bpf: add bpf_func_t and trampoline helpers

I'll be adding lsm cgroup specific helpers that grab
trampoline mutex.

No functional changes.

Reviewed-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20220628174314.1216643-2-sdf@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 33 insertions, 30 deletions

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 93c7675f0c9e..5466e15be61f 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -410,7 +410,7 @@ static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(struct bpf_prog *prog)
 	}
 }
 
-int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
+static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
 {
 	enum bpf_tramp_prog_type kind;
 	struct bpf_tramp_link *link_exiting;
@@ -418,44 +418,33 @@ int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline
 	int cnt = 0, i;
 
 	kind = bpf_attach_type_to_tramp(link->link.prog);
-	mutex_lock(&tr->mutex);
-	if (tr->extension_prog) {
+	if (tr->extension_prog)
 		/* cannot attach fentry/fexit if extension prog is attached.
 		 * cannot overwrite extension prog either.
 		 */
-		err = -EBUSY;
-		goto out;
-	}
+		return -EBUSY;
 
 	for (i = 0; i < BPF_TRAMP_MAX; i++)
 		cnt += tr->progs_cnt[i];
 
 	if (kind == BPF_TRAMP_REPLACE) {
 		/* Cannot attach extension if fentry/fexit are in use. */
-		if (cnt) {
-			err = -EBUSY;
-			goto out;
-		}
+		if (cnt)
+			return -EBUSY;
 		tr->extension_prog = link->link.prog;
-		err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL,
-					 link->link.prog->bpf_func);
-		goto out;
-	}
-	if (cnt >= BPF_MAX_TRAMP_LINKS) {
-		err = -E2BIG;
-		goto out;
+		return bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL,
+					  link->link.prog->bpf_func);
 	}
-	if (!hlist_unhashed(&link->tramp_hlist)) {
+	if (cnt >= BPF_MAX_TRAMP_LINKS)
+		return -E2BIG;
+	if (!hlist_unhashed(&link->tramp_hlist))
 		/* prog already linked */
-		err = -EBUSY;
-		goto out;
-	}
+		return -EBUSY;
 	hlist_for_each_entry(link_exiting, &tr->progs_hlist[kind], tramp_hlist) {
 		if (link_exiting->link.prog != link->link.prog)
 			continue;
 		/* prog already linked */
-		err = -EBUSY;
-		goto out;
+		return -EBUSY;
 	}
 
 	hlist_add_head(&link->tramp_hlist, &tr->progs_hlist[kind]);
@@ -465,30 +454,44 @@ int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline
 		hlist_del_init(&link->tramp_hlist);
 		tr->progs_cnt[kind]--;
 	}
-out:
+	return err;
+}
+
+int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
+{
+	int err;
+
+	mutex_lock(&tr->mutex);
+	err = __bpf_trampoline_link_prog(link, tr);
 	mutex_unlock(&tr->mutex);
 	return err;
 }
 
-/* bpf_trampoline_unlink_prog() should never fail. */
-int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
+static int __bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
 {
 	enum bpf_tramp_prog_type kind;
 	int err;
 
 	kind = bpf_attach_type_to_tramp(link->link.prog);
-	mutex_lock(&tr->mutex);
 	if (kind == BPF_TRAMP_REPLACE) {
 		WARN_ON_ONCE(!tr->extension_prog);
 		err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP,
 					 tr->extension_prog->bpf_func, NULL);
 		tr->extension_prog = NULL;
-		goto out;
+		return err;
 	}
 	hlist_del_init(&link->tramp_hlist);
 	tr->progs_cnt[kind]--;
-	err = bpf_trampoline_update(tr);
-out:
+	return bpf_trampoline_update(tr);
+}
+
+/* bpf_trampoline_unlink_prog() should never fail. */
+int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
+{
+	int err;
+
+	mutex_lock(&tr->mutex);
+	err = __bpf_trampoline_unlink_prog(link, tr);
 	mutex_unlock(&tr->mutex);
 	return err;
 }