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Kernel: Add fast page to page table

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Add "fast page" to KERNEL_OFFSET. This is always present in page
tables and only requires changing the page table entry to map. This
requires no interrupts since it should only be for very operations
like memcpy.

I used to map all temporary mappings to vaddr 0, but this is much
better. C++ standard always says that nullptr access is undefined
and this gets rid of it.

Fixed some bugs I found along the way
This commit is contained in:
Bananymous
2023-10-30 19:02:09 +02:00
parent 6e676ee8c5
commit 42772611ce
9 changed files with 193 additions and 134 deletions
Download Patch File Download Diff File Expand all files Collapse all files

96
kernel/arch/x86_64/PageTable.cpp
View File

@@ -1,6 +1,6 @@
#include <BAN/Errors.h>
#include <kernel/Arch.h>
#include <kernel/CPUID.h>
#include <kernel/InterruptController.h>
#include <kernel/LockGuard.h>
#include <kernel/Memory/kmalloc.h>
#include <kernel/Memory/PageTable.h>
@@ -143,6 +143,8 @@ namespace Kernel
uint64_t* pml4 = (uint64_t*)P2V(m_highest_paging_struct);
pml4[511] = s_global_pml4e;
prepare_fast_page();
// Map (phys_kernel_start -> phys_kernel_end) to (virt_kernel_start -> virt_kernel_end)
ASSERT((vaddr_t)g_kernel_start % PAGE_SIZE == 0);
map_range_at(
@@ -185,6 +187,76 @@ namespace Kernel
g_multiboot2_info = (multiboot2_info_t*)(multiboot2_vaddr + ((vaddr_t)g_multiboot2_info % PAGE_SIZE));
}
void PageTable::prepare_fast_page()
{
constexpr vaddr_t uc_vaddr = uncanonicalize(fast_page());
constexpr uint64_t pml4e = (uc_vaddr >> 39) & 0x1FF;
constexpr uint64_t pdpte = (uc_vaddr >> 30) & 0x1FF;
constexpr uint64_t pde = (uc_vaddr >> 21) & 0x1FF;
constexpr uint64_t pte = (uc_vaddr >> 12) & 0x1FF;
uint64_t* pml4 = (uint64_t*)P2V(m_highest_paging_struct);
ASSERT(!(pml4[pml4e] & Flags::Present));
pml4[pml4e] = V2P(allocate_zeroed_page_aligned_page()) | Flags::ReadWrite | Flags::Present;
uint64_t* pdpt = (uint64_t*)P2V(pml4[pml4e] & PAGE_ADDR_MASK);
ASSERT(!(pdpt[pdpte] & Flags::Present));
pdpt[pdpte] = V2P(allocate_zeroed_page_aligned_page()) | Flags::ReadWrite | Flags::Present;
uint64_t* pd = (uint64_t*)P2V(pdpt[pdpte] & PAGE_ADDR_MASK);
ASSERT(!(pd[pde] & Flags::Present));
pd[pde] = V2P(allocate_zeroed_page_aligned_page()) | Flags::ReadWrite | Flags::Present;
uint64_t* pt = (uint64_t*)P2V(pd[pde] & PAGE_ADDR_MASK);
ASSERT(!(pt[pte] & Flags::Present));
pt[pte] = V2P(allocate_zeroed_page_aligned_page());
}
void PageTable::map_fast_page(paddr_t paddr)
{
ASSERT(s_kernel);
ASSERT_GE(paddr, 0);
ASSERT(!interrupts_enabled());
constexpr vaddr_t uc_vaddr = uncanonicalize(fast_page());
constexpr uint64_t pml4e = (uc_vaddr >> 39) & 0x1FF;
constexpr uint64_t pdpte = (uc_vaddr >> 30) & 0x1FF;
constexpr uint64_t pde = (uc_vaddr >> 21) & 0x1FF;
constexpr uint64_t pte = (uc_vaddr >> 12) & 0x1FF;
uint64_t* pml4 = (uint64_t*)P2V(s_kernel->m_highest_paging_struct);
