x86_64/vga: rely less on magic state

10 files changed, 118 insertions, 37 deletions

diff --git a/.vscode/settings.json b/.vscode/settings.json
index dcf1d1a..4f3f047 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -24,9 +24,11 @@
     "cSpell.words": [
         "crtc",
         "efer",
+        "INTERPROCEDURAL",
         "invlpg",
         "kapi",
         "kstd",
+        "multiboot",
         "NOLINTNEXTLINE",
         "rdmsr",
         "rvalues",
diff --git a/arch/x86_64/CMakeLists.txt b/arch/x86_64/CMakeLists.txt
index 9c6d818..cf85b36 100644
--- a/arch/x86_64/CMakeLists.txt
+++ b/arch/x86_64/CMakeLists.txt
@@ -30,6 +30,30 @@ target_sources("x86_64" PRIVATE
     "src/vga/text.cpp"
 )
 
+target_sources("x86_64" PRIVATE
+    FILE_SET HEADERS
+    BASE_DIRS "include"
+    FILES
+    # Low-level bootstrap
+    "include/x86_64/boot/boot.hpp"
+    "include/x86_64/boot/ld.hpp"
+
+    # Low-level CPU access
+    "include/x86_64/cpu/registers.hpp"
+    "include/x86_64/cpu/impl/control_registers.hpp"
+    "include/x86_64/cpu/impl/model_specific_register.hpp"
+
+    # Low-level device I/O
+    "include/x86_64/device_io/port_io.hpp"
+
+    # Memory management
+    "include/x86_64/memory/mmu.hpp"
+    "include/x86_64/memory/region_allocator.hpp"
+
+    # VGA I/O
+    "include/x86_64/vga/text.hpp"
+)
+
 set(KERNEL_LINKER_SCRIPT
     "${CMAKE_CURRENT_SOURCE_DIR}/scripts/kernel.ld"
     PARENT_SCOPE
diff --git a/arch/x86_64/include/x86_64/boot/boot.hpp b/arch/x86_64/include/x86_64/boot/boot.hpp
index 3a3620d..6dcd2de 100644
--- a/arch/x86_64/include/x86_64/boot/boot.hpp
+++ b/arch/x86_64/include/x86_64/boot/boot.hpp
@@ -45,26 +45,22 @@
 /* clang-format on */
 #else
 
+#include "kapi/boot.hpp"  // IWYU pragma: export
+
 #include <multiboot2/information.hpp>
 
-#include <kstd/asm_ptr>
+#include <cstddef>
 
-namespace teachos::boot::x86_64
+namespace teachos::boot
 {
 
-  extern "C"
+  struct information
   {
-    /**
-     * @brief A pointer to the multiboot 2 information structure provided by the boot loader.
-     */
-    extern kstd::asm_ptr<multiboot2::information_view> multiboot_information_pointer;
-
-    /**
-     * @brief A pointer to the VGA text mode buffer.
-     */
-    extern kstd::asm_ptr<std::pair<char, std::byte>> vga_buffer_pointer;
-  }
-}  // namespace teachos::boot::x86_64
+    multiboot2::information_view const * mbi;
+    std::size_t vga_buffer_index;
+  };
+
+}  // namespace teachos::boot
 
 #endif
 
diff --git a/arch/x86_64/include/x86_64/boot/ld.hpp b/arch/x86_64/include/x86_64/boot/ld.hpp
index 104e6ee..9af3dc8 100644
--- a/arch/x86_64/include/x86_64/boot/ld.hpp
+++ b/arch/x86_64/include/x86_64/boot/ld.hpp
@@ -61,6 +61,15 @@ namespace teachos::boot::x86_64
      * To use this symbol for its intended purpose, the address of it shall be taken.
      */
     extern std::byte _end_virtual;
+
+    /**
+     * @brief The first byte of the kernel's virtual address space.
+     *
+     * @details
+     * This symbol is defined in the kernel linker script and marks beginning of the kernel virtual address space. To
+     * use this symbol for its intended purpose, the address of it shall be taken.
+     */
+    extern std::byte TEACHOS_VMA;
   }
 }  // namespace teachos::boot::x86_64
 
diff --git a/arch/x86_64/include/x86_64/vga/text.hpp b/arch/x86_64/include/x86_64/vga/text.hpp
index d8919bf..bb593e7 100644
--- a/arch/x86_64/include/x86_64/vga/text.hpp
+++ b/arch/x86_64/include/x86_64/vga/text.hpp
@@ -4,6 +4,7 @@
 #include "kapi/cio.hpp"
 
