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 9D55B223648AD for ; Tue, 30 Jan 2018 13:50:20 -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 A761E9D50B; Tue, 30 Jan 2018 21:55:55 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (ovpn-120-185.rdu2.redhat.com [10.10.120.185]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2CDCB6363D; Tue, 30 Jan 2018 21:55:53 +0000 (UTC) To: "Kinney, Michael D" , edk2-devel-01 Cc: "Ni, Ruiyu" , Paolo Bonzini , "Yao, Jiewen" , "Dong, Eric" References: <20180130153348.31992-1-lersek@redhat.com> <20180130153348.31992-2-lersek@redhat.com> <31138ce7-0637-a755-ec57-e36ab812f259@redhat.com> From: Laszlo Ersek Message-ID: Date: Tue, 30 Jan 2018 22:55:53 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: 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 [10.5.110.39]); Tue, 30 Jan 2018 21:55:55 +0000 (UTC) Subject: Re: [PATCH 1/3] UefiCpuPkg/PiSmmCpuDxeSmm: update comments in IA32 SmmStartup() X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 30 Jan 2018 21:50:21 -0000 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 01/30/18 22:26, Kinney, Michael D wrote: > Laszlo, > > Maybe we can add a macro to help: > > #define PATCH_X86_ASM(Label,Type,Value) *((Type *)(&Label) - 1) = (Type)(Value) > > PATCH_X86_ASM (gSmmCr0, UINT32, AsmReadCr0()); Before sending my previous email, I thought of something like this. Here I slightly dislike: - the unaligned access to a wider-than-byte object - the larger potential for triggering undefined behavior in the C language implementation (due to type punning) -- doing the arithmetic in UINTN and using CopyMem for the data movement should mitigate that - the requirement that the object to patch has to be followed by the same number of bytes (otherwise linking might fail, I think). For example if we'd like to patch 4 bytes at the very end of the assembly code, e.g. in a jmp instruction, we'd have to match that with a DD, just so the extern UINT32 global variable could be declared and linked. I think requiring just one byte trailing padding and making all such markers UINT8 is easier to handle - the requirement that the declared type of "gSmmCr0" match the type passed to the macro as 2nd argument That said, I'm fine using either of PATCH_X86_ASM() and PatchAssembly(). Thanks! Laszlo > > Mike > >> -----Original Message----- >> From: Kinney, Michael D >> Sent: Tuesday, January 30, 2018 12:31 PM >> To: Laszlo Ersek ; edk2-devel-01 >> ; Kinney, Michael D >> >> Cc: Ni, Ruiyu ; Paolo Bonzini >> ; Yao, Jiewen >> ; Dong, Eric >> Subject: RE: [edk2] [PATCH 1/3] >> UefiCpuPkg/PiSmmCpuDxeSmm: update comments in IA32 >> SmmStartup() >> >> Laszlo, >> >> We have already used this technique in other NASM files >> to remove DBs. >> >> Let us know if you have suggestions on how to make the >> C code that performs the patches easier to read and >> maintain. >> >> Mike >> >>> -----Original Message----- >>> From: edk2-devel [mailto:edk2-devel- >> bounces@lists.01.org] >>> On Behalf Of Laszlo Ersek >>> Sent: Tuesday, January 30, 2018 10:17 AM >>> To: Kinney, Michael D ; >> edk2- >>> devel-01 >>> Cc: Ni, Ruiyu ; Paolo Bonzini >>> ; Yao, Jiewen >>> ; Dong, Eric >> >>> Subject: Re: [edk2] [PATCH 1/3] >>> UefiCpuPkg/PiSmmCpuDxeSmm: update comments in IA32 >>> SmmStartup() >>> >>> On 01/30/18 18:22, Kinney, Michael D wrote: >>>> Laszlo, >>>> >>>> The DBs can be removed if the label is moved after >>>> the