Introduce a diskmap pseudo device which allows userland to open a disk

specified via its disklabel UID. The mapping from the disklabel UID to the
real disk and the opening of the resulting device is performed atomically
using a single ioctl.

ok krw@ deraadt@

1 files changed, 152 insertions, 0 deletions

diff --git a/sys/dev/diskmap.c b/sys/dev/diskmap.c
new file mode 100644
index 00000000000..cf5951a6e1d
--- /dev/null
+++ b/sys/dev/diskmap.c
@@ -0,0 +1,152 @@
+/*	$OpenBSD: diskmap.c,v 1.1 2010/06/08 12:46:49 jsing Exp $	*/
+
+/*
+ * Copyright (c) 2009, 2010 Joel Sing <jsing@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * Disk mapper.
+ */
+
+#include <sys/param.h>
+#include <sys/types.h>
+#include <sys/systm.h>
+#include <sys/device.h>
+#include <sys/errno.h>
+#include <sys/buf.h>
+#include <sys/conf.h>
+#include <sys/dkio.h>
+#include <sys/disk.h>
+#include <sys/disklabel.h>
+#include <sys/file.h>
+#include <sys/filedesc.h>
+#include <sys/malloc.h>
+#include <sys/namei.h>
+#include <sys/proc.h>
+#include <sys/vnode.h>
+
+int
+diskmapopen(dev_t dev, int flag, int fmt, struct proc *p)
+{
+	return 0;
+}
+
+int
+diskmapclose(dev_t dev, int flag, int fmt, struct proc *p)
+{
+	return 0;
+}
+
+int
+diskmapioctl(dev_t dev, u_long cmd, caddr_t addr, int flag, struct proc *p)
+{
+	struct dk_diskmap *dm;
+	struct nameidata ndp;
+	struct filedesc *fdp;
+	struct file *fp;
+	struct vnode *vp = NULL, *ovp;
+	char *devname;
+	int fd, error = EINVAL;
+
+	if (cmd != DIOCMAP)
+		return EINVAL;
+
+	/*
+	 * Map a request for a disk to the correct device. We should be
+	 * supplied with either a diskname or a disklabel UID.
+	 */
+
+	dm = (struct dk_diskmap *)addr;
+	fd = dm->fd;
+	devname = malloc(PATH_MAX, M_DEVBUF, M_WAITOK);
+	if (copyinstr(dm->device, devname, PATH_MAX, NULL))
+		goto invalid;
+	if (disk_map(devname, devname, PATH_MAX, dm->flags) == 0)
+		if (copyoutstr(devname, dm->device, PATH_MAX, NULL))
+			goto invalid;
+
+	/* Attempt to open actual device. */
+	fdp = p->p_fd;
+	fdplock(fdp);
+
+	if ((u_int)fd >= fdp->fd_nfiles || (fp = fdp->fd_ofiles[fd]) == NULL) {
+		error = EINVAL;
+		goto bad;
+	}
+
+	if (FILE_IS_USABLE(fp) == NULL) {
+		error = EINVAL;
+		goto bad;
+	}
+
+	NDINIT(&ndp, LOOKUP, NOFOLLOW | LOCKLEAF | SAVENAME, UIO_SYSSPACE,
+	    devname, p);
+
+	if ((error = vn_open(&ndp, fp->f_flag, 0)) != 0)
+		goto bad;
+
+	vp = ndp.ni_vp;
+
+	/* Close the original vnode. */
+	ovp = (struct vnode *)fp->f_data;
+	if (fp->f_flag & FWRITE)
+		ovp->v_writecount--;
+
+	if (ovp->v_writecount == 0) {
+		vn_lock(ovp, LK_EXCLUSIVE | LK_RETRY, p);
+		VOP_CLOSE(ovp, fp->f_flag, p->p_ucred, p);
+		vput(ovp);
+	}
+
+	fp->f_type = DTYPE_VNODE;
+	fp->f_ops = &vnops;
+	fp->f_data = (caddr_t)vp;
+	fp->f_offset = 0;
+	fp->f_rxfer = 0;
+	fp->f_wxfer = 0;
+	fp->f_seek = 0;
+	fp->f_rbytes = 0;
+	fp->f_wbytes = 0;
+
+	VOP_UNLOCK(vp, 0, p);
+
+	fdpunlock(fdp);
+
+	return 0;
+
+bad:
+	if (vp)
+		vput(vp);
+
+	fdpunlock(fdp);
+
+invalid:
+	if (devname)
+		free(devname, M_DEVBUF);
+
+	return (error);
+}
+
+int
+diskmapread(dev_t dev, struct uio *uio, int flag)
+{
+	return ENXIO;
+}
+
+int
+diskmapwrite(dev_t dev, struct uio *uio, int flag)
+{
+	return ENXIO;
+}