diff options
Diffstat (limited to 'sys/dev/nvram/nvram.c')
-rw-r--r-- | sys/dev/nvram/nvram.c | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/sys/dev/nvram/nvram.c b/sys/dev/nvram/nvram.c new file mode 100644 index 000000000000..fde9d8850ae5 --- /dev/null +++ b/sys/dev/nvram/nvram.c @@ -0,0 +1,159 @@ +/*- + * Copyright (c) 2007 Peter Wemm + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * $FreeBSD$ + */ + +#include <sys/param.h> +#include <sys/systm.h> +#include <sys/kernel.h> +#include <sys/conf.h> +#include <sys/fcntl.h> +#include <sys/proc.h> +#include <sys/uio.h> +#include <sys/module.h> + +#include <machine/clock.h> +#include <isa/rtc.h> + +/* + * Linux-style /dev/nvram driver + * + * cmos ram starts at bytes 14 through 128, for a total of 114 bytes. + * The driver exposes byte 14 as file offset 0. + * + * Offsets 2 through 31 are checksummed at offset 32, 33. + * In order to avoid the possibility of making the machine unbootable at the + * bios level (press F1 to continue!), we refuse to allow writes if we do + * not see a pre-existing valid checksum. If the existing sum is invalid, + * then presumably we do not know how to make a sum that the bios will accept. + */ + +#define NVRAM_FIRST RTC_DIAG /* 14 */ +#define NVRAM_LAST 128 + +#define CKSUM_FIRST 2 +#define CKSUM_LAST 31 +#define CKSUM_MSB 32 +#define CKSUM_LSB 33 + +static d_open_t nvram_open; +static d_read_t nvram_read; +static d_write_t nvram_write; + +static struct cdev *nvram_dev; + +static struct cdevsw nvram_cdevsw = { + .d_version = D_VERSION, + .d_flags = D_NEEDGIANT, + .d_open = nvram_open, + .d_read = nvram_read, + .d_write = nvram_write, + .d_name = "nvram", +}; + +static int +nvram_open(struct cdev *dev __unused, int flags, int fmt __unused, + struct thread *td) +{ + int error = 0; + + if (flags & FWRITE) + error = securelevel_gt(td->td_ucred, 0); + + return (error); +} + +static int +nvram_read(struct cdev *dev, struct uio *uio, int flags) +{ + int nv_off; + u_char v; + int error = 0; + + while (uio->uio_resid > 0 && error == 0) { + nv_off = uio->uio_offset + NVRAM_FIRST; + if (nv_off < NVRAM_FIRST || nv_off >= NVRAM_LAST) + return (0); /* Signal EOF */ + /* Single byte at a time */ + v = rtcin(nv_off); + error = uiomove(&v, 1, uio); + } + return (error); + +} + +static int +nvram_write(struct cdev *dev, struct uio *uio, int flags) +{ + int nv_off; + u_char v; + int error = 0; + int i; + uint16_t sum; + + /* Assert that we understand the existing checksum first! */ + sum = rtcin(NVRAM_FIRST + CKSUM_MSB) << 8 | + rtcin(NVRAM_FIRST + CKSUM_LSB); + for (i = CKSUM_FIRST; i <= CKSUM_LAST; i++) + sum -= rtcin(NVRAM_FIRST + i); + if (sum != 0) + return (EIO); + /* Bring in user data and write */ + while (uio->uio_resid > 0 && error == 0) { + nv_off = uio->uio_offset + NVRAM_FIRST; + if (nv_off < NVRAM_FIRST || nv_off >= NVRAM_LAST) + return (0); /* Signal EOF */ + /* Single byte at a time */ + error = uiomove(&v, 1, uio); + writertc(nv_off, v); + } + /* Recalculate checksum afterwards */ + sum = 0; + for (i = CKSUM_FIRST; i <= CKSUM_LAST; i++) + sum += rtcin(NVRAM_FIRST + i); + writertc(NVRAM_FIRST + CKSUM_MSB, sum >> 8); + writertc(NVRAM_FIRST + CKSUM_LSB, sum); + return (error); +} + +static int +nvram_modevent(module_t mod __unused, int type, void *data __unused) +{ + switch (type) { + case MOD_LOAD: + nvram_dev = make_dev(&nvram_cdevsw, 0, + UID_ROOT, GID_KMEM, 0640, "nvram"); + break; + case MOD_UNLOAD: + case MOD_SHUTDOWN: + destroy_dev(nvram_dev); + break; + default: + return (EOPNOTSUPP); + } + return (0); +} +DEV_MODULE(nvram, nvram_modevent, NULL); |