Rename the variable to "gPatchSmmInitStack" so that its association with
PatchInstructionX86() is clear from the declaration, change its type to
X86_ASSEMBLY_PATCH_LABEL, and patch it with PatchInstructionX86(). This
lets us remove the binary (DB) encoding of some instructions in
"SmmInit.nasm".

The size of the patched source operand is (sizeof (UINTN)).

Cc: Eric Dong <eric.dong@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=866
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---

Notes:
    v2:
    - use the X86_ASSEMBLY_PATCH_LABEL type rather than UINT8 [Mike]

 UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h  | 2 +-
 UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.nasm | 6 +++---
 UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmInit.nasm  | 6 +++---
 UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c  | 6 +++++-
 4 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
index 856d5738c081..0281be9d88f0 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
@@ -302,7 +302,7 @@ extern UINT32                       mSmmCr0;
 X86_ASSEMBLY_PATCH_LABEL            gPatchSmmCr3;
 extern UINT32                       mSmmCr4;
 X86_ASSEMBLY_PATCH_LABEL            gPatchSmmCr4;
-extern UINTN                        gSmmInitStack;
+X86_ASSEMBLY_PATCH_LABEL            gPatchSmmInitStack;
 
 /**
   Semaphore operation for all processor relocate SMMBase.
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.nasm b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.nasm
index f59413d9d4a3..5ff3cd2e731f 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.nasm
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.nasm
@@ -25,7 +25,7 @@ extern ASM_PFX(mSmmRelocationOriginalAddress)
 global ASM_PFX(gPatchSmmCr3)
 global ASM_PFX(gPatchSmmCr4)
 global ASM_PFX(gPatchSmmCr0)
-global ASM_PFX(gSmmInitStack)
+global ASM_PFX(gPatchSmmInitStack)
 global ASM_PFX(gcSmiInitGdtr)
 global ASM_PFX(gcSmmInitSize)
 global ASM_PFX(gcSmmInitTemplate)
@@ -72,8 +72,8 @@ BITS 32
     mov     fs, edi
     mov     gs, edi
     mov     ss, edi
-    DB      0xbc                        ; mov esp, imm32
-ASM_PFX(gSmmInitStack): DD 0
+    mov     esp, strict dword 0         ; source operand will be patched
+ASM_PFX(gPatchSmmInitStack):
     call    ASM_PFX(SmmInitHandler)
     rsm
 
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmInit.nasm b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmInit.nasm
index 2460e1eb2dee..eae14c0549f0 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmInit.nasm
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmInit.nasm
@@ -25,7 +25,7 @@ extern ASM_PFX(mSmmRelocationOriginalAddress)
 global ASM_PFX(gPatchSmmCr3)
 global ASM_PFX(gPatchSmmCr4)
 global ASM_PFX(gPatchSmmCr0)
-global ASM_PFX(gSmmInitStack)
+global ASM_PFX(gPatchSmmInitStack)
 global ASM_PFX(gcSmiInitGdtr)
 global ASM_PFX(gcSmmInitSize)
 global ASM_PFX(gcSmmInitTemplate)
@@ -72,8 +72,8 @@ ASM_PFX(gPatchSmmCr0):
 
 BITS 64
 @LongMode:                              ; long-mode starts here
-    DB      0x48, 0xbc                   ; mov rsp, imm64
-ASM_PFX(gSmmInitStack): DQ 0
+    mov     rsp, strict qword 0         ; source operand will be patched
+ASM_PFX(gPatchSmmInitStack):
     and     sp, 0xfff0                  ; make sure RSP is 16-byte aligned
     ;
     ; Accoring to X64 calling convention, XMM0~5 are volatile, we need to save
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
index 0c8a4543d865..fbf74e8d90f9 100755
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
@@ -848,7 +848,11 @@ PiCpuSmmEntry (
   //
   // Set SMI stack for SMM base relocation
   //
-  gSmmInitStack = (UINTN) (Stacks + mSmmStackSize - sizeof (UINTN));
+  PatchInstructionX86 (
+    gPatchSmmInitStack,
+    (UINTN) (Stacks + mSmmStackSize - sizeof (UINTN)),
+    sizeof (UINTN)
+    );
 
   //
   // Initialize IDT
-- 
2.14.1.3.gb7cf6e02401b


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