instruction and the patch is done to the label >>>> minus the size of the patch value. >>> >>> Indeed I haven't thought of this. >>> >>> If I understand correctly, it means >>> >>> extern UINT8 gSmmCr0; >>> >>> *(UINT32*)(&gSmmCr0 - sizeof (UINT32)) = >>> (UINT32)AsmReadCr0 (); >>> >>> TBH, the DB feels less ugly to me than this :) >>> >>> Still, if you think it would be an acceptable price to >>> pay for removing >>> the remaining DBs, I can respin. >>> >>> Thanks >>> Laszlo >>> >>>>> -----Original Message----- >>>>> From: edk2-devel [mailto:edk2-devel- >>> bounces@lists.01.org] >>>>> On Behalf Of Laszlo Ersek >>>>> Sent: Tuesday, January 30, 2018 7:34 AM >>>>> To: edk2-devel-01 >>>>> Cc: Ni, Ruiyu ; Yao, Jiewen >>>>> ; Dong, Eric >>> ; >>>>> Paolo Bonzini >>>>> Subject: [edk2] [PATCH 1/3] >> UefiCpuPkg/PiSmmCpuDxeSmm: >>>>> update comments in IA32 SmmStartup() >>>>> >>>>> The gSmmCr3, gSmmCr4, gSmmCr0 and gSmmJmpAddr global >>>>> variables are used >>>>> for patching assembly instructions, thus we can >> never >>>>> remove the DB >>>>> encodings for those instructions. At least we should >>> add >>>>> the intended >>>>> meanings in comments. >>>>> >>>>> This patch only changes comments. >>>>> >>>>> Cc: Eric Dong >>>>> Cc: Jian J Wang >>>>> Cc: Jiewen Yao >>>>> Cc: Paolo Bonzini >>>>> Cc: Ruiyu Ni >>>>> Contributed-under: TianoCore Contribution Agreement >>> 1.1 >>>>> Signed-off-by: Laszlo Ersek >>>>> --- >>>>> UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.nasm | 8 >> ++++- >>> --- >>>>> 1 file changed, 4 insertions(+), 4 deletions(-) >>>>> >>>>> diff --git >>> a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.nasm >>>>> b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.nasm >>>>> index e96dd8d2392a..08534dba64b7 100644 >>>>> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.nasm >>>>> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.nasm >>>>> @@ -44,34 +44,34 @@ global ASM_PFX(SmmStartup) >>>>> ASM_PFX(SmmStartup): >>>>> DB 0x66 >>>>> mov eax, 0x80000001 ; read >>>>> capability >>>>> cpuid >>>>> DB 0x66 >>>>> mov ebx, edx ; rdmsr >> will >>>>> change edx. keep it in ebx. >>>>> - DB 0x66, 0xb8 >>>>> + DB 0x66, 0xb8 ; mov eax, >>> imm32 >>>>> ASM_PFX(gSmmCr3): DD 0 >>>>> mov cr3, eax >>>>> DB 0x67, 0x66 >>>>> lgdt [cs:ebp + (ASM_PFX(gcSmiInitGdtr) - >>>>> ASM_PFX(SmmStartup))] >>>>> - DB 0x66, 0xb8 >>>>> + DB 0x66, 0xb8 ; mov eax, >>> imm32 >>>>> ASM_PFX(gSmmCr4): DD 0 >>>>> mov cr4, eax >>>>> DB 0x66 >>>>> mov ecx, 0xc0000080 ; IA32_EFER >>> MSR >>>>> rdmsr >>>>> DB 0x66 >>>>> test ebx, BIT20 ; check NXE >>>>> capability >>>>> jz .1 >>>>> or ah, BIT3 ; set NXE >> bit >>>>> wrmsr >>>>> .1: >>>>> - DB 0x66, 0xb8 >>>>> + DB 0x66, 0xb8 ; mov eax, >>> imm32 >>>>> ASM_PFX(gSmmCr0): DD 0 >>>>> DB 0xbf, PROTECT_MODE_DS, 0 ; mov di, >>>>> PROTECT_MODE_DS >>>>> mov cr0, eax >>>>> - DB 0x66, 0xea ; jmp far >>>>> [ptr48] >>>>> + DB 0x66, 0xea ; jmp far >>>>> [ptr48] >>>>> ASM_PFX(gSmmJmpAddr): >>>>> DD @32bit >>>>> DW PROTECT_MODE_CS >>>>> @32bit: >>>>> mov ds, edi >>>>> mov es, edi >>>>> -- >>>>> 2.14.1.3.gb7cf6e02401b >>>>> >>>>> >>>>> _______________________________________________ >>>>> edk2-devel mailing list >>>>> edk2-devel@lists.01.org >>>>> https://lists.01.org/mailman/listinfo/edk2-devel >>> >>> _______________________________________________ >>> edk2-devel mailing list >>> edk2-devel@lists.01.org >>> https://lists.01.org/mailman/listinfo/edk2-devel