Re: Trampolines on x86

[christos%astron.com@localhost (Christos Zoulas)]

In article <20091031152656.GF23079%piccard.ngas.ch@localhost>,
Tonnerre Lombard  <tonnerre%netbsd.ch@localhost> wrote:
>-=-=-=-=-=-
>
>Salut,
>
>Lars and me encountered a number of problems with iret and trampolines
>on x86. Therefor, we wondered of what use trampolines still are on
>x86 (i386 and amd64) are these days. Considering the fact that we're
>using lazy mapping tricks, wouldn't the trampoline be more of a
>performance drain than the gain it originally intented?
>
>In order to solve the bug we're currently tracing, we would need to
>add special handling code to the iret operation which would make the
>regular trampoline code slower. In order to avoid hitting this in
>future NetBSD releases, we'd like to disable trampolines entirely.
>Compat code however would retain them (obviously) and run slower.
>
>Are there any thoughts or objections on this?

This could be done only for images that have executable stack, so it
should not affect regular binaries. And there is always objective c.

christos