Re: [PATCH v3 bpf 1/3] ftrace: Fix BPF fexit with livepatch

[Song Liu]

> On Oct 27, 2025, at 1:48 AM, Jiri Olsa <olsaj...@gmail.com> wrote:

[…]
> 
>> 
>> 
>> diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
>> index 5949095e51c3..f2cb0b097093 100644
>> --- a/kernel/bpf/trampoline.c
>> +++ b/kernel/bpf/trampoline.c
>> @@ -479,11 +479,6 @@ static int bpf_trampoline_update(struct bpf_trampoline 
>> *tr, bool lock_direct_mut
>> * BPF_TRAMP_F_SHARE_IPMODIFY is set, we can generate the
>> * trampoline again, and retry register.
>> */
>> - /* reset fops->func and fops->trampoline for re-register */
>> - tr->fops->func = NULL;
>> - tr->fops->trampoline = 0;
>> -
>> - /* free im memory and reallocate later */
>> bpf_tramp_image_free(im);
>> goto again;
>> }
>> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
>> index 42bd2ba68a82..725c224fb4e6 100644
>> --- a/kernel/trace/ftrace.c
>> +++ b/kernel/trace/ftrace.c
>> @@ -6048,6 +6048,12 @@ int register_ftrace_direct(struct ftrace_ops *ops, 
>> unsigned long addr)
>> ops->direct_call = addr;
>> 
>> err = register_ftrace_function_nolock(ops);
>> + if (err) {
>> + /* cleanup for possible another register call */
>> + ops->func = NULL;
>> + ops->trampoline = 0;
> 
> nit, we could cleanup also flags and direct_call just to be complete,
> but at the same time it does not seem to affect anything

I actually thought about this and decided to use the same 
logic as unregister_ftrace_direct(). 

Thanks,
Song