Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 | // SPDX-License-Identifier: GPL-2.0 /* * Copyright (c) 2018 Dmitry Safonov, Arista Networks * * MAP_POPULATE | MAP_PRIVATE should COW VMA pages. */ #define _GNU_SOURCE #include <errno.h> #include <fcntl.h> #include <sys/mman.h> #include <sys/socket.h> #include <sys/types.h> #include <sys/wait.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #ifndef MMAP_SZ #define MMAP_SZ 4096 #endif #define BUG_ON(condition, description) \ do { \ if (condition) { \ fprintf(stderr, "[FAIL]\t%s:%d\t%s:%s\n", __func__, \ __LINE__, (description), strerror(errno)); \ exit(1); \ } \ } while (0) static int parent_f(int sock, unsigned long *smap, int child) { int status, ret; ret = read(sock, &status, sizeof(int)); BUG_ON(ret <= 0, "read(sock)"); *smap = 0x22222BAD; ret = msync(smap, MMAP_SZ, MS_SYNC); BUG_ON(ret, "msync()"); ret = write(sock, &status, sizeof(int)); BUG_ON(ret <= 0, "write(sock)"); waitpid(child, &status, 0); BUG_ON(!WIFEXITED(status), "child in unexpected state"); return WEXITSTATUS(status); } static int child_f(int sock, unsigned long *smap, int fd) { int ret, buf = 0; smap = mmap(0, MMAP_SZ, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_POPULATE, fd, 0); BUG_ON(smap == MAP_FAILED, "mmap()"); BUG_ON(*smap != 0xdeadbabe, "MAP_PRIVATE | MAP_POPULATE changed file"); ret = write(sock, &buf, sizeof(int)); BUG_ON(ret <= 0, "write(sock)"); ret = read(sock, &buf, sizeof(int)); BUG_ON(ret <= 0, "read(sock)"); BUG_ON(*smap == 0x22222BAD, "MAP_POPULATE didn't COW private page"); BUG_ON(*smap != 0xdeadbabe, "mapping was corrupted"); return 0; } int main(int argc, char **argv) { int sock[2], child, ret; FILE *ftmp; unsigned long *smap; ftmp = tmpfile(); BUG_ON(ftmp == 0, "tmpfile()"); ret = ftruncate(fileno(ftmp), MMAP_SZ); BUG_ON(ret, "ftruncate()"); smap = mmap(0, MMAP_SZ, PROT_READ | PROT_WRITE, MAP_SHARED, fileno(ftmp), 0); BUG_ON(smap == MAP_FAILED, "mmap()"); *smap = 0xdeadbabe; /* Probably unnecessary, but let it be. */ ret = msync(smap, MMAP_SZ, MS_SYNC); BUG_ON(ret, "msync()"); ret = socketpair(PF_LOCAL, SOCK_SEQPACKET, 0, sock); BUG_ON(ret, "socketpair()"); child = fork(); BUG_ON(child == -1, "fork()"); if (child) { ret = close(sock[0]); BUG_ON(ret, "close()"); return parent_f(sock[1], smap, child); } ret = close(sock[1]); BUG_ON(ret, "close()"); return child_f(sock[0], smap, fileno(ftmp)); } |