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SubjectRe: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f
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On 02/07/2018 10:13 AM, Linus Torvalds wrote:
> Adding more people for this funky warning from the kbuild robot.
>
> Something is confused. UD0 is 0f ff, the bytes after that shouldn't
> matter. But I guess they can be interpreted as modrm bytes, and
> somebody started doing that.
>
> That said, intel only _documents_ UD2 (0f 0b).

Intel Order Number: 325383-064US, October 2017, documents UD0, UD1, and UD2.
Section A.2.5, Table A-1, says:

Use the 0F0B opcode (UD2 instruction), the 0FB9H opcode (UD1 instruction), or the 0FFFH opcode (UD0 instruction) when deliberately trying to generate an invalid opcode exception (#UD).

Could this regression be a result of:

commit f5b5fab1780c98b74526dbac527574bd02dc16f8
Author: Randy Dunlap <rdunlap@infradead.org>
Date: Mon Dec 11 10:38:36 2017 -0800

x86/decoder: Fix and update the opcodes map

Update x86-opcode-map.txt based on the October 2017 Intel SDM publication.
Fix INVPID to INVVPID.
Add UD0 and UD1 instruction opcodes.


> Maybe we should avoid using UD0/UD1 entirely.
>
> Linus
>
> On Wed, Feb 7, 2018 at 3:44 AM, kbuild test robot
> <fengguang.wu@intel.com> wrote:
>> tree/branch: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>> branch HEAD: a2e5790d841658485d642196dbb0927303d6c22f Merge branch 'akpm' (patches from Andrew)
>>
>> Regressions in current branch:
>>
>> arch/x86/tools/insn_decoder_test: warning: ffffffff810010d7: 0f ff eb ud0 %ebx,%ebp
>> arch/x86/tools/insn_decoder_test: warning: ffffffff81001152: 0f ff bf 09 00 00 00 ud0 0x9(%rdi),%edi
>> arch/x86/tools/insn_decoder_test: warning: ffffffff81001275: 0f ff eb ud0 %ebx,%ebp
>> arch/x86/tools/insn_decoder_test: warning: ffffffff810013fd: 0f ff bf 09 00 00 00 ud0 0x9(%rdi),%edi
>> arch/x86/tools/insn_decoder_test: warning: ffffffff81001499: 0f ff bf 09 00 00 00 ud0 0x9(%rdi),%edi
>> arch/x86/tools/insn_decoder_test: warning: ffffffff812296eb: 0f ff e8 ud0 %eax,%ebp


--
~Randy

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