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
22static bool faulted;
23static int si_code;
24
25static 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
35int 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
75int main(void)
76{
77 return test_harness(test_segv_errors, "segv_errors");
78}
79

source code of linux/tools/testing/selftests/powerpc/mm/segv_errors.c