include/asm/archrandom.h

0001 /* SPDX-License-Identifier: GPL-2.0-only */
0002 /*
0003  * This file is part of the Linux kernel.
0004  *
0005  * Copyright (c) 2011-2014, Intel Corporation
0006  * Authors: Fenghua Yu <fenghua.yu@intel.com>,
0007  *          H. Peter Anvin <hpa@linux.intel.com>
0008  */
0009
0010 #ifndef ASM_X86_ARCHRANDOM_H
0011 #define ASM_X86_ARCHRANDOM_H
0012
0013 #include <asm/processor.h>
0014 #include <asm/cpufeature.h>
0015
0016 #define RDRAND_RETRY_LOOPS  10
0017
0018 /* Unconditional execution of RDRAND and RDSEED */
0019
0020 static inline bool __must_check rdrand_long(unsigned long *v)
0021 {
0022     bool ok;
0023     unsigned int retry = RDRAND_RETRY_LOOPS;
0024     do {
0025         asm volatile("rdrand %[out]"
0026                  CC_SET(c)
0027                  : CC_OUT(c) (ok), [out] "=r" (*v));
0028         if (ok)
0029             return true;
0030     } while (--retry);
0031     return false;
0032 }
0033
0034 static inline bool __must_check rdseed_long(unsigned long *v)
0035 {
0036     bool ok;
0037     asm volatile("rdseed %[out]"
0038              CC_SET(c)
0039              : CC_OUT(c) (ok), [out] "=r" (*v));
0040     return ok;
0041 }
0042
0043 /*
0044  * These are the generic interfaces; they must not be declared if the
0045  * stubs in <linux/random.h> are to be invoked.
0046  */
0047
0048 static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
0049 {
0050     return max_longs && static_cpu_has(X86_FEATURE_RDRAND) && rdrand_long(v) ? 1 : 0;
0051 }
0052
0053 static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
0054 {
0055     return max_longs && static_cpu_has(X86_FEATURE_RDSEED) && rdseed_long(v) ? 1 : 0;
0056 }
0057
0058 #ifndef CONFIG_UML
0059 void x86_init_rdrand(struct cpuinfo_x86 *c);
0060 #endif
0061
0062 #endif /* ASM_X86_ARCHRANDOM_H */