kprobes += function-return probes

@@ -25,6 +25,9 @@
  *		Rusty Russell).
  * 2004-July	Suparna Bhattacharya <[email protected]> added jumper probes
  *		interface to access function arguments.
+ * 2005-Mar     Hien Nguyen <[email protected]> and Jim Keniston
+ *		<[email protected]>  Added function-return probes, aka exit
+ *		probes.
  */
 #include <linux/config.h>
 #include <linux/list.h>

@@ -34,12 +37,15 @@
 
 struct kprobe;
 struct pt_regs;
+struct retprobe_instance;
 typedef int (*kprobe_pre_handler_t) (struct kprobe *, struct pt_regs *);
 typedef int (*kprobe_break_handler_t) (struct kprobe *, struct pt_regs *);
 typedef void (*kprobe_post_handler_t) (struct kprobe *, struct pt_regs *,
 				       unsigned long flags);
 typedef int (*kprobe_fault_handler_t) (struct kprobe *, struct pt_regs *,
 				       int trapnr);
+typedef int (*retprobe_handler_t) (struct retprobe_instance *, struct pt_regs *);
+
 struct kprobe {
 	struct hlist_node hlist;
 

@@ -65,6 +71,9 @@
 
 	/* copy of the original instruction */
 	struct arch_specific_insn ainsn;
+	
+	/* point to retprobe */
+	struct retprobe *rp;
 };
 
 /*

@@ -82,6 +91,49 @@
 	kprobe_opcode_t *entry;	/* probe handling code to jump to */
 };
 
+#ifdef arch_supports_retprobes
+extern int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs);
+extern struct task_struct *arch_get_kprobe_task(void *ptr);
+#else 
+#define arch_supports_retprobes		0
+static void retprobe_trampoline(void)
+{
+}
+static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	return 0;
+} 
+#define arch_get_kprobe_task(ptr) ((struct task_struct *)NULL)
+#endif
+/*
+ * Function-return probe -
+ * Note:
+ * User needs to provide a handler function, and initialize maxactive.
+ * maxactive - The maximum number of instances of the probed function that
+ * can be active concurrently. 
+ * nmissed - tracks the number of times the probed function's return was 
+ * ignored, due to maxactive being too low.
+ *
+ */
+struct retprobe {
+	retprobe_handler_t handler;
+	int maxactive;
+	int nmissed;
+	int num_ri_running;
+	int unregistering;
+	struct kprobe *kprobe;
+	struct retprobe_instance *instances;	/* allocated memory */
+	struct list_head free_instances;
+};
+
+struct retprobe_instance {
+	struct list_head list;
+	struct hlist_node hlist;
+	struct retprobe *rp;
+	void *ret_addr;
+	void *stack_addr;
+};
+
 #ifdef CONFIG_KPROBES
 /* Locks kprobe: irq must be disabled */
 void lock_kprobes(void);

@@ -110,6 +162,14 @@
 void unregister_jprobe(struct jprobe *p);
 void jprobe_return(void);
 
+int register_kretprobe(struct kprobe *p, struct retprobe *rp);
+int register_jretprobe(struct jprobe *p, struct retprobe *rp);
+
+struct retprobe_instance *get_free_rp_inst(struct retprobe *rp);
+struct retprobe_instance *get_rp_inst(void *sara);
+void add_retprobe_inst_to_hash(struct retprobe_instance *ri); 
+void kprobe_flush_task(struct task_struct *tk);
+void recycle_retprobe_instance(struct retprobe_instance *ri);
 #else
 static inline int kprobe_running(void)
 {

@@ -132,5 +192,13 @@
 static inline void jprobe_return(void)
 {
 }
+static inline int register_kretprobe(struct kprobe *p, struct retprobe *rp)
+{
+	return -ENOSYS;
+}
+static inline int register_jretprobe(struct jprobe *p, struct retprobe *rp)
+{
+	return -ENOSYS;
+}
 #endif
 #endif				/* _LINUX_KPROBES_H */

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@@ -39,6 +39,7 @@
 #include <linux/kallsyms.h>
 #include <linux/ptrace.h>
 #include <linux/random.h>
+#include <linux/kprobes.h>
 
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>

@@ -371,7 +372,14 @@
 {
 	struct task_struct *tsk = current;
 	struct thread_struct *t = &tsk->thread;
-
+#ifdef CONFIG_KPROBES
+	/* 
+	 * Remove function-return probe instances associated with this task
+	 * and put them back on the free list. Do not insert an exit probe for
+	 * this function, it will be disabled by kprobe_flush_task if you do. 
+	 */
+	kprobe_flush_task(tsk);
+#endif
 	/* The process may have allocated an io port bitmap... nuke it. */
 	if (unlikely(NULL != t->io_bitmap_ptr)) {
 		int cpu = get_cpu();

@@ -395,7 +403,14 @@
 void flush_thread(void)
 {
 	struct task_struct *tsk = current;
-
+#ifdef CONFIG_KPROBES
+	/* 
+	 * Remove function-return probe instances associated with this task
+	 * and put them back on the free list. Do not insert an exit probe for
+	 * this function, it will be disabled by kprobe_flush_task if you do.
+	 */
+	kprobe_flush_task(tsk);
+#endif
 	memset(tsk->thread.debugreg, 0, sizeof(unsigned long)*8);
 	memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));	
 	/*

@@ -39,6 +39,9 @@
 	: (((unsigned long)current_thread_info()) + THREAD_SIZE - (ADDR)))
 
 #define JPROBE_ENTRY(pentry)	(kprobe_opcode_t *)pentry
+#define arch_supports_retprobes 1
+
+asmlinkage void retprobe_trampoline(void) __asm__("retprobe_trampoline");
 
 /* Architecture specific copy of original instruction*/
 struct arch_specific_insn {