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Commit 16391bfc authored by Michael Ellerman's avatar Michael Ellerman
Browse files

selftests/powerpc: Add test of fork with mapping above 512TB 



This tests that when a process with a mapping above 512TB forks we
correctly separate the parent and child address spaces. This exercises
the bug in the context id handling fixed in the previous commit.

Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent ca72d883

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

+2 −1
Original line number Diff line number Diff line
@@ -4,3 +4,4 @@ tempfile 
prot_sao

segv_errors

wild_bctr

large_vm_fork_separation
 
 No newline at end of file

tools/testing/selftests/powerpc/mm/Makefile

+3 −1
Original line number Diff line number Diff line
@@ -2,7 +2,8 @@ 
noarg:

	$(MAKE) -C ../



TEST_GEN_PROGS := hugetlb_vs_thp_test subpage_prot prot_sao segv_errors wild_bctr

TEST_GEN_PROGS := hugetlb_vs_thp_test subpage_prot prot_sao segv_errors wild_bctr \

		  large_vm_fork_separation

TEST_GEN_FILES := tempfile



top_srcdir = ../../../../..
@@ -13,6 +14,7 @@ $(TEST_GEN_PROGS): ../harness.c 
$(OUTPUT)/prot_sao: ../utils.c



$(OUTPUT)/wild_bctr: CFLAGS += -m64

$(OUTPUT)/large_vm_fork_separation: CFLAGS += -m64



$(OUTPUT)/tempfile:

	dd if=/dev/zero of=$@ bs=64k count=1

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

0 → 100644
+87 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0+

//

// Copyright 2019, Michael Ellerman, IBM Corp.

//

// Test that allocating memory beyond the memory limit and then forking is

// handled correctly, ie. the child is able to access the mappings beyond the

// memory limit and the child's writes are not visible to the parent.



#include <stdio.h>

#include <stdlib.h>

#include <sys/mman.h>

#include <sys/types.h>

#include <sys/wait.h>

#include <unistd.h>



#include "utils.h"





#ifndef MAP_FIXED_NOREPLACE

#define MAP_FIXED_NOREPLACE	MAP_FIXED	// "Should be safe" above 512TB

#endif





static int test(void)

{

	int p2c[2], c2p[2], rc, status, c, *p;

	unsigned long page_size;

	pid_t pid;



	page_size = sysconf(_SC_PAGESIZE);

	SKIP_IF(page_size != 65536);



	// Create a mapping at 512TB to allocate an extended_id

	p = mmap((void *)(512ul << 40), page_size, PROT_READ | PROT_WRITE,

		MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED_NOREPLACE, -1, 0);

	if (p == MAP_FAILED) {

		perror("mmap");

		printf("Error: couldn't mmap(), confirm kernel has 4TB support?\n");

		return 1;

	}



	printf("parent writing %p = 1\n", p);

	*p = 1;



	FAIL_IF(pipe(p2c) == -1 || pipe(c2p) == -1);



	pid = fork();

	if (pid == 0) {

		FAIL_IF(read(p2c[0], &c, 1) != 1);



		pid = getpid();

		printf("child writing  %p = %d\n", p, pid);

		*p = pid;



		FAIL_IF(write(c2p[1], &c, 1) != 1);

		FAIL_IF(read(p2c[0], &c, 1) != 1);

		exit(0);

	}



	c = 0;

	FAIL_IF(write(p2c[1], &c, 1) != 1);

	FAIL_IF(read(c2p[0], &c, 1) != 1);



	// Prevent compiler optimisation

	barrier();



	rc = 0;

	printf("parent reading %p = %d\n", p, *p);

	if (*p != 1) {

		printf("Error: BUG! parent saw child's write! *p = %d\n", *p);

		rc = 1;

	}



	FAIL_IF(write(p2c[1], &c, 1) != 1);

	FAIL_IF(waitpid(pid, &status, 0) == -1);

	FAIL_IF(!WIFEXITED(status) || WEXITSTATUS(status));



	if (rc == 0)

		printf("success: test completed OK\n");



	return rc;

}



int main(void)

{

	return test_harness(test, "large_vm_fork_separation");

}