Subject: [PATCH bpf-next 17/29] bpf: Resolve id in bpf_tramp_id_single

From: Jiri Olsa <[email-masked]>
Date: Thu, 18 Nov 2021 12:24:43 +0100

Moving the id resolving in the bpf_tramp_id_single function
so it's centralized together with the trampoline's allocation
and init.

Signed-off-by: Jiri Olsa <[email-masked]>
---
 include/linux/bpf.h     |  3 ++-
 kernel/bpf/syscall.c    | 21 ++++++---------------
 kernel/bpf/trampoline.c | 18 +++++++++++++++---
 kernel/bpf/verifier.c   |  4 +---
 4 files changed, 24 insertions(+), 22 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 894ee812e213..dda24339e4b1 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -756,7 +756,8 @@ 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);
 struct bpf_tramp_id *bpf_tramp_id_single(const struct bpf_prog *tgt_prog,
-					 struct btf *btf, u32 btf_id);
+					 struct bpf_prog *prog, u32 btf_id,
+					 struct bpf_attach_target_info *tgt_info);
 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 8109b0fc7d2f..0acf6cb0fdc7 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2773,9 +2773,9 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog,
 			goto out_put_prog;
 		}
 
-		id = bpf_tramp_id_single(tgt_prog, NULL, btf_id);
-		if (!id) {
-			err = -ENOMEM;
+		id = bpf_tramp_id_single(tgt_prog, prog, btf_id, NULL);
+		if (IS_ERR(id)) {
+			err = PTR_ERR(id);
 			goto out_put_prog;
 		}
 	}
@@ -2828,9 +2828,9 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog,
 		}
 
 		btf_id = prog->aux->attach_btf_id;
-		id = bpf_tramp_id_single(NULL, prog->aux->attach_btf, btf_id);
-		if (!id) {
-			err = -ENOMEM;
+		id = bpf_tramp_id_single(NULL, prog, btf_id, NULL);
+		if (IS_ERR(id)) {
+			err = PTR_ERR(id);
 			goto out_unlock;
 		}
 	}
@@ -2842,15 +2842,6 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog,
 		 * different from the destination specified at load time, we
 		 * need a new trampoline and a check for compatibility
 		 */
-		struct bpf_attach_target_info tgt_info = {};
-
-		err = bpf_check_attach_target(NULL, prog, tgt_prog, btf_id,
-					      &tgt_info);
-		if (err)
-			goto out_unlock;
-
-		id->addr[0] = (void *) tgt_info.tgt_addr;
-
 		attach = bpf_tramp_attach(id, tgt_prog, prog);
 		if (IS_ERR(attach)) {
 			err = PTR_ERR(attach);
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 4a4ef9396b7e..e6a73088ecee 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -105,18 +105,30 @@ struct bpf_tramp_id *bpf_tramp_id_alloc(u32 max)
 }
 
 struct bpf_tramp_id *bpf_tramp_id_single(const struct bpf_prog *tgt_prog,
-					 struct btf *btf, u32 btf_id)
+					 struct bpf_prog *prog, u32 btf_id,
+					 struct bpf_attach_target_info *tgt_info)
 {
 	struct bpf_tramp_id *id;
 
+	if (!tgt_info) {
+		struct bpf_attach_target_info __tgt_info = {};
+		int err;
+
+		tgt_info = &__tgt_info;
+		err = bpf_check_attach_target(NULL, prog, tgt_prog, btf_id,
+					     tgt_info);
+		if (err)
+			return ERR_PTR(err);
+	}
 	id = bpf_tramp_id_alloc(1);
 	if (!id)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 	if (tgt_prog)
 		id->obj_id = tgt_prog->aux->id;
 	else
-		id->obj_id = btf_obj_id(btf);
+		id->obj_id = btf_obj_id(prog->aux->attach_btf);
 	id->id[0] = btf_id;
+	id->addr[0] = (void *) tgt_info->tgt_addr;
 	id->cnt = 1;
 	return id;
 }
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 9914487f2281..8d56d43489aa 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -13995,12 +13995,10 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 		return -EINVAL;
 	}
 
-	id = bpf_tramp_id_single(NULL, prog->aux->attach_btf, btf_id);
+	id = bpf_tramp_id_single(tgt_prog, prog, btf_id, &tgt_info);
 	if (!id)
 		return -ENOMEM;
 
-	id->addr[0] = (void *) tgt_info.tgt_addr;
-
 	attach = bpf_tramp_attach(id, tgt_prog, prog);
 	if (IS_ERR(attach)) {
 		bpf_tramp_id_free(id);
-- 
2.31.1