diff options
Diffstat (limited to 'IntelFspWrapperPkg/Library/BaseFspApiLib/X64/Thunk64To32.S')
| -rw-r--r-- | IntelFspWrapperPkg/Library/BaseFspApiLib/X64/Thunk64To32.S | 230 |
1 files changed, 230 insertions, 0 deletions
diff --git a/IntelFspWrapperPkg/Library/BaseFspApiLib/X64/Thunk64To32.S b/IntelFspWrapperPkg/Library/BaseFspApiLib/X64/Thunk64To32.S new file mode 100644 index 000000000..b6b5c1aca --- /dev/null +++ b/IntelFspWrapperPkg/Library/BaseFspApiLib/X64/Thunk64To32.S @@ -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.
+#
+#-------------------------------------------------------------------------------
+
+#----------------------------------------------------------------------------
+# 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.
+#
+#----------------------------------------------------------------------------
+
+ASM_GLOBAL ASM_PFX(AsmExecute32BitCode)
+ASM_PFX(AsmExecute32BitCode):
+ #
+ # save IFLAG and disable it
+ #
+ pushfq
+ cli
+
+ #
+ # save orignal GDTR and CS
+ #
+ movl %ds, %eax
+ push %rax
+ movl %cs, %eax
+ push %rax
+ subq $0x10, %rsp
+ sgdt (%rsp)
+ #
+ # load internal GDT
+ #
+ lgdt (%r9)
+ #
+ # Save general purpose register and rflag register
+ #
+ pushfq
+ push %rdi
+ push %rsi
+ push %rbp
+ push %rbx
+
+ #
+ # save CR3
+ #
+ movq %cr3, %rax
+ movq %rax, %rbp
+
+ #
+ # Prepare the CS and return address for the transition from 32-bit to 64-bit mode
+ #
+ movq $0x10, %rax # load long mode selector
+ shl $32, %rax
+ lea ReloadCS(%rip), %r9 #Assume the ReloadCS is under 4G
+ orq %r9, %rax
+ push %rax
+ #
+ # Save parameters for 32-bit function call
+ #
+ movq %r8, %rax
+ shl $32, %rax
+ orq %rdx, %rax
+ push %rax
+ #
+ # save the 32-bit function entry and the return address into stack which will be
+ # retrieve in compatibility mode.
+ #
+ lea ReturnBack(%rip), %rax #Assume the ReloadCS is under 4G
+ shl $32, %rax
+ orq %rcx, %rax
+ push %rax
+
+ #
+ # let rax save DS
+ #
+ movq $0x18, %rax
+
+ #
+ # Change to Compatible Segment
+ #
+ movq $8, %rcx # load compatible mode selector
+ shl $32, %rcx
+ lea Compatible(%rip), %rdx # assume address < 4G
+ orq %rdx, %rcx
+ push %rcx
+ .byte 0xcb # retf
+
+Compatible:
+ # reload DS/ES/SS to make sure they are correct referred to current GDT
+ movw %ax, %ds
+ movw %ax, %es
+ movw %ax, %ss
+
+ #
+ # Disable paging
+ #
+ movq %cr0, %rcx
+ btc $31, %ecx
+ movq %rcx, %cr0
+ #
+ # Clear EFER.LME
+ #
+ movl $0xC0000080, %ecx
+ rdmsr
+ btc $8, %eax
+ 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:
+ movl %eax, %ebx # save return status
+ pop %rcx # drop param1
+ pop %rcx # drop param2
+
+ #
+ # restore CR4
+ #
+ movq %cr4, %rax
+ bts $5, %eax
+ movq %rax, %cr4
+
+ #
+ # restore CR3
+ #
+ movl %ebp, %eax
+ movq %rax, %cr3
+
+ #
+ # Set EFER.LME to re-enable ia32-e
+ #
+ movl $0xC0000080, %ecx
+ rdmsr
+ bts $8, %eax
+ wrmsr
+ #
+ # Enable paging
+ #
+ movq %cr0, %rax
+ bts $31, %eax
+ mov %rax, %cr0
+# Now we are in compatible mode
+
+ #
+ # Reload cs register
+ #
+ .byte 0xcb # 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
+ #
+ movl %ebx, %eax # 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 (%rsp)
+ #
+ # drop GDT descriptor in stack
+ #
+ addq $0x10, %rsp
+ #
+ # switch to orignal CS and GDTR
+ #
+ pop %r9 # get CS
+ shl $32, %r9 # rcx[32..47] <- Cs
+ lea ReturnToLongMode(%rip), %rcx
+ orq %r9, %rcx
+ push %rcx
+ .byte 0xcb # retf
+ReturnToLongMode:
+ #
+ # Reload original DS/ES/SS
+ #
+ pop %rcx
+ movl %ecx, %ds
+ movl %ecx, %es
+ movl %ecx, %ss
+
+ #
+ # Restore IFLAG
+ #
+ popfq
+
+ ret
+
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