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 
rdrand_long(unsigned long * v)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 
rdseed_long(unsigned long * v)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 
arch_get_random_longs(unsigned long * v,size_t max_longs)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 
arch_get_random_seed_longs(unsigned long * v,size_t max_longs)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