[Qemu-devel] [PATCH 04/17] target/arm: Fill in helper_mte_check

[Richard Henderson]

Implements the rules of "PE generation of Checked and
Unchecked accesses" which aren't already covered by XXX.
Implements the rules of "PE handling of Tag Check Failure".

Does not implement tag physical address space, so all
operations reduce to unchecked so far.

Signed-off-by: Richard Henderson <address@hidden>
---
 target/arm/mte_helper.c | 80 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 79 insertions(+), 1 deletion(-)

diff --git a/target/arm/mte_helper.c b/target/arm/mte_helper.c
index a3226c44a4..6f4bc0aa04 100644
--- a/target/arm/mte_helper.c
+++ b/target/arm/mte_helper.c
@@ -25,8 +25,86 @@
 #include "exec/helper-proto.h"
 
 
+static int get_allocation_tag(CPUARMState *env, uint64_t ptr)
+{
+    /* Tag storage not implemented.  */
+    return -1;
+}
+
+static int allocation_tag_from_addr(uint64_t ptr)
+{
+    return (extract64(ptr, 56, 4) + extract64(ptr, 55, 1)) & 15;
+}
+
 uint64_t HELPER(mte_check)(CPUARMState *env, uint64_t ptr)
 {
-    /* Only unchecked implemented so far.  */
+    ARMMMUIdx mmu_idx = arm_stage1_mmu_idx(env);
+    ARMVAParameters param = aa64_va_parameters(env, ptr, mmu_idx, true);
+    int ptr_tag, mem_tag;
+
+    /*
+     * If TBI is disabled, then the access is unchecked.
+     * While we filtered out TBI0==0 && TBI1==0 in cpu_get_tb_cpu_state,
+     * we did not save separate bits for TBI0 != TBI1.
+     */
+    if (!param.tbi) {
+        /* Do not ignore the top byte.  */
+        return ptr;
+    }
+
+    /*
+     * If TCMA is enabled, then physical tag 0 is unchecked.
+     * Note the rules R0076 & R0077 are written with logical tags,
+     * and we need the physical tag below anyway.
+     */
+    ptr_tag = allocation_tag_from_addr(ptr);
+    if (param.tcma && ptr_tag == 0) {
+        goto pass;
+    }
+
+    /*
+     * If an access is made to an address that does not provide tag storage,
+     * the result is implementation defined (R0006).  We choose to treat the
+     * access as unchecked.
+     * This is similar to MemAttr != Tagged, which are also unchecked.
+     */
+    mem_tag = get_allocation_tag(env, ptr);
+    if (mem_tag < 0) {
+        goto pass;
+    }
+
+    /* If the tags do not match, the tag check operation fails.  */
+    if (ptr_tag != mem_tag) {
+        int el = arm_current_el(env);
+        int tcf;
+
+        /* Indicate the tag check fail, both async and sync reporting.  */
+        env->cp15.tfsr_el[el] |= 1 << param.select;
+
+        if (el == 0) {
+            /* FIXME: ARMv8.1-VHE S2 translation regime.  */
+            tcf = extract64(env->cp15.sctlr_el[1], 38, 2);
+        } else {
+            tcf = extract64(env->cp15.sctlr_el[el], 40, 2);
+        }
+        if (tcf == 1) {
+            /* Tag check fail causes a synchronous exception.  */
+            CPUState *cs = ENV_GET_CPU(env);
+
+            /*
+             * In restore_state_to_opc, we set the exception syndrome
+             * for the load or store operation.  Do that first so we
+             * may overwrite that with the syndrome for the tag check.
+             */
+            cpu_restore_state(cs, GETPC(), true);
+            env->exception.vaddress = ptr;
+            raise_exception(env, EXCP_DATA_ABORT,
+                            syn_data_abort_no_iss(el != 0, 0, 0, 0, 0, 0x11),
+                            exception_target_el(env));
+        }
+    }
+
+ pass:
+    /* Unchecked, or tag check pass.  Ignore the top byte.  */
     return sextract64(ptr, 0, 55);
 }
-- 
2.17.2