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Line 23: <tt>type_attr</tt> is specified here: Bit: 7 . 5 . 4 4 . . . 0 +----------+ +-------------+ \|Pr Priv\| S\| \| GateType \| +----------+ +-------------+ The bit fields of Flags are: * '''Pr:''': Present bit. This must be set to '''1''' for all valid gate descriptors. * '''Priv:''': Privilege, 2 bits. Contains the ring level, 0 = highest (kernel), 3 = lowest (user applications). * '''S''': System segment bit. '''GateType''' determines the type of gate. Line 65: Trap and Interrupt gates are similar, and their descriptors are structurally the same, they differ only in the "type" field. The difference is that for interrupt gates, interrupts are automatically disabled upon entry and reenabled upon IRET which restores the saved EFLAGS. Choosing type_attr values: (See [[Descriptors#type_attr]]) * P=1 (descriptor present, if you'll be using it) * S=0 (system segment) * DPL (if you're not using protection, set to 0, otherwise FIXME) * type 1110b=0xE (32-bit interrupt gate) Line 76 ⟶ 73: 0110b=0x6 (16-bit interrupt gate) ** 0111b=0x7 (16-bit trap gate) Here are some pre-cooked type_attr values people are likely to use (assuming DPL=0): Line 99 ⟶ 95: Choosing type_attr values: (See [[Descriptors#type_attr]]) * P=1 (descriptor present, if you'll be using it) * S=0 (system segment) * DPL (if you're not using protection, set to 0, otherwise FIXME) * type=0b0101=0x5 (task gate)

Interrupt Descriptor Table: Difference between revisions