[PATCH] kcov: refactor common handle ID into kcov_common_handle_id

[Jann Horn]

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.

Signed-off-by: Jann Horn <ja...@google.com>
---
drivers/usb/usbip/usbip_common.h | 29 +----------------------------
drivers/usb/usbip/vhci_rx.c | 4 ++--
drivers/usb/usbip/vhci_sysfs.c | 2 +-
drivers/vhost/vhost.h | 2 +-
include/linux/kcov.h | 12 ++++++------
include/linux/skbuff.h | 14 +++-----------
include/linux/types.h | 6 ++++++
kernel/kcov.c | 6 +++---
8 files changed, 23 insertions(+), 52 deletions(-)

diff --git a/drivers/usb/usbip/usbip_common.h b/drivers/usb/usbip/usbip_common.h
index 282efca64a01..be4c5e65a7f8 100644
--- a/drivers/usb/usbip/usbip_common.h
+++ b/drivers/usb/usbip/usbip_common.h
@@ -282,9 +282,7 @@ struct usbip_device {
void (*unusable)(struct usbip_device *);
} eh_ops;

-#ifdef CONFIG_KCOV
- u64 kcov_handle;
-#endif
+ struct kcov_common_handle_id kcov_handle;
};

#define kthread_get_run(threadfn, data, namefmt, ...) \
@@ -339,29 +337,4 @@ static inline int interface_to_devnum(struct usb_interface *interface)
return udev->devnum;
}

-#ifdef CONFIG_KCOV
-
-static inline void usbip_kcov_handle_init(struct usbip_device *ud)
-{
- ud->kcov_handle = kcov_common_handle();
-}
-
-static inline void usbip_kcov_remote_start(struct usbip_device *ud)
-{
- kcov_remote_start_common(ud->kcov_handle);
-}
-
-static inline void usbip_kcov_remote_stop(void)
-{
- kcov_remote_stop();
-}
-
-#else /* CONFIG_KCOV */
-
-static inline void usbip_kcov_handle_init(struct usbip_device *ud) { }
-static inline void usbip_kcov_remote_start(struct usbip_device *ud) { }
-static inline void usbip_kcov_remote_stop(void) { }
-
-#endif /* CONFIG_KCOV */
-
#endif /* __USBIP_COMMON_H */
diff --git a/drivers/usb/usbip/vhci_rx.c b/drivers/usb/usbip/vhci_rx.c
index a75f4a898a41..a678e7c89837 100644
--- a/drivers/usb/usbip/vhci_rx.c
+++ b/drivers/usb/usbip/vhci_rx.c
@@ -261,9 +261,9 @@ int vhci_rx_loop(void *data)
if (usbip_event_happened(ud))
break;

- usbip_kcov_remote_start(ud);
+ kcov_remote_start_common(ud->kcov_handle);
vhci_rx_pdu(ud);
- usbip_kcov_remote_stop();
+ kcov_remote_stop();
}

return 0;
diff --git a/drivers/usb/usbip/vhci_sysfs.c b/drivers/usb/usbip/vhci_sysfs.c
index 5bc8c47788d4..b98d14c43d13 100644
--- a/drivers/usb/usbip/vhci_sysfs.c
+++ b/drivers/usb/usbip/vhci_sysfs.c
@@ -425,7 +425,7 @@ static ssize_t attach_store(struct device *dev, struct device_attribute *attr,
vdev->ud.tcp_rx = tcp_rx;
vdev->ud.tcp_tx = tcp_tx;
vdev->ud.status = VDEV_ST_NOTASSIGNED;
- usbip_kcov_handle_init(&vdev->ud);
+ vdev->ud.kcov_handle = kcov_common_handle();

