000323d4ba7c4 131 pid = ARCH_FORK (); 0x000000323d4ba7a4 <__libc_fork+132>: 64 4c 8b 04 25 10 00 00 00 mov %fs:0x10,%r8 0x000000323d4ba7ad <__libc_fork+141>: 31 d2 xor %edx,%edx 0x000000323d4ba7af <__libc_fork+143>: 4d 8d 90 d0 02 00 00 lea 0x2d0(%r8),%r10 0x000000323d4ba7b6 <__libc_fork+150>: 31 f6 xor %esi,%esi 0x000000323d4ba7b8 <__libc_fork+152>: bf 11 00 20 01 mov $0x1200011,%edi 0x000000323d4ba7bd <__libc_fork+157>: b8 38 00 00 00 mov $0x38,%eax 0x000000323d4ba7c2 <__libc_fork+162>: 0f 05 syscall => 0x000000323d4ba7c4 <__libc_fork+164>: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax 0x000000323d4ba7ca <__libc_fork+170>: 0f 87 2b 01 00 00 ja 0x323d4ba8fb <__libc_fork+475> (gdb) si 0x000000323d4ba7ca 131 pid = ARCH_FORK (); 0x000000323d4ba7a4 <__libc_fork+132>: 64 4c 8b 04 25 10 00 00 00 mov %fs:0x10,%r8 0x000000323d4ba7ad <__libc_fork+141>: 31 d2 xor %edx,%edx 0x000000323d4ba7af <__libc_fork+143>: 4d 8d 90 d0 02 00 00 lea 0x2d0(%r8),%r10 0x000000323d4ba7b6 <__libc_fork+150>: 31 f6 xor %esi,%esi 0x000000323d4ba7b8 <__libc_fork+152>: bf 11 00 20 01 mov $0x1200011,%edi 0x000000323d4ba7bd <__libc_fork+157>: b8 38 00 00 00 mov $0x38,%eax 0x000000323d4ba7c2 <__libc_fork+162>: 0f 05 syscall 0x000000323d4ba7c4 <__libc_fork+164>: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax => 0x000000323d4ba7ca <__libc_fork+170>: 0f 87 2b 01 00 00 ja 0x323d4ba8fb <__libc_fork+475> Notice how the third "si" didn't actually make progress. Turning on infrun and lin-lwp debug, we see: (gdb) infrun: clear_proceed_status_thread (process 5252) infrun: proceed (addr=0xffffffffffffffff, signal=144, step=1) infrun: resume (step=1, signal=0), trap_expected=0, current thread [process 5252] at 0x323d4ba7c4 LLR: Preparing to step process 5252, 0, inferior_ptid process 5252 RC: Not resuming sibling process 5252 (not stopped) LLR: PTRACE_SINGLESTEP process 5252, 0 (resume event thread) sigchld infrun: wait_for_inferior () linux_nat_wait: [process -1], [] LLW: enter LNW: waitpid(-1, ...) returned 5252, No child processes LLW: waitpid 5252 received Child exited (stopped) LLW: Candidate event Child exited (stopped) in process 5252. SEL: Select single-step process 5252 LLW: exit infrun: target_wait (-1, status) = infrun: 5252 [process 5252], infrun: status->kind = stopped, signal = SIGCHLD infrun: infwait_normal_state infrun: TARGET_WAITKIND_STOPPED infrun: stop_pc = 0x323d4ba7c4 infrun: random signal 20 infrun: stepi/nexti infrun: stop_stepping So the inferior got a SIGCHLD (because the fork child exited while we're doing 'si'), and since that signal is set to "nostop noprint pass" (by default), it's considered a random signal, so it should not cause a stop. But, it resulted in an immediate a stop_stepping call anyway. So the single-step never really finished. This is a regression caused by: [[PATCH] Do not respawn signals, take 2.] https://sourceware.org/ml/gdb-patches/2012-06/msg00702.html Specifically, caused by this change (as mentioned in the "the lost step issue first" part of that