----- Original Message -----
From: "Daniel Jacobowitz" <dan@xxxxxxxxxx>
To: "Bradley D. LaRonde" <brad@xxxxxxxxxxx>
Cc: "Richard Sandiford" <rsandifo@xxxxxxxxxx>; <uclibc@xxxxxxxxxx>;
<linux-mips@xxxxxxxxxxxxxx>
Sent: Tuesday, May 11, 2004 10:03 AM
Subject: Re: uclibc mips ld.so and undefined symbols with nonzero symbol
table entry st_value
> On Mon, May 10, 2004 at 11:39:41PM -0400, Bradley D. LaRonde wrote:
> > ----- Original Message -----
> > From: "Richard Sandiford" <rsandifo@xxxxxxxxxx>
> > To: "Bradley D. LaRonde" <brad@xxxxxxxxxxx>
> > Cc: <uclibc@xxxxxxxxxx>; <linux-mips@xxxxxxxxxxxxxx>
> > Sent: Monday, May 10, 2004 4:41 PM
> > Subject: Re: uclibc mips ld.so and undefined symbols with nonzero symbol
> > table entry st_value
> >
> >
> > > "Bradley D. LaRonde" <brad@xxxxxxxxxxx> writes:
> > > > I read this in the spec:
> > > >
> > > > All externally visible symbols, both defined and undefined,
> > > > must be hashed into the hash table.
> > > >
> > > > Should libpthread's malloc stub be added to the hash table?
> > >
> > > Yes.
> > >
> > > > I guess not, but I think that might be happening (haven't verified),
> > > > and libdl finding it in there and thinking it is the real deal, not
> > > > realizing it is just a stub.
> > >
> > > If you have an undefined function symbol with st_value != 0, then
> > > that st_value must be for a stub. That's how the loader can (and is
> > > supposed to) tell the difference.
> > >
> > > It's probably a good idea to look at how glibc handles this.
> >
> > uClibc/ldso/ldso/mips/elfinterp.c around line 288 looks like this:
> >
> >
> > /* Relocate the global GOT entries for the object */
> > while(i--) {
> > if (sym->st_shndx == SHN_UNDEF) {
> > if (ELF32_ST_TYPE(sym->st_info) == STT_FUNC && sym->st_value)
> > *got_entry = sym->st_value + (unsigned long) tpnt->loadaddr;
> > else {
> > *got_entry = (unsigned long) _dl_find_hash(strtab +
> > sym->st_name, tpnt->symbol_scope, ELF_RTYPE_CLASS_COPY);
> > }
> > }
> >
> >
> > If I change that ELF_RTYPE_CLASS_COPY to ELF_RTYPE_CLASS_PLT to tell
> > _dl_find_hash to ignore stubs when resolving undefined functions without
> > stubs, the dlopen tests all pass. dlopen gets a pointer to the libc.so
> > malloc instead of a pointer to the libpthread malloc stub. Yay! :-)
> >
> > Does that look like the correct fix?
>
> Probably, since MIPS doesn't have a copy reloc.
How about the other copy reloc right below there:
else if (sym->st_shndx == SHN_COMMON) {
*got_entry = (unsigned long) _dl_find_hash(strtab +
sym->st_name, tpnt->symbol_scope, ELF_RTYPE_CLASS_COPY);
}
?
Regards,
Brad
