Subject: Re: ARM exception handlers -- question
To: Ben Harris <email@example.com>
From: Jason R Thorpe <firstname.lastname@example.org>
Date: 11/09/2001 07:37:01
On Fri, Nov 09, 2001 at 01:30:08PM +0000, Ben Harris wrote:
> The comment means that it shouldn't be called from an exception handler
> that's entered in SVC32 mode (which I think is just SWI). Data aborts are
> handled in ABT32 mode, so using PUSHFRAMEINSVC is fine.
Ah, duh, of course.
> > Obviously, I want to be storing SVC_sp and SVC_lr (which should be no
> > problem in a fixed fault handler, since this op is done after switing
> > from ABT mode to SVC mode).
> A few lines earlier:
> str r0, [sp, #-4]!; /* Push return address */ \
> str lr, [sp, #-4]!; /* Push SVC lr */ \
> str r2, [sp, #-4]!; /* Push SVC sp */ \
> These get restored by the final LDMIA in PULLFRAMEFROMSVCANDEXIT.
Wow, blind, I am. Okay, and the r0 there (which is copied from ABT_lr)
is stored in tf_pc?
> As above, PUSHFRAMEINSVC puts both the SVC and USR registers in the
> trapframe, and PULLFRAMEFROMSVCANDEXIT pops them. data_abort_handler
> twiddles tf_pc as necessary to return to the right place.
Ok, so I'm back to my original problem then, I suppose -- "Why didn't
my original badaddr() work?" I've also attempted implementing it like
the pcb_onfault stuff is implemented, and I lose, as well. Sigh, I'm
beginning to think I'm going to have to use the (Windows-only) JTAG
debugger to figure this one out :-/
-- Jason R. Thorpe <email@example.com>