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linux/drivers/char/hw_random.c

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/*
Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
(c) Copyright 2003 Red Hat Inc <jgarzik@redhat.com>
derived from
Hardware driver for the AMD 768 Random Number Generator (RNG)
(c) Copyright 2001 Red Hat Inc <alan@redhat.com>
derived from
Hardware driver for Intel i810 Random Number Generator (RNG)
Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com>
Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>
Please read Documentation/hw_random.txt for details on use.
----------------------------------------------------------
This software may be used and distributed according to the terms
of the GNU General Public License, incorporated herein by reference.
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/pci.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/random.h>
#include <linux/miscdevice.h>
#include <linux/smp_lock.h>
#include <linux/mm.h>
#include <linux/delay.h>
#ifdef __i386__
#include <asm/msr.h>
#include <asm/cpufeature.h>
#endif
#include <asm/io.h>
#include <asm/uaccess.h>
/*
* core module and version information
*/
#define RNG_VERSION "1.0.0"
#define RNG_MODULE_NAME "hw_random"
#define RNG_DRIVER_NAME RNG_MODULE_NAME " hardware driver " RNG_VERSION
#define PFX RNG_MODULE_NAME ": "
/*
* debugging macros
*/
/* pr_debug() collapses to a no-op if DEBUG is not defined */
#define DPRINTK(fmt, args...) pr_debug(PFX "%s: " fmt, __FUNCTION__ , ## args)
#undef RNG_NDEBUG /* define to enable lightweight runtime checks */
#ifdef RNG_NDEBUG
#define assert(expr) \
if(!(expr)) { \
printk(KERN_DEBUG PFX "Assertion failed! %s,%s,%s," \
"line=%d\n", #expr, __FILE__, __FUNCTION__, __LINE__); \
}
#else
#define assert(expr)
#endif
#define RNG_MISCDEV_MINOR 183 /* official */
static int rng_dev_open (struct inode *inode, struct file *filp);
static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size,
loff_t * offp);
static int __init intel_init (struct pci_dev *dev);
static void intel_cleanup(void);
static unsigned int intel_data_present (void);
static u32 intel_data_read (void);
static int __init amd_init (struct pci_dev *dev);
static void amd_cleanup(void);
static unsigned int amd_data_present (void);
static u32 amd_data_read (void);
#ifdef __i386__
static int __init via_init(struct pci_dev *dev);
static void via_cleanup(void);
static unsigned int via_data_present (void);
static u32 via_data_read (void);
#endif
struct rng_operations {
int (*init) (struct pci_dev *dev);
void (*cleanup) (void);
unsigned int (*data_present) (void);
u32 (*data_read) (void);
unsigned int n_bytes; /* number of bytes per ->data_read */
};
static struct rng_operations *rng_ops;
static struct file_operations rng_chrdev_ops = {
.owner = THIS_MODULE,
.open = rng_dev_open,
.read = rng_dev_read,
};
static struct miscdevice rng_miscdev = {
RNG_MISCDEV_MINOR,
RNG_MODULE_NAME,
&rng_chrdev_ops,
};
enum {
rng_hw_none,
rng_hw_intel,
rng_hw_amd,
rng_hw_via,
};
static struct rng_operations rng_vendor_ops[] = {
/* rng_hw_none */
{ },
/* rng_hw_intel */
{ intel_init, intel_cleanup, intel_data_present,
intel_data_read, 1 },
/* rng_hw_amd */
{ amd_init, amd_cleanup, amd_data_present, amd_data_read, 4 },
#ifdef __i386__
/* rng_hw_via */
{ via_init, via_cleanup, via_data_present, via_data_read, 1 },
#endif
};
/*
* Data for PCI driver interface
*
* This data only exists for exporting the supported
* PCI ids via MODULE_DEVICE_TABLE. We do not actually
* register a pci_driver, because someone else might one day
* want to register another driver on the same PCI id.
