Interrupt Descriptor Table: Difference between revisions
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Glauxosdever (talk | contribs) Clear things up |
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The '''Interrupt Descriptor Table''' ('''IDT''') is specific to the IA-32 architecture. It is the [[Protected mode]] counterpart to the [[Real Mode]] Interrupt Vector Table ([[IVT]]) telling where the [[Interrupt Service Routines]] (ISR) are located. It is similar to the [[Global Descriptor Table]] in structure. |
The '''Interrupt Descriptor Table''' ('''IDT''') is specific to the IA-32 architecture. It is the [[Protected mode]] counterpart to the [[Real Mode]] Interrupt Vector Table ([[IVT]]) telling where the [[Interrupt Service Routines]] (ISR) are located (one per interrupt vector). It is similar to the [[Global Descriptor Table]] in structure. |
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The IDT entries are called gates. It can contain Interrupt Gates, Task Gates and Trap Gates. |
The IDT entries are called gates. It can contain Interrupt Gates, Task Gates and Trap Gates. |
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</source> |
</source> |
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The <tt>offset</tt> is a 32 bit value, split in two parts. |
The <tt>offset</tt> is a 32 bit value, split in two parts. It represents the address of the entry point of the ISR. |
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The <tt>selector</tt> is a 16 bit value and must point to a valid selector in your [[GDT]]. |
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</source> |
</source> |
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The <tt>offset</tt> is a 64 bit value, split in three parts. |
The <tt>offset</tt> is a 64 bit value, split in three parts. It represents the address of the entry point of the ISR. |
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The <tt>selector</tt> is a 16 bit value and must point to a valid selector in your [[GDT]]. |
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<pre> |
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</pre> |
</pre> |
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<tt>type_attr</tt> is specified here: |
The <tt>type_attr</tt> is specified here: |
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<pre> |
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==Loading/Storing== |
==Loading/Storing== |
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The IDT is loaded using the <tt>LIDT</tt> assembly instruction. It expects the |
The IDT is loaded using the <tt>LIDT</tt> assembly instruction. It expects the address of a IDT description structure: |
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Byte: |
Byte: |
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+---------------+---------------+---------------+---------------+ |
+---------------+---------------+---------------+---------------+ |
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The <tt>offset</tt> is the virtual address of the table itself. The <tt>size</tt> is the size of the table subtracted by 1. This structure can be stored to memory again with the <tt>SIDT</tt> instruction. |
The <tt>offset</tt> is the virtual address of the table itself. The <tt>size</tt> is the size of the table itself subtracted by 1. This structure can be stored to memory again with the <tt>SIDT</tt> instruction. |
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To define the structure, one would write: |
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<source lang="asm"> |
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idt_info: |
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dw idt_end - idt_start - 1 |
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dd idt_start |
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</source> |
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To load the IDT, one would write: |
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<source lang="asm"> |
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lidt [idt_info] |
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</source> |
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==IDT in IA-32e Mode (64-bit IDT)== |
==IDT in IA-32e Mode (64-bit IDT)== |
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