How to stop --gc-sections nukeing all sections?

[Ian Lance Taylor]

   Date: Wed, 5 Apr 2000 13:47:19 +1000 (EST)
   From: greyham@research.canon.com.au (Graham Stoney)

   I'm currently using --gc-sections to eliminate dead code from the Linux kernel
   for use on embedded systems. I think I just resolved my last problem, which
   was that the linker wasn't outputing _any_ data in the output sections,
   presumably because there are no external references to any section. Hence, it
   garbage collected _everything_, leaving no output section data, and no kernel
   :-(.

   My hack workaround is to add "-u _start" to LINKFLAGS, which is enough to
   stop ld from discarding everything. However, I'm wondering what the approved
   method is to prevent --gc-sections from simply discarding everything?

   Is there something I can add to the linker command file to achieve this?
   It would be nice to be able to turn --gc-sections on and off without having
   to add other stuff to LINKFLAGS. I notice the binutils ldscripts don't suffer
   from this problem, but I can't see the magic that makes it work.

The binutils ldscripts typically have an implicit -u option from the
ENTRY command.

They also the KEEP command to retain special sections, such as those
holding initialization code for global constructors.

Ian