*/
static struct pci_device_id rng_pci_tbl[] = {
{ 0x1022, 0x7443, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_amd },
{ 0x1022, 0x746b, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_amd },
{ 0x8086, 0x2418, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_intel },
{ 0x8086, 0x2428, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_intel },
{ 0x8086, 0x2448, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_intel },
{ 0x8086, 0x244e, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_intel },
{ 0x8086, 0x245e, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_intel },
{ 0, }, /* terminate list */
};
MODULE_DEVICE_TABLE (pci, rng_pci_tbl);
/***********************************************************************
*
* Intel RNG operations
*
*/
/*
* RNG registers (offsets from rng_mem)
*/
#define INTEL_RNG_HW_STATUS 0
#define INTEL_RNG_PRESENT 0x40
#define INTEL_RNG_ENABLED 0x01
#define INTEL_RNG_STATUS 1
#define INTEL_RNG_DATA_PRESENT 0x01
#define INTEL_RNG_DATA 2
/*
* Magic address at which Intel PCI bridges locate the RNG
*/
#define INTEL_RNG_ADDR 0xFFBC015F
#define INTEL_RNG_ADDR_LEN 3
/* token to our ioremap'd RNG register area */
static void __iomem *rng_mem;
static inline u8 intel_hwstatus (void)
{
assert (rng_mem != NULL);
return readb (rng_mem + INTEL_RNG_HW_STATUS);
}
static inline u8 intel_hwstatus_set (u8 hw_status)
{
assert (rng_mem != NULL);
writeb (hw_status, rng_mem + INTEL_RNG_HW_STATUS);
return intel_hwstatus ();
}
static unsigned int intel_data_present(void)
{
assert (rng_mem != NULL);
return (readb (rng_mem + INTEL_RNG_STATUS) & INTEL_RNG_DATA_PRESENT) ?
1 : 0;
}
static u32 intel_data_read(void)
{
assert (rng_mem != NULL);
return readb (rng_mem + INTEL_RNG_DATA);
}
static int __init intel_init (struct pci_dev *dev)
{
int rc;
u8 hw_status;
DPRINTK ("ENTER\n");
rng_mem = ioremap (INTEL_RNG_ADDR, INTEL_RNG_ADDR_LEN);
if (rng_mem == NULL) {
printk (KERN_ERR PFX "cannot ioremap RNG Memory\n");
rc = -EBUSY;
goto err_out;
}
/* Check for Intel 82802 */
hw_status = intel_hwstatus ();
if ((hw_status & INTEL_RNG_PRESENT) == 0) {
printk (KERN_ERR PFX "RNG not detected\n");
rc = -ENODEV;
goto err_out_free_map;
}
/* turn RNG h/w on, if it's off */
if ((hw_status & INTEL_RNG_ENABLED) == 0)
hw_status = intel_hwstatus_set (hw_status | INTEL_RNG_ENABLED);
if ((hw_status & INTEL_RNG_ENABLED) == 0) {
printk (KERN_ERR PFX "cannot enable RNG, aborting\n");
rc = -EIO;
goto err_out_free_map;
}
DPRINTK ("EXIT, returning 0\n");
return 0;
err_out_free_map:
iounmap (rng_mem);
rng_mem = NULL;
err_out:
DPRINTK ("EXIT, returning %d\n", rc);
return rc;
}
static void intel_cleanup(void)
{
u8 hw_status;
hw_status = intel_hwstatus ();
if (hw_status & INTEL_RNG_ENABLED)
intel_hwstatus_set (hw_status & ~INTEL_RNG_ENABLED);
else
printk(KERN_WARNING PFX "unusual: RNG already disabled\n");
iounmap(rng_mem);
rng_mem = NULL;
}
/***********************************************************************
*
* AMD RNG operations
*
*/
static u32 pmbase; /* PMxx I/O base */
static struct pci_dev *amd_dev;
static unsigned int amd_data_present (void)
{
return inl(pmbase + 0xF4) & 1;
}
static u32 amd_data_read (void)
{
return inl(pmbase + 0xF0);
}
static int __init amd_init (struct pci_dev *dev)
{
int rc;
u8 rnen;
DPRINTK ("ENTER\n");
pci_read_config_dword(dev, 0x58, &pmbase);