mail): diff --git a/gdb/infrun.c b/gdb/infrun.c index 53db335..3e8dbc8 100644 --- a/gdb/infrun.c +++ b/gdb/infrun.c @@ -4363,10 +4363,8 @@ process_event_stop_test: (leaving the inferior at the step-resume-breakpoint without actually executing it). Either way continue until the breakpoint is really hit. */ - keep_going (ecs); - return; } - + else /* Handle cases caused by hitting a breakpoint. */ { That made GDB fall through to the > /* In all-stop mode, if we're currently stepping but have stopped in > some other thread, we need to switch back to the stepped thread. */ > if (!non_stop) part. However, if we don't have a stepped thread to get back to, we'll now also fall through to all the "stepping" tests. For line stepping, that'll turn out okay, as we'll just end up realizing the thread is still in the stepping range, and needs to be re-stepped. However, for stepi/nexti, we'll reach: if (ecs->event_thread->control.step_range_end == 1) { /* It is stepi or nexti. We always want to stop stepping after one instruction. */ if (debug_infrun) fprintf_unfiltered (gdb_stdlog, "infrun: stepi/nexti\n"); ecs->event_thread->control.stop_step = 1; print_end_stepping_range_reason (); stop_stepping (ecs); return; } and stop, even though the thread actually made no progress. The fix is to restore the keep_going call, but put it after the "switch back to the stepped thread" code, and before the stepping tests. Tested on x86_64 Fedora 17, native and gdbserver. New test included. gdb/ 2013-10-18 Pedro Alves <palves@redhat.com> PR gdb/16062 * infrun.c (handle_inferior_event): Keep going if we got a random signal we should not stop for, instead of falling through to the step tests. gdb/testsuite/ 2013-10-18 Pedro Alves <palves@redhat.com> PR gdb/16062 * gdb.threads/stepi-random-signal.c: New file. * gdb.threads/stepi-random-signal.exp: New file.
2013-10-18 14:28:34 +00:00
# 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/>.
standard_testfile
set executable ${testfile}
if { [gdb_compile_pthreads \
"${srcdir}/${subdir}/${srcfile}" \
"${binfile}" \
executable {debug}] != "" } {
untested "Couldn't compile test program."
return -1
}
clean_restart $executable
# Start the second thread.
if ![runto start] {
return -1
}
# Go back to the main thread, and leave it in the loop, where we're
# reasonably sure we don't have 'conditional jmp $pc'-like
# instructions. We wouldn't be able to detect whether a stepi makes
# progress over those.
gdb_test_no_output "set scheduler-locking on"
gdb_test "thread 1" "Switching to .*"
gdb_breakpoint $srcfile:[gdb_get_line_number "set break 2 here"]
gdb_continue_to_breakpoint "loop" ".* set break 2 here .*"
# Now back to thread 2, and let it queue a signal in thread 1.
gdb_test "thread 2" "Switching to .*"
gdb_breakpoint $srcfile:[gdb_get_line_number "set break here"]
gdb_continue_to_breakpoint "after pthread_kill" ".* set break here .*"
# We're now ready to stepi thread 1. It should immediately dequeue
# the signal.
gdb_test "thread 1" "Switching to .*" "thread 1 again"
