netdev - Re: [PATCH net-next 01/13] ARM: net: bpf: enumerate the JIT scratch stack layout

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Message-ID: <41b5fc68-e15f-56f9-c55b-4f6deb61c54c@iogearbox.net>
Date:   Tue, 10 Jul 2018 20:30:04 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Russell King <rmk+kernel@...linux.org.uk>
Cc:     netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH net-next 01/13] ARM: net: bpf: enumerate the JIT scratch
 stack layout

Hi Russell,

thanks a lot for your work on the arm32 JIT!

On 07/10/2018 02:36 PM, Russell King wrote:
> Enumerate the contents of the JIT scratch stack layout used for storing
> some of the JITs 64-bit registers, tail call counter and AX register.
> 
> XXX: what about the skb_copy_bits buffer - this appears to overlap with
> the first word of the JITs accessible stack.

Could you elaborate on that case? Unless I'm missing something there should
be no use of the skb_copy_bits buffer anymore (aka former SKB_BUFFER at
STACK_VAR(SCRATCH_SIZE) offset), but aside from that it's not supposed to
overlap either.

Thanks,
Daniel