1# Copyright 2018-2023 Free Software Foundation, Inc.
2#
3# This program is free software; you can redistribute it and/or modify
4# it under the terms of the GNU General Public License as published by
5# the Free Software Foundation; either version 3 of the License, or
6# (at your option) any later version.
7#
8# This program is distributed in the hope that it will be useful,
9# but WITHOUT ANY WARRANTY; without even the implied warranty of
10# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
11# GNU General Public License for more details.
12#
13# You should have received a copy of the GNU General Public License
14# along with this program.  If not, see <http://www.gnu.org/licenses/>.
15
16# This test script tries to expose a bug in some of the uses of
17# waitpid in the Linux native support within GDB.  The problem was
18# spotted on systems which were heavily loaded when attaching to
19# threaded test programs.  What happened was that during the initial
20# attach, the loop of waitpid calls that normally received the stop
21# events from each of the threads in the inferior was not receiving a
22# stop event for some threads (the kernel just hadn't sent the stop
23# event yet).
24#
25# GDB would then trigger a call to stop_all_threads which would
26# continue to wait for all of the outstanding threads to stop, when
27# the outstanding stop events finally arrived GDB would then
28# (incorrectly) discard the stop event, resume the thread, and
29# continue to wait for the thread to stop.... which it now never
30# would.
31#
32# In order to try and expose this issue reliably, this test preloads a
33# library that intercepts waitpid calls.  All waitpid calls targeting
34# pid -1 with the WNOHANG flag are rate limited so that only 1 per
35# second can complete.  Additional calls are forced to return 0
36# indicating no event waiting.  This is enough to trigger the bug
37# during the attach phase.
38
39# This test only works on Linux
40if { ![isnative] || [is_remote host] || [use_gdb_stub]
41     || ![istarget *-linux*] } {
42    return
43}
44
45standard_testfile
46
47set libfile slow-waitpid
48set libsrc "${srcdir}/${subdir}/${libfile}.c"
49set libobj [standard_output_file ${libfile}.so]
50
51with_test_prefix "compile preload library" {
52    # Compile the preload library.  We only get away with this as we
53    # limit this test to running when ISNATIVE is true.
54    if { [gdb_compile_shlib_pthreads \
55	      $libsrc $libobj {debug}] != "" } then {
56	return -1
57    }
58}
59
60with_test_prefix "compile test executable" {
61    # Compile the test program
62    if { [gdb_compile_pthreads \
63	      "${srcdir}/${subdir}/${srcfile}" "${binfile}" \
64	      executable {debug}] != "" } {
65	return -1
66    }
67}
68
69# Spawn GDB with LIB preloaded with LD_PRELOAD.
70
71proc gdb_spawn_with_ld_preload {lib} {
72    global env
73
74    save_vars { env(LD_PRELOAD) env(ASAN_OPTIONS) } {
75	if { ![info exists env(LD_PRELOAD) ]
76	     || $env(LD_PRELOAD) == "" } {
77	    set env(LD_PRELOAD) "$lib"
78	} else {
79	    append env(LD_PRELOAD) ":$lib"
80	}
81
82	# Prevent address sanitizer error:
83	# ASan runtime does not come first in initial library list; you should
84	# either link runtime to your application or manually preload it with
85	# LD_PRELOAD.
86	set_sanitizer_default ASAN_OPTIONS verify_asan_link_order 0
87
88	gdb_start
89    }
90}
91
92# Run test program in the background.
93set test_spawn_id [spawn_wait_for_attach $binfile]
94set testpid [spawn_id_get_pid $test_spawn_id]
95
96# Start GDB with preload library in place.
97if { [gdb_spawn_with_ld_preload $libobj] == -1 } {
98    # Make sure we get UNTESTED rather than UNRESOLVED.
99    set errcnt 0
100    untested "Couldn't start GDB with preloaded lib"
101    return -1
102}
103
104# Load binary, and attach to running program.
105gdb_load ${binfile}
106gdb_test "attach $testpid" "Attaching to program.*" "attach to target"
107
108gdb_exit
109
110# Kill of test program.
111kill_wait_spawned_process $test_spawn_id
112