continue implementing paging

9 files changed, 113 insertions, 136 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f5cc7ea..3586669 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -101,13 +101,20 @@ add_library("_video" OBJECT)
 add_library("teachos::video" ALIAS "_video")
 
 #[============================================================================[
-# The memory Library
+# THE Memory Library
 #]============================================================================]
 
 add_library("_memory" OBJECT)
 add_library("teachos::memory" ALIAS "_memory")
 
 #[============================================================================[
+# The Exception handling Library
+#]============================================================================]
+
+add_library("_exception" OBJECT)
+add_library("teachos::exception" ALIAS "_exception")
+
+#[============================================================================[
 # The Kernel
 #]============================================================================]
 
@@ -120,6 +127,7 @@ target_link_libraries("_kernel" PRIVATE
   "teachos::boot"
   "teachos::video"
   "teachos::memory"
+  "teachos::exception"
 )
 
 #[============================================================================[
diff --git a/arch/x86_64/CMakeLists.txt b/arch/x86_64/CMakeLists.txt
index 25f8634..603393c 100644
--- a/arch/x86_64/CMakeLists.txt
+++ b/arch/x86_64/CMakeLists.txt
@@ -47,6 +47,14 @@ target_sources("_memory" PRIVATE
 )
 
 #[============================================================================[
+# The Exception handling Library
+#]============================================================================]
+
+target_sources("_exception" PRIVATE
+  "src/exception_handling/assert.cpp"
+)
+
+#[============================================================================[
 # The Bootable ISO Image
 #]============================================================================]
 
diff --git a/arch/x86_64/include/arch/exception_handling/assert.hpp b/arch/x86_64/include/arch/exception_handling/assert.hpp
new file mode 100644
index 0000000..eba43ac
--- /dev/null
+++ b/arch/x86_64/include/arch/exception_handling/assert.hpp
@@ -0,0 +1,11 @@
+namespace teachos::arch::exception_handling
+{
+  /**
+   * @brief assert a condition to be true, if not do not continue
+   * execution of the code and print message to screen
+   *
+   * @param condition
+   * @param message
+   */
+  auto assert(bool condition, char const * message) -> void;
+}  // namespace teachos::arch::exception_handling
\ No newline at end of file
diff --git a/arch/x86_64/include/arch/memory/frame_allocator.hpp b/arch/x86_64/include/arch/memory/frame_allocator.hpp
index ab93231..69c108c 100644
--- a/arch/x86_64/include/arch/memory/frame_allocator.hpp
+++ b/arch/x86_64/include/arch/memory/frame_allocator.hpp
@@ -32,6 +32,13 @@ namespace teachos::arch::memory
     static auto containing_address(std::size_t address) -> physical_frame;
 
     /**
+     * @brief  TODO
+     *
+     * @return uint64_t
+     */
+    auto start_address() const -> uint64_t;
+
+    /**
      * @brief Defaulted equals operator.
      */
     constexpr auto operator==(const physical_frame & other) const -> bool = default;
diff --git a/arch/x86_64/include/arch/memory/paging.hpp b/arch/x86_64/include/arch/memory/paging.hpp
index a5408e1..1870c28 100644
--- a/arch/x86_64/include/arch/memory/paging.hpp
+++ b/arch/x86_64/include/arch/memory/paging.hpp
@@ -43,72 +43,6 @@ namespace teachos::arch::memory
     auto set_unused() -> void;
 
