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-rw-r--r--arch/arm64/include/asm/archrandom.h75
1 files changed, 75 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/archrandom.h b/arch/arm64/include/asm/archrandom.h
new file mode 100644
index 000000000000..3fe02da70004
--- /dev/null
+++ b/arch/arm64/include/asm/archrandom.h
@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ARCHRANDOM_H
+#define _ASM_ARCHRANDOM_H
+
+#ifdef CONFIG_ARCH_RANDOM
+
+#include <linux/random.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;
+}
+
+#else
+
+static inline bool __arm64_rndr(unsigned long *v) { return false; }
+static inline bool __init __early_cpu_has_rndr(void) { return false; }
+
+#endif /* CONFIG_ARCH_RANDOM */
+#endif /* _ASM_ARCHRANDOM_H */