microblaze: ftrace: add function graph support

For more information look at Documentation/trace folder.

Signed-off-by: Michal Simek <monstr@monstr.eu>

1 files changed, 58 insertions, 0 deletions

diff --git a/arch/microblaze/kernel/ftrace.c b/arch/microblaze/kernel/ftrace.c
index c1889b101cb8..0952a8b52c35 100644
--- a/arch/microblaze/kernel/ftrace.c
+++ b/arch/microblaze/kernel/ftrace.c
@@ -14,6 +14,64 @@
 #include <asm/cacheflush.h>
 #include <linux/ftrace.h>
 
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+/*
+ * Hook the return address and push it in the stack of return addrs
+ * in current thread info.
+ */
+void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
+{
+        unsigned long old;
+        int faulted, err;
+        struct ftrace_graph_ent trace;
+        unsigned long return_hooker = (unsigned long)
+                                &return_to_handler;
+
+        if (unlikely(atomic_read(&current->tracing_graph_pause)))
+                return;
+
+        /*
+         * Protect against fault, even if it shouldn't
+         * happen. This tool is too much intrusive to
+         * ignore such a protection.
+         */
+        asm volatile("  1:      lwi     %0, %2, 0;              \
+                        2:      swi     %3, %2, 0;              \
+                                addik   %1, r0, 0;              \
+                        3:                                      \
+                                .section .fixup, \"ax\";        \
+                        4:      brid    3b;                     \
+                                addik   %1, r0, 1;              \
+                                .previous;                      \
+                                .section __ex_table,\"a\";      \
+                                .word   1b,4b;                  \
+                                .word   2b,4b;                  \
+                                .previous;"                     \
+                        : "=&r" (old), "=r" (faulted)
+                        : "r" (parent), "r" (return_hooker)
+        );
+
+        if (unlikely(faulted)) {
+                ftrace_graph_stop();
+                WARN_ON(1);
+                return;
+        }
+
+        err = ftrace_push_return_trace(old, self_addr, &trace.depth, 0);
+        if (err == -EBUSY) {
+                *parent = old;
+                return;
+        }
+
+        trace.func = self_addr;
+        /* Only trace if the calling function expects to */
+        if (!ftrace_graph_entry(&trace)) {
+                current->curr_ret_stack--;
+                *parent = old;
+        }
+}
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
 #ifdef CONFIG_DYNAMIC_FTRACE
 /* save value to addr - it is save to do it in asm */
 static int ftrace_modify_code(unsigned long addr, unsigned int value)