     /**
-     * @brief Whether the current page is in memory and therefore present or not. Read from bit index 0.
-     *
-     * @return Current page is in memory.
-     */
-    auto present() const -> bool;
-
-    /**
-     * @brief Whether it is possible to write to the current page or not. Read from bit index 1.
-     *
-     * @return Current page can be written too.
-     */
-    auto writable() const -> bool;
-
-    /**
-     * @brief Whether the current page can be accessed in user mode, or only in kernel mode code. Read from bit index 2.
-     *
-     * @return Current page can be accessed in user mode.
-     */
-    auto user_accessible() const -> bool;
-
-    /**
-     * @brief Whether any write to the current page go directly to memory instead of the cache or not. Read from bit
-     * index 3.
-     *
-     * @return Writes to the current page go directly to memory.
-     */
-    auto write_through_caching() const -> bool;
-
-    /**
-     * @brief Whether the current page uses caching or not. Read from bit index 4.
-     *
-     * @return Current page does not use caching.
-     */
-    auto disabled_caching() const -> bool;
-
-    /**
-     * @brief Whether the current page is currently being used or not. Read from bit index 5.
-     *
-     * @return Current page is currently being used.
-     */
-    auto is_accessing() const -> bool;
-
-    /**
-     * @brief Whether the current page has been writen too or not. Read from bit index 6.
-     *
-     * @return Current page has been writen too.
-     */
-    auto is_diry() const -> bool;
-
-    /**
-     * @brief Whether the current page is huge or not (2 MiB page size in P2 page table and 1 GiB in P3 page table,
-     * instead of 4 KiB). Has to be false for P1 and P4 page tables. Read from bit index 7.
-     *
-     * @return Current page is huge
-     */
-    auto is_huge_page() const -> bool;
-
-    /**
-     * @brief Whether the current page is not flushed from caches on address space switches or not (PGE bit of CR4
-     * register has to be set). Read from bit index 8.
-     *
-     * @return Current page is not flushed from caches on address space switches.
-     */
-    auto is_global() const -> bool;
-
-    /**
      * @brief Whether the current page is forbidden from executing code or not (NXE bit in the EFER register has to be
      * set). Read from bit index 63.
      *
@@ -124,6 +58,22 @@ namespace teachos::arch::memory
      */
     auto calculate_pointed_to_frame() const -> std::optional<physical_frame>;
 
+    /**
+     * @brief TODO
+     *
+     * @param frame
+     */
+    auto set(physical_frame frame) -> void;
+
+    /**
+     * @brief TODO
+     *
+     * @param b
+     * @return true
+     * @return false
+     */
+    auto contains_flags(std::bitset<64U> b) const -> bool;
+
   private:
     /**
      * @brief Extracts the physical address from the underlying bitset read from bit index 12 - 51. Is a 52 bit page
@@ -134,17 +84,18 @@ namespace teachos::arch::memory
      */
     auto calculate_physical_address() const -> std::size_t;
 
-    /**
-     * @brief Checks the underlying std::bitset if the bit at the specific index is set, meaning a value of 1
-     *
-     * @param index Specific index we want to check at
-     * @return Bit value 1 is set and will return true
-     */
-    auto is_bit_set(uint8_t index) const -> bool;
-
     std::bitset<64U> flags;  ///< Underlying bitset used to read the flags from. Bits 9 - 11 and 52 - 62 can be freely
                              ///< used for additional flagsby the operating system.
   };
+
+  /**
+   * @brief TODO
+   *
+   */
+  struct page_table
+  {
+    entry entries[PAGE_TABLE_ENTRY_COUNT];
+  };
 }  // namespace teachos::arch::memory
 
 #endif  // TEACHOS_ARCH_X86_64_MEMORY_PAGING_HPP
diff --git a/arch/x86_64/src/exception_handling/assert.cpp b/arch/x86_64/src/exception_handling/assert.cpp
new file mode 100644
index 0000000..b55da49
--- /dev/null
+++ b/arch/x86_64/src/exception_handling/assert.cpp
@@ -0,0 +1,24 @@
+#include "arch/video/vga/text.hpp"
+
+namespace teachos::arch::exception_handling
+{
+  auto assert(bool condition, char const * message) -> void
+  {
+    if (condition)
+    {
+      return;
+    }
+
+    video::vga::text::write("Assert failed: ", video::vga::text::common_attributes::green_on_black);
+    video::vga::text::write(message, video::vga::text::common_attributes::green_on_black);
+    for (;;)
+    {
+      // Trick the compiler into thinking the variable is changes at run time,
+      // to prevent the while loop being optimized away
+      // See
+      // https://stackoverflow.com/questions/9495856/how-to-prevent-g-from-optimizing-out-a-loop-controlled-by-a-variable-that-can
+      // for more information.
+      asm volatile("" : "+g"(condition));
+    }
+  }
+}  // namespace teachos::arch::exception_handling
\ No newline at end of file
diff --git a/arch/x86_64/src/kernel/main.cpp b/arch/x86_64/src/kernel/main.cpp
index 7e4a336..c8981a8 100644
--- a/arch/x86_64/src/kernel/main.cpp
+++ b/arch/x86_64/src/kernel/main.cpp
@@ -1,6 +1,7 @@
 #include "arch/kernel/main.hpp"
 
