[Bug build/29456] missing DT_HASH section in shared objects

["adhemerval.zanella at linaro dot org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=29456

--- Comment #7 from Adhemerval Zanella <adhemerval.zanella at linaro dot org> ---
(In reply to Arkadiusz Hiler from comment #5)
> (In reply to Florian Weimer from comment #3)
> > Distributions configure or patch GCC to pass --hash-style=gnu to the linker
> > by default. The linker default does not matter.
> 
> Thanks, that explains a few things. My gcc -v indeed claims that:
> 
>     Configured with: /build/gcc/src/gcc/configure ...
> --with-linker-hash-style=gnu ...
> 
> According to gcc/docs/install.texi the default is sysv but after browsing
> the code for a bit it looks like if `--with-linker-hash-style` is not
> specified no `--hash-style` is passed to the linker so it would depend on
> linker's defaults.
> 
> Do you know why distros do this? Looking at package history it seems like an
> artifact from the times where both was a bit problematic. There used to be
> some custom patches for that years ago.
> 
> 
> (In reply to Adhemerval Zanella from comment #4)
> > > This breaks all the games running via Proton that are using EAC.
> > 
> > What EAC is doing exactly that requires a DT_HASH on glibc? What happens if
> > you mix DT_HASH and DT_GNU_HASH shared objects (for instance shared
> > libraries with only one option)? It does seem a shortcoming from EAC,
> > although I am not sure what exactly it is trying to enforce here.
> 
> I can only guess but probably to look up some symbols in multiple ways to
> assure no hooking has occurred.
> 
> It seems to require it only for the glibc DSOs as they were shipping with
> DT_HASH for years, even on distros that default to gnu, and this is an
> unexpected change.

Right, however, I am not sure this characterize as an ABI break since the
symbol lookup information would be indeed provided (albeit in a different
format). And it should be transparent to most applications as well since symbol
resolution is done by the loader itself.

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