Re: [PATCH] sparc: Improve setjmp()

[Jeff Johnston <jjohnstn@redhat.com>]

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On Thu, Oct 12, 2023 at 10:55 AM Sebastian Huber <
sebastian.huber@embedded-brains.de> wrote:

> Hello Jeff,
>
> On 12.10.23 16:50, Jeff Johnston wrote:
> > Hi Sebastian,
> >
> > I am not familiar with sparc to comment, but Corinna has performed
> > maintenance on the setjmp.S file if
> > you want to wait for her to look at the change.  Otherwise, if you have
> > a test case that
> > verifies the change, feel free to merge and you can confirm with Corinna
> > when she is back.
>
> the glibc version does also the window flush. I noticed the issue by
> testing compiler builtins which on some systems result in a trap, for
> example:
>

Then by all means go ahead and check it in.

-- Jeff J.

>
>      volatile int64_t n;
>      volatile int64_t d;
>
>      n = INT64_C( 0 );
>      d = INT64_C( 0 );
>      do_longjmp = true;
>
>      if ( setjmp( exception_return_context ) == 0 ) {
>        n = n % d;
>      }
>
> In RTEMS, we use a processor-specific stack to handle synchronous
> exceptions. If you want to jump back to the thread from the exception
> handler, then you have to change back to the original thread stack. This
> works only if you flush the windows in the setjmp().
>
> >
> > -- Jeff J.
> >
> >
> > On Thu, Oct 12, 2023 at 5:39 AM Sebastian Huber
> > <sebastian.huber@embedded-brains.de
> > <mailto:sebastian.huber@embedded-brains.de>> wrote:
> >
> >     On 06.10.23 07:31, Sebastian Huber wrote:
> >      > Flush the windows in setjmp().  This helps if the stack is
> >     changed after
> >      > the setjmp() and we want to jump back to the original stack using
> >      > longjmp().
> >      > ---
> >      >   newlib/libc/machine/sparc/setjmp.S | 2 ++
> >      >   1 file changed, 2 insertions(+)
> >      >
> >      > diff --git a/newlib/libc/machine/sparc/setjmp.S
> >     b/newlib/libc/machine/sparc/setjmp.S
> >      > index 613df2ba2..d7185be4c 100644
> >      > --- a/newlib/libc/machine/sparc/setjmp.S
> >      > +++ b/newlib/libc/machine/sparc/setjmp.S
> >      > @@ -110,6 +110,8 @@
> >      >
> >      >   ENTRY(setjmp)
> >      >   ENTRY(_setjmp)
> >      > +        ta      0x03            /* Flush registers, just in case
> >     another stack
> >      > +                                   is used after the setjmp().
> */
> >      >           st      %sp, [%o0]      /* caller's stack pointer */
> >      >           st      %i7, [%o0+4]    /* caller's return pc */
> >      >           st      %fp, [%o0+8]    /* store caller's frame pointer
> */
> >
> >     I am not sure if there is anyone left being able to review this
> change.
> >
> >     --
> >     embedded brains GmbH
> >     Herr Sebastian HUBER
> >     Dornierstr. 4
> >     82178 Puchheim
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> --
> embedded brains GmbH
> Herr Sebastian HUBER
> Dornierstr. 4
> 82178 Puchheim
> Germany
> email: sebastian.huber@embedded-brains.de
> phone: +49-89-18 94 741 - 16
> fax:   +49-89-18 94 741 - 08
>
> Registergericht: Amtsgericht München
> Registernummer: HRB 157899
> Vertretungsberechtigte Geschäftsführer: Peter Rasmussen, Thomas Dörfler
> Unsere Datenschutzerklärung finden Sie hier:
> https://embedded-brains.de/datenschutzerklaerung/
>
>