spin_unlock(&vdev->ud.lock);
spin_unlock_irqrestore(&vhci->lock, flags);
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 4fe99765c5c7..0192ade6e749 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -44,7 +44,7 @@ struct vhost_worker {
/* Used to serialize device wide flushing with worker swapping. */
struct mutex mutex;
struct llist_head work_list;
- u64 kcov_handle;
+ struct kcov_common_handle_id kcov_handle;
u32 id;
int attachment_cnt;
bool killed;
diff --git a/include/linux/kcov.h b/include/linux/kcov.h
index 0143358874b0..cdb72b3859d8 100644
--- a/include/linux/kcov.h
+++ b/include/linux/kcov.h
@@ -43,11 +43,11 @@ do { \
/* See Documentation/dev-tools/kcov.rst for usage details. */
void kcov_remote_start(u64 handle);
void kcov_remote_stop(void);
-u64 kcov_common_handle(void);
+struct kcov_common_handle_id kcov_common_handle(void);

-static inline void kcov_remote_start_common(u64 id)
+static inline void kcov_remote_start_common(struct kcov_common_handle_id id)
{
- kcov_remote_start(kcov_remote_handle(KCOV_SUBSYSTEM_COMMON, id));
+ kcov_remote_start(kcov_remote_handle(KCOV_SUBSYSTEM_COMMON, id.val));
}

static inline void kcov_remote_start_usb(u64 id)
@@ -99,11 +99,11 @@ static inline void kcov_prepare_switch(struct task_struct *t) {}
static inline void kcov_finish_switch(struct task_struct *t) {}
static inline void kcov_remote_start(u64 handle) {}
static inline void kcov_remote_stop(void) {}
-static inline u64 kcov_common_handle(void)
+static inline struct kcov_common_handle_id kcov_common_handle(void)
{
- return 0;
+ return (struct kcov_common_handle_id){};
}
-static inline void kcov_remote_start_common(u64 id) {}
+static inline void kcov_remote_start_common(struct kcov_common_handle_id id) {}
static inline void kcov_remote_start_usb(u64 id) {}
static inline void kcov_remote_start_usb_softirq(u64 id) {}
static inline void kcov_remote_stop_softirq(void) {}
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2bcf78a4de7b..a3fe418f7ced 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1082,9 +1082,7 @@ struct sk_buff {
__u16 network_header;
__u16 mac_header;

-#ifdef CONFIG_KCOV
- u64 kcov_handle;
-#endif
+ struct kcov_common_handle_id kcov_handle;

); /* end headers group */

@@ -5437,20 +5435,14 @@ static inline void skb_reset_csum_not_inet(struct sk_buff *skb)
}

static inline void skb_set_kcov_handle(struct sk_buff *skb,
- const u64 kcov_handle)
+ struct kcov_common_handle_id kcov_handle)
{
-#ifdef CONFIG_KCOV
skb->kcov_handle = kcov_handle;
-#endif
}

-static inline u64 skb_get_kcov_handle(struct sk_buff *skb)
+static inline struct kcov_common_handle_id skb_get_kcov_handle(struct sk_buff *skb)
{
-#ifdef CONFIG_KCOV
return skb->kcov_handle;
-#else
- return 0;
-#endif
}

static inline void skb_mark_for_recycle(struct sk_buff *skb)
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
diff --git a/kernel/kcov.c b/kernel/kcov.c
index 0b369e88c7c9..a43e33a28adb 100644
--- a/kernel/kcov.c
+++ b/kernel/kcov.c
@@ -1083,11 +1083,11 @@ void kcov_remote_stop(void)
EXPORT_SYMBOL(kcov_remote_stop);

/* See the comment before kcov_remote_start() for usage details. */
-u64 kcov_common_handle(void)
+struct kcov_common_handle_id kcov_common_handle(void)
{
if (!in_task())
- return 0;
- return current->kcov_handle;
+ return (struct kcov_common_handle_id){ .val = 0 };
+ return (struct kcov_common_handle_id){ .val = current->kcov_handle };
}
EXPORT_SYMBOL(kcov_common_handle);


---
base-commit: 57b8e2d666a31fa201432d58f5fe3469a0dd83ba
change-id: 20260430-kcov-refactor-common-handle-25178495b2eb

--
Jann Horn <ja...@google.com>