Re: [kbuild-all] arch/x86/tools/insn_decoder_test: warning: ffffffff810005ac: 0f ff e9 ud0 %ecx, %ebp

[Masami Hiramatsu]

Hi,

On Fri, 9 Feb 2018 00:30:20 +0000
"Hao, Shun" <shun.hao@xxxxxxxxx> wrote:

> Thanks Masami, so that explains why a lot of these warnings come out just after 
> we upgrading to gcc-7.3 (now the objdump version is 2.30). 
> Currently we've already ignore these warnings and won't send this report. 

Anyway, it must be fixed with the below patch.

https://lkml.org/lkml/2018/2/8/350

(Sorry, I replyed to another warning mail)

Thank you,

> 
> >-----Original Message-----
> >From: kbuild-all [mailto:kbuild-all-bounces@xxxxxxxxxxxx] On Behalf Of Masami
> >Hiramatsu
> >Sent: Thursday, February 8, 2018 10:34 PM
> >To: Wu, Fengguang <fengguang.wu@xxxxxxxxx>
> >Cc: Ingo Molnar <mingo@xxxxxxxxxx>; kbuild-all@xxxxxx; linux-
> >kernel@xxxxxxxxxxxxxxx
> >Subject: Re: [kbuild-all] arch/x86/tools/insn_decoder_test: warning: ffffffff810005ac:
> >0f ff e9 ud0 %ecx, %ebp
> >
> >On Thu, 8 Feb 2018 06:04:45 +0800
> >kbuild test robot <fengguang.wu@xxxxxxxxx> wrote:
> >
> >> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> >> head:   7590e37bdaeec25ae325f4ba450be13e2aac6c8d
> >> commit: 10c91577d5e631773a6394e14cf60125389b71ae x86/tools: Standardize
> >output format of insn_decode_test
> >> date:   8 weeks ago
> >> config: x86_64-randconfig-s2-02072130 (attached as .config)
> >> compiler: gcc-6 (Debian 6.4.0-9) 6.4.0 20171026
> >> reproduce:
> >>         git checkout 10c91577d5e631773a6394e14cf60125389b71ae
> >>         # save the attached .config to linux build tree
> >>         make ARCH=x86_64
> >>
> >> All warnings (new ones prefixed by >>):
> >>
> >>    arch/x86/tools/insn_decoder_test: warning: Found an x86 instruction decoder bug,
> >please report this.
> >> >> arch/x86/tools/insn_decoder_test: warning: ffffffff810005ac:	0f ff e9
> >	ud0    %ecx,%ebp
> >
> >Does UD0 really take an operand? Hmm, indeed, the latest Intel SDM (December2017)
> >says
> >
> >NOTES:
> >1. Some older processors decode the UD0 instruction without a ModR/M byte. As a
> >result, those processors would deliver an invalid-
> >opcode exception instead of a fault on instruction fetch when the instruction with a
> >ModR/M byte (and any implied bytes) would
> >cross a page or segment boundary.
> >
> >and older SDM (e.g. March 2017) says UD0 has no modrm byte.
> >It is easy to change x86-opecode-map.txt, but this means this test may fail with older
> >objdump...
> >
> >>
> >> ---
> >> 0-DAY kernel test infrastructure                Open Source Technology Center
> >> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
> >
> >
> >--
> >Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> >_______________________________________________
> >kbuild-all mailing list
> >kbuild-all@xxxxxxxxxxxx
> >https://lists.01.org/mailman/listinfo/kbuild-all


-- 
Masami Hiramatsu <mhiramat@xxxxxxxxxx>