Fix issue in vector

8 files changed, 92 insertions, 36 deletions

diff --git a/arch/x86_64/include/arch/context_switching/descriptor_table/gdt_flags.hpp b/arch/x86_64/include/arch/context_switching/descriptor_table/gdt_flags.hpp
index 11f5dd4..de41762 100644
--- a/arch/x86_64/include/arch/context_switching/descriptor_table/gdt_flags.hpp
+++ b/arch/x86_64/include/arch/context_switching/descriptor_table/gdt_flags.hpp
@@ -70,10 +70,10 @@ namespace teachos::arch::context_switching::descriptor_table
     auto get_limit() const -> std::bitset<4U>;
 
     /**
-     * @brief Allows to compare the underlying std::bitset of two instances.
+     * @brief Allows to compare the underlying set bits of two instances.
      *
      * @param other Other instance that we want to compare with.
-     * @return Whether the underlying std::bitset of both types is the same.
+     * @return Whether the underlying set bits of both types are the same.
      */
     auto operator==(gdt_flags const & other) const -> bool = default;
 
diff --git a/arch/x86_64/include/arch/context_switching/descriptor_table/global_descriptor_table.hpp b/arch/x86_64/include/arch/context_switching/descriptor_table/global_descriptor_table.hpp
index ab8f1ac..75e1e9d 100644
--- a/arch/x86_64/include/arch/context_switching/descriptor_table/global_descriptor_table.hpp
+++ b/arch/x86_64/include/arch/context_switching/descriptor_table/global_descriptor_table.hpp
@@ -30,7 +30,7 @@ namespace teachos::arch::context_switching::descriptor_table
    * - User Code Segment
    * - User Data Segment
    *
-   * @return Created global_descriptor_table.
+   * @return Copy of the created global_descriptor_table.
    */
   auto create_global_descriptor_table() -> global_descriptor_table;
 
@@ -46,9 +46,9 @@ namespace teachos::arch::context_switching::descriptor_table
    * @brief Initializes the global_descriptor_table and task_state_segment by loading them
    * in the GDTR and TR registers respectively.
    *
-   * @return Created global_descriptor_table.
+   * @return Reference to the created global_descriptor_table.
    */
-  auto initialize_global_descriptor_table() -> global_descriptor_table;
+  auto initialize_global_descriptor_table() -> global_descriptor_table &;
 
 }  // namespace teachos::arch::context_switching::descriptor_table
 
diff --git a/arch/x86_64/include/arch/context_switching/descriptor_table/segment_descriptor.hpp b/arch/x86_64/include/arch/context_switching/descriptor_table/segment_descriptor.hpp
index 7454470..8714eb8 100644
--- a/arch/x86_64/include/arch/context_switching/descriptor_table/segment_descriptor.hpp
+++ b/arch/x86_64/include/arch/context_switching/descriptor_table/segment_descriptor.hpp
@@ -49,6 +49,14 @@ namespace teachos::arch::context_switching::descriptor_table
      */
     auto get_segment_type() const -> segment_descriptor_type;
 
+    /**
+     * @brief Allows to compare the underlying bits of two instances.
+     *
+     * @param other Other instance that we want to compare with.
+     * @return Whether the underlying set bits of both types are the same.
+     */
+    auto operator==(segment_descriptor const & other) const -> bool = default;
+
   private:
     // The order in private variables starts for the first variable being the rightmost bit.
     uint16_t _limit_1 = {};      ///< First part of the limit field (0 - 15)
diff --git a/arch/x86_64/include/arch/context_switching/descriptor_table/task_state_segment.hpp b/arch/x86_64/include/arch/context_switching/descriptor_table/task_state_segment.hpp
index c3b0233..1e306af 100644
--- a/arch/x86_64/include/arch/context_switching/descriptor_table/task_state_segment.hpp
+++ b/arch/x86_64/include/arch/context_switching/descriptor_table/task_state_segment.hpp
@@ -24,9 +24,9 @@ namespace teachos::arch::context_switching::descriptor_table
     uint64_t ist6 = {};
     uint64_t ist7 = {};
     uint64_t : 64;
-    uint32_t : 32;
+    uint16_t : 16;
     uint16_t io_map_base_address = {};
   };
 }  // namespace teachos::arch::context_switching::descriptor_table
 
