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samples/vfs/test-fsmount.c
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// SPDX-License-Identifier: GPL-2.0-or-later |
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/* fd-based mount test. * * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) |
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*/ #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, buf + 2); break; case 'w': fprintf(stderr, "Warning: %*.*s ", n, n, buf + 2); break; case 'i': fprintf(stderr, "Info: %*.*s ", 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 ", 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); } |