From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 53BC6C433EF for ; Tue, 22 Mar 2022 12:03:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234518AbiCVMEb (ORCPT ); Tue, 22 Mar 2022 08:04:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45020 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231799AbiCVME3 (ORCPT ); Tue, 22 Mar 2022 08:04:29 -0400 Received: from gnuweeb.org (gnuweeb.org [51.81.211.47]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6AC3923E for ; Tue, 22 Mar 2022 05:03:02 -0700 (PDT) Received: from [192.168.12.80] (unknown [182.2.69.158]) by gnuweeb.org (Postfix) with ESMTPSA id 6DA6E7E308; Tue, 22 Mar 2022 12:02:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gnuweeb.org; s=default; t=1647950581; bh=ZQJLnPz+HIze1L/LflEJoR20vMyXMwvNahO4vlcWCnQ=; h=Date:To:Cc:References:From:Subject:In-Reply-To:From; b=dLsuuOGV+8ZBwuvsEC2HBuXMQE+Xn8Lg4T02mmYnNCpHVATJa7Ma8TOsD5GmYwWNt 43UxIyR8OErh32Ao8p7G97hP3/urxGAMwybm/Ob7lrDzc5ME8Smv1/ZJxiOJSUyiun jxA3glPl86F+W2iTX0Cohd2YyZ/sNYWwQp1od2rfG6fo8bO8G2pjgcIrAEq6D38v3K 5nVp6YnAcd7+9wigAhz/qymTN39BN3eqPUYil/TLa29AmfUR9ZpFxoqrSdSQ01iJts 01j0X4QzyWbUoYM2jjySnfKLibjJgOUQW/Qsz1c6Ru0Zs3JEEn3E31BPoUDJdYjCeH mFRrBry7B57mA== Message-ID: Date: Tue, 22 Mar 2022 19:02:53 +0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Content-Language: en-US To: David Laight , Willy Tarreau Cc: "Paul E. McKenney" , Alviro Iskandar Setiawan , Nugraha , Linux Kernel Mailing List , GNU/Weeb Mailing List , "x86@kernel.org" , "llvm@lists.linux.dev" References: <20220322102115.186179-1-ammarfaizi2@gnuweeb.org> <20220322102115.186179-4-ammarfaizi2@gnuweeb.org> <8653f6784a9b4272a59a75a530663567@AcuMS.aculab.com> From: Ammar Faizi Subject: Re: [RFC PATCH v2 3/8] tools/nolibc: i386: Implement syscall with 6 arguments In-Reply-To: <8653f6784a9b4272a59a75a530663567@AcuMS.aculab.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/22/22 6:39 PM, David Laight wrote: >> + __asm__ volatile ( >> + "pushl %[arg6]\n\t" >> + "pushl %%ebp\n\t" >> + "movl 4(%%esp), %%ebp\n\t" >> + "int $0x80\n\t" >> + "popl %%ebp\n\t" >> + "addl $4,%%esp\n\t" >> + : "=a"(eax) >> + : "a"(eax), "b"(ebx), "c"(ecx), "d"(edx), "S"(esi), "D"(edi), > > Does having "=a" for an output constraint and "a" for an input > constraint actually DTRT? > There is a special syntax for tying input and output to > the same register. > Or you could use "+a"(nr_rval) and 'return nr_rval'. Well, I agree with your previous email. Now since we no longer use a #pragma optimize with -fomit-frame-pointer, the function is not needed. I propose the following macro (this is not so much different with other my_syscall macro), expect the 6th argument can be in reg or mem. The "rm" constraint here gives the opportunity for the compiler to use %ebp instead of memory if -fomit-frame-pointer is turned on. #define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \ ({ \ long _ret; \ register long _num asm("eax") = (num); \ register long _arg1 asm("ebx") = (long)(arg1); \ register long _arg2 asm("ecx") = (long)(arg2); \ register long _arg3 asm("edx") = (long)(arg3); \ register long _arg4 asm("esi") = (long)(arg4); \ register long _arg5 asm("edi") = (long)(arg5); \ long _arg6 = (long)(arg6); /* Might be in memory */ \ \ asm volatile ( \ "pushl %[_arg6]\n\t" \ "pushl %%ebp\n\t" \ "movl 4(%%esp), %%ebp\n\t" \ "int $0x80\n\t" \ "popl %%ebp\n\t" \ "addl $4,%%esp\n\t" \ : "=a"(_ret) \ : "r"(_num), "r"(_arg1), "r"(_arg2), "r"(_arg3), \ "r"(_arg4),"r"(_arg5), [_arg6]"rm"(_arg6) \ : "memory", "cc" \ ); \ _ret; \ }) What do you think? -- Ammar Faizi