1// SPDX-License-Identifier: GPL-2.0+
2//
3// Copyright 2019, Michael Ellerman, IBM Corp.
4//
5// Test that allocating memory beyond the memory limit and then forking is
6// handled correctly, ie. the child is able to access the mappings beyond the
7// memory limit and the child's writes are not visible to the parent.
8
9#include <stdio.h>
10#include <stdlib.h>
11#include <sys/mman.h>
12#include <sys/types.h>
13#include <sys/wait.h>
14#include <unistd.h>
15
16#include "utils.h"
17
18
19#ifndef MAP_FIXED_NOREPLACE
20#define MAP_FIXED_NOREPLACE	MAP_FIXED	// "Should be safe" above 512TB
21#endif
22
23
24static int test(void)
25{
26	int p2c[2], c2p[2], rc, status, c, *p;
27	unsigned long page_size;
28	pid_t pid;
29
30	page_size = sysconf(_SC_PAGESIZE);
31	SKIP_IF(page_size != 65536);
32
33	// Create a mapping at 512TB to allocate an extended_id
34	p = mmap((void *)(512ul << 40), page_size, PROT_READ | PROT_WRITE,
35		MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED_NOREPLACE, -1, 0);
36	if (p == MAP_FAILED) {
37		perror("mmap");
38		printf("Error: couldn't mmap(), confirm kernel has 4TB support?\n");
39		return 1;
40	}
41
42	printf("parent writing %p = 1\n", p);
43	*p = 1;
44
45	FAIL_IF(pipe(p2c) == -1 || pipe(c2p) == -1);
46
47	pid = fork();
48	if (pid == 0) {
49		FAIL_IF(read(p2c[0], &c, 1) != 1);
50
51		pid = getpid();
52		printf("child writing  %p = %d\n", p, pid);
53		*p = pid;
54
55		FAIL_IF(write(c2p[1], &c, 1) != 1);
56		FAIL_IF(read(p2c[0], &c, 1) != 1);
57		exit(0);
58	}
59
60	c = 0;
61	FAIL_IF(write(p2c[1], &c, 1) != 1);
62	FAIL_IF(read(c2p[0], &c, 1) != 1);
63
64	// Prevent compiler optimisation
65	barrier();
66
67	rc = 0;
68	printf("parent reading %p = %d\n", p, *p);
69	if (*p != 1) {
70		printf("Error: BUG! parent saw child's write! *p = %d\n", *p);
71		rc = 1;
72	}
73
74	FAIL_IF(write(p2c[1], &c, 1) != 1);
75	FAIL_IF(waitpid(pid, &status, 0) == -1);
76	FAIL_IF(!WIFEXITED(status) || WEXITSTATUS(status));
77
78	if (rc == 0)
79		printf("success: test completed OK\n");
80
81	return rc;
82}
83
84int main(void)
85{
86	return test_harness(test, "large_vm_fork_separation");
87}
88