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linux/drivers/rtc/rtc-m48t59.c
David Brownell a4b1d50e61 RTCs: handle NVRAM better 
Several of the RTC drivers are exporting binary "nvram" files in sysfs.  Such
NVRAM (or on many systems, EEPROM) data is often initialized during system
manufacture to hold data about identity (serial numbers, Ethernet addresses,
etc), configuration, calibration, and so forth.

This patch improves integrity and security of those files:

  - Correctly initializes the size in one of the two cases where
    that was not yet being done.

  - Improves system security/integrity by making this state not
    be world-writable by default.

Letting arbitrary userspace code mangle such state by default is at least Not
A Good Thing; and it could sometimes be worse, depending on the particular
data that might be corrupted.  (I disregard the paranoiac "don't let anyone
read it either" approach.  Anyone storing passwords in such memory doesn't
really care about security.)

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Cc: Torsten Ertbjerg Rasmussen <tr@newtec.dk>
Cc: Mark Zhan <rongkai.zhan@windriver.com>
Cc: Thomas Hommel <thomas.hommel@gefanuc.com>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-11-14 18:45:36 -08:00

493 lines
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/*
* ST M48T59 RTC driver
*
* Copyright (c) 2007 Wind River Systems, Inc.
*
* Author: Mark Zhan <rongkai.zhan@windriver.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/rtc/m48t59.h>
#include <linux/bcd.h>
#ifndef NO_IRQ
#define NO_IRQ (-1)
#endif
#define M48T59_READ(reg) pdata->read_byte(dev, reg)
#define M48T59_WRITE(val, reg) pdata->write_byte(dev, reg, val)
#define M48T59_SET_BITS(mask, reg) \
M48T59_WRITE((M48T59_READ(reg) | (mask)), (reg))
#define M48T59_CLEAR_BITS(mask, reg) \
M48T59_WRITE((M48T59_READ(reg) & ~(mask)), (reg))
struct m48t59_private {
void __iomem *ioaddr;
unsigned int size; /* iomem size */
int irq;
struct rtc_device *rtc;
spinlock_t lock; /* serialize the NVRAM and RTC access */
};
/*
* This is the generic access method when the chip is memory-mapped
*/
static void
m48t59_mem_writeb(struct device *dev, u32 ofs, u8 val)
{
struct platform_device *pdev = to_platform_device(dev);
struct m48t59_private *m48t59 = platform_get_drvdata(pdev);
writeb(val, m48t59->ioaddr+ofs);
}
static u8
m48t59_mem_readb(struct device *dev, u32 ofs)
{
struct platform_device *pdev = to_platform_device(dev);
struct m48t59_private *m48t59 = platform_get_drvdata(pdev);
return readb(m48t59->ioaddr+ofs);
}
/*
* NOTE: M48T59 only uses BCD mode
*/
static int m48t59_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
struct platform_device *pdev = to_platform_device(dev);
struct m48t59_plat_data *pdata = pdev->dev.platform_data;
struct m48t59_private *m48t59 = platform_get_drvdata(pdev);
unsigned long flags;
u8 val;
spin_lock_irqsave(&m48t59->lock, flags);
/* Issue the READ command */
M48T59_SET_BITS(M48T59_CNTL_READ, M48T59_CNTL);
tm->tm_year = BCD2BIN(M48T59_READ(M48T59_YEAR));
/* tm_mon is 0-11 */
tm->tm_mon = BCD2BIN(M48T59_READ(M48T59_MONTH)) - 1;
tm->tm_mday = BCD2BIN(M48T59_READ(M48T59_MDAY));
val = M48T59_READ(M48T59_WDAY);
if ((val & M48T59_WDAY_CEB) && (val & M48T59_WDAY_CB)) {
dev_dbg(dev, "Century bit is enabled\n");
tm->tm_year += 100; /* one century */
}
tm->tm_wday = BCD2BIN(val & 0x07);
tm->tm_hour = BCD2BIN(M48T59_READ(M48T59_HOUR) & 0x3F);
tm->tm_min = BCD2BIN(M48T59_READ(M48T59_MIN) & 0x7F);
tm->tm_sec = BCD2BIN(M48T59_READ(M48T59_SEC) & 0x7F);
/* Clear the READ bit */
M48T59_CLEAR_BITS(M48T59_CNTL_READ, M48T59_CNTL);
spin_unlock_irqrestore(&m48t59->lock, flags);
dev_dbg(dev, "RTC read time %04d-%02d-%02d %02d/%02d/%02d\n",
tm->tm_year + 1900, tm->tm_mon, tm->tm_mday,
tm->tm_hour, tm->tm_min, tm->tm_sec);
return 0;
}
