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-rw-r--r--drivers/char/hw_random/Kconfig13
-rw-r--r--drivers/char/hw_random/Makefile1
-rw-r--r--drivers/char/hw_random/via-rng.c183
3 files changed, 197 insertions, 0 deletions
diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index defe68736959..01e2691d568c 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -48,3 +48,16 @@ config HW_RANDOM_GEODE
48 module will be called geode-rng. 48 module will be called geode-rng.
49 49
50 If unsure, say Y. 50 If unsure, say Y.
51
52config HW_RANDOM_VIA
53 tristate "VIA HW Random Number Generator support"
54 depends on HW_RANDOM && X86_32
55 default y
56 ---help---
57 This driver provides kernel-side support for the Random Number
58 Generator hardware found on VIA based motherboards.
59
60 To compile this driver as a module, choose M here: the
61 module will be called via-rng.
62
63 If unsure, say Y.
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 19ff20e5fb1b..f03bdf23f7bc 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -6,3 +6,4 @@ obj-$(CONFIG_HW_RANDOM) += core.o
6obj-$(CONFIG_HW_RANDOM_INTEL) += intel-rng.o 6obj-$(CONFIG_HW_RANDOM_INTEL) += intel-rng.o
7obj-$(CONFIG_HW_RANDOM_AMD) += amd-rng.o 7obj-$(CONFIG_HW_RANDOM_AMD) += amd-rng.o
8obj-$(CONFIG_HW_RANDOM_GEODE) += geode-rng.o 8obj-$(CONFIG_HW_RANDOM_GEODE) += geode-rng.o
9obj-$(CONFIG_HW_RANDOM_VIA) += via-rng.o
diff --git a/drivers/char/hw_random/via-rng.c b/drivers/char/hw_random/via-rng.c
new file mode 100644
index 000000000000..0e786b617bb8
--- /dev/null
+++ b/drivers/char/hw_random/via-rng.c
@@ -0,0 +1,183 @@
1/*
2 * RNG driver for VIA RNGs
3 *
4 * Copyright 2005 (c) MontaVista Software, Inc.
5 *
6 * with the majority of the code coming from:
7 *
8 * Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
9 * (c) Copyright 2003 Red Hat Inc <jgarzik@redhat.com>
10 *
11 * derived from
12 *
13 * Hardware driver for the AMD 768 Random Number Generator (RNG)
14 * (c) Copyright 2001 Red Hat Inc <alan@redhat.com>
15 *
16 * derived from
17 *
18 * Hardware driver for Intel i810 Random Number Generator (RNG)
19 * Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com>
20 * Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>
21 *
22 * This file is licensed under the terms of the GNU General Public
23 * License version 2. This program is licensed "as is" without any
24 * warranty of any kind, whether express or implied.
25 */
26
27#include <linux/module.h>
28#include <linux/kernel.h>
29#include <linux/pci.h>
30#include <linux/hw_random.h>
31#include <asm/io.h>
32#include <asm/msr.h>
33#include <asm/cpufeature.h>
34
35
36#define PFX KBUILD_MODNAME ": "
37
38
39enum {
40 VIA_STRFILT_CNT_SHIFT = 16,
41 VIA_STRFILT_FAIL = (1 << 15),
42 VIA_STRFILT_ENABLE = (1 << 14),
43 VIA_RAWBITS_ENABLE = (1 << 13),
44 VIA_RNG_ENABLE = (1 << 6),
45 VIA_XSTORE_CNT_MASK = 0x0F,
46
47 VIA_RNG_CHUNK_8 = 0x00, /* 64 rand bits, 64 stored bits */
48 VIA_RNG_CHUNK_4 = 0x01, /* 32 rand bits, 32 stored bits */
49 VIA_RNG_CHUNK_4_MASK = 0xFFFFFFFF,
50 VIA_RNG_CHUNK_2 = 0x02, /* 16 rand bits, 32 stored bits */
51 VIA_RNG_CHUNK_2_MASK = 0xFFFF,
52 VIA_RNG_CHUNK_1 = 0x03, /* 8 rand bits, 32 stored bits */
53 VIA_RNG_CHUNK_1_MASK = 0xFF,
54};
55
56/*
57 * Investigate using the 'rep' prefix to obtain 32 bits of random data
58 * in one insn. The upside is potentially better performance. The
59 * downside is that the instruction becomes no longer atomic. Due to
60 * this, just like familiar issues with /dev/random itself, the worst
61 * case of a 'rep xstore' could potentially pause a cpu for an
62 * unreasonably long time. In practice, this condition would likely
63 * only occur when the hardware is failing. (or so we hope :))
64 *
65 * Another possible performance boost may come from simply buffering
66 * until we have 4 bytes, thus returning a u32 at a time,
67 * instead of the current u8-at-a-time.
