Re: [PATCH 1/3] UefiCpuPkg/PiSmmCpuDxeSmm: update comments in IA32 SmmStartup()

["Kinney, Michael D" <michael.d.kinney@intel.com>]

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());

Mike

> -----Original Message-----
> From: Kinney, Michael D
> Sent: Tuesday, January 30, 2018 12:31 PM
> To: Laszlo Ersek <lersek@redhat.com>; edk2-devel-01
> <edk2-devel@lists.01.org>; Kinney, Michael D
> <michael.d.kinney@intel.com>
> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Paolo Bonzini
> <pbonzini@redhat.com>; Yao, Jiewen
> <jiewen.yao@intel.com>; Dong, Eric <eric.dong@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-
> bounces@lists.01.org]
> > On Behalf Of Laszlo Ersek
> > Sent: Tuesday, January 30, 2018 10:17 AM
> > To: Kinney, Michael D <michael.d.kinney@intel.com>;
> edk2-
> > devel-01 <edk2-devel@lists.01.org>
> > Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Paolo Bonzini
> > <pbonzini@redhat.com>; Yao, Jiewen
> > <jiewen.yao@intel.com>; Dong, Eric
> <eric.dong@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-
> > bounces@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.ni@intel.com>; Yao, Jiewen
> > >> <jiewen.yao@intel.com>; Dong, Eric
> > <eric.dong@intel.com>;
> > >> Paolo Bonzini <pbonzini@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.dong@intel.com>
> > >> Cc: Jian J Wang <jian.j.wang@intel.com>
> > >> Cc: Jiewen Yao <jiewen.yao@intel.com>
> > >> Cc: Paolo Bonzini <pbonzini@redhat.com>
> > >> Cc: Ruiyu Ni <ruiyu.ni@intel.com>
> > >> Contributed-under: TianoCore Contribution Agreement
> > 1.1
> > >> Signed-off-by: Laszlo Ersek <lersek@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
> > >>
> > >>
> > >> _______________________________________________
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> > >> edk2-devel@lists.01.org
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> >
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