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

[Steven Rostedt]

On Sun, 26 Oct 2025 13:54:43 -0700
Song Liu <s...@kernel.org> wrote:

> --- 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;
> +             remove_direct_functions_hash(hash, addr);
> +     }
>  

As you AI bot noticed that it was missing what unregister_ftrace_direct()
does, instead, can we make a helper function that both use? This way it
will not get out of sync again.

static void reset_direct(struct ftrace_ops *ops, unsigned long addr)
{
        struct ftrace_hash *hash = ops->func_hash->filter_hash;

        ops->func = NULL;
        ops->trampoline = 0;
        remove_direct_functions_hash(hash, addr);
}

Then we could have:

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 0c91247a95ab..51c3f5d46fde 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6062,7 +6062,7 @@ int register_ftrace_direct(struct ftrace_ops *ops, 
unsigned long addr)
 
        err = register_ftrace_function_nolock(ops);
        if (err)
-               remove_direct_functions_hash(hash, addr);
+               reset_direct(ops, addr);
 
  out_unlock:
        mutex_unlock(&direct_mutex);
@@ -6095,7 +6095,6 @@ EXPORT_SYMBOL_GPL(register_ftrace_direct);
 int unregister_ftrace_direct(struct ftrace_ops *ops, unsigned long addr,
                             bool free_filters)
 {
-       struct ftrace_hash *hash = ops->func_hash->filter_hash;
        int err;
 
        if (check_direct_multi(ops))
@@ -6105,13 +6104,9 @@ int unregister_ftrace_direct(struct ftrace_ops *ops, 
unsigned long addr,
 
        mutex_lock(&direct_mutex);
        err = unregister_ftrace_function(ops);
-       remove_direct_functions_hash(hash, addr);
+       reset_direct(ops, addr);
        mutex_unlock(&direct_mutex);
 
-       /* cleanup for possible another register call */
-       ops->func = NULL;
-       ops->trampoline = 0;
-
        if (free_filters)
                ftrace_free_filter(ops);
        return err;

-- Steve