# No longer need these.
delete_breakpoints
# Turn on infrun debugging, so we can tell whether the signal is
# really dequeued and that GDB sees it.
gdb_test_no_output "set debug infrun 1"
Fix gdb.threads/stepi-random-signal.exp on software single-step targets. Currently on software single-step Linux targets we get: (gdb) PASS: gdb.threads/stepi-random-signal.exp: before stepi: get hexadecimal valueof "$pc" stepi infrun: clear_proceed_status_thread (Thread 0x7ffff7fca700 (LWP 7073)) infrun: clear_proceed_status_thread (Thread 0x7ffff7fcb740 (LWP 7069)) infrun: proceed (addr=0xffffffffffffffff, signal=GDB_SIGNAL_DEFAULT, step=1) infrun: resume (step=1, signal=GDB_SIGNAL_0), trap_expected=0, current thread [Thread 0x7ffff7fcb740 (LWP 7069)] at 0x400700 infrun: wait_for_inferior () infrun: target_wait (-1, status) = infrun: 7069 [Thread 0x7ffff7fcb740 (LWP 7069)], infrun: status->kind = stopped, signal = GDB_SIGNAL_TRAP infrun: infwait_normal_state infrun: TARGET_WAITKIND_STOPPED infrun: stop_pc = 0x400704 infrun: software single step trap for Thread 0x7ffff7fcb740 (LWP 7069) infrun: stepi/nexti infrun: stop_stepping 44 while (counter != 0) (gdb) FAIL: gdb.threads/stepi-random-signal.exp: stepi (no random signal) Vs hardware-step targets: (gdb) PASS: gdb.threads/stepi-random-signal.exp: before stepi: get hexadecimal valueof "$pc" stepi infrun: clear_proceed_status_thread (Thread 0x7ffff7fca700 (LWP 9565)) infrun: clear_proceed_status_thread (Thread 0x7ffff7fcb740 (LWP 9561)) infrun: proceed (addr=0xffffffffffffffff, signal=GDB_SIGNAL_DEFAULT, step=1) infrun: resume (step=1, signal=GDB_SIGNAL_0), trap_expected=0, current thread [Thread 0x7ffff7fcb740 (LWP 9561)] at 0x400700 infrun: wait_for_inferior () infrun: target_wait (-1, status) = infrun: 9561 [Thread 0x7ffff7fcb740 (LWP 9561)], infrun: status->kind = stopped, signal = GDB_SIGNAL_CHLD infrun: infwait_normal_state infrun: TARGET_WAITKIND_STOPPED infrun: stop_pc = 0x400700 infrun: random signal (GDB_SIGNAL_CHLD) infrun: random signal, keep going infrun: resume (step=1, signal=GDB_SIGNAL_CHLD), trap_expected=0, current thread [Thread 0x7ffff7fcb740 (LWP 9561)] at 0x400700 infrun: prepare_to_wait infrun: target_wait (-1, status) = infrun: 9561 [Thread 0x7ffff7fcb740 (LWP 9561)], infrun: status->kind = stopped, signal = GDB_SIGNAL_TRAP infrun: infwait_normal_state infrun: TARGET_WAITKIND_STOPPED infrun: stop_pc = 0x400704 infrun: stepi/nexti infrun: stop_stepping 44 while (counter != 0) (gdb) PASS: gdb.threads/stepi-random-signal.exp: stepi The test turns on infrun debug, does a stepi while a SIGCHLD is pending, and checks whether the "random signal" paths in infrun.c are taken. On the software single-step variant above, those paths were not taken. This is a test bug. The Linux backend short-circuits reporting signals that are set to pass/nostop/noprint. But _only_ if the thread is _not_ single-stepping. So on hardware-step targets, even though the signal is set to pass/nostop/noprint by default, the thread is indeed told to single-step, and so the core sees the signal. On the other hand, on software single-step architectures, the backend never actually gets a single-step request (steps are emulated by setting a breakpoint at the next pc, and then the target told to continue, not step). So the short-circuiting code triggers and the core doesn't see the signal. The fix is to make the test be sure the target doesn't bypass reporting the signal to the core. Tested on x86_64 Fedora 17, both with and without a series that implements software single-step for x86_64. gdb/testsuite/ 2014-02-07 Pedro Alves <palves@redhat.com> * gdb.threads/stepi-random-signal.exp: Set SIGCHLD to print.
