[PATCH] sparc: Improve setjmp()

[Sebastian Huber]

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:

     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
>     Germany
>     email: sebastian.huber@embedded-brains.de
>     <mailto:sebastian.huber@embedded-brains.de>
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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

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Registernummer: HRB 157899
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