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Commit 0e39ac44 authored by Mathieu Desnoyers's avatar Mathieu Desnoyers Committed by Ingo Molnar
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tracing, Text Edit Lock - Architecture Independent Code 



This is an architecture independant synchronization around kernel text
modifications through use of a global mutex.

A mutex has been chosen so that kprobes, the main user of this, can sleep
during memory allocation between the memory read of the instructions it
must replace and the memory write of the breakpoint.

Other user of this interface: immediate values.

Paravirt and alternatives are always done when SMP is inactive, so there
is no need to use locks.

Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
LKML-Reference: <49B142D8.7020601@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent f0ef0398

include/linux/memory.h

+6 −0
Original line number Diff line number Diff line
@@ -99,4 +99,10 @@ enum mem_add_context { BOOT, HOTPLUG }; 
#define hotplug_memory_notifier(fn, pri) do { } while (0)

#endif



/*

 * Kernel text modification mutex, used for code patching. Users of this lock

 * can sleep.

 */

extern struct mutex text_mutex;



#endif /* _LINUX_MEMORY_H_ */

mm/memory.c

+10 −0
Original line number Diff line number Diff line
@@ -48,6 +48,8 @@ 
#include <linux/rmap.h>

#include <linux/module.h>

#include <linux/delayacct.h>

#include <linux/kprobes.h>

#include <linux/mutex.h>

#include <linux/init.h>

#include <linux/writeback.h>

#include <linux/memcontrol.h>
@@ -99,6 +101,14 @@ int randomize_va_space __read_mostly = 
					2;

#endif



/*

 * mutex protecting text section modification (dynamic code patching).

 * some users need to sleep (allocating memory...) while they hold this lock.

 *

 * NOT exported to modules - patching kernel text is a really delicate matter.

 */

DEFINE_MUTEX(text_mutex);



static int __init disable_randmaps(char *s)

{

	randomize_va_space = 0;