target/arm: Implement ARMv8.5-RNG

Use the newly introduced infrastructure for guest random numbers.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 44 insertions, 0 deletions

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 6b91082b8b..acd23c53ca 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -22,6 +22,8 @@
 #include "fpu/softfloat.h"
 #include "qemu/range.h"
 #include "qapi/qapi-commands-target.h"
+#include "qapi/error.h"
+#include "qemu/guest-random.h"
 
 #define ARM_CPU_FREQ 1000000000 /* FIXME: 1 GHz, should be configurable */
 
@@ -5746,6 +5748,45 @@ static const ARMCPRegInfo pauth_reginfo[] = {
       .fieldoffset = offsetof(CPUARMState, keys.apib.hi) },
     REGINFO_SENTINEL
 };
+
+static uint64_t rndr_readfn(CPUARMState *env, const ARMCPRegInfo *ri)
+{
+    Error *err = NULL;
+    uint64_t ret;
+
+    /* Success sets NZCV = 0000.  */
+    env->NF = env->CF = env->VF = 0, env->ZF = 1;
+
+    if (qemu_guest_getrandom(&ret, sizeof(ret), &err) < 0) {
+        /*
+         * ??? Failed, for unknown reasons in the crypto subsystem.
+         * The best we can do is log the reason and return the
+         * timed-out indication to the guest.  There is no reason
+         * we know to expect this failure to be transitory, so the
+         * guest may well hang retrying the operation.
+         */
+        qemu_log_mask(LOG_UNIMP, "%s: Crypto failure: %s",
+                      ri->name, error_get_pretty(err));
+        error_free(err);
+
+        env->ZF = 0; /* NZCF = 0100 */
+        return 0;
+    }
+    return ret;
+}
+
+/* We do not support re-seeding, so the two registers operate the same.  */
+static const ARMCPRegInfo rndr_reginfo[] = {
+    { .name = "RNDR", .state = ARM_CP_STATE_AA64,
+      .type = ARM_CP_NO_RAW | ARM_CP_SUPPRESS_TB_END | ARM_CP_IO,
+      .opc0 = 3, .opc1 = 3, .crn = 2, .crm = 4, .opc2 = 0,
+      .access = PL0_R, .readfn = rndr_readfn },
+    { .name = "RNDRRS", .state = ARM_CP_STATE_AA64,
+      .type = ARM_CP_NO_RAW | ARM_CP_SUPPRESS_TB_END | ARM_CP_IO,
+      .opc0 = 3, .opc1 = 3, .crn = 2, .crm = 4, .opc2 = 1,
+      .access = PL0_R, .readfn = rndr_readfn },
+    REGINFO_SENTINEL
+};
 #endif
 
 static CPAccessResult access_predinv(CPUARMState *env, const ARMCPRegInfo *ri,
@@ -6690,6 +6731,9 @@ void register_cp_regs_for_features(ARMCPU *cpu)
     if (cpu_isar_feature(aa64_pauth, cpu)) {
         define_arm_cp_regs(cpu, pauth_reginfo);
     }
+    if (cpu_isar_feature(aa64_rndr, cpu)) {
+        define_arm_cp_regs(cpu, rndr_reginfo);
+    }
 #endif
 
     /*