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      1 /*	$NetBSD: md.c,v 1.87 2023/01/13 15:46:40 hannken Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1995 Gordon W. Ross, Leo Weppelman.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     26  */
     27 
     28 /*
     29  * This implements a general-purpose memory-disk.
     30  * See md.h for notes on the config types.
     31  *
     32  * Note that this driver provides the same functionality
     33  * as the MFS filesystem hack, but this is better because
     34  * you can use this for any filesystem type you'd like!
     35  *
     36  * Credit for most of the kmem ramdisk code goes to:
     37  *   Leo Weppelman (atari) and Phil Nelson (pc532)
     38  * Credit for the ideas behind the "user space memory" code goes
     39  * to the authors of the MFS implementation.
     40  */
     41 
     42 #include <sys/cdefs.h>
     43 __KERNEL_RCSID(0, "$NetBSD: md.c,v 1.87 2023/01/13 15:46:40 hannken Exp $");
     44 
     45 #ifdef _KERNEL_OPT
     46 #include "opt_md.h"
     47 #else
     48 #define MEMORY_DISK_SERVER 1
     49 #endif
     50 
     51 #include <sys/param.h>
     52 #include <sys/kernel.h>
     53 #include <sys/kmem.h>
     54 #include <sys/systm.h>
     55 #include <sys/buf.h>
     56 #include <sys/bufq.h>
     57 #include <sys/device.h>
     58 #include <sys/disk.h>
     59 #include <sys/stat.h>
     60 #include <sys/proc.h>
     61 #include <sys/conf.h>
     62 #include <sys/disklabel.h>
     63 
     64 #include <uvm/uvm_extern.h>
     65 
     66 #include <dev/md.h>
     67 
     68 #include "ioconf.h"
     69 /*
     70  * The user-space functionality is included by default.
     71  * Use  `options MEMORY_DISK_SERVER=0' to turn it off.
     72  */
     73 #ifndef MEMORY_DISK_SERVER
     74 #error MEMORY_DISK_SERVER should be defined by opt_md.h
     75 #endif	/* MEMORY_DISK_SERVER */
     76 
     77 /*
     78  * We should use the raw partition for ioctl.
     79  */
     80 #define MD_UNIT(unit)	DISKUNIT(unit)
     81 
     82 /* autoconfig stuff... */
     83 
     84 struct md_softc {
     85 	device_t sc_dev;	/* Self. */
     86 	struct disk sc_dkdev;	/* hook for generic disk handling */
     87 	struct md_conf sc_md;
     88 	kmutex_t sc_lock;	/* Protect self. */
     89 	kcondvar_t sc_cv;	/* Wait here for work. */
     90 	struct bufq_state *sc_buflist;
     91 };
     92 /* shorthand for fields in sc_md: */
     93 #define sc_addr sc_md.md_addr
     94 #define sc_size sc_md.md_size
     95 #define sc_type sc_md.md_type
     96 
     97 static void	md_attach(device_t, device_t, void *);
     98 static int	md_detach(device_t, int);
     99 
    100 static dev_type_open(mdopen);
    101 static dev_type_close(mdclose);
    102 static dev_type_read(mdread);
    103 static dev_type_write(mdwrite);
    104 static dev_type_ioctl(mdioctl);
    105 static dev_type_strategy(mdstrategy);
    106 static dev_type_size(mdsize);
    107 
    108 const struct bdevsw md_bdevsw = {
    109 	.d_open = mdopen,
