1 files changed, 34 insertions, 21 deletions

diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
index 6851fc97a511..6bfcb7a00ec6 100644
--- a/arch/mips/kernel/mcount.S
+++ b/arch/mips/kernel/mcount.S
@@ -6,6 +6,7 @@
  * more details.
  *
  * Copyright (C) 2009 Lemote Inc. & DSLab, Lanzhou University, China
+ * Copyright (C) 2010 DSLab, Lanzhou University, China
  * Author: Wu Zhangjin <wuzhangjin@gmail.com>
  */
 
@@ -45,8 +46,6 @@
         PTR_L   a5, PT_R9(sp)
         PTR_L   a6, PT_R10(sp)
         PTR_L   a7, PT_R11(sp)
-#endif
-#ifdef CONFIG_64BIT
         PTR_ADDIU       sp, PT_SIZE
 #else
         PTR_ADDIU       sp, (PT_SIZE + 8)
@@ -58,6 +57,12 @@
          move ra, AT
         .endm
 
+/*
+ * The -mmcount-ra-address option of gcc 4.5 uses register $12 to pass
+ * the location of the parent's return address.
+ */
+#define MCOUNT_RA_ADDRESS_REG   $12
+
 #ifdef CONFIG_DYNAMIC_FTRACE
 
 NESTED(ftrace_caller, PT_SIZE, ra)
@@ -71,14 +76,14 @@ _mcount:
 
         MCOUNT_SAVE_REGS
 #ifdef KBUILD_MCOUNT_RA_ADDRESS
-        PTR_S   t0, PT_R12(sp)  /* t0 saved the location of the return address(at) by -mmcount-ra-address */
+        PTR_S   MCOUNT_RA_ADDRESS_REG, PT_R12(sp)
 #endif
 
-        move    a0, ra          /* arg1: next ip, selfaddr */
+        move    a0, ra          /* arg1: self return address */
         .globl ftrace_call
 ftrace_call:
         nop     /* a placeholder for the call to a real tracing function */
-         move   a1, AT          /* arg2: the caller's next ip, parent */
+         move   a1, AT          /* arg2: parent's return address */
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
         .globl ftrace_graph_call
@@ -119,9 +124,9 @@ NESTED(_mcount, PT_SIZE, ra)
 static_trace:
         MCOUNT_SAVE_REGS
 
-        move    a0, ra          /* arg1: next ip, selfaddr */
+        move    a0, ra          /* arg1: self return address */
         jalr    t2              /* (1) call *ftrace_trace_function */
-         move   a1, AT          /* arg2: the caller's next ip, parent */
+         move   a1, AT          /* arg2: parent's return address */
 
         MCOUNT_RESTORE_REGS
         .globl ftrace_stub
@@ -134,28 +139,34 @@ ftrace_stub:
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 
 NESTED(ftrace_graph_caller, PT_SIZE, ra)
-#ifdef CONFIG_DYNAMIC_FTRACE
-        PTR_L   a1, PT_R31(sp)  /* load the original ra from the stack */
-#ifdef KBUILD_MCOUNT_RA_ADDRESS
-        PTR_L   t0, PT_R12(sp)  /* load the original t0 from the stack */
-#endif
-#else
+#ifndef CONFIG_DYNAMIC_FTRACE
         MCOUNT_SAVE_REGS
-        move    a1, ra          /* arg2: next ip, selfaddr */
 #endif
 
+        /* arg1: Get the location of the parent's return address */
 #ifdef KBUILD_MCOUNT_RA_ADDRESS
-        bnez    t0, 1f          /* non-leaf func: t0 saved the location of the return address */
+#ifdef CONFIG_DYNAMIC_FTRACE
+        PTR_L   a0, PT_R12(sp)
+#else
+        move    a0, MCOUNT_RA_ADDRESS_REG
+#endif
+        bnez    a0, 1f  /* non-leaf func: stored in MCOUNT_RA_ADDRESS_REG */
          nop
-        PTR_LA  t0, PT_R1(sp)   /* leaf func: get the location of at(old ra) from our own stack */
-1:      move    a0, t0          /* arg1: the location of the return address */
+#endif
+        PTR_LA  a0, PT_R1(sp)   /* leaf func: the location in current stack */
+1:
+
+        /* arg2: Get self return address */
+#ifdef CONFIG_DYNAMIC_FTRACE
+        PTR_L   a1, PT_R31(sp)
 #else
-        PTR_LA  a0, PT_R1(sp)   /* arg1: &AT -> a0 */
+        move    a1, ra
 #endif
-        jal     prepare_ftrace_return
+
+        /* arg3: Get frame pointer of current stack */
 #ifdef CONFIG_FRAME_POINTER
-         move   a2, fp          /* arg3: frame pointer */
-#else
+         move   a2, fp
+#else /* ! CONFIG_FRAME_POINTER */
 #ifdef CONFIG_64BIT
          PTR_LA a2, PT_SIZE(sp)
 #else
@@ -163,6 +174,8 @@ NESTED(ftrace_graph_caller, PT_SIZE, ra)
 #endif
 #endif
 
+        jal     prepare_ftrace_return
+         nop
         MCOUNT_RESTORE_REGS
         RETURN_BACK
         END(ftrace_graph_caller)