Merge tag 'kcsan.2024.05.10a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull kcsan update from Paul McKenney:
 "Introduce __data_racy type qualifier

  This adds a __data_racy type qualifier that enables kernel developers
  to inform KCSAN that a given variable is a shared variable without
  needing to mark each and every access.

  This allows pre-KCSAN code to be correctly (if approximately)
  instrumented withh very little effort, and also provides people
  reading the code a clear indication that the variable is in fact
  shared.

  In addition, it permits incremental transition to per-access KCSAN
  marking, so that (for example) a given subsystem can be transitioned
  one variable at a time, while avoiding large numbers of KCSAN warnings
  during this transition"

* tag 'kcsan.2024.05.10a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  kcsan, compiler_types: Introduce __data_racy type qualifier

1 files changed, 7 insertions, 0 deletions

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 8f8236317d5b..774c2570fe51 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -273,9 +273,16 @@ struct ftrace_likely_data {
  * disable all instrumentation. See Kconfig.kcsan where this is mandatory.
  */
 # define __no_kcsan __no_sanitize_thread __disable_sanitizer_instrumentation
+/*
+ * Type qualifier to mark variables where all data-racy accesses should be
+ * ignored by KCSAN. Note, the implementation simply marks these variables as
+ * volatile, since KCSAN will treat such accesses as "marked".
+ */
+# define __data_racy volatile
 # define __no_sanitize_or_inline __no_kcsan notrace __maybe_unused
 #else
 # define __no_kcsan
+# define __data_racy
 #endif
 
 #ifdef __SANITIZE_MEMORY__