Subject: [PATCH v2 0/2] get rid of GCC __attribute__((optimize)) for BPF

From: Ard Biesheuvel <[email-masked]>
Date: Wed, 28 Oct 2020 18:15:04 +0100

This is a followup to [0]:
[PATCH] bpf: don't rely on GCC __attribute__((optimize)) to disable GCSE[0]

Changes since v1:
- only use -fno-gcse when CONFIG_BPF_JIT_ALWAYS_ON=y and CONFIG_CC_IS_GCC=y
  (but ignore CONFIG_RETPOLINE since we want to avoid GCSE in all cases)
- to avoid potential impact of disabling GCSE on other code, put the
  interpreter in a separate file (patch #2)

Note that patch #1 is intended for backporting, as function scope GCC
optimization attributes are really quite broken.

I don't have a strong opinion on whether the interpreter code should be
split off or not, but it looks like it can be done fairly painlessly,
so it is probably a good idea to do it anyway.

[0] https://lore.kernel.org/bpf/[email-masked]/

Cc: Nick Desaulniers <[email-masked]>
Cc: Arvind Sankar <[email-masked]>
Cc: Randy Dunlap <[email-masked]>
Cc: Josh Poimboeuf <[email-masked]>
Cc: Thomas Gleixner <[email-masked]>
Cc: Alexei Starovoitov <[email-masked]>
Cc: Daniel Borkmann <[email-masked]>
Cc: Peter Zijlstra (Intel) <[email-masked]>
Cc: Geert Uytterhoeven <[email-masked]>
Cc: Kees Cook <[email-masked]>

Ard Biesheuvel (2):
  bpf: don't rely on GCC __attribute__((optimize)) to disable GCSE
  bpf: move interpreter into separate source file

 include/linux/compiler-gcc.h   |   2 -
 include/linux/compiler_types.h |   4 -
 include/linux/filter.h         |   1 +
 kernel/bpf/Makefile            |   7 +-
 kernel/bpf/core.c              | 567 ------------------
 kernel/bpf/interp.c            | 601 ++++++++++++++++++++
 6 files changed, 607 insertions(+), 575 deletions(-)
 create mode 100644 kernel/bpf/interp.c

-- 
2.17.1