ftrace: Pass retval through return in ftrace_dyn_arch_init()

No architecture uses the "data" parameter in ftrace_dyn_arch_init() in any
way, it just sets the value to 0. And this is used as a return value
in the caller -- ftrace_init, which just checks the retval against
zero.

Note there is also "return 0" in every ftrace_dyn_arch_init.  So it is
enough to check the retval and remove all the indirect sets of data on
all archs.

Link: http://lkml.kernel.org/r/1393268401-24379-3-git-send-email-jslaby@suse.cz

Cc: linux-arch@vger.kernel.org
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Documentation/trace/ftrace-design.txt

@@ -360,9 +360,6 @@ function below should be sufficient for most people:
 
 int __init ftrace_dyn_arch_init(void *data)
 {
-	/* return value is done indirectly via data */
-	*(unsigned long *)data = 0;
-
 	return 0;
 }
 

arch/arm/kernel/ftrace.c

@@ -158,8 +158,6 @@ int ftrace_make_nop(struct module *mod,
 
 int __init ftrace_dyn_arch_init(void *data)
 {
-	*(unsigned long *)data = 0;
-
 	return 0;
 }
 #endif /* CONFIG_DYNAMIC_FTRACE */

arch/blackfin/kernel/ftrace.c

@@ -67,9 +67,6 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 
 int __init ftrace_dyn_arch_init(void *data)
 {
-	/* return value is done indirectly via data */
-	*(unsigned long *)data = 0;
-
 	return 0;
 }
 

arch/ia64/kernel/ftrace.c

@@ -200,7 +200,5 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 /* run from kstop_machine */
 int __init ftrace_dyn_arch_init(void *data)
 {
-	*(unsigned long *)data = 0;
-
 	return 0;
 }

arch/metag/kernel/ftrace.c

@@ -119,8 +119,5 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 /* run from kstop_machine */
 int __init ftrace_dyn_arch_init(void *data)
 {
-	/* The return code is returned via data */
-	writel(0, data);
-
 	return 0;
 }

arch/microblaze/kernel/ftrace.c

@@ -173,9 +173,6 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 
 int __init ftrace_dyn_arch_init(void *data)
 {
-	/* The return code is retured via data */
-	*(unsigned long *)data = 0;
-
 	return 0;
 }
 

arch/mips/kernel/ftrace.c

@@ -206,9 +206,6 @@ int __init ftrace_dyn_arch_init(void *data)
 	/* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
 	ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
 
-	/* The return code is retured via data */
-	*(unsigned long *)data = 0;
-
 	return 0;
 }
 #endif	/* CONFIG_DYNAMIC_FTRACE */

arch/powerpc/kernel/ftrace.c

@@ -533,11 +533,6 @@ void arch_ftrace_update_code(int command)
 
 int __init ftrace_dyn_arch_init(void *data)
 {
-	/* caller expects data to be zero */
-	unsigned long *p = data;
-
-	*p = 0;
-
 	return 0;
 }
 #endif /* CONFIG_DYNAMIC_FTRACE */

arch/s390/kernel/ftrace.c

@@ -132,7 +132,6 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 
 int __init ftrace_dyn_arch_init(void *data)
 {
-	*(unsigned long *) data = 0;
 	return 0;
 }
 

arch/sh/kernel/ftrace.c

@@ -274,9 +274,6 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 
 int __init ftrace_dyn_arch_init(void *data)
 {
-	/* The return code is retured via data */
-	__raw_writel(0, (unsigned long)data);
-
 	return 0;
 }
 #endif /* CONFIG_DYNAMIC_FTRACE */

arch/sparc/kernel/ftrace.c

@@ -84,10 +84,6 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 
 int __init ftrace_dyn_arch_init(void *data)
 {
-	unsigned long *p = data;
-
-	*p = 0;
-
 	return 0;
 }
 #endif

arch/tile/kernel/ftrace.c

@@ -169,8 +169,6 @@ int ftrace_make_nop(struct module *mod,
 
 int __init ftrace_dyn_arch_init(void *data)
 {
-	*(unsigned long *)data = 0;
-
 	return 0;
 }
 #endif /* CONFIG_DYNAMIC_FTRACE */

arch/x86/kernel/ftrace.c

@@ -670,9 +670,6 @@ void arch_ftrace_update_code(int command)
 
 int __init ftrace_dyn_arch_init(void *data)
 {
-	/* The return code is retured via data */
-	*(unsigned long *)data = 0;
-
 	return 0;
 }
 #endif

kernel/trace/ftrace.c

@@ -4379,11 +4379,9 @@ void __init ftrace_init(void)
 	addr = (unsigned long)ftrace_stub;
 
 	local_irq_save(flags);
-	ftrace_dyn_arch_init(&addr);
+	ret = ftrace_dyn_arch_init(&addr);
 	local_irq_restore(flags);
-
+	if (ret)
-	/* ftrace_dyn_arch_init places the return code in addr */
-	if (addr)
 		goto failed;
 
 	count = __stop_mcount_loc - __start_mcount_loc;