Subject: [PATCH v2 bpf-next 07/12] bpf: attach raw_tp program with BTF via type name

From: Alexei Starovoitov <[email-masked]>
Date: Wed, 9 Oct 2019 21:14:58 -0700

BTF type id specified at program load time has all
necessary information to attach that program to raw tracepoint.
Use kernel type name to find raw tracepoint.

Signed-off-by: Alexei Starovoitov <[email-masked]>
---
 kernel/bpf/syscall.c | 67 +++++++++++++++++++++++++++++---------------
 1 file changed, 44 insertions(+), 23 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index b56c482c9760..03f36e73d84a 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1816,17 +1816,49 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
 	struct bpf_raw_tracepoint *raw_tp;
 	struct bpf_raw_event_map *btp;
 	struct bpf_prog *prog;
-	char tp_name[128];
+	const char *tp_name;
+	char buf[128];
 	int tp_fd, err;
 
-	if (strncpy_from_user(tp_name, u64_to_user_ptr(attr->raw_tracepoint.name),
-			      sizeof(tp_name) - 1) < 0)
-		return -EFAULT;
-	tp_name[sizeof(tp_name) - 1] = 0;
+	prog = bpf_prog_get(attr->raw_tracepoint.prog_fd);
+	if (IS_ERR(prog))
+		return PTR_ERR(prog);
+
+	if (prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT &&
+	    prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE) {
+		err = -EINVAL;
+		goto out_put_prog;
+	}
+
+	if (prog->type == BPF_PROG_TYPE_RAW_TRACEPOINT &&
+	    prog->aux->attach_btf_id) {
+		if (attr->raw_tracepoint.name) {
+			/* raw_tp name should not be specified in raw_tp
+			 * programs that were verified via in-kernel BTF info
+			 */
+			err = -EINVAL;
+			goto out_put_prog;
+		}
+		/* raw_tp name is taken from type name instead */
+		tp_name = kernel_type_name(prog->aux->attach_btf_id);
+		/* skip the prefix */
+		tp_name += sizeof("btf_trace_") - 1;
+	} else {
+		if (strncpy_from_user(buf,
+				      u64_to_user_ptr(attr->raw_tracepoint.name),
+				      sizeof(buf) - 1) < 0) {
+			err = -EFAULT;
+			goto out_put_prog;
+		}
+		buf[sizeof(buf) - 1] = 0;
+		tp_name = buf;
+	}
 
 	btp = bpf_get_raw_tracepoint(tp_name);
-	if (!btp)
-		return -ENOENT;
+	if (!btp) {
+		err = -ENOENT;
+		goto out_put_prog;
+	}
 
 	raw_tp = kzalloc(sizeof(*raw_tp), GFP_USER);
 	if (!raw_tp) {
@@ -1834,38 +1866,27 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
 		goto out_put_btp;
 	}
 	raw_tp->btp = btp;
-
-	prog = bpf_prog_get(attr->raw_tracepoint.prog_fd);
-	if (IS_ERR(prog)) {
-		err = PTR_ERR(prog);
-		goto out_free_tp;
-	}
-	if (prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT &&
-	    prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE) {
-		err = -EINVAL;
-		goto out_put_prog;
-	}
+	raw_tp->prog = prog;
 
 	err = bpf_probe_register(raw_tp->btp, prog);
 	if (err)
-		goto out_put_prog;
+		goto out_free_tp;
 
-	raw_tp->prog = prog;
 	tp_fd = anon_inode_getfd("bpf-raw-tracepoint", &bpf_raw_tp_fops, raw_tp,
 				 O_CLOEXEC);
 	if (tp_fd < 0) {
 		bpf_probe_unregister(raw_tp->btp, prog);
 		err = tp_fd;
-		goto out_put_prog;
+		goto out_free_tp;
 	}
 	return tp_fd;
 
-out_put_prog:
-	bpf_prog_put(prog);
 out_free_tp:
 	kfree(raw_tp);
 out_put_btp:
 	bpf_put_raw_tracepoint(btp);
+out_put_prog:
+	bpf_prog_put(prog);
 	return err;
 }
 
-- 
2.23.0