 #include <cstdint>
+#include <span>
 #include <string_view>
 
 namespace teachos::vga::x86_64::text
@@ -100,6 +101,8 @@ namespace teachos::vga::x86_64::text
 
   struct device final : teachos::cio::output_device
   {
+    device();
+
     /**
      * @brief Clear the VGA text mode buffer.
      *
@@ -134,6 +137,8 @@ namespace teachos::vga::x86_64::text
     }
 
   private:
+    using glyph = std::pair<char, std::byte>;
+
     /**
      * @brief Move the cursor to a new line, scrolling the buffer if necessary.
      */
@@ -150,6 +155,8 @@ namespace teachos::vga::x86_64::text
      */
     auto write(std::string_view code_points, attribute attribute) -> void;
 
+    auto write(char code_point, attribute attribute) -> void;
+
     /**
      * @brief Write a string of code points followed by a newline to the VGA text buffer.
      *
@@ -160,6 +167,10 @@ namespace teachos::vga::x86_64::text
      * @see vga::text::attribute
      */
     auto writeln(std::string_view code_points, attribute attribute) -> void;
+
+    std::span<glyph> static const buffer;
+
+    std::size_t m_position{};
   };
 
 }  // namespace teachos::vga::x86_64::text
diff --git a/arch/x86_64/src/boot/entry64.s b/arch/x86_64/src/boot/entry64.s
index c5df5db..636e4cd 100644
--- a/arch/x86_64/src/boot/entry64.s
+++ b/arch/x86_64/src/boot/entry64.s
@@ -1,3 +1,16 @@
+.section .bss, "aw", @nobits
+
+//! A structure containing information gathered during the bootstrap process.
+//! Expected layout (as described by teachos::boot::information):
+//!
+//! struct
+//! {
+//!   multiboot2::information_view const * mbi;
+//!   std::size_t vga_buffer_index;
+//! }
+.global bootstrap_information
+bootstrap_information: .skip 16
+
 .section .boot_text, "ax", @progbits
 .code64
 
@@ -10,6 +23,12 @@ _entry64:
     mov %rax, %fs
     mov %rax, %gs
 
+    mov multiboot_information_pointer, %rax
+    mov vga_buffer_pointer, %rdx
+    sub $0xb8000, %rdx
+    mov %rax, (bootstrap_information)
+    mov %rdx, (bootstrap_information + 8)
+
     call invoke_global_constructors
     
     xor %rax, %rax
diff --git a/arch/x86_64/src/kapi/memory.cpp b/arch/x86_64/src/kapi/memory.cpp
index 5142a2a..3848fb8 100644
--- a/arch/x86_64/src/kapi/memory.cpp
+++ b/arch/x86_64/src/kapi/memory.cpp
@@ -24,7 +24,7 @@ namespace teachos::memory
 
     auto create_memory_information() -> x86_64::region_allocator::memory_information
     {
-      auto const & mbi = boot::x86_64::multiboot_information_pointer.get();
+      auto const & mbi = boot::bootstrap_information.mbi;
 
       return {.image_range = std::make_pair(physical_address{&boot::x86_64::_start_physical},
                                             physical_address{&boot::x86_64::_end_physical}),
@@ -35,7 +35,7 @@ namespace teachos::memory
 
     auto create_early_frame_allocator()
     {
-      auto memory_map = boot::x86_64::multiboot_information_pointer->maybe_memory_map();
+      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.");
diff --git a/arch/x86_64/src/vga/text.cpp b/arch/x86_64/src/vga/text.cpp
index 6ecffa3..8b7f01b 100644
--- a/arch/x86_64/src/vga/text.cpp
+++ b/arch/x86_64/src/vga/text.cpp
@@ -1,38 +1,41 @@
 #include "x86_64/vga/text.hpp"
 
+#include "kapi/boot.hpp"
+
 #include "x86_64/boot/boot.hpp"
+#include "x86_64/boot/ld.hpp"
 #include "x86_64/vga/crtc.hpp"
 
 #include <algorithm>
 #include <bit>
 #include <cstddef>
+#include <cstdint>
 #include <string_view>
 #include <utility>
 
 namespace teachos::vga::x86_64::text
 {
-  using boot::x86_64::vga_buffer_pointer;
-
   namespace
   {
-    // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
-    auto constinit buffer_offset = std::ptrdiff_t{};
-
+    constexpr auto BUFFER_BASE_ADDRESS = std::uintptr_t{0xb8000};
     constexpr auto DEFAULT_TEXT_BUFFER_WIDTH = 80U;
     constexpr auto DEFAULT_TEXT_BUFFER_HEIGHT = 25U;
     constexpr auto CURSOR_ENABLED_BIT = 5U;
-
-    auto write_char(char code_point, attribute attribute) -> void
-    {
-      vga_buffer_pointer[buffer_offset++] = std::pair{code_point, std::bit_cast<std::byte>(attribute)};
-    };
   }  // namespace
 
