multi-arch and CALL_DUMMY_BREAKPOINT_OFFSET

[Richard Earnshaw <rearnsha at arm dot com>]

I guess I'm going to find several things like this...

Well it appears that in a multi-arch gdb (even at level 1), 
CALL_DUMMY_BREAKPOINT_OFFSET can only be a constant for any particular 
architecture.  This is a problem, because on the ARM it is currently a 
function that returns one of two values depending on whether the 
call-dummy stub has to be ARM code or Thumb code.  Note that both types of 
code can exist within a single application and it is not always safe to 
assume that every function is interworking safe.

I guess I could re-write the whole of the call-dummy stuff so that 
appropriate breakpoints are built in, but that is certainly going to be 
non-trivial.

Any suggestions?  Can I diddle with the gdbarch setting dynamically -- eg 
by calling gdbarch_set_call_dummy_breakpoint_offset() from within 
arm_fix_call_dummy()?  It's quite gross, but it might work.

Long term it would probably be better to rewrite the call-dummy handling 
to remove the covert variable that is used to communicate between the 
various call-dummy stubs, but I'd rather not do that now.

R.