Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 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) |
Alan Cox | 77122d0 | 2008-10-27 15:10:23 +0000 | [diff] [blame] | 14 | * (c) Copyright 2001 Red Hat Inc |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 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 | |
Herbert Xu | 55db838 | 2011-01-07 14:55:06 +1100 | [diff] [blame] | 27 | #include <crypto/padlock.h> |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 28 | #include <linux/module.h> |
| 29 | #include <linux/kernel.h> |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 30 | #include <linux/hw_random.h> |
Patrick McHardy | 984e976 | 2007-11-21 12:24:45 +0800 | [diff] [blame] | 31 | #include <linux/delay.h> |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 32 | #include <asm/io.h> |
| 33 | #include <asm/msr.h> |
| 34 | #include <asm/cpufeature.h> |
Suresh Siddha | e491401 | 2008-08-13 22:02:26 +1000 | [diff] [blame] | 35 | #include <asm/i387.h> |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 36 | |
| 37 | |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 38 | |
| 39 | |
| 40 | enum { |
| 41 | VIA_STRFILT_CNT_SHIFT = 16, |
| 42 | VIA_STRFILT_FAIL = (1 << 15), |
| 43 | VIA_STRFILT_ENABLE = (1 << 14), |
| 44 | VIA_RAWBITS_ENABLE = (1 << 13), |
| 45 | VIA_RNG_ENABLE = (1 << 6), |
Dave Jones | 11025e8 | 2008-02-06 01:37:13 -0800 | [diff] [blame] | 46 | VIA_NOISESRC1 = (1 << 8), |
| 47 | VIA_NOISESRC2 = (1 << 9), |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 48 | VIA_XSTORE_CNT_MASK = 0x0F, |
| 49 | |
| 50 | VIA_RNG_CHUNK_8 = 0x00, /* 64 rand bits, 64 stored bits */ |
| 51 | VIA_RNG_CHUNK_4 = 0x01, /* 32 rand bits, 32 stored bits */ |
| 52 | VIA_RNG_CHUNK_4_MASK = 0xFFFFFFFF, |
| 53 | VIA_RNG_CHUNK_2 = 0x02, /* 16 rand bits, 32 stored bits */ |
| 54 | VIA_RNG_CHUNK_2_MASK = 0xFFFF, |
| 55 | VIA_RNG_CHUNK_1 = 0x03, /* 8 rand bits, 32 stored bits */ |
| 56 | VIA_RNG_CHUNK_1_MASK = 0xFF, |
| 57 | }; |
| 58 | |
| 59 | /* |
| 60 | * Investigate using the 'rep' prefix to obtain 32 bits of random data |
| 61 | * in one insn. The upside is potentially better performance. The |
| 62 | * downside is that the instruction becomes no longer atomic. Due to |
| 63 | * this, just like familiar issues with /dev/random itself, the worst |
| 64 | * case of a 'rep xstore' could potentially pause a cpu for an |
| 65 | * unreasonably long time. In practice, this condition would likely |
| 66 | * only occur when the hardware is failing. (or so we hope :)) |
| 67 | * |
| 68 | * Another possible performance boost may come from simply buffering |
| 69 | * until we have 4 bytes, thus returning a u32 at a time, |
| 70 | * instead of the current u8-at-a-time. |
Suresh Siddha | e491401 | 2008-08-13 22:02:26 +1000 | [diff] [blame] | 71 | * |
| 72 | * Padlock instructions can generate a spurious DNA fault, so |
| 73 | * we have to call them in the context of irq_ts_save/restore() |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 74 | */ |
| 75 | |
| 76 | static inline u32 xstore(u32 *addr, u32 edx_in) |
| 77 | { |
| 78 | u32 eax_out; |
Suresh Siddha | e491401 | 2008-08-13 22:02:26 +1000 | [diff] [blame] | 79 | int ts_state; |
