[PATCH v2 0/8] Add Kernel Concurrency Sanitizer (KCSAN)

[Marco Elver]

This is the patch-series for the Kernel Concurrency Sanitizer (KCSAN).
KCSAN is a sampling watchpoint-based data-race detector. More details
are included in Documentation/dev-tools/kcsan.rst. This patch-series
only enables KCSAN for x86, but we expect adding support for other
architectures is relatively straightforward (we are aware of
experimental ARM64 and POWER support).

To gather early feedback, we announced KCSAN back in September, and
have integrated the feedback where possible:
http://lkml.kernel.org/r/CANpmjNPJ_bHjfLZCAPV23AXFfiPiyXXqqu72n6TgWzb2Gnu1eA@xxxxxxxxxxxxxx

We want to point out and acknowledge the work surrounding the LKMM,
including several articles that motivate why data-races are dangerous
[1, 2], justifying a data-race detector such as KCSAN.
[1] https://lwn.net/Articles/793253/
[2] https://lwn.net/Articles/799218/

The current list of known upstream fixes for data-races found by KCSAN
can be found here:
https://github.com/google/ktsan/wiki/KCSAN#upstream-fixes-of-data-races-found-by-kcsan

Changelog
---------
v2:
* Elaborate comment about instrumentation calls emitted by compilers.
* Replace kcsan_check_access(.., {true, false}) with
  kcsan_check_{read,write} for improved readability.
* Introduce __atomic_check_{read,write} in atomic-instrumented.h [Suggested by
  Mark Rutland].
* Change bug title of race of unknown origin to just say "data-race in".
* Refine "Key Properties" in kcsan.rst, and mention observed slow-down.
* Add comment about safety of find_watchpoint without user_access_save.
* Remove unnecessary preempt_disable/enable and elaborate on comment why
  we want to disable interrupts and preemptions.
* Use common struct kcsan_ctx in task_struct and for per-CPU interrupt
  contexts [Suggested by Mark Rutland].
* Document x86 build exceptions where no previous above comment
  explained why we cannot instrument.

v1: http://lkml.kernel.org/r/20191016083959.186860-1-elver@xxxxxxxxxx


Marco Elver (8):
  kcsan: Add Kernel Concurrency Sanitizer infrastructure
  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
  asm-generic, kcsan: Add KCSAN instrumentation for bitops
  locking/atomics, kcsan: Add KCSAN instrumentation
  x86, kcsan: Enable KCSAN for x86

 Documentation/dev-tools/kcsan.rst         | 203 ++++++++++
 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                  |   7 +
 arch/x86/kernel/cpu/Makefile              |   3 +
 arch/x86/lib/Makefile                     |   4 +
 arch/x86/mm/Makefile                      |   3 +
 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/asm-generic/bitops-instrumented.h |  18 +
 include/linux/compiler-clang.h            |   9 +
 include/linux/compiler-gcc.h              |   7 +
 include/linux/compiler.h                  |  35 +-
 include/linux/kcsan-checks.h              | 147 ++++++++
 include/linux/kcsan.h                     | 108 ++++++
 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                     |  14 +
 kernel/kcsan/atomic.c                     |  21 ++
 kernel/kcsan/core.c                       | 428 ++++++++++++++++++++++
 kernel/kcsan/debugfs.c                    | 225 ++++++++++++
 kernel/kcsan/encoding.h                   |  94 +++++
 kernel/kcsan/kcsan.c                      |  86 +++++
 kernel/kcsan/kcsan.h                      | 140 +++++++
 kernel/kcsan/report.c                     | 306 ++++++++++++++++
 kernel/kcsan/test.c                       | 117 ++++++
 kernel/sched/Makefile                     |   6 +
 lib/Kconfig.debug                         |   2 +
 lib/Kconfig.kcsan                         |  88 +++++
 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                     |  17 +
 46 files changed, 2428 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.c
 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.c
 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

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2.23.0.866.gb869b98d4c-goog