1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Test that we can take signals with and without the VDSO mapped, which trigger
4 * different paths in the signal handling code.
5 *
6 * See handle_rt_signal64() and setup_trampoline() in signal_64.c
7 */
8
9#define _GNU_SOURCE
10
11#include <errno.h>
12#include <stdio.h>
13#include <signal.h>
14#include <stdlib.h>
15#include <string.h>
16#include <sys/mman.h>
17#include <sys/types.h>
18#include <unistd.h>
19
20// Ensure assert() is not compiled out
21#undef NDEBUG
22#include <assert.h>
23
24#include "utils.h"
25
26static int search_proc_maps(char *needle, unsigned long *low, unsigned long *high)
27{
28 unsigned long start, end;
29 static char buf[4096];
30 char name[128];
31 FILE *f;
32 int rc = -1;
33
34 f = fopen("/proc/self/maps", "r");
35 if (!f) {
36 perror("fopen");
37 return -1;
38 }
39
40 while (fgets(buf, sizeof(buf), f)) {
41 rc = sscanf(buf, "%lx-%lx %*c%*c%*c%*c %*x %*d:%*d %*d %127s\n",
42 &start, &end, name);
43 if (rc == 2)
44 continue;
45
46 if (rc != 3) {
47 printf("sscanf errored\n");
48 rc = -1;
49 break;
50 }
51
52 if (strstr(name, needle)) {
53 *low = start;
54 *high = end - 1;
55 rc = 0;
56 break;
57 }
58 }
59
60 fclose(f);
61
62 return rc;
63}
64
65static volatile sig_atomic_t took_signal = 0;
66
67static void sigusr1_handler(int sig)
68{
69 took_signal++;
70}
71
72int test_sigreturn_vdso(void)
73{
74 unsigned long low, high, size;
75 struct sigaction act;
76 char *p;
77
78 act.sa_handler = sigusr1_handler;
79 act.sa_flags = 0;
80 sigemptyset(&act.sa_mask);
81
82 assert(sigaction(SIGUSR1, &act, NULL) == 0);
83
84 // Confirm the VDSO is mapped, and work out where it is
85 assert(search_proc_maps(needle: "[vdso]", low: &low, high: &high) == 0);
86 size = high - low + 1;
87 printf("VDSO is at 0x%lx-0x%lx (%lu bytes)\n", low, high, size);
88
89 kill(getpid(), SIGUSR1);
90 assert(took_signal == 1);
91 printf("Signal delivered OK with VDSO mapped\n");
92
93 // Remap the VDSO somewhere else
94 p = mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
95 assert(p != MAP_FAILED);
96 assert(mremap((void *)low, size, size, MREMAP_MAYMOVE|MREMAP_FIXED, p) != MAP_FAILED);
97 assert(search_proc_maps(needle: "[vdso]", low: &low, high: &high) == 0);
98 size = high - low + 1;
99 printf("VDSO moved to 0x%lx-0x%lx (%lu bytes)\n", low, high, size);
100
101 kill(getpid(), SIGUSR1);
102 assert(took_signal == 2);
103 printf("Signal delivered OK with VDSO moved\n");
104
105 assert(munmap((void *)low, size) == 0);
106 printf("Unmapped VDSO\n");
107
108 // Confirm the VDSO is not mapped anymore
109 assert(search_proc_maps(needle: "[vdso]", low: &low, high: &high) != 0);
110
111 // Make the stack executable
112 assert(search_proc_maps(needle: "[stack]", low: &low, high: &high) == 0);
113 size = high - low + 1;
114 mprotect((void *)low, size, PROT_READ|PROT_WRITE|PROT_EXEC);
115 printf("Remapped the stack executable\n");
116
117 kill(getpid(), SIGUSR1);
118 assert(took_signal == 3);
119 printf("Signal delivered OK with VDSO unmapped\n");
120
121 return 0;
122}
123
124int main(void)
125{
126 return test_harness(test_sigreturn_vdso, "sigreturn_vdso");
127}
128

source code of linux/tools/testing/selftests/powerpc/signal/sigreturn_vdso.c