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5a0c4a06eb
The check removed by this patch, using current_inferior, looks wrong. When debugging multiple inferiors with the Linux native target and linux_handle_extended_wait is called, there's no guarantee about which is the current inferior. The vfork-done event we receive could be for any inferior. If the vfork-done event is for a non-current inferior, we end up wrongfully ignoring it. As a result, the core never processes a TARGET_WAITKIND_VFORK_DONE event, program_space::breakpoints_not_allowed is never cleared, and breakpoints are never reinserted. However, because the Linux native target decided to ignore the event, it resumed the thread - while breakpoints out. And that's bad. The proposed fix is to remove this check. Always report vfork-done events and let infrun's logic decide if it should be ignored. We don't save much cycles by filtering the event here. Add a test that replicates the situation described above. See comments in the test for more details. Change-Id: Ibe33c1716c3602e847be6c2093120696f2286fbf
116 lines
4.3 KiB
Plaintext
116 lines
4.3 KiB
Plaintext
# Copyright 2020-2022 Free Software Foundation, Inc.
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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# Test handling a vfork while another inferior is running. The bug that
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# prompted writing this test case was in the Linux native target. The target
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# assumed that the vfork-done event it received was for the current inferior
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# (an invalid assumption, the current inferior is the one randomly selected by
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# do_target_wait (at the time of writing). This caused the target to drop the
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# vfork-done event, because it was seen as unneeded and to restart the thread
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# as if nothing happened. This however resulted in the thread running with
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# breakpoints not inserted.
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#
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# To catch the bug, this test verifies that we can hit a breakpoint after a
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# vfork call, while a second inferior runs in the background.
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if [use_gdb_stub] {
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unsupported "test uses multiple inferiors"
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return
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}
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standard_testfile .c -sleep.c
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set srcfile_sleep $srcfile2
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set binfile_sleep ${binfile}-sleep
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# The reproducibility of the bug depends on which inferior randomly selects in
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# do_target_wait when consuming the vfork-done event. Since GDB doesn't call
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# srand(), we are likely to always see the same sequence of inferior selected by
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# do_target_wait, which can hide the bug if you are not "lucky". To work
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# around that, call vfork and hit the breakpoint in a loop, it makes it
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# somewhat likely that the wrong inferior will be selected eventually.
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set nr_loops 20
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# Compile the main program that calls vfork and hits a breakpoint.
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set opts [list debug additional_flags=-DNR_LOOPS=$nr_loops]
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if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable \
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$opts] != "" } {
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untested "failed to compile"
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return -1
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}
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# Compile the secondary program, which just sleeps.
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if { [gdb_compile "${srcdir}/${subdir}/${srcfile_sleep}" "${binfile_sleep}" executable \
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{debug}] != "" } {
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untested "failed to compile"
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return -1
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}
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# We exercise two methods of getting a second inferior to execute while the
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# first one vforks. METHOD can be:
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#
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# - non-stop: start GDB with non-stop on and run the second inferior in
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# background.
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# - schedule-multiple: set "schedule-multiple on", this will make "continue"
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# resume both inferiors.
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proc do_test {method} {
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save_vars { ::GDBFLAGS } {
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if { $method == "non-stop" } {
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append ::GDBFLAGS " -ex \"set non-stop on\""
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}
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clean_restart
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}
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# Start the second inferior in background.
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gdb_test "add-inferior" "Added inferior 2.*"
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gdb_test "inferior 2" "Switching to inferior 2 .*"
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gdb_file_cmd ${::binfile_sleep}
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if { $method == "non-stop" } {
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gdb_test "run &" "Starting program: .*" "run inferior 2"
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} else {
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gdb_test "start" "Temporary breakpoint $::decimal, main .*" \
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"start inferior 2"
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}
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# Start the first inferior.
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gdb_test "inferior 1" "Switching to inferior 1 .*"
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gdb_file_cmd ${::binfile}
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gdb_test "break should_break_here" "Breakpoint $::decimal at .*"
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gdb_test "start" "Thread 1.1 .* hit Temporary breakpoint.*" \
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"start inferior 1"
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# Only enable schedule-multiple this late, because of:
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# https://sourceware.org/bugzilla/show_bug.cgi?id=28777
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if { $method == "schedule-multiple" } {
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gdb_test_no_output "set schedule-multiple on"
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}
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# Continue over vfork and until the breakpoint. The number of loops here
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# matches the number of loops in the program. So if a breakpoint is missed
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# at some point, a "continue" will wrongfully continue until the end of the
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# program, which will fail the test.
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for {set i 0} {$i < $::nr_loops} {incr i} {
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with_test_prefix "i=$i" {
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gdb_test "continue" \
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"Thread 1.1 .* hit Breakpoint $::decimal, should_break_here.*"
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}
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}
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}
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foreach_with_prefix method {schedule-multiple non-stop} {
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do_test $method
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}
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