    110 	.d_close = mdclose,
    111 	.d_strategy = mdstrategy,
    112 	.d_ioctl = mdioctl,
    113 	.d_dump = nodump,
    114 	.d_psize = mdsize,
    115 	.d_discard = nodiscard,
    116 	.d_flag = D_DISK | D_MPSAFE
    117 };
    118 
    119 const struct cdevsw md_cdevsw = {
    120 	.d_open = mdopen,
    121 	.d_close = mdclose,
    122 	.d_read = mdread,
    123 	.d_write = mdwrite,
    124 	.d_ioctl = mdioctl,
    125 	.d_stop = nostop,
    126 	.d_tty = notty,
    127 	.d_poll = nopoll,
    128 	.d_mmap = nommap,
    129 	.d_kqfilter = nokqfilter,
    130 	.d_discard = nodiscard,
    131 	.d_flag = D_DISK | D_MPSAFE
    132 };
    133 
    134 static const struct dkdriver mddkdriver = {
    135 	.d_strategy = mdstrategy,
    136 	.d_minphys = minphys
    137 };
    138 
    139 CFATTACH_DECL3_NEW(md, sizeof(struct md_softc),
    140 	0, md_attach, md_detach, NULL, NULL, NULL, DVF_DETACH_SHUTDOWN);
    141 
    142 static kmutex_t md_device_lock;		/* Protect unit creation / deletion. */
    143 extern size_t md_root_size;
    144 
    145 static void md_set_disklabel(struct md_softc *);
    146 
    147 /*
    148  * This is called if we are configured as a pseudo-device
    149  */
    150 void
    151 mdattach(int n)
    152 {
    153 
    154 	mutex_init(&md_device_lock, MUTEX_DEFAULT, IPL_NONE);
    155 	if (config_cfattach_attach(md_cd.cd_name, &md_ca)) {
    156 		aprint_error("%s: cfattach_attach failed\n", md_cd.cd_name);
    157 		return;
    158 	}
    159 }
    160 
    161 static void
    162 md_attach(device_t parent, device_t self, void *aux)
    163 {
    164 	struct md_softc *sc = device_private(self);
    165 
    166 	sc->sc_dev = self;
    167 	sc->sc_type = MD_UNCONFIGURED;
    168 	mutex_init(&sc->sc_lock, MUTEX_DEFAULT, IPL_NONE);
    169 	cv_init(&sc->sc_cv, "mdidle");
    170 	bufq_alloc(&sc->sc_buflist, "fcfs", 0);
    171 
    172 	/* XXX - Could accept aux info here to set the config. */
    173 #ifdef	MEMORY_DISK_HOOKS
    174 	/*
    175 	 * This external function might setup a pre-loaded disk.
    176 	 * All it would need to do is setup the md_conf struct.
    177 	 * See sys/dev/md_root.c for an example.
    178 	 */
    179 	md_attach_hook(device_unit(self), &sc->sc_md);
    180 #endif
    181 
    182 	/*
    183 	 * Initialize and attach the disk structure.
    184 	 */
    185 	disk_init(&sc->sc_dkdev, device_xname(self), &mddkdriver);
    186 	disk_attach(&sc->sc_dkdev);
    187 
    188 	if (sc->sc_type != MD_UNCONFIGURED)
    189 		md_set_disklabel(sc);
    190 
    191 	if (!pmf_device_register(self, NULL, NULL))
    192 		aprint_error_dev(self, "couldn't establish power handler\n");
    193 }
    194 
    195 static int
    196 md_detach(device_t self, int flags)
    197 {
    198 	struct md_softc *sc = device_private(self);
    199 	int rc;
    200 
    201 	rc = 0;
    202 	mutex_enter(&sc->sc_dkdev.dk_openlock);
    203 	if (sc->sc_dkdev.dk_openmask == 0 && sc->sc_type == MD_UNCONFIGURED)
    204 		;	/* nothing to do */
