[PATCH] kernel: Shrink embedded kernel, remove WARN strings when !CONFIG_PRINTK

[Joe Perches]

WARN strings are currently always saved in text.
When printk is not enabled, this wastes space.

Don't call or compile slowpath_warn_<foo> when !CONFIG_PRINTK.

This makes an embedded image without printk support ~1% smaller.

x86-32 allnoconfig/embedded:

$ size vmlinux.new vmlinux.old
   text	   data	    bss	    dec	    hex	filename
1180807	 182720	1269372	2632899	 282cc3	vmlinux.new
1198760	 182720	1267948	2649428	 286d54	vmlinux.old

Signed-off-by: Joe Perches <joe at perches.com>
---
 include/asm-generic/bug.h |   18 +++++++++++++++++-
 kernel/panic.c            |    3 +++
 2 files changed, 20 insertions(+), 1 deletions(-)

diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index 2520a6e..a16101a 100644
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -59,7 +59,8 @@ struct bug_entry {
  * appear at runtime.  Use the versions with printk format strings
  * to provide better diagnostics.
  */
-#ifndef __WARN_TAINT
+#if !defined(__WARN_TAINT)
+
 #ifndef __ASSEMBLY__
 extern __printf(3, 4)
 void warn_slowpath_fmt(const char *file, const int line,
@@ -70,15 +71,30 @@ void warn_slowpath_fmt_taint(const char *file, const int line, unsigned taint,
 extern void warn_slowpath_null(const char *file, const int line);
 #define WANT_WARN_ON_SLOWPATH
 #endif
+
+#ifdef CONFIG_PRINTK
 #define __WARN()		warn_slowpath_null(__FILE__, __LINE__)
 #define __WARN_printf(arg...)	warn_slowpath_fmt(__FILE__, __LINE__, arg)
 #define __WARN_printf_taint(taint, arg...)				\
 	warn_slowpath_fmt_taint(__FILE__, __LINE__, taint, arg)
 #else
+#define __WARN()		do {} while (0)
+#define __WARN_printf(fmt, ...)			\
+do {						\
+	if (0)					\
+		printk(fmt, ##__VA_ARGS__);	\
+} while (0)
+#define __WARN_printf_taint(taint, fmt, ...)	\
+	__WARN_printf(fmt, ##__VA_ARGS__)
+#endif
+
+#else
+
 #define __WARN()		__WARN_TAINT(TAINT_WARN)
 #define __WARN_printf(arg...)	do { printk(arg); __WARN(); } while (0)
 #define __WARN_printf_taint(taint, arg...)				\
 	do { printk(arg); __WARN_TAINT(taint); } while (0)
+
 #endif
 
 #ifndef WARN_ON
diff --git a/kernel/panic.c b/kernel/panic.c
index 8ed89a1..bc57785 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -396,6 +396,7 @@ struct slowpath_args {
 	va_list args;
 };
 
+#ifdef CONFIG_PRINTK
 static void warn_slowpath_common(const char *file, int line, void *caller,
 				 unsigned taint, struct slowpath_args *args)
 {
@@ -449,6 +450,8 @@ void warn_slowpath_null(const char *file, int line)
 EXPORT_SYMBOL(warn_slowpath_null);
 #endif
 
+#endif
+
 #ifdef CONFIG_CC_STACKPROTECTOR
 
 /*