[llvm] r316282 - [X86] Don't allow gather/scatter to disassembler if memory operand does not use a SIB byte.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Sat Oct 21 21:32:30 2017
New Revision: 316282

URL: http://llvm.org/viewvc/llvm-project?rev=316282&view=rev
Log:
[X86] Don't allow gather/scatter to disassembler if memory operand does not use a SIB byte.

Fixes PR34998.

Added:
    llvm/trunk/test/MC/Disassembler/X86/gather-novsib.txt
Modified:
    llvm/trunk/lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp

Modified: llvm/trunk/lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp?rev=316282&r1=316281&r2=316282&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp (original)
+++ llvm/trunk/lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp Sat Oct 21 21:32:30 2017
@@ -1723,6 +1723,10 @@ static int readOperands(struct InternalI
       if (readModRM(insn))
         return -1;
 
+      // Reject if SIB wasn't used.
+      if (insn->eaBase != EA_BASE_sib && insn->eaBase != EA_BASE_sib64)
+        return -1;
+
       // If sibIndex was set to SIB_INDEX_NONE, index offset is 4.
       if (insn->sibIndex == SIB_INDEX_NONE)
         insn->sibIndex = (SIBIndex)4;

Added: llvm/trunk/test/MC/Disassembler/X86/gather-novsib.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/Disassembler/X86/gather-novsib.txt?rev=316282&view=auto
==============================================================================
--- llvm/trunk/test/MC/Disassembler/X86/gather-novsib.txt (added)
+++ llvm/trunk/test/MC/Disassembler/X86/gather-novsib.txt Sat Oct 21 21:32:30 2017
@@ -0,0 +1,4 @@
+# RUN: llvm-mc --disassemble %s -triple=x86_64-apple-darwin9 2>&1 | grep "invalid instruction encoding"
+
+// This corresponds to a gather, but doesn't use a SIB byte.
+0xc4,0xe2,0xe9,0x92,0x08