Re: Why disable vdso by default with CONFIG_PARAVIRT?

[Rusty Russell <rusty@rustcorp.com.au>]

On Tue, 2006-12-12 at 04:02 +0100, Andi Kleen wrote:
> On Tuesday 12 December 2006 02:22, Jeremy Fitzhardinge wrote:
> > What problem do they cause together?  There's certainly no problem with
> > Xen+vdso
> 
> This was the change which finally got my test system (with an older
> SUSE 9.0 based user land to boot).  With paravirt older glibc's ld.so 
> otherwise throws assertation failures because it somehow can't deal with 
> the new placement. This only happens with paravirt enabled.
> 
> Binary compatibility is important.

Yes, this goes back to the original COMPAT_VDSO config option, months
ago.  FC1's buggy glibc couldn't handle the vdso being in an unusual
place, and (over my objections) the COMPAT_VDSO option was introduced.
Seems like SuSE 9.0 is similarly effected.

I don't have a system which has this problem (and, at the end of a
modem, I'm unlikely to get one soon).  But I would suggest that
COMPAT_VDSO should be rewritten: catch the segv from init (presumably in
around the old vdso 0xFFFF0000 addr?), printk a message, turn vdso off
and re-exec init.

That should make everyone happy.  Now, someone who can repro this please
code it up!

Thanks!
Rusty.