linux-kernel - [PATCH 3.16 115/136] x86/decoder: Add new TEST instruction pattern

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Message-ID: <lsq.1518323471.893461445@decadent.org.uk>
Date:   Sun, 11 Feb 2018 04:31:11 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "kbuild test robot" <fengguang.wu@...el.com>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Ingo Molnar" <mingo@...nel.org>,
        "Masami Hiramatsu" <mhiramat@...nel.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Peter Zijlstra" <peterz@...radead.org>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH 3.16 115/136] x86/decoder: Add new TEST instruction pattern

3.16.54-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Masami Hiramatsu <mhiramat@...nel.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@...el.com>
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Ben Hutchings <ben@...adent.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
@@ -814,7 +814,7 @@ EndTable
 
 GrpTable: Grp3_1
 0: TEST Eb,Ib
-1:
+1: TEST Eb,Ib
 2: NOT Eb
 3: NEG Eb
 4: MUL AL,Eb