From f1b5618e013af28b3c78daf424436a79674423c0 Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 1 Nov 2018 23:36:32 +0000 Subject: vfs: Add a sample program for the new mount API Add a sample program to demonstrate fsopen/fsmount/move_mount to mount something. To make it compile on all arches, irrespective of whether or not syscall numbers are assigned, define the syscall number to -1 if it isn't to cause the kernel to return -ENOSYS. Signed-off-by: David Howells Signed-off-by: Al Viro --- samples/vfs/test-fsmount.c | 133 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 133 insertions(+) create mode 100644 samples/vfs/test-fsmount.c (limited to 'samples/vfs/test-fsmount.c') diff --git a/samples/vfs/test-fsmount.c b/samples/vfs/test-fsmount.c new file mode 100644 index 000000000000..266d72b3dce4 --- /dev/null +++ b/samples/vfs/test-fsmount.c @@ -0,0 +1,133 @@ +/* fd-based mount test. + * + * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public Licence + * as published by the Free Software Foundation; either version + * 2 of the Licence, or (at your option) any later version. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#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); +} -- cgit v1.2.3