Messages in this thread | | | Date | Wed, 11 Feb 2009 09:59:23 -0500 | Subject | Re: [PATCH 2/3] x86: Pass in pt_regs pointer for syscalls that need it | From | Brian Gerst <> |
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On Wed, Feb 11, 2009 at 9:48 AM, Tejun Heo <htejun@gmail.com> wrote: > Tejun Heo wrote: >>> I checked the disassembly of these functions and didn't see this >>> happen on gcc 4.3.0. >> >> Well, tracking down why run_init_process() is returning 0 with >> -fstack-protector wasn't much of fun. These breakages are very subtle >> and if we're gonna pass in pointer to pt_regs anyway and thus can >> guarantee such breakage can't happen at no additional cost, I think we >> should do that even if it means slightly more argument fetching in a >> few places. > > In addition, if we do that, we can remove the horrible > asmlinkage_protect() thing altogether.
Like I said before, the tail-call optimization problem isn't limited to just this set of syscalls. There are only two real ways to fix it. 1) Set up a real stack frame for the syscalls instead of overalying pt_regs, or 2) patch gcc to tell it not to touch the args area of the stack.
-- Brian Gerst
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