MIPS: Tracing: Make function graph tracer work with -mmcount-ra-address

[pandora-kernel.git] / arch / mips / kernel / ftrace.c

diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
index e363fc6..68b0670 100644 (file)
--- a/arch/mips/kernel/ftrace.c
+++ b/arch/mips/kernel/ftrace.c
@@ -148,6 +148,7 @@ int ftrace_disable_ftrace_graph_caller(void)
 
 #endif                         /* !CONFIG_DYNAMIC_FTRACE */
 
+#ifndef KBUILD_MCOUNT_RA_ADDRESS
 #define S_RA_SP        (0xafbf << 16)  /* s{d,w} ra, offset(sp) */
 #define S_R_SP (0xafb0 << 16)  /* s{d,w} R, offset(sp) */
 #define OFFSET_MASK    0xffff  /* stack offset range: 0 ~ PT_SIZE */
@@ -201,6 +202,8 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
        return 0;
 }
 
+#endif
+
 /*
  * Hook the return address and push it in the stack of return addrs
  * in current thread info.
@@ -218,19 +221,26 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
                return;
 
        /* "parent" is the stack address saved the return address of the caller
-        * of _mcount, for a leaf function not save the return address in the
-        * stack address, so, we "emulate" one in _mcount's stack space, and
-        * hijack it directly, but for a non-leaf function, it will save the
-        * return address to the its stack space, so, we can not hijack the
-        * "parent" directly, but need to find the real stack address,
+        * of _mcount.
+        *
+        * if the gcc < 4.5, a leaf function does not save the return address
+        * in the stack address, so, we "emulate" one in _mcount's stack space,
+        * and hijack it directly, but for a non-leaf function, it save the
+        * return address to the its own stack space, we can not hijack it
+        * directly, but need to find the real stack address,
         * ftrace_get_parent_addr() does it!
+        *
+        * if gcc>= 4.5, with the new -mmcount-ra-address option, for a
+        * non-leaf function, the location of the return address will be saved
+        * to $12 for us, and for a leaf function, only put a zero into $12. we
+        * do it in ftrace_graph_caller of mcount.S.
         */
 
        /* old = *parent; */
        safe_load_stack(old, parent, faulted);
        if (unlikely(faulted))
                goto out;
-
+#ifndef KBUILD_MCOUNT_RA_ADDRESS
        parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old,
                                                         (unsigned long)parent,
                                                         fp);
@@ -238,7 +248,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
         * ra, stop function graph tracer and return */
        if (parent == 0)
                goto out;
-
+#endif
        /* *parent = return_hooker; */
        safe_store_stack(return_hooker, parent, faulted);
        if (unlikely(faulted))