[PATCH v3 00/12] Rework READ_ONCE() to improve codegen

[Will Deacon]

Hi everyone,

This is version three of the patches I previously posted for improving
the code generation of READ_ONCE() and moving the minimum GCC version
to 4.8:

RFC: https://lore.kernel.org/lkml/20200110165636.28035-1-will@xxxxxxxxxx
v2:  https://lore.kernel.org/lkml/20200123153341.19947-1-will@xxxxxxxxxx

Although v2 was queued up by Peter in -tip, it was found to break the
build for m68k and sparc32. We fixed m68k during the merge window and
I've since posted patches to fix sparc32 here:

  https://lore.kernel.org/lkml/20200414214011.2699-1-will@xxxxxxxxxx

This series is a refresh on top of 5.7-rc1, the main changes being:

  * Fix another issue where 'const' is assigned to non-const via
    WRITE_ONCE(), this time in the tls code

  * Fix READ_ONCE_NOCHECK() abuse in arm64 checksum code

  * Added Reviewed-bys and Acks from v2

Hopefully this can be considered for 5.8, along with the sparc32 changes.

Cheers,

Will

Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Segher Boessenkool <segher@xxxxxxxxxxxxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Cc: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Peter Oberparleiter <oberpar@xxxxxxxxxxxxx>
Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>

--->8

Will Deacon (12):
  compiler/gcc: Emit build-time warning for GCC prior to version 4.8
  netfilter: Avoid assigning 'const' pointer to non-const pointer
  net: tls: Avoid assigning 'const' pointer to non-const pointer
  fault_inject: Don't rely on "return value" from WRITE_ONCE()
  arm64: csum: Disable KASAN for do_csum()
  READ_ONCE: Simplify implementations of {READ,WRITE}_ONCE()
  READ_ONCE: Enforce atomicity for {READ,WRITE}_ONCE() memory accesses
  READ_ONCE: Drop pointer qualifiers when reading from scalar types
  locking/barriers: Use '__unqual_scalar_typeof' for load-acquire macros
  arm64: barrier: Use '__unqual_scalar_typeof' for acquire/release
    macros
  compiler/gcc: Raise minimum GCC version for kernel builds to 4.8
  gcov: Remove old GCC 3.4 support

 Documentation/process/changes.rst |   2 +-
 arch/arm/crypto/Kconfig           |  12 +-
 arch/arm64/include/asm/barrier.h  |  16 +-
 arch/arm64/lib/csum.c             |  20 +-
 crypto/Kconfig                    |   1 -
 drivers/xen/time.c                |   2 +-
 include/asm-generic/barrier.h     |  16 +-
 include/linux/compiler-gcc.h      |   5 +-
 include/linux/compiler.h          | 129 +++----
 include/linux/compiler_types.h    |  21 ++
 init/Kconfig                      |   5 +-
 kernel/gcov/Kconfig               |  24 --
 kernel/gcov/Makefile              |   3 +-
 kernel/gcov/gcc_3_4.c             | 573 ------------------------------
 lib/fault-inject.c                |   4 +-
 net/netfilter/core.c              |   2 +-
 net/tls/tls_main.c                |   2 +-
 scripts/Kconfig.include           |   6 +
 scripts/gcc-plugins/Kconfig       |   2 +-
 19 files changed, 126 insertions(+), 719 deletions(-)
 delete mode 100644 kernel/gcov/gcc_3_4.c

-- 
2.26.0.110.g2183baf09c-goog