diff options
Diffstat (limited to 'MdePkg/Library/BaseLib/Ia32/Thunk16.S')
| -rw-r--r-- | MdePkg/Library/BaseLib/Ia32/Thunk16.S | 24 |
1 files changed, 11 insertions, 13 deletions
diff --git a/MdePkg/Library/BaseLib/Ia32/Thunk16.S b/MdePkg/Library/BaseLib/Ia32/Thunk16.S index 331ea1634e..185655eecb 100644 --- a/MdePkg/Library/BaseLib/Ia32/Thunk16.S +++ b/MdePkg/Library/BaseLib/Ia32/Thunk16.S @@ -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
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