| 80 | |
| 81 | ts_state = irq_ts_save(); |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 82 | |
| 83 | asm(".byte 0x0F,0xA7,0xC0 /* xstore %%edi (addr=%0) */" |
Herbert Xu | 0735ac1 | 2011-01-07 14:48:57 +1100 | [diff] [blame] | 84 | : "=m" (*addr), "=a" (eax_out), "+d" (edx_in), "+D" (addr)); |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 85 | |
Suresh Siddha | e491401 | 2008-08-13 22:02:26 +1000 | [diff] [blame] | 86 | irq_ts_restore(ts_state); |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 87 | return eax_out; |
| 88 | } |
| 89 | |
Patrick McHardy | 984e976 | 2007-11-21 12:24:45 +0800 | [diff] [blame] | 90 | static int via_rng_data_present(struct hwrng *rng, int wait) |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 91 | { |
Herbert Xu | 55db838 | 2011-01-07 14:55:06 +1100 | [diff] [blame] | 92 | char buf[16 + PADLOCK_ALIGNMENT - STACK_ALIGN] __attribute__ |
| 93 | ((aligned(STACK_ALIGN))); |
| 94 | u32 *via_rng_datum = (u32 *)PTR_ALIGN(&buf[0], PADLOCK_ALIGNMENT); |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 95 | u32 bytes_out; |
Patrick McHardy | 984e976 | 2007-11-21 12:24:45 +0800 | [diff] [blame] | 96 | int i; |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 97 | |
| 98 | /* We choose the recommended 1-byte-per-instruction RNG rate, |
| 99 | * for greater randomness at the expense of speed. Larger |
| 100 | * values 2, 4, or 8 bytes-per-instruction yield greater |
| 101 | * speed at lesser randomness. |
| 102 | * |
| 103 | * If you change this to another VIA_CHUNK_n, you must also |
| 104 | * change the ->n_bytes values in rng_vendor_ops[] tables. |
| 105 | * VIA_CHUNK_8 requires further code changes. |
| 106 | * |
| 107 | * A copy of MSR_VIA_RNG is placed in eax_out when xstore |
| 108 | * completes. |
| 109 | */ |
| 110 | |
Patrick McHardy | 984e976 | 2007-11-21 12:24:45 +0800 | [diff] [blame] | 111 | for (i = 0; i < 20; i++) { |
| 112 | *via_rng_datum = 0; /* paranoia, not really necessary */ |
| 113 | bytes_out = xstore(via_rng_datum, VIA_RNG_CHUNK_1); |
| 114 | bytes_out &= VIA_XSTORE_CNT_MASK; |
| 115 | if (bytes_out || !wait) |
| 116 | break; |
| 117 | udelay(10); |
| 118 | } |
Herbert Xu | 55db838 | 2011-01-07 14:55:06 +1100 | [diff] [blame] | 119 | rng->priv = *via_rng_datum; |
Patrick McHardy | 984e976 | 2007-11-21 12:24:45 +0800 | [diff] [blame] | 120 | return bytes_out ? 1 : 0; |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 121 | } |
| 122 | |
| 123 | static int via_rng_data_read(struct hwrng *rng, u32 *data) |
| 124 | { |
| 125 | u32 via_rng_datum = (u32)rng->priv; |
| 126 | |
| 127 | *data = via_rng_datum; |
| 128 | |
| 129 | return 1; |
| 130 | } |
| 131 | |
| 132 | static int via_rng_init(struct hwrng *rng) |
| 133 | { |
Dave Jones | 11025e8 | 2008-02-06 01:37:13 -0800 | [diff] [blame] | 134 | struct cpuinfo_x86 *c = &cpu_data(0); |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 135 | u32 lo, hi, old_lo; |
| 136 | |
Harald Welte | 858576b | 2009-05-15 16:00:32 +1000 | [diff] [blame] | 137 | /* VIA Nano CPUs don't have the MSR_VIA_RNG anymore. The RNG |
| 138 | * is always enabled if CPUID rng_en is set. There is no |
