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| 1 | +/* fd-based mount test. |
| 2 | + * |
| 3 | + * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved. |
| 4 | + * Written by David Howells ([email protected]) |
| 5 | + * |
| 6 | + * This program is free software; you can redistribute it and/or |
| 7 | + * modify it under the terms of the GNU General Public Licence |
| 8 | + * as published by the Free Software Foundation; either version |
| 9 | + * 2 of the Licence, or (at your option) any later version. |
| 10 | + */ |
| 11 | + |
| 12 | +#include <stdio.h> |
| 13 | +#include <stdlib.h> |
| 14 | +#include <unistd.h> |
| 15 | +#include <errno.h> |
| 16 | +#include <fcntl.h> |
| 17 | +#include <sys/prctl.h> |
| 18 | +#include <sys/wait.h> |
| 19 | +#include <linux/mount.h> |
| 20 | +#include <linux/unistd.h> |
| 21 | + |
| 22 | +#define E(x) do { if ((x) == -1) { perror(#x); exit(1); } } while(0) |
| 23 | + |
| 24 | +static void check_messages(int fd) |
| 25 | +{ |
| 26 | + char buf[4096]; |
| 27 | + int err, n; |
| 28 | + |
| 29 | + err = errno; |
| 30 | + |
| 31 | + for (;;) { |
| 32 | + n = read(fd, buf, sizeof(buf)); |
| 33 | + if (n < 0) |
| 34 | + break; |
| 35 | + n -= 2; |
| 36 | + |
| 37 | + switch (buf[0]) { |
| 38 | + case 'e': |
| 39 | + fprintf(stderr, "Error: %*.*s\n", n, n, buf + 2); |
| 40 | + break; |
| 41 | + case 'w': |
| 42 | + fprintf(stderr, "Warning: %*.*s\n", n, n, buf + 2); |
| 43 | + break; |
| 44 | + case 'i': |
| 45 | + fprintf(stderr, "Info: %*.*s\n", n, n, buf + 2); |
| 46 | + break; |
| 47 | + } |
| 48 | + } |
| 49 | + |
| 50 | + errno = err; |
| 51 | +} |
| 52 | + |
| 53 | +static __attribute__((noreturn)) |
| 54 | +void mount_error(int fd, const char *s) |
| 55 | +{ |
| 56 | + check_messages(fd); |
| 57 | + fprintf(stderr, "%s: %m\n", s); |
| 58 | + exit(1); |
| 59 | +} |
| 60 | + |
| 61 | +/* Hope -1 isn't a syscall */ |
| 62 | +#ifndef __NR_fsopen |
| 63 | +#define __NR_fsopen -1 |
| 64 | +#endif |
| 65 | +#ifndef __NR_fsmount |
| 66 | +#define __NR_fsmount -1 |
| 67 | +#endif |
| 68 | +#ifndef __NR_fsconfig |
| 69 | +#define __NR_fsconfig -1 |
| 70 | +#endif |
| 71 | +#ifndef __NR_move_mount |
| 72 | +#define __NR_move_mount -1 |
| 73 | +#endif |
| 74 | + |
| 75 | + |
| 76 | +static inline int fsopen(const char *fs_name, unsigned int flags) |
| 77 | +{ |
| 78 | + return syscall(__NR_fsopen, fs_name, flags); |
| 79 | +} |
| 80 | + |
| 81 | +static inline int fsmount(int fsfd, unsigned int flags, unsigned int ms_flags) |
| 82 | +{ |
| 83 | + return syscall(__NR_fsmount, fsfd, flags, ms_flags); |
| 84 | +} |
| 85 | + |
| 86 | +static inline int fsconfig(int fsfd, unsigned int cmd, |
| 87 | + const char *key, const void *val, int aux) |
| 88 | +{ |
| 89 | + return syscall(__NR_fsconfig, fsfd, cmd, key, val, aux); |
| 90 | +} |
| 91 | + |
| 92 | +static inline int move_mount(int from_dfd, const char *from_pathname, |
| 93 | + int to_dfd, const char *to_pathname, |
| 94 | + unsigned int flags) |
| 95 | +{ |
| 96 | + return syscall(__NR_move_mount, |
| 97 | + from_dfd, from_pathname, |
| 98 | + to_dfd, to_pathname, flags); |
| 99 | +} |
| 100 | + |
| 101 | +#define E_fsconfig(fd, cmd, key, val, aux) \ |
| 102 | + do { \ |
| 103 | + if (fsconfig(fd, cmd, key, val, aux) == -1) \ |
| 104 | + mount_error(fd, key ?: "create"); \ |
| 105 | + } while (0) |
| 106 | + |
| 107 | +int main(int argc, char *argv[]) |
| 108 | +{ |
| 109 | + int fsfd, mfd; |
| 110 | + |
| 111 | + /* Mount a publically available AFS filesystem */ |
| 112 | + fsfd = fsopen("afs", 0); |
| 113 | + if (fsfd == -1) { |
| 114 | + perror("fsopen"); |
| 115 | + exit(1); |
| 116 | + } |
| 117 | + |
| 118 | + E_fsconfig(fsfd, FSCONFIG_SET_STRING, "source", "#grand.central.org:root.cell.", 0); |
| 119 | + E_fsconfig(fsfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0); |
| 120 | + |
| 121 | + mfd = fsmount(fsfd, 0, MOUNT_ATTR_RDONLY); |
| 122 | + if (mfd < 0) |
| 123 | + mount_error(fsfd, "fsmount"); |
| 124 | + E(close(fsfd)); |
| 125 | + |
| 126 | + if (move_mount(mfd, "", AT_FDCWD, "/mnt", MOVE_MOUNT_F_EMPTY_PATH) < 0) { |
| 127 | + perror("move_mount"); |
| 128 | + exit(1); |
| 129 | + } |
| 130 | + |
| 131 | + E(close(mfd)); |
| 132 | + exit(0); |
| 133 | +} |
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