1 /* $NetBSD: mapper.c,v 1.2 2020/01/30 07:58:33 kamil 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 1.2 2020/01/30 07:58:33 kamil 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.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