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

Ard Biesheuvel
2020-10-29T01:21:18Z

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/20201027205723.12514-1-ardb@kernel.org/

Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Kees Cook <keescook@chromium.org>

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