cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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segv_errors.c (1384B)

      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}