[PATCH] x86/Intel: don't accept bogus instructions

[H.J. Lu]

On Thu, Jun 30, 2016 at 4:58 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>> On 30.06.16 at 13:50, <hjl.tools@gmail.com> wrote:
>> On Thu, Jun 30, 2016 at 4:38 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>>>> On 30.06.16 at 13:18, <hjl.tools@gmail.com> wrote:
>>>> On Thu, Jun 30, 2016 at 3:34 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>>> ... due to their last byte looking like a suffix, when after its
>>>>> stripping a matching instruction can be found. Since memory operand
>>>>> size specifiers in Intel mode get converted into suffix representation
>>>>> internally, we need to keep track of the actual mnemonic suffix which
>>>>> may have got trimmed off, and check its validity while looking for a
>>>>> matching template. I tripper over this quite some time again after
>>>>> support for AMD's SSE5 instructions got removed, as at that point some
>>>>> of the SSE5 mnemonics, other than expected, didn't fail to assemble.
>>>>> But the problem affects many more instructions, namely (almost) all
>>>>> MMX, SSE, and AVX ones as it looks. I don't think it makes sense to
>>>>> add a testcase covering all of them, nor do I think it makes sense to
>>>>> pick out some random examples for a new test case.
>>>>
>>>> Please open a bug report to show there is a problem.
>>>
>>> I don't see the point, but anyway: 20318.
>>
>> Please add this testcase:
>>
>> .text
>> phadddb %xmm0, %xmm1
>> phadddd %xmm0, %xmm1
>> phadddl %xmm0, %xmm1
>> phadddld %xmm0, %xmm1
>> phadddq %xmm0, %xmm1
>> phaddds %xmm0, %xmm1
>> phadddw %xmm0, %xmm1
>> .intel_syntax noprefix
>> phadddb xmm0, xmm1
>> phadddd xmm0, xmm1
>> phadddl xmm0, xmm1
>> phadddld xmm0, xmm1
>> phadddq xmm0, xmm1
>> phaddds xmm0, xmm1
>> phadddw xmm0, xmm1
>>
>> to your patch and run it with both --32 and --64.  All of them should fail.
>
> To quote the original submission: "I don't think it makes sense to add
> a testcase covering all of them, nor do I think it makes sense to pick
> out some random examples for a new test case."
>
> What good does such a limited test case do? If anything, someone
> should sit down and write a script to machine generate a list of all
> mnemonics with invalid suffixes.
>

Without a testcase, your change looks like random change to me.
For all I know, you change doesn't make those instructions error.

-- 
H.J.