68 */
69
70static inline u32 xstore(u32 *addr, u32 edx_in)
71{
72 u32 eax_out;
73
74 asm(".byte 0x0F,0xA7,0xC0 /* xstore %%edi (addr=%0) */"
75 :"=m"(*addr), "=a"(eax_out)
76 :"D"(addr), "d"(edx_in));
77
78 return eax_out;
79}
80
81static int via_rng_data_present(struct hwrng *rng)
82{
83 u32 bytes_out;
84 u32 *via_rng_datum = (u32 *)(&rng->priv);
85
86 /* We choose the recommended 1-byte-per-instruction RNG rate,
87 * for greater randomness at the expense of speed. Larger
88 * values 2, 4, or 8 bytes-per-instruction yield greater
89 * speed at lesser randomness.
90 *
91 * If you change this to another VIA_CHUNK_n, you must also
92 * change the ->n_bytes values in rng_vendor_ops[] tables.
93 * VIA_CHUNK_8 requires further code changes.
94 *
95 * A copy of MSR_VIA_RNG is placed in eax_out when xstore
96 * completes.
97 */
98
99 *via_rng_datum = 0; /* paranoia, not really necessary */
100 bytes_out = xstore(via_rng_datum, VIA_RNG_CHUNK_1);
101 bytes_out &= VIA_XSTORE_CNT_MASK;
102 if (bytes_out == 0)
103 return 0;
104 return 1;
105}
106
107static int via_rng_data_read(struct hwrng *rng, u32 *data)
108{
109 u32 via_rng_datum = (u32)rng->priv;
110
111 *data = via_rng_datum;
112
113 return 1;
114}
115
116static int via_rng_init(struct hwrng *rng)
117{
118 u32 lo, hi, old_lo;
119
120 /* Control the RNG via MSR. Tread lightly and pay very close
121 * close attention to values written, as the reserved fields
122 * are documented to be "undefined and unpredictable"; but it
123 * does not say to write them as zero, so I make a guess that
124 * we restore the values we find in the register.
125 */
126 rdmsr(MSR_VIA_RNG, lo, hi);
127
128 old_lo = lo;
129 lo &= ~(0x7f << VIA_STRFILT_CNT_SHIFT);
130 lo &= ~VIA_XSTORE_CNT_MASK;
131 lo &= ~(VIA_STRFILT_ENABLE | VIA_STRFILT_FAIL | VIA_RAWBITS_ENABLE);
132 lo |= VIA_RNG_ENABLE;
133
134 if (lo != old_lo)
135 wrmsr(MSR_VIA_RNG, lo, hi);
136
137 /* perhaps-unnecessary sanity check; remove after testing if
138 unneeded */
139 rdmsr(MSR_VIA_RNG, lo, hi);
140 if ((lo & VIA_RNG_ENABLE) == 0) {
141 printk(KERN_ERR PFX "cannot enable VIA C3 RNG, aborting\n");
142 return -ENODEV;
143 }
144
145 return 0;
146}
147
148
149static struct hwrng via_rng = {
150 .name = "via",
151 .init = via_rng_init,
152 .data_present = via_rng_data_present,
153 .data_read = via_rng_data_read,
154};
155
156
157static int __init mod_init(void)
158{
159 int err;
160
161 if (!cpu_has_xstore)
162 return -ENODEV;
163 printk(KERN_INFO "VIA RNG detected\n");
164 err = hwrng_register(&via_rng);
165 if (err) {
166 printk(KERN_ERR PFX "RNG registering failed (%d)\n",
167 err);
168 goto out;
169 }
170out:
171 return err;
172}
173
174static void __exit mod_exit(void)
175{
176 hwrng_unregister(&via_rng);
177}
178
179subsys_initcall(mod_init);
180module_exit(mod_exit);
181
182MODULE_DESCRIPTION("H/W RNG driver for VIA chipsets");
183MODULE_LICENSE("GPL");