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Kernel: 64 bit MMU now properly identity maps kernel

This commit is contained in:
Bananymous 2023-05-05 14:18:18 +03:00
parent 4e859bedbc
commit 0cb53efa01
2 changed files with 19 additions and 33 deletions
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34
kernel/arch/x86_64/MMU.cpp
View File

@ -44,30 +44,12 @@ namespace Kernel
void MMU::initialize_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(); m_highest_paging_struct = allocate_page_aligned_page();
memset(m_highest_paging_struct, 0, PAGE_SIZE);
uint64_t* pdpt = allocate_page_aligned_page(); // Identity map 4 KiB -> kernel end. We don't map the first page since nullptr derefs should
m_highest_paging_struct[0] = (uint64_t)pdpt | Flags::ReadWrite | Flags::Present; // 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);
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;
} }
MMU::MMU() MMU::MMU()
@ -150,13 +132,13 @@ namespace Kernel
asm volatile("movq %0, %%cr3" :: "r"(m_highest_paging_struct)); 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; address &= PAGE_MASK;
map_page_at(address, address, flags); 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 s_page = address & PAGE_MASK;
paddr_t e_page = (address + size - 1) & PAGE_MASK; paddr_t e_page = (address + size - 1) & PAGE_MASK;
@ -201,7 +183,7 @@ namespace Kernel
pml4[pml4e] = 0; 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 s_page = address & PAGE_MASK;
vaddr_t e_page = (address + size - 1) & PAGE_MASK; vaddr_t e_page = (address + size - 1) & PAGE_MASK;
@ -209,7 +191,7 @@ namespace Kernel
unmap_page(page); 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((paddr >> 48) == 0);
ASSERT((vaddr >> 48) == 0); ASSERT((vaddr >> 48) == 0);

16
kernel/include/kernel/Memory/MMU.h
View File

@ -8,7 +8,8 @@ namespace Kernel
class MMU class MMU
{ {
public: public:
enum Flags : uint8_t using flags_t = uint8_t;
enum Flags : flags_t
{ {
Present = 1, Present = 1,
ReadWrite = 2, ReadWrite = 2,
@ -22,15 +23,18 @@ namespace Kernel
MMU(); MMU();
~MMU(); ~MMU();
void identity_map_page(paddr_t, uint8_t); void identity_map_page(paddr_t, flags_t);
void identity_map_range(paddr_t, ptrdiff_t, uint8_t); void identity_map_range(paddr_t, size_t, flags_t);
void unmap_page(vaddr_t); void unmap_page(vaddr_t);
void unmap_range(vaddr_t, ptrdiff_t); void unmap_range(vaddr_t, size_t);
void map_page_at(paddr_t, vaddr_t, uint8_t); void map_page_at(paddr_t, vaddr_t, flags_t);
uint8_t get_page_flags(vaddr_t) const; flags_t get_page_flags(vaddr_t) const;
vaddr_t get_free_page() const;
vaddr_t get_free_contiguous_pages(uint32_t) const;
void load(); void load();