// SPDX-License-Identifier: GPL-2.0-or-later
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/* fd-based mount test.
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*
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* Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <sys/prctl.h>
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#include <sys/wait.h>
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#include <linux/mount.h>
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#include <linux/unistd.h>
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#define E(x) do { if ((x) == -1) { perror(#x); exit(1); } } while(0)
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static void check_messages(int fd)
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{
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char buf[4096];
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int err, n;
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err = errno;
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for (;;) {
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n = read(fd, buf, sizeof(buf));
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if (n < 0)
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break;
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n -= 2;
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switch (buf[0]) {
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case 'e':
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fprintf(stderr, "Error: %*.*s\n", n, n, buf + 2);
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break;
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case 'w':
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fprintf(stderr, "Warning: %*.*s\n", n, n, buf + 2);
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break;
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case 'i':
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fprintf(stderr, "Info: %*.*s\n", n, n, buf + 2);
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break;
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}
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}
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errno = err;
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}
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static __attribute__((noreturn))
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void mount_error(int fd, const char *s)
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{
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check_messages(fd);
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fprintf(stderr, "%s: %m\n", s);
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exit(1);
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}
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/* Hope -1 isn't a syscall */
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#ifndef __NR_fsopen
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#define __NR_fsopen -1
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#endif
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#ifndef __NR_fsmount
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#define __NR_fsmount -1
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#endif
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#ifndef __NR_fsconfig
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#define __NR_fsconfig -1
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#endif
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#ifndef __NR_move_mount
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#define __NR_move_mount -1
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#endif
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static inline int fsopen(const char *fs_name, unsigned int flags)
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{
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return syscall(__NR_fsopen, fs_name, flags);
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}
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static inline int fsmount(int fsfd, unsigned int flags, unsigned int ms_flags)
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{
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return syscall(__NR_fsmount, fsfd, flags, ms_flags);
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}
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static inline int fsconfig(int fsfd, unsigned int cmd,
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const char *key, const void *val, int aux)
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{
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return syscall(__NR_fsconfig, fsfd, cmd, key, val, aux);
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}
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static inline int move_mount(int from_dfd, const char *from_pathname,
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int to_dfd, const char *to_pathname,
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unsigned int flags)
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{
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return syscall(__NR_move_mount,
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from_dfd, from_pathname,
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to_dfd, to_pathname, flags);
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}
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#define E_fsconfig(fd, cmd, key, val, aux) \
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do { \
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if (fsconfig(fd, cmd, key, val, aux) == -1) \
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mount_error(fd, key ?: "create"); \
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} while (0)
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int main(int argc, char *argv[])
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{
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int fsfd, mfd;
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/* Mount a publically available AFS filesystem */
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fsfd = fsopen("afs", 0);
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if (fsfd == -1) {
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perror("fsopen");
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exit(1);
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}
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E_fsconfig(fsfd, FSCONFIG_SET_STRING, "source", "#grand.central.org:root.cell.", 0);
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E_fsconfig(fsfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0);
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mfd = fsmount(fsfd, 0, MOUNT_ATTR_RDONLY);
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if (mfd < 0)
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mount_error(fsfd, "fsmount");
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E(close(fsfd));
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if (move_mount(mfd, "", AT_FDCWD, "/mnt", MOVE_MOUNT_F_EMPTY_PATH) < 0) {
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perror("move_mount");
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exit(1);
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}
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E(close(mfd));
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exit(0);
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}
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