sparc and trap 4 (floating point disabled)

Schweikhardt, Jens (TSPCE3-TL4) Jens.Schweikhardt at
Tue Dec 3 14:48:30 UTC 2019

Hello, world\n

I have a question about the use of trap 4 by RTEMS on Sparc32 (leon3).
Since our app needs FP, we set the PSR[EF] bit during the boot process before RTEMS is invoked.
Since we don't expect the fp_disabled trap (4) to occur, we install a fatal handler for it with
rtems_interrupt_catch(&fatalTrapHandler, 4, &old);

However, the fatalTrapHandler is invoked a short time after application start (we use the Init() task
and start a handful of additional tasks, all of which have attribute RTEMS_FLOATING_POINT)
and the PSR[EF] bit is indeed cleared. None of our tasks
clears that bit, so we suspect RTEMS does it for some reason.

Question: is an RTEMS/sparc application allowed to install a handler for trap 4? I could not find an
answer in the docs for SPARC Specific Information.

Thanks for any insight!
Regards, Jens


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