linux/drivers/char/nvram.c
H. Peter Anvin a01c780042 nvram: Fix write beyond end condition; prove to gcc copy is safe
In nvram_write, first of all, correctly handle the case where the file
pointer is already beyond the end; we should return EOF in that case.

Second, make the logic a bit more explicit so that gcc can statically
prove that the copy_from_user() is safe.  Once the condition of the
beyond-end filepointer is eliminated, the copy is safe but gcc can't
prove it, causing build failures for i386 allyesconfig.

Third, eliminate the entirely superfluous variable "len", and just use
the passed-in variable "count" instead.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Wim Van Sebroeck <wim@iguana.be>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <tip-*@git.kernel.org>
2009-12-11 15:48:23 -08:00

722 lines
17 KiB
C

/*
* CMOS/NV-RAM driver for Linux
*
* Copyright (C) 1997 Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de>
* idea by and with help from Richard Jelinek <rj@suse.de>
* Portions copyright (c) 2001,2002 Sun Microsystems (thockin@sun.com)
*
* This driver allows you to access the contents of the non-volatile memory in
* the mc146818rtc.h real-time clock. This chip is built into all PCs and into
* many Atari machines. In the former it's called "CMOS-RAM", in the latter
* "NVRAM" (NV stands for non-volatile).
*
* The data are supplied as a (seekable) character device, /dev/nvram. The
* size of this file is dependent on the controller. The usual size is 114,
* the number of freely available bytes in the memory (i.e., not used by the
* RTC itself).
*
* Checksums over the NVRAM contents are managed by this driver. In case of a
* bad checksum, reads and writes return -EIO. The checksum can be initialized
* to a sane state either by ioctl(NVRAM_INIT) (clear whole NVRAM) or
* ioctl(NVRAM_SETCKS) (doesn't change contents, just makes checksum valid
* again; use with care!)
*
* This file also provides some functions for other parts of the kernel that
* want to access the NVRAM: nvram_{read,write,check_checksum,set_checksum}.
* Obviously this can be used only if this driver is always configured into
* the kernel and is not a module. Since the functions are used by some Atari
* drivers, this is the case on the Atari.
*
*
* 1.1 Cesar Barros: SMP locking fixes
* added changelog
* 1.2 Erik Gilling: Cobalt Networks support
* Tim Hockin: general cleanup, Cobalt support
* 1.3 Wim Van Sebroeck: convert PRINT_PROC to seq_file
*/
#define NVRAM_VERSION "1.3"
#include <linux/module.h>
#include <linux/nvram.h>
#define PC 1
#define ATARI 2
/* select machine configuration */
#if defined(CONFIG_ATARI)
# define MACH ATARI
#elif defined(__i386__) || defined(__x86_64__) || defined(__arm__) /* and ?? */
# define MACH PC
#else
# error Cannot build nvram driver for this machine configuration.
#endif
#if MACH == PC
/* RTC in a PC */
#define CHECK_DRIVER_INIT() 1
/* On PCs, the checksum is built only over bytes 2..31 */
#define PC_CKS_RANGE_START 2
#define PC_CKS_RANGE_END 31
#define PC_CKS_LOC 32
#define NVRAM_BYTES (128-NVRAM_FIRST_BYTE)
#define mach_check_checksum pc_check_checksum
#define mach_set_checksum pc_set_checksum
#define mach_proc_infos pc_proc_infos
#endif
#if MACH == ATARI
/* Special parameters for RTC in Atari machines */
#include <asm/atarihw.h>
#include <asm/atariints.h>
#define RTC_PORT(x) (TT_RTC_BAS + 2*(x))
#define CHECK_DRIVER_INIT() (MACH_IS_ATARI && ATARIHW_PRESENT(TT_CLK))
#define NVRAM_BYTES 50
/* On Ataris, the checksum is over all bytes except the checksum bytes
* themselves; these are at the very end */
#define ATARI_CKS_RANGE_START 0
#define ATARI_CKS_RANGE_END 47
#define ATARI_CKS_LOC 48
#define mach_check_checksum atari_check_checksum
#define mach_set_checksum atari_set_checksum
#define mach_proc_infos atari_proc_infos
#endif
/* Note that *all* calls to CMOS_READ and CMOS_WRITE must be done with
* rtc_lock held. Due to the index-port/data-port design of the RTC, we
* don't want two different things trying to get to it at once. (e.g. the
* periodic 11 min sync from time.c vs. this driver.)