    205 	else if ((flags & DETACH_FORCE) == 0)
    206 		rc = EBUSY;
    207 	mutex_exit(&sc->sc_dkdev.dk_openlock);
    208 
    209 	if (rc != 0)
    210 		return rc;
    211 
    212 	pmf_device_deregister(self);
    213 	disk_detach(&sc->sc_dkdev);
    214 	disk_destroy(&sc->sc_dkdev);
    215 	bufq_free(sc->sc_buflist);
    216 	mutex_destroy(&sc->sc_lock);
    217 	cv_destroy(&sc->sc_cv);
    218 	return 0;
    219 }
    220 
    221 /*
    222  * operational routines:
    223  * open, close, read, write, strategy,
    224  * ioctl, dump, size
    225  */
    226 
    227 #if MEMORY_DISK_SERVER
    228 static int	md_server_loop(struct md_softc *sc);
    229 static int	md_ioctl_server(struct md_softc *sc, struct md_conf *umd,
    230 		    struct lwp *l);
    231 #endif	/* MEMORY_DISK_SERVER */
    232 static int	md_ioctl_kalloc(struct md_softc *sc, struct md_conf *umd,
    233 		    struct lwp *l);
    234 
    235 static int
    236 mdsize(dev_t dev)
    237 {
    238 	struct md_softc *sc;
    239 	int res;
    240 
    241 	sc = device_lookup_private(&md_cd, MD_UNIT(dev));
    242 	if (sc == NULL)
    243 		return 0;
    244 
    245 	mutex_enter(&sc->sc_lock);
    246 	if (sc->sc_type == MD_UNCONFIGURED)
    247 		res = 0;
    248 	else
    249 		res = sc->sc_size >> DEV_BSHIFT;
    250 	mutex_exit(&sc->sc_lock);
    251 
    252 	return res;
    253 }
    254 
    255 static int
    256 mdopen(dev_t dev, int flag, int fmt, struct lwp *l)
    257 {
    258 	int unit;
    259 	int part = DISKPART(dev);
    260 	int pmask = 1 << part;
    261 	cfdata_t cf;
    262 	struct md_softc *sc;
    263 	struct disk *dk;
    264 #ifdef	MEMORY_DISK_HOOKS
    265 	bool configured;
    266 #endif
    267 
    268 	mutex_enter(&md_device_lock);
    269 	unit = MD_UNIT(dev);
    270 	sc = device_lookup_private(&md_cd, unit);
    271 	if (sc == NULL) {
    272 		if (part != RAW_PART) {
    273 			mutex_exit(&md_device_lock);
    274 			return ENXIO;
    275 		}
    276 		cf = kmem_zalloc(sizeof(*cf), KM_SLEEP);
    277 		cf->cf_name = md_cd.cd_name;
    278 		cf->cf_atname = md_cd.cd_name;
    279 		cf->cf_unit = unit;
    280 		cf->cf_fstate = FSTATE_STAR;
    281 		sc = device_private(config_attach_pseudo(cf));
    282 		if (sc == NULL) {
    283 			mutex_exit(&md_device_lock);
    284 			return ENOMEM;
    285 		}
    286 	}
    287 
    288 	dk = &sc->sc_dkdev;
    289 
    290 	/*
    291 	 * The raw partition is used for ioctl to configure.
    292 	 */
    293 	if (part == RAW_PART)
    294 		goto ok;
    295 
    296 #ifdef	MEMORY_DISK_HOOKS
    297 	/* Call the open hook to allow loading the device. */
    298 	configured = (sc->sc_type != MD_UNCONFIGURED);
    299 	md_open_hook(unit, &sc->sc_md);
    300 	/* initialize disklabel if the device is configured in open hook */
    301 	if (!configured && sc->sc_type != MD_UNCONFIGURED)
    302 		md_set_disklabel(sc);
    303 #endif
    304 
    305 	/*
    306 	 * This is a normal, "slave" device, so
    307 	 * enforce initialized.
