Hi Tim, Tim, folks,

Update on -ffunction-sections status:

I re-tested linux-2.6.35-rc4 today.

Most of work needed for -ffunction-sections -fdata-sections
is already in this kernel. This mail explains what is
still missing.

In order to have a working kernel with this make invocation:

	make KCFLAGS="-ffunction-sections -fdata-sections"

linux-2.6.35-rc4 needs three patches:

* modpost fix for 64k+ sections: linux-2.6.35-rc4-fs.modpost.patch
  This patch is in -mm, it still not reach mainline...

* fix for kernel linker stripts: linux-2.6.35-rc4-fs.fix-kernel-linker-scripts.patch
  It makes _all_ linker scripts -ffunction/data-sections safe via:
  -       *(.data)
  +       *(.data .data.*)
  
* fix for module linker script: linux-2.6.35-rc4-fs.fix-ko-module-linker-script.patch
  Prevents kernel modules from having unnecessarily many
  sections and thus prevents module size growth.


Then, in order to also garbage-collect the sections, I added

LDFLAGS_vmlinux += --gc-sections

in top-level Makefile.

This requires the additional patch (linux-2.6.35-rc4-fsgs.patch)
which adds KEEP(section) directives to kernel linker stripts.
Otherwise, linker will discard some crucial sections.


All four patches are attached.

I am sending this email from the machine which runs the kernel
built with -ffunction-sections -fdata-sections --gc-sections.

-- 
vda