Re: [PATCH] ftrace: properly merge notrace hash

[Steven Rostedt]

On Tue,  8 Apr 2025 02:07:44 +0800
Andy Chiu <andyb...@gmail.com> wrote:

> The global notrace hash should be jointly decided by the intersection of
> each subops's notrace hash, but not the filter hash.
> 
> Fixes: 5fccc7552ccb ("ftrace: Add subops logic to allow one ops to manage 
> many")
> Signed-off-by: Andy Chiu <andyb...@gmail.com>
> ---
>  kernel/trace/ftrace.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 1a48aedb5255..ee662f380b61 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -3526,18 +3526,17 @@ int ftrace_startup_subops(struct ftrace_ops *ops, 
> struct ftrace_ops *subops, int
>           ftrace_hash_empty(subops->func_hash->notrace_hash)) {
>               notrace_hash = EMPTY_HASH;
>       } else {
> -             size_bits = max(ops->func_hash->filter_hash->size_bits,
> -                             subops->func_hash->filter_hash->size_bits);
> +             size_bits = max(ops->func_hash->notrace_hash->size_bits,
> +                             subops->func_hash->notrace_hash->size_bits);
>               notrace_hash = alloc_ftrace_hash(size_bits);
>               if (!notrace_hash) {
> -                     free_ftrace_hash(filter_hash);
> +                     free_ftrace_hash(notrace_hash);
>                       return -ENOMEM;
>               }
>  
> -             ret = intersect_hash(&notrace_hash, ops->func_hash->filter_hash,
> -                                  subops->func_hash->filter_hash);
> +             ret = intersect_hash(&notrace_hash, 
> ops->func_hash->notrace_hash,
> +                                  subops->func_hash->notrace_hash);

Thanks for catching this.


>               if (ret < 0) {
> -                     free_ftrace_hash(filter_hash);

The filter_hash still needs to be freed, as it could have been allocated in
the previous if statement and never used (both the filter_hash and
notrace_hash get used at the end of the function via ftrace_update_ops().

Care to send a v2?

-- Steve


>                       free_ftrace_hash(notrace_hash);
>                       return ret;
>               }