netdev - Re: [PATCH 1/2] tools, bpf_asm: Hard error on out of range jumps.

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Date:   Wed, 24 Feb 2021 10:30:55 +0100
From:   Ilya Leoshkevich <iii@...ux.ibm.com>
To:     Ian Denhardt <ian@...hack.net>, ast@...nel.org,
        daniel@...earbox.net, bpf@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 1/2] tools, bpf_asm: Hard error on out of range jumps.

On Tue, 2021-02-23 at 21:15 -0500, Ian Denhardt wrote:
> Per discussion at:
> 
> https://lore.kernel.org/bpf/c964892195a6b91d20a67691448567ef528ffa6d.camel@linux.ibm.com/T/#t
> 
> ...this was originally introduced as a warning due to concerns about
> breaking existing code, but a hard error probably makes more sense,
> especially given that concerns about breakage were only speculation.
> ---
>  tools/bpf/bpf_exp.y | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/bpf/bpf_exp.y b/tools/bpf/bpf_exp.y
> index 8d48e896be50..8d03e5245da5 100644
> --- a/tools/bpf/bpf_exp.y
> +++ b/tools/bpf/bpf_exp.y
> @@ -549,9 +549,11 @@ static uint8_t bpf_encode_jt_jf_offset(int off,
> int i)
>  {
>         int delta = off - i - 1;
>  
> -       if (delta < 0 || delta > 255)
> -               fprintf(stderr, "warning: insn #%d jumps to insn #%d, "
> +       if (delta < 0 || delta > 255) {
> +               fprintf(stderr, "error: insn #%d jumps to insn #%d, "
>                                 "which is out of range\n", i, off);
> +               exit(1);
> +       }
>         return (uint8_t) delta;
>  }
>  

Acked-by: Ilya Leoshkevich <iii@...ux.ibm.com>