[PATCH 3.2 60/79] x86/decoder: Add new TEST instruction pattern

Ben Hutchings
2018-02-11T04:33:46Z

From: Masami Hiramatsu <mhiramat@kernel.org>

commit 12a78d43de767eaf8fb272facb7a7b6f2dc6a9df upstream.

The kbuild test robot reported this build warning:

Warning: arch/x86/tools/test_get_len found difference at <jump_table>:ffffffff8103dd2c

Warning: ffffffff8103dd82: f6 09 d8 testb $0xd8,(%rcx)
Warning: objdump says 3 bytes, but insn_get_length() says 2
Warning: decoded and checked 1569014 instructions with 1 warnings

This sequence seems to be a new instruction not in the opcode map in the Intel SDM.

The instruction sequence is "F6 09 d8", means Group3(F6), MOD(00)REG(001)RM(001), and 0xd8.
Intel SDM vol2 A.4 Table A-6 said the table index in the group is "Encoding of Bits 5,4,3 of
the ModR/M Byte (bits 2,1,0 in parenthesis)"

In that table, opcodes listed by the index REG bits as:

000 001 010 011 100 101 110 111
TEST Ib/Iz,(undefined),NOT,NEG,MUL AL/rAX,IMUL AL/rAX,DIV AL/rAX,IDIV AL/rAX

So, it seems TEST Ib is assigned to 001.

Add the new pattern.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/x86/lib/x86-opcode-map.txt | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/lib/x86-opcode-map.txt
+++ b/arch/x86/lib/x86-opcode-map.txt
@@ -759,7 +759,7 @@ EndTable

GrpTable: Grp3_1
0: TEST Eb,Ib
-1:
+1: TEST Eb,Ib
2: NOT Eb
3: NEG Eb
4: MUL AL,Eb