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#include "kapi/memory.hpp"
#include "kapi/boot.hpp"
#include "kapi/cio.hpp"
#include "kapi/system.hpp"
#include "x86_64/boot/boot.hpp"
#include "x86_64/boot/ld.hpp"
#include "x86_64/cpu/registers.hpp"
#include "x86_64/memory/buffered_allocator.hpp"
#include "x86_64/memory/kernel_mapper.hpp"
#include "x86_64/memory/mmu.hpp"
#include "x86_64/memory/page_table.hpp"
#include "x86_64/memory/page_utilities.hpp"
#include "x86_64/memory/paging_root.hpp"
#include "x86_64/memory/recursive_page_mapper.hpp"
#include "x86_64/memory/region_allocator.hpp"
#include "x86_64/memory/scoped_mapping.hpp"
#include <multiboot2/information.hpp>
#include <atomic>
#include <bit>
#include <memory>
#include <span>
namespace teachos::memory
{
namespace
{
// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
auto constinit allocator = static_cast<frame_allocator *>(nullptr);
// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
auto constinit mapper = static_cast<page_mapper *>(nullptr);
constexpr auto static unused_page_address = linear_address{0x0000'7fff'cafe'faceuz};
constexpr auto static recursive_page_map_index = x86_64::page_table::entry_count - 2;
//! Instantiate a basic, memory region based, early frame allocator for remapping.
auto create_early_frame_allocator()
{
auto memory_map = boot::bootstrap_information.mbi->maybe_memory_map();
if (!memory_map)
{
system::panic("[x86_64] Failed to create early allocator, no memory map available.");
}
auto const & mbi = boot::bootstrap_information.mbi;
auto mbi_span = std::span{std::bit_cast<std::byte *>(mbi), mbi->size_bytes()};
auto image_span = std::span{&boot::x86_64::_start_physical, &boot::x86_64::_end_physical};
return x86_64::region_allocator{
{
.image_range = std::make_pair(physical_address{&image_span.front()}, physical_address{&image_span.back()}),
.mbi_range = std::make_pair(physical_address{&mbi_span.front()}, physical_address{&mbi_span.back()}),
.memory_map = *memory_map,
}
};
}
//! Enable additional CPU protection features, required during later stages of the kernel.
auto enable_cpu_protections() -> void
{
cpu::x86_64::cr0::set(cpu::x86_64::cr0::flags::write_protect);
cpu::x86_64::i32_efer::set(cpu::x86_64::i32_efer::flags::execute_disable_bit_enable);
}
//! Inject, or graft, a faux recursive PML4 into the active page mapping structure.
auto inject_faux_pml4(frame_allocator & allocator)
{
using namespace x86_64;
using entry_flags = page_table::entry::flags;
auto page = page::containing(unused_page_address);
auto temporary_mapper = scoped_mapping{page};
auto new_pml4_frame = allocator.allocate();
auto pml4 = std::construct_at(temporary_mapper.map_as<page_table>(*new_pml4_frame, entry_flags::writable));
(*pml4)[recursive_page_map_index].frame(new_pml4_frame.value(), entry_flags::present | entry_flags::writable);
auto pml4_index = pml_index<4>(page);
auto & old_pml4 = paging_root::get();
auto pml4_entry = old_pml4[pml4_index];
auto pml3_index = pml_index<3>(page);
auto old_pml3 = old_pml4.next(pml4_index);
auto pml3_entry = (**old_pml3)[pml3_index];
auto pml2_index = pml_index<2>(page);
auto old_pml2 = (**old_pml3).next(pml3_index);
auto pml2_entry = (**old_pml2)[pml2_index];
auto pml1_index = pml_index<1>(page);
auto old_pml1 = (**old_pml2).next(pml2_index);
auto pml1_entry = (**old_pml1)[pml1_index];
paging_root::get()[recursive_page_map_index].frame(new_pml4_frame.value(),
entry_flags::present | entry_flags::writable);
tlb_flush_all();
auto & new_pml4 = paging_root::get();
new_pml4[pml4_index] = pml4_entry;
auto new_pml3 = new_pml4.next(pml4_index);
(**new_pml3)[pml3_index] = pml3_entry;
auto new_pml2 = (**new_pml3).next(pml3_index);
(**new_pml2)[pml2_index] = pml2_entry;
auto new_pml1 = (**new_pml2).next(pml2_index);
(**new_pml1)[pml1_index] = pml1_entry;
return *new_pml4_frame;
}
auto remap_kernel() -> void
{
auto kernel_mapper = x86_64::kernel_mapper{boot::bootstrap_information.mbi};
kernel_mapper.remap_kernel();
}
auto remap_vga_text_mode_buffer(page_mapper & mapper) -> void
{
constexpr auto vga_base = std::uintptr_t{0xb8000};
auto vga_physical_start = physical_address{vga_base};
auto vga_virtual_start = linear_address{vga_base + std::bit_cast<std::uintptr_t>(&boot::x86_64::TEACHOS_VMA)};
auto page = page::containing(vga_virtual_start);
auto frame = frame::containing(vga_physical_start);
mapper.map(page, frame, page_mapper::flags::writable);
}
auto remap_multiboot_information(page_mapper & mapper) -> void
{
auto mbi_base = std::bit_cast<std::uintptr_t>(boot::bootstrap_information.mbi);
auto mbi_size = boot::bootstrap_information.mbi->size_bytes();
auto mbi_physical_start = physical_address{mbi_base};
auto mbi_virtual_start = linear_address{mbi_base + std::bit_cast<std::uintptr_t>(&boot::x86_64::TEACHOS_VMA)};
auto mbi_block_count = (mbi_size + PLATFORM_FRAME_SIZE - 1) / PLATFORM_FRAME_SIZE;
for (auto i = 0uz; i < mbi_block_count; ++i)
{
auto page = page::containing(mbi_virtual_start) + 1;
auto frame = frame::containing(mbi_physical_start) + 1;
mapper.map(page, frame, page_mapper::flags::empty);
}
boot::bootstrap_information.mbi = std::bit_cast<multiboot2::information_view const *>(mbi_virtual_start.raw());
}
} // namespace
auto active_frame_allocator() -> frame_allocator &
{
if (!allocator)
{
system::panic("[x86_64] The frame allocator has not been set yet.");
}
return *allocator;
}
auto active_page_mapper() -> page_mapper &
{
if (!mapper)
{
system::panic("[x86_64] The page mapper has not been set you.");
}
return *mapper;
}
auto init() -> void
{
auto static constinit is_initialized = std::atomic_flag{};
if (is_initialized.test_and_set())
{
system::panic("[x86_64] Memory management has already been initialized.");
}
cio::println("[x86_64:MEM] Enabling additional CPU protection features.");
enable_cpu_protections();
auto early_allocator = create_early_frame_allocator();
auto allocation_buffer = x86_64::buffered_allocator<4>{&early_allocator};
allocator = &allocation_buffer;
auto recursive_mapper = x86_64::recursive_page_mapper{allocation_buffer};
mapper = &recursive_mapper;
auto new_pml4_frame = inject_faux_pml4(allocation_buffer);
cio::println("[x86_64:MEM] Preparing new paging hierarchy.");
remap_kernel();
remap_vga_text_mode_buffer(recursive_mapper);
remap_multiboot_information(recursive_mapper);
cio::println("[x86_64:MEM] Switching to new paging hierarchy.");
auto cr3 = cpu::x86_64::cr3::read();
cr3.address(new_pml4_frame.start_address());
cpu::x86_64::cr3::write(cr3);
mapper = nullptr;
allocator = nullptr;
}
} // namespace teachos::memory
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