Messages in this thread | | | Date | Thu, 14 Jun 2012 17:16:30 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [RFC] x86, fpu: unify signal handling code paths for x86 and x86_64 kernels |
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On 06/14/2012 05:10 PM, Suresh Siddha wrote: > > For the above mentioned reason, I guess the current usage of > is_ia32_task() in copy_siginfo_to_user32() (added recently for x32 > support) is broken, as the TS_COMPAT flag may not be set for the x86 > compat mode apps in those paths. > > Peter offline suggested that the signal delivery path should probably > set/clear the TS_COMPAT flag (just like we do it for syscall paths), so > that is_ia32_task() will work in those paths. > > But the exception paths for the 32bit and 64bit apps in the 64-bit > kernel is same. So I really need to use something like TIF_IA32 to find > out the compat mode of the task. Anyways, the comment in the below patch > explains the problem ;) What should we do? Just remove the > is_ia32_task() checks in signal paths and just use TIF_IA32 or do > something like below. > > My personal preference is to use TIF_IA32 check and avoid the usage of > is_ia32_task() in the signal delivery paths.
That is the quick fix, but...
> Signal return goes through a system call which already sets the > TS_COMPAT. It is the signal delivery that is causing the asymmetry.
Yes, and I think you missed some aspects of my statement: the notion would be that TS_COMPAT would be set from the TIF_IA32 flag at the time we decide to deliver a signal, the signal being a pseudo-system-call. However, the more I wonder about if that will confuse the crap out of ptrace, so using TIF_IA32 might just be the best thing anyway.
-hpa
-- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.
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