linux-kernel - [PATCH 01/43] x86/decoder: Add new TEST instruction pattern

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Date:   Fri, 24 Nov 2017 10:14:06 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...capital.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 01/43] x86/decoder: Add new TEST instruction pattern

From: Masami Hiramatsu <mhiramat@...nel.org>

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.

Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Reported-by: kbuild test robot <fengguang.wu@...el.com>
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Cc: <stable@...r.kernel.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>
---
 arch/x86/lib/x86-opcode-map.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/lib/x86-opcode-map.txt b/arch/x86/lib/x86-opcode-map.txt
index 12e377184ee4..c4d55919fac1 100644
--- a/arch/x86/lib/x86-opcode-map.txt
+++ b/arch/x86/lib/x86-opcode-map.txt
@@ -896,7 +896,7 @@ EndTable
 
 GrpTable: Grp3_1
 0: TEST Eb,Ib
-1:
+1: TEST Eb,Ib
 2: NOT Eb
 3: NEG Eb
 4: MUL AL,Eb
-- 
2.14.1