*/
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/slab.h>
#include <linux/ioport.h>
#include <linux/fcntl.h>
#include <linux/mc146818rtc.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/spinlock.h>
#include <linux/io.h>
#include <linux/uaccess.h>
#include <linux/smp_lock.h>
#include <asm/system.h>
static DEFINE_SPINLOCK(nvram_state_lock);
static int nvram_open_cnt; /* #times opened */
static int nvram_open_mode; /* special open modes */
#define NVRAM_WRITE 1 /* opened for writing (exclusive) */
#define NVRAM_EXCL 2 /* opened with O_EXCL */
static int mach_check_checksum(void);
static void mach_set_checksum(void);
#ifdef CONFIG_PROC_FS
static void mach_proc_infos(unsigned char *contents, struct seq_file *seq,
void *offset);
#endif
/*
* These functions are provided to be called internally or by other parts of
* the kernel. It's up to the caller to ensure correct checksum before reading
* or after writing (needs to be done only once).
*
* It is worth noting that these functions all access bytes of general
* purpose memory in the NVRAM - that is to say, they all add the
* NVRAM_FIRST_BYTE offset. Pass them offsets into NVRAM as if you did not
* know about the RTC cruft.
*/
unsigned char __nvram_read_byte(int i)
{
return CMOS_READ(NVRAM_FIRST_BYTE + i);
}
EXPORT_SYMBOL(__nvram_read_byte);
unsigned char nvram_read_byte(int i)
{
unsigned long flags;
unsigned char c;
spin_lock_irqsave(&rtc_lock, flags);
c = __nvram_read_byte(i);
spin_unlock_irqrestore(&rtc_lock, flags);
return c;
}
EXPORT_SYMBOL(nvram_read_byte);
/* This races nicely with trying to read with checksum checking (nvram_read) */
void __nvram_write_byte(unsigned char c, int i)
{
CMOS_WRITE(c, NVRAM_FIRST_BYTE + i);
}
EXPORT_SYMBOL(__nvram_write_byte);
void nvram_write_byte(unsigned char c, int i)
{
unsigned long flags;
spin_lock_irqsave(&rtc_lock, flags);
__nvram_write_byte(c, i);
spin_unlock_irqrestore(&rtc_lock, flags);
}
EXPORT_SYMBOL(nvram_write_byte);
int __nvram_check_checksum(void)
{
return mach_check_checksum();
}
EXPORT_SYMBOL(__nvram_check_checksum);
int nvram_check_checksum(void)
{
unsigned long flags;
int rv;
spin_lock_irqsave(&rtc_lock, flags);
rv = __nvram_check_checksum();
spin_unlock_irqrestore(&rtc_lock, flags);
return rv;
}
EXPORT_SYMBOL(nvram_check_checksum);
static void __nvram_set_checksum(void)
{
mach_set_checksum();
}
#if 0
void nvram_set_checksum(void)
{
unsigned long flags;
spin_lock_irqsave(&rtc_lock, flags);
__nvram_set_checksum();
spin_unlock_irqrestore(&rtc_lock, flags);
}
#endif /* 0 */
/*
* The are the file operation function for user access to /dev/nvram
*/
static loff_t nvram_llseek(struct file *file, loff_t offset, int origin)
{
switch (origin) {
case 0:
/* nothing to do */
break;
case 1:
offset += file->f_pos;
break;
case 2:
offset += NVRAM_BYTES;
break;
}
return (offset >= 0) ? (file->f_pos = offset) : -EINVAL;
}
static ssize_t nvram_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
unsigned char contents[NVRAM_BYTES];
unsigned i = *ppos;
unsigned char *tmp;
spin_lock_irq(&rtc_lock);
if (!__nvram_check_checksum())
goto checksum_err;
for (tmp = contents; count-- > 0 && i < NVRAM_BYTES; ++i, ++tmp)
*tmp = __nvram_read_byte(i);
spin_unlock_irq(&rtc_lock);
if (copy_to_user(buf, contents, tmp - contents))
return -EFAULT;
*ppos = i;
