tools/testing/selftests/powerpc/mm/segv_errors.c

   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 }