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[v2,0/3] jump_label: get rid of NOP patching where possible

Message ID 20220615154142.1574619-1-ardb@kernel.org (mailing list archive)
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Series jump_label: get rid of NOP patching where possible | expand

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Ard Biesheuvel June 15, 2022, 3:41 p.m. UTC 
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.

Changes since v1:
- use a default implementation of arch_jump_label_transform_static()
  instead of an empty macro in patch #3
- fix MIPS with CONFIG_MODULES=n
- add acks from Mark and Peter to patch #3

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mark Rutland <mark.rutland@arm.com>
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         | 19 +++++++++
 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, 38 insertions(+), 145 deletions(-)