mbox series

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

Message ID 20201103121721.5166-1-will@kernel.org (mailing list archive)
Headers show
Series Upgrade READ_ONCE() to RCpc acquire on arm64 with LTO | expand

Message

Will Deacon Nov. 3, 2020, 12:17 p.m. UTC 
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

Comments

Will Deacon Nov. 9, 2020, 11:25 p.m. UTC | #1 
On Tue, Nov 03, 2020 at 12:17:17PM +0000, Will Deacon wrote:
> 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.

Now pushed to for-next/lto:

https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=for-next/lto

with Mark's comments addressed.

Will