pmbase &= 0x0000FF00;
if (pmbase == 0)
{
printk (KERN_ERR PFX "power management base not set\n");
rc = -EIO;
goto err_out;
}
pci_read_config_byte(dev, 0x40, &rnen);
rnen |= (1 << 7); /* RNG on */
pci_write_config_byte(dev, 0x40, rnen);
pci_read_config_byte(dev, 0x41, &rnen);
rnen |= (1 << 7); /* PMIO enable */
pci_write_config_byte(dev, 0x41, rnen);
pr_info( PFX "AMD768 system management I/O registers at 0x%X.\n",
pmbase);
amd_dev = dev;
DPRINTK ("EXIT, returning 0\n");
return 0;
err_out:
DPRINTK ("EXIT, returning %d\n", rc);
return rc;
}
static void amd_cleanup(void)
{
u8 rnen;
pci_read_config_byte(amd_dev, 0x40, &rnen);
rnen &= ~(1 << 7); /* RNG off */
pci_write_config_byte(amd_dev, 0x40, rnen);
/* FIXME: twiddle pmio, also? */
}
#ifdef __i386__
/***********************************************************************
*
* VIA RNG operations
*
*/
enum {
VIA_STRFILT_CNT_SHIFT = 16,
VIA_STRFILT_FAIL = (1 << 15),
VIA_STRFILT_ENABLE = (1 << 14),
VIA_RAWBITS_ENABLE = (1 << 13),
VIA_RNG_ENABLE = (1 << 6),
VIA_XSTORE_CNT_MASK = 0x0F,
VIA_RNG_CHUNK_8 = 0x00, /* 64 rand bits, 64 stored bits */
VIA_RNG_CHUNK_4 = 0x01, /* 32 rand bits, 32 stored bits */
VIA_RNG_CHUNK_4_MASK = 0xFFFFFFFF,
VIA_RNG_CHUNK_2 = 0x02, /* 16 rand bits, 32 stored bits */
VIA_RNG_CHUNK_2_MASK = 0xFFFF,
VIA_RNG_CHUNK_1 = 0x03, /* 8 rand bits, 32 stored bits */
VIA_RNG_CHUNK_1_MASK = 0xFF,
};
static u32 via_rng_datum;
/*
* Investigate using the 'rep' prefix to obtain 32 bits of random data
* in one insn. The upside is potentially better performance. The
* downside is that the instruction becomes no longer atomic. Due to
* this, just like familiar issues with /dev/random itself, the worst
* case of a 'rep xstore' could potentially pause a cpu for an
* unreasonably long time. In practice, this condition would likely
* only occur when the hardware is failing. (or so we hope :))
*
* Another possible performance boost may come from simply buffering
* until we have 4 bytes, thus returning a u32 at a time,
* instead of the current u8-at-a-time.
*/
static inline u32 xstore(u32 *addr, u32 edx_in)
{
u32 eax_out;
asm(".byte 0x0F,0xA7,0xC0 /* xstore %%edi (addr=%0) */"
:"=m"(*addr), "=a"(eax_out)
:"D"(addr), "d"(edx_in));
return eax_out;
}
static unsigned int via_data_present(void)
{
u32 bytes_out;
/* We choose the recommended 1-byte-per-instruction RNG rate,
* for greater randomness at the expense of speed. Larger
* values 2, 4, or 8 bytes-per-instruction yield greater
* speed at lesser randomness.
*
* If you change this to another VIA_CHUNK_n, you must also
* change the ->n_bytes values in rng_vendor_ops[] tables.
* VIA_CHUNK_8 requires further code changes.
*
* A copy of MSR_VIA_RNG is placed in eax_out when xstore
* completes.
*/
via_rng_datum = 0; /* paranoia, not really necessary */
bytes_out = xstore(&via_rng_datum, VIA_RNG_CHUNK_1) & VIA_XSTORE_CNT_MASK;
if (bytes_out == 0)
return 0;
return 1;
}
static u32 via_data_read(void)
{
return via_rng_datum;
}
static int __init via_init(struct pci_dev *dev)
{
u32 lo, hi, old_lo;
/* Control the RNG via MSR. Tread lightly and pay very close
* close attention to values written, as the reserved fields
* are documented to be "undefined and unpredictable"; but it
* does not say to write them as zero, so I make a guess that
* we restore the values we find in the register.
