Re: [PATCH V4 1/3] kallsyms: Simplify update_iter_mod()

[Peter Zijlstra]

On Wed, Jun 06, 2018 at 03:54:09PM +0300, Adrian Hunter wrote:
> The logic in update_iter_mod() is overcomplicated and gets worse every time
> another get_ksymbol_* function is added.
> 
> In preparation for adding another get_ksymbol_* function, simplify logic in
> update_iter_mod().
> 
> Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> Acked-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>

Both Daniel and Steven touched this function last year, let's also Cc
them.

Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>

> ---
>  kernel/kallsyms.c | 25 +++++++++++--------------
>  1 file changed, 11 insertions(+), 14 deletions(-)
> 
> diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> index a23e21ada81b..aa31aa07f2ef 100644
> --- a/kernel/kallsyms.c
> +++ b/kernel/kallsyms.c
> @@ -506,27 +506,24 @@ static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
>  	}
>  }
>  
> +/*
> + * The end position (last + 1) of each additional kallsyms section is recorded
> + * in iter->pos_..._end as each section is added, and so can be used to
> + * determine which get_ksymbol_...() function to call next.
> + */
>  static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
>  {
>  	iter->pos = pos;
>  
> -	if (iter->pos_ftrace_mod_end > 0 &&
> -	    iter->pos_ftrace_mod_end < iter->pos)
> -		return get_ksymbol_bpf(iter);
> -
> -	if (iter->pos_mod_end > 0 &&
> -	    iter->pos_mod_end < iter->pos) {
> -		if (!get_ksymbol_ftrace_mod(iter))
> -			return get_ksymbol_bpf(iter);
> +	if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
> +	    get_ksymbol_mod(iter))
>  		return 1;
> -	}
>  
> -	if (!get_ksymbol_mod(iter)) {
> -		if (!get_ksymbol_ftrace_mod(iter))
> -			return get_ksymbol_bpf(iter);
> -	}
> +	if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > pos) &&
> +	    get_ksymbol_ftrace_mod(iter))
> +		return 1;
>  
> -	return 1;
> +	return get_ksymbol_bpf(iter);
>  }
>  
>  /* Returns false if pos at or past end of file. */
> -- 
> 1.9.1
>