linux/drivers/char/hw_random/via-rng.c

/*
 * RNG driver for VIA RNGs
 *
 * Copyright 2005 (c) MontaVista Software, Inc.
 *
 * with the majority of the code coming from:
 *
 * Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
 * (c) Copyright 2003 Red Hat Inc <[email protected]>
 *
 * derived from
 *
 * Hardware driver for the AMD 768 Random Number Generator (RNG)
 * (c) Copyright 2001 Red Hat Inc
 *
 * derived from
 *
 * Hardware driver for Intel i810 Random Number Generator (RNG)
 * Copyright 2000,2001 Jeff Garzik <[email protected]>
 * Copyright 2000,2001 Philipp Rumpf <[email protected]>
 *
 * This file is licensed under  the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <crypto/padlock.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/hw_random.h>
#include <linux/delay.h>
#include <asm/cpu_device_id.h>
#include <asm/io.h>
#include <asm/msr.h>
#include <asm/cpufeature.h>
#include <asm/fpu/api.h>




enum { … };

/*
 * 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.
 *
 * Padlock instructions can generate a spurious DNA fault, but the
 * kernel doesn't use CR0.TS, so this doesn't matter.
 */

static inline u32 xstore(u32 *addr, u32 edx_in)
{ … }

static int via_rng_data_present(struct hwrng *rng, int wait)
{ … }

static int via_rng_data_read(struct hwrng *rng, u32 *data)
{ … }

static int via_rng_init(struct hwrng *rng)
{ … }


static struct hwrng via_rng = …;


static int __init via_rng_mod_init(void)
{ … }
module_init(…) …;

static void __exit via_rng_mod_exit(void)
{ … }
module_exit(via_rng_mod_exit);

static struct x86_cpu_id __maybe_unused via_rng_cpu_id[] = …;
MODULE_DEVICE_TABLE(x86cpu, via_rng_cpu_id);

MODULE_DESCRIPTION(…) …;
MODULE_LICENSE(…) …;