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Re: RFC: Unwind info for PLT
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Richard Henderson <rth at twiddle dot net>
- Cc: libc-alpha at sourceware dot org, binutils at sourceware dot org, gdb at sourceware dot org, Mark Wielaard <mjw at redhat dot com>, Frank Eigler <fche at redhat dot com>
- Date: Mon, 13 Jun 2011 19:13:52 +0200
- Subject: Re: RFC: Unwind info for PLT
- References: <20110610074524.GR17079@tyan-ft48-01.lab.bos.redhat.com> <4DF23519.firstname.lastname@example.org>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Fri, Jun 10, 2011 at 08:15:37AM -0700, Richard Henderson wrote:
> On 06/10/2011 12:45 AM, Jakub Jelinek wrote:
> > Anyway, I think hardcoding this in the linker would be problematic,
> > we couldn't tweak it, so providing some special hidden symbols around
> > the .plt section and let glibc crtfiles provide it sounds like the best
> > option to me.
> Would it be problematic beyond the fact that it's easier to write the
> directives in assembler than it is within bfd?
Yeah, easier to write and easier to change. Anyway, if you prefer to do
it in ld, I can try to do it there. Just a question, should it be done
unconditionally, or guarded with some ld cmdline option (either existing one, like
abuse --eh-frame-hdr for it, or a new one)?
On other targets like SPARC or PowerPC -mbss-plt it is the dynamic linker
which updates or completely writes .plt section though, should in that
case the dynamic linker provide the unwind info instead?
> As for the actual unwind info, I agree that using pointer arithmetic
> is the better expression over decoding the insns. Increasing the
> alignment is probably a good idea, also for the actual decoding of
> the insns on the real hardware.