2013-10-30 15:07:07 +00:00
# Make sure the target backend reports the signal to GDB core. Some
# backends (like Linux) skip reporting a signal if set to
# pass/nostop/noprint, resuming the thread immediately instead.
gdb_test "handle SIGCHLD print"
[gdb/16062] stepi sometimes doesn't make progress I noticed something odd while doing "stepi" over a fork syscall: ... (gdb) set disassemble-next-line on ... (gdb) si 0x000000323d4ba7c2 131 pid = ARCH_FORK (); 0x000000323d4ba7a4 <__libc_fork+132>: 64 4c 8b 04 25 10 00 00 00 mov %fs:0x10,%r8 0x000000323d4ba7ad <__libc_fork+141>: 31 d2 xor %edx,%edx 0x000000323d4ba7af <__libc_fork+143>: 4d 8d 90 d0 02 00 00 lea 0x2d0(%r8),%r10 0x000000323d4ba7b6 <__libc_fork+150>: 31 f6 xor %esi,%esi 0x000000323d4ba7b8 <__libc_fork+152>: bf 11 00 20 01 mov $0x1200011,%edi 0x000000323d4ba7bd <__libc_fork+157>: b8 38 00 00 00 mov $0x38,%eax => 0x000000323d4ba7c2 <__libc_fork+162>: 0f 05 syscall 0x000000323d4ba7c4 <__libc_fork+164>: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax 0x000000323d4ba7ca <__libc_fork+170>: 0f 87 2b 01 00 00 ja 0x323d4ba8fb <__libc_fork+475> (gdb) si 0x000000323d4ba7c4 131 pid = ARCH_FORK (); 0x000000323d4ba7a4 <__libc_fork+132>: 64 4c 8b 04 25 10 00 00 00 mov %fs:0x10,%r8 0x000000323d4ba7ad <__libc_fork+141>: 31 d2 xor %edx,%edx 0x000000323d4ba7af <__libc_fork+143>: 4d 8d 90 d0 02 00 00 lea 0x2d0(%r8),%r10 0x000000323d4ba7b6 <__libc_fork+150>: 31 f6 xor %esi,%esi 0x000000323d4ba7b8 <__libc_fork+152>: bf 11 00 20 01 mov $0x1200011,%edi 0x000000323d4ba7bd <__libc_fork+157>: b8 38 00 00 00 mov $0x38,%eax 0x000000323d4ba7c2 <__libc_fork+162>: 0f 05 syscall => 0x000000323d4ba7c4 <__libc_fork+164>: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax 0x000000323d4ba7ca <__libc_fork+170>: 0f 87 2b 01 00 00 ja 0x323d4ba8fb <__libc_fork+475> (gdb) si 0x000000323d4ba7c4 131 pid = ARCH_FORK (); 0x000000323d4ba7a4 <__libc_fork+132>: 64 4c 8b 04 25 10 00 00 00 mov %fs:0x10,%r8 0x000000323d4ba7ad <__libc_fork+141>: 31 d2 xor %edx,%edx 0x000000323d4ba7af <__libc_fork+143>: 4d 8d 90 d0 02 00 00 lea 0x2d0(%r8),%r10 0x000000323d4ba7b6 <__libc_fork+150>: 31 f6 xor %esi,%esi 0x000000323d4ba7b8 <__libc_fork+152>: bf 11 00 20 01 mov $0x1200011,%edi 0x000000323d4ba7bd <__libc_fork+157>: b8 38 00 00 00 mov $0x38,%eax 0x000000323d4ba7c2 <__libc_fork+162>: 0f 05 syscall => 0x000000323d4ba7c4 <__libc_fork+164>: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax 0x000000323d4ba7ca <__libc_fork+170>: 0f 87 2b 01 00 00 ja 0x323d4ba8fb <__libc_fork+475> (gdb) si 0x000000323d4ba7ca 131 pid = ARCH_FORK (); 0x000000323d4ba7a4 <__libc_fork+132>: 64 4c 8b 04 25 10 00 00 00 mov %fs:0x10,%r8 0x000000323d4ba7ad <__libc_fork+141>: 31 d2 xor %edx,%edx 0x000000323d4ba7af <__libc_fork+143>: 4d 8d 90 d0 02 00 00 lea 0x2d0(%r8),%r10 0x000000323d4ba7b6 <__libc_fork+150>: 31 f6 xor %esi,%esi 0x000000323d4ba7b8 <__libc_fork+152>: bf 11 00 20 01 mov $0x1200011,%edi 0x000000323d4ba7bd <__libc_fork+157>: b8 38 00 00 00 mov $0x38,%eax 0x000000323d4ba7c2 <__libc_fork+162>: 0f 05 syscall 0x000000323d4ba7c4 <__libc_fork+164>: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax => 0x000000323d4ba7ca <__libc_fork+170>: 0f 87 2b 01 00 00 ja 0x323d4ba8fb <__libc_fork+475> Notice how the third "si" didn't actually make progress. Turning on infrun and lin-lwp debug, we see: (gdb) infrun: clear_proceed_status_thread (process 5252) infrun: proceed (addr=0xffffffffffffffff, signal=144, step=1) infrun: resume (step=1, signal=0), trap_expected=0, current thread [process 5252] at 0x323d4ba7c4 LLR: Preparing to step process 5252, 0, inferior_ptid process 5252 RC: Not resuming sibling process 5252 (not stopped) LLR: PTRACE_SINGLESTEP process 5252, 0 (resume event thread) sigchld