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 356DD20349DA0 for ; Mon, 13 Nov 2017 10:32:41 -0800 (PST) Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6521E356D5; Mon, 13 Nov 2017 18:36:47 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (ovpn-120-226.rdu2.redhat.com [10.10.120.226]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1EC8186E0A; Mon, 13 Nov 2017 18:36:45 +0000 (UTC) To: Jordan Justen , edk2-devel-01 Cc: Ard Biesheuvel , Ruiyu Ni References: <20171110154908.306-1-lersek@redhat.com> <20171110154908.306-3-lersek@redhat.com> <151059752091.21010.2353399254871736446@jljusten-skl> From: Laszlo Ersek Message-ID: <13cae797-05c1-7ea0-0763-707cc1985320@redhat.com> Date: Mon, 13 Nov 2017 19:36:45 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <151059752091.21010.2353399254871736446@jljusten-skl> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Mon, 13 Nov 2017 18:36:47 +0000 (UTC) Subject: Re: [PATCH 2/4] OvmfPkg/Sec/Ia32: seed the temporary RAM with PcdInitValueInTempStack X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Nov 2017 18:32:41 -0000 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 11/13/17 19:25, Jordan Justen wrote: > On 2017-11-10 07:49:06, Laszlo Ersek wrote: >> diff --git a/OvmfPkg/Sec/Ia32/SecEntry.nasm b/OvmfPkg/Sec/Ia32/SecEntry.nasm >> index 54d074e621f6..1d426fafa888 100644 >> --- a/OvmfPkg/Sec/Ia32/SecEntry.nasm >> +++ b/OvmfPkg/Sec/Ia32/SecEntry.nasm >> @@ -29,6 +29,7 @@ extern ASM_PFX(SecCoreStartupWithStack) >> ; @param[in] EAX Initial value of the EAX register (BIST: Built-in Self Test) >> ; @param[in] DI 'BP': boot-strap processor, or 'AP': application processor >> ; @param[in] EBP Pointer to the start of the Boot Firmware Volume >> +; @param[in] ES Set to LINEAR_SEL in TransitionFromReal16To32BitFlat > > Can you document all the segment registers, and also document them in > UefiCpuPkg/ResetVector/Vtf0/Main.asm? Do you mean the above format (i.e., @param[in]...), just repeated for the other segment registers too? Regarding "UefiCpuPkg/ResetVector/Vtf0/Main.asm", what format do you suggest? The @param[in]... format wouldn't be right, because the segment registers are set up in TransitionFromReal16To32BitFlat. Should I write a free-form comment / list above OneTimeCall TransitionFromReal16To32BitFlat ? > >> ; >> ; @return None This routine does not return >> ; >> @@ -44,6 +45,18 @@ ASM_PFX(_ModuleEntryPoint): >> mov esp, ebx >> nop >> >> + ; >> + ; Fill the temporary RAM with the initial stack value. >> + ; The loop below will seed the heap as well, but that's harmless. >> + ; >> + mov eax, FixedPcdGet32 (PcdInitValueInTempStack) ; dword to store >> + mov edi, FixedPcdGet32 (PcdOvmfSecPeiTempRamBase) ; base address, >> + ; relative to ES >> + mov ecx, FixedPcdGet32 (PcdOvmfSecPeiTempRamSize) ; byte count >> + shr ecx, 2 ; dword count > > I'm not sure, but I think NASM might let you do something like: > > mov ecx, FixedPcdGet32 (PcdOvmfSecPeiTempRamSize) / 4 OK, I can try that. I was worried about NASM arithmetic in general, but I see the "info" page describes "Multiplication and Division", so the semantics should be well-defined. > >> + cld ; store from base up >> + rep stosd > > I think if you move this above the code in patch 1, then patch 1 is > not needed. I think I agree (to be seen in practice :) ) > I also think it would be reasonable to merge 2 & 3, but > separate is fine too. If I remove the "shr" from both, then I might feel tempted to merge them; I'm not sure yet. For testing at least I prefer to keep them separate. Thanks Laszlo