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      1 /*	$NetBSD: mapper.c,v 1.4 2020/09/06 02:18:53 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2019 The NetBSD Foundation, Inc.
      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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #include <sys/cdefs.h>
     30 __KERNEL_RCSID(0, "$NetBSD: mapper.c,v 1.4 2020/09/06 02:18:53 riastradh Exp $");
     31 
     32 #include <sys/param.h>
     33 #include <sys/conf.h>
     34 #include <sys/device.h>
     35 #include <sys/kernel.h>
     36 #include <sys/kmem.h>
     37 #include <sys/module.h>
     38 #include <sys/systm.h>
     39 
     40 #include <uvm/uvm_extern.h>
     41 
     42 /*
     43  * Creating a device /dev/mapper for demonstration.
     44  * To use this device you need to do:
     45  * 	mknod /dev/mapper c 351 0
     46  *
     47  */
     48 
     49 dev_type_open(mapper_open);
     50 dev_type_close(mapper_close);
     51 dev_type_mmap(mapper_mmap);
     52 
     53 static struct cdevsw mapper_cdevsw = {
     54 	.d_open = mapper_open,
     55 	.d_close = mapper_close,
     56 	.d_read = noread,
     57 	.d_write = nowrite,
     58 	.d_ioctl = noioctl,
     59 	.d_stop = nostop,
     60 	.d_tty = notty,
     61 	.d_poll = nopoll,
     62 	.d_mmap = mapper_mmap,
     63 	.d_kqfilter = nokqfilter,
     64 	.d_discard = nodiscard,
     65 	.d_flag = D_OTHER
     66 };
     67 
     68 struct mapper_softc {
     69 	int refcnt;
     70 	char *buffer;
     71 };
     72 
     73 static struct mapper_softc sc;
     74 
     75 int
     76 mapper_open(dev_t self __unused, int flag __unused, int mode __unused,
     77            struct lwp *l __unused)
     78 {
     79 	if (sc.refcnt > 0)
     80 		return EBUSY;
     81 	++sc.refcnt;
     82 	sc.buffer = kmem_zalloc(PAGE_SIZE, KM_SLEEP);
     83 	snprintf(sc.buffer, PAGE_SIZE, "Hey There!");
     84 	return 0;
     85 }
     86 
     87 int
     88 mapper_close(dev_t self __unused, int flag __unused, int mode __unused,
     89             struct lwp *l __unused)
     90 {
     91 	kmem_free(sc.buffer, PAGE_SIZE);
     92 	--sc.refcnt;
     93 	return 0;
     94 }
     95 
     96 /*
     97  * Here, pmap_extract() is used to extract the mapping from the specified
     98  * physical map for the provided virtual address, where pmap_kernel() points
     99  * to the kernel pmap.
    100  */
    101 
    102 paddr_t
    103 mapper_mmap(dev_t dev, off_t off, int prot)
    104 {
    105 	paddr_t pa;
    106 
    107 	if (off & PAGE_MASK)
    108 		return (paddr_t)-1;
    109 	if (prot != VM_PROT_READ)
    110 		return (paddr_t)-1;
    111 	if (pmap_extract(pmap_kernel(), (vaddr_t)sc.buffer, &pa))
    112 		return (paddr_t)atop(pa);
    113 
    114 	return (paddr_t)-1;
    115 }
    116 
    117 MODULE(MODULE_CLASS_MISC, mapper, NULL);
    118 
    119 static int
    120 mapper_modcmd(modcmd_t cmd, void *arg __unused)
    121 {
    122 	/* The major should be verified and changed if needed to avoid
    123 	 * conflicts with other devices. */
    124 	int cmajor = 351, bmajor = -1;
    125 
    126 	switch (cmd) {
    127 	case MODULE_CMD_INIT:
    128 		if (devsw_attach("mapper", NULL, &bmajor, &mapper_cdevsw,
    129 					&cmajor))
    130 			return ENXIO;
    131 		return 0;
    132 	case MODULE_CMD_FINI:
    133 		if (sc.refcnt > 0)
    134 			return EBUSY;
    135 		devsw_detach(NULL, &mapper_cdevsw);
    136 		return 0;
    137 	default:
    138 		return ENOTTY;
    139 	}
    140 	return 0;
    141 }
    142