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
20 static 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
34 static 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
48 static 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
53 static 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
59 void x86_init_rdrand(struct cpuinfo_x86 *c);
60 #endif
61
62 #endif /* ASM_X86_ARCHRANDOM_H */
63
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