ftrace: powerpc clean ups

This patch cleans up the ftrace code in PowerPC based on the comments from
Michael Ellerman.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: proski@gnu.org
Cc: a.p.zijlstra@chello.nl
Cc: Pekka Paalanen <pq@iki.fi>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: linuxppc-dev@ozlabs.org
Cc: Soeren Sandmann Pedersen <sandmann@redhat.com>
Cc: paulus@samba.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/powerpc/kernel/entry_32.S

@@ -1129,18 +1129,11 @@ _GLOBAL(_mcount)
 	stw	r5, 8(r1)
 
 	LOAD_REG_ADDR(r5, ftrace_trace_function)
-#if 0
-	mtctr	r3
-	mr	r1, r5
-	bctrl
-#endif
 	lwz	r5,0(r5)
-#if 1
+
 	mtctr	r5
 	bctrl
-#else
-	bl	ftrace_stub
-#endif
+
 	nop
 
 	lwz	r6, 8(r1)

arch/powerpc/kernel/ftrace.c

@@ -51,10 +51,16 @@ notrace unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
 {
 	static unsigned int op;
 
+	/*
+	 * It would be nice to just use create_function_call, but that will
+	 * update the code itself. Here we need to just return the
+	 * instruction that is going to be modified, without modifying the
+	 * code.
+	 */
 	addr = GET_ADDR(addr);
 
 	/* Set to "bl addr" */
-	op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffe);
+	op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffc);
 
 	/*
 	 * No locking needed, this must be called via kstop_machine

arch/powerpc/kernel/ppc_ksyms.c

@@ -43,6 +43,7 @@
 #include <asm/div64.h>
 #include <asm/signal.h>
 #include <asm/dcr.h>
+#include <asm/ftrace.h>
 
 #ifdef CONFIG_PPC32
 extern void transfer_to_handler(void);
@@ -68,6 +69,10 @@ EXPORT_SYMBOL(single_step_exception);
 EXPORT_SYMBOL(sys_sigreturn);
 #endif
 
+#ifdef CONFIG_FTRACE
+EXPORT_SYMBOL(_mcount);
+#endif
+
 EXPORT_SYMBOL(strcpy);
 EXPORT_SYMBOL(strncpy);
 EXPORT_SYMBOL(strcat);

arch/powerpc/kernel/setup_32.c

@@ -47,11 +47,6 @@
 #include <asm/kgdb.h>
 #endif
 
-#ifdef CONFIG_FTRACE
-extern void _mcount(void);
-EXPORT_SYMBOL(_mcount);
-#endif
-
 extern void bootx_init(unsigned long r4, unsigned long phys);
 
 int boot_cpuid;

arch/powerpc/kernel/setup_64.c

@@ -85,11 +85,6 @@ struct ppc64_caches ppc64_caches = {
 };
 EXPORT_SYMBOL_GPL(ppc64_caches);
 
-#ifdef CONFIG_FTRACE
-extern void _mcount(void);
-EXPORT_SYMBOL(_mcount);
-#endif
-
 /*
  * These are used in binfmt_elf.c to put aux entries on the stack
  * for each elf executable being started.

include/asm-powerpc/ftrace.h

@@ -0,0 +1,6 @@
+#ifndef _ASM_POWERPC_FTRACE
+#define _ASM_POWERPC_FTRACE
+
+extern void _mcount(void);
+
+#endif