From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53703) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fiwSI-00072A-Js for qemu-devel@nongnu.org; Fri, 27 Jul 2018 02:42:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fiwSF-0008PZ-H5 for qemu-devel@nongnu.org; Fri, 27 Jul 2018 02:42:26 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:36224 helo=mx0a-001b2d01.pphosted.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fiwSF-0008PI-A1 for qemu-devel@nongnu.org; Fri, 27 Jul 2018 02:42:23 -0400 Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w6R6dg3u126176 for ; Fri, 27 Jul 2018 02:42:22 -0400 Received: from e06smtp04.uk.ibm.com (e06smtp04.uk.ibm.com [195.75.94.100]) by mx0b-001b2d01.pphosted.com with ESMTP id 2kfsqn9e29-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 27 Jul 2018 02:42:21 -0400 Received: from localhost by e06smtp04.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 27 Jul 2018 07:42:19 +0100 References: <153258768962.6738.11319866502689416568.stgit@dhcp-9-109-246-16> From: Shivaprasad G Bhat Date: Fri, 27 Jul 2018 12:12:14 +0530 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Message-Id: Subject: Re: [Qemu-devel] [PATCH] linux-user: ppc64: don't use volatile register during safe_syscall List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Richard Henderson , dgibson@redhat.com, riku.voipio@iki.fi, laurent@vivier.eu Cc: qemu-devel@nongnu.org On 07/26/2018 10:56 PM, Richard Henderson wrote: > On 07/25/2018 11:48 PM, Shivaprasad G Bhat wrote: >> Reference: >> https://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi-1.9.html#REG > This document is for _CALL_ELF < 2. For ppc64le, the document is at > > https://openpowerfoundation.org/wp-content/uploads/2016/03/ABI64BitOpenPOWERv1.1_16July2015_pub4.pdf > > In both cases, it appears that we can (ab)use SP+16 to save > the value of r14 across the syscall. This slot would normally > be used for saving our own return address (LR), but we have no > need to save that value because it *is* preserved across the syscall. I will send updated patch as suggested. Thanks, Shivaprasad > > > r~ >