    308 	 */
    309 	if (sc->sc_type == MD_UNCONFIGURED) {
    310 		mutex_exit(&md_device_lock);
    311 		return ENXIO;
    312 	}
    313 
    314 ok:
    315 	/* XXX duplicates code in dk_open().  Call dk_open(), instead? */
    316 	mutex_enter(&dk->dk_openlock);
    317 	/* Mark our unit as open. */
    318 	switch (fmt) {
    319 	case S_IFCHR:
    320 		dk->dk_copenmask |= pmask;
    321 		break;
    322 	case S_IFBLK:
    323 		dk->dk_bopenmask |= pmask;
    324 		break;
    325 	}
    326 
    327 	dk->dk_openmask = dk->dk_copenmask | dk->dk_bopenmask;
    328 
    329 	mutex_exit(&dk->dk_openlock);
    330 	mutex_exit(&md_device_lock);
    331 	return 0;
    332 }
    333 
    334 static int
    335 mdclose(dev_t dev, int flag, int fmt, struct lwp *l)
    336 {
    337 	int part = DISKPART(dev);
    338 	int pmask = 1 << part;
    339 	int error;
    340 	cfdata_t cf;
    341 	struct md_softc *sc;
    342 	struct disk *dk;
    343 
    344 	sc = device_lookup_private(&md_cd, MD_UNIT(dev));
    345 	if (sc == NULL)
    346 		return ENXIO;
    347 
    348 	dk = &sc->sc_dkdev;
    349 
    350 	mutex_enter(&dk->dk_openlock);
    351 
    352 	switch (fmt) {
    353 	case S_IFCHR:
    354 		dk->dk_copenmask &= ~pmask;
    355 		break;
    356 	case S_IFBLK:
    357 		dk->dk_bopenmask &= ~pmask;
    358 		break;
    359 	}
    360 	dk->dk_openmask = dk->dk_copenmask | dk->dk_bopenmask;
    361 	if (dk->dk_openmask != 0) {
    362 		mutex_exit(&dk->dk_openlock);
    363 		return 0;
    364 	}
    365 
    366 	mutex_exit(&dk->dk_openlock);
    367 
    368 	mutex_enter(&md_device_lock);
    369 	cf = device_cfdata(sc->sc_dev);
    370 	error = config_detach(sc->sc_dev, DETACH_QUIET);
    371 	if (! error)
    372 		kmem_free(cf, sizeof(*cf));
    373 	mutex_exit(&md_device_lock);
    374 	return error;
    375 }
    376 
    377 static int
    378 mdread(dev_t dev, struct uio *uio, int flags)
    379 {
    380 	struct md_softc *sc;
    381 
    382 	sc = device_lookup_private(&md_cd, MD_UNIT(dev));
    383 
    384 	if (sc == NULL || sc->sc_type == MD_UNCONFIGURED)
    385 		return ENXIO;
    386 
    387 	return (physio(mdstrategy, NULL, dev, B_READ, minphys, uio));
    388 }
    389 
    390 static int
    391 mdwrite(dev_t dev, struct uio *uio, int flags)
    392 {
    393 	struct md_softc *sc;
    394 
    395 	sc = device_lookup_private(&md_cd, MD_UNIT(dev));
    396 
    397 	if (sc == NULL || sc->sc_type == MD_UNCONFIGURED)
    398 		return ENXIO;
    399 
    400 	return (physio(mdstrategy, NULL, dev, B_WRITE, minphys, uio));
    401 }
    402 
    403 /*
    404  * Handle I/O requests, either directly, or
    405  * by passing them to the server process.