 #include "arch/boot/pointers.hpp"
+#include "arch/exception_handling/assert.hpp"
 #include "arch/memory/frame_allocator.hpp"
 #include "arch/memory/multiboot.hpp"
 #include "arch/video/vga/text.hpp"
@@ -9,31 +10,12 @@
 
 namespace teachos::arch::kernel
 {
-  auto assert(bool condition) -> void
-  {
-    if (condition)
-    {
-      return;
-    }
-
-    video::vga::text::write("Assert failed", video::vga::text::common_attributes::green_on_black);
-    for (;;)
-    {
-      // Trick the compiler into thinking the variable is changes at run time,
-      // to prevent the while loop being optimized away
-      // See
-      // https://stackoverflow.com/questions/9495856/how-to-prevent-g-from-optimizing-out-a-loop-controlled-by-a-variable-that-can
-      // for more information.
-      asm volatile("" : "+g"(condition));
-    }
-  }
-
   auto process_memory_map(arch::memory::memory_map * mminfo, arch::memory::memory_area *& memory_areas,
                           uint8_t & area_count) -> void
   {
     auto expected_entry_size = mminfo->entry_size;
     constexpr auto actual_entry_size = sizeof(arch::memory::memory_area);
-    assert(expected_entry_size == actual_entry_size);
+    arch::exception_handling::assert(expected_entry_size == actual_entry_size, "Unexpected memoryarea entry size");
 
     auto total_size = mminfo->tag.size;
     auto total_entries_size = total_size - sizeof(arch::memory::memory_map) + actual_entry_size;
@@ -48,17 +30,18 @@ namespace teachos::arch::kernel
   {
     auto expected_entry_size = symbol->entry_size;
     constexpr auto actual_entry_size = sizeof(arch::memory::elf_section_header);
-    assert(expected_entry_size == actual_entry_size);
+    arch::exception_handling::assert(expected_entry_size == actual_entry_size,
+                                     "Unexpected elf_section_header entry size");
 
     auto expected_total_size = symbol->tag.size;
     auto actual_total_entry_size = actual_entry_size * symbol->number_of_sections;
     constexpr auto actual_total_section_size = sizeof(arch::memory::elf_symbols_section) - sizeof(uint32_t);
     auto actual_total_size = actual_total_entry_size + actual_total_section_size;
-    assert(expected_total_size == actual_total_size);
+    arch::exception_handling::assert(expected_total_size == actual_total_size, "Unexpected elf_symbols total size");
 
     auto begin = reinterpret_cast<arch::memory::elf_section_header *>(&symbol->end);
     auto end = begin + symbol->number_of_sections;
-    assert(begin->is_null());
+    arch::exception_handling::assert(begin->is_null(), "Missing elf_section_header begin");
 
     std::size_t symbol_table_section_count = 0U;
     std::size_t dynamic_section_count = 0U;
@@ -115,8 +98,8 @@ namespace teachos::arch::kernel
       }
     }
 
-    assert(symbol_table_section_count == 1U);
-    assert(dynamic_section_count <= 1U);
+    arch::exception_handling::assert(symbol_table_section_count == 1U, "Unexpected symbol_table_count value");
+    arch::exception_handling::assert(dynamic_section_count <= 1U, "Unexpected dynamic_section_count value");
   }
 
   template<typename T>
@@ -173,15 +156,6 @@ namespace teachos::arch::kernel
       }
     }
 
-    // Kernel start       0x100000
-    // Kernel end         0x23E943
-    //    Kernel Size       0x13E943 -> 1'304'899
-    // Multiboot start    0x241AA0
-    // Multiboot end      0x242280
-    //    Multiboot Size    0x7E0 -> 2'016
-    // Memory area start  0x241b10
-    //
-    // Address of Frame:  0x203F00
     auto allocator = arch::memory::area_frame_allocator(kernel_start, kernel_end, multiboot_start, multiboot_end,
                                                         memory_areas, area_count);
 
diff --git a/arch/x86_64/src/memory/frame_allocator.cpp b/arch/x86_64/src/memory/frame_allocator.cpp
index 3733cc3..01dcc88 100644
--- a/arch/x86_64/src/memory/frame_allocator.cpp
+++ b/arch/x86_64/src/memory/frame_allocator.cpp
@@ -1,7 +1,11 @@
 #include "arch/memory/frame_allocator.hpp"
 