static int m48t59_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
struct platform_device *pdev = to_platform_device(dev);
struct m48t59_plat_data *pdata = pdev->dev.platform_data;
struct m48t59_private *m48t59 = platform_get_drvdata(pdev);
unsigned long flags;
u8 val = 0;
dev_dbg(dev, "RTC set time %04d-%02d-%02d %02d/%02d/%02d\n",
tm->tm_year + 1900, tm->tm_mon, tm->tm_mday,
tm->tm_hour, tm->tm_min, tm->tm_sec);
spin_lock_irqsave(&m48t59->lock, flags);
/* Issue the WRITE command */
M48T59_SET_BITS(M48T59_CNTL_WRITE, M48T59_CNTL);
M48T59_WRITE((BIN2BCD(tm->tm_sec) & 0x7F), M48T59_SEC);
M48T59_WRITE((BIN2BCD(tm->tm_min) & 0x7F), M48T59_MIN);
M48T59_WRITE((BIN2BCD(tm->tm_hour) & 0x3F), M48T59_HOUR);
M48T59_WRITE((BIN2BCD(tm->tm_mday) & 0x3F), M48T59_MDAY);
/* tm_mon is 0-11 */
M48T59_WRITE((BIN2BCD(tm->tm_mon + 1) & 0x1F), M48T59_MONTH);
M48T59_WRITE(BIN2BCD(tm->tm_year % 100), M48T59_YEAR);
if (tm->tm_year/100)
val = (M48T59_WDAY_CEB | M48T59_WDAY_CB);
val |= (BIN2BCD(tm->tm_wday) & 0x07);
M48T59_WRITE(val, M48T59_WDAY);
/* Clear the WRITE bit */
M48T59_CLEAR_BITS(M48T59_CNTL_WRITE, M48T59_CNTL);
spin_unlock_irqrestore(&m48t59->lock, flags);
return 0;
}
/*
* Read alarm time and date in RTC
*/
static int m48t59_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm)
{
struct platform_device *pdev = to_platform_device(dev);
struct m48t59_plat_data *pdata = pdev->dev.platform_data;
struct m48t59_private *m48t59 = platform_get_drvdata(pdev);
struct rtc_time *tm = &alrm->time;
unsigned long flags;
u8 val;
/* If no irq, we don't support ALARM */
if (m48t59->irq == NO_IRQ)
return -EIO;
spin_lock_irqsave(&m48t59->lock, flags);
/* Issue the READ command */
M48T59_SET_BITS(M48T59_CNTL_READ, M48T59_CNTL);
tm->tm_year = BCD2BIN(M48T59_READ(M48T59_YEAR));
/* tm_mon is 0-11 */
tm->tm_mon = BCD2BIN(M48T59_READ(M48T59_MONTH)) - 1;
val = M48T59_READ(M48T59_WDAY);
if ((val & M48T59_WDAY_CEB) && (val & M48T59_WDAY_CB))
tm->tm_year += 100; /* one century */
tm->tm_mday = BCD2BIN(M48T59_READ(M48T59_ALARM_DATE));
tm->tm_hour = BCD2BIN(M48T59_READ(M48T59_ALARM_HOUR));
tm->tm_min = BCD2BIN(M48T59_READ(M48T59_ALARM_MIN));
tm->tm_sec = BCD2BIN(M48T59_READ(M48T59_ALARM_SEC));
/* Clear the READ bit */
M48T59_CLEAR_BITS(M48T59_CNTL_READ, M48T59_CNTL);
spin_unlock_irqrestore(&m48t59->lock, flags);
dev_dbg(dev, "RTC read alarm time %04d-%02d-%02d %02d/%02d/%02d\n",
tm->tm_year + 1900, tm->tm_mon, tm->tm_mday,
tm->tm_hour, tm->tm_min, tm->tm_sec);
return 0;
}
/*
* Set alarm time and date in RTC
*/
static int m48t59_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
{
struct platform_device *pdev = to_platform_device(dev);
struct m48t59_plat_data *pdata = pdev->dev.platform_data;
struct m48t59_private *m48t59 = platform_get_drvdata(pdev);
struct rtc_time *tm = &alrm->time;
u8 mday, hour, min, sec;
unsigned long flags;
/* If no irq, we don't support ALARM */
if (m48t59->irq == NO_IRQ)
return -EIO;
/*
* 0xff means "always match"
*/
mday = tm->tm_mday;
mday = (mday >= 1 && mday <= 31) ? BIN2BCD(mday) : 0xff;
if (mday == 0xff)
mday = M48T59_READ(M48T59_MDAY);
hour = tm->tm_hour;
hour = (hour < 24) ? BIN2BCD(hour) : 0x00;
min = tm->tm_min;
min = (min < 60) ? BIN2BCD(min) : 0x00;
sec = tm->tm_sec;
sec = (sec < 60) ? BIN2BCD(sec) : 0x00;
spin_lock_irqsave(&m48t59->lock, flags);
/* Issue the WRITE command */
M48T59_SET_BITS(M48T59_CNTL_WRITE, M48T59_CNTL);
M48T59_WRITE(mday, M48T59_ALARM_DATE);
M48T59_WRITE(hour, M48T59_ALARM_HOUR);
M48T59_WRITE(min, M48T59_ALARM_MIN);
M48T59_WRITE(sec, M48T59_ALARM_SEC);
/* Clear the WRITE bit */
M48T59_CLEAR_BITS(M48T59_CNTL_WRITE, M48T59_CNTL);
spin_unlock_irqrestore(&m48t59->lock, flags);
dev_dbg(dev, "RTC set alarm time %04d-%02d-%02d %02d/%02d/%02d\n",
tm->tm_year + 1900, tm->tm_mon, tm->tm_mday,
tm->tm_hour, tm->tm_min, tm->tm_sec);
return 0;
}
/*
* Handle commands from user-space
