ARM: ftrace: function graph tracer support

Cc: Tim Bird <tim.bird@am.sony.com>
[rabin@rab.in: rebase on top of latest code,
	       keep code in ftrace.c instead of separate file,
	       check for ftrace_graph_entry also]
Signed-off-by: Rabin Vincent <rabin@rab.in>

3 files changed, 82 insertions, 1 deletions

diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 5b9b268f4fbb..679851a9f589 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -5,7 +5,7 @@
 CPPFLAGS_vmlinux.lds := -DTEXT_OFFSET=$(TEXT_OFFSET)
 AFLAGS_head.o        := -DTEXT_OFFSET=$(TEXT_OFFSET)
 
-ifdef CONFIG_DYNAMIC_FTRACE
+ifdef CONFIG_FUNCTION_TRACER
 CFLAGS_REMOVE_ftrace.o = -pg
 endif
 
@@ -33,6 +33,7 @@ obj-$(CONFIG_SMP)		+= smp.o
 obj-$(CONFIG_HAVE_ARM_SCU)      += smp_scu.o
 obj-$(CONFIG_HAVE_ARM_TWD)      += smp_twd.o
 obj-$(CONFIG_DYNAMIC_FTRACE)    += ftrace.o
+obj-$(CONFIG_FUNCTION_GRAPH_TRACER)     += ftrace.o
 obj-$(CONFIG_KEXEC)             += machine_kexec.o relocate_kernel.o
 obj-$(CONFIG_KPROBES)           += kprobes.o kprobes-decode.o
 obj-$(CONFIG_ATAGS_PROC)        += atags.o
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index fe1d5862b19f..9f1766211668 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -148,6 +148,20 @@ ENDPROC(ret_from_fork)
         adr     r0, .Lftrace_stub
         cmp     r0, r2
         bne     1f
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+        ldr     r1, =ftrace_graph_return
+        ldr     r2, [r1]
+        cmp     r0, r2
+        bne     ftrace_graph_caller\suffix
+
+        ldr     r1, =ftrace_graph_entry
+        ldr     r2, [r1]
+        ldr     r0, =ftrace_graph_entry_stub
+        cmp     r0, r2
+        bne     ftrace_graph_caller\suffix
+#endif
+
         mcount_exit
 
 1:      mcount_get_lr   r1                      @ lr of instrumented func
@@ -172,6 +186,15 @@ ftrace_call\suffix:
         mcount_exit
 .endm
 
+.macro __ftrace_graph_caller
+        sub     r0, fp, #4              @ &lr of instrumented routine (&parent)
+        mov     r1, lr                  @ instrumented routine (func)
+        sub     r1, r1, #MCOUNT_INSN_SIZE
+        mov     r2, fp                  @ frame pointer
+        bl      prepare_ftrace_return
+        mcount_exit
+.endm
+
 #ifdef CONFIG_OLD_MCOUNT
 /*
  * mcount
@@ -206,6 +229,12 @@ ENTRY(ftrace_caller_old)
 ENDPROC(ftrace_caller_old)
 #endif
 
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ENTRY(ftrace_graph_caller_old)
+        __ftrace_graph_caller
+ENDPROC(ftrace_graph_caller_old)
+#endif
+
 .purgem mcount_enter
 .purgem mcount_get_lr
 .purgem mcount_exit
@@ -244,10 +273,27 @@ ENTRY(ftrace_caller)
 ENDPROC(ftrace_caller)
 #endif
 
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ENTRY(ftrace_graph_caller)
+        __ftrace_graph_caller
+ENDPROC(ftrace_graph_caller)
+#endif
+
 .purgem mcount_enter
 .purgem mcount_get_lr
 .purgem mcount_exit
 
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+        .globl return_to_handler
+return_to_handler:
+        stmdb   sp!, {r0-r3}
+        mov     r0, fp                  @ frame pointer
+        bl      ftrace_return_to_handler
+        mov     lr, r0                  @ r0 has real ret addr
+        ldmia   sp!, {r0-r3}
+        mov     pc, lr
+#endif
+
 ENTRY(ftrace_stub)
 .Lftrace_stub:
         mov     pc, lr
diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index 971ac8c36ea7..7a702a502871 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -24,6 +24,7 @@
 #define NOP             0xe8bd4000      /* pop {lr} */
 #endif
 
+#ifdef CONFIG_DYNAMIC_FTRACE
 #ifdef CONFIG_OLD_MCOUNT
 #define OLD_MCOUNT_ADDR ((unsigned long) mcount)
 #define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old)
@@ -193,3 +194,36 @@ int __init ftrace_dyn_arch_init(void *data)
 
         return 0;
 }
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
+                           unsigned long frame_pointer)
+{
+        unsigned long return_hooker = (unsigned long) &return_to_handler;
+        struct ftrace_graph_ent trace;
+        unsigned long old;
+        int err;
+
+        if (unlikely(atomic_read(&current->tracing_graph_pause)))
+                return;
+
+        old = *parent;
+        *parent = return_hooker;
+
+        err = ftrace_push_return_trace(old, self_addr, &trace.depth,
+                                       frame_pointer);
+        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 */