-#\r
-# Copyright (c) 2014, Intel Corporation. All rights reserved.<BR>\r
-# This program and the accompanying materials\r
-# are licensed and made available under the terms and conditions of the BSD License\r
-# which accompanies this distribution. The full text of the license may be found at\r
-# http://opensource.org/licenses/bsd-license.php.\r
-#\r
-# THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
-# WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
-#\r
-#\r
-# Module Name:\r
-#\r
-# Thunk64To32.asm\r
-#\r
-# Abstract:\r
-#\r
-# This is the assembly code to transition from long mode to compatibility mode to execute 32-bit code and then\r
-# transit back to long mode.\r
-#\r
-#-------------------------------------------------------------------------------\r
-\r
-#----------------------------------------------------------------------------\r
-# Procedure: AsmExecute32BitCode\r
-#\r
-# Input: None\r
-#\r
-# Output: None\r
-#\r
-# Prototype: UINT32\r
-# AsmExecute32BitCode (\r
-# IN UINT64 Function,\r
-# IN UINT64 Param1,\r
-# IN UINT64 Param2,\r
-# IN IA32_DESCRIPTOR *InternalGdtr\r
-# );\r
-#\r
-#\r
-# Description: A thunk function to execute 32-bit code in long mode.\r
-#\r
-#----------------------------------------------------------------------------\r
-\r
-ASM_GLOBAL ASM_PFX(AsmExecute32BitCode)\r
-ASM_PFX(AsmExecute32BitCode):\r
- #\r
- # save IFLAG and disable it\r
- #\r
- pushfq\r
- cli\r
-\r
- #\r
- # save orignal GDTR and CS\r
- #\r
- movl %ds, %eax\r
- push %rax\r
- movl %cs, %eax\r
- push %rax\r
- subq $0x10, %rsp\r
- sgdt (%rsp)\r
- #\r
- # load internal GDT\r
- #\r
- lgdt (%r9)\r
- #\r
- # Save general purpose register and rflag register\r
- #\r
- pushfq\r
- push %rdi\r
- push %rsi\r
- push %rbp\r
- push %rbx\r
-\r
- #\r
- # save CR3\r
- #\r
- movq %cr3, %rax\r
- movq %rax, %rbp\r
-\r
- #\r
- # Prepare the CS and return address for the transition from 32-bit to 64-bit mode\r
- #\r
- movq $0x10, %rax # load long mode selector\r
- shl $32, %rax\r
- lea ReloadCS(%rip), %r9 #Assume the ReloadCS is under 4G\r
- orq %r9, %rax\r
- push %rax\r
- #\r
- # Save parameters for 32-bit function call\r
- #\r
- movq %r8, %rax\r
- shl $32, %rax\r
- orq %rdx, %rax\r
- push %rax\r
- #\r
- # save the 32-bit function entry and the return address into stack which will be\r
- # retrieve in compatibility mode.\r
- #\r
- lea ReturnBack(%rip), %rax #Assume the ReloadCS is under 4G\r
- shl $32, %rax\r
- orq %rcx, %rax\r
- push %rax\r
-\r
- #\r
- # let rax save DS\r
- #\r
- movq $0x18, %rax\r
-\r
- #\r
- # Change to Compatible Segment\r
- #\r
- movq $8, %rcx # load compatible mode selector\r
- shl $32, %rcx\r
- lea Compatible(%rip), %rdx # assume address < 4G\r
- orq %rdx, %rcx\r
- push %rcx\r
- .byte 0xcb # retf\r
-\r
-Compatible:\r
- # reload DS/ES/SS to make sure they are correct referred to current GDT\r
- movw %ax, %ds\r
- movw %ax, %es\r
- movw %ax, %ss\r
-\r
- #\r
- # Disable paging\r
- #\r
- movq %cr0, %rcx\r
- btc $31, %ecx\r
- movq %rcx, %cr0\r
- #\r
- # Clear EFER.LME\r
- #\r
- movl $0xC0000080, %ecx\r
- rdmsr\r
- btc $8, %eax\r
- wrmsr\r
-\r
-# Now we are in protected mode\r
- #\r
- # Call 32-bit function. Assume the function entry address and parameter value is less than 4G\r
- #\r
- pop %rax # Here is the function entry\r
- #\r
- # Now the parameter is at the bottom of the stack, then call in to IA32 function.\r
- #\r
- jmp *%rax\r
-ReturnBack:\r
- movl %eax, %ebx # save return status\r
- pop %rcx # drop param1\r
- pop %rcx # drop param2\r
-\r
- #\r
- # restore CR4\r
- #\r
- movq %cr4, %rax\r
- bts $5, %eax\r
- movq %rax, %cr4\r
-\r
- #\r
- # restore CR3\r
- #\r
- movl %ebp, %eax\r
- movq %rax, %cr3\r
-\r
- #\r
- # Set EFER.LME to re-enable ia32-e\r
- #\r
- movl $0xC0000080, %ecx\r
- rdmsr\r
- bts $8, %eax\r
- wrmsr\r
- #\r
- # Enable paging\r
- #\r
- movq %cr0, %rax\r
- bts $31, %eax\r
- mov %rax, %cr0\r
-# Now we are in compatible mode\r
-\r
- #\r
- # Reload cs register\r
- #\r
- .byte 0xcb # retf\r
-ReloadCS:\r
- #\r
- # Now we're in Long Mode\r
- #\r
- #\r
- # Restore C register and eax hold the return status from 32-bit function.\r
- # Note: Do not touch rax from now which hold the return value from IA32 function\r
- #\r
- movl %ebx, %eax # put return status to EAX\r
- pop %rbx\r
- pop %rbp\r
- pop %rsi\r
- pop %rdi\r
- popfq\r
- #\r
- # Switch to orignal GDT and CS. here rsp is pointer to the orignal GDT descriptor.\r
- #\r
- lgdt (%rsp)\r
- #\r
- # drop GDT descriptor in stack\r
- #\r
- addq $0x10, %rsp\r
- #\r
- # switch to orignal CS and GDTR\r
- #\r
- pop %r9 # get CS\r
- shl $32, %r9 # rcx[32..47] <- Cs\r
- lea ReturnToLongMode(%rip), %rcx\r
- orq %r9, %rcx\r
- push %rcx\r
- .byte 0xcb # retf\r
-ReturnToLongMode:\r
- #\r
- # Reload original DS/ES/SS\r
- #\r
- pop %rcx\r
- movl %ecx, %ds\r
- movl %ecx, %es\r
- movl %ecx, %ss\r
-\r
- #\r
- # Restore IFLAG\r
- #\r
- popfq\r
-\r
- ret\r
-\r
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