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 
segv_handler(int n,siginfo_t * info,void * ctxt_v)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 
test_segv_errors(void)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 
main(void)75 int main(void)
76 {
77 	return test_harness(test_segv_errors, "segv_errors");
78 }
79