The source code may have a problem when the IDT is initialized.
This code is located in `src/cpu/x86/16bit/entry16.inc`.
----------------------------------------------------------------------------------------------
movw %cs, %ax
shlw $4, %ax
movw $nullidt_offset, %bx
subw %ax, %bx
lidt %cs:(%bx) —> this mybe lidtl
movw $gdtptr16_offset, %bx
subw %ax, %bx
lgdtl %cs:(%bx)
----------------------------------------------------------------------------------------------
lidt only used for base 0-16M.
But nullidt located in (4G-64k) - 4G space.
This instruct must be **lidtl**
Description of LIDT
IF Instruction is LIDT THEN IF OperandSize = 16 THEN
IDTR(Limit) ← SRC[0:15]; IDTR(Base) ←
SRC[16:47] AND 00FFFFFFH; ELSE IF 32-bit Operand Size
THEN IDTR(Limit) ← SRC[0:15];
IDTR(Base) ← SRC[16:47]; FI; ELSE IF
64-bit Operand Size (* In 64-Bit Mode *) THEN
IDTR(Limit) ← SRC[0:15]; IDTR(Base) ←
SRC[16:79]; FI; FI; ELSE (* Instruction is
LGDT *) IF OperandSize = 16 THEN
GDTR(Limit) ← SRC[0:15]; GDTR(Base) ← SRC[16:47] AND
00FFFFFFH; ELSE IF 32-bit Operand Size THEN
GDTR(Limit) ← SRC[0:15];
GDTR(Base) ← SRC[16:47]; FI; ELSE IF 64-bit
Operand Size (* In 64-Bit Mode *) THEN
GDTR(Limit) ← SRC[0:15]; GDTR(Base) ← SRC[16:79];
FI; FI; FI;
------------------
王翔
安全研究员
广州市腾御安信息科技有限公司
广州市天河区珠江新城华穗路406号保利克洛维二期中景A座1020-1024--
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