arm64: ftrace: Add dynamic ftrace support

[firefly-linux-kernel-4.4.55.git] / arch / arm64 / kernel / entry-ftrace.S

diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S
index b2d8c4559cd83afd6ab0e699daa7c03707ce36ae..b051871f296597bcd9317bf59476d9545656baf6 100644 (file)
--- a/arch/arm64/kernel/entry-ftrace.S
+++ b/arch/arm64/kernel/entry-ftrace.S
@@ -86,6 +86,7 @@
        add     \reg, \reg, #8
        .endm
 
+#ifndef CONFIG_DYNAMIC_FTRACE
 /*
  * void _mcount(unsigned long return_address)
  * @return_address: return address to instrumented function
@@ -134,6 +135,48 @@ skip_ftrace_call:
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 ENDPROC(_mcount)
 
+#else /* CONFIG_DYNAMIC_FTRACE */
+/*
+ * _mcount() is used to build the kernel with -pg option, but all the branch
+ * instructions to _mcount() are replaced to NOP initially at kernel start up,
+ * and later on, NOP to branch to ftrace_caller() when enabled or branch to
+ * NOP when disabled per-function base.
+ */
+ENTRY(_mcount)
+       ret
+ENDPROC(_mcount)
+
+/*
+ * void ftrace_caller(unsigned long return_address)
+ * @return_address: return address to instrumented function
+ *
+ * This function is a counterpart of _mcount() in 'static' ftrace, and
+ * makes calls to:
+ *     - tracer function to probe instrumented function's entry,
+ *     - ftrace_graph_caller to set up an exit hook
+ */
+ENTRY(ftrace_caller)
+       mcount_enter
+
+       mcount_get_pc0  x0              //     function's pc
+       mcount_get_lr   x1              //     function's lr
+
+       .global ftrace_call
+ftrace_call:                           // tracer(pc, lr);
+       nop                             // This will be replaced with "bl xxx"
+                                       // where xxx can be any kind of tracer.
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+       .global ftrace_graph_call
+ftrace_graph_call:                     // ftrace_graph_caller();
+       nop                             // If enabled, this will be replaced
+                                       // "b ftrace_graph_caller"
+#endif
+
+       mcount_exit
+ENDPROC(ftrace_caller)
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
 ENTRY(ftrace_stub)
        ret
 ENDPROC(ftrace_stub)