Messages in this thread | | | Date | Wed, 9 Jul 2008 13:14:05 -0700 | From | Arjan van de Ven <> | Subject | Re: [RFC 00/15] x86_64: Optimize percpu accesses |
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On Wed, 09 Jul 2008 13:00:19 -0700 ebiederm@xmission.com (Eric W. Biederman) wrote:
> > I just took a quick look at how stack_protector works on x86_64. > Unless there is some deep kernel magic that changes the segment > register to %gs from the ABI specified %fs CC_STACKPROTECTOR is > totally broken on x86_64. We access our pda through %gs.
and so does gcc in kernel mode.
> > Further -fstack-protector-all only seems to detect against buffer > overflows and thus corruption of the stack. Not stack overflows. So > it doesn't appear especially useful.
stopping buffer overflows and other return address corruption is not useful? Excuse me?
> > So we don't we kill the broken CONFIG_CC_STACKPROTECTOR. Stop trying > to figure out how to use a zero based percpu area.
So why don't we NOT do that and fix instead what you're trying to do?
> > That should allow us to make the current pda a per cpu variable, and > use %gs with a large offset to access the per cpu area.
and what does that gain us?
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