*/
static int m48t59_rtc_ioctl(struct device *dev, unsigned int cmd,
unsigned long arg)
{
struct platform_device *pdev = to_platform_device(dev);
struct m48t59_plat_data *pdata = pdev->dev.platform_data;
struct m48t59_private *m48t59 = platform_get_drvdata(pdev);
unsigned long flags;
int ret = 0;
spin_lock_irqsave(&m48t59->lock, flags);
switch (cmd) {
case RTC_AIE_OFF: /* alarm interrupt off */
M48T59_WRITE(0x00, M48T59_INTR);
break;
case RTC_AIE_ON: /* alarm interrupt on */
M48T59_WRITE(M48T59_INTR_AFE, M48T59_INTR);
break;
default:
ret = -ENOIOCTLCMD;
break;
}
spin_unlock_irqrestore(&m48t59->lock, flags);
return ret;
}
static int m48t59_rtc_proc(struct device *dev, struct seq_file *seq)
{
struct platform_device *pdev = to_platform_device(dev);
struct m48t59_plat_data *pdata = pdev->dev.platform_data;
struct m48t59_private *m48t59 = platform_get_drvdata(pdev);
unsigned long flags;
u8 val;
spin_lock_irqsave(&m48t59->lock, flags);
val = M48T59_READ(M48T59_FLAGS);
spin_unlock_irqrestore(&m48t59->lock, flags);
seq_printf(seq, "battery\t\t: %s\n",
(val & M48T59_FLAGS_BF) ? "low" : "normal");
return 0;
}
/*
* IRQ handler for the RTC
*/
static irqreturn_t m48t59_rtc_interrupt(int irq, void *dev_id)
{
struct device *dev = (struct device *)dev_id;
struct platform_device *pdev = to_platform_device(dev);
struct m48t59_plat_data *pdata = pdev->dev.platform_data;
struct m48t59_private *m48t59 = platform_get_drvdata(pdev);
u8 event;
spin_lock(&m48t59->lock);
event = M48T59_READ(M48T59_FLAGS);
spin_unlock(&m48t59->lock);
if (event & M48T59_FLAGS_AF) {
rtc_update_irq(m48t59->rtc, 1, (RTC_AF | RTC_IRQF));
return IRQ_HANDLED;
}
return IRQ_NONE;
}
static const struct rtc_class_ops m48t59_rtc_ops = {
.ioctl = m48t59_rtc_ioctl,
.read_time = m48t59_rtc_read_time,
.set_time = m48t59_rtc_set_time,
.read_alarm = m48t59_rtc_readalarm,
.set_alarm = m48t59_rtc_setalarm,
.proc = m48t59_rtc_proc,
};
static ssize_t m48t59_nvram_read(struct kobject *kobj,
struct bin_attribute *bin_attr,
char *buf, loff_t pos, size_t size)
{
struct device *dev = container_of(kobj, struct device, kobj);
struct platform_device *pdev = to_platform_device(dev);
struct m48t59_plat_data *pdata = pdev->dev.platform_data;
struct m48t59_private *m48t59 = platform_get_drvdata(pdev);
ssize_t cnt = 0;
unsigned long flags;
for (; size > 0 && pos < M48T59_NVRAM_SIZE; cnt++, size--) {
spin_lock_irqsave(&m48t59->lock, flags);
*buf++ = M48T59_READ(cnt);
spin_unlock_irqrestore(&m48t59->lock, flags);
}
return cnt;
}
static ssize_t m48t59_nvram_write(struct kobject *kobj,
struct bin_attribute *bin_attr,
char *buf, loff_t pos, size_t size)
{
struct device *dev = container_of(kobj, struct device, kobj);
struct platform_device *pdev = to_platform_device(dev);
struct m48t59_plat_data *pdata = pdev->dev.platform_data;
struct m48t59_private *m48t59 = platform_get_drvdata(pdev);
ssize_t cnt = 0;
unsigned long flags;
for (; size > 0 && pos < M48T59_NVRAM_SIZE; cnt++, size--) {
spin_lock_irqsave(&m48t59->lock, flags);
M48T59_WRITE(*buf++, cnt);
spin_unlock_irqrestore(&m48t59->lock, flags);
}
return cnt;
}
static struct bin_attribute m48t59_nvram_attr = {
.attr = {
.name = "nvram",
.mode = S_IRUGO | S_IWUSR,
.owner = THIS_MODULE,
},
.read = m48t59_nvram_read,
.write = m48t59_nvram_write,
.size = M48T59_NVRAM_SIZE,
};
static int __devinit m48t59_rtc_probe(struct platform_device *pdev)
{
struct m48t59_plat_data *pdata = pdev->dev.platform_data;
struct m48t59_private *m48t59 = NULL;
struct resource *res;
int ret = -ENOMEM;
/* This chip could be memory-mapped or I/O-mapped */
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!res) {
res = platform_get_resource(pdev, IORESOURCE_IO, 0);
if (!res)
return -EINVAL;
}
if (res->flags & IORESOURCE_IO) {
/* If we are I/O-mapped, the platform should provide
* the operations accessing chip registers.
