Re: [PATCH] clean up kernel messages

[Andrew Morton]

Matt Mackall <mpm@xxxxxxxxxxx> wrote:
>
> This patch tidies up those annoying kernel messages. A typical kernel
>  boot now looks like this:
> 
>  Loading Linux... Uncompressing kernel...
>  #
> 
>  See? Much nicer. This patch saves about 375k on my laptop config and
>  nearly 100k on minimal configs.
> 

heh.  Please take a look at
http://www.uwsg.iu.edu/hypermail/linux/kernel/0004.2/0709.html, see if
Graham did anything which you missed.

One problem was that

	printk("foo");

will still cause the string "foo\0" to appear in the kernel image.  That
was fixed in later gcc's, but it would be interesting to know which
compilers get it right.

> 
>  Index: af/include/linux/kernel.h
>  ===================================================================
>  --- af.orig/include/linux/kernel.h	2005-04-01 00:32:18.000000000 -0800
>  +++ af/include/linux/kernel.h	2005-04-01 10:38:43.000000000 -0800
>  @@ -115,10 +115,19 @@ extern int __kernel_text_address(unsigne
>   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

Actually printk() is supposed to return the number of chars which it
printed.  So if someone is doing:

	while (len < 40)
		len += printk("something");

you've gone and made them lock up.

But I think the number of places where we examine the printk return value
is near zero.

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