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gdt: Check that MAX is in range #365

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Mar 30, 2022
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gdt: Check that MAX is in range #365

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5 changes: 5 additions & 0 deletions src/structures/gdt.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -64,6 +64,9 @@ impl<const MAX: usize> GlobalDescriptorTable<MAX> {
/// Creates an empty GDT which can hold `MAX` number of [`Descriptor`]s.
#[inline]
pub const fn empty() -> Self {
// TODO: Replace with compiler error when feature(generic_const_exprs) is stable.
assert!(MAX > 0, "A GDT cannot have 0 entries");
assert!(MAX <= (1 << 13), "A GDT can only have at most 2^13 entries");
Self {
table: [0; MAX],
next_free: 1,
Expand Down Expand Up @@ -184,6 +187,8 @@ impl<const MAX: usize> GlobalDescriptorTable<MAX> {
use core::mem::size_of;
super::DescriptorTablePointer {
base: crate::VirtAddr::new(self.table.as_ptr() as u64),
// 0 < self.next_free <= MAX <= 2^13, so the limit calculation
// will not underflow or overflow.
limit: (self.next_free * size_of::<u64>() - 1) as u16,
}
}
Expand Down