[PATCH 0/4] Add support for compiling with -ffunction-sections -fdata-sections

Tim Abbott
2009-03-24T05:31:38Z

Hi Linus,

I'd like to see this patch series merged for 2.6.30. It applies on
top of your current master (aka v2.6.29). Patch 1/4 would benefit
from special treatment during the merge window, since it makes many
small changes in lots of files, and thus is likely to conflict with
other changes; the other patches are fairly small.

The purpose of this patch series is to make it possible to build the
kernel with "gcc -ffunction-sections -fdata-sections". There are two
major applications for this functionality: decreasing vmlinux image
size with --gc-sections, and Ksplice.

The original motivation for this functionality was to allow using the
linker's unused section garbage collection support (ld --gc-sections)
in order to get a smaller vmlinux image for embedded systems. People
have been developing patches for supporting building the kernel with
-ffunction-sections -fdata-sections for this purpose for a few years
now (e.g. [1]). The most recent previous set of patches for
--gc-sections was by Denys Vlasenko, and saved 10% on vmlinux size
with CONFIG_MODULES=n and 1% with CONFIG_MODULES=y [2,3,4]. The
primary source of complexity in the various patch series for doing
section garbage collection has been in the patches adding support for
compiling the kernel with -ffunction-sections -fdata-sections, so
merging this patch series should be a big step towards those
significant savings in kernel image size.

[1] <http://lkml.org/lkml/2006/6/4/169>
[2] <http://lkml.org/lkml/2007/9/5/90>
[3] <http://lkml.org/lkml/2007/9/7/110>
[4] <http://lkml.org/lkml/2008/7/1/499>

Support for building the kernel with -ffunction-sections
-fdata-sections is the only significant prerequisite change currently
required by Ksplice. Ksplice is a system for updating the Linux
kernel without rebooting [5].

[5] <http://lkml.org/lkml/2009/2/24/362> is the latest version of the
Ksplice patch series

Patches 1/4, 2/4, and 3/4 are independent of each other, but
all three are prerequisites for patch 4/4.

--

Anders Kaseorg (1):
modpost: Check the section flags, not name, to catch missing
"ax"/"aw"

Denys Vlasenko (1):
modpost: support objects with more than 64k sections

Tim Abbott (1):
Make section names compatible with -ffunction-sections
-fdata-sections

Waseem Daher (1):
x86: Add an option to compile with -ffunction-sections
-fdata-sections

