On Sun, Apr 07, 2013 at 12:00:50PM +0200, Michael Kerrisk (man-pages) wrote:
> [Adding a few people to CC who may be able to help with Mike's doubts
> on PA-RISC; folks, if any of you could have a quick look at the parisc
> piece below, that would be helpful]
>
The syscall number is in %r20, everything else looks correct. The
returned value is in %r28 and the args are %r26 through %r21.
--Kyle
> Mike,
>
> On Wed, Apr 3, 2013 at 1:17 AM, Mike Frysinger <vapier@xxxxxxxxxx> wrote:
> > On Tuesday 02 April 2013 02:54:39 Michael Kerrisk (man-pages) wrote:
> >> On Mon, Apr 1, 2013 at 12:32 PM, Mike Frysinger wrote:
> >> > On Monday 01 April 2013 05:29:11 Michael Kerrisk (man-pages) wrote:
> >> >> On Mon, Apr 1, 2013 at 10:29 AM, Mike Frysinger wrote:
> >> >> > on a related topic, would it be useful to document the exact calling
> >> >> > convention for architecture system calls ? from time to time, i need
> >> >> > to reference this, and i inevitably turn to a variety of sources to
> >> >> > dig up the answer (the kernel itself, or strace, or qemu, or glibc,
> >> >> > or uClibc, or lss, or other random places). i would find it handy to
> >> >> > have all of these in a single location.
> >> >>
> >> >> Sounds like it would be useful to have that documented. Would you have
> >> >> a chance to write patches for that?
> >> >
> >> > should we do it in syscall(2) ? or a dedicated man page ?
> >>
> >> It's a little hard to say until I see the shape of what comes. Can you
> >> provide a rough per-syscall example or two of what you expect to
> >> document? (Don't write too concrete a patch yet, until I can get a
> >> handle on what you intend.)
> >
> > this renders nicely i think. it shows most of the stuff i'm interested in.
> > might be useful to add a dedicated section covering the clobbers in the
> > future.
>
> Thanks for that. It looks good to me, and I have applied. But it
> renders too wide (wherever possible, I try to ensure that everything
> renders inside 80 columns), so I have split into tables, one with
> "instruction, NR, ret" and another with the arguments (arg1 to arg7).
>
> Now, just to make 100% sure of your intention, the NR column would be
> better named "syscall #" (or similar), right? (I've made that change.)
>
> > --- a/man2/syscall.2
> > +++ b/man2/syscall.2
> > @@ -79,6 +79,35 @@ and an error code is stored in
> > .BR syscall ()
> > first appeared in
> > 4BSD.
> > +.SS Architecture calling conventions
> > +Every architecture has its own way of invoking & passing arguments to the
> > +kernel.
> > +Note that the instruction listed below might not be the fastest or best way to
> > +transition to the kernel, so you might have to refer to the VDSO.
>
> Mike, any chance that I could interest you in writing a vdso(7) man
> page? I've felt the lack of such a page for a while (it need not be
> too long), but am not deep enough into the details to write it easily
> (I am not sure if you are).
>
> > +Also note that this doesn't cover the entire calling convention -- some
> > +architectures may indiscriminately clobber other registers not listed here.
> > +.if t \{\
> > +.ft CW
> > +\}
> > +.TS
> > +l l l l l l l l l l l.
> > +arch/ABI insn NR ret arg1 arg2 arg3 arg4 arg5 arg6 arg7
> > +_
> > +arm/OABI swi NR; - a1 a1 a2 a3 a4 v1 v2 v3
> > +arm/EABI swi 0x0; r7 r1 r1 r2 r3 r4 r5 r6 r7
> > +bfin excpt 0x0; P0 R0 R0 R1 R2 R3 R4 R5 -
> > +i386 int $0x80; eax eax ebx ecx edx esi edi ebp -
> > +ia64 break 0x100000; r15 r10/r8 r11 r9 r10 r14 r15 r13 -
> > +.\" not sure about insn or NR
> > +.\" parisc ble 0x100(%%sr2, %%r0); - r28 r26 r25 r24 r23 r22 r21 -
>
> PA-RISC folks, are you able to confirm/correct the above?
>
> > +sparc/32 t 0x10; g1 o0 o0 o1 o2 o3 o4 o5 -
> > +sparc/64 t 0x6d; g1 o0 o0 o1 o2 o3 o4 o5 -
> > +x86_64 syscall; rax rax rdi rsi rdx r10 r8 r9 -
> > +.TE
> > +.if t \{\
> > +.in
> > +.ft P
> > +\}
> > .SS Architecture-specific requirements
> > Each architecture ABI has its own requirements on how
> > system call arguments are passed to the kernel.
>
> Cheers,
>
> Michael
>
> --
> Michael Kerrisk
> Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
> Author of "The Linux Programming Interface"; http://man7.org/tlpi/
>
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