Re: Compat 32-bit syscall entry from 64-bit task!?

["H. Peter Anvin" <hpa@zytor.com>]

On 02/10/2012 02:42 PM, Indan Zupancic wrote:
>> #include <stdnak.h>
> 
> Could you please elaborate? Is it just the stealing of eflags bits that
> irks you or are there technical problems too?

Yes, I will not accept that unless it gets ok'd by the architecture
people, which may take a long time.

> I understand some people would prefer a new regset, but that would force
> everyone to use PTRACE_GETREGSET instead of whatever they are using now.
> The problem with that is that not all archs support PTRACE_GETREGSET, so
> the user space ptrace code needs to use different ptrace calls depending
> on the architecture for no good reason. If PEEK_USER works then it's less
> of a problem, then it's one extra ptrace call compared to the eflag way
> if PTRACE_GETREGS is used. If this new info is exposed with a special
> regset instead of being appended to normal regs then one extra ptrace
> call per system call event needs to be done. You can as well add special
> x86 ptrace requests then.

Seriously... if you're mucking with registers on this level, youan
architecture dependency is not a big deal, and perhaps it's a good sign
that the laggard architectures need to catch up.  If multiple ptrace
requests is a problem, then perhaps this is a good sign that we need a
single way to get multiple regsets in a single request?

> Or is the main advantage of using a regset that it shows up in coredumps?
> That would merit the extra effort at least.

That is another plus, which is significant, too.  The final advantage is
expandability.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.