[PATCH v4 05/15] tracepoint: Exclude tp_stub_func from CFI checking

Sami Tolvanen
2021-09-30T18:05:55Z

If allocate_probes fails, func_remove replaces the old function
with a pointer to tp_stub_func, which is called using a mismatching
function pointer that will always trip indirect call checks with
CONFIG_CFI_CLANG. Use DEFINE_CFI_IMMEDATE_RETURN_STUB to define
tp_stub_func to allow it to pass CFI checking.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
---
kernel/tracepoint.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 64ea283f2f86..58acc7d86c3f 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -99,10 +99,7 @@ struct tp_probes {
};

/* Called in removal of a func but failed to allocate a new tp_funcs */
-static void tp_stub_func(void)
-{
- return;
-}
+static DEFINE_CFI_IMMEDIATE_RETURN_STUB(tp_stub_func);

static inline void *allocate_probes(int count)
{
--
2.33.0.800.g4c38ced690-goog