diff options
| author | Soham Bagchi <soham.bagchi@utah.edu> | 2025-07-28 12:43:18 -0600 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2025-09-13 17:32:44 -0700 |
| commit | 1455b6ac210d5c094066264e7a6809c3a6a9a4d2 (patch) | |
| tree | dba745c94ac5804cf38a5eb92387dcbcc128c9ff | |
| parent | c2fe368b6eb24af72708890b04e9a773c8465703 (diff) | |
kcov: load acquire coverage count in user-space code
Update the KCOV documentation to use a load-acquire operation for the
first element of the shared memory buffer between kernel-space and
user-space.
The load-acquire pairs with the write memory barrier used in
kcov_move_area().
[soham.bagchi@utah.edu: v2]
Link: https://lkml.kernel.org/r/20250803180558.2967962-1-soham.bagchi@utah.edu
Link: https://lkml.kernel.org/r/20250728184318.1839137-2-soham.bagchi@utah.edu
Signed-off-by: Soham Bagchi <soham.bagchi@utah.edu>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | Documentation/dev-tools/kcov.rst | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/Documentation/dev-tools/kcov.rst b/Documentation/dev-tools/kcov.rst index 6611434e2dd2..8127849d40f5 100644 --- a/Documentation/dev-tools/kcov.rst +++ b/Documentation/dev-tools/kcov.rst @@ -361,7 +361,12 @@ local tasks spawned by the process and the global task that handles USB bus #1: */ sleep(2); - n = __atomic_load_n(&cover[0], __ATOMIC_RELAXED); + /* + * The load to the coverage count should be an acquire to pair with + * pair with the corresponding write memory barrier (smp_wmb()) on + * the kernel-side in kcov_move_area(). + */ + n = __atomic_load_n(&cover[0], __ATOMIC_ACQUIRE); for (i = 0; i < n; i++) printf("0x%lx\n", cover[i + 1]); if (ioctl(fd, KCOV_DISABLE, 0)) |