Messages in this thread | | | Date | Thu, 7 Mar 2019 18:06:29 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH v2 10/20] x86: avoid W^X being broken during modules loading |
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On Thu, Mar 07, 2019 at 08:53:34AM -0800, hpa@zytor.com wrote: > If we *do*, what is the issue here? Although boot_cpu_has() isn't > slow (it should in general be possible to reduce to one testb > instruction followed by a conditional jump) it seems that "avoiding an > alternatives slot" *should* be a *very* weak reason, and seems to me > to look like papering over some other problem.
Forget the current thread: this is simply trying to document when to use static_cpu_has() and when to use boot_cpu_has(). I get asked about it at least once a month.
And then it is replacing clear slow paths using static_cpu_has() with boot_cpu_has() because there's purely no need to patch there. And having a RIP-relative MOV and a JMP is good enough for slow paths.
Makes sense?
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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