Messages in this thread | | | From | Andi Kleen <> | Subject | Re: [discuss] Re: [PATCH] x86-64: adjust ia32entry.S | Date | Fri, 11 Nov 2005 16:53:52 +0100 |
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On Friday 11 November 2005 16:50, Jan Beulich wrote: > >>> Andi Kleen <ak@suse.de> 11.11.05 16:34:44 >>> > > > >On Wednesday 09 November 2005 17:10, Jan Beulich wrote: > >> IA32 compatibility entry points needlessly played with extended > >> registers. Additionally, frame unwind information was still > > incorrect > > >> for ia32_ptregs_common (sorry, my fault). > > > >What do you mean with needlessly played? That it didn't initialize > >all on the stack frame? That was more a feature than a bug. > >Did it cause you problems? > > It saved and restored R12-R15, even though these registers have no > meaning (and are architecturally undefined) when coming from/going to > 32-bit mode. Problems? No, except that without the extra loads (stores > don't matter that much I believe) performance is better...
int 0x80 can be called from long mode too. We especially kept this option to allow JITs like valgrind to run a 32bit process in a 64bit image. In this case we shouldn't leak kernel registers.
You're right they normally shouldn't be leaked anyways because the C ABI will save/restore it. I will think about it.
> > >In general I'm weary of making the asm macros more complex > >(adding more arguments etc.) Please keep it simple. > > Then ignore this, perhaps with the exception of the unwind info > adjustment.
Can you please resubmit that as a separate patch?
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