[PATCH] kprobes: no probes on critical path

For Kprobes critical path is the path from debug break exception handler
till the control reaches kprobes exception code.  No probes can be
supported in this path as we will end up in recursion.

This patch prevents this by moving the below function to safe __kprobes
section onto which no probes can be inserted.
Signed-off-by: NAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

include/linux/kprobes.h

@@ -37,6 +37,7 @@
 #include <linux/spinlock.h>
 #include <linux/rcupdate.h>
 
+#ifdef CONFIG_KPROBES
 #include <asm/kprobes.h>
 
 /* kprobe_status settings */
@@ -147,7 +148,6 @@ struct kretprobe_instance {
 	struct task_struct *task;
 };
 
-#ifdef CONFIG_KPROBES
 extern spinlock_t kretprobe_lock;
 extern int arch_prepare_kprobe(struct kprobe *p);
 extern void arch_copy_kprobe(struct kprobe *p);
@@ -195,6 +195,11 @@ void add_rp_inst(struct kretprobe_instance *ri);
 void kprobe_flush_task(struct task_struct *tk);
 void recycle_rp_inst(struct kretprobe_instance *ri);
 #else /* CONFIG_KPROBES */
+
+#define __kprobes	/**/
+struct jprobe;
+struct kretprobe;
+
 static inline struct kprobe *kprobe_running(void)
 {
 	return NULL;

kernel/sys.c

@@ -32,6 +32,7 @@
 
 #include <linux/compat.h>
 #include <linux/syscalls.h>
+#include <linux/kprobes.h>
 
 #include <asm/uaccess.h>
 #include <asm/io.h>
@@ -168,7 +169,7 @@ EXPORT_SYMBOL(notifier_chain_unregister);
  *	of the last notifier function called.
  */
  
-int notifier_call_chain(struct notifier_block **n, unsigned long val, void *v)
+int __kprobes notifier_call_chain(struct notifier_block **n, unsigned long val, void *v)
 {
 	int ret=NOTIFY_DONE;
 	struct notifier_block *nb = *n;