From: Andrew Cagney <ac131313@redhat.com>
To: "Theodore A. Roth" <troth@openavr.org>
Cc: gdb@sources.redhat.com
Subject: Re: avr and frame unwinding
Date: Sun, 08 Jun 2003 19:15:00 -0000 [thread overview]
Message-ID: <3EE38B4B.3020100@redhat.com> (raw)
In-Reply-To: <Pine.LNX.4.44.0306081041190.32526-100000@bozoland.mynet>
> :):)Is this arrithmetic correct - I understand the ``* 2'' but not the ``>>8''.
> :):)
> :):)> pc = (extract_unsigned_integer (buf, 2) * 2) >> 8;
> :)
> :)That's the ugly part I don't understand. It seems to give the correct
> :)result, but now that I think about it more, it could mean that my memory
> :)address is off by 1. I will have to re-examine that.
> :)
> :):)
> :):)this memcpy will need to be a
> :):)
> :):) store_unsigned_integer (bufferp, pc, SIZEOF_AVR_PC);
> :):)
> :)
> :)I tried that, but it performed a endian byte swap and the PC came out wrong.
> :)I dug around and saw what looked to be too many byte swaps.
> :)
> :):)> memcpy (bufferp, &pc, sizeof(pc));
> :):)> }
> :):)> else
> :):)> {
> :):)> read_memory (this_saved_regs[regnum], bufferp,
> :):)> register_size (current_gdbarch, regnum));
> :):)> }
>
> I think found the root of the ugliness. When the avr performs a call
> instruction the PC is pushed onto the stack, but it turns out that it is
> pushed in big endian order. For the most part though, the avr is little
> endian.
That would explain it. I guess it needs an explicit big endian extract
followed by a little endian store (via store_unsigned_integer).
Andrew
prev parent reply other threads:[~2003-06-08 19:15 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-06-06 0:35 Theodore A. Roth
2003-06-06 2:01 ` Andrew Cagney
2003-06-07 20:23 ` Theodore A. Roth
2003-06-07 22:37 ` Andrew Cagney
2003-06-08 0:26 ` Theodore A. Roth
2003-06-08 17:51 ` Theodore A. Roth
2003-06-08 19:15 ` Andrew Cagney [this message]
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