Merge branch 'for-next/rng' into for-next/core

Add support for the TRNG firmware call introduced by Arm spec DEN0098.

* for-next/rng:
  arm64: Add support for SMCCC TRNG entropy source
  firmware: smccc: Introduce SMCCC TRNG framework
  firmware: smccc: Add SMCCC TRNG function call IDs

4 files changed, 119 insertions, 10 deletions

diff --git a/arch/arm/include/asm/archrandom.h b/arch/arm/include/asm/archrandom.h
new file mode 100644
index 000000000000..a8e84ca5c2ee
--- /dev/null
+++ b/arch/arm/include/asm/archrandom.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ARCHRANDOM_H
+#define _ASM_ARCHRANDOM_H
+
+static inline bool __init smccc_probe_trng(void)
+{
+	return false;
+}
+
+#endif /* _ASM_ARCHRANDOM_H */
diff --git a/arch/arm64/include/asm/archrandom.h b/arch/arm64/include/asm/archrandom.h
index ffb1a40d5475..09e43272ccb0 100644
--- a/arch/arm64/include/asm/archrandom.h
+++ b/arch/arm64/include/asm/archrandom.h
@@ -4,10 +4,26 @@
 
 #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;
@@ -38,26 +54,55 @@ static inline bool __must_check arch_get_random_int(unsigned int *v)
 
 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;
+		}
+	}
+
 	/*
 	 * 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;
+	if (cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndr(v))
+		return true;
 
-	return __arm64_rndr(v);
+	return false;
 }
 
-
 static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
 {
+	struct arm_smccc_res res;
 	unsigned long val;
-	bool ok = arch_get_random_seed_long(&val);
 
-	*v = val;
-	return ok;
+	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_rndr(&val)) {
+			*v = val;
+			return true;
+		}
+	}
+
+	return false;
 }
 
 static inline bool __init __early_cpu_has_rndr(void)
@@ -72,12 +117,29 @@ arch_get_random_seed_long_early(unsigned long *v)
 {
 	WARN_ON(system_state != SYSTEM_BOOTING);
 
-	if (!__early_cpu_has_rndr())
-		return false;
+	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 __arm64_rndr(v);
+	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 */
diff --git a/drivers/firmware/smccc/smccc.c b/drivers/firmware/smccc/smccc.c
index 00c88b809c0c..d52bfc5ed5e4 100644
--- a/drivers/firmware/smccc/smccc.c
+++ b/drivers/firmware/smccc/smccc.c
@@ -5,16 +5,22 @@
 
 #define pr_fmt(fmt) "smccc: " fmt
 
+#include <linux/cache.h>
 #include <linux/init.h>
 #include <linux/arm-smccc.h>
+#include <asm/archrandom.h>
 
 static u32 smccc_version = ARM_SMCCC_VERSION_1_0;
 static enum arm_smccc_conduit smccc_conduit = SMCCC_CONDUIT_NONE;
 
+bool __ro_after_init smccc_trng_available = false;
+
 void __init arm_smccc_version_init(u32 version, enum arm_smccc_conduit conduit)
 {
 	smccc_version = version;
 	smccc_conduit = conduit;
+
+	smccc_trng_available = smccc_probe_trng();
 }
 
 enum arm_smccc_conduit arm_smccc_1_1_get_conduit(void)
diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index f860645f6512..62c54234576c 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -102,6 +102,37 @@
 			   ARM_SMCCC_OWNER_STANDARD_HYP,	\
 			   0x21)
 
+/* TRNG entropy source calls (defined by ARM DEN0098) */
+#define ARM_SMCCC_TRNG_VERSION					\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
+			   ARM_SMCCC_SMC_32,			\
+			   ARM_SMCCC_OWNER_STANDARD,		\
+			   0x50)
+
+#define ARM_SMCCC_TRNG_FEATURES					\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
+			   ARM_SMCCC_SMC_32,			\
+			   ARM_SMCCC_OWNER_STANDARD,		\
+			   0x51)
+
+#define ARM_SMCCC_TRNG_GET_UUID					\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
+			   ARM_SMCCC_SMC_32,			\
+			   ARM_SMCCC_OWNER_STANDARD,		\
+			   0x52)
+
+#define ARM_SMCCC_TRNG_RND32					\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
+			   ARM_SMCCC_SMC_32,			\
+			   ARM_SMCCC_OWNER_STANDARD,		\
+			   0x53)
+
+#define ARM_SMCCC_TRNG_RND64					\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
+			   ARM_SMCCC_SMC_64,			\
+			   ARM_SMCCC_OWNER_STANDARD,		\
+			   0x53)
+
 /*
  * Return codes defined in ARM DEN 0070A
  * ARM DEN 0070A is now merged/consolidated into ARM DEN 0028 C