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// 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");
}
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