[GIT RFC PULL kcsan] KCSAN commits for 5.5

[Paul E. McKenney]

Hello, Ingo,

This pull request contains base kernel concurrency sanitizer
(KCSAN) enablement for x86, courtesy of Marco Elver.  KCSAN is a
sampling watchpoint-based data-race detector, and is documented in
Documentation/dev-tools/kcsan.rst.  KCSAN was announced in September,
and much feedback has since been incorporated:

http://lkml.kernel.org/r/CANpmjNPJ_bHjfLZCAPV23AXFfiPiyXXqqu72n6TgWzb2Gnu1eA@xxxxxxxxxxxxxx

The data races located thus far have resulted in a number of fixes:

https://github.com/google/ktsan/wiki/KCSAN#upstream-fixes-of-data-races-found-by-kcsan

Additional information may be found here:

https://lore.kernel.org/lkml/20191114180303.66955-1-elver@xxxxxxxxxx/

This has been subject to kbuild test robot and -next testing.  The
-next testing located a Kconfig conflict called out here:

https://lore.kernel.org/lkml/20191119183042.5839ef00@xxxxxxxxxxxxxxxx/

Marco is satisfied with Stephen's resolution, and it looks good to me
as well.

The following changes since commit 31f4f5b495a62c9a8b15b1c3581acd5efeb9af8c:

  Linux 5.4-rc7 (2019-11-10 16:17:15 -0800)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git for-mingo

for you to fetch changes up to 40d04110f87940b6a03bf0aa19cd29e84f465f20:

  x86, kcsan: Enable KCSAN for x86 (2019-11-16 07:23:16 -0800)

----------------------------------------------------------------
Marco Elver (9):
      kcsan: Add Kernel Concurrency Sanitizer infrastructure
      include/linux/compiler.h: Introduce data_race(expr) macro
      kcsan: Add Documentation entry in dev-tools
      objtool, kcsan: Add KCSAN runtime functions to whitelist
      build, kcsan: Add KCSAN build exceptions
      seqlock, kcsan: Add annotations for KCSAN
      seqlock: Require WRITE_ONCE surrounding raw_seqcount_barrier
      locking/atomics, kcsan: Add KCSAN instrumentation
      x86, kcsan: Enable KCSAN for x86

 Documentation/dev-tools/index.rst         |   1 +
 Documentation/dev-tools/kcsan.rst         | 256 ++++++++++++
 MAINTAINERS                               |  11 +
 Makefile                                  |   3 +-
 arch/x86/Kconfig                          |   1 +
 arch/x86/boot/Makefile                    |   2 +
 arch/x86/boot/compressed/Makefile         |   2 +
 arch/x86/entry/vdso/Makefile              |   3 +
 arch/x86/include/asm/bitops.h             |   6 +-
 arch/x86/kernel/Makefile                  |   4 +
 arch/x86/kernel/cpu/Makefile              |   3 +
 arch/x86/lib/Makefile                     |   4 +
 arch/x86/mm/Makefile                      |   4 +
 arch/x86/purgatory/Makefile               |   2 +
 arch/x86/realmode/Makefile                |   3 +
 arch/x86/realmode/rm/Makefile             |   3 +
 drivers/firmware/efi/libstub/Makefile     |   2 +
 include/asm-generic/atomic-instrumented.h | 393 ++++++++++---------
 include/linux/compiler-clang.h            |   9 +
 include/linux/compiler-gcc.h              |   7 +
 include/linux/compiler.h                  |  57 ++-
 include/linux/kcsan-checks.h              |  97 +++++
 include/linux/kcsan.h                     | 115 ++++++
 include/linux/sched.h                     |   4 +
 include/linux/seqlock.h                   |  51 ++-
 init/init_task.c                          |   8 +
 init/main.c                               |   2 +
 kernel/Makefile                           |   6 +
 kernel/kcsan/Makefile                     |  11 +
 kernel/kcsan/atomic.h                     |  27 ++
 kernel/kcsan/core.c                       | 626 ++++++++++++++++++++++++++++++
 kernel/kcsan/debugfs.c                    | 275 +++++++++++++
 kernel/kcsan/encoding.h                   |  94 +++++
 kernel/kcsan/kcsan.h                      | 108 ++++++
 kernel/kcsan/report.c                     | 320 +++++++++++++++
 kernel/kcsan/test.c                       | 121 ++++++
 kernel/sched/Makefile                     |   6 +
 lib/Kconfig.debug                         |   2 +
 lib/Kconfig.kcsan                         | 118 ++++++
 lib/Makefile                              |   3 +
 mm/Makefile                               |   8 +
 scripts/Makefile.kcsan                    |   6 +
 scripts/Makefile.lib                      |  10 +
 scripts/atomic/gen-atomic-instrumented.sh |  17 +-
 tools/objtool/check.c                     |  18 +
 45 files changed, 2623 insertions(+), 206 deletions(-)
 create mode 100644 Documentation/dev-tools/kcsan.rst
 create mode 100644 include/linux/kcsan-checks.h
 create mode 100644 include/linux/kcsan.h
 create mode 100644 kernel/kcsan/Makefile
 create mode 100644 kernel/kcsan/atomic.h
 create mode 100644 kernel/kcsan/core.c
 create mode 100644 kernel/kcsan/debugfs.c
 create mode 100644 kernel/kcsan/encoding.h
 create mode 100644 kernel/kcsan/kcsan.h
 create mode 100644 kernel/kcsan/report.c
 create mode 100644 kernel/kcsan/test.c
 create mode 100644 lib/Kconfig.kcsan
 create mode 100644 scripts/Makefile.kcsan