microblaze: ftrace: add function graph support

For more information look at Documentation/trace folder.

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

2 files changed, 99 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)
diff --git a/arch/microblaze/kernel/mcount.S b/arch/microblaze/kernel/mcount.S
index 30aaf8fb55b2..84a19458c74d 100644
--- a/arch/microblaze/kernel/mcount.S
+++ b/arch/microblaze/kernel/mcount.S
@@ -96,6 +96,27 @@ ENTRY(ftrace_caller)
         bneid   r5, end;
         nop;
         /* MS: HAVE_FUNCTION_TRACE_MCOUNT_TEST end of checking */
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+        lwi     r5, r0, ftrace_graph_return;
+        addik   r6, r0, ftrace_stub; /* asm implementation */
+        cmpu    r5, r5, r6; /* ftrace_graph_return != ftrace_stub */
+        beqid   r5, end_graph_tracer;
+        nop;
+
+        lwi     r6, r0, ftrace_graph_entry;
+        addik   r5, r0, ftrace_graph_entry_stub; /* implemented in C */
+        cmpu    r5, r5, r6; /* ftrace_graph_entry != ftrace_graph_entry_stub */
+        beqid   r5, end_graph_tracer;
+        nop;
+        addik   r5, r1, 120; /* MS: load parent addr */
+        addik   r6, r15, 0; /* MS: load current function addr */
+        bralid  r15, prepare_ftrace_return;
+        nop;
+        /* MS: graph was taken that's why - can jump over function trace */
+        brid    end;
+        nop;
+end_graph_tracer:
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 #ifndef CONFIG_DYNAMIC_FTRACE
         /* MS: test function trace if is taken or not */
         lwi     r20, r0, ftrace_trace_function;
@@ -121,3 +142,23 @@ end:
 
         rtsd    r15, 8; /* MS: jump back */
         nop;
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ENTRY(return_to_handler)
+        nop; /* MS: just barrier for rtsd r15, 8 */
+        nop;
+        SAVE_REGS
+        swi     r15, r1, 0;
+
+        /* MS: find out returning address */
+        bralid  r15, ftrace_return_to_handler;
+        nop;
+
+        /* MS: return value from ftrace_return_to_handler is my returning addr
+         * must be before restore regs because I have to restore r3 content */
+        addik   r15, r3, 0;
+        RESTORE_REGS
+
+        rtsd    r15, 8; /* MS: jump back */
+        nop;
+#endif  /* CONFIG_FUNCTION_TRACER */