Messages in this thread | | | Date | Sun, 14 Nov 2021 12:03:05 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 3/3] x86_64: Use relative per-cpu offsets |
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On Sat, Nov 13, 2021 at 11:54:19PM -0500, Brian Gerst wrote: > On Sat, Nov 13, 2021 at 8:18 PM Andy Lutomirski <luto@kernel.org> wrote: > > > > > > > > On Sat, Nov 13, 2021, at 4:40 AM, Brian Gerst wrote: > > > The per-cpu section is currently linked at virtual address 0, because > > > older compilers hardcoded the stack protector canary value at a fixed > > > offset from the start of the GS segment. Use a standard relative offset > > > as the GS base when the stack protector is disabled, or a newer compiler > > > is used that supports a configurable location for the stack canary. > > > > Can you explain the benefit? Also, I think we should consider dropping support for the fixed model like we did on x86_32. > > This patch probably makes more sense if we drop the fixed model, as > that gets rid of alot of code that works around having to link the > percpu section differently.
Can someone spell out these benefits please? To me having per-cpu start at 0 makes perfect sense, how does not having that make things better?
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