os: rework kernel architecture

Rework the code structure and architecture of the kernel by separating
platform-dependent and platform-independent code more cleanly. As of
this patchset, full feature parity has not been achieved. Nonetheless, a
sufficient subset of functionality has been ported to the new
architecture to demonstrate the feasibility of the new structure.

1 files changed, 111 insertions, 0 deletions

diff --git a/arch/x86_64/src/memory/kernel_mapper.cpp b/arch/x86_64/src/memory/kernel_mapper.cpp
new file mode 100644
index 0000000..4781d64
--- /dev/null
+++ b/arch/x86_64/src/memory/kernel_mapper.cpp
@@ -0,0 +1,111 @@
+#include "x86_64/memory/kernel_mapper.hpp"
+
+#include "kapi/cio.hpp"
+#include "kapi/memory.hpp"
+#include "kapi/system.hpp"
+
+#include "x86_64/boot/ld.hpp"
+
+#include <elf/format.hpp>
+#include <elf/section_header.hpp>
+#include <multiboot2/information.hpp>
+
+#include <algorithm>
+#include <array>
+#include <bit>
+#include <cstdint>
+#include <ranges>
+#include <string_view>
+#include <utility>
+
+namespace teachos::memory::x86_64
+{
+
+  namespace
+  {
+    using namespace std::string_view_literals;
+
+    constexpr auto static ignored_section_prefixes = std::array{
+      ".boot_"sv,
+    };
+
+    constexpr auto static user_accessible_prefixes = std::array{
+      ".user"sv,
+      ".stl"sv,
+    };
+
+  }  // namespace
+
+  kernel_mapper::kernel_mapper(multiboot2::information_view const * mbi)
+      : m_mbi{std::move(mbi)}
+      , m_kernel_load_base{std::bit_cast<std::uintptr_t>(&boot::x86_64::TEACHOS_VMA)}
+  {}
+
+  auto kernel_mapper::remap_kernel(page_mapper & mapper) -> void
+  {
+    auto elf_information = m_mbi->maybe_elf_symbols<elf::format::elf64>();
+    if (!elf_information)
+    {
+      system::panic("[x86_64:MEM] ELF section information is not available.");
+    }
+
+    auto sections = *elf_information;
+    auto allocated_sections =
+        std::views::all(sections) | std::views::filter(&elf::section_header<elf::format::elf64>::allocated) |
+        std::views::filter([&](auto const & section) -> auto {
+          auto name = sections.name(section);
+          return !std::ranges::any_of(ignored_section_prefixes,
+                                      [&](auto const & prefix) -> auto { return name.starts_with(prefix); });
+        });
+
+    if (allocated_sections.empty())
+    {
+      system::panic("[x86_64:MEM] No allocated ELF sections were found.");
+    }
+
+    std::ranges::for_each(allocated_sections,
+                          [&](auto const & section) -> auto { map_section(section, sections.name(section), mapper); });
+  }
+
+  auto kernel_mapper::map_section(section_header_type const & section, std::string_view name, page_mapper & mapper)
+      -> void
+  {
+    cio::print("[x86_64:MEM] mapping ");
+    cio::println(name);
+
+    auto number_of_pages = (section.size + (PLATFORM_PAGE_SIZE - 1)) / PLATFORM_PAGE_SIZE;
+
+    auto linear_start_address = linear_address{section.virtual_load_address};
+    auto physical_start_address = physical_address{section.virtual_load_address & ~m_kernel_load_base};
+
+    auto first_page = page::containing(linear_start_address);
+    auto first_frame = frame::containing(physical_start_address);
+
+    auto page_flags = page_mapper::flags::empty;
+
+    if (section.writable())
+    {
+      page_flags |= page_mapper::flags::writable;
+    }
+
+    if (section.executable())
+    {
+      page_flags |= page_mapper::flags::executable;
+    }
+
+    auto is_prefix_of_name = [=](auto prefix) -> bool {
+      return name.starts_with(prefix);
+    };
+
+    if (!std::ranges::any_of(user_accessible_prefixes, is_prefix_of_name))
+    {
+      page_flags |= page_mapper::flags::supervisor_only;
+    }
+
+    for (auto i = 0uz; i < number_of_pages; ++i)
+    {
+      mapper.map(first_page + i, first_frame + i, page_flags);
+    }
+  }
+
+}  // namespace teachos::memory::x86_64
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