RE: linking problem - mips32 Android

[Matthew Fortune <Matthew dot Fortune at imgtec dot com>]

H.J. Lu <hjl.tools@gmail.com> writes:
> On Mon, Aug 24, 2015 at 8:52 AM, Andrzej Warzynski <andrzej@codeplay.com> wrote:
> >
> > Hello,
> >
> > We've recently came across a weird behavior with ld, and I wanted to
> > check whether this is a known issue and what's the best way to solve it.
> >
> > We're using ld to link position independent binaries (passing the -pie
> > flag) for mips32 devices running Android. The problem is that ld marks
> > such binaries as shared when parsing arguments. This is implemented in
> > the parse_args() function in the lexsup.c file:
> >
> > case OPTION_PIE:
> >      if (config.has_shared)
> >      {
> >          link_info.shared = TRUE;
> >          link_info.pie = TRUE;
> >      }
> >
> > However, having been compiled with -pie does not necessarily imply that
> > it is a shared object, it could be an executable. Indeed, Android
> > requires all binaries to be position independent (i.e. linked with the
> > -pie flag), both shared objects and executables.
> >
> > The above situation is particularly problematic for us, because it
> > prevents the _bfd_mips_elf_size_dynamic_sections() function in the
> > elfxx-mips.c file from adding the DT_MIPS_RLD_MAP structure to the
> > .dynamic section. This is due to the following check on line 9786 in
> > elfxx-mips.c (binutils-2.25.1):
> >
> > if (!info->shared && !MIPS_ELF_ADD_DYNAMIC_ENTRY (info, DT_MIPS_RLD_MAP,
> > 0))
> >
> > This check means that DT_MIPS_RLD_MAP will not be added if the file
> > that's being processed is flagged as shared. The DT_MIPS_RLD_MAP
> > structure is used by debuggers to track loading and unloading of shared
> > objects. The above behavior (i.e. flagging all position independent
> > binaries as shared objects) renders debugging executables for mips32
> > Android impossible.
> >
> > Is it necessary to flag all position independent executables as shared?
> > There's a bunch of easy workarounds, but we're not really sure what
> > would be the optimal solution.
> >
> 
> Please checkout master branch.  It has been changed.

Indeed. The feature you need is DT_MIPS_RLD_MAP_REL and support for
this has been added to master branches of binutils, gdb and glibc.

This is the post for the binutils commit:

https://cygwin.com/ml/binutils/2015-06/msg00264.html

Sorry for missing this the first time you asked about it.

Thanks,
Matthew