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Commit 6ed36158 authored by Michael Ellerman's avatar Michael Ellerman
Browse files

selftests/powerpc: Add a test of SEGV error behaviour 



Add a test case of the error code reported when we take a SEGV on a
mapped but inaccessible area. We broke this recently.

Based on a test case from John Sperbeck <jsperbeck@google.com>.

Acked-by: default avatarJohn Sperbeck <jsperbeck@google.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 5769beaf

tools/testing/selftests/powerpc/mm/.gitignore

+2 −1
Original line number Diff line number Diff line
@@ -2,3 +2,4 @@ hugetlb_vs_thp_test 
subpage_prot

tempfile

prot_sao

segv_errors
 
 No newline at end of file

tools/testing/selftests/powerpc/mm/Makefile

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@@ -2,7 +2,7 @@ 
noarg:

	$(MAKE) -C ../



TEST_GEN_PROGS := hugetlb_vs_thp_test subpage_prot prot_sao

TEST_GEN_PROGS := hugetlb_vs_thp_test subpage_prot prot_sao segv_errors

TEST_GEN_FILES := tempfile



include ../../lib.mk

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

0 → 100644
+78 −0
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// SPDX-License-Identifier: GPL-2.0



/*

 * Copyright 2017 John Sperbeck

 *

 * Test that an access to a mapped but inaccessible area causes a SEGV and

 * reports si_code == SEGV_ACCERR.

 */



#include <stdbool.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <signal.h>

#include <sys/mman.h>

#include <assert.h>

#include <ucontext.h>



#include "utils.h"



static bool faulted;

static int si_code;



static void segv_handler(int n, siginfo_t *info, void *ctxt_v)

{

	ucontext_t *ctxt = (ucontext_t *)ctxt_v;

	struct pt_regs *regs = ctxt->uc_mcontext.regs;



	faulted = true;

	si_code = info->si_code;

	regs->nip += 4;

}



int test_segv_errors(void)

{

	struct sigaction act = {

		.sa_sigaction = segv_handler,

		.sa_flags = SA_SIGINFO,

	};

	char c, *p = NULL;



	p = mmap(NULL, getpagesize(), 0, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);

	FAIL_IF(p == MAP_FAILED);



	FAIL_IF(sigaction(SIGSEGV, &act, NULL) != 0);



	faulted = false;

	si_code = 0;



	/*

	 * We just need a compiler barrier, but mb() works and has the nice

	 * property of being easy to spot in the disassembly.

	 */

	mb();

	c = *p;

	mb();



	FAIL_IF(!faulted);

	FAIL_IF(si_code != SEGV_ACCERR);



	faulted = false;

	si_code = 0;



	mb();

	*p = c;

	mb();



	FAIL_IF(!faulted);

	FAIL_IF(si_code != SEGV_ACCERR);



	return 0;

}



int main(void)

{

	return test_harness(test_segv_errors, "segv_errors");

}