Re: Can objdump show friendly symbolic function name?

[David Daney <david dot s dot daney at gmail dot com>]

On 07/22/2010 04:57 AM, Maciej W. Rozycki wrote:
> On Wed, 21 Jul 2010, Richard Sandiford wrote:
>
> > > > It would certainly be possible to do the same thing in objdump,
> > > > and FWIW, I did wonder about that when adding the readelf -A GOT dump.
> > > > The problem is that, in a multi-GOT world, the annotations are only
> > > > ever going to be a best guess.  If the disassembler sees:
> > > >
> > > >       lw    $2,-32000(gp)
> > > >
> > > > it doesn't in general know whether gp points to the primary
> > > > (ABI-defined) GOT, or to some secondary GOT.  If it guesses
> > > > right, the annotation would be useful, but if it guesses wrong,
> > > > the annotation would be very misleading.  This is different from
> > > > the current<foo>  markers, which are always accurate (or at least,
> > > > _should_ always be accurate).
> > >
> > >   Can the GOT pointer switch between GOTs within a single function?
> >
> > No.
>
>   I suppose it should be moderately easy to decode the prologue of each
> function then to see which GOT $gp refers to.

Modern GCCs will not generate a fixed function prologue layout, and for 
leaf functions the GP will not necessarily be in $28.  Add in the 
difference caused by -mshared and -mplt, and there can be quite a bit of 
variability.

I think it is still technically feasible, but it could be a rather large 
piece of code.  I would note that this problem is similar to the problem 
of generating a stack trace by using code inspection.  It is possible, 
but using real debugging info is far better.

David Daney