1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (c) 2018 Dmitry Safonov, Arista Networks
5 * MAP_POPULATE | MAP_PRIVATE should COW VMA pages.
12 #include <sys/socket.h>
13 #include <sys/types.h>
24 #define BUG_ON(condition, description) \
27 fprintf(stderr, "[FAIL]\t%s:%d\t%s:%s\n", __func__, \
28 __LINE__, (description), strerror(errno)); \
33 static int parent_f(int sock, unsigned long *smap, int child)
37 ret = read(sock, &status, sizeof(int));
38 BUG_ON(ret <= 0, "read(sock)");
41 ret = msync(smap, MMAP_SZ, MS_SYNC);
42 BUG_ON(ret, "msync()");
44 ret = write(sock, &status, sizeof(int));
45 BUG_ON(ret <= 0, "write(sock)");
47 waitpid(child, &status, 0);
48 BUG_ON(!WIFEXITED(status), "child in unexpected state");
50 return WEXITSTATUS(status);
53 static int child_f(int sock, unsigned long *smap, int fd)
57 smap = mmap(0, MMAP_SZ, PROT_READ | PROT_WRITE,
58 MAP_PRIVATE | MAP_POPULATE, fd, 0);
59 BUG_ON(smap == MAP_FAILED, "mmap()");
61 BUG_ON(*smap != 0xdeadbabe, "MAP_PRIVATE | MAP_POPULATE changed file");
63 ret = write(sock, &buf, sizeof(int));
64 BUG_ON(ret <= 0, "write(sock)");
66 ret = read(sock, &buf, sizeof(int));
67 BUG_ON(ret <= 0, "read(sock)");
69 BUG_ON(*smap == 0x22222BAD, "MAP_POPULATE didn't COW private page");
70 BUG_ON(*smap != 0xdeadbabe, "mapping was corrupted");
75 int main(int argc, char **argv)
77 int sock[2], child, ret;
82 BUG_ON(ftmp == 0, "tmpfile()");
84 ret = ftruncate(fileno(ftmp), MMAP_SZ);
85 BUG_ON(ret, "ftruncate()");
87 smap = mmap(0, MMAP_SZ, PROT_READ | PROT_WRITE,
88 MAP_SHARED, fileno(ftmp), 0);
89 BUG_ON(smap == MAP_FAILED, "mmap()");
92 /* Probably unnecessary, but let it be. */
93 ret = msync(smap, MMAP_SZ, MS_SYNC);
94 BUG_ON(ret, "msync()");
96 ret = socketpair(PF_LOCAL, SOCK_SEQPACKET, 0, sock);
97 BUG_ON(ret, "socketpair()");
100 BUG_ON(child == -1, "fork()");
103 ret = close(sock[0]);
104 BUG_ON(ret, "close()");
106 return parent_f(sock[1], smap, child);
109 ret = close(sock[1]);
110 BUG_ON(ret, "close()");
112 return child_f(sock[0], smap, fileno(ftmp));