1 /*- 2 * Copyright (c) 2007 Peter Wemm 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 * 26 * $FreeBSD$ 27 */ 28 29 #include <sys/param.h> 30 #include <sys/systm.h> 31 #include <sys/kernel.h> 32 #include <sys/conf.h> 33 #include <sys/fcntl.h> 34 #include <sys/proc.h> 35 #include <sys/uio.h> 36 #include <sys/module.h> 37 38 #include <isa/rtc.h> 39 40 /* 41 * Linux-style /dev/nvram driver 42 * 43 * cmos ram starts at bytes 14 through 128, for a total of 114 bytes. 44 * The driver exposes byte 14 as file offset 0. 45 * 46 * Offsets 2 through 31 are checksummed at offset 32, 33. 47 * In order to avoid the possibility of making the machine unbootable at the 48 * bios level (press F1 to continue!), we refuse to allow writes if we do 49 * not see a pre-existing valid checksum. If the existing sum is invalid, 50 * then presumably we do not know how to make a sum that the bios will accept. 51 */ 52 53 #define NVRAM_FIRST RTC_DIAG /* 14 */ 54 #define NVRAM_LAST 128 55 56 #define CKSUM_FIRST 2 57 #define CKSUM_LAST 31 58 #define CKSUM_MSB 32 59 #define CKSUM_LSB 33 60 61 static d_open_t nvram_open; 62 static d_read_t nvram_read; 63 static d_write_t nvram_write; 64 65 static struct cdev *nvram_dev; 66 67 static struct cdevsw nvram_cdevsw = { 68 .d_version = D_VERSION, 69 .d_flags = D_NEEDGIANT, 70 .d_open = nvram_open, 71 .d_read = nvram_read, 72 .d_write = nvram_write, 73 .d_name = "nvram", 74 }; 75 76 static int 77 nvram_open(struct cdev *dev __unused, int flags, int fmt __unused, 78 struct thread *td) 79 { 80 int error = 0; 81 82 if (flags & FWRITE) 83 error = securelevel_gt(td->td_ucred, 0); 84 85 return (error); 86 } 87 88 static int 89 nvram_read(struct cdev *dev, struct uio *uio, int flags) 90 { 91 int nv_off; 92 u_char v; 93 int error = 0; 94 95 while (uio->uio_resid > 0 && error == 0) { 96 nv_off = uio->uio_offset + NVRAM_FIRST; 97 if (nv_off < NVRAM_FIRST || nv_off >= NVRAM_LAST) 98 return (0); /* Signal EOF */ 99 /* Single byte at a time */ 100 v = rtcin(nv_off); 101 error = uiomove(&v, 1, uio); 102 } 103 return (error); 104 105 } 106 107 static int 108 nvram_write(struct cdev *dev, struct uio *uio, int flags) 109 { 110 int nv_off; 111 u_char v; 112 int error = 0; 113 int i; 114 uint16_t sum; 115 116 /* Assert that we understand the existing checksum first! */ 117 sum = rtcin(NVRAM_FIRST + CKSUM_MSB) << 8 | 118 rtcin(NVRAM_FIRST + CKSUM_LSB); 119 for (i = CKSUM_FIRST; i <= CKSUM_LAST; i++) 120 sum -= rtcin(NVRAM_FIRST + i); 121 if (sum != 0) 122 return (EIO); 123 /* Bring in user data and write */ 124 while (uio->uio_resid > 0 && error == 0) { 125 nv_off = uio->uio_offset + NVRAM_FIRST; 126 if (nv_off < NVRAM_FIRST || nv_off >= NVRAM_LAST) 127 return (0); /* Signal EOF */ 128 /* Single byte at a time */ 129 error = uiomove(&v, 1, uio); 130 writertc(nv_off, v); 131 } 132 /* Recalculate checksum afterwards */ 133 sum = 0; 134 for (i = CKSUM_FIRST; i <= CKSUM_LAST; i++) 135 sum += rtcin(NVRAM_FIRST + i); 136 writertc(NVRAM_FIRST + CKSUM_MSB, sum >> 8); 137 writertc(NVRAM_FIRST + CKSUM_LSB, sum); 138 return (error); 139 } 140 141 static int 142 nvram_modevent(module_t mod __unused, int type, void *data __unused) 143 { 144 switch (type) { 145 case MOD_LOAD: 146 nvram_dev = make_dev(&nvram_cdevsw, 0, 147 UID_ROOT, GID_KMEM, 0640, "nvram"); 148 break; 149 case MOD_UNLOAD: 150 case MOD_SHUTDOWN: 151 destroy_dev(nvram_dev); 152 break; 153 default: 154 return (EOPNOTSUPP); 155 } 156 return (0); 157 } 158 DEV_MODULE(nvram, nvram_modevent, NULL); 159