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=-0.8 required=5.0 tests=ALL_TRUSTED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NO_DNS_FOR_FROM,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.6 Received: from integral2.. (unknown [182.2.70.161]) by gnuweeb.org (Postfix) with ESMTPSA id 632E27E72A; Tue, 29 Mar 2022 10:17:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gnuweeb.org; s=default; t=1648549081; bh=sOa5bTrQEKERvFJedlayh1Unbt9LOKPwsCzeI50Bj1k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lx/7IuFTk6fAH3rYLwr/TJtsTaUHd3qTJqK3lcjI/hhU25WOBbGYuKY+Mj8ceN5r9 rokZey+MbRFLdlrhTRRWlmeJS4uX3W41mpW/z5cNbO74neTuvt2hHNNEqWCcuw56nS AdbA0hKG4w7mjEtBtJloml4CGj8b9N6IdAvEIMz+7/m2h7tbq+d1kSMmUfHo9fBJo0 BTd0yG2LtbHaaNTVdBo2IcvtDE8cRCH1Kg2CIuIQ+a0COLQOrxORp/xmVZqTQ5TgsN xTEBIWaqDWvCTOV2N+UyIQ9IDxTUUsIJ+pRkhnKO2lY6sr4/NGjUq7iypI17bKvJWJ N3kZ5duH8YYuA== From: Ammar Faizi To: Willy Tarreau Cc: Ammar Faizi , Alviro Iskandar Setiawan , Nugraha , "Paul E. McKenney" , Linux Kernel Mailing List , GNU/Weeb Mailing List , x86@kernel.org, llvm@lists.linux.dev, David Laight Subject: [PATCH v2 4/9] tools/nolibc: i386: Implement syscall with 6 arguments Date: Tue, 29 Mar 2022 17:17:32 +0700 Message-Id: <20220329101737.58985-5-ammarfaizi2@gnuweeb.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20220329101737.58985-1-ammarfaizi2@gnuweeb.org> References: <20220329101737.58985-1-ammarfaizi2@gnuweeb.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit List-Id: On i386, the 6th argument of syscall goes in %ebp. However, both Clang and GCC cannot use %ebp in the clobber list and in the "r" constraint without using -fomit-frame-pointer. To make it always available for any kind of compilation, the below workaround is implemented. 1) Push the 6-th argument. 2) Push %ebp. 3) Load the 6-th argument from 4(%esp) to %ebp. 4) Do the syscall (int $0x80). 5) Pop %ebp (restore the old value of %ebp). 6) Add %esp by 4 (undo the stack pointer). Cc: x86@kernel.org Cc: llvm@lists.linux.dev Link: https://lore.kernel.org/lkml/2e335ac54db44f1d8496583d97f9dab0@AcuMS.aculab.com Suggested-by: David Laight Signed-off-by: Ammar Faizi === @@ Changelog: Link v1: https://lore.gnuweeb.org/gwml/20220324073039.140946-7-ammarfaizi2@gnuweeb.org v1 -> v2: * No changes * Link RFC v2: https://lore.kernel.org/lkml/20220322102115.186179-4-ammarfaizi2@gnuweeb.org RFC v2 -> v1: - Use the same pattern for syscall6, regardless using GCC or Clang (comment from David). - Use appropriate constraints for syscall6 instead of always using register variables (comment from David). Link RFC v1: https://lore.kernel.org/llvm/20220320093750.159991-4-ammarfaizi2@gnuweeb.org RFC v1 -> RFC v2: - Fix %ebp saving method. Don't use redzone, i386 doesn't have a redzone (comment from David and Alviro). --- tools/include/nolibc/arch-i386.h | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/tools/include/nolibc/arch-i386.h b/tools/include/nolibc/arch-i386.h index 10aada40680d..d7e7212346e2 100644 --- a/tools/include/nolibc/arch-i386.h +++ b/tools/include/nolibc/arch-i386.h @@ -167,6 +167,29 @@ struct sys_stat_struct { _ret; \ }) +#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \ +({ \ + long _eax = (long)(num); \ + long _arg6 = (long)(arg6); /* Always 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"(_eax) /* %eax */ \ + : "b"(arg1), /* %ebx */ \ + "c"(arg2), /* %ecx */ \ + "d"(arg3), /* %edx */ \ + "S"(arg4), /* %esi */ \ + "D"(arg5), /* %edi */ \ + [_arg6]"m"(_arg6) /* memory */ \ + : "memory", "cc" \ + ); \ + _eax; \ +}) + /* startup code */ /* * i386 System V ABI mandates: -- Ammar Faizi