[PATCH v9 07/10] tracing: add dynamic function graph tracer for MIPS

[Wu Zhangjin <wuzhangjin@gmail.com>]

From: Wu Zhangjin <wuzhangjin@gmail.com>

This patch make function graph tracer work with dynamic function tracer.

To share the source code of dynamic function tracer(MCOUNT_SAVE_REGS),
and avoid restoring the whole saved registers, we need to restore the ra
register from the stack.

(NOTE: This not work with 32bit! need to ensure why!)

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
---
 arch/mips/kernel/ftrace.c |   21 +++++++++++++++++++++
 arch/mips/kernel/mcount.S |   14 ++++++++++++--
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
index 65a3f8a..e981a49 100644
--- a/arch/mips/kernel/ftrace.c
+++ b/arch/mips/kernel/ftrace.c
@@ -115,6 +115,27 @@ int __init ftrace_dyn_arch_init(void *data)
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+extern void ftrace_graph_call(void);
+#define JMP    0x08000000      /* jump to target directly */
+#define CALL_FTRACE_GRAPH_CALLER \
+       jump_insn_encode(JMP, (unsigned long)(&ftrace_graph_caller))
+#define FTRACE_GRAPH_CALL_IP   ((unsigned long)(&ftrace_graph_call))
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+       return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
+                                 CALL_FTRACE_GRAPH_CALLER);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+       return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, ftrace_nop);
+}
+
+#endif                         /* !CONFIG_DYNAMIC_FTRACE */
+
 #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 */
diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
index b50e38d..98d4690 100644
--- a/arch/mips/kernel/mcount.S
+++ b/arch/mips/kernel/mcount.S
@@ -77,6 +77,13 @@ ftrace_call:
        nop     /* a placeholder for the call to a real tracing function */
         move   a1, AT          /* arg2: the caller's next ip, parent */
 
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+       .globl ftrace_graph_call
+ftrace_graph_call:
+       nop
+        nop
+#endif
+
        MCOUNT_RESTORE_REGS
        .globl ftrace_stub
 ftrace_stub:
@@ -124,10 +131,13 @@ 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 */
+#else
        MCOUNT_SAVE_REGS
-
-       PTR_LA  a0, PT_R1(sp)   /* arg1: &AT -> a0 */
        move    a1, ra          /* arg2: next ip, selfaddr */
+#endif
+       PTR_LA  a0, PT_R1(sp)   /* arg1: &AT -> a0 */
        jal     prepare_ftrace_return
         move   a2, fp          /* arg3: frame pointer */
 
-- 
1.6.2.1