[llvm-exegesis][AArch64] Disable pauth and ldgm as unsupported instructions fixed

llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp

@@ -9,6 +9,14 @@
 #include "AArch64.h"
 #include "AArch64RegisterInfo.h"
 
+#if defined(__aarch64__) && defined(__linux__)
+#include <linux/prctl.h> // For PR_PAC_* constants
+#include <sys/prctl.h>
+#ifndef PR_PAC_SET_ENABLED_KEYS
+#define PR_PAC_SET_ENABLED_KEYS 60
+#endif
+#endif
+
 #define GET_AVAILABLE_OPCODE_CHECKER
 #include "AArch64GenInstrInfo.inc"
 
@@ -134,6 +142,35 @@ class ExegesisAArch64Target : public ExegesisTarget {
     // Function return is a pseudo-instruction that needs to be expanded
     PM.add(createAArch64ExpandPseudoPass());
   }
+
+  const char *getIgnoredOpcodeReasonOrNull(const LLVMState &State,
+                                           unsigned Opcode) const override {
+    if (const char *Reason =
+            ExegesisTarget::getIgnoredOpcodeReasonOrNull(State, Opcode))
+      return Reason;
+
+    if (isPointerAuth(Opcode)) {
+#if defined(__aarch64__) && defined(__linux__)
+      // Disable all PAC keys. Note that while we expect the measurements to
+      // be the same with PAC keys disabled, they could potentially be lower
+      // since authentication checks are bypassed.
+      if (prctl(PR_PAC_SET_ENABLED_KEYS,
+                PR_PAC_APIAKEY | PR_PAC_APIBKEY | PR_PAC_APDAKEY |
+                    PR_PAC_APDBKEY, // all keys
+                0,                  // disable all
+                0, 0) < 0) {
+        return "Failed to disable PAC keys";
+      }
+#else
+      return "Unsupported opcode: isPointerAuth";
+#endif
+    }
+
+    if (isLoadTagMultiple(Opcode))
+      return "Unsupported opcode: load tag multiple";
+
+    return nullptr;
+  }
 };
 
 } // namespace