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Re: [patch/rfc] signal trampoline frames
- From: Daniel Jacobowitz <drow at false dot org>
- To: Andrew Cagney <cagney at gnu dot org>
- Cc: gdb-patches at sources dot redhat dot com
- Date: Tue, 23 Mar 2004 18:09:30 -0500
- Subject: Re: [patch/rfc] signal trampoline frames
- References: <405E5A09.2050803@gnu.org>
On Sun, Mar 21, 2004 at 10:14:17PM -0500, Andrew Cagney wrote:
> Hello,
>
> This adds "tramp-frame.[hc]" as a generic signal trampoline frame
> unwinder. The client architectures, per the revised change to
> ppcnbsd-tdep.c (it superseeds my original), just needs to provide the
> signal trampoline instruction sequence and a method to initialize the
> trad_frame_cache.
>
> Thoughts, I'll look to commit the tramp-frame parts in a few days.
Some minor comments.
> +static CORE_ADDR
> +tramp_frame_start (CORE_ADDR pc, const struct tramp_frame *tramp)
> +{
> + int ti;
> + /* Search through the trampoline for one that matches the
> + instruction sequence around PC. */
> + for (ti = 0; tramp->insn[ti] != 0; ti++)
> + {
> + CORE_ADDR func = pc - tramp->insn_size * ti;
> + int i;
> + for (i = 0; 1; i++)
> + {
> + bfd_byte buf[sizeof (LONGEST)];
> + CORE_ADDR insn;
tramp->insn is a ULONGEST. Both of these should probably be ULONGEST
also.
> + if (tramp->insn[i] == 0)
> + return func;
So zeros in tramp->insn mark the end of the sequence? Should document
that, zeros are valid instructions and some bizarre architecture might
use one as a syscall trap.
> + /* If the function has a valid symbol name, it isn't a
> + trampoline. */
> + find_pc_partial_function (pc, &name, NULL, NULL);
> + if (name != NULL)
> + return 0;
> + /* If the function lives in a valid section (even without a starting
> + point) it isn't a trampoline. */
> + if (find_pc_section (pc) != NULL)
> + return 0;
I believe the first check is redundant to the second check; can we have
names without sections? I may be wrong about this, remembering the
problem on IRIX with absolute sections.
--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer