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Save segment registers on stack in case the thunk code assembly calls CF9 soft reset and the x64 registers get cleared.

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git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@8123 6f19259b-4bc3-4df7-8a09-765794883524
This commit is contained in:
qhuang8
2009-04-17 07:38:57 +00:00
parent 14ca06407d
commit 0fe43214e3
2 changed files with 42 additions and 22 deletions
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34
MdePkg/Library/BaseLib/X64/Thunk16.S
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@@ -136,10 +136,13 @@ SavedCr4: .space 4
SavedCr0: .space 4
movq %rax, %cr0
.byte 0x66,0xea # jmp far cs:L_64Bit
L_64Eip: .space 4
L_64Eip: .space 4
SavedCs: .space 2
L_64BitCode:
movq %r8, %rsp
.byte 0x90
.byte 0x67,0xbc # mov esp, imm32
SavedSp: .space 4 # restore stack
nop
ret
_EntryPoint: .long ASM_PFX(ToUserCode) - ASM_PFX(m16Start)
@@ -227,7 +230,6 @@ ASM_PFX(_32Data):
# IN OUT VOID *Transition
# );
#------------------------------------------------------------------------------
# MISMATCH: "InternalAsmThunk16 PROC USES rbp rbx rsi rdi"
.globl ASM_PFX(InternalAsmThunk16)
ASM_PFX(InternalAsmThunk16):
@@ -236,9 +238,13 @@ ASM_PFX(InternalAsmThunk16):
pushq %rsi
pushq %rdi
movl %ds, %r10d # r9 ~ r11 are not accessible in 16-bit
movl %es, %r11d # so use them for saving seg registers
movl %ss, %r9d
movq %ds, %rbx
pushq %rbx # Save ds segment register on the stack
movq %es, %rbx
pushq %rbx # Save es segment register on the stack
movq %ss, %rbx
pushq %rbx # Save ss segment register on the stack
.byte 0x0f, 0xa0 #push fs
.byte 0x0f, 0xa8 #push gs
movq %rcx, %rsi
@@ -259,7 +265,7 @@ ASM_PFX(InternalAsmThunk16):
lea (_BackFromUserCode - ASM_PFX(m16Start))(%rdx), %ax
stosl # [edi] <- return address of user code
sgdt (SavedGdt - SavedCr4)(%rcx)
sidt 0x38(%rsp)
sidt 0x50(%rsp)
movq %cr0, %rax
movl %eax, (SavedCr0 - SavedCr4)(%rcx)
andl $0x7ffffffe,%eax # clear PE, PG bits
@@ -277,18 +283,22 @@ ASM_PFX(InternalAsmThunk16):
pushq %r8
movl %cs, %r8d
movw %r8w, (SavedCs - SavedCr4)(%rcx)
movq %rsp, %r8
movl %esp, (SavedSp - SavedCr4)(%rcx)
.byte 0xff, 0x69 # jmp (_EntryPoint - SavedCr4)(%rcx)
.byte _EntryPoint - SavedCr4
L_RetFromRealMode:
popfq
lidt 0x38(%rsp)
lidt 0x50(%rsp)
lea -IA32_REGS_SIZE(%rbp), %eax
.byte 0x0f, 0xa9 # pop gs
.byte 0x0f, 0xa1 # pop fs
movl %r9d, %ss
movl %r11d, %es
movl %r10d, %ds
popq %rbx
movq %rbx, %ss
popq %rbx
movq %rbx, %es
popq %rbx
movq %rbx, %ds
popq %rdi
popq %rsi