[Bug ld/31795] ld.bfd makes ELFs of type ET_EXEC for static PIEs when load address is non-0

[mintsuki at protonmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31795

--- Comment #48 from mintsuki <mintsuki at protonmail dot com> ---
(In reply to H.J. Lu from comment #47)
> (In reply to mintsuki from comment #46)
> g.
> > > 
> > > Opt-in to ET_EXEC will be wrong.
> > 
> > Why will it be wrong? What if someone (me) wants to make a PIE that loads at
> 
> It is wrong because -Ttext-segment=0x600000000000 no longer works.
> 
> > a minimum at the specified address, but can be relocated above it? Currently
> > ld makes this impossible by simply checking the ELF type, forcing my ELF
> > loader to additionally check for the presence of the DF_1_PIE flag to decide
> > whether an ELF file is relocatable or not...
> > 
> > ...but Linux doesn't do that, apparently, but instead forces the load
> > address to be the one specified, due to the ELF type being ET_EXEC.
> > 
> > Earlier you said I should check DF_1_PIE to determine relocatability... so
> 
> No, that was not what I said.  DF_1_PIE can be used to determine if a binary
> is PIE.

Okay, then how can I make a *relocatable* aka ET_DYN (?) ELF file which is PIE
and has a non-0 text segment load address using ld? This is, as far as my
knowledge goes, *impossible* using GNU ld.bfd. Why?

I can still make an ET_DYN ELF using -shared instead of -pie, but then I have
to build using -fPIC rather than -fPIE, as far as I understand. And in any case
I don't understand why the limitation.

> 
> > which one is it? If I check for DF_1_PIE then I am not following the same
> > behaviour as the Linux ELF loader, which means that I either break from
> > Linux's behaviour, or I follow it, but that means that ld will never allow
> > me to make an ET_DYN PIE with a non-0 load address.

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