    406  */
    407 static void
    408 mdstrategy(struct buf *bp)
    409 {
    410 	struct md_softc	*sc;
    411 	void *	addr;
    412 	size_t off, xfer;
    413 	bool is_read;
    414 
    415 	sc = device_lookup_private(&md_cd, MD_UNIT(bp->b_dev));
    416 
    417 	if (sc == NULL || sc->sc_type == MD_UNCONFIGURED) {
    418 		bp->b_error = ENXIO;
    419 		goto done;
    420 	}
    421 
    422 	mutex_enter(&sc->sc_lock);
    423 
    424 	switch (sc->sc_type) {
    425 #if MEMORY_DISK_SERVER
    426 	case MD_UMEM_SERVER:
    427 		/* Just add this job to the server's queue. */
    428 		bufq_put(sc->sc_buflist, bp);
    429 		cv_signal(&sc->sc_cv);
    430 		mutex_exit(&sc->sc_lock);
    431 		/* see md_server_loop() */
    432 		/* no biodone in this case */
    433 		return;
    434 #endif	/* MEMORY_DISK_SERVER */
    435 
    436 	case MD_KMEM_FIXED:
    437 	case MD_KMEM_ALLOCATED:
    438 		/* These are in kernel space.  Access directly. */
    439 		is_read = ((bp->b_flags & B_READ) == B_READ);
    440 		bp->b_resid = bp->b_bcount;
    441 		off = (bp->b_blkno << DEV_BSHIFT);
    442 		if (off >= sc->sc_size) {
    443 			if (is_read)
    444 				break;	/* EOF */
    445 			goto set_eio;
    446 		}
    447 		xfer = bp->b_resid;
    448 		if (xfer > (sc->sc_size - off))
    449 			xfer = (sc->sc_size - off);
    450 		addr = (char *)sc->sc_addr + off;
    451 		disk_busy(&sc->sc_dkdev);
    452 		if (is_read)
    453 			memcpy(bp->b_data, addr, xfer);
    454 		else
    455 			memcpy(addr, bp->b_data, xfer);
    456 		disk_unbusy(&sc->sc_dkdev, xfer, is_read);
    457 		bp->b_resid -= xfer;
    458 		break;
    459 
    460 	default:
    461 		bp->b_resid = bp->b_bcount;
    462 	set_eio:
    463 		bp->b_error = EIO;
    464 		break;
    465 	}
    466 	mutex_exit(&sc->sc_lock);
    467 
    468  done:
    469 
    470 	biodone(bp);
    471 }
    472 
    473 static int
    474 mdioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
    475 {
    476 	struct md_softc *sc;
    477 	struct md_conf *umd;
    478 	int error;
    479 
    480 	if ((sc = device_lookup_private(&md_cd, MD_UNIT(dev))) == NULL)
    481 		return ENXIO;
    482 
    483 	if (sc->sc_type != MD_UNCONFIGURED) {
    484 		error = disk_ioctl(&sc->sc_dkdev, dev, cmd, data, flag, l);
    485 		if (error != EPASSTHROUGH) {
    486 			return error;
    487 		}
    488 	}
    489 
    490 	/* If this is not the raw partition, punt! */
    491 	if (DISKPART(dev) != RAW_PART) {
    492 		return ENOTTY;
    493 	}
    494 
    495 	mutex_enter(&sc->sc_lock);
    496 	umd = (struct md_conf *)data;
    497 	error = EINVAL;
    498 	switch (cmd) {
    499 	case MD_GETCONF:
    500 		*umd = sc->sc_md;
    501 		error = 0;
    502 		break;
    503 
    504 	case MD_SETCONF:
    505 		/* Can only set it once. */
    506 		if (sc->sc_type != MD_UNCONFIGURED)
    507 			break;
    508 		switch (umd->md_type) {
    509 		case MD_KMEM_ALLOCATED:
    510 			error = md_ioctl_kalloc(sc, umd, l);
    511 			break;
    512 #if MEMORY_DISK_SERVER
    513 		case MD_UMEM_SERVER:
    514 			error = md_ioctl_server(sc, umd, l);
    515 			break;
    516 #endif	/* MEMORY_DISK_SERVER */
    517 		default:
    518 			break;
    519 		}
    520 		break;
