Subject: [PATCH 04/13] kprobe: Add support to register multiple ftrace kretprobes

From: Jiri Olsa <[email-masked]>
Date: Tue, 4 Jan 2022 09:09:34 +0100

Adding support to register kretprobe on multiple addresses within
single kprobe object instance.

The interface stays same as for kprobes, the patch just adds blacklist
check for each address, which is special for kretprobes.

Signed-off-by: Jiri Olsa <[email-masked]>
---
 include/linux/kprobes.h |  1 +
 kernel/kprobes.c        | 46 ++++++++++++++++++++++++++++++++---------
 2 files changed, 37 insertions(+), 10 deletions(-)

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 03fd86ef69cb..a31da6202b5c 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -75,6 +75,7 @@ struct kprobe {
 		kprobe_opcode_t **addrs;
 		unsigned int cnt;
 		struct ftrace_ops ops;
+		bool check_kretprobe;
 	} multi;
 #endif
 
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index e7729e20d85c..04fc411ca30c 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1052,6 +1052,17 @@ static int check_ftrace_location(unsigned long addr, struct kprobe *p)
 	return 0;
 }
 
+static bool in_kretprobe_blacklist(void *addr)
+{
+	int i;
+
+	for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
+		if (kretprobe_blacklist[i].addr == addr)
+			return true;
+	}
+	return false;
+}
+
 #ifdef CONFIG_KPROBES_ON_FTRACE
 static struct ftrace_ops kprobe_ftrace_ops __read_mostly = {
 	.func = kprobe_ftrace_handler,
@@ -1155,7 +1166,8 @@ static int disarm_kprobe_ftrace(struct kprobe *p)
  * - ftrace managed function entry address
  * - kernel core only address
  */
-static unsigned long check_ftrace_addr(unsigned long addr)
+static unsigned long check_ftrace_addr(unsigned long addr,
+				       bool check_kretprobe)
 {
 	int err;
 
@@ -1168,6 +1180,8 @@ static unsigned long check_ftrace_addr(unsigned long addr)
 		return -EINVAL;
 	if (__module_text_address(addr))
 		return -EINVAL;
+	if (check_kretprobe && in_kretprobe_blacklist((void *) addr))
+		return -EINVAL;
 	return 0;
 }
 
@@ -1202,7 +1216,7 @@ static int check_ftrace_multi(struct kprobe *p)
 	preempt_disable();
 
 	for (i = 0; i < cnt; i++) {
-		err = check_ftrace_addr(ips[i]);
+		err = check_ftrace_addr(ips[i], p->multi.check_kretprobe);
 		if (err)
 			break;
 	}
@@ -2188,13 +2202,17 @@ int kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym, unsigned long o
 	return 0;
 }
 
-int register_kretprobe(struct kretprobe *rp)
+static int check_kretprobe_address(struct kretprobe *rp)
 {
 	int ret;
-	struct kretprobe_instance *inst;
-	int i;
 	void *addr;
 
+#ifdef CONFIG_HAVE_KPROBES_MULTI_ON_FTRACE
+	if (rp->kp.multi.cnt) {
+		rp->kp.multi.check_kretprobe = !!kretprobe_blacklist_size;
+		return 0;
+	}
+#endif
 	ret = kprobe_on_func_entry(rp->kp.addr, rp->kp.symbol_name, rp->kp.offset);
 	if (ret)
 		return ret;
@@ -2207,12 +2225,20 @@ int register_kretprobe(struct kretprobe *rp)
 		addr = kprobe_addr(&rp->kp);
 		if (IS_ERR(addr))
 			return PTR_ERR(addr);
-
-		for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
-			if (kretprobe_blacklist[i].addr == addr)
-				return -EINVAL;
-		}
+		if (in_kretprobe_blacklist(addr))
+			return -EINVAL;
 	}
+	return 0;
+}
+
+int register_kretprobe(struct kretprobe *rp)
+{
+	struct kretprobe_instance *inst;
+	int i, ret = 0;
+
+	ret = check_kretprobe_address(rp);
+	if (ret)
+		return ret;
 
 	if (rp->data_size > KRETPROBE_MAX_DATA_SIZE)
 		return -E2BIG;
-- 
2.33.1