Re: [PATCHv5 bpf-next 01/28] ftrace: Add ftrace_hash_count function

On Sat, Apr 18, 2026 at 12:58:20AM +0000, [email protected] wrote:
> Sashiko AI review found 1 potential issue(s):
> - [Low] ftrace_hash_count() is declared under CONFIG_DYNAMIC_FTRACE but defined under CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS, leading to potential linker errors.
> --
> 
> commit 62c46ea6c0c10abc0df16b7c684809496d439e2f
> Author: Jiri Olsa <[email protected]>
> 
> ftrace: Add ftrace_hash_count function
> 
> This commit adds an external ftrace_hash_count function so the hash
> count can be obtained outside of the ftrace object.
> 
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > index 28b30c6f10314..9d9ae1bc692ae 100644
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -415,6 +415,7 @@ struct ftrace_hash *alloc_ftrace_hash(int size_bits);
> >  void free_ftrace_hash(struct ftrace_hash *hash);
> >  struct ftrace_func_entry *add_ftrace_hash_entry_direct(struct ftrace_hash *hash,
> >  						       unsigned long ip, unsigned long direct);
> > +unsigned long ftrace_hash_count(struct ftrace_hash *hash);
> >  
> >  /* The hash used to know what functions callbacks trace */
> >  struct ftrace_ops_hash {
> 
> [ ... ]
> 
> > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > index b2611de3f5943..57ab01fd00bda 100644
> > --- a/kernel/trace/ftrace.c
> > +++ b/kernel/trace/ftrace.c
> > @@ -6288,11 +6288,16 @@ int modify_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
> >  }
> >  EXPORT_SYMBOL_GPL(modify_ftrace_direct);
> >  
> > -static unsigned long hash_count(struct ftrace_hash *hash)
> > +static inline unsigned long hash_count(struct ftrace_hash *hash)
> >  {
> >  	return hash ? hash->count : 0;
> >  }
> >  
> > +unsigned long ftrace_hash_count(struct ftrace_hash *hash)
> > +{
> > +	return hash_count(hash);
> > +}
> > +
> 
> If a kernel is configured with CONFIG_DYNAMIC_FTRACE=y but 
> CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS=n, will this result in a linker error?
> 
> The declaration in include/linux/ftrace.h is located under 
> CONFIG_DYNAMIC_FTRACE, but this definition in kernel/trace/ftrace.c is placed 
> inside a CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS block.
> 
> Code built-in to the kernel (like BPF or tracing extensions) that attempts 
> to use this new API could compile successfully but fail to link on 
> architectures that do not support direct ftrace calls.

right, will check the compilation for such config

jirka