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 <ler...@redhat.com>; edk2-devel-01 >> <edk2-devel@lists.01.org>; Kinney, Michael D >> <michael.d.kin...@intel.com> >> Cc: Ni, Ruiyu <ruiyu...@intel.com>; Paolo Bonzini >> <pbonz...@redhat.com>; Yao, Jiewen >> <jiewen....@intel.com>; Dong, Eric <eric.d...@intel.com> >> 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- >> boun...@lists.01.org] >>> On Behalf Of Laszlo Ersek >>> Sent: Tuesday, January 30, 2018 10:17 AM >>> To: Kinney, Michael D <michael.d.kin...@intel.com>; >> edk2- >>> devel-01 <edk2-devel@lists.01.org> >>> Cc: Ni, Ruiyu <ruiyu...@intel.com>; Paolo Bonzini >>> <pbonz...@redhat.com>; Yao, Jiewen >>> <jiewen....@intel.com>; Dong, Eric >> <eric.d...@intel.com> >>> 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- >>> boun...@lists.01.org] >>>>> On Behalf Of Laszlo Ersek >>>>> Sent: Tuesday, January 30, 2018 7:34 AM >>>>> To: edk2-devel-01 <edk2-devel@lists.01.org> >>>>> Cc: Ni, Ruiyu <ruiyu...@intel.com>; Yao, Jiewen >>>>> <jiewen....@intel.com>; Dong, Eric >>> <eric.d...@intel.com>; >>>>> Paolo Bonzini <pbonz...@redhat.com> >>>>> 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 <eric.d...@intel.com> >>>>> Cc: Jian J Wang <jian.j.w...@intel.com> >>>>> Cc: Jiewen Yao <jiewen....@intel.com> >>>>> Cc: Paolo Bonzini <pbonz...@redhat.com> >>>>> Cc: Ruiyu Ni <ruiyu...@intel.com> >>>>> Contributed-under: TianoCore Contribution Agreement >>> 1.1 >>>>> Signed-off-by: Laszlo Ersek <ler...@redhat.com> >>>>> --- >>>>> 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 _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
