From 09ec92d707236e4af9484092e470078c238531d5 Mon Sep 17 00:00:00 2001 From: Leon Hwang Date: Fri, 16 Oct 2026 22:20:13 +0800 Subject: [PATCH 1/2] bpf: Initialize ftrace_managed in bpf_trampoline_get() 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. No functional change intended. Signed-off-by: Leon Hwang Signed-off-by: Alexei Starovoitov Acked-by: Jiri Olsa Link: https://patch.msgid.link/20261016142014.12420-2-leon.hwang@linux.dev --- 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 24edb59238f3..17f2a8133f61 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -475,18 +475,11 @@ 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); @@ -1286,6 +1279,7 @@ 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; @@ -1649,7 +1643,6 @@ 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; From b443a4578a0d14ab07802aea4bcd93da1c31a592 Mon Sep 17 00:00:00 2001 From: Leon Hwang Date: Fri, 16 Oct 2026 22:20:14 +0800 Subject: [PATCH 2/2] bpf: Drop unnecessary ftrace_location() in register/unregister/modify_fentry_multi() Since 'tr->ip' is already a 'ftrace_location()'-ed IP in bpf_trampoline_lookup(), it is unnecessary to call ftrace_location() again in register/unregister/modify_fentry_multi(). No functional changes intended. Signed-off-by: Leon Hwang Signed-off-by: Alexei Starovoitov Acked-by: Jiri Olsa Link: https://patch.msgid.link/20261016142014.12420-3-leon.hwang@linux.dev --- kernel/bpf/trampoline.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index 17f2a8133f61..21d460866dfe 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -1629,8 +1629,8 @@ static void ftrace_hash_add(struct ftrace_hash *hash, struct ftrace_func_entry * static int register_fentry_multi(struct bpf_trampoline *tr, struct bpf_tramp_image *im, void *ptr) { unsigned long addr = (unsigned long) im->image; - unsigned long ip = ftrace_location(tr->ip); struct bpf_tracing_multi_data *data = ptr; + unsigned long ip = tr->ip; /* * Different BTF ids get different trampolines, but they can still @@ -1651,13 +1651,12 @@ static int register_fentry_multi(struct bpf_trampoline *tr, struct bpf_tramp_ima static int unregister_fentry_multi(struct bpf_trampoline *tr, u32 orig_flags, void *ptr) { unsigned long addr = (unsigned long) tr->cur_image->image; - unsigned long ip = ftrace_location(tr->ip); struct bpf_tracing_multi_data *data = ptr; if (bpf_trampoline_use_jmp(tr->flags)) addr = ftrace_jmp_set(addr); - ftrace_hash_add(data->unreg, data->entry, ip, addr); + ftrace_hash_add(data->unreg, data->entry, tr->ip, addr); tr->cur_image = NULL; return 0; } @@ -1666,13 +1665,12 @@ static int modify_fentry_multi(struct bpf_trampoline *tr, u32 orig_flags, struct bool lock_direct_mutex, void *ptr) { unsigned long addr = (unsigned long) im->image; - unsigned long ip = ftrace_location(tr->ip); struct bpf_tracing_multi_data *data = ptr; if (bpf_trampoline_use_jmp(tr->flags)) addr = ftrace_jmp_set(addr); - ftrace_hash_add(data->modify, data->entry, ip, addr); + ftrace_hash_add(data->modify, data->entry, tr->ip, addr); tr->cur_image = im; return 0; }