*/
if (!pdata || !pdata->write_byte || !pdata->read_byte)
return -EINVAL;
} else if (res->flags & IORESOURCE_MEM) {
/* we are memory-mapped */
if (!pdata) {
pdata = kzalloc(sizeof(*pdata), GFP_KERNEL);
if (!pdata)
return -ENOMEM;
/* Ensure we only kmalloc platform data once */
pdev->dev.platform_data = pdata;
}
/* Try to use the generic memory read/write ops */
if (!pdata->write_byte)
pdata->write_byte = m48t59_mem_writeb;
if (!pdata->read_byte)
pdata->read_byte = m48t59_mem_readb;
}
m48t59 = kzalloc(sizeof(*m48t59), GFP_KERNEL);
if (!m48t59)
return -ENOMEM;
m48t59->size = res->end - res->start + 1;
m48t59->ioaddr = ioremap(res->start, m48t59->size);
if (!m48t59->ioaddr)
goto out;
/* Try to get irq number. We also can work in
* the mode without IRQ.
*/
m48t59->irq = platform_get_irq(pdev, 0);
if (m48t59->irq < 0)
m48t59->irq = NO_IRQ;
if (m48t59->irq != NO_IRQ) {
ret = request_irq(m48t59->irq, m48t59_rtc_interrupt,
IRQF_SHARED, "rtc-m48t59", &pdev->dev);
if (ret)
goto out;
}
m48t59->rtc = rtc_device_register("m48t59", &pdev->dev,
&m48t59_rtc_ops, THIS_MODULE);
if (IS_ERR(m48t59->rtc)) {
ret = PTR_ERR(m48t59->rtc);
goto out;
}
ret = sysfs_create_bin_file(&pdev->dev.kobj, &m48t59_nvram_attr);
if (ret)
goto out;
spin_lock_init(&m48t59->lock);
platform_set_drvdata(pdev, m48t59);
return 0;
out:
if (!IS_ERR(m48t59->rtc))
rtc_device_unregister(m48t59->rtc);
if (m48t59->irq != NO_IRQ)
free_irq(m48t59->irq, &pdev->dev);
if (m48t59->ioaddr)
iounmap(m48t59->ioaddr);
if (m48t59)
kfree(m48t59);
return ret;
}
static int __devexit m48t59_rtc_remove(struct platform_device *pdev)
{
struct m48t59_private *m48t59 = platform_get_drvdata(pdev);
sysfs_remove_bin_file(&pdev->dev.kobj, &m48t59_nvram_attr);
if (!IS_ERR(m48t59->rtc))
rtc_device_unregister(m48t59->rtc);
if (m48t59->ioaddr)
iounmap(m48t59->ioaddr);
if (m48t59->irq != NO_IRQ)
free_irq(m48t59->irq, &pdev->dev);
platform_set_drvdata(pdev, NULL);
kfree(m48t59);
return 0;
}
static struct platform_driver m48t59_rtc_driver = {
.driver = {
.name = "rtc-m48t59",
.owner = THIS_MODULE,
},
.probe = m48t59_rtc_probe,
.remove = __devexit_p(m48t59_rtc_remove),
};
static int __init m48t59_rtc_init(void)
{
return platform_driver_register(&m48t59_rtc_driver);
}
static void __exit m48t59_rtc_exit(void)
{
platform_driver_unregister(&m48t59_rtc_driver);
}
module_init(m48t59_rtc_init);
module_exit(m48t59_rtc_exit);
MODULE_AUTHOR("Mark Zhan <rongkai.zhan@windriver.com>");
MODULE_DESCRIPTION("M48T59 RTC driver");
MODULE_LICENSE("GPL");
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