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From: Daniel Borkmann <daniel@iogearbox.net>
To: Will Deacon <will.deacon@arm.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com,
	ast@fb.com
Subject: Re: [PATCH] arm64/bpf: use movn/movk/movk sequence to generate kernel addresses
Date: Tue, 27 Nov 2018 19:24:40 +0100	[thread overview]
Message-ID: <c8f11ce3-1ab4-5e54-85f6-2431c7eb8a7a@iogearbox.net> (raw)
In-Reply-To: <20181127182203.GA19721@arm.com>

On 11/27/2018 07:22 PM, Will Deacon wrote:
> Hi Ard,
> 
> On Fri, Nov 23, 2018 at 06:29:02PM +0100, Ard Biesheuvel wrote:
>> On arm64, all executable code is guaranteed to reside in the vmalloc
>> space (or the module space), and so jump targets will only use 48
>> bits at most, and the remaining bits are guaranteed to be 0x1.
>>
>> This means we can generate an immediate jump address using a sequence
>> of one MOVN (move wide negated) and two MOVK instructions, where the
>> first one sets the lower 16 bits but also sets all top bits to 0x1.
>>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> ---
> 
> Acked-by: Will Deacon <will.deacon@arm.com>
> 
> Denial, Alexei, shall I take this via arm64, or would you rather take
> it via davem?

Yeah we can take it via bpf trees, thanks.

Cheers,
Daniel

  reply	other threads:[~2018-11-27 18:24 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-23 17:29 Ard Biesheuvel
2018-11-27 18:22 ` Will Deacon
2018-11-27 18:24   ` Daniel Borkmann [this message]
2018-11-30 10:07     ` Daniel Borkmann

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