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

[ldv@altlinux.org (Dmitry V. Levin)]

Hi,

On Thu, Jan 26, 2012 at 07:03:43PM +0100, Denys Vlasenko wrote:
> Hi Linus,
> 
> On Thu, Jan 26, 2012 at 4:47 AM, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> >> Please look at strace source, get_scno() function, where
> >> it reads syscall no and parameters. Let's see....
> >> - POWERPC: has 32-bit and 64-bit mode
> >> - X86_64: has 32-bit and 64-bit mode
> >> - IA64: has i386-compat mode
> >> - ARM: has more than one ABI
> >> - SPARC: has 32-bit and 64-bit mode
> >>
> >> Do you want to re-invent a different arch-specific way to report
> >> syscall type for each of these arches?
> >
> > I think an arch-specific one is better than trying to make some
> > generic one that is messy.
> >
> > As you say, many architectures have multiple system call ABIs.
> >
> > But they tend to be very *different* issues. They can be about
> > multiple ABI's, as you mention, and even when they *look* similar
> > (32-bit vs 64-bit ABI's) they are actually totally different issues.
> > [skip]
> 
> I don't have a particular attachment to my solution,
> and I think we already talk about this problem for
> far too long.
> 
> Looks like nobody is _strongly_ opposed to your patch
> which uses a few bits in eflags to report bitness
> of the x86 syscall.
> 
> Lets just do that already. If you commit it to kernel git,
> I will immediately change strace accordingly.

Is there any progress with this (or any alternative) solution?

I see the kernel side has changed a bit, and the strace part
is in a better shape than 5 years ago (although I'm biased of course),
but I don't see any kernel interface that would allow strace to reliably
recognize this 0x80 case.


-- 
ldv
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