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cpu: Check for reserved zeros in interrupt descriptor

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This lets us make our gate type validity check more readable
This commit is contained in:
Amaan Cheval 2018-09-19 15:34:57 +05:30 committed by Fabian
parent aa789d4129
commit 8ba3de34c1
1 changed files with 8 additions and 3 deletions
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11
src/rust/cpu2/cpu.rs
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@ -354,11 +354,12 @@ impl InterruptDescriptor {
pub fn selector(&self) -> u16 { (self.raw >> 16 & 0xffff) as u16 }
pub fn access_byte(&self) -> u8 { (self.raw >> 40 & 0xff) as u8 }
pub fn dpl(&self) -> u8 { (self.access_byte() >> 5 & 3) as u8 }
pub fn gate_type(&self) -> u8 { self.access_byte() & 31 }
pub fn gate_type(&self) -> u8 { self.access_byte() & 7 }
pub fn is_32(&self) -> bool { self.access_byte() & 8 == 8 }
pub fn is_present(&self) -> bool { self.access_byte() & 0x80 == 0x80 }
const TASK_GATE: u8 = 0b101;
const INTERRUPT_GATE: u8 = 0b110;
const TRAP_GATE: u8 = 0b111;
}
@ -430,7 +431,12 @@ pub unsafe fn call_interrupt_vector(
return;
}
if gate_type & !1 & !8 != 6 {
let is_trap = gate_type == InterruptDescriptor::TRAP_GATE;
let is_valid_type = is_trap || gate_type == InterruptDescriptor::INTERRUPT_GATE;
let reserved_zeroes_are_valid =
descriptor.raw >> 36 & 7 == 0 && descriptor.access_byte() & 16 == 0;
if !is_valid_type || !reserved_zeroes_are_valid {
// invalid gate_type
dbg_trace();
dbg_log!("invalid gate_type: 0b{:b}", gate_type);
@ -443,7 +449,6 @@ pub unsafe fn call_interrupt_vector(
panic!("Unimplemented: #GP handler");
}
let is_trap = gate_type & 7 == InterruptDescriptor::TRAP_GATE;
let is_16 = !descriptor.is_32();
let cs_segment_descriptor = match return_on_pagefault!(lookup_segment_selector(selector)) {