[PATCH bpf-next 01/13] bpf: Initialize ftrace_managed in bpf_trampoline_get

[Leon Hwang]

A trampoline managed by ftrace is determined by its target, that said
ftrace_managed is already known when the trampoline is initialized. so,
set 'ftrace_managed = tr->ip != 0' in bpf_trampoline_get() instead of
relying on the first regular or tracing_multi attachment to set it.

This makes the backend selection independent of attachment order and keeps
the registration callbacks focused on installing the trampoline.

Assisted-by: Codex:gpt-5.6-sol
Signed-off-by: Leon Hwang <leon.hwang@xxxxxxxxx>
---
 kernel/bpf/trampoline.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index e07af35ed040..8c2c1d1b9094 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -474,18 +474,11 @@ static int register_fentry(struct bpf_trampoline *tr, struct bpf_tramp_image *im
 			   void *data __maybe_unused)
 {
 	void *new_addr = im->image;
-	void *ip = tr->func.addr;
-	unsigned long faddr;
 	int ret;
 
-	faddr = ftrace_location((unsigned long)ip);
-	if (faddr) {
+	if (tr->func.ftrace_managed) {
 		if (!tr->fops)
 			return -ENOTSUPP;
-		tr->func.ftrace_managed = true;
-	}
-
-	if (tr->func.ftrace_managed) {
 		ret = direct_ops_add(tr, new_addr);
 	} else {
 		ret = bpf_trampoline_update_fentry(tr, 0, NULL, new_addr);
@@ -1226,6 +1219,7 @@ struct bpf_trampoline *bpf_trampoline_get(u64 key,
 
 	memcpy(&tr->func.model, &tgt_info->fmodel, sizeof(tgt_info->fmodel));
 	tr->func.addr = (void *)tgt_info->tgt_addr;
+	tr->func.ftrace_managed = tr->ip != 0;
 out:
 	trampoline_unlock(tr);
 	return tr;
@@ -1583,7 +1577,6 @@ static int register_fentry_multi(struct bpf_trampoline *tr, struct bpf_tramp_ima
 	if (bpf_trampoline_use_jmp(tr->flags))
 		addr = ftrace_jmp_set(addr);
 
-	tr->func.ftrace_managed = true;
 	ftrace_hash_add(data->reg, data->entry, ip, addr);
 	tr->cur_image = im;
 	return 0;
-- 
2.55.0