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1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * This file is part of the Linux kernel.
4 *
5 * Copyright (c) 2011-2014, Intel Corporation
6 * Authors: Fenghua Yu <fenghua.yu@intel.com>,
7 * H. Peter Anvin <hpa@linux.intel.com>
8 */
9
10#ifndef ASM_X86_ARCHRANDOM_H
11#define ASM_X86_ARCHRANDOM_H
12
13#include <asm/processor.h>
14#include <asm/cpufeature.h>
15
16#define RDRAND_RETRY_LOOPS 10
17
18/* Unconditional execution of RDRAND and RDSEED */
19
20static inline bool __must_check rdrand_long(unsigned long *v)
21{
22 bool ok;
23 unsigned int retry = RDRAND_RETRY_LOOPS;
24 do {
25 asm volatile("rdrand %[out]"
26 CC_SET(c)
27 : CC_OUT(c) (ok), [out] "=r" (*v));
28 if (ok)
29 return true;
30 } while (--retry);
31 return false;
32}
33
34static inline bool __must_check rdseed_long(unsigned long *v)
35{
36 bool ok;
37 asm volatile("rdseed %[out]"
38 CC_SET(c)
39 : CC_OUT(c) (ok), [out] "=r" (*v));
40 return ok;
41}
42
43/*
44 * These are the generic interfaces; they must not be declared if the
45 * stubs in <linux/random.h> are to be invoked.
46 */
47
48static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
49{
50 return max_longs && static_cpu_has(X86_FEATURE_RDRAND) && rdrand_long(v) ? 1 : 0;
51}
52
53static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
54{
55 return max_longs && static_cpu_has(X86_FEATURE_RDSEED) && rdseed_long(v) ? 1 : 0;
56}
57
58#ifndef CONFIG_UML
59void x86_init_rdrand(struct cpuinfo_x86 *c);
60#endif
61
62#endif /* ASM_X86_ARCHRANDOM_H */
1/*
2 * This file is part of the Linux kernel.
3 *
4 * Copyright (c) 2011-2014, Intel Corporation
5 * Authors: Fenghua Yu <fenghua.yu@intel.com>,
6 * H. Peter Anvin <hpa@linux.intel.com>
7 *
8 * This program is free software; you can redistribute it and/or modify it
9 * under the terms and conditions of the GNU General Public License,
10 * version 2, as published by the Free Software Foundation.
11 *
12 * This program is distributed in the hope it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
15 * more details.
16 *
17 * You should have received a copy of the GNU General Public License along with
18 * this program; if not, write to the Free Software Foundation, Inc.,
19 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 */
22
23#ifndef ASM_X86_ARCHRANDOM_H
24#define ASM_X86_ARCHRANDOM_H
25
26#include <asm/processor.h>
27#include <asm/cpufeature.h>
28#include <asm/alternative.h>
29#include <asm/nops.h>
30
31#define RDRAND_RETRY_LOOPS 10
32
33#define RDRAND_INT ".byte 0x0f,0xc7,0xf0"
34#define RDSEED_INT ".byte 0x0f,0xc7,0xf8"
35#ifdef CONFIG_X86_64
36# define RDRAND_LONG ".byte 0x48,0x0f,0xc7,0xf0"
37# define RDSEED_LONG ".byte 0x48,0x0f,0xc7,0xf8"
38#else
39# define RDRAND_LONG RDRAND_INT
40# define RDSEED_LONG RDSEED_INT
41#endif
42
43#ifdef CONFIG_ARCH_RANDOM
44
45/* Instead of arch_get_random_long() when alternatives haven't run. */
46static inline int rdrand_long(unsigned long *v)
47{
48 int ok;
49 asm volatile("1: " RDRAND_LONG "\n\t"
50 "jc 2f\n\t"
51 "decl %0\n\t"
52 "jnz 1b\n\t"
53 "2:"
54 : "=r" (ok), "=a" (*v)
55 : "0" (RDRAND_RETRY_LOOPS));
56 return ok;
57}
58
59/* A single attempt at RDSEED */
60static inline bool rdseed_long(unsigned long *v)
61{
62 unsigned char ok;
63 asm volatile(RDSEED_LONG "\n\t"
64 "setc %0"
65 : "=qm" (ok), "=a" (*v));
66 return ok;
67}
68
69#define GET_RANDOM(name, type, rdrand, nop) \
70static inline int name(type *v) \
71{ \
72 int ok; \
73 alternative_io("movl $0, %0\n\t" \
74 nop, \
75 "\n1: " rdrand "\n\t" \
76 "jc 2f\n\t" \
77 "decl %0\n\t" \
78 "jnz 1b\n\t" \
79 "2:", \
80 X86_FEATURE_RDRAND, \
81 ASM_OUTPUT2("=r" (ok), "=a" (*v)), \
82 "0" (RDRAND_RETRY_LOOPS)); \
83 return ok; \
84}
85
86#define GET_SEED(name, type, rdseed, nop) \
87static inline int name(type *v) \
88{ \
89 unsigned char ok; \
90 alternative_io("movb $0, %0\n\t" \
91 nop, \
92 rdseed "\n\t" \
93 "setc %0", \
94 X86_FEATURE_RDSEED, \
95 ASM_OUTPUT2("=q" (ok), "=a" (*v))); \
96 return ok; \
97}
98
99#ifdef CONFIG_X86_64
100
101GET_RANDOM(arch_get_random_long, unsigned long, RDRAND_LONG, ASM_NOP5);
102GET_RANDOM(arch_get_random_int, unsigned int, RDRAND_INT, ASM_NOP4);
103
104GET_SEED(arch_get_random_seed_long, unsigned long, RDSEED_LONG, ASM_NOP5);
105GET_SEED(arch_get_random_seed_int, unsigned int, RDSEED_INT, ASM_NOP4);
106
107#else
108
109GET_RANDOM(arch_get_random_long, unsigned long, RDRAND_LONG, ASM_NOP3);
110GET_RANDOM(arch_get_random_int, unsigned int, RDRAND_INT, ASM_NOP3);
111
112GET_SEED(arch_get_random_seed_long, unsigned long, RDSEED_LONG, ASM_NOP4);
113GET_SEED(arch_get_random_seed_int, unsigned int, RDSEED_INT, ASM_NOP4);
114
115#endif /* CONFIG_X86_64 */
116
117#define arch_has_random() static_cpu_has(X86_FEATURE_RDRAND)
118#define arch_has_random_seed() static_cpu_has(X86_FEATURE_RDSEED)
119
120#else
121
122static inline int rdrand_long(unsigned long *v)
123{
124 return 0;
125}
126
127static inline bool rdseed_long(unsigned long *v)
128{
129 return 0;
130}
131
132#endif /* CONFIG_ARCH_RANDOM */
133
134extern void x86_init_rdrand(struct cpuinfo_x86 *c);
135
136#endif /* ASM_X86_ARCHRANDOM_H */