1 // SPDX-License-Identifier: GPL-2.0
2
3 /*
4 * Copyright 2017 John Sperbeck
5 *
6 * Test that an access to a mapped but inaccessible area causes a SEGV and
7 * reports si_code == SEGV_ACCERR.
8 */
9
10 #include <stdbool.h>
11 #include <stdio.h>
12 #include <stdlib.h>
13 #include <string.h>
14 #include <unistd.h>
15 #include <signal.h>
16 #include <sys/mman.h>
17 #include <assert.h>
18 #include <ucontext.h>
19
20 #include "utils.h"
21
22 static bool faulted;
23 static int si_code;
24
25 static void segv_handler(int n, siginfo_t *info, void *ctxt_v)
26 {
27 ucontext_t *ctxt = (ucontext_t *)ctxt_v;
28 struct pt_regs *regs = ctxt->uc_mcontext.regs;
29
30 faulted = true;
31 si_code = info->si_code;
32 regs->nip += 4;
33 }
34
35 int test_segv_errors(void)
36 {
37 struct sigaction act = {
38 .sa_sigaction = segv_handler,
39 .sa_flags = SA_SIGINFO,
40 };
41 char c, *p = NULL;
42
43 p = mmap(NULL, getpagesize(), 0, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
44 FAIL_IF(p == MAP_FAILED);
45
46 FAIL_IF(sigaction(SIGSEGV, &act, NULL) != 0);
47
48 faulted = false;
49 si_code = 0;
50
51 /*
52 * We just need a compiler barrier, but mb() works and has the nice
53 * property of being easy to spot in the disassembly.
54 */
55 mb();
56 c = *p;
57 mb();
58
59 FAIL_IF(!faulted);
60 FAIL_IF(si_code != SEGV_ACCERR);
61
62 faulted = false;
63 si_code = 0;
64
65 mb();
66 *p = c;
67 mb();
68
69 FAIL_IF(!faulted);
70 FAIL_IF(si_code != SEGV_ACCERR);
71
72 return 0;
73 }
74
75 int main(void)
76 {
77 return test_harness(test_segv_errors, "segv_errors");
78 }
79
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.