Documentation/mutex-design.txt | 4 +-
Makefile | 4 +
arch/alpha/kernel/head.S | 2 +-
arch/alpha/kernel/init_task.c | 2 +-
arch/alpha/kernel/vmlinux.lds.S | 14 ++--
arch/arm/kernel/head-nommu.S | 2 +-
arch/arm/kernel/head.S | 2 +-
arch/arm/kernel/init_task.c | 2 +-
arch/arm/kernel/vmlinux.lds.S | 14 ++--
arch/arm/mm/proc-v6.S | 2 +-
arch/arm/mm/proc-v7.S | 2 +-
arch/arm/mm/tlb-v6.S | 2 +-
arch/arm/mm/tlb-v7.S | 2 +-
arch/avr32/kernel/init_task.c | 2 +-
arch/avr32/kernel/vmlinux.lds.S | 6 +-
arch/avr32/mm/init.c | 2 +-
arch/blackfin/kernel/vmlinux.lds.S | 2 +-
arch/cris/kernel/process.c | 2 +-
arch/cris/kernel/vmlinux.lds.S | 2 +-
arch/frv/kernel/break.S | 4 +-
arch/frv/kernel/entry.S | 2 +-
arch/frv/kernel/head-mmu-fr451.S | 2 +-
arch/frv/kernel/head-uc-fr401.S | 2 +-
arch/frv/kernel/head-uc-fr451.S | 2 +-
arch/frv/kernel/head-uc-fr555.S | 2 +-
arch/frv/kernel/head.S | 4 +-
arch/frv/kernel/init_task.c | 2 +-
arch/frv/kernel/vmlinux.lds.S | 18 ++--
arch/frv/mm/tlb-miss.S | 2 +-
arch/h8300/boot/compressed/head.S | 2 +-
arch/h8300/boot/compressed/vmlinux.lds | 2 +-
arch/h8300/kernel/init_task.c | 2 +-
arch/h8300/kernel/vmlinux.lds.S | 2 +-
arch/ia64/include/asm/asmmacro.h | 12 +-
arch/ia64/include/asm/cache.h | 2 +-
arch/ia64/include/asm/percpu.h | 2 +-
arch/ia64/kernel/Makefile | 2 +-
arch/ia64/kernel/gate-data.S | 2 +-
arch/ia64/kernel/gate.S | 8 +-
arch/ia64/kernel/gate.lds.S | 10 +-
arch/ia64/kernel/head.S | 2 +-
arch/ia64/kernel/init_task.c | 4 +-
arch/ia64/kernel/ivt.S | 2 +-
arch/ia64/kernel/minstate.h | 4 +-
arch/ia64/kernel/paravirtentry.S | 2 +-
arch/ia64/kernel/vmlinux.lds.S | 48 ++++----
arch/ia64/kvm/vmm_ivt.S | 2 +-
arch/ia64/xen/xensetup.S | 2 +-
arch/m32r/kernel/head.S | 2 +-
arch/m32r/kernel/init_task.c | 2 +-
arch/m32r/kernel/vmlinux.lds.S | 8 +-
arch/m68k/kernel/head.S | 2 +-
arch/m68k/kernel/process.c | 2 +-
arch/m68k/kernel/sun3-head.S | 2 +-
arch/m68k/kernel/vmlinux-std.lds | 6 +-
arch/m68k/kernel/vmlinux-sun3.lds | 4 +-
arch/m68knommu/kernel/init_task.c | 2 +-
arch/m68knommu/kernel/vmlinux.lds.S | 6 +-
arch/m68knommu/platform/68360/head-ram.S | 2 +-
arch/m68knommu/platform/68360/head-rom.S | 2 +-
arch/mips/kernel/init_task.c | 2 +-
arch/mips/kernel/vmlinux.lds.S | 8 +-
arch/mips/lasat/image/head.S | 2 +-
arch/mips/lasat/image/romscript.normal | 2 +-
arch/mn10300/kernel/head.S | 2 +-
arch/mn10300/kernel/init_task.c | 2 +-
arch/mn10300/kernel/vmlinux.lds.S | 16 ++--
arch/parisc/include/asm/cache.h | 2 +-
arch/parisc/include/asm/system.h | 2 +-
arch/parisc/kernel/head.S | 2 +-
arch/parisc/kernel/init_task.c | 8 +-
arch/parisc/kernel/vmlinux.lds.S | 26 +++---
arch/powerpc/include/asm/cache.h | 2 +-
arch/powerpc/include/asm/page_64.h | 2 +-
arch/powerpc/include/asm/ppc_asm.h | 4 +-
arch/powerpc/kernel/head_32.S | 2 +-
arch/powerpc/kernel/head_40x.S | 2 +-
arch/powerpc/kernel/head_44x.S | 2 +-
arch/powerpc/kernel/head_8xx.S | 2 +-
arch/powerpc/kernel/head_fsl_booke.S | 2 +-
arch/powerpc/kernel/init_task.c | 2 +-
arch/powerpc/kernel/machine_kexec_64.c | 2 +-
arch/powerpc/kernel/vdso.c | 2 +-
arch/powerpc/kernel/vdso32/vdso32_wrapper.S | 2 +-
arch/powerpc/kernel/vdso64/vdso64_wrapper.S | 2 +-
arch/powerpc/kernel/vmlinux.lds.S | 28 +++---
arch/s390/include/asm/cache.h | 2 +-
arch/s390/kernel/head.S | 2 +-
arch/s390/kernel/init_task.c | 2 +-
arch/s390/kernel/vdso.c | 2 +-
arch/s390/kernel/vdso32/vdso32_wrapper.S | 2 +-
arch/s390/kernel/vdso64/vdso64_wrapper.S | 2 +-
arch/s390/kernel/vmlinux.lds.S | 20 ++--
arch/sh/include/asm/cache.h | 2 +-
arch/sh/kernel/cpu/sh5/entry.S | 4 +-
arch/sh/kernel/head_32.S | 2 +-
arch/sh/kernel/head_64.S | 2 +-
arch/sh/kernel/init_task.c | 2 +-
arch/sh/kernel/irq.c | 4 +-
arch/sh/kernel/vmlinux_32.lds.S | 14 ++--
arch/sh/kernel/vmlinux_64.lds.S | 14 ++--
arch/sparc/boot/btfixupprep.c | 4 +-
arch/sparc/include/asm/cache.h | 2 +-
arch/sparc/kernel/head_32.S | 4 +-
arch/sparc/kernel/head_64.S | 2 +-
arch/sparc/kernel/init_task.c | 2 +-
arch/sparc/kernel/vmlinux.lds.S | 14 ++--
arch/um/include/asm/common.lds.S | 4 +-
arch/um/kernel/dyn.lds.S | 4 +-
arch/um/kernel/init_task.c | 4 +-
arch/um/kernel/uml.lds.S | 4 +-
arch/x86/Kconfig | 1 +
arch/x86/boot/compressed/head_32.S | 2 +-
arch/x86/boot/compressed/head_64.S | 2 +-
arch/x86/boot/compressed/relocs.c | 2 +-
arch/x86/boot/compressed/vmlinux.scr | 2 +-
arch/x86/boot/compressed/vmlinux_32.lds | 14 ++-
arch/x86/boot/compressed/vmlinux_64.lds | 10 +-
arch/x86/include/asm/cache.h | 4 +-
arch/x86/kernel/acpi/wakeup_32.S | 2 +-
arch/x86/kernel/head_32.S | 6 +-
arch/x86/kernel/head_64.S | 4 +-
arch/x86/kernel/init_task.c | 4 +-
arch/x86/kernel/traps.c | 2 +-
arch/x86/kernel/vmlinux_32.lds.S | 37 ++++---
arch/x86/kernel/vmlinux_64.lds.S | 27 +++---
arch/xtensa/kernel/head.S | 2 +-
arch/xtensa/kernel/init_task.c | 2 +-
arch/xtensa/kernel/vmlinux.lds.S | 6 +-
include/asm-frv/init.h | 8 +-
include/asm-generic/vmlinux.lds.h | 19 ++--
include/linux/cache.h | 2 +-
include/linux/init.h | 8 +-
include/linux/linkage.h | 4 +-
include/linux/percpu.h | 10 +-
include/linux/spinlock.h | 2 +-
kernel/module.c | 2 +-
lib/Kconfig.debug | 18 +++
scripts/mod/file2alias.c | 6 +-
scripts/mod/modpost.c | 155 ++++++++++++++++-----------
scripts/mod/modpost.h | 43 ++++++++
scripts/recordmcount.pl | 6 +-
142 files changed, 515 insertions(+), 409 deletions(-)