Bochs: Difference between revisions

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===fetch_raw_descriptor: LDTR.valid=0===

Many of you have said "but ... I do not have an LDT and i read it wasn't mandatory!?". You're right. And so is BOCHS. This message usually means that your program tried to load a selector with some garbage value, which happened to have the 3rd bit (Table Indicator) set. The CPU will try to look up the descriptor in the LDT, but there's no LDT registered! In most cases, the error comes from some mispairing of push and pop on the stack, which lead to a non-selector value to be loaded in a segment register.

Many of you have said "but ... I do not have an LDT and I read it wasn't mandatory!?". You're right. And so is BOCHS. This message usually means that your program tried to load a selector with some garbage value, which happened to have the 3rd bit (Table Indicator) set. The CPU will try to look up the descriptor in the LDT, but there's no LDT registered! In most cases, the error comes from some mispairing of push and pop on the stack, which lead to a non-selector value to be loaded in a segment register.

If you're still stuck, download the Bochs sources package and search for the message you received. Then, maybe you can add extra information to the message-printing code (like the faulty offset of a segfault, the segment limit, etc). But keep away from modifying Bochs' operations! Every time I suspected a bug in Bochs, I was just misunderstanding the Intel Manual...

@@ Line 31: / Line 31: @@
 ===fetch_raw_descriptor: LDTR.valid=0===
-Many of you have said "but ... I do not have an LDT and i read it wasn't mandatory!?". You're right. And so is BOCHS. This message usually means that your program tried to load a selector with some garbage value, which happened to have the 3rd bit (Table Indicator) set. The CPU will try to look up the descriptor in the LDT, but there's no LDT registered! In most cases, the error comes from some mispairing of push and pop on the stack, which lead to a non-selector value to be loaded in a segment register.
+Many of you have said "but ... I do not have an LDT and I read it wasn't mandatory!?". You're right. And so is BOCHS. This message usually means that your program tried to load a selector with some garbage value, which happened to have the 3rd bit (Table Indicator) set. The CPU will try to look up the descriptor in the LDT, but there's no LDT registered! In most cases, the error comes from some mispairing of push and pop on the stack, which lead to a non-selector value to be loaded in a segment register.
 If you're still stuck, download the Bochs sources package and search for the message you received. Then, maybe you can add extra information to the message-printing code (like the faulty offset of a segfault, the segment limit, etc). But keep away from modifying Bochs' operations! Every time I suspected a bug in Bochs, I was just misunderstanding the Intel Manual...

Bochs: Difference between revisions

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