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 3BE8221157FD6 for ; Wed, 26 Sep 2018 05:04:39 -0700 (PDT) Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id CCCBF308A95D; Wed, 26 Sep 2018 12:04:38 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (ovpn-122-6.rdu2.redhat.com [10.10.122.6]) by smtp.corp.redhat.com (Postfix) with ESMTP id 73E2860C17; Wed, 26 Sep 2018 12:04:37 +0000 (UTC) To: "Ni, Ruiyu" , edk2-devel-01 Cc: Michael Kinney , Jiewen Yao , Liming Gao References: <20180925194857.10514-1-lersek@redhat.com> <7935451f-6648-a383-5be2-007ab77c3a36@redhat.com> From: Laszlo Ersek Message-ID: <9175ba14-99aa-6ed2-24ca-26af69dd5bf5@redhat.com> Date: Wed, 26 Sep 2018 14:04:36 +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: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Wed, 26 Sep 2018 12:04:38 +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 12:04:40 -0000 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit On 09/26/18 11:34, Ni, Ruiyu wrote: > On 9/26/2018 5:05 PM, Laszlo Ersek wrote: >> 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. > > Sure. Reviewed-by: Ruiyu Ni Thanks, Ray! Commit 8a94eb9283fa. Laszlo