text: /* SPDX-License-Identifier: GPL-2.0 */
  #ifndef _ASM_ARCHRANDOM_H
  #define _ASM_ARCHRANDOM_H
  
  #ifdef CONFIG_ARCH_RANDOM
  
  #include <linux/arm-smccc.h>
  #include <linux/bug.h>
  #include <linux/kernel.h>
  #include <asm/cpufeature.h>
  
  #define ARM_SMCCC_TRNG_MIN_VERSION	0x10000UL
  
  extern bool smccc_trng_available;
  
  static inline bool __init smccc_probe_trng(void)
  {
  	struct arm_smccc_res res;
  
  	arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_VERSION, &res);
  	if ((s32)res.a0 < 0)
  		return false;
  
  	return res.a0 >= ARM_SMCCC_TRNG_MIN_VERSION;
  }
  
  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 __arm64_rndrrs(unsigned long *v)
  {
  	bool ok;
  
  	/*
  	 * Reads of RNDRRS set PSTATE.NZCV to 0b0000 on success,
  	 * and set PSTATE.NZCV to 0b0100 otherwise.
  	 */
  	asm volatile(
  		__mrs_s("%0", SYS_RNDRRS_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)
  {
  	/*
  	 * 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) && __arm64_rndr(v))
  		return true;
  	return false;
  }
  
  static inline bool __must_check arch_get_random_int(unsigned int *v)
  {
  	if (cpus_have_const_cap(ARM64_HAS_RNG)) {
  		unsigned long val;
  
  		if (__arm64_rndr(&val)) {
  			*v = val;
  			return true;
  		}
  	}
  	return false;
  }
  
  static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
  {
  	struct arm_smccc_res res;
  
  	/*
  	 * We prefer the SMCCC call, since its semantics (return actual
  	 * hardware backed entropy) is closer to the idea behind this
  	 * function here than what even the RNDRSS register provides
  	 * (the output of a pseudo RNG freshly seeded by a TRNG).
  	 */
  	if (smccc_trng_available) {
  		arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 64, &res);
  		if ((int)res.a0 >= 0) {
  			*v = res.a3;
  			return true;
  		}
  	}
  
  	/*
  	 * RNDRRS is not backed by an entropy source but by a DRBG that is
  	 * reseeded after each invocation. This is not a 100% fit but good
  	 * enough to implement this API if no other entropy source exists.
  	 */
  	if (cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndrrs(v))
  		return true;
  
  	return false;
  }
  
  static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
  {
  	struct arm_smccc_res res;
  	unsigned long val;
  
  	if (smccc_trng_available) {
  		arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 32, &res);
  		if ((int)res.a0 >= 0) {
  			*v = res.a3 & GENMASK(31, 0);
  			return true;
  		}
  	}
  
  	if (cpus_have_const_cap(ARM64_HAS_RNG)) {
  		if (__arm64_rndrrs(&val)) {
  			*v = val;
  			return true;
  		}
  	}
  
  	return false;
  }
  
  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 (smccc_trng_available) {
  		struct arm_smccc_res res;
  
  		arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 64, &res);
  		if ((int)res.a0 >= 0) {
  			*v = res.a3;
  			return true;
  		}
  	}
  
  	if (__early_cpu_has_rndr() && __arm64_rndr(v))
  		return true;
  
  	return false;
  }
  #define arch_get_random_seed_long_early arch_get_random_seed_long_early
  
  #else /* !CONFIG_ARCH_RANDOM */
  
  static inline bool __init smccc_probe_trng(void)
  {
  	return false;
  }
  
  #endif /* CONFIG_ARCH_RANDOM */
  #endif /* _ASM_ARCHRANDOM_H */
  