target/arm: Implement the IRG instruction

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200626033144.790098-10-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 72 insertions, 0 deletions

diff --git a/target/arm/mte_helper.c b/target/arm/mte_helper.c
new file mode 100644
index 0000000000..539a04de84
--- /dev/null
+++ b/target/arm/mte_helper.c
@@ -0,0 +1,72 @@
+/*
+ * ARM v8.5-MemTag Operations
+ *
+ * Copyright (c) 2020 Linaro, Ltd.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "cpu.h"
+#include "internals.h"
+#include "exec/exec-all.h"
+#include "exec/cpu_ldst.h"
+#include "exec/helper-proto.h"
+
+
+static int choose_nonexcluded_tag(int tag, int offset, uint16_t exclude)
+{
+    if (exclude == 0xffff) {
+        return 0;
+    }
+    if (offset == 0) {
+        while (exclude & (1 << tag)) {
+            tag = (tag + 1) & 15;
+        }
+    } else {
+        do {
+            do {
+                tag = (tag + 1) & 15;
+            } while (exclude & (1 << tag));
+        } while (--offset > 0);
+    }
+    return tag;
+}
+
+uint64_t HELPER(irg)(CPUARMState *env, uint64_t rn, uint64_t rm)
+{
+    int rtag;
+
+    /*
+     * Our IMPDEF choice for GCR_EL1.RRND==1 is to behave as if
+     * GCR_EL1.RRND==0, always producing deterministic results.
+     */
+    uint16_t exclude = extract32(rm | env->cp15.gcr_el1, 0, 16);
+    int start = extract32(env->cp15.rgsr_el1, 0, 4);
+    int seed = extract32(env->cp15.rgsr_el1, 8, 16);
+    int offset, i;
+
+    /* RandomTag */
+    for (i = offset = 0; i < 4; ++i) {
+        /* NextRandomTagBit */
+        int top = (extract32(seed, 5, 1) ^ extract32(seed, 3, 1) ^
+                   extract32(seed, 2, 1) ^ extract32(seed, 0, 1));
+        seed = (top << 15) | (seed >> 1);
+        offset |= top << i;
+    }
+    rtag = choose_nonexcluded_tag(start, offset, exclude);
+    env->cp15.rgsr_el1 = rtag | (seed << 8);
+
+    return address_with_allocation_tag(rn, rtag);
+}