Re: [PATCH v4 08/17] x86/entry: Add enter_from_user_mode and use it in syscalls

Borislav Petkov
2015-07-01T10:24:39Z

On Mon, Jun 29, 2015 at 12:33:40PM -0700, Andy Lutomirski wrote:
> Changing the x86 context tracking hooks is dangerous because there
> are no good checks that we track our context correctly. Add a
> helper to check that we're actually in CONTEXT_USER when we enter
> from user mode and wire it up for syscall entries.
>
> Subsequent patches will wire this up for all non-NMI entries as
> well. NMIs are their own special beast and cannot currently switch
> overall context tracking state. Instead, they have their own
> special RCU hooks.
>
> This is a tiny speedup if !CONFIG_CONTEXT_TRACKING (removes a
> branch) and a tiny slowdown if CONFIG_CONTEXT_TRACING (adds a layer

CONTEXT_TRACING?!

Oh noooo, not another tracer :-P

--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.
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