support for ARM GNU/Linux

[Richard Earnshaw]

ac131313@cygnus.com said:
> I'm slightly curious about what is going on with all these different
> breakpoints (I should hasten to point out that I'm _not_ the ARM
> expert/maintainer :-).  Stan Shebs recently commited the change:

> 	1999-03-02  Stan Shebs  <shebs@andros.cygnus.com>

> 	From Gary Thomas  <gthomas@cygnus.co.uk>:
> 	* arm-tdep.c (ARM_LE_BREAKPOINT, ARM_BE_BREAKPOINT,
> 	THUMB_LE_BREAKPOINT, THUMB_BE_BREAKPOINT): Use illegal instruction
> 	instead of SWI 24.
> 	* config/arm/tm-arm.h (CALL_DUMMY): Ditto.
> 	(IN_SIGTRAMP): Define. 


A bit of history.  SWI 24 was the breakpoint swi in RISC iX, which the 
kernel understood (in some way).  I don't know if it was necessary to use 
exactly that SWI if you were using gdb or if the same effect could be 
achieved with other illegal instructions.

A side-note, before ARM Architecture v4 many "undefined" instruction 
formats aren't guaranteed to take the undefined instruction trap.  Also 
note that, in this respect, the ARM7TDMI is NOT fully ARM v4 compliant.

I don't know if anyone cares about RISC iX support any more (though gcc 
still supports it).

Richard.