[Xen-devel] [PATCH 3/4] x86emul: drop SrcInvalid

["Jan Beulich" <JBeulich@xxxxxxxx>]

As of commit a800e4f611 ("x86emul: drop pointless and add useful
default cases") we no longer need the early bailing when "d == 0" (the
default cases in the main switch() statements take care of that),
removal of which renders internal_error() wrong and SrcInvalid useless.
Drop them, as they're going to get in the way of completing the decoder
to cover all known insns (to allow it to be used by more callers)
without at the same time completing the actual emulation logic.

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

--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -31,15 +31,14 @@
 #define DstMem      (3<<1) /* Memory operand. */
 #define DstMask     (3<<1)
 /* Source operand type. */
-#define SrcInvalid  (0<<3) /* Unimplemented opcode. */
-#define SrcNone     (1<<3) /* No source operand. */
-#define SrcImplicit (1<<3) /* Source operand is implicit in the opcode. */
-#define SrcReg      (2<<3) /* Register operand. */
-#define SrcMem      (3<<3) /* Memory operand. */
-#define SrcMem16    (4<<3) /* Memory operand (16-bit). */
-#define SrcImm      (5<<3) /* Immediate operand. */
-#define SrcImmByte  (6<<3) /* 8-bit sign-extended immediate operand. */
-#define SrcImm16    (7<<3) /* 16-bit zero-extended immediate operand. */
+#define SrcNone     (0<<3) /* No source operand. */
+#define SrcImplicit (0<<3) /* Source operand is implicit in the opcode. */
+#define SrcReg      (1<<3) /* Register operand. */
+#define SrcMem      (2<<3) /* Memory operand. */
+#define SrcMem16    (3<<3) /* Memory operand (16-bit). */
+#define SrcImm      (4<<3) /* Immediate operand. */
+#define SrcImmByte  (5<<3) /* 8-bit sign-extended immediate operand. */
+#define SrcImm16    (6<<3) /* 16-bit zero-extended immediate operand. */
 #define SrcMask     (7<<3)
 /* Generic ModRM decode. */
 #define ModRM       (1<<6)
@@ -1532,19 +1531,6 @@ int x86emul_unhandleable_rw(
     return X86EMUL_UNHANDLEABLE;
 }
 
-static void internal_error(const char *which, uint8_t byte,
-                           const struct cpu_user_regs *regs)
-{
-#ifdef __XEN__
-    static bool_t logged;
-
-    if ( !test_and_set_bool(logged) )
-        gprintk(XENLOG_ERR, "Internal error: %s/%02x [%04x:%08lx]\n",
-                which, byte, regs->cs, regs->eip);
-#endif
-    ASSERT_UNREACHABLE();
-}
-
 int
 x86_emulate(
     struct x86_emulate_ctxt *ctxt,
@@ -1664,10 +1650,6 @@ x86_emulate(
                 break;
             }
         }
-
-        /* Unrecognised? */
-        if ( d == 0 )
-            goto cannot_emulate;
     }
 
     /* Lock prefix is allowed only on RMW instructions. */
@@ -1729,10 +1711,6 @@ x86_emulate(
                 b = insn_fetch_type(uint8_t);
                 d = twobyte_table[b];
 
-                /* Unrecognised? */
-                if ( d == 0 || b == 0x38 )
-                    goto cannot_emulate;
-
                 modrm = insn_fetch_type(uint8_t);
                 modrm_mod = (modrm & 0xc0) >> 6;
 
@@ -3851,7 +3829,6 @@ x86_emulate(
         break;
 
     default:
-        internal_error("primary", b, ctxt->regs);
         goto cannot_emulate;
     }
 
@@ -4837,7 +4814,6 @@ x86_emulate(
         break;
 
     default:
-        internal_error("secondary", b, ctxt->regs);
         goto cannot_emulate;
     }
     goto writeback;

Attachment: x86emul-drop-SrcInvalid.patch
Description: Text document

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