+  std::span<device::glyph> const device::buffer =
+      std::span{std::bit_cast<device::glyph *>(BUFFER_BASE_ADDRESS +
+                                               std::bit_cast<std::uintptr_t>(&teachos::boot::x86_64::TEACHOS_VMA)),
+                DEFAULT_TEXT_BUFFER_WIDTH * DEFAULT_TEXT_BUFFER_HEIGHT};
+
+  device::device()
+      : m_position{boot::bootstrap_information.vga_buffer_index}
+  {}
+
   auto device::clear(attribute attribute) -> void
   {
-    buffer_offset = 0;
-    std::ranges::fill_n(vga_buffer_pointer.get(), DEFAULT_TEXT_BUFFER_WIDTH * DEFAULT_TEXT_BUFFER_HEIGHT,
-                        std::pair{' ', std::bit_cast<std::byte>(attribute)});
+    m_position = 0;
+    std::ranges::fill(buffer, std::pair{' ', std::bit_cast<std::byte>(attribute)});
   }
 
   auto device::cursor(bool enabled) -> void
@@ -45,30 +48,35 @@ namespace teachos::vga::x86_64::text
 
   auto device::newline() -> void
   {
-    auto current_line = buffer_offset / DEFAULT_TEXT_BUFFER_WIDTH;
+    auto current_line = m_position / DEFAULT_TEXT_BUFFER_WIDTH;
     auto next_line = current_line + 1;
 
     if (std::cmp_greater_equal(next_line, DEFAULT_TEXT_BUFFER_HEIGHT))
     {
-      auto begin = vga_buffer_pointer + DEFAULT_TEXT_BUFFER_WIDTH;
-      auto end = vga_buffer_pointer + DEFAULT_TEXT_BUFFER_WIDTH * DEFAULT_TEXT_BUFFER_HEIGHT;
-      std::ranges::move(begin, end, vga_buffer_pointer.get());
-      buffer_offset = current_line * DEFAULT_TEXT_BUFFER_WIDTH;
+      auto begin = buffer.begin() + DEFAULT_TEXT_BUFFER_WIDTH;
+      auto end = buffer.begin() + DEFAULT_TEXT_BUFFER_WIDTH * DEFAULT_TEXT_BUFFER_HEIGHT;
+      std::ranges::move(begin, end, buffer.begin());
+      m_position = current_line * DEFAULT_TEXT_BUFFER_WIDTH;
     }
     else
     {
-      buffer_offset = next_line * DEFAULT_TEXT_BUFFER_WIDTH;
+      m_position = next_line * DEFAULT_TEXT_BUFFER_WIDTH;
     }
   }
 
   auto device::write(std::string_view code_points, attribute attribute) -> void
   {
-    std::ranges::for_each(code_points, [&](auto code_point) -> void { write_char(code_point, attribute); });
+    std::ranges::for_each(code_points, [&](auto code_point) -> void { write(code_point, attribute); });
   }
 
+  auto device::write(char code_point, attribute attribute) -> void
+  {
+    buffer[m_position++] = std::pair{code_point, std::bit_cast<std::byte>(attribute)};
+  };
+
   auto device::writeln(std::string_view code_points, attribute attribute) -> void
   {
-    std::ranges::for_each(code_points, [&](auto code_point) -> void { write_char(code_point, attribute); });
+    std::ranges::for_each(code_points, [&](auto code_point) -> void { write(code_point, attribute); });
     newline();
   }
 
diff --git a/kapi/CMakeLists.txt b/kapi/CMakeLists.txt
index 86b0fb6..553b9ba 100644
--- a/kapi/CMakeLists.txt
+++ b/kapi/CMakeLists.txt
@@ -5,6 +5,7 @@ target_sources("kapi" PUBLIC
     FILE_SET HEADERS
     BASE_DIRS "include"
     FILES
+    "include/kapi/boot.hpp"
     "include/kapi/cio.hpp"
     "include/kapi/memory.hpp"
     "include/kapi/system.hpp"
diff --git a/kapi/include/kapi/boot.hpp b/kapi/include/kapi/boot.hpp
new file mode 100644
index 0000000..013e180
--- /dev/null
+++ b/kapi/include/kapi/boot.hpp
@@ -0,0 +1,11 @@
+#ifndef TEACHOS_KAPI_BOOT_HPP
+#define TEACHOS_KAPI_BOOT_HPP
+
+namespace teachos::boot
+{
+  struct information;
+
+  extern "C" information const bootstrap_information;
+}  // namespace teachos::boot
+
+#endif