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fbbc9a4e | 1 | /* Tests of signal delivery on an alternate stack (nonlethal). |
dff8da6b | 2 | Copyright (C) 2019-2024 Free Software Foundation, Inc. |
fbbc9a4e ZW |
3 | This file is part of the GNU C Library. |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
16 | License along with the GNU C Library; if not, see | |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
fbbc9a4e ZW |
18 | |
19 | #include <support/xsignal.h> | |
20 | #include <support/support.h> | |
21 | #include <support/check.h> | |
22 | ||
23 | /* C2011 7.4.1.1p5 specifies that only the following operations are | |
24 | guaranteed to be well-defined inside an asynchronous signal handler: | |
25 | * any operation on a lock-free atomic object | |
26 | * assigning a value to an object declared as volatile sig_atomic_t | |
27 | * calling abort, _Exit, quick_exit, or signal | |
28 | * signal may only be called with its first argument equal to the | |
29 | number of the signal that caused the handler to be called | |
30 | ||
31 | We use this list as a guideline for the set of operations that ought | |
32 | also to be safe in a _synchronous_ signal delivered on an alternate | |
33 | signal stack with only MINSIGSTKSZ bytes of space. | |
34 | ||
35 | This test program tests all of the above operations that do not, | |
36 | one way or another, cause the program to be terminated. */ | |
37 | ||
38 | /* We do not try to test atomic operations exhaustively, only a simple | |
39 | atomic counter increment. This is only safe if atomic_[u]int is | |
40 | unconditionally lock-free. */ | |
41 | #ifdef __STDC_NO_ATOMICS__ | |
42 | # define TEST_ATOMIC_OPS 0 | |
43 | #else | |
44 | # include <stdatomic.h> | |
45 | # if ATOMIC_INT_LOCK_FREE != 2 | |
46 | # define TEST_ATOMIC_OPS 0 | |
47 | # else | |
48 | # define TEST_ATOMIC_OPS 1 | |
49 | # endif | |
50 | #endif | |
51 | ||
52 | static volatile sig_atomic_t signal_flag = 0; | |
53 | static volatile sig_atomic_t signal_err = 0; | |
54 | static void | |
55 | handler_set_flag (int unused) | |
56 | { | |
57 | signal_flag = 1; | |
58 | } | |
59 | ||
60 | static void | |
61 | handler_set_flag_once (int sig) | |
62 | { | |
63 | signal_flag = 1; | |
64 | if (signal (sig, SIG_IGN) == SIG_ERR) | |
65 | /* It is not safe to call FAIL_EXIT1 here. Set another flag instead. */ | |
66 | signal_err = 1; | |
67 | } | |
68 | ||
69 | #if TEST_ATOMIC_OPS | |
70 | static atomic_uint signal_count = 0; | |
71 | static void | |
72 | handler_count_up_1 (int unused) | |
73 | { | |
74 | atomic_fetch_add (&signal_count, 1); | |
75 | } | |
76 | #endif | |
77 | ||
78 | int | |
79 | do_test (void) | |
80 | { | |
81 | void *sstk = xalloc_sigstack (0); | |
82 | struct sigaction sa; | |
83 | ||
84 | /* Test 1: setting a volatile sig_atomic_t flag. */ | |
85 | sa.sa_handler = handler_set_flag; | |
86 | sa.sa_flags = SA_RESTART | SA_ONSTACK; | |
87 | sigfillset (&sa.sa_mask); | |
88 | if (sigaction (SIGUSR1, &sa, 0)) | |
89 | FAIL_EXIT1 ("sigaction (SIGUSR1, handler_set_flag): %m\n"); | |
90 | ||
91 | TEST_VERIFY_EXIT (signal_flag == 0); | |
92 | raise (SIGUSR1); | |
93 | TEST_VERIFY_EXIT (signal_flag == 1); | |
94 | signal_flag = 0; | |
95 | raise (SIGUSR1); | |
96 | TEST_VERIFY_EXIT (signal_flag == 1); | |
97 | signal_flag = 0; | |
98 | ||
99 | /* Test 1: setting a volatile sig_atomic_t flag and then ignoring | |
100 | further delivery of the signal. */ | |
101 | sa.sa_handler = handler_set_flag_once; | |
102 | if (sigaction (SIGUSR1, &sa, 0)) | |
103 | FAIL_EXIT1 ("sigaction (SIGUSR1, handler_set_flag_once): %m\n"); | |
104 | ||
105 | raise (SIGUSR1); | |
106 | TEST_VERIFY_EXIT (signal_flag == 1); | |
107 | /* Note: if signal_err is 1, a system call failed, but we can't | |
108 | report the error code because errno is indeterminate. */ | |
109 | TEST_VERIFY_EXIT (signal_err == 0); | |
110 | ||
111 | signal_flag = 0; | |
112 | raise (SIGUSR1); | |
113 | TEST_VERIFY_EXIT (signal_flag == 0); | |
114 | TEST_VERIFY_EXIT (signal_err == 0); | |
115 | ||
116 | #if TEST_ATOMIC_OPS | |
117 | sa.sa_handler = handler_count_up_1; | |
118 | if (sigaction (SIGUSR1, &sa, 0)) | |
119 | FAIL_EXIT1 ("sigaction (SIGUSR1, handler_count_up_1): %m\n"); | |
120 | ||
121 | raise (SIGUSR1); | |
122 | TEST_VERIFY_EXIT (atomic_load (&signal_count) == 1); | |
123 | raise (SIGUSR1); | |
124 | TEST_VERIFY_EXIT (atomic_load (&signal_count) == 2); | |
125 | #endif | |
126 | ||
127 | xfree_sigstack (sstk); | |
128 | return 0; | |
129 | } | |
130 | ||
131 | #include <support/test-driver.c> |