1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * 32-bit test to check vDSO mremap.
4 *
5 * Copyright (c) 2016 Dmitry Safonov
6 * Suggested-by: Andrew Lutomirski
7 */
8 /*
9 * Can be built statically:
10 * gcc -Os -Wall -static -m32 test_mremap_vdso.c
11 */
12 #define _GNU_SOURCE
13 #include <stdio.h>
14 #include <errno.h>
15 #include <unistd.h>
16 #include <string.h>
17
18 #include <sys/mman.h>
19 #include <sys/auxv.h>
20 #include <sys/syscall.h>
21 #include <sys/wait.h>
22 #include "../kselftest.h"
23
24 #define PAGE_SIZE 4096
25
try_to_remap(void * vdso_addr,unsigned long size)26 static int try_to_remap(void *vdso_addr, unsigned long size)
27 {
28 void *dest_addr, *new_addr;
29
30 /* Searching for memory location where to remap */
31 dest_addr = mmap(0, size, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
32 if (dest_addr == MAP_FAILED) {
33 ksft_print_msg("WARN: mmap failed (%d): %m\n", errno);
34 return 0;
35 }
36
37 ksft_print_msg("Moving vDSO: [%p, %#lx] -> [%p, %#lx]\n",
38 vdso_addr, (unsigned long)vdso_addr + size,
39 dest_addr, (unsigned long)dest_addr + size);
40 fflush(stdout);
41
42 new_addr = mremap(vdso_addr, size, size,
43 MREMAP_FIXED|MREMAP_MAYMOVE, dest_addr);
44 if ((unsigned long)new_addr == (unsigned long)-1) {
45 munmap(dest_addr, size);
46 if (errno == EINVAL) {
47 ksft_print_msg("vDSO partial move failed, will try with bigger size\n");
48 return -1; /* Retry with larger */
49 }
50 ksft_print_msg("[FAIL]\tmremap failed (%d): %m\n", errno);
51 return 1;
52 }
53
54 return 0;
55
56 }
57
main(int argc,char ** argv,char ** envp)58 int main(int argc, char **argv, char **envp)
59 {
60 pid_t child;
61
62 ksft_print_header();
63 ksft_set_plan(1);
64
65 child = fork();
66 if (child == -1)
67 ksft_exit_fail_msg("failed to fork (%d): %m\n", errno);
68
69 if (child == 0) {
70 unsigned long vdso_size = PAGE_SIZE;
71 unsigned long auxval;
72 int ret = -1;
73
74 auxval = getauxval(AT_SYSINFO_EHDR);
75 ksft_print_msg("AT_SYSINFO_EHDR is %#lx\n", auxval);
76 if (!auxval || auxval == -ENOENT) {
77 ksft_print_msg("WARN: getauxval failed\n");
78 return 0;
79 }
80
81 /* Simpler than parsing ELF header */
82 while (ret < 0) {
83 ret = try_to_remap((void *)auxval, vdso_size);
84 vdso_size += PAGE_SIZE;
85 }
86
87 #ifdef __i386__
88 /* Glibc is likely to explode now - exit with raw syscall */
89 asm volatile ("int $0x80" : : "a" (__NR_exit), "b" (!!ret));
90 #else /* __x86_64__ */
91 syscall(SYS_exit, ret);
92 #endif
93 } else {
94 int status;
95
96 if (waitpid(child, &status, 0) != child ||
97 !WIFEXITED(status))
98 ksft_test_result_fail("mremap() of the vDSO does not work on this kernel!\n");
99 else if (WEXITSTATUS(status) != 0)
100 ksft_test_result_fail("Child failed with %d\n", WEXITSTATUS(status));
101 else
102 ksft_test_result_pass("%s\n", __func__);
103 }
104
105 ksft_finished();
106 }
107