return tmp - contents;
checksum_err:
spin_unlock_irq(&rtc_lock);
return -EIO;
}
static ssize_t nvram_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
unsigned char contents[NVRAM_BYTES];
unsigned i = *ppos;
unsigned char *tmp;
if (i >= NVRAM_BYTES)
return 0; /* Past EOF */
if (count > NVRAM_BYTES - i)
count = NVRAM_BYTES - i;
if (count > NVRAM_BYTES)
return -EFAULT; /* Can't happen, but prove it to gcc */
if (copy_from_user(contents, buf, count))
return -EFAULT;
spin_lock_irq(&rtc_lock);
if (!__nvram_check_checksum())
goto checksum_err;
for (tmp = contents; count--; ++i, ++tmp)
__nvram_write_byte(*tmp, i);
__nvram_set_checksum();
spin_unlock_irq(&rtc_lock);
*ppos = i;
return tmp - contents;
checksum_err:
spin_unlock_irq(&rtc_lock);
return -EIO;
}
static int nvram_ioctl(struct inode *inode, struct file *file,
unsigned int cmd, unsigned long arg)
{
int i;
switch (cmd) {
case NVRAM_INIT:
/* initialize NVRAM contents and checksum */
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
spin_lock_irq(&rtc_lock);
for (i = 0; i < NVRAM_BYTES; ++i)
__nvram_write_byte(0, i);
__nvram_set_checksum();
spin_unlock_irq(&rtc_lock);
return 0;
case NVRAM_SETCKS:
/* just set checksum, contents unchanged (maybe useful after
* checksum garbaged somehow...) */
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
spin_lock_irq(&rtc_lock);
__nvram_set_checksum();
spin_unlock_irq(&rtc_lock);
return 0;
default:
return -ENOTTY;
}
}
static int nvram_open(struct inode *inode, struct file *file)
{
lock_kernel();
spin_lock(&nvram_state_lock);
if ((nvram_open_cnt && (file->f_flags & O_EXCL)) ||
(nvram_open_mode & NVRAM_EXCL) ||
((file->f_mode & FMODE_WRITE) && (nvram_open_mode & NVRAM_WRITE))) {
spin_unlock(&nvram_state_lock);
unlock_kernel();
return -EBUSY;
}
if (file->f_flags & O_EXCL)
nvram_open_mode |= NVRAM_EXCL;
if (file->f_mode & FMODE_WRITE)
nvram_open_mode |= NVRAM_WRITE;
nvram_open_cnt++;
spin_unlock(&nvram_state_lock);
unlock_kernel();
return 0;
}
static int nvram_release(struct inode *inode, struct file *file)
{
spin_lock(&nvram_state_lock);
nvram_open_cnt--;
/* if only one instance is open, clear the EXCL bit */
if (nvram_open_mode & NVRAM_EXCL)
nvram_open_mode &= ~NVRAM_EXCL;
if (file->f_mode & FMODE_WRITE)
nvram_open_mode &= ~NVRAM_WRITE;
spin_unlock(&nvram_state_lock);
return 0;
}
#ifndef CONFIG_PROC_FS
static int nvram_add_proc_fs(void)
{
return 0;
}
#else
static int nvram_proc_read(struct seq_file *seq, void *offset)
{
unsigned char contents[NVRAM_BYTES];
int i = 0;
spin_lock_irq(&rtc_lock);
for (i = 0; i < NVRAM_BYTES; ++i)
contents[i] = __nvram_read_byte(i);
spin_unlock_irq(&rtc_lock);
mach_proc_infos(contents, seq, offset);
return 0;
}
static int nvram_proc_open(struct inode *inode, struct file *file)
{
return single_open(file, nvram_proc_read, NULL);
}
static const struct file_operations nvram_proc_fops = {
.owner = THIS_MODULE,
.open = nvram_proc_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
static int nvram_add_proc_fs(void)
{
if (!proc_create("driver/nvram", 0, NULL, &nvram_proc_fops))
return -ENOMEM;
return 0;
}
#endif /* CONFIG_PROC_FS */
static const struct file_operations nvram_fops = {
.owner = THIS_MODULE,
.llseek = nvram_llseek,
.read = nvram_read,
.write = nvram_write,
.ioctl = nvram_ioctl,
.open = nvram_open,
