fprobe: Pass return address to the handlers

Pass return address as 'ret_ip' to the fprobe entry and return handlers
so that the fprobe user handler can get the reutrn address without
analyzing arch-dependent pt_regs.

Link: https://lore.kernel.org/all/168507467664.913472.11642316698862778600.stgit@mhiramat.roam.corp.google.com/

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

include/linux/fprobe.h

@@ -35,9 +35,11 @@ struct fprobe {
 	int			nr_maxactive;
 
 	int (*entry_handler)(struct fprobe *fp, unsigned long entry_ip,
-			     struct pt_regs *regs, void *entry_data);
+			     unsigned long ret_ip, struct pt_regs *regs,
+			     void *entry_data);
 	void (*exit_handler)(struct fprobe *fp, unsigned long entry_ip,
-			     struct pt_regs *regs, void *entry_data);
+			     unsigned long ret_ip, struct pt_regs *regs,
+			     void *entry_data);
 };
 
 /* This fprobe is soft-disabled. */

include/linux/rethook.h

@@ -14,7 +14,7 @@
 
 struct rethook_node;
 
-typedef void (*rethook_handler_t) (struct rethook_node *, void *, struct pt_regs *);
+typedef void (*rethook_handler_t) (struct rethook_node *, void *, unsigned long, struct pt_regs *);
 
 /**
  * struct rethook - The rethook management data structure.

kernel/kprobes.c

@@ -2127,6 +2127,7 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
 NOKPROBE_SYMBOL(pre_handler_kretprobe);
 
 static void kretprobe_rethook_handler(struct rethook_node *rh, void *data,
+				      unsigned long ret_addr,
 				      struct pt_regs *regs)
 {
 	struct kretprobe *rp = (struct kretprobe *)data;

kernel/trace/bpf_trace.c

@@ -2642,7 +2642,8 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
 
 static int
 kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,
-			  struct pt_regs *regs, void *data)
+			  unsigned long ret_ip, struct pt_regs *regs,
+			  void *data)
 {
 	struct bpf_kprobe_multi_link *link;
 
@@ -2653,7 +2654,8 @@ kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,
 
 static void
 kprobe_multi_link_exit_handler(struct fprobe *fp, unsigned long fentry_ip,
-			       struct pt_regs *regs, void *data)
+			       unsigned long ret_ip, struct pt_regs *regs,
+			       void *data)
 {
 	struct bpf_kprobe_multi_link *link;
 

kernel/trace/fprobe.c

@@ -46,7 +46,7 @@ static inline void __fprobe_handler(unsigned long ip, unsigned long parent_ip,
 	}
 
 	if (fp->entry_handler)
-		ret = fp->entry_handler(fp, ip, ftrace_get_regs(fregs), entry_data);
+		ret = fp->entry_handler(fp, ip, parent_ip, ftrace_get_regs(fregs), entry_data);
 
 	/* If entry_handler returns !0, nmissed is not counted. */
 	if (rh) {
@@ -112,7 +112,7 @@ static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip,
 }
 
 static void fprobe_exit_handler(struct rethook_node *rh, void *data,
-				struct pt_regs *regs)
+				unsigned long ret_ip, struct pt_regs *regs)
 {
 	struct fprobe *fp = (struct fprobe *)data;
 	struct fprobe_rethook_node *fpr;
@@ -133,7 +133,7 @@ static void fprobe_exit_handler(struct rethook_node *rh, void *data,
 		return;
 	}
 
-	fp->exit_handler(fp, fpr->entry_ip, regs,
+	fp->exit_handler(fp, fpr->entry_ip, ret_ip, regs,
 			 fp->entry_data_size ? (void *)fpr->data : NULL);
 	ftrace_test_recursion_unlock(bit);
 }

kernel/trace/rethook.c

@@ -301,7 +301,8 @@ unsigned long rethook_trampoline_handler(struct pt_regs *regs,
 			break;
 		handler = READ_ONCE(rhn->rethook->handler);
 		if (handler)
-			handler(rhn, rhn->rethook->data, regs);
+			handler(rhn, rhn->rethook->data,
+				correct_ret_addr, regs);
 
 		if (first == node)
 			break;

lib/test_fprobe.c

@@ -39,7 +39,8 @@ static noinline u32 fprobe_selftest_nest_target(u32 value, u32 (*nest)(u32))
 }
 
 static notrace int fp_entry_handler(struct fprobe *fp, unsigned long ip,
-				     struct pt_regs *regs, void *data)
+				    unsigned long ret_ip,
+				    struct pt_regs *regs, void *data)
 {
 	KUNIT_EXPECT_FALSE(current_test, preemptible());
 	/* This can be called on the fprobe_selftest_target and the fprobe_selftest_target2 */
@@ -57,6 +58,7 @@ static notrace int fp_entry_handler(struct fprobe *fp, unsigned long ip,
 }
 
 static notrace void fp_exit_handler(struct fprobe *fp, unsigned long ip,
+				    unsigned long ret_ip,
 				    struct pt_regs *regs, void *data)
 {
 	unsigned long ret = regs_return_value(regs);
@@ -78,14 +80,16 @@ static notrace void fp_exit_handler(struct fprobe *fp, unsigned long ip,
 }
 
 static notrace int nest_entry_handler(struct fprobe *fp, unsigned long ip,
-				     struct pt_regs *regs, void *data)
+				      unsigned long ret_ip,
+				      struct pt_regs *regs, void *data)
 {
 	KUNIT_EXPECT_FALSE(current_test, preemptible());
 	return 0;
 }
 
 static notrace void nest_exit_handler(struct fprobe *fp, unsigned long ip,
-				    struct pt_regs *regs, void *data)
+				      unsigned long ret_ip,
+				      struct pt_regs *regs, void *data)
 {
 	KUNIT_EXPECT_FALSE(current_test, preemptible());
 	KUNIT_EXPECT_EQ(current_test, ip, target_nest_ip);

samples/fprobe/fprobe_example.c

@@ -49,6 +49,7 @@ static void show_backtrace(void)
 }
 
 static int sample_entry_handler(struct fprobe *fp, unsigned long ip,
+				unsigned long ret_ip,
 				struct pt_regs *regs, void *data)
 {
 	if (use_trace)
@@ -65,10 +66,11 @@ static int sample_entry_handler(struct fprobe *fp, unsigned long ip,
 	return 0;
 }
 
-static void sample_exit_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs,
+static void sample_exit_handler(struct fprobe *fp, unsigned long ip,
+				unsigned long ret_ip, struct pt_regs *regs,
 				void *data)
 {
-	unsigned long rip = instruction_pointer(regs);
+	unsigned long rip = ret_ip;
 
 	if (use_trace)
 		/*