Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into locking/kcsan

Pull the KCSAN subsystem from Paul E. McKenney:

   "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@mail.gmail.com

    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@google.com/
   "

Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 108 insertions, 0 deletions

diff --git a/kernel/kcsan/kcsan.h b/kernel/kcsan/kcsan.h
new file mode 100644
index 000000000000..1bb2f1c0d61e
--- /dev/null
+++ b/kernel/kcsan/kcsan.h
@@ -0,0 +1,108 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * The Kernel Concurrency Sanitizer (KCSAN) infrastructure. For more info please
+ * see Documentation/dev-tools/kcsan.rst.
+ */
+
+#ifndef _KERNEL_KCSAN_KCSAN_H
+#define _KERNEL_KCSAN_KCSAN_H
+
+#include <linux/kcsan.h>
+
+/* The number of adjacent watchpoints to check. */
+#define KCSAN_CHECK_ADJACENT 1
+
+/*
+ * Globally enable and disable KCSAN.
+ */
+extern bool kcsan_enabled;
+
+/*
+ * Initialize debugfs file.
+ */
+void kcsan_debugfs_init(void);
+
+enum kcsan_counter_id {
+	/*
+	 * Number of watchpoints currently in use.
+	 */
+	KCSAN_COUNTER_USED_WATCHPOINTS,
+
+	/*
+	 * Total number of watchpoints set up.
+	 */
+	KCSAN_COUNTER_SETUP_WATCHPOINTS,
+
+	/*
+	 * Total number of data races.
+	 */
+	KCSAN_COUNTER_DATA_RACES,
+
+	/*
+	 * Number of times no watchpoints were available.
+	 */
+	KCSAN_COUNTER_NO_CAPACITY,
+
+	/*
+	 * A thread checking a watchpoint raced with another checking thread;
+	 * only one will be reported.
+	 */
+	KCSAN_COUNTER_REPORT_RACES,
+
+	/*
+	 * Observed data value change, but writer thread unknown.
+	 */
+	KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN,
+
+	/*
+	 * The access cannot be encoded to a valid watchpoint.
+	 */
+	KCSAN_COUNTER_UNENCODABLE_ACCESSES,
+
+	/*
+	 * Watchpoint encoding caused a watchpoint to fire on mismatching
+	 * accesses.
+	 */
+	KCSAN_COUNTER_ENCODING_FALSE_POSITIVES,
+
+	KCSAN_COUNTER_COUNT, /* number of counters */
+};
+
+/*
+ * Increment/decrement counter with given id; avoid calling these in fast-path.
+ */
+void kcsan_counter_inc(enum kcsan_counter_id id);
+void kcsan_counter_dec(enum kcsan_counter_id id);
+
+/*
+ * Returns true if data races in the function symbol that maps to func_addr
+ * (offsets are ignored) should *not* be reported.
+ */
+bool kcsan_skip_report_debugfs(unsigned long func_addr);
+
+enum kcsan_report_type {
+	/*
+	 * The thread that set up the watchpoint and briefly stalled was
+	 * signalled that another thread triggered the watchpoint.
+	 */
+	KCSAN_REPORT_RACE_SIGNAL,
+
+	/*
+	 * A thread found and consumed a matching watchpoint.
+	 */
+	KCSAN_REPORT_CONSUMED_WATCHPOINT,
+
+	/*
+	 * No other thread was observed to race with the access, but the data
+	 * value before and after the stall differs.
+	 */
+	KCSAN_REPORT_RACE_UNKNOWN_ORIGIN,
+};
+/*
+ * Print a race report from thread that encountered the race.
+ */
+void kcsan_report(const volatile void *ptr, size_t size, bool is_write,
+		  bool value_change, int cpu_id, enum kcsan_report_type type);
+
+#endif /* _KERNEL_KCSAN_KCSAN_H */