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Kernel: Keep fast page always reserved

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There was a bug where 32 bit target's reserve_free_page was allocating
the fast page address
This commit is contained in:
Bananymous
2026-04-04 22:27:00 +03:00
parent e239d9ca55
commit 664c824bc0
2 changed files with 12 additions and 2 deletions
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7
kernel/arch/i686/PageTable.cpp
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@@ -198,6 +198,7 @@ namespace Kernel
{
constexpr uint64_t pdpte = (fast_page() >> 30) & 0x1FF;
constexpr uint64_t pde = (fast_page() >> 21) & 0x1FF;
constexpr uint64_t pte = (fast_page() >> 12) & 0x1FF;
const uint64_t* pdpt = P2V(m_highest_paging_struct);
ASSERT(pdpt[pdpte] & Flags::Present);
@@ -205,6 +206,10 @@ namespace Kernel
uint64_t* pd = P2V(pdpt[pdpte] & s_page_addr_mask);
ASSERT(!(pd[pde] & Flags::Present));
pd[pde] = V2P(allocate_zeroed_page_aligned_page()) | Flags::ReadWrite | Flags::Present;
uint64_t* pt = P2V(pd[pde] & s_page_addr_mask);
ASSERT(pt[pte] == 0);
pt[pte] = Flags::Reserved;
}
void PageTable::map_fast_page(paddr_t paddr)
@@ -244,7 +249,7 @@ namespace Kernel
uint64_t* pt = P2V(pd[pde] & s_page_addr_mask);
ASSERT(pt[pte] & Flags::Present);
pt[pte] = 0;
pt[pte] = Flags::Reserved;
asm volatile("invlpg (%0)" :: "r"(fast_page()) : "memory");
}