+#include "arch/exception_handling/assert.hpp"
+
 namespace teachos::arch::memory
 {
+  uint64_t PAGE_SIZE;
+
   physical_frame::physical_frame(std::size_t frame_number)
       : frame_number(frame_number)
   {
@@ -13,6 +17,8 @@ namespace teachos::arch::memory
     return physical_frame{address / PAGE_FRAME_SIZE};
   }
 
+  auto physical_frame::start_address() const -> uint64_t { return frame_number * PAGE_SIZE; }
+
   memory_area_iterator::memory_area_iterator(memory_area * p)
       : ptr(p)
   {
@@ -103,10 +109,8 @@ namespace teachos::arch::memory
 
   auto area_frame_allocator::deallocate_frame(physical_frame physical_frame) -> void
   {
-    // TODO: Fix, simply done because compiler will complain if physical_frame is unused and not compile
-    if (physical_frame.frame_number == 3)
-    {
-    }
+    arch::exception_handling::assert(false && physical_frame.frame_number == 0,
+                                     "[deallocate_frame] Not implemented Exception");
   }
 
   auto area_frame_allocator::begin() -> memory_area_iterator { return area_begin; }
diff --git a/arch/x86_64/src/memory/paging.cpp b/arch/x86_64/src/memory/paging.cpp
index 555357c..90c4199 100644
--- a/arch/x86_64/src/memory/paging.cpp
+++ b/arch/x86_64/src/memory/paging.cpp
@@ -1,34 +1,16 @@
 #include "arch/memory/paging.hpp"
 
+#include "arch/exception_handling/assert.hpp"
+
 namespace teachos::arch::memory
 {
   auto entry::is_unused() const -> bool { return flags == 0U; }
 
   auto entry::set_unused() -> void { flags = 0U; }
 
-  auto entry::present() const -> bool { return is_bit_set(0U); }
-
-  auto entry::writable() const -> bool { return is_bit_set(1U); }
-
-  auto entry::user_accessible() const -> bool { return is_bit_set(2U); }
-
-  auto entry::write_through_caching() const -> bool { return is_bit_set(3U); }
-
-  auto entry::disabled_caching() const -> bool { return is_bit_set(4U); }
-
-  auto entry::is_accessing() const -> bool { return is_bit_set(5U); }
-
-  auto entry::is_diry() const -> bool { return is_bit_set(6U); }
-
-  auto entry::is_huge_page() const -> bool { return is_bit_set(7U); }
-
-  auto entry::is_global() const -> bool { return is_bit_set(8U); }
-
-  auto entry::executing_code_forbidden() const -> bool { return is_bit_set(63U); }
-
   auto entry::calculate_pointed_to_frame() const -> std::optional<physical_frame>
   {
-    if (present())
+    if (contains_flags(1))
     {
       auto physical_address = calculate_physical_address();
       return physical_frame::containing_address(physical_address);
@@ -39,7 +21,7 @@ namespace teachos::arch::memory
   auto entry::calculate_physical_address() const -> std::size_t
   {
     constexpr std::size_t start_bit = 12U;
-    constexpr std::size_t end_bit = 51U;
+    constexpr std::size_t end_bit = 52U;
     size_t value = 0U;
 
     for (auto i = start_bit; i < end_bit; i++)
@@ -49,5 +31,13 @@ namespace teachos::arch::memory
     return value;
   }
 
-  auto entry::is_bit_set(uint8_t index) const -> bool { return flags[index] == 1U; }
+  auto entry::set(physical_frame frame) -> void
+  {
+    arch::exception_handling::assert((frame.start_address() & ~0x000fffff'fffff000) == 0,
+                                     "Start address is not aligned with Page");
+    flags = std::bitset<64U>(frame.start_address()) | flags;
+  }
+
+  auto entry::contains_flags(std::bitset<64U> b) const -> bool { return (flags & b) == b; }
+
 }  // namespace teachos::arch::memory