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