archrandom.h

 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			     : "=@ccc" (ok), [out] "=r" (*v));
27		if (ok)
28			return true;
29	} while (--retry);
30	return false;
31}
32
33static inline bool __must_check rdseed_long(unsigned long *v)
34{
35	bool ok;
36	asm volatile("rdseed %[out]"
37		     : "=@ccc" (ok), [out] "=r" (*v));
38	return ok;
39}
40
41/*
42 * These are the generic interfaces; they must not be declared if the
43 * stubs in <linux/random.h> are to be invoked.
44 */
45
46static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
47{
48	return max_longs && static_cpu_has(X86_FEATURE_RDRAND) && rdrand_long(v) ? 1 : 0;
49}
50
51static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
52{
53	return max_longs && static_cpu_has(X86_FEATURE_RDSEED) && rdseed_long(v) ? 1 : 0;
54}
55
56#ifndef CONFIG_UML
57void x86_init_rdrand(struct cpuinfo_x86 *c);
58#endif
59
60#endif /* ASM_X86_ARCHRANDOM_H */