| 139 | * RNG configuration like it used to be the case in this |
| 140 | * register */ |
| 141 | if ((c->x86 == 6) && (c->x86_model >= 0x0f)) { |
| 142 | if (!cpu_has_xstore_enabled) { |
| 143 | printk(KERN_ERR PFX "can't enable hardware RNG " |
| 144 | "if XSTORE is not enabled\n"); |
| 145 | return -ENODEV; |
| 146 | } |
| 147 | return 0; |
| 148 | } |
| 149 | |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 150 | /* Control the RNG via MSR. Tread lightly and pay very close |
| 151 | * close attention to values written, as the reserved fields |
| 152 | * are documented to be "undefined and unpredictable"; but it |
| 153 | * does not say to write them as zero, so I make a guess that |
| 154 | * we restore the values we find in the register. |
| 155 | */ |
| 156 | rdmsr(MSR_VIA_RNG, lo, hi); |
| 157 | |
| 158 | old_lo = lo; |
| 159 | lo &= ~(0x7f << VIA_STRFILT_CNT_SHIFT); |
| 160 | lo &= ~VIA_XSTORE_CNT_MASK; |
| 161 | lo &= ~(VIA_STRFILT_ENABLE | VIA_STRFILT_FAIL | VIA_RAWBITS_ENABLE); |
| 162 | lo |= VIA_RNG_ENABLE; |
Dave Jones | 11025e8 | 2008-02-06 01:37:13 -0800 | [diff] [blame] | 163 | lo |= VIA_NOISESRC1; |
| 164 | |
| 165 | /* Enable secondary noise source on CPUs where it is present. */ |
| 166 | |
| 167 | /* Nehemiah stepping 8 and higher */ |
| 168 | if ((c->x86_model == 9) && (c->x86_mask > 7)) |
| 169 | lo |= VIA_NOISESRC2; |
| 170 | |
| 171 | /* Esther */ |
| 172 | if (c->x86_model >= 10) |
| 173 | lo |= VIA_NOISESRC2; |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 174 | |
| 175 | if (lo != old_lo) |
| 176 | wrmsr(MSR_VIA_RNG, lo, hi); |
| 177 | |
| 178 | /* perhaps-unnecessary sanity check; remove after testing if |
| 179 | unneeded */ |
| 180 | rdmsr(MSR_VIA_RNG, lo, hi); |
| 181 | if ((lo & VIA_RNG_ENABLE) == 0) { |
| 182 | printk(KERN_ERR PFX "cannot enable VIA C3 RNG, aborting\n"); |
| 183 | return -ENODEV; |
| 184 | } |
| 185 | |
| 186 | return 0; |
| 187 | } |
| 188 | |
| 189 | |
| 190 | static struct hwrng via_rng = { |
| 191 | .name = "via", |
| 192 | .init = via_rng_init, |
| 193 | .data_present = via_rng_data_present, |
| 194 | .data_read = via_rng_data_read, |
| 195 | }; |
| 196 | |
| 197 | |
| 198 | static int __init mod_init(void) |
| 199 | { |
| 200 | int err; |
| 201 | |
| 202 | if (!cpu_has_xstore) |
| 203 | return -ENODEV; |
| 204 | printk(KERN_INFO "VIA RNG detected\n"); |
| 205 | err = hwrng_register(&via_rng); |
| 206 | if (err) { |
| 207 | printk(KERN_ERR PFX "RNG registering failed (%d)\n", |
| 208 | err); |
| 209 | goto out; |
| 210 | } |
| 211 | out: |
| 212 | return err; |
| 213 | } |
| 214 | |
| 215 | static void __exit mod_exit(void) |
| 216 | { |
| 217 | hwrng_unregister(&via_rng); |
| 218 | } |
| 219 | |
Michael Buesch | 56fb5fe | 2007-01-10 23:15:43 -0800 | [diff] [blame] | 220 | module_init(mod_init); |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 221 | module_exit(mod_exit); |
| 222 | |
Harald Welte | 608d1cd | 2009-05-15 15:57:35 +1000 | [diff] [blame] | 223 | MODULE_DESCRIPTION("H/W RNG driver for VIA CPU with PadLock"); |
Michael Buesch | 1352336 | 2006-06-26 00:25:02 -0700 | [diff] [blame] | 224 | MODULE_LICENSE("GPL"); |