    521 	}
    522 	mutex_exit(&sc->sc_lock);
    523 	return error;
    524 }
    525 
    526 static void
    527 md_set_disklabel(struct md_softc *sc)
    528 {
    529 	struct disk_geom *dg = &sc->sc_dkdev.dk_geom;
    530 	struct disklabel *lp = sc->sc_dkdev.dk_label;
    531 	struct partition *pp;
    532 
    533 	memset(lp, 0, sizeof(*lp));
    534 
    535 	lp->d_secsize = DEV_BSIZE;
    536 	lp->d_secperunit = sc->sc_size / DEV_BSIZE;
    537 	if (lp->d_secperunit >= (32*64)) {
    538 		lp->d_nsectors = 32;
    539 		lp->d_ntracks = 64;
    540 		lp->d_ncylinders = lp->d_secperunit / (32*64);
    541 	} else {
    542 		lp->d_nsectors = 1;
    543 		lp->d_ntracks = 1;
    544 		lp->d_ncylinders = lp->d_secperunit;
    545 	}
    546 	lp->d_secpercyl = lp->d_ntracks*lp->d_nsectors;
    547 
    548 	strncpy(lp->d_typename, md_cd.cd_name, sizeof(lp->d_typename));
    549 	lp->d_type = DKTYPE_MD;
    550 	strncpy(lp->d_packname, "fictitious", sizeof(lp->d_packname));
    551 	lp->d_rpm = 3600;
    552 	lp->d_interleave = 1;
    553 	lp->d_flags = 0;
    554 
    555 	pp = &lp->d_partitions[0];
    556 	pp->p_offset = 0;
    557 	pp->p_size = lp->d_secperunit;
    558 	pp->p_fstype = FS_BSDFFS;
    559 
    560 	pp = &lp->d_partitions[RAW_PART];
    561 	pp->p_offset = 0;
    562 	pp->p_size = lp->d_secperunit;
    563 	pp->p_fstype = FS_UNUSED;
    564 
    565 	lp->d_npartitions = RAW_PART+1;
    566 	lp->d_magic = DISKMAGIC;
    567 	lp->d_magic2 = DISKMAGIC;
    568 	lp->d_checksum = dkcksum(lp);
    569 
    570 	memset(dg, 0, sizeof(*dg));
    571 
    572 	dg->dg_secsize = lp->d_secsize;
    573 	dg->dg_secperunit = lp->d_secperunit;
    574 	dg->dg_nsectors = lp->d_nsectors;
    575 	dg->dg_ntracks = lp->d_ntracks = 64;
    576 	dg->dg_ncylinders = lp->d_ncylinders;
    577 
    578 	disk_set_info(sc->sc_dev, &sc->sc_dkdev, NULL);
    579 }
    580 
    581 /*
    582  * Handle ioctl MD_SETCONF for (sc_type == MD_KMEM_ALLOCATED)
    583  * Just allocate some kernel memory and return.
    584  */
    585 static int
    586 md_ioctl_kalloc(struct md_softc *sc, struct md_conf *umd,
    587     struct lwp *l)
    588 {
    589 	vaddr_t addr;
    590 	vsize_t size;
    591 
    592 	/* Sanity check the size. */
    593 	size = umd->md_size;
    594 	if (size < DEV_BSIZE || (size % DEV_BSIZE) != 0)
    595 		return EINVAL;
    596 
    597 	mutex_exit(&sc->sc_lock);
    598 
    599 	addr = uvm_km_alloc(kernel_map, size, 0, UVM_KMF_WIRED|UVM_KMF_ZERO);
    600 
    601 	mutex_enter(&sc->sc_lock);
    602 
    603 	if (!addr)
    604 		return ENOMEM;
    605 
    606 	/* If another thread beat us to configure this unit:  fail. */
    607 	if (sc->sc_type != MD_UNCONFIGURED) {
    608 		uvm_km_free(kernel_map, addr, size, UVM_KMF_WIRED);
    609 		return EINVAL;
    610 	}
    611 
    612 	/* This unit is now configured. */
    613 	sc->sc_addr = (void *)addr; 	/* kernel space */
    614 	sc->sc_size = (size_t)size;
    615 	sc->sc_type = MD_KMEM_ALLOCATED;
    616 	md_set_disklabel(sc);
    617 	return 0;
    618 }
    619 
    620 #if MEMORY_DISK_SERVER
    621 
    622 /*
    623  * Handle ioctl MD_SETCONF for (sc_type == MD_UMEM_SERVER)
    624  * Set config, then become the I/O server for this unit.
