tracing: Fix CFI violation in probestub being called by tprobes

The probestub is a function to allow tprobes to hook to a tracepoint to
gain access to its parameters. The function itself is only referenced by
the tracepoint structure which lives in the __tracepoint section. objtool
explicitly ignores that section and when processing functions in the
kernel, if it detects one that has no references it will seal it to have
its ENDBR stripped on boot up.

This means when a tprobe is attached to the sched_wakeup tracepoint, when it
is triggered it will call __probestub_sched_wakeup and due to the missing
ENDBR on a CFI-enabled machine it will take a #CP exception.

Fix this by adding CFI_NOSEAL annotation to probestub declaration.

Cc: stable@vger.kernel.org
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Link: https://patch.msgid.link/20260603153147.573589-1-eva.kurchatova@virtuozzo.com
Fixes: d5173f753750 ("objtool: Exclude __tracepoints data from ENDBR checks")
Signed-off-by: Eva Kurchatova <eva.kurchatova@virtuozzo.com>
[ Updated change log ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 763eea4d80d87b6aacb5faad92b3f136186cd37f..2d2b9f8cdda43d9057c740c5ee9ab166616caa7f 100644 (file)
--- 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))