Re: [ECOS] cyg_hal_gdb_interrupt

[John Newlin <jnewlin at rawbw dot com>]

> John Newlin <jnewlin@rawbw.com> writes:
>
> > In file:
> > packages/hal/common/current/src/hal_stub.c
> >
> > There is this wonderful function: cyg_hal_gdb_interrupt
> >
> > This function saves the current instruction, and installs a break
> > instruction.  Generally this is safe, but on the Xtensa architecture
> > instructions can be on any address alignment, which will cause the load of
> > the old instruction and store of the new instruction to generate an
> > exception.
> >
> > Is there a general way to override this function, or if I made a change to
> > do a memcpy instead of load/store would you accept that back into the
> > tree?
>
> The ususal approach here is for the HAL to supply a substitute
> routine. The ARM HAL does this since it has to deal with 32 bit ARM
> breakpoints and 16 bit Thumb breakpoints, and has to decide which to
> plant at runtime.

That means anytime an architecture wants to override those functions,
there has to be a change to the common code in order to support an
architecture.

Would it be better to just put in something more generic, like:

#ifndef CYGARG_HAS_HAL_GDB_INTERRUPT
...
#endif

Instead of:

#ifndef CYGARC_HAL_ARM (or whatever it was)
#endif

Or just mark the function as a weak symbol, and let the linker sort it
out.  :)


Anyhow, I submitted a patch that changed direct load/store to use the
appropriate memread/memwrite functions, which seems better anyhow
(especially since my gdb stub works now).


-john


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