.release = nvram_release,
};
static struct miscdevice nvram_dev = {
NVRAM_MINOR,
"nvram",
&nvram_fops
};
static int __init nvram_init(void)
{
int ret;
/* First test whether the driver should init at all */
if (!CHECK_DRIVER_INIT())
return -ENODEV;
ret = misc_register(&nvram_dev);
if (ret) {
printk(KERN_ERR "nvram: can't misc_register on minor=%d\n",
NVRAM_MINOR);
goto out;
}
ret = nvram_add_proc_fs();
if (ret) {
printk(KERN_ERR "nvram: can't create /proc/driver/nvram\n");
goto outmisc;
}
ret = 0;
printk(KERN_INFO "Non-volatile memory driver v" NVRAM_VERSION "\n");
out:
return ret;
outmisc:
misc_deregister(&nvram_dev);
goto out;
}
static void __exit nvram_cleanup_module(void)
{
remove_proc_entry("driver/nvram", NULL);
misc_deregister(&nvram_dev);
}
module_init(nvram_init);
module_exit(nvram_cleanup_module);
/*
* Machine specific functions
*/
#if MACH == PC
static int pc_check_checksum(void)
{
int i;
unsigned short sum = 0;
unsigned short expect;
for (i = PC_CKS_RANGE_START; i <= PC_CKS_RANGE_END; ++i)
sum += __nvram_read_byte(i);
expect = __nvram_read_byte(PC_CKS_LOC)<<8 |
__nvram_read_byte(PC_CKS_LOC+1);
return (sum & 0xffff) == expect;
}
static void pc_set_checksum(void)
{
int i;
unsigned short sum = 0;
for (i = PC_CKS_RANGE_START; i <= PC_CKS_RANGE_END; ++i)
sum += __nvram_read_byte(i);
__nvram_write_byte(sum >> 8, PC_CKS_LOC);
__nvram_write_byte(sum & 0xff, PC_CKS_LOC + 1);
}
#ifdef CONFIG_PROC_FS
static char *floppy_types[] = {
"none", "5.25'' 360k", "5.25'' 1.2M", "3.5'' 720k", "3.5'' 1.44M",
"3.5'' 2.88M", "3.5'' 2.88M"
};
static char *gfx_types[] = {
"EGA, VGA, ... (with BIOS)",
"CGA (40 cols)",
"CGA (80 cols)",
"monochrome",
};
static void pc_proc_infos(unsigned char *nvram, struct seq_file *seq,
void *offset)
{
int checksum;
int type;
spin_lock_irq(&rtc_lock);
checksum = __nvram_check_checksum();
spin_unlock_irq(&rtc_lock);
seq_printf(seq, "Checksum status: %svalid\n", checksum ? "" : "not ");
seq_printf(seq, "# floppies : %d\n",
(nvram[6] & 1) ? (nvram[6] >> 6) + 1 : 0);
seq_printf(seq, "Floppy 0 type : ");
type = nvram[2] >> 4;
if (type < ARRAY_SIZE(floppy_types))
seq_printf(seq, "%s\n", floppy_types[type]);
else
seq_printf(seq, "%d (unknown)\n", type);
seq_printf(seq, "Floppy 1 type : ");
type = nvram[2] & 0x0f;
if (type < ARRAY_SIZE(floppy_types))
seq_printf(seq, "%s\n", floppy_types[type]);
else
seq_printf(seq, "%d (unknown)\n", type);
seq_printf(seq, "HD 0 type : ");
type = nvram[4] >> 4;
if (type)
seq_printf(seq, "%02x\n", type == 0x0f ? nvram[11] : type);
else
seq_printf(seq, "none\n");
seq_printf(seq, "HD 1 type : ");
type = nvram[4] & 0x0f;
if (type)
seq_printf(seq, "%02x\n", type == 0x0f ? nvram[12] : type);
else
seq_printf(seq, "none\n");
seq_printf(seq, "HD type 48 data: %d/%d/%d C/H/S, precomp %d, lz %d\n",
nvram[18] | (nvram[19] << 8),
nvram[20], nvram[25],
nvram[21] | (nvram[22] << 8), nvram[23] | (nvram[24] << 8));
seq_printf(seq, "HD type 49 data: %d/%d/%d C/H/S, precomp %d, lz %d\n",
nvram[39] | (nvram[40] << 8),
nvram[41], nvram[46],
nvram[42] | (nvram[43] << 8), nvram[44] | (nvram[45] << 8));
seq_printf(seq, "DOS base memory: %d kB\n", nvram[7] | (nvram[8] << 8));
seq_printf(seq, "Extended memory: %d kB (configured), %d kB (tested)\n",
nvram[9] | (nvram[10] << 8), nvram[34] | (nvram[35] << 8));