uint64_t* pdpt = (uint64_t*)P2V(pml4[pml4e] & PAGE_ADDR_MASK);
uint64_t* pd = (uint64_t*)P2V(pdpt[pdpte] & PAGE_ADDR_MASK);
uint64_t* pt = (uint64_t*)P2V(pd[pde] & PAGE_ADDR_MASK);
ASSERT(!(pt[pte] & Flags::Present));
pt[pte] = paddr | Flags::ReadWrite | Flags::Present;
invalidate(fast_page());
}
void PageTable::unmap_fast_page()
{
ASSERT(s_kernel);
ASSERT(!interrupts_enabled());
constexpr vaddr_t uc_vaddr = uncanonicalize(fast_page());
constexpr uint64_t pml4e = (uc_vaddr >> 39) & 0x1FF;
constexpr uint64_t pdpte = (uc_vaddr >> 30) & 0x1FF;
constexpr uint64_t pde = (uc_vaddr >> 21) & 0x1FF;
constexpr uint64_t pte = (uc_vaddr >> 12) & 0x1FF;
uint64_t* pml4 = (uint64_t*)P2V(s_kernel->m_highest_paging_struct);
uint64_t* pdpt = (uint64_t*)P2V(pml4[pml4e] & PAGE_ADDR_MASK);
uint64_t* pd = (uint64_t*)P2V(pdpt[pdpte] & PAGE_ADDR_MASK);
uint64_t* pt = (uint64_t*)P2V(pd[pde] & PAGE_ADDR_MASK);
ASSERT(pt[pte] & Flags::Present);
pt[pte] = 0;
invalidate(fast_page());
}
BAN::ErrorOr<PageTable*> PageTable::create_userspace()
{
LockGuard _(s_kernel->m_lock);
@@ -246,13 +318,16 @@ namespace Kernel
void PageTable::invalidate(vaddr_t vaddr)
{
ASSERT(vaddr % PAGE_SIZE == 0);
if (this == s_current)
asm volatile("invlpg (%0)" :: "r"(vaddr) : "memory");
asm volatile("invlpg (%0)" :: "r"(vaddr) : "memory");
}
void PageTable::unmap_page(vaddr_t vaddr)
{
if (vaddr && (vaddr >= KERNEL_OFFSET) != (this == s_kernel))
ASSERT(vaddr);
ASSERT(vaddr != fast_page());
if (vaddr >= KERNEL_OFFSET)
ASSERT_GE(vaddr, (vaddr_t)g_kernel_start);
if ((vaddr >= KERNEL_OFFSET) != (this == s_kernel))
Kernel::panic("unmapping {8H}, kernel: {}", vaddr, this == s_kernel);
ASSERT(is_canonical(vaddr));
@@ -294,7 +369,11 @@ namespace Kernel
void PageTable::map_page_at(paddr_t paddr, vaddr_t vaddr, flags_t flags)
{
if (vaddr && (vaddr >= KERNEL_OFFSET) != (this == s_kernel))
ASSERT(vaddr);
ASSERT(vaddr != fast_page());
if (vaddr >= KERNEL_OFFSET)
ASSERT_GE(vaddr, (vaddr_t)g_kernel_start);
if ((vaddr >= KERNEL_OFFSET) != (this == s_kernel))
Kernel::panic("mapping {8H} to {8H}, kernel: {}", paddr, vaddr, this == s_kernel);
ASSERT(is_canonical(vaddr));
@@ -361,12 +440,11 @@ namespace Kernel
{
ASSERT(is_canonical(vaddr));
ASSERT(vaddr);
ASSERT(paddr % PAGE_SIZE == 0);
ASSERT(vaddr % PAGE_SIZE == 0);
size_t first_page = vaddr / PAGE_SIZE;
size_t last_page = (vaddr + size - 1) / PAGE_SIZE;
size_t page_count = last_page - first_page + 1;
size_t page_count = range_page_count(vaddr, size);
LockGuard _(m_lock);
for (size_t page = 0; page < page_count; page++)
@@ -527,6 +605,8 @@ namespace Kernel
vaddr_t PageTable::reserve_free_contiguous_pages(size_t page_count, vaddr_t first_address, vaddr_t last_address)
{
if (first_address >= KERNEL_OFFSET && first_address < (vaddr_t)g_kernel_start)
first_address = (vaddr_t)g_kernel_start;
if (size_t rem = first_address % PAGE_SIZE)
first_address += PAGE_SIZE - rem;
if (size_t rem = last_address % PAGE_SIZE)