When multiple callbacks are registered on the same tracepoint,
callbacks will be indirectly called via traceiter helper.
Pointers to __probestub_* callbacks reside in __tracepoints section,
which is excluded from ENDBR checks in objtool, causing objtool to
assume those functions are never indirectly called.
Registering multiple callbacks using sched_wakeup test will result
in #CP exception due to missing ENDBR in __probestub_sched_wakeup
on a CFI-enabled machine.
Fix this by adding CFI_NOSEAL annotation to probestub declaration.
Fixes: d5173f753750 ("objtool: Exclude __tracepoints data from ENDBR checks")
Signed-off-by: Eva Kurchatova <[email protected]>
---
include/linux/tracepoint.h | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 763eea4d80d8..2d2b9f8cdda4 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -20,6 +20,7 @@
#include <linux/rcupdate_trace.h>
#include <linux/tracepoint-defs.h>
#include <linux/static_call.h>
+#include <linux/cfi.h>
struct module;
struct tracepoint;
@@ -389,6 +390,13 @@ static inline struct tracepoint
*tracepoint_ptr_deref(tracepoint_ptr_t *p)
void __probestub_##_name(void *__data, proto) \
{ \
} \
+ /* \
+ * Annotate the probestub 'CFI_NOSEAL' to stop objtool from \
+ * requesting the kernel remove the ENDBR, because the only \
+ * references to the function are in the __tracepoint section, \
+ * that objtool doesn't scan. \
+ */ \
+ CFI_NOSEAL(__probestub_##_name); \
DEFINE_STATIC_CALL(tp_func_##_name, __traceiter_##_name); \
DEFINE_RUST_DO_TRACE(_name, TP_PROTO(proto), TP_ARGS(args))
--
2.54.0
