Re: [RFC PATCH 0/2] elfutils: don't use dlopen() for libebl modules

[Omar Sandoval <osandov at osandov dot com>]

On Wed, Jul 03, 2019 at 05:39:53PM -0400, Frank Ch. Eigler wrote:
> Hi - 
> 
> > This is actually with dynamically linked binaries -- the size increase
> > is because we link libebl.a directly into all of the binaries in
> > addition to libdw.so:
> > 
> > objdump_LDADD  = $(libasm) $(libebl) $(libdw) $(libelf) $(libeu) $(argp_LDADD
> 
> Is there some reason to keep doing that?
> 
> - FChE

Yes:

$ make -C src
make: Entering directory '/home/osandov/dev/elfutils/src'
  CCLD     objdump
/bin/ld: objdump.o: in function `show_relocs_x':
/home/osandov/dev/elfutils/src/objdump.c:352: undefined reference to `ebl_reloc_type_name'
/bin/ld: objdump.o: in function `handle_elf':
/home/osandov/dev/elfutils/src/objdump.c:755: undefined reference to `ebl_openbackend'
/bin/ld: /home/osandov/dev/elfutils/src/objdump.c:757: undefined reference to `ebl_backend_name'
/bin/ld: /home/osandov/dev/elfutils/src/objdump.c:788: undefined reference to `ebl_closebackend'
collect2: error: ld returned 1 exit status
make: *** [Makefile:624: objdump] Error 1
make: Leaving directory '/home/osandov/dev/elfutils/src'

Some of the binaries use libebl, and although libebl is linked into libdw.so,
the libebl symbols are not exported by libdw. So, libebl is linked in
statically for the binaries.

This is why I suggested exporting those symbols from libdw.so. (I also
considered adding a libebl.so, but that would have a circular dependency with
libdw.so, so they might as well be combined).