[RFC PATCH 0/9] powerpc: ftrace updates

Naveen N Rao naveen at kernel.org
Sat Dec 9 03:30:39 AEDT 2023

Early RFC.

This series attempts to address couple of issues with the existing 
support for ftrace on powerpc, with a view towards improving performance 
when ftrace is not enabled. See patch 6 for more details.

Patches 7 and 8 implement support for ftrace direct calls, through 
adding support for DYNAMIC_FTRACE_WITH_CALL_OPS.

The first 5 patches are minor cleanups and updates, and can go in 

This series depends on Benjamin Gray's series adding support for 

I have lightly tested this patch set and it looks to be working well. As 
described in patch 6, context_switch microbenchmark shows an improvement 
of ~6% with this series with ftrace disabled. Performance when ftrace is
enabled reduces due to how DYNAMIC_FTRACE_WITH_CALL_OPS works, and due 
to support for direct calls. Some of that can hopefully be improved, if 
this approach is otherwise ok.

- Naveen

Naveen N Rao (8):
  powerpc/ftrace: Fix indentation in ftrace.h
  powerpc/ftrace: Unify 32-bit and 64-bit ftrace entry code
  powerpc/ftrace: Remove nops after the call to ftrace_stub
  powerpc/kprobes: Use ftrace to determine if a probe is at function
  powerpc/ftrace: Update and move function profile instructions
  powerpc/ftrace: Add support for DYNAMIC_FTRACE_WITH_CALL_OPS
  powerpc/ftrace: Add support for DYNAMIC_FTRACE_WITH_DIRECT_CALLS
  samples/ftrace: Add support for ftrace direct samples on powerpc

Sathvika Vasireddy (1):
  powerpc/Kconfig: Select FUNCTION_ALIGNMENT_4B

 arch/powerpc/Kconfig                        |   6 +
 arch/powerpc/Makefile                       |   6 +-
 arch/powerpc/include/asm/code-patching.h    |  15 +-
 arch/powerpc/include/asm/ftrace.h           |  35 ++-
 arch/powerpc/include/asm/linkage.h          |   3 -
 arch/powerpc/kernel/asm-offsets.c           |   7 +
 arch/powerpc/kernel/kprobes.c               |  69 +++++-
 arch/powerpc/kernel/trace/ftrace.c          | 231 ++++++++++++++++----
 arch/powerpc/kernel/trace/ftrace_entry.S    | 182 +++++++++++----
 samples/ftrace/ftrace-direct-modify.c       |  94 +++++++-
 samples/ftrace/ftrace-direct-multi-modify.c | 110 +++++++++-
 samples/ftrace/ftrace-direct-multi.c        |  64 +++++-
 samples/ftrace/ftrace-direct-too.c          |  72 +++++-
 samples/ftrace/ftrace-direct.c              |  61 +++++-
 14 files changed, 845 insertions(+), 110 deletions(-)

base-commit: 9a15ae60f2c9707433b01e55815cd9142be102b2
prerequisite-patch-id: 38d3e705bf2e27cfa5e3ba369a6ded84ba6615c2
prerequisite-patch-id: 609d292e054b2396b603890522a940fa0bdfb6d8
prerequisite-patch-id: 6f7213fb77b1260defbf43be0e47bff9c80054cc
prerequisite-patch-id: f2328625ae2193c3c8e336b154b62030940cece8

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