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SubjectRe: [PATCH 1/4] glibc: Perform rseq(2) registration at C startup and thread creation (v7)
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* Michael Ellerman:

> I'm a bit vague on what we're trying to do here.
>
> But it seems like you want some sort of "eye catcher" prior to the branch?
>
> That value is a valid instruction on current CPUs (rlwimi.
> r5,r24,6,1,9), and even if it wasn't it could become one in future.
>
> If you change it to 0x8053530 that is both a valid instruction and is a
> nop (conditional trap immediate but with no conditions set).

I think we need something that is very unlikely to appear in the
instruction stream. It's just a marker. The instruction will never be
executed, and it does not have to be a trap, either (I believe that a
standard trap instruction would be a bad choice).

Thanks,
Florian

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