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
test(void)24 static 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
main(void)84 int main(void)
85 {
86 return test_harness(test, "large_vm_fork_separation");
87 }
88
