Re: linux-next: Tree for Oct 14 (insn_decoder_test)

[Randy Dunlap]

[adding x86 people]

I am still seeing this insn_decoder warning in linux-next.

Can we get this patch applied, please?

Masami, you might need to resend it...

thanks.


On 11/27/19 4:04 PM, Randy Dunlap wrote:
> On 10/22/19 10:49 PM, Masami Hiramatsu wrote:
>> Hi,
>>
>> On Mon, 14 Oct 2019 08:30:02 -0700
>> Randy Dunlap <rdunlap@xxxxxxxxxxxxx> wrote:
>>
>>> On 10/13/19 11:47 PM, Stephen Rothwell wrote:
>>>> Hi all,
>>>>
>>>> Changes since 20191011:
>>>>
>>>
>>> on x86_64:
>>>
>>>   HOSTCC  arch/x86/tools/insn_decoder_test
>>>   HOSTCC  arch/x86/tools/insn_sanity
>>>   TEST    posttest
>>> arch/x86/tools/insn_decoder_test: warning: Found an x86 instruction decoder bug, please report this.
>>> arch/x86/tools/insn_decoder_test: warning: ffffffff81000bf1:	f7 0b 00 01 08 00    	testl  $0x80100,(%rbx)
>>> arch/x86/tools/insn_decoder_test: warning: objdump says 6 bytes, but insn_get_length() says 2
>>> arch/x86/tools/insn_decoder_test: warning: Decoded and checked 11913894 instructions with 1 failures
>>>   TEST    posttest
>>> arch/x86/tools/insn_sanity: Success: decoded and checked 1000000 random instructions with 0 errors (seed:0x871ce29c)
>>
>> Hmm, curious.
>>
>> x86-opcode-map.txt said,
>> f7: Grp3_2 Ev (1A)
>>
>> and "0x0b" is 00001011b, Group encoding bits are 5,4,3 (reg field),
>> so group index is 001.
>>
>> GrpTable: Grp3_2
>> 0: TEST Ev,Iz
>> 1:
>>
>> Hmm, "f7 0b" is not assigned to any instruction... (testl should be f7 03)
>>
>> I've checked Intel SDM May 2019 version(*), but the Opcode Map (Table A-6. Opecode
>> Extensions for One- and Two-byte Opecodes by Group Number) showed the group index
>> 001 is still blank. I've also checked that Table B-13 (General Purpose Instruction
>>  Formats and Encodings for Non-64-Bit Modes (Note that this has no REX prefix)) but
>> I couldn't find "f7 0b".
>>
>> At last, I found that on AMD64 Architecture Programmer's Manual Volume 3, Appendix A.2
>> Table A-6. ModRM.reg Extensions for the Primary Opcode Map(**), which shows that both
>> f7 + reg=000 and f7 + reg=001 are same. So only on AMD64, it is officially available
>> instruction.
>>
>> (*) https://software.intel.com/sites/default/files/managed/a4/60/325383-sdm-vol-2abcd.pdf
>> (**) https://www.amd.com/system/files/TechDocs/24594.pdf
>>
>> OK, so this should be fixed with below patch.
>>
>> ------
>> >From b3f45b86df25be59fcf417730ab4c69c6310eaad Mon Sep 17 00:00:00 2001
>> From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
>> Date: Wed, 23 Oct 2019 14:45:35 +0900
>> Subject: [PATCH] x86/decoder: Add TEST opcode to Group3-2
>>
>> Add TEST opcode to Group3-2 reg=001b as same as Group3-1 does.
>>
>> Commit 12a78d43de76 ("x86/decoder: Add new TEST instruction pattern")
>> added a TEST opcode assignment to f6 XX/001/XXX (Group 3-1), but not
>> added f7 XX/001/XXX (Group 3-2). Actually these TEST opcode is not
>> described in Intel SDM Vol2, but described in AMD64 Architecture
>> Programmer's Manual Vol.3, Appendix A.2 Table A-6. ModRM.reg
>> Extensions for the Primary Opcode Map.
>>
>> Without this fix, Randy found a warning by insn_decoder_test related
>> to this issue as below.
>>
>>   HOSTCC  arch/x86/tools/insn_decoder_test
>>   HOSTCC  arch/x86/tools/insn_sanity
>>   TEST    posttest
>> arch/x86/tools/insn_decoder_test: warning: Found an x86 instruction decoder bug, please report this.
>> arch/x86/tools/insn_decoder_test: warning: ffffffff81000bf1:	f7 0b 00 01 08 00    	testl  $0x80100,(%rbx)
>> arch/x86/tools/insn_decoder_test: warning: objdump says 6 bytes, but insn_get_length() says 2
>> arch/x86/tools/insn_decoder_test: warning: Decoded and checked 11913894 instructions with 1 failures
>>   TEST    posttest
>> arch/x86/tools/insn_sanity: Success: decoded and checked 1000000 random instructions with 0 errors (seed:0x871ce29c)
>>
>> To fix this error, add TEST opcode according to AMD64 APM Vol.3.
>>
>> Reported-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
>> Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> 
> Acked-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> Tested-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> 
> Thanks.
> 
>> ---
>>  arch/x86/lib/x86-opcode-map.txt       | 2 +-
>>  tools/arch/x86/lib/x86-opcode-map.txt | 2 +-
>>  2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/lib/x86-opcode-map.txt b/arch/x86/lib/x86-opcode-map.txt
>> index e0b85930dd77..4635ce298d1d 100644
>> --- a/arch/x86/lib/x86-opcode-map.txt
>> +++ b/arch/x86/lib/x86-opcode-map.txt
>> @@ -907,7 +907,7 @@ EndTable
>>  
>>  GrpTable: Grp3_2
>>  0: TEST Ev,Iz
>> -1:
>> +1: TEST Ev,Iz
>>  2: NOT Ev
>>  3: NEG Ev
>>  4: MUL rAX,Ev
>> diff --git a/tools/arch/x86/lib/x86-opcode-map.txt b/tools/arch/x86/lib/x86-opcode-map.txt
>> index e0b85930dd77..4635ce298d1d 100644
>> --- a/tools/arch/x86/lib/x86-opcode-map.txt
>> +++ b/tools/arch/x86/lib/x86-opcode-map.txt
>> @@ -907,7 +907,7 @@ EndTable
>>  
>>  GrpTable: Grp3_2
>>  0: TEST Ev,Iz
>> -1:
>> +1: TEST Ev,Iz
>>  2: NOT Ev
>>  3: NEG Ev
>>  4: MUL rAX,Ev
>>
> 
> 


-- 
~Randy
Reported-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>