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 <machine/clock.h> 39 #include <isa/rtc.h> 40 41 /* 42 * Linux-style /dev/nvram driver 43 * 44 * cmos ram starts at bytes 14 through 128, for a total of 114 bytes. 45 * The driver exposes byte 14 as file offset 0. 46 * 47 * Offsets 2 through 31 are checksummed at offset 32, 33. 48 * In order to avoid the possibility of making the machine unbootable at the 49 * bios level (press F1 to continue!), we refuse to allow writes if we do 50 * not see a pre-existing valid checksum. If the existing sum is invalid, 51 * then presumably we do not know how to make a sum that the bios will accept. 52 */ 53 54 #define NVRAM_FIRST RTC_DIAG /* 14 */ 55 #define NVRAM_LAST 128 56 57 #define CKSUM_FIRST 2 58 #define CKSUM_LAST 31 59 #define CKSUM_MSB 32 60 #define CKSUM_LSB 33 61 62 static d_open_t nvram_open; 63 static d_read_t nvram_read; 64 static d_write_t nvram_write; 65 66 static struct cdev *nvram_dev; 67 68 static struct cdevsw nvram_cdevsw = { 69 .d_version = D_VERSION, 70 .d_flags = D_NEEDGIANT, 71 .d_open = nvram_open, 72 .d_read = nvram_read, 73 .d_write = nvram_write, 74 .d_name = "nvram", 75 }; 76 77 static int 78 nvram_open(struct cdev *dev __unused, int flags, int fmt __unused, 79 struct thread *td) 80 { 81 int error = 0; 82 83 if (flags & FWRITE) 84 error = securelevel_gt(td->td_ucred, 0); 85 86 return (error); 87 } 88 89 static int 90 nvram_read(struct cdev *dev, struct uio *uio, int flags) 91 { 92 int nv_off; 93 u_char v; 94 int error = 0; 95 96 while (uio->uio_resid > 0 && error == 0) { 97 nv_off = uio->uio_offset + NVRAM_FIRST; 98 if (nv_off < NVRAM_FIRST || nv_off >= NVRAM_LAST) 99 return (0); /* Signal EOF */ 100 /* Single byte at a time */ 101 v = rtcin(nv_off); 102 error = uiomove(&v, 1, uio); 103 } 104 return (error); 105 106 } 107 108 static int 109 nvram_write(struct cdev *dev, struct uio *uio, int flags) 110 { 111 int nv_off; 112 u_char v; 113 int error = 0; 114 int i; 115 uint16_t sum; 116 117 /* Assert that we understand the existing checksum first! */ 118 sum = rtcin(NVRAM_FIRST + CKSUM_MSB) << 8 | 119 rtcin(NVRAM_FIRST + CKSUM_LSB); 120 for (i = CKSUM_FIRST; i <= CKSUM_LAST; i++) 121 sum -= rtcin(NVRAM_FIRST + i); 122 if (sum != 0) 123 return (EIO); 124 /* Bring in user data and write */ 125 while (uio->uio_resid > 0 && error == 0) { 126 nv_off = uio->uio_offset + NVRAM_FIRST; 127 if (nv_off < NVRAM_FIRST || nv_off >= NVRAM_LAST) 128 return (0); /* Signal EOF */ 129 /* Single byte at a time */ 130 error = uiomove(&v, 1, uio); 131 writertc(nv_off, v); 132 } 133 /* Recalculate checksum afterwards */ 134 sum = 0; 135 for (i = CKSUM_FIRST; i <= CKSUM_LAST; i++) 136 sum += rtcin(NVRAM_FIRST + i); 137 writertc(NVRAM_FIRST + CKSUM_MSB, sum >> 8); 138 writertc(NVRAM_FIRST + CKSUM_LSB, sum); 139 return (error); 140 } 141 142 static int 143 nvram_modevent(module_t mod __unused, int type, void *data __unused) 144 { 145 switch (type) { 146 case MOD_LOAD: 147 nvram_dev = make_dev(&nvram_cdevsw, 0, 148 UID_ROOT, GID_KMEM, 0640, "nvram"); 149 break; 150 case MOD_UNLOAD: 151 case MOD_SHUTDOWN: 152 destroy_dev(nvram_dev); 153 break; 154 default: 155 return (EOPNOTSUPP); 156 } 157 return (0); 158 } 159 DEV_MODULE(nvram, nvram_modevent, NULL); 160