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Re: ppc64 vDSO in mainline
- From: Steve Munroe <sjmunroe at us dot ibm dot com>
- To: Ulrich Drepper <drepper at redhat dot com>
- Cc: Alan Modra <amodra at bigpond dot net dot au>, Benjamin Herrenschmidt <benh at kernel dot crashing dot org>, libc-alpha at sources dot redhat dot com, Roland McGrath <roland at redhat dot com>
- Date: Thu, 24 Mar 2005 17:44:23 -0600
- Subject: Re: ppc64 vDSO in mainline
Ulrich Drepper <firstname.lastname@example.org> 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
> > 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