Re: Pending fixes for all-ABIs builds

[Joseph Myers <joseph@codesourcery.com>]

On Wed, 9 Nov 2016, Florian Weimer wrote:

> On 11/09/2016 12:21 AM, Joseph Myers wrote:
> > On Tue, 8 Nov 2016, Florian Weimer wrote:
> > 
> > > But there's one pre-existing issue I've been wondering about for a while
> > > (along with the s390 maintainers): I don't understand why we have PLT
> > > references to malloc & friends in ld.so.  The malloc implementation there
> > > is
> > > not compliant with the C requirements.  Why is it exported, and why do we
> > > use
> > > GOT indirection to call it?
> > 
> > My understanding is that it's meant to be interposable by a user-provided
> > malloc implementation.  See
> > <https://sourceware.org/ml/libc-alpha/2014-01/msg00719.html>, item 3.
> 
> Does this mean the dynamic linker starts with it's GOT pointer as NULL,
> initializes that to point it to the malloc in elf/dl-minimal.c, and then, once
> libc.so.6 is relocated updates its GOT pointer to point to the malloc in
> libc.so.6?

I don't know the details (beyond what Roland explained, that early 
allocations use ld.so's own malloc, but after interposition none of the 
early allocations should ever be realloced or freed).

-- 
Joseph S. Myers
joseph@codesourcery.com