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

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
[off-list ref] wrote:

quoted

quoted

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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