Re: PIE binaries are no longer mapped below 4 GiB on ppc64le

["Michal Suchánek" <msuchanek@suse.de>]

On Wed, 31 Oct 2018 18:20:56 +0100
Florian Weimer <fweimer@redhat.com> wrote:

> We tried to use Go to build PIE binaries, and while the Go toolchain
> is definitely not ready (it produces text relocations and problematic
> relocations in general), it exposed what could be an accidental
> userspace ABI change.
> 
> With our 4.10-derived kernel, PIE binaries are mapped below 4 GiB, so
> relocations like R_PPC64_ADDR16_HA work:
> 
...

> There are fewer mappings because the loader detects a relocation
> overflow and aborts (“error while loading shared libraries:
> R_PPC64_ADDR16_HA reloc at 0x0000000120f0983c for symbol `' out of
> range”), so I had to recover the mappings externally.  Disabling ASLR
> does not help.
> 
...
> 
> And it needs to be built with:
> 
>   go build -ldflags=-extldflags=-pie extld.go
> 
> I'm not entirely sure what to make of this, but I'm worried that this
> could be a regression that matters to userspace.

I encountered the same when trying to build go on ppc64le. I am not
familiar with the internals so I just let it be.

It does not seem to matter to any other userspace. Maybe it would be
good idea to generate 64bit relocations on 64bit targets?

Thanks

Michal