[PATCH v4 0/4] Upgrade READ_ONCE() to RCpc acquire on arm64 with LTO

Will Deacon
2020-11-03T12:19:30Z

Hi all,

These patches were previously posted as part of a larger series enabling
architectures to override __READ_ONCE():

v3: https://lore.kernel.org/lkml/20200710165203.31284-1-will@kernel.org/

With the bulk of that merged, the four patches here override READ_ONCE()
so that it gains RCpc acquire semantics on arm64 when LTO is enabled. We
can revisit this as and when the compiler provides a means for us to reason
about the result of dependency-breaking optimisations. In the meantime,
this unblocks LTO for arm64, which I would really like to see merged so
that we can focus on enabling CFI.

I plan to queue these on their own branch in the arm64 tree for 5.11 at
-rc3.

Cheers,

Will

Cc: Kees Cook <keescook@chromium.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org

--->8

Will Deacon (4):
arm64: alternatives: Split up alternative.h
arm64: cpufeatures: Add capability for LDAPR instruction
arm64: alternatives: Remove READ_ONCE() usage during patch operation
arm64: lto: Strengthen READ_ONCE() to acquire when CONFIG_LTO=y

arch/arm64/Kconfig | 3 +
arch/arm64/include/asm/alternative-macros.h | 276 ++++++++++++++++++++
arch/arm64/include/asm/alternative.h | 267 +------------------
arch/arm64/include/asm/cpucaps.h | 3 +-
arch/arm64/include/asm/insn.h | 3 +-
arch/arm64/include/asm/rwonce.h | 63 +++++
arch/arm64/kernel/alternative.c | 7 +-
arch/arm64/kernel/cpufeature.c | 10 +
arch/arm64/kernel/vdso/Makefile | 2 +-
arch/arm64/kernel/vdso32/Makefile | 2 +-
arch/arm64/kernel/vmlinux.lds.S | 2 +-
11 files changed, 364 insertions(+), 274 deletions(-)
create mode 100644 arch/arm64/include/asm/alternative-macros.h
create mode 100644 arch/arm64/include/asm/rwonce.h

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2.29.1.341.ge80a0c044ae-goog