Needs porting / support in binutils and glibc, and then some target configure magic for GCC.

http://nickclifton.livejournal.com/6612.html has a short summary about how to use it from GCC.

• binutils

  Already passes the ifunc testsuite bits for GAS, but notably for LD (ld/testsuite/ld-ifunc/ifunc.exp), too, but that one contains a bunch of stuff explicitly tailored towards Linux. For example, we get *OS/ABI: UNIX

  • Linux*. (This should be fixed through using ELFOSABI GNU.)

  Most of the executables that the testsuite generates don't actually execute. (Though, this is partly due to the static issue.)

  $ tmpdir/local_prog 
  ifunc working correctly
  $ tmpdir/static_prog 
  Killed
  $ tmpdir/dynamic_prog 
  tmpdir/dynamic_prog: error while loading shared libraries: ./tmpdir/libshared_ifunc.so: ELF file OS ABI invalid
  $ tmpdir/static_nonifunc_prog 
  Killed
  $ tmpdir/test-1
  tmpdir/test-1: error while loading shared libraries: tmpdir/libshared_ifunc.so: ELF file OS ABI invalid
  

• glibc

  • libc variant selection

• GCC

  In gcc/config.gcc, set default_gnu_indirect_function=yes for us, like done for GNU/Linux. See thread starting at id:"CAFULd4YZsAQ6ckFjXtU5-yyv=3tYQwTJOPhU9zmJxFOrnotj8g@mail.gmail.com".