From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on gnuweeb.org X-Spam-Level: X-Spam-Status: No, score=-1.8 required=5.0 tests=ALL_TRUSTED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,NO_DNS_FOR_FROM, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 Received: from [192.168.12.80] (unknown [182.2.69.158]) by gnuweeb.org (Postfix) with ESMTPSA id 27DA87E2DF; Tue, 22 Mar 2022 13:26:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gnuweeb.org; s=default; t=1647955607; bh=SKM43D9jDBq+PWDOPBX3QtOzn+TW4kuM/fe+xnCwC/k=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=PbUywEleF/ZAh7d/Q0QM2FLLqGcJDHh3Bnp1FuuSZVHvDKGlnXorXzwiTk+H7QyFs 5kXTKXnyoR7y00+wug7GGo/IiyaYuugAx4JpRBOsRp0pTyhMGjuMxxpcYMk3Lfeqqx 0UZyJgqhH1yvH7EWrJDwLJ4V3+YiNVzXqYjermxXLrouTvY4OlwTBzOMApswMng4vh X4PC6leIptY6ORiiC3hpk1qICmTlOD+UkiyMFg0karoCZfuuxWlZe+alAYCL0xmsAX NRnP0WSKSLggQlIhUAZbE/i5GdP/a2KvfAFH6CtkMWUyx7thFLHnUj/RzwK0OmOJus 5iwSpioO3BNYw== Message-ID: <81569a1c-a6d3-ceb2-a1f1-f229a024d684@gnuweeb.org> Date: Tue, 22 Mar 2022 20:26:37 +0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [RFC PATCH v2 3/8] tools/nolibc: i386: Implement syscall with 6 arguments Content-Language: en-US To: Willy Tarreau Cc: David Laight , "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> <20220322121338.GD10306@1wt.eu> From: Ammar Faizi In-Reply-To: <20220322121338.GD10306@1wt.eu> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit List-Id: On 3/22/22 7:13 PM, Willy Tarreau wrote: > On Tue, Mar 22, 2022 at 07:02:53PM +0700, Ammar Faizi wrote: >> 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? > > Hmmm indeed that comes back to the existing constructs and is certainly > more in line with the rest of the code (plus it will not be affected by > -O0). > > I seem to remember a register allocation issue which kept me away from > implementing it this way on i386 back then, but given that my focus was > not as much on i386 as it was on other platforms, it's likely that I have > not insisted too much and not tried this one which looks like the way to > go to me. I turned out GCC refuses to use "rm" if we compile without -fomit-frame-pointer (e.g. without optimization / -O0). So I will still use "m" here. -- Ammar Faizi