Re: [parisc] double restarts on multiple signal arrivals

[Grant Grundler <grantgrundler@gmail.com>]

+patofiero,anglin

On Fri, May 18, 2012 at 12:56 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Fri, May 18, 2012 at 11:05:46AM -0700, Grant Grundler wrote:
>> On Fri, May 18, 2012 at 10:58 AM, Al Viro <viro@zeniv.linux.org.uk> wrote:
>> ...
>> >?Except for that mess with multiple
>> > pending signals, the value we have in r28 on syscall entry doesn't
>> > seem to affect the syscall behaviour... ?Some HPUX compat fun?
>>
>> We stopped trying to support HPUX compat support probably 8 or so
>> years ago. Since HP didn't care, no one else did either.  So no need
>> to consider it now.
>
> BTW, what should we put into the trampolines of subsequent sigframes
> when we are building more that one?

Sorry - I only knew about the state of the HPUX support...Carlos and
Dave (and a few others) understand the syscall interface. I've include
them directly and hopefully they can respond soon.

cheers,
grant

>  I.e. suppose we are in a syscall
> and see two signals.  We build a sigframe for the first one, with
> r25 = 1, call rt_sigreturn() in it.  Return address of original syscall
> is stored into sigcontext of that frame, our return address set to the
> entry point of handler1.  Now we see the second signal and build another
> sigframe.  That one will have the entry point of the first handler stored
> in sigframe and we'll set the things up so that return to userland will
> land us in the entry of handler2.  Fine, but... what should we have in r25
> for rt_sigreturn() in the second trampoline?
>
> We return to userland and find ourselves in the beginning of handler2.
> It's executed and eventually we return from it.  We are at the beginning
> of the second trampoline now.  rt_sigreturn() is called, restores the
> registers from the second sigcontext and returns to userland.  We are at
> the beginning of handler1.  It is executed and returns.  We are at the
> beginning of the first trampoline.  rt_sigreturn() _there_ restores the
> original registers from the first sigcontext and we finally return to the
> insn right after the original syscall (or to the syscall itself if we
> took a syscall restart).
>
> That final rt_sigreturn() will go through syscall_exit; OK, no problem
> with that.  But should the earlier one (done after return from handler2()
> and landing us at the entry of handler1) go through syscall_exit or
> through syscall_exit_rfi?