Messages in this thread | | | Date | Wed, 28 Nov 2007 10:51:29 -0800 (PST) | From | Christoph Lameter <> | Subject | Re: [patch 05/14] percpu: Use a Kconfig variable to configure arch specific percpu setup |
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On Wed, 28 Nov 2007, Rusty Russell wrote:
> On Wednesday 28 November 2007 05:14:47 Christoph Lameter wrote: > > On Tue, 27 Nov 2007, Rusty Russell wrote: > > > Have you considered moving x86-64's setup_per_cpu_areas into generic > > > code? It's a bit messier because some archs might not have set up NUMA > > > stuff yet, but it's logically generic... > > > > Yes that will happen later. This is just the early cleanup work. I > > plan to generally bring the two x86 arches in line. The pda will be > > folded into the per cpu area and after that its easy to do. > > Unfortunately, we tried to get rid of the x86-64 pda (like i386) but you lose > the ability to use the stack protection config option. That's because it > assumes that gs:0x68 (or something) is the stack canary; we need a YA gcc > change to make this gs:__builtin_stack_canary_off (where gcc can emit > __builtin_stack_canary_off as a weak absolute symbol, so we can override it > for the kernel.
This works if you rebase the per cpu area at zero. gs:0x68 is still the stack canary.
The i386 method does not work because the segment register does not directly point to the pda.
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