bpf: Add a common helper bpf_copy_to_user()

Add a common helper bpf_copy_to_user(), which will be used at multiple
places.
No functional change.
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230709025630.3735-8-laoar.shao@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/syscall.c

@@ -3295,6 +3295,25 @@ static void bpf_raw_tp_link_show_fdinfo(const struct bpf_link *link,
 		   raw_tp_link->btp->tp->name);
 }
 
+static int bpf_copy_to_user(char __user *ubuf, const char *buf, u32 ulen,
+			    u32 len)
+{
+	if (ulen >= len + 1) {
+		if (copy_to_user(ubuf, buf, len + 1))
+			return -EFAULT;
+	} else {
+		char zero = '\0';
+
+		if (copy_to_user(ubuf, buf, ulen - 1))
+			return -EFAULT;
+		if (put_user(zero, ubuf + ulen - 1))
+			return -EFAULT;
+		return -ENOSPC;
+	}
+
+	return 0;
+}
+
 static int bpf_raw_tp_link_fill_link_info(const struct bpf_link *link,
 					  struct bpf_link_info *info)
 {
@@ -3313,20 +3332,7 @@ static int bpf_raw_tp_link_fill_link_info(const struct bpf_link *link,
 	if (!ubuf)
 		return 0;
 
-	if (ulen >= tp_len + 1) {
-		if (copy_to_user(ubuf, tp_name, tp_len + 1))
-			return -EFAULT;
-	} else {
-		char zero = '\0';
-
-		if (copy_to_user(ubuf, tp_name, ulen - 1))
-			return -EFAULT;
-		if (put_user(zero, ubuf + ulen - 1))
-			return -EFAULT;
-		return -ENOSPC;
-	}
-
-	return 0;
+	return bpf_copy_to_user(ubuf, tp_name, ulen, tp_len);
 }
 
 static const struct bpf_link_ops bpf_raw_tp_link_lops = {