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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_ARCHRANDOM_H
#define _ASM_ARCHRANDOM_H
#ifdef CONFIG_ARCH_RANDOM
#include <linux/bug.h>
#include <linux/kernel.h>
#include <asm/cpufeature.h>
static inline bool __arm64_rndr(unsigned long *v)
{
bool ok;
/*
* Reads of RNDR set PSTATE.NZCV to 0b0000 on success,
* and set PSTATE.NZCV to 0b0100 otherwise.
*/
asm volatile(
__mrs_s("%0", SYS_RNDR_EL0) "\n"
" cset %w1, ne\n"
: "=r" (*v), "=r" (ok)
:
: "cc");
return ok;
}
static inline bool __must_check arch_get_random_long(unsigned long *v)
{
return false;
}
static inline bool __must_check arch_get_random_int(unsigned int *v)
{
return false;
}
static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
{
/*
* Only support the generic interface after we have detected
* the system wide capability, avoiding complexity with the
* cpufeature code and with potential scheduling between CPUs
* with and without the feature.
*/
if (!cpus_have_const_cap(ARM64_HAS_RNG))
return false;
return __arm64_rndr(v);
}
static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
{
unsigned long val;
bool ok = arch_get_random_seed_long(&val);
*v = val;
return ok;
}
static inline bool __init __early_cpu_has_rndr(void)
{
/* Open code as we run prior to the first call to cpufeature. */
unsigned long ftr = read_sysreg_s(SYS_ID_AA64ISAR0_EL1);
return (ftr >> ID_AA64ISAR0_RNDR_SHIFT) & 0xf;
}
static inline bool __init __must_check
arch_get_random_seed_long_early(unsigned long *v)
{
WARN_ON(system_state != SYSTEM_BOOTING);
if (!__early_cpu_has_rndr())
return false;
return __arm64_rndr(v);
}
#define arch_get_random_seed_long_early arch_get_random_seed_long_early
#endif /* CONFIG_ARCH_RANDOM */
#endif /* _ASM_ARCHRANDOM_H */
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