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-rw-r--r--sys/dev/nvram/nvram.c159
1 files changed, 159 insertions, 0 deletions
diff --git a/sys/dev/nvram/nvram.c b/sys/dev/nvram/nvram.c
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+++ b/sys/dev/nvram/nvram.c
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+/*-
+ * 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);