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 */
137