Bananymous/banan-os
1
1
Fork 1
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Kernel: 64 bit MMU now properly identity maps kernel

Browse Source
This commit is contained in:
Bananymous
2023-05-05 14:18:18 +03:00
parent 3c5d3eb8ad
commit e7a170c89f
2 changed files with 19 additions and 33 deletions
Download Patch File Download Diff File Expand all files Collapse all files

34
kernel/arch/x86_64/MMU.cpp
View File

@@ -44,30 +44,12 @@ namespace Kernel
void MMU::initialize_kernel()
{
// FIXME: We should just identity map until g_kernel_end
ASSERT((uintptr_t)g_kernel_end <= 6 * (1 << 20));
// Identity map from 0 -> 6 MiB
m_highest_paging_struct = allocate_page_aligned_page();
uint64_t* pdpt = allocate_page_aligned_page();
m_highest_paging_struct[0] = (uint64_t)pdpt | Flags::ReadWrite | Flags::Present;
memset(m_highest_paging_struct, 0, PAGE_SIZE);
uint64_t* pd = allocate_page_aligned_page();
pdpt[0] = (uint64_t)pd | Flags::ReadWrite | Flags::Present;
for (uint32_t i = 0; i < 3; i++)
{
uint64_t* pt = allocate_page_aligned_page();
for (uint64_t j = 0; j < 512; j++)
pt[j] = (i << 21) | (j << 12) | Flags::ReadWrite | Flags::Present;
pd[i] = (uint64_t)pt | Flags::ReadWrite | Flags::Present;
}
// Unmap 0 -> 4 KiB
uint64_t* pt1 = (uint64_t*)(pd[0] & PAGE_MASK);
pt1[0] = 0;
// Identity map 4 KiB -> kernel end. We don't map the first page since nullptr derefs should
// page fault. Also there isn't anything useful in that memory.
identity_map_range(PAGE_SIZE, (uintptr_t)g_kernel_end, Flags::ReadWrite | Flags::Present);
}
MMU::MMU()
@@ -150,13 +132,13 @@ namespace Kernel
asm volatile("movq %0, %%cr3" :: "r"(m_highest_paging_struct));
}
void MMU::identity_map_page(paddr_t address, uint8_t flags)
void MMU::identity_map_page(paddr_t address, flags_t flags)
{
address &= PAGE_MASK;
map_page_at(address, address, flags);
}
void MMU::identity_map_range(paddr_t address, ptrdiff_t size, uint8_t flags)
void MMU::identity_map_range(paddr_t address, size_t size, flags_t flags)
{
paddr_t s_page = address & PAGE_MASK;
paddr_t e_page = (address + size - 1) & PAGE_MASK;
@@ -201,7 +183,7 @@ namespace Kernel
pml4[pml4e] = 0;
}
void MMU::unmap_range(vaddr_t address, ptrdiff_t size)
void MMU::unmap_range(vaddr_t address, size_t size)
{
vaddr_t s_page = address & PAGE_MASK;
vaddr_t e_page = (address + size - 1) & PAGE_MASK;
@@ -209,7 +191,7 @@ namespace Kernel
unmap_page(page);
}
void MMU::map_page_at(paddr_t paddr, vaddr_t vaddr, uint8_t flags)
void MMU::map_page_at(paddr_t paddr, vaddr_t vaddr, flags_t flags)
{
ASSERT((paddr >> 48) == 0);
ASSERT((vaddr >> 48) == 0);