linux-kernel - [RFC] Sectionized printk data

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Date:	Mon, 04 Feb 2008 16:48:34 +0100
From:	Johannes Weiner <hannes@...urebad.de>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:	Sam Ravnborg <sam@...nborg.org>
Subject: [RFC] Sectionized printk data

Hi,

current approaches to have printk format strings in the corresponding
data section to the function they appear in look like the following (at
least what I have seen so far):

int __init some_function(void)
{
	static char errmsg[] __initdata = "failure %s in %s\n";

        [...]
        printk(errmsg);
        [...]
}

The attached patch allows something along the lines:

int __init some_function(void)
{
        [...]
        pr_init(KERN_WARNING "failure %s in %s\n", ...);
        [...]
}

Another idea I had was to make printk a macro that figures out the
section of the surrounding function and then moves the data
automatically when it is a literal, but I couldn't find mechanisms that
allow this.  Anyone of you got an idea?

What do you think in general?

	Hannes

---
From: Johannes Weiner <hannes@...urebad.de>

Sectionized printk wrappers

Introduce printk wrappers that place format string literals in init/exit
data sections.

Signed-off-by: Johannes Weiner <hannes@...urebad.de>
---
The place for these wrappers is probably very wrong.  Suggestions
welcome.

	<Imagine diff-stat here>

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index ff356b2..6a1355d 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -192,7 +192,22 @@ static inline int __cold printk(const char *s, ...) { return 0; }
 static inline int log_buf_get_len(void) { return 0; }
 static inline int log_buf_read(int idx) { return 0; }
 static inline int log_buf_copy(char *dest, int idx, int len) { return 0; }
-#endif
+
+/* Sectionized printk constant data */
+#include <linux/init.h>
+#define pr_section(sec, fmt, args...) ({		\
+	static const char __fmt[] sec = fmt;		\
+	printk(__fmt, ## args);				\
+})
+#define pr_init(fmt, args)	pr_section(__initdata, fmt, ## args)
+#define pr_exit(fmt, args)	pr_section(__exitdata, fmt, ## args)
+#define pr_devinit(fmt, args)	pr_section(__devinitdata, fmt, ## args)
+#define pr_devexit(fmt, args)	pr_section(__devexitdata, fmt, ## args)
+#define pr_cpuinit(fmt, args)	pr_section(__cpuinitdata, fmt, ## args)
+#define pr_cpuexit(fmt, args)	pr_section(__cpuexitdata, fmt, ## args)
+#define pr_meminit(fmt, args)	pr_section(__meminitdata, fmt, ## args)
+#define pr_memexit(fmt, args)	pr_section(__memexitdata, fmt, ## args)
+#endif /* CONFIG_PRINTK */
 
 extern void __attribute__((format(printf, 1, 2)))
 	early_printk(const char *fmt, ...);
--
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