diff options
Diffstat (limited to 'IntelFsp2WrapperPkg/Library/BaseFspWrapperApiLib/X64/Thunk64To32.asm')
| -rw-r--r-- | IntelFsp2WrapperPkg/Library/BaseFspWrapperApiLib/X64/Thunk64To32.asm | 230 |
1 files changed, 230 insertions, 0 deletions
diff --git a/IntelFsp2WrapperPkg/Library/BaseFspWrapperApiLib/X64/Thunk64To32.asm b/IntelFsp2WrapperPkg/Library/BaseFspWrapperApiLib/X64/Thunk64To32.asm new file mode 100644 index 0000000000..70e7b5f408 --- /dev/null +++ b/IntelFsp2WrapperPkg/Library/BaseFspWrapperApiLib/X64/Thunk64To32.asm @@ -0,0 +1,230 @@ +;
+; Copyright (c) 2014, Intel Corporation. All rights reserved.<BR>
+; This program and the accompanying materials
+; are licensed and made available under the terms and conditions of the BSD License
+; which accompanies this distribution. The full text of the license may be found at
+; http://opensource.org/licenses/bsd-license.php.
+;
+; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+;
+;
+; Module Name:
+;
+; Thunk64To32.asm
+;
+; Abstract:
+;
+; This is the assembly code to transition from long mode to compatibility mode to execute 32-bit code and then
+; transit back to long mode.
+;
+;-------------------------------------------------------------------------------
+ .code
+;----------------------------------------------------------------------------
+; Procedure: AsmExecute32BitCode
+;
+; Input: None
+;
+; Output: None
+;
+; Prototype: UINT32
+; AsmExecute32BitCode (
+; IN UINT64 Function,
+; IN UINT64 Param1,
+; IN UINT64 Param2,
+; IN IA32_DESCRIPTOR *InternalGdtr
+; );
+;
+;
+; Description: A thunk function to execute 32-bit code in long mode.
+;
+;----------------------------------------------------------------------------
+AsmExecute32BitCode PROC
+ ;
+ ; save IFLAG and disable it
+ ;
+ pushfq
+ cli
+
+ ;
+ ; save orignal GDTR and CS
+ ;
+ mov rax, ds
+ push rax
+ mov rax, cs
+ push rax
+ sub rsp, 10h
+ sgdt fword ptr [rsp]
+ ;
+ ; load internal GDT
+ ;
+ lgdt fword ptr [r9]
+ ;
+ ; Save general purpose register and rflag register
+ ;
+ pushfq
+ push rdi
+ push rsi
+ push rbp
+ push rbx
+
+ ;
+ ; save CR3
+ ;
+ mov rax, cr3
+ mov rbp, rax
+
+ ;
+ ; Prepare the CS and return address for the transition from 32-bit to 64-bit mode
+ ;
+ mov rax, 10h ; load long mode selector
+ shl rax, 32
+ mov r9, OFFSET ReloadCS ;Assume the ReloadCS is under 4G
+ or rax, r9
+ push rax
+ ;
+ ; Save parameters for 32-bit function call
+ ;
+ mov rax, r8
+ shl rax, 32
+ or rax, rdx
+ push rax
+ ;
+ ; save the 32-bit function entry and the return address into stack which will be
+ ; retrieve in compatibility mode.
+ ;
+ mov rax, OFFSET ReturnBack ;Assume the ReloadCS is under 4G
+ shl rax, 32
+ or rax, rcx
+ push rax
+
+ ;
+ ; let rax save DS
+ ;
+ mov rax, 018h
+
+ ;
+ ; Change to Compatible Segment
+ ;
+ mov rcx, 08h ; load compatible mode selector
+ shl rcx, 32
+ mov rdx, OFFSET Compatible ; assume address < 4G
+ or rcx, rdx
+ push rcx
+ retf
+
+Compatible:
+ ; reload DS/ES/SS to make sure they are correct referred to current GDT
+ mov ds, ax
+ mov es, ax
+ mov ss, ax
+
+ ;
+ ; Disable paging
+ ;
+ mov rcx, cr0
+ btc ecx, 31
+ mov cr0, rcx
+ ;
+ ; Clear EFER.LME
+ ;
+ mov ecx, 0C0000080h
+ rdmsr
+ btc eax, 8
+ wrmsr
+
+; Now we are in protected mode
+ ;
+ ; Call 32-bit function. Assume the function entry address and parameter value is less than 4G
+ ;
+ pop rax ; Here is the function entry
+ ;
+ ; Now the parameter is at the bottom of the stack, then call in to IA32 function.
+ ;
+ jmp rax
+ReturnBack:
+ mov ebx, eax ; save return status
+ pop rcx ; drop param1
+ pop rcx ; drop param2
+
+ ;
+ ; restore CR4
+ ;
+ mov rax, cr4
+ bts eax, 5
+ mov cr4, rax
+
+ ;
+ ; restore CR3
+ ;
+ mov eax, ebp
+ mov cr3, rax
+
+ ;
+ ; Set EFER.LME to re-enable ia32-e
+ ;
+ mov ecx, 0C0000080h
+ rdmsr
+ bts eax, 8
+ wrmsr
+ ;
+ ; Enable paging
+ ;
+ mov rax, cr0
+ bts eax, 31
+ mov cr0, rax
+; Now we are in compatible mode
+
+ ;
+ ; Reload cs register
+ ;
+ retf
+ReloadCS:
+ ;
+ ; Now we're in Long Mode
+ ;
+ ;
+ ; Restore C register and eax hold the return status from 32-bit function.
+ ; Note: Do not touch rax from now which hold the return value from IA32 function
+ ;
+ mov eax, ebx ; put return status to EAX
+ pop rbx
+ pop rbp
+ pop rsi
+ pop rdi
+ popfq
+ ;
+ ; Switch to orignal GDT and CS. here rsp is pointer to the orignal GDT descriptor.
+ ;
+ lgdt fword ptr[rsp]
+ ;
+ ; drop GDT descriptor in stack
+ ;
+ add rsp, 10h
+ ;
+ ; switch to orignal CS and GDTR
+ ;
+ pop r9 ; get CS
+ shl r9, 32 ; rcx[32..47] <- Cs
+ mov rcx, OFFSET @F
+ or rcx, r9
+ push rcx
+ retf
+@@:
+ ;
+ ; Reload original DS/ES/SS
+ ;
+ pop rcx
+ mov ds, rcx
+ mov es, rcx
+ mov ss, rcx
+
+ ;
+ ; Restore IFLAG
+ ;
+ popfq
+
+ ret
+AsmExecute32BitCode ENDP
+
+ END
|