Re: [rfa:NetBSD/ppc] Implement signal trampoline unwinder

Kevin Buettner
2004-03-02T22:21:35Z

On Sun, 29 Feb 2004 20:05:28 -0500
Andrew Cagney <cagney@gnu.org> wrote:

> * ppcnbsd-tdep.c: Include "trad-frame.h", and "frame-unwind.h".
> (struct ppcnbsd_sigtramp_cache, ppcnbsd_sigtramp_this_id)
> (ppcnbsd_sigtramp_prev_register, ppcnbsd_sigtramp_cache)
> (ppcnbsd_sigtramp_sniffer, ppcnbsd_sigtramp_unwind)
> (ppcnbsd_init_abi): Implement a NetBSD/PPC signal trampline
> unwinder, register.

After reading the disucssion, the only part about this which bothers
me is the part that you yourself had a question about:

> + if (frame_pc_unwind (next_frame) > 0x7f000000)
> + /* Assume anything that is vaguely on the stack is a signal
> + trampoline. */
> + return &ppcnbsd_sigtramp_unwind;

Given Mark K's comments, I think it would be better to check for a
specific instruction sequence. I know it's expensive, but it seems
like a more robust approach. (But, also given Mark K's comments,
it seems that a name based approach will work well in the future.)

Kevin