1 #------------------------------------------------------------------------------
3 # Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
4 # This program and the accompanying materials
5 # are licensed and made available under the terms and conditions of the BSD License
6 # which accompanies this distribution. The full text of the license may be found at
7 # http://opensource.org/licenses/bsd-license.php
9 # THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
10 # WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
20 #------------------------------------------------------------------------------
22 #include <EdkIIGlueBase.h>
24 .globl ASM_PFX(m16Start)
25 .globl ASM_PFX(m16Size)
26 .globl ASM_PFX(mThunk16Attr)
27 .globl ASM_PFX(m16Gdt)
28 .globl ASM_PFX(m16GdtrBase)
29 .globl ASM_PFX(mTransition)
30 .globl ASM_PFX(InternalAsmThunk16)
32 # define the structure of IA32_REGS
45 .set _EFLAGS, 40 #size 8
49 .set IA32_REGS_SIZE, 56
54 ASM_PFX(m16Size): .word ASM_PFX(InternalAsmThunk16) - ASM_PFX(m16Start)
55 ASM_PFX(mThunk16Attr): .word _ThunkAttr - ASM_PFX(m16Start)
56 ASM_PFX(m16Gdt): .word ASM_PFX(NullSeg) - ASM_PFX(m16Start)
57 ASM_PFX(m16GdtrBase): .word _16GdtrBase - ASM_PFX(m16Start)
58 ASM_PFX(mTransition): .word _EntryPoint - ASM_PFX(m16Start)
67 #------------------------------------------------------------------------------
68 # _BackFromUserCode() takes control in real mode after 'retf' has been executed
69 # by user code. It will be shadowed to somewhere in memory below 1MB.
70 #------------------------------------------------------------------------------
71 .globl ASM_PFX(BackFromUserCode)
72 ASM_PFX(BackFromUserCode):
77 # The order of saved registers on the stack matches the order they appears
78 # in IA32_REGS structure. This facilitates wrapper function to extract them
79 # into that structure.
81 # Some instructions for manipulation of segment registers have to be written
82 # in opcode since 64-bit MASM prevents accesses to those registers.
87 call L_Base # push eip
90 pushq $0 # reserved high order 32 bits of EFlags
91 .byte 0x66, 0x9c # pushfd actually
92 cli # disable interrupts
97 .byte 0x66,0x60 # pushad
98 .byte 0x66,0xba # mov edx, imm32
100 testb $THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15, %dl
102 movl $0x15cd2401,%eax # mov ax, 2401h & int 15h
103 cli # disable interrupts
106 testb $THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL, %dl
110 outb %al, $0x92 # deactivate A20M#
113 lea IA32_REGS_SIZE(%esp), %bp
115 # rsi in the following 2 instructions is indeed bp in 16-bit code
117 movw %bp, (_ESP - IA32_REGS_SIZE)(%rsi)
119 movl (_EIP - IA32_REGS_SIZE)(%rsi), %ebx
120 shlw $4,%ax # shl eax, 4
121 addw %ax,%bp # add ebp, eax
124 lea (L_64BitCode - L_Base)(%ebx, %eax), %ax
125 .byte 0x66,0x2e,0x89,0x87 # mov cs:[bx + (L_64Eip - L_Base)], eax
126 .word L_64Eip - L_Base
127 .byte 0x66,0xb8 # mov eax, imm32
131 # rdi in the instruction below is indeed bx in 16-bit code
133 .byte 0x66,0x2e # 2eh is "cs:" segment override
134 lgdt (SavedGdt - L_Base)(%rdi)
136 movl $0xc0000080,%ecx
140 .byte 0x66,0xb8 # mov eax, imm32
143 .byte 0x66,0xea # jmp far cs:L_64Bit
148 .byte 0x67,0xbc # mov esp, imm32
149 SavedSp: .space 4 # restore stack
155 _EntryPoint: .long ASM_PFX(ToUserCode) - ASM_PFX(m16Start)
157 _16Gdtr: .word GDT_SIZE - 1
158 _16GdtrBase: .quad ASM_PFX(NullSeg)
163 #------------------------------------------------------------------------------
164 # _ToUserCode() takes control in real mode before passing control to user code.
