DISKLABEL(9) OpenBSD Kernel Manual DISKLABEL(9)NAME
disklabel, readdisklabel, writedisklabel, setdisklabel,
bounds_check_with_label - disk label management routines
SYNOPSIS
#include <sys/param.h>
#include <sys/disklabel.h>
char *
readdisklabel(dev_t dev, void (*strat)(struct buf *), struct disklabel
*lp, int spoofonly);
int
writedisklabel(dev_t dev, void (*strat)(struct buf *), struct disklabel
*lp);
int
setdisklabel(struct disklabel *olp, struct disklabel *nlp, u_int
openmask);
int
bounds_check_with_label(struct buf *bp, struct disklabel *lp, int
wlabel);
DESCRIPTION
This collection of routines provides a disklabel management interface to
kernel device drivers. These routines are classified as machine- or
architecture-dependent because of restrictions imposed by the machine
architecture and boot-strapping code on the location of the label, or
because cooperation with other operating systems requires specialized
conversion code.
readdisklabel() attempts to read a disklabel from the device identified
by dev, using the device strategy routine passed in strat. Note that a
buffer structure is required to pass to the strategy routine; it needs to
be acquired and parametrized for the intended I/O operation, and disposed
of when the operation has completed. Some fields in the disklabel passed
in lp may be pre-initialized by the caller in order to meet device driver
requirements for the I/O operation initiated to get to the disklabel data
on the medium. In particular, the field ``d_secsize'', if non-zero, is
used by readdisklabel() to get an appropriately sized buffer to pass to
the device strategy routine. Unspecified fields in lp should be set to
zero. If the medium does not contain a native disklabel that can be read
in directly or spoofonly argument is a true value, If a disk label can
not be found or constructed, a string containing an approximated
description of the failure mode is returned. Otherwise the NULL string
is returned.
writedisklabel() stores disk label information contained in the disk
label structure given by lp on the device identified by dev. Like
readdisklabel(), it acquires and sets up an I/O buffer to pass to the
strategy routine strat. writedisklabel() returns 0 on success and EINVAL
if the disk label specifies invalid or unconvertible values. Otherwise,
any error condition reported by the device strategy routine in the
buffer's ``b_error'' field is returned.
setdisklabel() checks a proposed new disk label passed in nlp for some
amount of basic sanity. This includes a check on attempts to change the
location, or reduce the size, of an existing disk partition that is
currently in use by the system. The current disposition of the disk
partitions is made available through olp and openmask, which provide,
respectively, the existing disk label and a bit mask identifying the
partitions that are currently in use. Failure to pass on ``basic
sanity'', results in a EINVAL return value, while a vetoed update of the
partition layout is signalled by a EBUSY return value. Otherwise, 0 is
returned.
bounds_check_with_label() is used to check whether a device transfer
described by bp to the device identified by dev, is properly contained
within a disk partition of the disk with label lp. If this check fails,
bounds_check_with_label() sets the buffer's ``b_error'' field to EINVAL
and sets the B_ERROR flag in ``b_flags''. If the argument wlabel is
zero, and the transfer is a write operation, a check is done if the
transfer would overwrite (a portion of) the disklabel area on the medium.
If that is the case, EROFS is set in ``b_error'' and the B_ERROR flag is
set in ``b_flags''. Note that wlabel should be set to a non-zero value
if the intended operation is expected to install or update the disk
label. Programs that intend to do so using the raw device interface
should notify the driver by using a DIOCWLABEL ioctl function. A zero
value is returned if any of the bound checks failed or transfer was
attempted exactly at the end of disk partition. Otherwise the value of 1
is returned.
SEE ALSOdisklabel(5), disklabel(8), fdisk(8)OpenBSD 4.9 June 26, 2008 OpenBSD 4.9