MIPS: Move signal return trampolines off the stack.

This patch set (against 2.6.29.1) creates a vdso and moves the signal trampolines to it from their previous home on the stack.

Tested with a 64-bit kernel on a Cavium Octeon cn3860 where I have the following results from lmbench2:

Before:
n64 - Signal handler overhead: 14.517 microseconds n32 - Signal handler overhead: 14.497 microseconds o32 - Signal handler overhead: 16.637 microseconds

After:

n64 - Signal handler overhead: 7.935 microseconds
n32 - Signal handler overhead: 7.334 microseconds
o32 - Signal handler overhead: 8.628 microseconds

Comments encourged.

I will reply with two patches.

David Daney (2):
MIPS: Preliminary vdso.
MIPS: Move signal trampolines off of the stack.

arch/mips/include/asm/abi.h         |    6 +-
arch/mips/include/asm/elf.h         |    4 +
arch/mips/include/asm/mmu.h         |    5 +-
arch/mips/include/asm/mmu_context.h |    2 +-
arch/mips/include/asm/processor.h   |    5 +-
arch/mips/include/asm/vdso.h        |   29 ++++++++++
arch/mips/kernel/Makefile           |    2 +-
arch/mips/kernel/signal-common.h    |    5 --
arch/mips/kernel/signal.c           |   86 ++++++----------------------
arch/mips/kernel/signal32.c         |   55 +++++--------------
arch/mips/kernel/signal_n32.c       |   26 ++-------
arch/mips/kernel/syscall.c          |    2 +-
arch/mips/kernel/vdso.c             |  104 +++++++++++++++++++++++++++++++++++
13 files changed, 190 insertions(+), 141 deletions(-)

create mode 100644 arch/mips/include/asm/vdso.h
create mode 100644 arch/mips/kernel/vdso.c