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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) | |
77122d0b | 14 | * (c) Copyright 2001 Red Hat Inc |
13523363 MB |
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 | ||
55db8387 | 27 | #include <crypto/padlock.h> |
13523363 MB |
28 | #include <linux/module.h> |
29 | #include <linux/kernel.h> | |
13523363 | 30 | #include <linux/hw_random.h> |
984e976f | 31 | #include <linux/delay.h> |
ff6f83fc | 32 | #include <asm/cpu_device_id.h> |
13523363 MB |
33 | #include <asm/io.h> |
34 | #include <asm/msr.h> | |
35 | #include <asm/cpufeature.h> | |
df6b35f4 | 36 | #include <asm/fpu/api.h> |
13523363 MB |
37 | |
38 | ||
13523363 MB |
39 | |
40 | ||
41 | enum { | |
42 | VIA_STRFILT_CNT_SHIFT = 16, | |
43 | VIA_STRFILT_FAIL = (1 << 15), | |
44 | VIA_STRFILT_ENABLE = (1 << 14), | |
45 | VIA_RAWBITS_ENABLE = (1 << 13), | |
46 | VIA_RNG_ENABLE = (1 << 6), | |
11025e85 DJ |
47 | VIA_NOISESRC1 = (1 << 8), |
48 | VIA_NOISESRC2 = (1 << 9), | |
13523363 MB |
49 | VIA_XSTORE_CNT_MASK = 0x0F, |
50 | ||
51 | VIA_RNG_CHUNK_8 = 0x00, /* 64 rand bits, 64 stored bits */ | |
52 | VIA_RNG_CHUNK_4 = 0x01, /* 32 rand bits, 32 stored bits */ | |
53 | VIA_RNG_CHUNK_4_MASK = 0xFFFFFFFF, | |
54 | VIA_RNG_CHUNK_2 = 0x02, /* 16 rand bits, 32 stored bits */ | |
55 | VIA_RNG_CHUNK_2_MASK = 0xFFFF, | |
56 | VIA_RNG_CHUNK_1 = 0x03, /* 8 rand bits, 32 stored bits */ | |
57 | VIA_RNG_CHUNK_1_MASK = 0xFF, | |
58 | }; | |
59 | ||
60 | /* | |
61 | * Investigate using the 'rep' prefix to obtain 32 bits of random data | |
62 | * in one insn. The upside is potentially better performance. The | |
63 | * downside is that the instruction becomes no longer atomic. Due to | |
64 | * this, just like familiar issues with /dev/random itself, the worst | |
65 | * case of a 'rep xstore' could potentially pause a cpu for an | |
66 | * unreasonably long time. In practice, this condition would likely | |
67 | * only occur when the hardware is failing. (or so we hope :)) | |
68 | * | |
69 | * Another possible performance boost may come from simply buffering | |
70 | * until we have 4 bytes, thus returning a u32 at a time, | |
71 | * instead of the current u8-at-a-time. | |
e4914012 SS |
72 | * |
73 | * Padlock instructions can generate a spurious DNA fault, so | |
74 | * we have to call them in the context of irq_ts_save/restore() | |
13523363 MB |
75 | */ |
76 | ||
77 | static inline u32 xstore(u32 *addr, u32 edx_in) | |
78 | { | |
79 | u32 eax_out; | |
e4914012 SS |
80 | int ts_state; |
81 | ||
82 | ts_state = irq_ts_save(); | |
13523363 MB |
83 | |
84 | asm(".byte 0x0F,0xA7,0xC0 /* xstore %%edi (addr=%0) */" | |
0735ac1f | 85 | : "=m" (*addr), "=a" (eax_out), "+d" (edx_in), "+D" (addr)); |
13523363 | 86 | |
e4914012 | 87 | irq_ts_restore(ts_state); |
13523363 MB |
88 | return eax_out; |
89 | } | |
90 | ||
984e976f | 91 | static int via_rng_data_present(struct hwrng *rng, int wait) |
13523363 | 92 | { |
55db8387 HX |
93 | char buf[16 + PADLOCK_ALIGNMENT - STACK_ALIGN] __attribute__ |
94 | ((aligned(STACK_ALIGN))); | |
95 | u32 *via_rng_datum = (u32 *)PTR_ALIGN(&buf[0], PADLOCK_ALIGNMENT); | |
13523363 | 96 | u32 bytes_out; |
984e976f | 97 | int i; |
13523363 MB |
98 | |
99 | /* We choose the recommended 1-byte-per-instruction RNG rate, | |
100 | * for greater randomness at the expense of speed. Larger | |
101 | * values 2, 4, or 8 bytes-per-instruction yield greater | |
102 | * speed at lesser randomness. | |
103 | * | |
104 | * If you change this to another VIA_CHUNK_n, you must also | |
105 | * change the ->n_bytes values in rng_vendor_ops[] tables. | |
106 | * VIA_CHUNK_8 requires further code changes. | |
107 | * | |
108 | * A copy of MSR_VIA_RNG is placed in eax_out when xstore | |
109 | * completes. | |
110 | */ | |
111 | ||
984e976f PM |
112 | for (i = 0; i < 20; i++) { |
113 | *via_rng_datum = 0; /* paranoia, not really necessary */ | |
114 | bytes_out = xstore(via_rng_datum, VIA_RNG_CHUNK_1); | |