seq_printf(seq, "Gfx adapter : %s\n",
gfx_types[(nvram[6] >> 4) & 3]);
seq_printf(seq, "FPU : %sinstalled\n",
(nvram[6] & 2) ? "" : "not ");
return;
}
#endif
#endif /* MACH == PC */
#if MACH == ATARI
static int atari_check_checksum(void)
{
int i;
unsigned char sum = 0;
for (i = ATARI_CKS_RANGE_START; i <= ATARI_CKS_RANGE_END; ++i)
sum += __nvram_read_byte(i);
return (__nvram_read_byte(ATARI_CKS_LOC) == (~sum & 0xff)) &&
(__nvram_read_byte(ATARI_CKS_LOC + 1) == (sum & 0xff));
}
static void atari_set_checksum(void)
{
int i;
unsigned char sum = 0;
for (i = ATARI_CKS_RANGE_START; i <= ATARI_CKS_RANGE_END; ++i)
sum += __nvram_read_byte(i);
__nvram_write_byte(~sum, ATARI_CKS_LOC);
__nvram_write_byte(sum, ATARI_CKS_LOC + 1);
}
#ifdef CONFIG_PROC_FS
static struct {
unsigned char val;
char *name;
} boot_prefs[] = {
{ 0x80, "TOS" },
{ 0x40, "ASV" },
{ 0x20, "NetBSD (?)" },
{ 0x10, "Linux" },
{ 0x00, "unspecified" }
};
static char *languages[] = {
"English (US)",
"German",
"French",
"English (UK)",
"Spanish",
"Italian",
"6 (undefined)",
"Swiss (French)",
"Swiss (German)"
};
static char *dateformat[] = {
"MM%cDD%cYY",
"DD%cMM%cYY",
"YY%cMM%cDD",
"YY%cDD%cMM",
"4 (undefined)",
"5 (undefined)",
"6 (undefined)",
"7 (undefined)"
};
static char *colors[] = {
"2", "4", "16", "256", "65536", "??", "??", "??"
};
static void atari_proc_infos(unsigned char *nvram, struct seq_file *seq,
void *offset)
{
int checksum = nvram_check_checksum();
int i;
unsigned vmode;
seq_printf(seq, "Checksum status : %svalid\n", checksum ? "" : "not ");
seq_printf(seq, "Boot preference : ");
for (i = ARRAY_SIZE(boot_prefs) - 1; i >= 0; --i) {
if (nvram[1] == boot_prefs[i].val) {
seq_printf(seq, "%s\n", boot_prefs[i].name);
break;
}
}
if (i < 0)
seq_printf(seq, "0x%02x (undefined)\n", nvram[1]);
seq_printf(seq, "SCSI arbitration : %s\n",
(nvram[16] & 0x80) ? "on" : "off");
seq_printf(seq, "SCSI host ID : ");
if (nvram[16] & 0x80)
seq_printf(seq, "%d\n", nvram[16] & 7);
else
seq_printf(seq, "n/a\n");
/* the following entries are defined only for the Falcon */
if ((atari_mch_cookie >> 16) != ATARI_MCH_FALCON)
return;
seq_printf(seq, "OS language : ");
if (nvram[6] < ARRAY_SIZE(languages))
seq_printf(seq, "%s\n", languages[nvram[6]]);
else
seq_printf(seq, "%u (undefined)\n", nvram[6]);
seq_printf(seq, "Keyboard language: ");
if (nvram[7] < ARRAY_SIZE(languages))
seq_printf(seq, "%s\n", languages[nvram[7]]);
else
seq_printf(seq, "%u (undefined)\n", nvram[7]);
seq_printf(seq, "Date format : ");
seq_printf(seq, dateformat[nvram[8] & 7],
nvram[9] ? nvram[9] : '/', nvram[9] ? nvram[9] : '/');
seq_printf(seq, ", %dh clock\n", nvram[8] & 16 ? 24 : 12);
seq_printf(seq, "Boot delay : ");
if (nvram[10] == 0)
seq_printf(seq, "default");
else
seq_printf(seq, "%ds%s\n", nvram[10],
nvram[10] < 8 ? ", no memory test" : "");
vmode = (nvram[14] << 8) || nvram[15];
seq_printf(seq,
"Video mode : %s colors, %d columns, %s %s monitor\n",
colors[vmode & 7],
vmode & 8 ? 80 : 40,
vmode & 16 ? "VGA" : "TV", vmode & 32 ? "PAL" : "NTSC");
seq_printf(seq, " %soverscan, compat. mode %s%s\n",
vmode & 64 ? "" : "no ",
vmode & 128 ? "on" : "off",
vmode & 256 ?
(vmode & 16 ? ", line doubling" : ", half screen") : "");
return;
}
#endif
#endif /* MACH == ATARI */
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(NVRAM_MINOR);