netdev - Re: [PATCH v2 net-next] bpf: arm64: remove callee-save registers use for tmp registers

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Date:	Tue, 17 May 2016 14:03:46 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	yang.shi@...aro.org
Cc:	ast@...nel.org, will.deacon@....com, catalin.marinas@....com,
	daniel@...earbox.net, zlim.lnx@...il.com,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH v2 net-next] bpf: arm64: remove callee-save registers
 use for tmp registers

From: Yang Shi <yang.shi@...aro.org>
Date: Mon, 16 May 2016 16:36:26 -0700

> In the current implementation of ARM64 eBPF JIT, R23 and R24 are used for
> tmp registers, which are callee-saved registers. This leads to variable size
> of JIT prologue and epilogue. The latest blinding constant change prefers to
> constant size of prologue and epilogue. AAPCS reserves R9 ~ R15 for temp
> registers which not need to be saved/restored during function call. So, replace
> R23 and R24 to R10 and R11, and remove tmp_used flag to save 2 instructions for
> some jited BPF program.
> 
> CC: Daniel Borkmann <daniel@...earbox.net>
> Acked-by: Zi Shen Lim <zlim.lnx@...il.com>
> Signed-off-by: Yang Shi <yang.shi@...aro.org>

Applied.