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
