arch/x86/include/asm/archrandom.h

/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * This file is part of the Linux kernel.
 *
 * Copyright (c) 2011-2014, Intel Corporation
 * Authors: Fenghua Yu <fenghua.yu@intel.com>,
 *          H. Peter Anvin <hpa@linux.intel.com>
 */

#ifndef ASM_X86_ARCHRANDOM_H
#define ASM_X86_ARCHRANDOM_H

#include <asm/processor.h>
#include <asm/cpufeature.h>

#define RDRAND_RETRY_LOOPS	10

/* Unconditional execution of RDRAND and RDSEED */

static inline bool __must_check rdrand_long(unsigned long *v)
{
	bool ok;
	unsigned int retry = RDRAND_RETRY_LOOPS;
	do {
		asm volatile("rdrand %[out]"
			     : "=@ccc" (ok), [out] "=r" (*v));
		if (ok)
			return true;
	} while (--retry);
	return false;
}

static inline bool __must_check rdseed_long(unsigned long *v)
{
	bool ok;
	asm volatile("rdseed %[out]"
		     : "=@ccc" (ok), [out] "=r" (*v));
	return ok;
}

/*
 * These are the generic interfaces; they must not be declared if the
 * stubs in <linux/random.h> are to be invoked.
 */

static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
{
	return max_longs && cpu_feature_enabled(X86_FEATURE_RDRAND) && rdrand_long(v) ? 1 : 0;
}

static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
{
	return max_longs && cpu_feature_enabled(X86_FEATURE_RDSEED) && rdseed_long(v) ? 1 : 0;
}

#ifndef CONFIG_UML
void x86_init_rdrand(struct cpuinfo_x86 *c);
#endif

#endif /* ASM_X86_ARCHRANDOM_H */