LXR linux/tools/testing/selftests/vm/map

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Copyright (c) 2018 Dmitry Safonov, Arista Networks
   4 *
   5 * MAP_POPULATE | MAP_PRIVATE should COW VMA pages.
   6 */
   7
   8#define _GNU_SOURCE
   9#include <errno.h>
  10#include <fcntl.h>
  11#include <sys/mman.h>
  12#include <sys/socket.h>
  13#include <sys/types.h>
  14#include <sys/wait.h>
  15#include <stdio.h>
  16#include <stdlib.h>
  17#include <string.h>
  18#include <unistd.h>
  19
  20#ifndef MMAP_SZ
  21#define MMAP_SZ         4096
  22#endif
  23
  24#define BUG_ON(condition, description)                                  \
  25        do {                                                            \
  26                if (condition) {                                        \
  27                        fprintf(stderr, "[FAIL]\t%s:%d\t%s:%s\n", __func__, \
  28                                __LINE__, (description), strerror(errno)); \
  29                        exit(1);                                        \
  30                }                                                       \
  31        } while (0)
  32
  33static int parent_f(int sock, unsigned long *smap, int child)
  34{
  35        int status, ret;
  36
  37        ret = read(sock, &status, sizeof(int));
  38        BUG_ON(ret <= 0, "read(sock)");
  39
  40        *smap = 0x22222BAD;
  41        ret = msync(smap, MMAP_SZ, MS_SYNC);
  42        BUG_ON(ret, "msync()");
  43
  44        ret = write(sock, &status, sizeof(int));
  45        BUG_ON(ret <= 0, "write(sock)");
  46
  47        waitpid(child, &status, 0);
  48        BUG_ON(!WIFEXITED(status), "child in unexpected state");
  49
  50        return WEXITSTATUS(status);
  51}
  52
  53static int child_f(int sock, unsigned long *smap, int fd)
  54{
  55        int ret, buf = 0;
  56
  57        smap = mmap(0, MMAP_SZ, PROT_READ | PROT_WRITE,
  58                        MAP_PRIVATE | MAP_POPULATE, fd, 0);
  59        BUG_ON(smap == MAP_FAILED, "mmap()");
  60
  61        BUG_ON(*smap != 0xdeadbabe, "MAP_PRIVATE | MAP_POPULATE changed file");
  62
  63        ret = write(sock, &buf, sizeof(int));
  64        BUG_ON(ret <= 0, "write(sock)");
  65
  66        ret = read(sock, &buf, sizeof(int));
  67        BUG_ON(ret <= 0, "read(sock)");
  68
  69        BUG_ON(*smap == 0x22222BAD, "MAP_POPULATE didn't COW private page");
  70        BUG_ON(*smap != 0xdeadbabe, "mapping was corrupted");
  71
  72        return 0;
  73}
  74
  75int main(int argc, char **argv)
  76{
  77        int sock[2], child, ret;
  78        FILE *ftmp;
  79        unsigned long *smap;
  80
  81        ftmp = tmpfile();
  82        BUG_ON(ftmp == 0, "tmpfile()");
  83
  84        ret = ftruncate(fileno(ftmp), MMAP_SZ);
  85        BUG_ON(ret, "ftruncate()");
  86
  87        smap = mmap(0, MMAP_SZ, PROT_READ | PROT_WRITE,
  88                        MAP_SHARED, fileno(ftmp), 0);
  89        BUG_ON(smap == MAP_FAILED, "mmap()");
  90
  91        *smap = 0xdeadbabe;
  92        /* Probably unnecessary, but let it be. */
  93        ret = msync(smap, MMAP_SZ, MS_SYNC);
  94        BUG_ON(ret, "msync()");
  95
  96        ret = socketpair(PF_LOCAL, SOCK_SEQPACKET, 0, sock);
  97        BUG_ON(ret, "socketpair()");
  98
  99        child = fork();
 100        BUG_ON(child == -1, "fork()");
 101
 102        if (child) {
 103                ret = close(sock[0]);
 104                BUG_ON(ret, "close()");
 105
 106                return parent_f(sock[1], smap, child);
 107        }
 108
 109        ret = close(sock[1]);
 110        BUG_ON(ret, "close()");
 111
 112        return child_f(sock[0], smap, fileno(ftmp));
 113}
 114