Re: .eh_frame

[Joerg Sonnenberger <joerg%britannica.bec.de@localhost>]

On Mon, Nov 10, 2014 at 06:06:54PM +0000, Andrew Cagney wrote:
> On 9 November 2014 17:12, Joerg Sonnenberger <joerg%britannica.bec.de@localhost> wrote:
> >> >> o .eh_frame in kernel is not used yet, and safely removed from /netbsd
> >> >
> >> > Please do not.
> >>
> >> o Is it correct that .eh_frame is not used by anything at all at the moment?
> >
> > gdb should in principle, haven't tried. libunwind is not hooked into ddb
> > (yet).
> 
> Can you be more specific?
> 
> A remote debugger will call on either .debug_frame or .eh_frame when
> generating a back-trace - what it uses depends on what it chooses to
> look for first at each address. In fact, ignoring the potential for
> bugs, you could:
> - strip .eh_frame
> - strip all debug info except .debug_frame
> and still have good back-traces without weighing down the kernel's
> text segment with .eh_frame info.

Consider x86_64 where you can't do reliable stack unwinding without also
disabling -fomit-frame-pointer. The question is not about .debug_frame
vs .eh_frame, you don't get the former at all without explicitly asking
for debug data.

Joerg