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Re: RFA/ARM: Switch mode when setting PC
- From: Daniel Jacobowitz <drow at mvista dot com>
- To: Andrew Cagney <cagney at gnu dot org>
- Cc: gdb-patches at sources dot redhat dot com, rearnsha at arm dot com
- Date: Fri, 16 Jan 2004 09:10:40 -0500
- Subject: Re: RFA/ARM: Switch mode when setting PC
- References: <20040116035402.GA3215@nevyn.them.org> <40077A12.email@example.com>
On Fri, Jan 16, 2004 at 12:43:46AM -0500, Andrew Cagney wrote:
> >This patch fixes several failures in virtfunc.exp for arm-sim/-mthumb. The
> >problem is that the non-virtual thunk for pDe->vg() is emitted in ARM mode
> >and called via _call_via_r2. But the rest of the program is Thumb mode,
> >nothing tells the simulator (or target; I haven't tested this on hardware
> >yet but I expect the same result) to switch to ARM. So it gets very
> >This is somewhat suboptimal in that if you want, for some reason, to call
> >something marked as an ARM function with Thumb mode enabled you will have
> >set $ps yourself _after_ setting $pc. I think it's still a good idea,
> >though. OK?
> (sorry, but I don't understand that paragraph - doesn't that code set
> the $ps after setting the $pc?)
Right. But if you want to start a Thumb function in ARM mode you'll
have to do:
(gdb) set $pc = start_of_function
(gdb) set $ps = $ps & ~0x20
> The ari contains this yellow card:
> write pc
> Replace write_pc() with get_frame_base_address or get_frame_id; at
> present the inferior function call code still uses this when doing a
> the concern is with the way write_pc is being called to perform two
> different operations:
> - decrement the pc just after the target stops
> - jump to a specific address
> As with an inferior function call or jump.
> I think it would be better to have two methods so that it's clear that
> this case only applies when doing a jump.
Well, it'd be better to rip out the current DECR_PC_AFTER_BREAK and
handle it completely within the four (roughly) affected targets,
thereby removing the overloading of write_pc. IMVHO.
MontaVista Software Debian GNU/Linux Developer