Subject: [PATCH bpf-next 16/29] bpf: Add bpf_tramp_id_single function

From: Jiri Olsa <[email-masked]>
Date: Thu, 18 Nov 2021 12:24:42 +0100

Adding bpf_tramp_id_single function as interface to
create trampoline with single ID and grouping together
the trampoline allocation with init that is used on
several places and save us few lines.

Signed-off-by: Jiri Olsa <[email-masked]>
---
 include/linux/bpf.h     |  5 ++---
 kernel/bpf/syscall.c    | 18 +++++++-----------
 kernel/bpf/trampoline.c | 11 ++++++++---
 kernel/bpf/verifier.c   |  3 +--
 4 files changed, 18 insertions(+), 19 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 13e9dcfd47e7..894ee812e213 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -755,9 +755,8 @@ struct bpf_tramp_id *bpf_tramp_id_alloc(u32 cnt);
 void bpf_tramp_id_free(struct bpf_tramp_id *id);
 bool bpf_tramp_id_is_empty(struct bpf_tramp_id *id);
 int bpf_tramp_id_is_equal(struct bpf_tramp_id *a, struct bpf_tramp_id *b);
-void bpf_tramp_id_init(struct bpf_tramp_id *id,
-		       const struct bpf_prog *tgt_prog,
-		       struct btf *btf, u32 btf_id);
+struct bpf_tramp_id *bpf_tramp_id_single(const struct bpf_prog *tgt_prog,
+					 struct btf *btf, u32 btf_id);
 int bpf_trampoline_link_prog(struct bpf_tramp_node *node, struct bpf_trampoline *tr);
 int bpf_trampoline_unlink_prog(struct bpf_tramp_node *node, struct bpf_trampoline *tr);
 void bpf_trampoline_put(struct bpf_trampoline *tr);
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 0ae3b5b7419a..8109b0fc7d2f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2766,12 +2766,6 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog,
 			goto out_put_prog;
 		}
 
-		id = bpf_tramp_id_alloc(1);
-		if (!id) {
-			err = -ENOMEM;
-			goto out_put_prog;
-		}
-
 		tgt_prog = bpf_prog_get(tgt_prog_fd);
 		if (IS_ERR(tgt_prog)) {
 			err = PTR_ERR(tgt_prog);
@@ -2779,7 +2773,11 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog,
 			goto out_put_prog;
 		}
 
-		bpf_tramp_id_init(id, tgt_prog, NULL, btf_id);
+		id = bpf_tramp_id_single(tgt_prog, NULL, btf_id);
+		if (!id) {
+			err = -ENOMEM;
+			goto out_put_prog;
+		}
 	}
 
 	link = kzalloc(sizeof(*link), GFP_USER);
@@ -2829,14 +2827,12 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog,
 			goto out_unlock;
 		}
 
-		id = bpf_tramp_id_alloc(1);
+		btf_id = prog->aux->attach_btf_id;
+		id = bpf_tramp_id_single(NULL, prog->aux->attach_btf, btf_id);
 		if (!id) {
 			err = -ENOMEM;
 			goto out_unlock;
 		}
-
-		btf_id = prog->aux->attach_btf_id;
-		bpf_tramp_id_init(id, NULL, prog->aux->attach_btf, btf_id);
 	}
 
 	if (!prog->aux->dst_attach ||
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index d9675d619963..4a4ef9396b7e 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -104,16 +104,21 @@ struct bpf_tramp_id *bpf_tramp_id_alloc(u32 max)
 	return id;
 }
 
-void bpf_tramp_id_init(struct bpf_tramp_id *id,
-		       const struct bpf_prog *tgt_prog,
-		       struct btf *btf, u32 btf_id)
+struct bpf_tramp_id *bpf_tramp_id_single(const struct bpf_prog *tgt_prog,
+					 struct btf *btf, u32 btf_id)
 {
+	struct bpf_tramp_id *id;
+
+	id = bpf_tramp_id_alloc(1);
+	if (!id)
+		return NULL;
 	if (tgt_prog)
 		id->obj_id = tgt_prog->aux->id;
 	else
 		id->obj_id = btf_obj_id(btf);
 	id->id[0] = btf_id;
 	id->cnt = 1;
+	return id;
 }
 
 void bpf_tramp_id_free(struct bpf_tramp_id *id)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 56c518efa2d2..9914487f2281 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -13995,11 +13995,10 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 		return -EINVAL;
 	}
 
-	id = bpf_tramp_id_alloc(1);
+	id = bpf_tramp_id_single(NULL, prog->aux->attach_btf, btf_id);
 	if (!id)
 		return -ENOMEM;
 
-	bpf_tramp_id_init(id, tgt_prog, prog->aux->attach_btf, btf_id);
 	id->addr[0] = (void *) tgt_info.tgt_addr;
 
 	attach = bpf_tramp_attach(id, tgt_prog, prog);
-- 
2.31.1