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Re: ppc64 vDSO in mainline


Ulrich Drepper <drepper@redhat.com> wrote on 03/24/2005 05:00:21 PM:

> Steve Munroe wrote:
> > I will work on the hackery for powerpc/gettimeofday, but I wanted to
> > start/restart the design discussion about generalized vdso binding and 
a
> > cross platform issues.
> 
> Any change to the vDSO is fine if (and this is a hard requirement) the
> changes do not make the vDSO position dependent.  We definitely need the
> vDSO address to be randomized.  It's OK for now to have a fixed address
> but fixing the vDSO text for every program start is not acceptable.
> This is how we arrived at the current model.
> 

Is this a hard requirement for all arches or just for i386? 

I can see how randomized VDSO for platforms using 
NEED_DL_SYSINFO/DL_SYSINFO_IMPLEMENTATION might prevent a virus attacker 
from using syscalls. But powerpc is a NEED_DL_SYSINFO_DSO only 
implemention and so can't prevent anyone from using syscalls inline. And I 
don't see how calling gettimeofday is a security threat?

I was not even thinking of a fixed absolute address in the ABI. 

Steven J. Munroe
Linux on Power Toolchain Architect
IBM Corporation, Linux Technology Center


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