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authorMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>2009-03-06 10:35:52 -0500
committerIngo Molnar <mingo@elte.hu>2009-03-06 16:48:59 +0100
commit0e39ac444636ff5be39b26f1cb56d79594654dda (patch)
tree35ba33c22dc1d0a371570a6bd34a617a8cd68e8b
parentf0ef03985130287c6c84ebe69416cf790e6cc00e (diff)
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: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> LKML-Reference: <49B142D8.7020601@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--include/linux/memory.h6
-rw-r--r--mm/memory.c10
2 files changed, 16 insertions, 0 deletions
diff --git a/include/linux/memory.h b/include/linux/memory.h
index 3fdc10806d3..86a6c0f0518 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -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_ */
diff --git a/mm/memory.c b/mm/memory.c
index baa999e87cd..05fab3bc5b4 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -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;