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MdePkg: First instruction after clearing CR0.PE must be a far jmp.

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Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15029 6f19259b-4bc3-4df7-8a09-765794883524
This commit is contained in:
David Woodhouse
2013-12-30 01:14:13 +00:00
committed by lgao4
parent 321c89c208
commit af8aa62d59
2 changed files with 35 additions and 29 deletions
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24
MdePkg/Library/BaseLib/Ia32/Thunk16.S
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@@ -113,22 +113,18 @@ ASM_PFX(ToUserCode):
movw %cx, %es
movw %cx, %fs
movw %cx, %gs
movl %eax, %cr0
movl %ebp, %cr4 # real mode starts at next instruction
movl %eax, %cr0 # real mode starts at next instruction
# which (per SDM) *must* be a far JMP.
ljmpw $0,$0 # will be filled in by InternalAsmThunk16
L_Base: # to point here.
movl %ebp, %cr4
movw %si, %ss # set up 16-bit stack segment
xchgl %ebx, %esp # set up 16-bit stack pointer
calll L_Base # push eip
L_Base:
popl %ebp # ebp <- offset L_Base
push (IA32_REGS_SIZE + 2)(%esp)
lea (L_RealMode - L_Base)(%bp), %ax
push %ax
lret
L_RealMode:
mov %dx, %cs:(SavedSs - L_Base)(%bp)
mov %ebx, %cs:(SavedEsp - L_Base)(%bp)
lidtl %cs:(_16Idtr - L_Base)(%bp)
movw IA32_REGS_SIZE(%esp), %bp # get BackToUserCode address from stack
mov %dx, %cs:(SavedSs - ASM_PFX(BackFromUserCode))(%bp)
mov %ebx, %cs:(SavedEsp - ASM_PFX(BackFromUserCode))(%bp)
lidtl %cs:(_16Idtr - ASM_PFX(BackFromUserCode))(%bp)
popal
pop %ds
pop %es
@@ -189,6 +185,8 @@ ASM_PFX(InternalAsmThunk16):
lea (ASM_PFX(BackFromUserCode) - ASM_PFX(m16Start))(%ecx), %ecx
movw %cx, %ax
stosl # [edi] <- return address of user code
addl $(L_Base - ASM_PFX(BackFromUserCode)), %eax
movl %eax, (L_Base - SavedCr0 - 4)(%edx)
sgdtl (SavedGdt - SavedCr0)(%edx)
sidtl 0x24(%esp)
movl %cr0, %eax