Merge tag 'v5.5-rc6' into devel

Linux 5.5-rc6

1 files changed, 23 insertions, 0 deletions

diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index 67e0c462b059..1af321dec0f1 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -96,11 +96,34 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func,
 	return 0;
 }
 
+/*
+ * Not all archs define MCOUNT_INSN_SIZE which is used to look for direct
+ * functions. But those archs currently don't support direct functions
+ * anyway, and ftrace_find_rec_direct() is just a stub for them.
+ * Define MCOUNT_INSN_SIZE to keep those archs compiling.
+ */
+#ifndef MCOUNT_INSN_SIZE
+/* Make sure this only works without direct calls */
+# ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+#  error MCOUNT_INSN_SIZE not defined with direct calls enabled
+# endif
+# define MCOUNT_INSN_SIZE 0
+#endif
+
 int function_graph_enter(unsigned long ret, unsigned long func,
 			 unsigned long frame_pointer, unsigned long *retp)
 {
 	struct ftrace_graph_ent trace;
 
+	/*
+	 * Skip graph tracing if the return location is served by direct trampoline,
+	 * since call sequence and return addresses is unpredicatable anymore.
+	 * Ex: BPF trampoline may call original function and may skip frame
+	 * depending on type of BPF programs attached.
+	 */
+	if (ftrace_direct_func_count &&
+	    ftrace_find_rec_direct(ret - MCOUNT_INSN_SIZE))
+		return -EBUSY;
 	trace.func = func;
 	trace.depth = ++current->curr_ret_depth;