sigreturn_vdso.c

  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("[vdso]", &low, &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("[vdso]", &low, &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("[vdso]", &low, &high) != 0);
110
111	// Make the stack executable
112	assert(search_proc_maps("[stack]", &low, &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}