tracing, Text Edit Lock - Architecture Independent Code (0e39ac44) · Commits · 戴 / test

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:

Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> LKML-Reference: <49B142D8.7020601@redhat.com> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

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;

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