infrun: wait_for_inferior () linux_nat_wait: [process -1], [] LLW: enter LNW: waitpid(-1, ...) returned 5252, No child processes LLW: waitpid 5252 received Child exited (stopped) LLW: Candidate event Child exited (stopped) in process 5252. SEL: Select single-step process 5252 LLW: exit infrun: target_wait (-1, status) = infrun: 5252 [process 5252], infrun: status->kind = stopped, signal = SIGCHLD infrun: infwait_normal_state infrun: TARGET_WAITKIND_STOPPED infrun: stop_pc = 0x323d4ba7c4 infrun: random signal 20 infrun: stepi/nexti infrun: stop_stepping So the inferior got a SIGCHLD (because the fork child exited while we're doing 'si'), and since that signal is set to "nostop noprint pass" (by default), it's considered a random signal, so it should not cause a stop. But, it resulted in an immediate a stop_stepping call anyway. So the single-step never really finished. This is a regression caused by: [[PATCH] Do not respawn signals, take 2.] https://sourceware.org/ml/gdb-patches/2012-06/msg00702.html Specifically, caused by this change (as mentioned in the "the lost step issue first" part of that mail): diff --git a/gdb/infrun.c b/gdb/infrun.c index 53db335..3e8dbc8 100644 --- a/gdb/infrun.c +++ b/gdb/infrun.c @@ -4363,10 +4363,8 @@ process_event_stop_test: (leaving the inferior at the step-resume-breakpoint without actually executing it). Either way continue until the breakpoint is really hit. */ - keep_going (ecs); - return; } - + else /* Handle cases caused by hitting a breakpoint. */ { That made GDB fall through to the > /* In all-stop mode, if we're currently stepping but have stopped in > some other thread, we need to switch back to the stepped thread. */ > if (!non_stop) part. However, if we don't have a stepped thread to get back to, we'll now also fall through to all the "stepping" tests. For line stepping, that'll turn out okay, as we'll just end up realizing the thread is still in the stepping range, and needs to be re-stepped. However, for stepi/nexti, we'll reach: if (ecs->event_thread->control.step_range_end == 1) { /* It is stepi or nexti. We always want to stop stepping after one instruction. */ if (debug_infrun) fprintf_unfiltered (gdb_stdlog, "infrun: stepi/nexti\n"); ecs->event_thread->control.stop_step = 1; print_end_stepping_range_reason (); stop_stepping (ecs); return; } and stop, even though the thread actually made no progress. The fix is to restore the keep_going call, but put it after the "switch back to the stepped thread" code, and before the stepping tests. Tested on x86_64 Fedora 17, native and gdbserver. New test included. gdb/ 2013-10-18 Pedro Alves <palves@redhat.com> PR gdb/16062 * infrun.c (handle_inferior_event): Keep going if we got a random signal we should not stop for, instead of falling through to the step tests. gdb/testsuite/ 2013-10-18 Pedro Alves <palves@redhat.com> PR gdb/16062 * gdb.threads/stepi-random-signal.c: New file. * gdb.threads/stepi-random-signal.exp: New file.
2013-10-18 14:28:34 +00:00
# Helper to extract the current PC. PREFIX is used to make each call
# have its own unique test name.
proc get_pc { prefix } {
with_test_prefix "$prefix" {
return [get_hexadecimal_valueof "\$pc" ""]
}
}
set prev_addr [get_pc "before stepi"]
if {$prev_addr == ""} {
return
}
# True if we saw the infrun path we want to test be exercised.
set seen 0
set test "stepi"
if {[gdb_test_multiple "stepi" "$test" {
-re "infrun: random signal" {
set seen 1
exp_continue
}
-re "$gdb_prompt $" {
}
}] != 0} {
return
}
if {$seen} {
pass "$test"
} else {
fail "$test (no random signal)"
}
set addr [get_pc "after stepi"]
if {$addr == ""} {
return
}
set test "stepi interfered by signal makes progress"
if {$addr == $prev_addr} {
fail "$test"
} else {
pass "$test"
}