linux-kernel - [RFC PATCH 1/3] init.h: Add __init_str / __exit

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Date:	Mon, 23 Jun 2014 00:46:47 +0200
From:	Mathias Krause <minipli@...glemail.com>
To:	linux-kernel@...r.kernel.org
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Joe Perches <joe@...ches.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Jason Baron <jbaron@...hat.com>,
	Mathias Krause <minipli@...glemail.com>
Subject: [RFC PATCH 1/3] init.h: Add __init_str / __exit_str macros

Add macros to be able to mark string literals used in __init / __exit
functions.

Signed-off-by: Mathias Krause <minipli@...glemail.com>
---
 include/linux/init.h |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/include/linux/init.h b/include/linux/init.h
index 2df8e8dd10..0a425b296e 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -35,6 +35,18 @@
  * Don't forget to initialize data not at file scope, i.e. within a function,
  * as gcc otherwise puts the data into the bss section and not into the init
  * section.
+ *
+ * For messages printed in __init / __exit functions the __init_str() /
+ * __exit_str() macros will take care of marking the strings accordingly so
+ * they can be freed, too. Otherwise the strings would resist in memory, even
+ * though they are no longer referenced.
+ *
+ * Use them like this:
+ *
+ * static void __init initme(void)
+ * {
+ *    printk(__init_str(KERN_INFO "I am fully initialized, now\n"));
+ * }
  */
 
 /* These are for everybody (although not all archs will actually
@@ -45,6 +57,12 @@
 #define __exitdata	__section(.exit.data)
 #define __exit_call	__used __section(.exitcall.exit)
 
+/* Those can be used to mark strings used in __init / __exit functions. */
+#define __init_str(str)	__mark_str(str, __UNIQUE_ID(_init_str_), __initconst)
+#define __exit_str(str)	__mark_str(str, __UNIQUE_ID(_exit_str_), __exitdata)
+#define __mark_str(str, var, __section) \
+	({ static const char var[] __section __aligned(1) = str; var; })
+
 /*
  * Some architecture have tool chains which do not handle rodata attributes
  * correctly. For those disable special sections for const, so that other
-- 
1.7.10.4

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