From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=209.132.183.28; helo=mx1.redhat.com; envelope-from=lersek@redhat.com; receiver=edk2-devel@lists.01.org Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 3E8E52194D387 for ; Wed, 26 Sep 2018 02:05:21 -0700 (PDT) Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9BAC830001EF; Wed, 26 Sep 2018 09:05:20 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (ovpn-120-54.rdu2.redhat.com [10.10.120.54]) by smtp.corp.redhat.com (Postfix) with ESMTP id 42627308BDA2; Wed, 26 Sep 2018 09:05:19 +0000 (UTC) From: Laszlo Ersek To: edk2-devel-01 Cc: Michael Kinney , Ruiyu Ni , Jiewen Yao , Liming Gao References: <20180925194857.10514-1-lersek@redhat.com> Message-ID: <7935451f-6648-a383-5be2-007ab77c3a36@redhat.com> Date: Wed, 26 Sep 2018 11:05:18 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180925194857.10514-1-lersek@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.24 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Wed, 26 Sep 2018 09:05:20 +0000 (UTC) Subject: Re: [PATCH] MdePkg/BaseSynchronizationLib: fix XADD operands in GCC IA32/X64 assembly X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 26 Sep 2018 09:05:21 -0000 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Hi, On 09/25/18 21:48, Laszlo Ersek wrote: > Currently, "gcc-4.8.5-28.el7_5.1.x86_64" generates the following code for > me, from the XADD inline assembly added to "X64/GccInline.c" in commit > 17634d026f96: > >> 0000000000004383 : >> UINT32 >> EFIAPI >> InternalSyncIncrement ( >> IN volatile UINT32 *Value >> ) >> { >> 4383: 55 push %rbp >> 4384: 48 89 e5 mov %rsp,%rbp >> 4387: 48 83 ec 10 sub $0x10,%rsp >> 438b: 48 89 4d 10 mov %rcx,0x10(%rbp) >> UINT32 Result; >> >> __asm__ __volatile__ ( >> 438f: 48 8b 55 10 mov 0x10(%rbp),%rdx >> 4393: 48 8b 45 10 mov 0x10(%rbp),%rax >> 4397: b8 01 00 00 00 mov $0x1,%eax >> 439c: f0 0f c1 00 lock xadd %eax,(%rax) >> 43a0: ff c0 inc %eax >> 43a2: 89 45 fc mov %eax,-0x4(%rbp) >> : "m" (*Value) // %2 >> : "memory", >> "cc" >> ); >> >> return Result; >> 43a5: 8b 45 fc mov -0x4(%rbp),%eax >> } >> 43a8: c9 leaveq >> 43a9: c3 retq >> > > The MOV $0X1,%EAX instruction corrupts the address of Value in %RAX before > we reach the XADD instruction. In fact, it makes no sense for XADD to use > %EAX as source operand and (%RAX) as destination operand at the same time. may I get a fast review for this patch, please? The regression from commit 17634d026f96 prevents OVMF from booting. Thanks Laszlo