kernel-hardening - Re: arch: arm: bpf: Converting cBPF to eBPF for arm 32 bit

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Message-ID: <CAHgaXd+4QkFxnt-_iCqH8AyCN_Y8gXwr+y=iugz38NKSWspsbA@mail.gmail.com>
Date: Wed, 29 Mar 2017 02:19:54 +0530
From: Shubham Bansal <illusionist.neo@...il.com>
To: David Miller <davem@...emloft.net>
Cc: Kees Cook <keescook@...omium.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Mircea Gherzan <mgherzan@...il.com>, Network Development <netdev@...r.kernel.org>, 
	kernel-hardening@...ts.openwall.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: arch: arm: bpf: Converting cBPF to eBPF for arm 32 bit

Thanks David. It helped a lot.

Hi Daniel,

Do you have any document to understand the working of tail calls? I
looked at your presentations but it seemed confusing to me. Anything
simple would be great, just about the tail calls. I don't think I need
examples, I can get them from your presentations. I just need a very
general idea. May be you know the code in kernel where it is
implemented.
Thanks for the help Daniel.

Best,
Shubham Bansal

On Thu, Mar 16, 2017 at 3:25 AM, David Miller <davem@...emloft.net> wrote:
> From: Shubham Bansal <illusionist.neo@...il.com>
> Date: Wed, 15 Mar 2017 17:43:44 +0530
>
>>> You can't truncate, but you'll have to build 64-bit ops using 32-bit registers.
>>
>> A small example would help a lot.
>
> You can simply perform 64-bit operations in C code and see what gcc
> outputs for that code on this 32-bit target.

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