[PATCHv5 bpf-next 07/28] bpf: Add bpf_trampoline_add/remove_prog functions

[Jiri Olsa <jolsa@kernel.org>]

Separate bpf_trampoline_add/remove_prog functions from
__bpf_trampoline_link/unlink functions to be able to add/remove
trampoline programs without the image being updated in following
changes. No functional change is intended.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 kernel/bpf/trampoline.c | 108 +++++++++++++++++++++++-----------------
 1 file changed, 61 insertions(+), 47 deletions(-)

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index ad4ddb62d22f..71e5a121c2fd 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -820,41 +820,16 @@ static int bpf_freplace_check_tgt_prog(struct bpf_prog *tgt_prog)
 	return 0;
 }
 
-static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link,
-				      struct bpf_trampoline *tr,
-				      struct bpf_prog *tgt_prog,
-				      const struct bpf_trampoline_ops *ops,
-				      void *data)
+static int bpf_trampoline_add_prog(struct bpf_trampoline *tr,
+				   struct bpf_tramp_link *link,
+				   int cnt)
 {
 	struct bpf_fsession_link *fslink = NULL;
 	enum bpf_tramp_prog_type kind;
 	struct bpf_tramp_link *link_exiting;
 	struct hlist_head *prog_list;
-	int err = 0;
-	int cnt = 0, i;
 
 	kind = bpf_attach_type_to_tramp(link->link.prog);
-	if (tr->extension_prog)
-		/* cannot attach fentry/fexit if extension prog is attached.
-		 * cannot overwrite extension prog either.
-		 */
-		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)
-			return -EBUSY;
-		err = bpf_freplace_check_tgt_prog(tgt_prog);
-		if (err)
-			return err;
-		tr->extension_prog = link->link.prog;
-		return bpf_arch_text_poke(tr->func.addr, BPF_MOD_NOP,
-					  BPF_MOD_JUMP, NULL,
-					  link->link.prog->bpf_func);
-	}
 	if (kind == BPF_TRAMP_FSESSION) {
 		prog_list = &tr->progs_hlist[BPF_TRAMP_FENTRY];
 		cnt++;
@@ -882,17 +857,64 @@ static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link,
 	} else {
 		tr->progs_cnt[kind]++;
 	}
-	err = bpf_trampoline_update(tr, true /* lock_direct_mutex */, ops, data);
-	if (err) {
-		hlist_del_init(&link->tramp_hlist);
-		if (kind == BPF_TRAMP_FSESSION) {
-			tr->progs_cnt[BPF_TRAMP_FENTRY]--;
-			hlist_del_init(&fslink->fexit.tramp_hlist);
-			tr->progs_cnt[BPF_TRAMP_FEXIT]--;
-		} else {
-			tr->progs_cnt[kind]--;
-		}
+	return 0;
+}
+
+static void bpf_trampoline_remove_prog(struct bpf_trampoline *tr,
+				    struct bpf_tramp_link *link)
+{
+	struct bpf_fsession_link *fslink;
+	enum bpf_tramp_prog_type kind;
+
+	kind = bpf_attach_type_to_tramp(link->link.prog);
+	if (kind == BPF_TRAMP_FSESSION) {
+		fslink = container_of(link, struct bpf_fsession_link, link.link);
+		hlist_del_init(&fslink->fexit.tramp_hlist);
+		tr->progs_cnt[BPF_TRAMP_FEXIT]--;
+		kind = BPF_TRAMP_FENTRY;
+	}
+	hlist_del_init(&link->tramp_hlist);
+	tr->progs_cnt[kind]--;
+}
+
+static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link,
+				      struct bpf_trampoline *tr,
+				      struct bpf_prog *tgt_prog,
+				      const struct bpf_trampoline_ops *ops,
+				      void *data)
+{
+	enum bpf_tramp_prog_type kind;
+	int err = 0;
+	int cnt = 0, i;
+
+	kind = bpf_attach_type_to_tramp(link->link.prog);
+	if (tr->extension_prog)
+		/* cannot attach fentry/fexit if extension prog is attached.
+		 * cannot overwrite extension prog either.
+		 */
+		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)
+			return -EBUSY;
+		err = bpf_freplace_check_tgt_prog(tgt_prog);
+		if (err)
+			return err;
+		tr->extension_prog = link->link.prog;
+		return bpf_arch_text_poke(tr->func.addr, BPF_MOD_NOP,
+					  BPF_MOD_JUMP, NULL,
+					  link->link.prog->bpf_func);
 	}
+	err = bpf_trampoline_add_prog(tr, link, cnt);
+	if (err)
+		return err;
+	err = bpf_trampoline_update(tr, true /* lock_direct_mutex */, ops, data);
+	if (err)
+		bpf_trampoline_remove_prog(tr, link);
 	return err;
 }
 
@@ -927,16 +949,8 @@ static int __bpf_trampoline_unlink_prog(struct bpf_tramp_link *link,
 		guard(mutex)(&tgt_prog->aux->ext_mutex);
 		tgt_prog->aux->is_extended = false;
 		return err;
-	} else if (kind == BPF_TRAMP_FSESSION) {
-		struct bpf_fsession_link *fslink =
-			container_of(link, struct bpf_fsession_link, link.link);
-
-		hlist_del_init(&fslink->fexit.tramp_hlist);
-		tr->progs_cnt[BPF_TRAMP_FEXIT]--;
-		kind = BPF_TRAMP_FENTRY;
 	}
-	hlist_del_init(&link->tramp_hlist);
-	tr->progs_cnt[kind]--;
+	bpf_trampoline_remove_prog(tr, link);
 	return bpf_trampoline_update(tr, true /* lock_direct_mutex */, ops, data);
 }
 
-- 
2.53.0