[Xen-devel] [PATCH v5 01/47] x86emul: introduce IMPOSSIBLE()

["Jan Beulich" <JBeulich@xxxxxxxx>]

This abstracts away the debug/release coverage using both
ASSERT_UNREACHABLE() and a return value of X86EMUL_UNHANDLEABLE.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v5: New.

--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -1017,6 +1017,15 @@ do {
     if ( rc ) goto done;                                \
 } while (0)
 
+#define IMPOSSIBLE(p)                                   \
+do {                                                    \
+    if ( unlikely(p) )                                  \
+    {                                                   \
+        ASSERT_UNREACHABLE();                           \
+        goto unhandleable;                              \
+    }                                                   \
+} while (0)
+
 static inline int mkec(uint8_t e, int32_t ec, ...)
 {
     return (e < 32 && ((1u << e) & EXC_HAS_EC)) ? ec : X86_EVENT_NO_EC;
@@ -8828,12 +8837,7 @@ x86_emulate(
                 dst.type = OP_NONE;
                 break;
             default:
-                if ( (d & DstMask) != DstMem )
-                {
-                    ASSERT_UNREACHABLE();
-                    rc = X86EMUL_UNHANDLEABLE;
-                    goto done;
-                }
+                IMPOSSIBLE((d & DstMask) != DstMem);
                 break;
             }
             if ( (d & DstMask) == DstMem )
@@ -8960,9 +8964,11 @@ x86_emulate(
             stub.func);
     generate_exception_if(stub_exn.info.fields.trapnr == EXC_UD, EXC_UD);
     domain_crash(current->domain);
+#endif
+
+ unhandleable:
     rc = X86EMUL_UNHANDLEABLE;
     goto done;
-#endif
 }
 
 #undef op_bytes





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