Re: [PATCH] linux-2.5.43_vsyscall_A0

Jeff Dike
2002-10-19T22:33:34Z

andrea@suse.de said:
> the sysctl would replace the vsyscall fixmap fixmap entry for the
> current cpu enterely at switch_to time, I certainly don't want to add
> not necessary branches in the core vsyscall code. Doing it globally
> is zerocost but it would probably need privilegies as said, per-task
> could be more dynamic without privilegies and it would be an unlikely
> branch added in switch_to, still a very low cost so still acceptable.

If I'm understanding this (and reading the code) correctly, this would
allow UML to specify that, for a given process, it should have a page of
its choosing mapped into the vsyscall area. Correct?

If so, I can go along with this. It makes vsyscalls virtualizable, and thus
available to UML, which needs them more than the other arches :-)

The one suggestion I'd make is to make it per-mm rather than per-task and
put it in switch_mm rather than switch_to.

Jeff