Re: [RFC][PATCH] objtool: STAC/CLAC validation

[hpa]

On February 23, 2019 12:39:42 AM PST, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>On Fri, Feb 22, 2019 at 03:39:48PM -0800, hpa@xxxxxxxxx wrote:
>> Objtool could also detect CLAC-STAC or STAC-CLAC sequences without
>> memory operations and remove them; don't know how often that happens,
>> but I know it *does* happen.
>
>Objtool doesn't know about memops; that'd be a lot of work. Also,
>objtool doesn't actually rewrite the text, at best it could warn about
>such occurences.

It doesn't have to understand the contents of the memop, but it seems that the presence of a modrm with mode â 3 should be plenty. It needs to know that much in order to know the length of instructions anyway. For extra credit, ignore LEA or hinting instructions.
-- 
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