[PATCH v4 bpf-next 08/11] bpf: Add bpf_perf_link_fill_common()

[Yafang Shao <laoar.shao@gmail.com>]

Add a new helper bpf_perf_link_fill_common(), which will be used by
perf_link based tracepoint, kprobe and uprobe.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 kernel/bpf/syscall.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 6af003d..db9b500 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3306,6 +3306,40 @@ static void bpf_perf_link_dealloc(struct bpf_link *link)
 	kfree(perf_link);
 }
 
+static int bpf_perf_link_fill_common(const struct perf_event *event,
+				     char __user *uname, u32 ulen,
+				     u64 *probe_offset, u64 *probe_addr,
+				     u32 *fd_type)
+{
+	const char *buf;
+	u32 prog_id;
+	size_t len;
+	int err;
+
+	if (!ulen ^ !uname)
+		return -EINVAL;
+	if (!uname)
+		return 0;
+
+	err = bpf_get_perf_event_info(event, &prog_id, fd_type, &buf,
+				      probe_offset, probe_addr);
+	if (err)
+		return err;
+
+	len = strlen(buf);
+	if (buf) {
+		err = bpf_copy_to_user(uname, buf, ulen, len);
+		if (err)
+			return err;
+	} else {
+		char zero = '\0';
+
+		if (put_user(zero, uname))
+			return -EFAULT;
+	}
+	return 0;
+}
+
 static const struct bpf_link_ops bpf_perf_link_lops = {
 	.release = bpf_perf_link_release,
 	.dealloc = bpf_perf_link_dealloc,
-- 
1.8.3.1