[PATCH v4 0/7] powerpc: Add KCSAN Support

[Rohan McLure]

Add Kernel Concurrency Sanitiser support for PPC64. Doing so involves
exclusion of a number of compilation units from instrumentation, as was
done with KASAN.

KCSAN uses watchpoints on memory accesses to enforce the semantics of
the Linux kernel memory model, notifying the user of observed data races
which have not been declared to be intended in source through the
data_race() macro, in order to remove false positives.

A number of such race conditions are identified. This patch series
provides support for the instrumentation, with bug fixes as well as
removal of false positives to be issued in future patches.

As of v4, provide stubs for __atomic_* builtins for 8-byte values
for 32-bit systems without toolchain support. This generalises xtensa's
stubs, and causes xtensa to use generic implementation.

v3: Restrict support to PPC64 as kcsan code expects support for
__atomic* builtins for 64-bit atomic types.
Link: https://lore.kernel.org/linuxppc-dev/449b9d60-18f6-ebf3-9878-ae54a61d1e49@csgroup.eu/

v2: Implement __smp_mb() in terms of __mb() to avoid multiple calls to
kcsan_mb().
Link: https://lore.kernel.org/linuxppc-dev/20230201043438.1301212-4-rmclure@linux.ibm.com/

v1: https://lore.kernel.org/linuxppc-dev/20230131234859.1275125-1-rmclure@linux.ibm.com/

Rohan McLure (7):
  kcsan: Add atomic builtin stubs for 32-bit systems
  xtensa: kcsan: Remove kcsan stubs for atomic builtins
  powerpc: kcsan: Add exclusions from instrumentation
  powerpc: kcsan: Exclude udelay to prevent recursive instrumentation
  powerpc: kcsan: Memory barriers semantics
  powerpc: kcsan: Prevent recursive instrumentation with IRQ
    save/restores
  powerpc: kcsan: Add KCSAN Support

 arch/powerpc/Kconfig                          |  1 +
 arch/powerpc/include/asm/barrier.h            | 12 ++++-----
 arch/powerpc/kernel/Makefile                  | 10 +++++++
 arch/powerpc/kernel/irq_64.c                  |  6 ++---
 arch/powerpc/kernel/time.c                    |  4 +--
 arch/powerpc/kernel/trace/Makefile            |  1 +
 arch/powerpc/kernel/vdso/Makefile             |  1 +
 arch/powerpc/lib/Makefile                     |  2 ++
 arch/powerpc/purgatory/Makefile               |  1 +
 arch/powerpc/xmon/Makefile                    |  1 +
 arch/xtensa/lib/Makefile                      |  1 -
 kernel/kcsan/Makefile                         |  2 +-
 .../lib/kcsan-stubs.c => kernel/kcsan/stubs.c | 26 ++++++++++++++++++-
 13 files changed, 54 insertions(+), 14 deletions(-)
 rename arch/xtensa/lib/kcsan-stubs.c => kernel/kcsan/stubs.c (58%)

-- 
2.37.2