Re: [PATCH] Gerd Hoffman's move-vsyscall-into-user-address-range patch

[Andi Kleen <ak@suse.de>]

On Saturday 20 May 2006 03:11, Andrew Morton wrote:
> Ingo Molnar <mingo@elte.hu> wrote:
> >
> > 
> > * Andrew Morton <akpm@osdl.org> wrote:
> > 
> > > Rusty Russell <rusty@rustcorp.com.au> wrote:
> > > >
> > > > Name: Move vsyscall page out of fixmap into normal vma as per mmap
> > > 
> > > This causes mysterious hangs when starting init.
> > > 
> > > Distro is RH FC1, running SysVinit-2.85-5.
> > > 
> > > dmesg, sysrq-T and .config are at
> > > http://www.zip.com.au/~akpm/linux/patches/stuff/log-vmm - nothing leaps
> > > out.
> > > 
> > > This is the second time recently when a patch has caused this machine 
> > > to oddly hang in init.  It's possible that there's a bug of some form 
> > > in that version of init that we'll need to know about and take care of 
> > > in some fashion.
> > 
> > FC1 is like really ancient. I think there was a glibc bug that caused 
> > vsyscall related init hangs like that. To nevertheless let people run 
> > their old stuff there's a vdso=0 boot option in exec-shield.
> > 
> 
> Well that patch took a machine from working to non-working.  Pretty serious
> stuff.  We should get to the bottom of the problem so we can assess the
> risk and impact, no?

Just changing the address of the vsyscall page shouldn't break anything. The 
x86-64 32bit emulation has it at a different address than native i386 and 
afaik nothing broke because of that.

-Andi