Blackfin: update ftrace for latest toolchain

The mcount support that was finally added to the Blackfin gcc port isn't
exactly the same as what ftrace was developed against.  Now that the final
gcc version is in place, update the ftrace code to match.

While updating this, fix the swapped arguments to the tracer (signature is
(ip, parent_ip) while we were passing (parent_ip, ip)).
Signed-off-by: Yi Li <yi.li@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

arch/blackfin/include/asm/ftrace.h

@@ -8,6 +8,6 @@
 #ifndef __ASM_BFIN_FTRACE_H__
 #define __ASM_BFIN_FTRACE_H__
 
-#define MCOUNT_INSN_SIZE	8 /* sizeof mcount call: LINK + CALL */
+#define MCOUNT_INSN_SIZE	6 /* sizeof "[++sp] = rets; call __mcount;" */
 
 #endif

arch/blackfin/kernel/ftrace-entry.S

@@ -17,8 +17,8 @@
  * only one we can blow away.  With pointer registers, we have P0-P2.
  *
  * Upon entry, the RETS will point to the top of the current profiled
- * function.  And since GCC setup the frame for us, the previous function
- * will be waiting there.  mmmm pie.
+ * function.  And since GCC pushed the previous RETS for us, the previous
+ * function will be waiting there.  mmmm pie.
  */
 ENTRY(__mcount)
 	/* save third function arg early so we can do testing below */
@@ -70,14 +70,14 @@ ENTRY(__mcount)
 	/* setup the tracer function */
 	p0 = r3;
 
-	/* tracer(ulong frompc, ulong selfpc):
-	 *  frompc: the pc that did the call to ...
-	 *  selfpc: ... this location
-	 * the selfpc itself will need adjusting for the mcount call
+	/* function_trace_call(unsigned long ip, unsigned long parent_ip):
+	 *  ip: this point was called by ...
+	 *  parent_ip: ... this function
+	 * the ip itself will need adjusting for the mcount call
 	 */
-	r1 = rets;
-	r0 = [fp + 4];
-	r1 += -MCOUNT_INSN_SIZE;
+	r0 = rets;
+	r1 = [sp + 16];	/* skip the 4 local regs on stack */
+	r0 += -MCOUNT_INSN_SIZE;
 
 	/* call the tracer */
 	call (p0);
@@ -106,9 +106,10 @@ ENTRY(_ftrace_graph_caller)
 	[--sp] = r1;
 	[--sp] = rets;
 
-	r0 = fp;
+	/* prepare_ftrace_return(unsigned long *parent, unsigned long self_addr) */
+	r0 = sp;
 	r1 = rets;
-	r0 += 4;
+	r0 += 16;	/* skip the 4 local regs on stack */
 	r1 += -MCOUNT_INSN_SIZE;
 	call _prepare_ftrace_return;