Copyright (c) 2004 Tom Rhodes
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.Dd December 13, 2004 .Dt KERNEL_MOUNT 9 .Os .Sh NAME .Nm free_mntarg , .Nm kernel_mount , .Nm kernel_vmount , .Nm mount_arg , .Nm mount_argb , .Nm mount_argf , .Nm mount_argsu .Nd "functions provided as part of the kernel mount interface" .Sh SYNOPSIS .Ft void .Fn free_mntarg "struct mntarg *ma" .Ft int .Fn kernel_mount "struct mntarg *ma" "int flags" .Ft int .Fn kernel_vmount "int flags" ... .Ft "struct mntarg *" .Fo mount_arg .Fa "struct mntarg *ma" "const char *name" "const void *val" "int len" .Fc .Ft "struct mntarg *" .Fn mount_argb "struct mntarg *ma" "int flag" "const char *name" .Ft "struct mntarg *" .Fn mount_argf "struct mntarg *ma" "const char *name" "const char *fmt" ... .Ft "struct mntarg *" .Fo mount_argsu .Fa "struct mntarg *ma" "const char *name" "const void *val" "int len" .Fc .Sh DESCRIPTION The .Fn kernel_mount family of functions are provided as an API for building a list of mount arguments which will be used to mount file systems from inside the kernel. By accumulating a list of arguments, the API takes shape and provides the information necessary for the kernel to control the .Xr mount 8 utility. When an error occurs, the process will stop. This will not cause a .Xr panic 9 .
p The header of the structure is stored in
a src/sys/kern/vfs_mount.c which permits automatic structure creation to ease the mount process. Memory allocation must always be freed when the entire process is complete, it is an error otherwise.
p The .Fn free_mntarg function is used to free or clear the .Vt mntarg structure.
p The .Fn kernel_mount function pulls information from the structure to perform the mount request on a given file system. Additionally, the .Fn kernel_mount function always calls the .Fn free_mntarg function. If .Fa ma contains any error code generated during the construction, that code will be called and the file system mount will not be attempted.
p The .Fn kernel_vmount is a function similar to .Xr printf 9 which is used to mount a file system.
p The .Fn mount_arg function takes a plain argument and crafts parts of the structure with regards to various mount options. If the length is a value less than 0, .Xr strlen 3 is used. This argument will be referenced until either .Fn free_mntarg or .Fn kernel_mount is called.
p The .Fn mount_argb function is used to add boolean arguments to the structure. The .Fa flag is the boolean value and .Fa name must start with .Qq Li no , otherwise a panic will occur.
p The .Fn mount_argf function adds .Xr printf 9 style arguments to the current structure.
p The .Fn mount_argsu function will add arguments to the structure from a userland string. .Sh EXAMPLES An example of the .Fn *_cmount function: d -literal static int msdosfs_cmount(struct mntarg *ma, void *data, int flags, struct thread *td) { struct msdosfs_args args; int error; if (data == NULL) return (EINVAL); error = copyin(data, &args, sizeof(args)); if (error) return (error); ma = mount_argsu(ma, "from", args.fspec, MAXPATHLEN); ma = mount_arg(ma, "export", &args.export, sizeof(args.export)); ma = mount_argf(ma, "uid", "%d", args.uid); ma = mount_argf(ma, "gid", "%d", args.gid); ma = mount_argf(ma, "mask", "%d", args.mask); ma = mount_argf(ma, "dirmask", "%d", args.dirmask); ma = mount_argb(ma, args.flags & MSDOSFSMNT_SHORTNAME, "noshortname"); ma = mount_argb(ma, args.flags & MSDOSFSMNT_LONGNAME, "nolongname"); ma = mount_argb(ma, !(args.flags & MSDOSFSMNT_NOWIN95), "nowin95"); ma = mount_argb(ma, args.flags & MSDOSFSMNT_KICONV, "nokiconv"); ma = mount_argsu(ma, "cs_win", args.cs_win, MAXCSLEN); ma = mount_argsu(ma, "cs_dos", args.cs_dos, MAXCSLEN); ma = mount_argsu(ma, "cs_local", args.cs_local, MAXCSLEN); error = kernel_mount(ma, flags); return (error); } .Ed
p When working with .Fn kernel_vmount , .Fa varargs must come in pairs, e.g., rq Va name , value . d -literal error = kernel_vmount( MNT_RDONLY, "fstype", vfsname, "fspath", "/", "from", path, NULL); .Ed .Sh SEE ALSO .Xr VFS 9 , .Xr VFS_MOUNT 9 .Sh HISTORY The .Fn kernel_mount family of functions and this manual page first appeared in .Fx 6.0 . .Sh AUTHORS .An -nosplit The .Fn kernel_mount family of functions and API was developed by .An Poul-Henning Kamp Aq phk@FreeBSD.org . This manual page was written by .An Tom Rhodes Aq trhodes@FreeBSD.org .