1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Stas Sergeev <stsp@users.sourceforge.net>
4 *
5 * test sigaltstack(SS_ONSTACK | SS_AUTODISARM)
6 * If that succeeds, then swapcontext() can be used inside sighandler safely.
7 *
8 */
9
10 #define _GNU_SOURCE
11 #include <signal.h>
12 #include <stdio.h>
13 #include <stdlib.h>
14 #include <sys/mman.h>
15 #include <ucontext.h>
16 #include <alloca.h>
17 #include <string.h>
18 #include <assert.h>
19 #include <errno.h>
20 #include <sys/auxv.h>
21
22 #include "../kselftest.h"
23 #include "current_stack_pointer.h"
24
25 #ifndef SS_AUTODISARM
26 #define SS_AUTODISARM (1U << 31)
27 #endif
28
29 #ifndef AT_MINSIGSTKSZ
30 #define AT_MINSIGSTKSZ 51
31 #endif
32
33 static unsigned int stack_size;
34 static void *sstack, *ustack;
35 static ucontext_t uc, sc;
36 static const char *msg = "[OK]\tStack preserved";
37 static const char *msg2 = "[FAIL]\tStack corrupted";
38 struct stk_data {
39 char msg[128];
40 int flag;
41 };
42
my_usr1(int sig,siginfo_t * si,void * u)43 void my_usr1(int sig, siginfo_t *si, void *u)
44 {
45 char *aa;
46 int err;
47 stack_t stk;
48 struct stk_data *p;
49
50 if (sp < (unsigned long)sstack ||
51 sp >= (unsigned long)sstack + stack_size) {
52 ksft_exit_fail_msg("SP is not on sigaltstack\n");
53 }
54 /* put some data on stack. other sighandler will try to overwrite it */
55 aa = alloca(1024);
56 assert(aa);
57 p = (struct stk_data *)(aa + 512);
58 strcpy(p->msg, msg);
59 p->flag = 1;
60 ksft_print_msg("[RUN]\tsignal USR1\n");
61 err = sigaltstack(NULL, &stk);
62 if (err) {
63 ksft_exit_fail_msg("sigaltstack() - %s\n", strerror(errno));
64 exit(EXIT_FAILURE);
65 }
66 if (stk.ss_flags != SS_DISABLE)
67 ksft_test_result_fail("tss_flags=%x, should be SS_DISABLE\n",
68 stk.ss_flags);
69 else
70 ksft_test_result_pass(
71 "sigaltstack is disabled in sighandler\n");
72 swapcontext(&sc, &uc);
73 ksft_print_msg("%s\n", p->msg);
74 if (!p->flag) {
75 ksft_exit_fail_msg("[RUN]\tAborting\n");
76 exit(EXIT_FAILURE);
77 }
78 }
79
my_usr2(int sig,siginfo_t * si,void * u)80 void my_usr2(int sig, siginfo_t *si, void *u)
81 {
82 char *aa;
83 struct stk_data *p;
84
85 ksft_print_msg("[RUN]\tsignal USR2\n");
86 aa = alloca(1024);
87 /* dont run valgrind on this */
88 /* try to find the data stored by previous sighandler */
89 p = memmem(aa, 1024, msg, strlen(msg));
90 if (p) {
91 ksft_test_result_fail("sigaltstack re-used\n");
92 /* corrupt the data */
93 strcpy(p->msg, msg2);
94 /* tell other sighandler that his data is corrupted */
95 p->flag = 0;
96 }
97 }
98
switch_fn(void)99 static void switch_fn(void)
100 {
101 ksft_print_msg("[RUN]\tswitched to user ctx\n");
102 raise(SIGUSR2);
103 setcontext(&sc);
104 }
105
main(void)106 int main(void)
107 {
108 struct sigaction act;
109 stack_t stk;
110 int err;
111
112 /* Make sure more than the required minimum. */
113 stack_size = getauxval(AT_MINSIGSTKSZ) + SIGSTKSZ;
114 ksft_print_msg("[NOTE]\tthe stack size is %lu\n", stack_size);
115
116 ksft_print_header();
117 ksft_set_plan(3);
118
119 sigemptyset(&act.sa_mask);
120 act.sa_flags = SA_ONSTACK | SA_SIGINFO;
121 act.sa_sigaction = my_usr1;
122 sigaction(SIGUSR1, &act, NULL);
123 act.sa_sigaction = my_usr2;
124 sigaction(SIGUSR2, &act, NULL);
125 sstack = mmap(NULL, stack_size, PROT_READ | PROT_WRITE,
126 MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
127 if (sstack == MAP_FAILED) {
128 ksft_exit_fail_msg("mmap() - %s\n", strerror(errno));
129 return EXIT_FAILURE;
130 }
131
132 err = sigaltstack(NULL, &stk);
133 if (err) {
134 ksft_exit_fail_msg("sigaltstack() - %s\n", strerror(errno));
135 exit(EXIT_FAILURE);
136 }
137 if (stk.ss_flags == SS_DISABLE) {
138 ksft_test_result_pass(
139 "Initial sigaltstack state was SS_DISABLE\n");
140 } else {
141 ksft_exit_fail_msg("Initial sigaltstack state was %x; "
142 "should have been SS_DISABLE\n", stk.ss_flags);
143 return EXIT_FAILURE;
144 }
145
146 stk.ss_sp = sstack;
147 stk.ss_size = stack_size;
148 stk.ss_flags = SS_ONSTACK | SS_AUTODISARM;
149 err = sigaltstack(&stk, NULL);
150 if (err) {
151 if (errno == EINVAL) {
152 ksft_test_result_skip(
153 "[NOTE]\tThe running kernel doesn't support SS_AUTODISARM\n");
154 /*
155 * If test cases for the !SS_AUTODISARM variant were
156 * added, we could still run them. We don't have any
157 * test cases like that yet, so just exit and report
158 * success.
159 */
160 return 0;
161 } else {
162 ksft_exit_fail_msg(
163 "sigaltstack(SS_ONSTACK | SS_AUTODISARM) %s\n",
164 strerror(errno));
165 return EXIT_FAILURE;
166 }
167 }
168
169 ustack = mmap(NULL, stack_size, PROT_READ | PROT_WRITE,
170 MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
171 if (ustack == MAP_FAILED) {
172 ksft_exit_fail_msg("mmap() - %s\n", strerror(errno));
173 return EXIT_FAILURE;
174 }
175 getcontext(&uc);
176 uc.uc_link = NULL;
177 uc.uc_stack.ss_sp = ustack;
178 uc.uc_stack.ss_size = stack_size;
179 makecontext(&uc, switch_fn, 0);
180 raise(SIGUSR1);
181
182 err = sigaltstack(NULL, &stk);
183 if (err) {
184 ksft_exit_fail_msg("sigaltstack() - %s\n", strerror(errno));
185 exit(EXIT_FAILURE);
186 }
187 if (stk.ss_flags != SS_AUTODISARM) {
188 ksft_exit_fail_msg("ss_flags=%x, should be SS_AUTODISARM\n",
189 stk.ss_flags);
190 exit(EXIT_FAILURE);
191 }
192 ksft_test_result_pass(
193 "sigaltstack is still SS_AUTODISARM after signal\n");
194
195 ksft_exit_pass();
196 return 0;
197 }
198