netdev - Re: [PATCHv3 bpf-next 01/12] bpf: Add iterator for spilled registers

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Date:   Fri, 28 Sep 2018 15:41:56 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Joe Stringer <joe@...d.net.nz>
Cc:     netdev@...r.kernel.org, ast@...nel.org, john.fastabend@...il.com,
        tgraf@...g.ch, kafai@...com, nitin.hande@...il.com,
        mauricio.vasquez@...ito.it
Subject: Re: [PATCHv3 bpf-next 01/12] bpf: Add iterator for spilled registers

On 09/28/2018 01:26 AM, Joe Stringer wrote:
> Add this iterator for spilled registers, it concentrates the details of
> how to get the current frame's spilled registers into a single macro
> while clarifying the intention of the code which is calling the macro.
> 
> Signed-off-by: Joe Stringer <joe@...d.net.nz>
> Acked-by: Alexei Starovoitov <ast@...nel.org>
> ---
>  include/linux/bpf_verifier.h | 11 +++++++++++
>  kernel/bpf/verifier.c        | 16 +++++++---------
>  2 files changed, 18 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> index b42b60a83e19..af262b97f586 100644
> --- a/include/linux/bpf_verifier.h
> +++ b/include/linux/bpf_verifier.h
> @@ -131,6 +131,17 @@ struct bpf_verifier_state {
>  	u32 curframe;
>  };
>  
> +#define __get_spilled_reg(slot, frame)					\
> +	(((slot < frame->allocated_stack / BPF_REG_SIZE) &&		\
> +	  (frame->stack[slot].slot_type[0] == STACK_SPILL))		\
> +	 ? &frame->stack[slot].spilled_ptr : NULL)
> +
> +/* Iterate over 'frame', setting 'reg' to either NULL or a spilled register. */
> +#define for_each_spilled_reg(iter, frame, reg)				\
> +	for (iter = 0, reg = __get_spilled_reg(iter, frame);		\
> +	     iter < frame->allocated_stack / BPF_REG_SIZE;		\
> +	     iter++, reg = __get_spilled_reg(iter, frame))
> +

(Just a very small nit: please make sure this has a bpf_ prefix given this
is a global kernel header.)