Powerpc IRQ handling breaks strict EABI compliance

[Joel Sherrill]

Till Straumann wrote:
> 
> Joel Sherrill wrote:
> >
> > Sergei Organov wrote:
> >
> >>Till Straumann <strauman at SLAC.Stanford.EDU> writes:
> >>
> >>>OK, I fixed the motorola/shared BSP to not clobber R2/R13 anymore.
> >>>However, the question remains:
> >>>
> >>>  - who is responsible for the setup (calling __eabi()) ?
> >>>    RTEMS or application code?
> >>
> >>It's main() that when compiled with corresponding gcc switches automatically
> >>invokes __eabi(). It basically only setups R2/R13. BTW, R13 is being used even
> >>without EABI -- R13 usage is part of SYSV ABI which EABI is derived from.
> >>
> >>This brings another interesting problem. In older days of RTEMS the 'main' was
> >>part of RTEMS, not the part of application code, so it was invoked very early
> >>and thus all RTEMS/BSP initialization went after __eabi() has been called.
> >>AFAIK, now situation is different and __eabi() will be invoked too late. It
> >>means that RTEMS startup code should invoke __eabi() (or setup R13/R2 itself)
> >>for things to work correctly as C startup/initialization code compiled for
> >>SYSV ABI/EABI will already rely on correct values in R2/R13.
> >
> >
> > RTEMS now ensures that the first thread to execute invokes the
> > appropriate
> > routine for that gcc target to run global constructors.  The
> > powerpc-rtems
> > gcc target is noted as being an init/fini target so it will call
> > _init().
> >
> >
> 
> OK, I saw that bsp_specs have been updated to include crtbegin/crtend.
> However, how do you prevent from initialization happening twice if
> the user uses 'main'?

My memory is that the __init functions have a boolean variable that
say they have been executed already.

> -- Till.
> 
> >>What I want to tell is that using of SYSV ABI/EABI indeed makes code smaller
> >>and faster, so it'd be fine if PPC port of RTEMS starts to support it again
> >>(the old RTEMS 3.x code did support it, BTW).
> >
> >
> > The application owning main() was generally viewed as an improvement. :)
> >
> > In the olden days, main() happened too early and drivers were not yet
> > initialized.
> > This lead to situations where global constructors could not print or do
> > other operations.
> >
> >
> >>--
> >>Sergei.
> >
> >

-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel at OARcorp.com                 On-Line Applications Research
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