[PATCH 0/3] jump_label: get rid of NOP patching where possible

Ard Biesheuvel
2022-06-08T10:45:33Z

The only architecture that actually needs to convert compiler generated
jump label NOP encodings into something else at runtime is MIPS, because
the assembler cannot be trusted to emit a sequence that can be safely
patched into a branch instruction.

All other architectures either do nothing with jump label NOPs at load
time, or patch a perfectly good NOP into a different one, or into the same
one - none of this seems very useful, so let's get rid of it where we
can.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: linux-mips@vger.kernel.org
Cc: linux-s390@vger.kernel.org

Ard Biesheuvel (3):
jump_label: s390: avoid pointless initial NOP patching
jump_label: mips: move module NOP patching into arch code
jump_label: make initial NOP patching the special case

Documentation/staging/static-keys.rst | 3 --
arch/arc/kernel/jump_label.c | 13 -------
arch/arm/kernel/jump_label.c | 6 ---
arch/arm64/kernel/jump_label.c | 11 ------
arch/mips/include/asm/jump_label.h | 2 +
arch/mips/kernel/jump_label.c | 17 ++++++++
arch/mips/kernel/module.c | 5 ++-
arch/parisc/kernel/jump_label.c | 11 ------
arch/riscv/kernel/jump_label.c | 12 ------
arch/s390/include/asm/jump_label.h | 5 +--
arch/s390/kernel/jump_label.c | 28 +++----------
arch/s390/kernel/module.c | 1 -
arch/sparc/kernel/module.c | 3 --
arch/x86/kernel/jump_label.c | 13 -------
arch/x86/kernel/module.c | 3 --
include/linux/jump_label.h | 7 +---
kernel/jump_label.c | 41 ++------------------
17 files changed, 34 insertions(+), 147 deletions(-)

--
2.30.2