    625  */
    626 static int
    627 md_ioctl_server(struct md_softc *sc, struct md_conf *umd,
    628     struct lwp *l)
    629 {
    630 	vaddr_t end;
    631 	int error;
    632 
    633 	KASSERT(mutex_owned(&sc->sc_lock));
    634 
    635 	/* Sanity check addr, size. */
    636 	end = (vaddr_t) ((char *)umd->md_addr + umd->md_size);
    637 
    638 	if (
    639 #ifndef _RUMPKERNEL
    640 	    /*
    641 	     * On some architectures (e.g. powerpc) rump kernel provides
    642 	     * "safe" low defaults which make this test fail since malloc
    643 	     * does return higher addresses than the "safe" default.
    644 	     */
    645 	    (end >= VM_MAXUSER_ADDRESS) ||
    646 #endif
    647 	    (end < ((vaddr_t) umd->md_addr)))
    648 		return EINVAL;
    649 
    650 	/* This unit is now configured. */
    651 	sc->sc_addr = umd->md_addr; 	/* user space */
    652 	sc->sc_size = umd->md_size;
    653 	sc->sc_type = MD_UMEM_SERVER;
    654 	md_set_disklabel(sc);
    655 
    656 	/* Become the server daemon */
    657 	error = md_server_loop(sc);
    658 
    659 	/* This server is now going away! */
    660 	sc->sc_type = MD_UNCONFIGURED;
    661 	sc->sc_addr = 0;
    662 	sc->sc_size = 0;
    663 
    664 	return (error);
    665 }
    666 
    667 static int
    668 md_server_loop(struct md_softc *sc)
    669 {
    670 	struct buf *bp;
    671 	void *addr;	/* user space address */
    672 	size_t off;	/* offset into "device" */
    673 	size_t xfer;	/* amount to transfer */
    674 	int error;
    675 	bool is_read;
    676 
    677 	KASSERT(mutex_owned(&sc->sc_lock));
    678 
    679 	for (;;) {
    680 		/* Wait for some work to arrive. */
    681 		while ((bp = bufq_get(sc->sc_buflist)) == NULL) {
    682 			error = cv_wait_sig(&sc->sc_cv, &sc->sc_lock);
    683 			if (error)
    684 				return error;
    685 		}
    686 
    687 		/* Do the transfer to/from user space. */
    688 		mutex_exit(&sc->sc_lock);
    689 		error = 0;
    690 		is_read = ((bp->b_flags & B_READ) == B_READ);
    691 		bp->b_resid = bp->b_bcount;
    692 		off = (bp->b_blkno << DEV_BSHIFT);
    693 		if (off >= sc->sc_size) {
    694 			if (is_read)
    695 				goto done;	/* EOF (not an error) */
    696 			error = EIO;
    697 			goto done;
    698 		}
    699 		xfer = bp->b_resid;
    700 		if (xfer > (sc->sc_size - off))
    701 			xfer = (sc->sc_size - off);
    702 		addr = (char *)sc->sc_addr + off;
    703 		disk_busy(&sc->sc_dkdev);
    704 		if (is_read)
    705 			error = copyin(addr, bp->b_data, xfer);
    706 		else
    707 			error = copyout(bp->b_data, addr, xfer);
    708 		disk_unbusy(&sc->sc_dkdev, (error ? 0 : xfer), is_read);
    709 		if (!error)
    710 			bp->b_resid -= xfer;
    711 
    712 	done:
    713 		if (error) {
    714 			bp->b_error = error;
    715 		}
    716 		biodone(bp);
    717 		mutex_enter(&sc->sc_lock);
    718 	}
    719 }
    720 #endif	/* MEMORY_DISK_SERVER */
    721