*/
rdmsr(MSR_VIA_RNG, lo, hi);
old_lo = lo;
lo &= ~(0x7f << VIA_STRFILT_CNT_SHIFT);
lo &= ~VIA_XSTORE_CNT_MASK;
lo &= ~(VIA_STRFILT_ENABLE | VIA_STRFILT_FAIL | VIA_RAWBITS_ENABLE);
lo |= VIA_RNG_ENABLE;
if (lo != old_lo)
wrmsr(MSR_VIA_RNG, lo, hi);
/* perhaps-unnecessary sanity check; remove after testing if
unneeded */
rdmsr(MSR_VIA_RNG, lo, hi);
if ((lo & VIA_RNG_ENABLE) == 0) {
printk(KERN_ERR PFX "cannot enable VIA C3 RNG, aborting\n");
return -ENODEV;
}
return 0;
}
static void via_cleanup(void)
{
/* do nothing */
}
#endif
/***********************************************************************
*
* /dev/hwrandom character device handling (major 10, minor 183)
*
*/
static int rng_dev_open (struct inode *inode, struct file *filp)
{
/* enforce read-only access to this chrdev */
if ((filp->f_mode & FMODE_READ) == 0)
return -EINVAL;
if (filp->f_mode & FMODE_WRITE)
return -EINVAL;
return 0;
}
static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size,
loff_t * offp)
{
static DEFINE_SPINLOCK(rng_lock);
unsigned int have_data;
u32 data = 0;
ssize_t ret = 0;
while (size) {
spin_lock(&rng_lock);
have_data = 0;
if (rng_ops->data_present()) {
data = rng_ops->data_read();
have_data = rng_ops->n_bytes;
}
spin_unlock (&rng_lock);
while (have_data && size) {
if (put_user((u8)data, buf++)) {
ret = ret ? : -EFAULT;
break;
}
size--;
ret++;
have_data--;
data>>=8;
}
if (filp->f_flags & O_NONBLOCK)
return ret ? : -EAGAIN;
if(need_resched())
schedule_timeout_interruptible(1);
else
udelay(200); /* FIXME: We could poll for 250uS ?? */
if (signal_pending (current))
return ret ? : -ERESTARTSYS;
}
return ret;
}
/*
* rng_init_one - look for and attempt to init a single RNG
*/
static int __init rng_init_one (struct pci_dev *dev)
{
int rc;
DPRINTK ("ENTER\n");
assert(rng_ops != NULL);
rc = rng_ops->init(dev);
if (rc)
goto err_out;
rc = misc_register (&rng_miscdev);
if (rc) {
printk (KERN_ERR PFX "misc device register failed\n");
goto err_out_cleanup_hw;
}
DPRINTK ("EXIT, returning 0\n");
return 0;
err_out_cleanup_hw:
rng_ops->cleanup();
err_out:
DPRINTK ("EXIT, returning %d\n", rc);
return rc;
}
MODULE_AUTHOR("The Linux Kernel team");
MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
MODULE_LICENSE("GPL");
/*
* rng_init - initialize RNG module
*/
static int __init rng_init (void)
{
int rc;
struct pci_dev *pdev = NULL;
const struct pci_device_id *ent;
DPRINTK ("ENTER\n");
/* Probe for Intel, AMD RNGs */
for_each_pci_dev(pdev) {
ent = pci_match_id(rng_pci_tbl, pdev);
if (ent) {
rng_ops = &rng_vendor_ops[ent->driver_data];
goto match;
}
}
#ifdef __i386__
/* Probe for VIA RNG */
if (cpu_has_xstore) {
rng_ops = &rng_vendor_ops[rng_hw_via];
pdev = NULL;
goto match;
}
#endif
DPRINTK ("EXIT, returning -ENODEV\n");
return -ENODEV;
match:
rc = rng_init_one (pdev);
if (rc)
return rc;
pr_info( RNG_DRIVER_NAME " loaded\n");
DPRINTK ("EXIT, returning 0\n");
return 0;
}
/*
* rng_init - shutdown RNG module
*/
static void __exit rng_cleanup (void)
{
DPRINTK ("ENTER\n");
misc_deregister (&rng_miscdev);
if (rng_ops->cleanup)
rng_ops->cleanup();
DPRINTK ("EXIT\n");
}
module_init (rng_init);
module_exit (rng_cleanup);
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