Re: [PATCH 0/7] kvx: New port.

[Paul Iannetta <piannetta@kalrayinc.com>]

Hi Michael,
On Wed, Jul 26, 2023 at 01:32:56PM +0000, Michael Matz wrote:
> Hello,
> 
> On Wed, 26 Jul 2023, Paul Iannetta via Binutils wrote:
> 
> > > Most of the remaining failures appear to be due to this error:
> > > 
> > >  error: PHDR segment not covered by LOAD segment
> > > 
> > > Which I am guessing is due to some kind of issue with the built in linker script
> > > for the KVX target.  Although I am not sure exactly what the issue might be.
> > > 
> > This one is due to the fact that we do not generate a PHDR at all
> > since we only support a very primitive form of dynamic loading (only
> > through calls to dlopen/dlsym), we do not need a PHDR.
> 
> You are using the ELF file format right?  In the gABI a program header 
> table is actually non-optional for executables and shared libs.  
> Obviously a psABI can do mostly whatever it likes, but not having PHDRs is 
> _very_ unusual.  They aren't specific to dynamic linking: after all, even 
> static executables need to be loaded somewhere, by kernel or boot loader 
> or ROM or $othermagic, and the program headers describe what and where to 
> load.  So, you really might want to reconsider.  At least one PT_LOAD 
> segment covering the whole file would be good.

I was not very clear sorry.  We have actually have 2 main usages of ELF
files:
  - one for bare-metal programs -- a program is linked with a bare-metal
OS into a final standalone free standing executable ELF file which
contains an OS, a libc and the userland program.  Those bare-metal
programs can use a dlopen/dlsym-like API to load ELF blobs which have
been deposed in the DDR by some other means. In that case, we don't
need a PHDR, even for the ELF blobs which are dynamically loaded, the
information in the ELF header are enough since we do not support PIE
in this mode and the information in the PHDR is mostly useful for the
dynamic loader.

 - one for linux programs.  In that case, all exec/shared libs have a
   PHDR, and iirc we follow the gABI.

When I was writing the previous mail, I had the first case in my head,
which is indeed a pretty unusual scenario.

Regards,
Paul