On Sun, 13 Apr 2025 09:44:44 +0800
Menglong Dong <menglong8.dong@xxxxxxxxx> wrote:
> The maximum of the ftrace hash bits is made fls(32) in
> register_ftrace_direct(), which seems illogical. So, we fix it by making
> the max hash bits FTRACE_HASH_MAX_BITS instead.
>
Loogs good to me.
Acked-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Thanks!
> Fixes: d05cb470663a ("ftrace: Fix modification of direct_function hash while in use")
> Signed-off-by: Menglong Dong <dongml2@xxxxxxxxxxxxxxx>
> ---
> v2:
> - thanks for Steven's advice, we fix the problem by making the max hash
> bits FTRACE_HASH_MAX_BITS instead.
> ---
> kernel/trace/ftrace.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 1a48aedb5255..d153ad13e0e0 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -5914,9 +5914,10 @@ int register_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
>
> /* Make a copy hash to place the new and the old entries in */
> size = hash->count + direct_functions->count;
> - if (size > 32)
> - size = 32;
> - new_hash = alloc_ftrace_hash(fls(size));
> + size = fls(size);
> + if (size > FTRACE_HASH_MAX_BITS)
> + size = FTRACE_HASH_MAX_BITS;
> + new_hash = alloc_ftrace_hash(size);
> if (!new_hash)
> goto out_unlock;
>
> --
> 2.39.5
>
>
--
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
