From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752413AbcEQSDu (ORCPT ); Tue, 17 May 2016 14:03:50 -0400 Received: from shards.monkeyblade.net ([149.20.54.216]:49125 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751835AbcEQSDt (ORCPT ); Tue, 17 May 2016 14:03:49 -0400 Date: Tue, 17 May 2016 14:03:46 -0400 (EDT) Message-Id: <20160517.140346.1420108193136786648.davem@davemloft.net> To: yang.shi@linaro.org Cc: ast@kernel.org, will.deacon@arm.com, catalin.marinas@arm.com, daniel@iogearbox.net, zlim.lnx@gmail.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linaro-kernel@lists.linaro.org Subject: Re: [PATCH v2 net-next] bpf: arm64: remove callee-save registers use for tmp registers From: David Miller In-Reply-To: <1463441786-32224-1-git-send-email-yang.shi@linaro.org> References: <1463441786-32224-1-git-send-email-yang.shi@linaro.org> X-Mailer: Mew version 6.6 on Emacs 24.5 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Tue, 17 May 2016 11:03:48 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yang Shi 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 > Acked-by: Zi Shen Lim > Signed-off-by: Yang Shi Applied.