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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. */
46 static 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 */
60 static 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)                     \
70 static 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)                       \
87 static 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
101 GET_RANDOM(arch_get_random_long, unsigned long, RDRAND_LONG, ASM_NOP5);
102 GET_RANDOM(arch_get_random_int, unsigned int, RDRAND_INT, ASM_NOP4);
103
104 GET_SEED(arch_get_random_seed_long, unsigned long, RDSEED_LONG, ASM_NOP5);
105 GET_SEED(arch_get_random_seed_int, unsigned int, RDSEED_INT, ASM_NOP4);
106
107 #else
108
109 GET_RANDOM(arch_get_random_long, unsigned long, RDRAND_LONG, ASM_NOP3);
110 GET_RANDOM(arch_get_random_int, unsigned int, RDRAND_INT, ASM_NOP3);
111
112 GET_SEED(arch_get_random_seed_long, unsigned long, RDSEED_LONG, ASM_NOP4);
113 GET_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
122 static inline int rdrand_long(unsigned long *v)
123 {
124         return 0;
125 }
126
127 static inline bool rdseed_long(unsigned long *v)
128 {
129         return 0;
130 }
131
132 #endif  /* CONFIG_ARCH_RANDOM */
133
134 extern void x86_init_rdrand(struct cpuinfo_x86 *c);
135
136 #endif /* ASM_X86_ARCHRANDOM_H */