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 F29957E308; Tue, 22 Mar 2022 12:07:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gnuweeb.org; s=default; t=1647950861; bh=6+Vksk11nsg1faQTkiQCnBBB8df1qVnWOn2yS0BMZik=; h=Date:Subject:From:To:Cc:References:In-Reply-To:From; b=BbQy2doFPp/k3wyxs9aSPO2wEus9iNM6OnCQFsA4LaUig2IIEBWtt+C+utsdua2xM qBwTkUddH5lM0BfZKhkHmUBMpIVSDsPtqLcFrEcig9XhJnv0FAZdQX5h92O58k/Ub8 alHRhOoC50U4OKWB3HUCxpPC/DKZQqkzn3NCqQf9rMVjqRitUC0EV3QIZ9GNCwHVUZ NquJroGm9W/ksrRSVwC6aqRHz7UHuvZfosXT4JaHw407aEPLc2/xDGnOx6QJKWS41i HM5o3T1wUWgV+5+/vs91oTXoyME7gmhWm9wvpprbt/VBfYU+0Y+3LbzlqS+o2kLSb1 d+HJSWh+hsZGg== Message-ID: Date: Tue, 22 Mar 2022 19:07:34 +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 From: Ammar Faizi 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> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit List-Id: On 3/22/22 7:02 PM, Ammar Faizi wrote: > 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? > For the following code: int main() { mmap(NULL, 0x1000, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0); return 0; } GCC generates this: 00001000
: 1000: push %ebp 1001: mov $0xc0,%eax 1006: mov $0x1000,%ecx 100b: mov $0x3,%edx 1010: push %edi 1011: xor %ebp,%ebp 1013: mov $0xffffffff,%edi 1018: push %esi 1019: mov $0x22,%esi 101e: push %ebx 101f: xor %ebx,%ebx 1021: push %ebp <--- arg6 here 1022: push %ebp 1023: mov 0x4(%esp),%ebp 1027: int $0x80 1029: pop %ebp 102a: add $0x4,%esp 102d: xor %eax,%eax 102f: pop %ebx 1030: pop %esi 1031: pop %edi 1032: pop %ebp 1033: ret -- Ammar Faizi