kcov: refactor common handle ID into kcov_common_handle_id

Store common handle IDs in "struct kcov_common_handle_id", which consumes
no space in non-KCOV builds.

This cleanup removes #ifdef boilerplate code from subsystems that
integrate with KCOV (in particular in usbip_common.h and skbuff.h, see the
diffstat).

This should also make it easier to add KCOV remote coverage to more
subsystems in the future.

Link: https://lore.kernel.org/20260430-kcov-refactor-common-handle-v1-1-23a0c7a0ba38@google.com
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Eugenio Pérez <eperezma@redhat.com>
Cc: Hongren (Zenithal) Zheng <i@zenithal.me>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Valentina Manea <valentina.manea.m@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/types.h b/include/linux/types.h
index 608050dbca6a..93166b0b0617 100644
--- a/include/linux/types.h
+++ b/include/linux/types.h
@@ -224,6 +224,12 @@ struct ustat {
 	char			f_fpack[6];
 };
 
+struct kcov_common_handle_id {
+#ifdef CONFIG_KCOV
+	u64 val;
+#endif
+};
+
 /**
  * struct callback_head - callback structure for use with RCU and task_work
  * @next: next update requests in a list