165 # It will be shadowed to somewhere in memory below 1MB.
166 #------------------------------------------------------------------------------
167 .globl ASM_PFX(ToUserCode)
172 movl %edx,%ss # set new segment selectors
178 movl $0xc0000080,%ecx
181 andb $0b11111110, %ah
184 movl %esi,%ss # set up 16-bit stack segment
185 movw %bx,%sp # set up 16-bit stack pointer
186 .byte 0x66 # make the following call 32-bit
187 call L_Base1 # push eip
189 popw %bp # ebp <- address of L_Base1
190 pushq (IA32_REGS_SIZE + 2)(%esp)
193 lret # execution begins at next instruction
195 .byte 0x66,0x2e # CS and operand size override
196 lidt (_16Idtr - L_Base1)(%rsi)
197 .byte 0x66,0x61 # popad
200 .byte 0x0f, 0xa1 # pop fs
201 .byte 0x0f, 0xa9 # pop gs
202 .byte 0x66, 0x9d # popfd
203 leaw 4(%esp),%sp # skip high order 32 bits of EFlags
204 .byte 0x66 # make the following retf 32-bit
206 lret # transfer control to user code
208 .set CODE16, ASM_PFX(_16Code) - .
209 .set DATA16, ASM_PFX(_16Data) - .
210 .set DATA32, ASM_PFX(_32Data) - .
212 ASM_PFX(NullSeg): .quad 0
218 .byte 0x8f # 16-bit segment, 4GB limit
225 .byte 0x8f # 16-bit segment, 4GB limit
232 .byte 0xcf # 16-bit segment, 4GB limit
235 .set GDT_SIZE, . - ASM_PFX(NullSeg)
237 #------------------------------------------------------------------------------
238 # IA32_REGISTER_SET *
240 # InternalAsmThunk16 (
241 # IN IA32_REGISTER_SET *RegisterSet,
242 # IN OUT VOID *Transition
244 #------------------------------------------------------------------------------
246 .globl ASM_PFX(InternalAsmThunk16)
247 ASM_PFX(InternalAsmThunk16):
257 pushq %rbx # Save ds segment register on the stack
259 pushq %rbx # Save es segment register on the stack
261 pushq %rbx # Save ss segment register on the stack
263 .byte 0x0f, 0xa0 #push fs
264 .byte 0x0f, 0xa8 #push gs
266 movzwl _SS(%rsi), %r8d
267 movl _ESP(%rsi), %edi
268 lea -(IA32_REGS_SIZE + 4)(%edi), %rdi
270 movl %edi,%ebx # ebx <- stack for 16-bit code
271 pushq $(IA32_REGS_SIZE / 4)
272 addl %eax,%edi # edi <- linear address of 16-bit stack
276 lea (SavedCr4 - ASM_PFX(m16Start))(%rdx), %ecx
277 movl %edx,%eax # eax <- transition code address
279 shll $12,%eax # segment address in high order 16 bits
280 lea (_BackFromUserCode - ASM_PFX(m16Start))(%rdx), %ax
281 stosl # [edi] <- return address of user code
282 sgdt (SavedGdt - SavedCr4)(%rcx)
285 movl %eax, (SavedCr0 - SavedCr4)(%rcx)
286 andl $0x7ffffffe,%eax # clear PE, PG bits
288 movl %ebp, (%rcx) # save CR4 in SavedCr4
289 andl $0x300,%ebp # clear all but PCE and OSFXSR bits
290 movl %r8d, %esi # esi <- 16-bit stack segment
293 lgdt (_16Gdtr - SavedCr4)(%rcx)
297 lea L_RetFromRealMode, %r8
300 movw %r8w, (SavedCs - SavedCr4)(%rcx)
301 movl %esp, (SavedSp - SavedCr4)(%rcx)
302 .byte 0xff, 0x69 # jmp (_EntryPoint - SavedCr4)(%rcx)
303 .byte _EntryPoint - SavedCr4
307 lea -IA32_REGS_SIZE(%rbp), %eax
308 .byte 0x0f, 0xa9 # pop gs
309 .byte 0x0f, 0xa1 # pop fs