[PATCH] clean up kernel messages

Arrange for all kernel printks to be no-ops. Only available if
CONFIG_EMBEDDED.

This patch saves about 375k on my laptop config and nearly 100k on minimal
configs.

Signed-off-by: Matt Mackall <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/i386/kernel/head.S

···
 	ALIGN
 ignore_int:
 	cld
+#ifdef CONFIG_PRINTK
 	pushl %eax
 	pushl %ecx
 	pushl %edx
···
 	popl %edx
 	popl %ecx
 	popl %eax
+#endif
 	iret
 
 /*

include/linux/kernel.h

···
 extern int kernel_text_address(unsigned long addr);
 extern int session_of_pgrp(int pgrp);
 
+#ifdef CONFIG_PRINTK
 asmlinkage int vprintk(const char *fmt, va_list args)
 	__attribute__ ((format (printf, 1, 0)));
 asmlinkage int printk(const char * fmt, ...)
 	__attribute__ ((format (printf, 1, 2)));
+#else
+static inline int vprintk(const char *s, va_list args)
+	__attribute__ ((format (printf, 1, 0)));
+static inline int vprintk(const char *s, va_list args) { return 0; }
+static inline int printk(const char *s, ...)
+	__attribute__ ((format (printf, 1, 2)));
+static inline int printk(const char *s, ...) { return 0; }
+#endif
 
 unsigned long int_sqrt(unsigned long);
 

init/Kconfig

···
 	   reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
 	   you wait for kallsyms to be fixed.
 
+
+config PRINTK
+	default y
+	bool "Enable support for printk" if EMBEDDED
+	help
+	  This option enables normal printk support. Removing it
+	  eliminates most of the message strings from the kernel image
+	  and makes the kernel more or less silent. As this makes it
+	  very difficult to diagnose system problems, saying N here is
+	  strongly discouraged.
+
 config BUG
 	bool "BUG() support" if EMBEDDED
 	default y

kernel/printk.c

···
  */
 static DEFINE_SPINLOCK(logbuf_lock);
 
-static char __log_buf[__LOG_BUF_LEN];
-static char *log_buf = __log_buf;
-static int log_buf_len = __LOG_BUF_LEN;
-
 #define LOG_BUF_MASK	(log_buf_len-1)
 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
 
···
 static unsigned long log_start;	/* Index into log_buf: next char to be read by syslog() */
 static unsigned long con_start;	/* Index into log_buf: next char to be sent to consoles */
 static unsigned long log_end;	/* Index into log_buf: most-recently-written-char + 1 */
-static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
 
 /*
  *	Array of consoles built from command line options (console=)
···
 
 /* Flag: console code may call schedule() */
 static int console_may_schedule;
+
+#ifdef CONFIG_PRINTK
+
+static char __log_buf[__LOG_BUF_LEN];
+static char *log_buf = __log_buf;
+static int log_buf_len = __LOG_BUF_LEN;
+static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
 
 /*
  *	Setup a list of consoles. Called from init/main.c
···
  * then changes console_loglevel may break. This is because console_loglevel
  * is inspected when the actual printing occurs.
  */
+
 asmlinkage int printk(const char *fmt, ...)
 {
 	va_list args;
···
 }
 EXPORT_SYMBOL(printk);
 EXPORT_SYMBOL(vprintk);
+
+#else
+
+asmlinkage long sys_syslog(int type, char __user * buf, int len)
+{
+	return 0;
+}
+
+int do_syslog(int type, char __user * buf, int len) { return 0; }
+static void call_console_drivers(unsigned long start, unsigned long end) {}
+
+#endif
 
 /**
  * acquire_console_sem - lock the console system for exclusive use.
···
 	return res;
 }
 EXPORT_SYMBOL(unregister_console);
-	
+
 /**
  * tty_write_message - write a message to a certain tty, not just the console.
  *