// SPDX-License-Identifier: GPL-2.0+
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//
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// Copyright 2019, Michael Ellerman, IBM Corp.
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//
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// Test that allocating memory beyond the memory limit and then forking is
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// handled correctly, ie. the child is able to access the mappings beyond the
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// memory limit and the child's writes are not visible to the parent.
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/mman.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <unistd.h>
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#include "utils.h"
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#ifndef MAP_FIXED_NOREPLACE
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#define MAP_FIXED_NOREPLACE MAP_FIXED // "Should be safe" above 512TB
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#endif
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static int test(void)
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{
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int p2c[2], c2p[2], rc, status, c, *p;
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unsigned long page_size;
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pid_t pid;
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page_size = sysconf(_SC_PAGESIZE);
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SKIP_IF(page_size != 65536);
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// Create a mapping at 512TB to allocate an extended_id
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p = mmap((void *)(512ul << 40), page_size, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED_NOREPLACE, -1, 0);
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if (p == MAP_FAILED) {
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perror("mmap");
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printf("Error: couldn't mmap(), confirm kernel has 4TB support?\n");
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return 1;
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}
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printf("parent writing %p = 1\n", p);
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*p = 1;
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FAIL_IF(pipe(p2c) == -1 || pipe(c2p) == -1);
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pid = fork();
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if (pid == 0) {
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FAIL_IF(read(p2c[0], &c, 1) != 1);
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pid = getpid();
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printf("child writing %p = %d\n", p, pid);
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*p = pid;
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FAIL_IF(write(c2p[1], &c, 1) != 1);
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FAIL_IF(read(p2c[0], &c, 1) != 1);
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exit(0);
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}
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c = 0;
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FAIL_IF(write(p2c[1], &c, 1) != 1);
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FAIL_IF(read(c2p[0], &c, 1) != 1);
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// Prevent compiler optimisation
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barrier();
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rc = 0;
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printf("parent reading %p = %d\n", p, *p);
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if (*p != 1) {
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printf("Error: BUG! parent saw child's write! *p = %d\n", *p);
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rc = 1;
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}
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FAIL_IF(write(p2c[1], &c, 1) != 1);
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FAIL_IF(waitpid(pid, &status, 0) == -1);
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FAIL_IF(!WIFEXITED(status) || WEXITSTATUS(status));
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if (rc == 0)
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printf("success: test completed OK\n");
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return rc;
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}
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int main(void)
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{
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return test_harness(test, "large_vm_fork_separation");
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}
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