115 | bytes_out &= VIA_XSTORE_CNT_MASK; | |
116 | if (bytes_out || !wait) | |
117 | break; | |
118 | udelay(10); | |
119 | } | |
55db8387 | 120 | rng->priv = *via_rng_datum; |
984e976f | 121 | return bytes_out ? 1 : 0; |
13523363 MB |
122 | } |
123 | ||
124 | static int via_rng_data_read(struct hwrng *rng, u32 *data) | |
125 | { | |
126 | u32 via_rng_datum = (u32)rng->priv; | |
127 | ||
128 | *data = via_rng_datum; | |
129 | ||
130 | return 1; | |
131 | } | |
132 | ||
133 | static int via_rng_init(struct hwrng *rng) | |
134 | { | |
11025e85 | 135 | struct cpuinfo_x86 *c = &cpu_data(0); |
13523363 MB |
136 | u32 lo, hi, old_lo; |
137 | ||
858576bd HW |
138 | /* VIA Nano CPUs don't have the MSR_VIA_RNG anymore. The RNG |
139 | * is always enabled if CPUID rng_en is set. There is no | |
140 | * RNG configuration like it used to be the case in this | |
141 | * register */ | |
142 | if ((c->x86 == 6) && (c->x86_model >= 0x0f)) { | |
362f924b | 143 | if (!boot_cpu_has(X86_FEATURE_XSTORE_EN)) { |
7a1ae9c0 | 144 | pr_err(PFX "can't enable hardware RNG " |
858576bd HW |
145 | "if XSTORE is not enabled\n"); |
146 | return -ENODEV; | |
147 | } | |
148 | return 0; | |
149 | } | |
150 | ||
13523363 MB |
151 | /* Control the RNG via MSR. Tread lightly and pay very close |
152 | * close attention to values written, as the reserved fields | |
153 | * are documented to be "undefined and unpredictable"; but it | |
154 | * does not say to write them as zero, so I make a guess that | |
155 | * we restore the values we find in the register. | |
156 | */ | |
157 | rdmsr(MSR_VIA_RNG, lo, hi); | |
158 | ||
159 | old_lo = lo; | |
160 | lo &= ~(0x7f << VIA_STRFILT_CNT_SHIFT); | |
161 | lo &= ~VIA_XSTORE_CNT_MASK; | |
162 | lo &= ~(VIA_STRFILT_ENABLE | VIA_STRFILT_FAIL | VIA_RAWBITS_ENABLE); | |
163 | lo |= VIA_RNG_ENABLE; | |
11025e85 DJ |
164 | lo |= VIA_NOISESRC1; |
165 | ||
166 | /* Enable secondary noise source on CPUs where it is present. */ | |
167 | ||
168 | /* Nehemiah stepping 8 and higher */ | |
169 | if ((c->x86_model == 9) && (c->x86_mask > 7)) | |
170 | lo |= VIA_NOISESRC2; | |
171 | ||
172 | /* Esther */ | |
173 | if (c->x86_model >= 10) | |
174 | lo |= VIA_NOISESRC2; | |
13523363 MB |
175 | |
176 | if (lo != old_lo) | |
177 | wrmsr(MSR_VIA_RNG, lo, hi); | |
178 | ||
179 | /* perhaps-unnecessary sanity check; remove after testing if | |
180 | unneeded */ | |
181 | rdmsr(MSR_VIA_RNG, lo, hi); | |
182 | if ((lo & VIA_RNG_ENABLE) == 0) { | |
7a1ae9c0 | 183 | pr_err(PFX "cannot enable VIA C3 RNG, aborting\n"); |
13523363 MB |
184 | return -ENODEV; |
185 | } | |
186 | ||
187 | return 0; | |
188 | } | |
189 | ||
190 | ||
191 | static struct hwrng via_rng = { | |
192 | .name = "via", | |
193 | .init = via_rng_init, | |
194 | .data_present = via_rng_data_present, | |
195 | .data_read = via_rng_data_read, | |
196 | }; | |
197 | ||
198 | ||
199 | static int __init mod_init(void) | |
200 | { | |
201 | int err; | |
202 | ||
362f924b | 203 | if (!boot_cpu_has(X86_FEATURE_XSTORE)) |
13523363 | 204 | return -ENODEV; |
362f924b | 205 | |
7a1ae9c0 | 206 | pr_info("VIA RNG detected\n"); |
13523363 MB |
207 | err = hwrng_register(&via_rng); |
208 | if (err) { | |
7a1ae9c0 | 209 | pr_err(PFX "RNG registering failed (%d)\n", |
13523363 MB |
210 | err); |
211 | goto out; | |
212 | } | |
213 | out: | |
214 | return err; | |
215 | } | |
216 | ||
217 | static void __exit mod_exit(void) | |
218 | { | |
219 | hwrng_unregister(&via_rng); | |
220 | } | |
221 | ||
56fb5fe9 | 222 | module_init(mod_init); |
13523363 MB |
223 | module_exit(mod_exit); |
224 | ||
a44bc80e | 225 | static struct x86_cpu_id __maybe_unused via_rng_cpu_id[] = { |
ff6f83fc BH |
226 | X86_FEATURE_MATCH(X86_FEATURE_XSTORE), |
227 | {} | |
228 | }; | |
229 | ||
608d1cd5 | 230 | MODULE_DESCRIPTION("H/W RNG driver for VIA CPU with PadLock"); |
13523363 | 231 | MODULE_LICENSE("GPL"); |
ff6f83fc | 232 | MODULE_DEVICE_TABLE(x86cpu, via_rng_cpu_id); |