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;
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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