-#endif  // TEACHOS_ARCH_X86_64_CONTEXT_SWITCHING_DESCRIPTOR_TABLE_TASK_STATE_SEGMENT_HPP
\ No newline at end of file
+#endif  // TEACHOS_ARCH_X86_64_CONTEXT_SWITCHING_DESCRIPTOR_TABLE_TASK_STATE_SEGMENT_HPP
diff --git a/arch/x86_64/include/arch/stl/vector.hpp b/arch/x86_64/include/arch/stl/vector.hpp
index 112af57..f3d41fd 100644
--- a/arch/x86_64/include/arch/stl/vector.hpp
+++ b/arch/x86_64/include/arch/stl/vector.hpp
@@ -162,13 +162,13 @@ namespace teachos::arch::stl
      */
     void push_back(T const & value)
     {
-      _data[_size] = value;
-      _size++;
-
       if (_size == _capacity)
       {
         reserve(_capacity * 2);
       }
+
+      _data[_size] = value;
+      _size++;
     }
 
     /**
@@ -182,13 +182,13 @@ namespace teachos::arch::stl
      */
     void push_back(T && value)
     {
-      _data[_size] = std::move(value);
-      _size++;
-
       if (_size == _capacity)
       {
         reserve(_capacity * 2);
       }
+
+      _data[_size] = std::move(value);
+      _size++;
     }
 
     /**
@@ -206,13 +206,13 @@ namespace teachos::arch::stl
     template<class... Args>
     auto emplace_back(Args &&... args) -> T &
     {
-      _data[_size] = T{std::forward<Args>(args)...};
-      auto const index = _size++;
-
       if (_size == _capacity)
       {
         reserve(_capacity * 2);
       }
+
+      _data[_size] = T{std::forward<Args>(args)...};
+      auto const index = _size++;
       return _data[index];
     }
 
@@ -255,6 +255,30 @@ namespace teachos::arch::stl
     T const * cbegin() const noexcept { return begin(); }
 
     /**
+     * @brief Returns a reverse iterator to the first element of the reversed vector. It corresponds to the last element
+     * of the non-reversed vector. If the vector is empty, the returned iterator will be equal to rend().
+     *
+     * @return Reverse iterator to the first element.
+     */
+    T * rbegin() noexcept { return _data + _size - 1; }
+
+    /**
+     * @brief Returns a reverse iterator to the first element of the reversed vector. It corresponds to the last element
+     * of the non-reversed vector. If the vector is empty, the returned iterator will be equal to rend().
+     *
+     * @return Reverse iterator to the first element.
+     */
+    T const * rbegin() const noexcept { return _data + _size - 1; }
+
+    /**
+     * @brief Returns a reverse iterator to the first element of the reversed vector. It corresponds to the last element
+     * of the non-reversed vector. If the vector is empty, the returned iterator will be equal to rend().
+     *
+     * @return Reverse iterator to the first element.
+     */
+    T const * crbegin() const noexcept { return rbegin(); }
+
+    /**
      * @brief Returns an iterator to the element following the last element of the vector. This element acts as a
      * placeholder, attempting to access it results in undefined behavior.
      *
@@ -279,6 +303,33 @@ namespace teachos::arch::stl
     T const * cend() const noexcept { return end(); }
 
     /**
+     * @brief Returns a reverse iterator to the element following the last element of the reversed vector. It
+     * corresponds to the element preceding the first element of the non-reversed vector. This element acts as a
+     * placeholder, attempting to access it results in undefined behavior.
+     *
+     * @return Reverse iterator to the element following the last element.
+     */
+    T * rend() noexcept { return _data + size - 1; }
+
+    /**
+     * @brief Returns a reverse iterator to the element following the last element of the reversed vector. It
+     * corresponds to the element preceding the first element of the non-reversed vector. This element acts as a
+     * placeholder, attempting to access it results in undefined behavior.
+     *
+     * @return Reverse iterator to the element following the last element.
+     */
+    T const * rend() const noexcept { return _data + size - 1; }
+
+    /**
+     * @brief Returns a reverse iterator to the element following the last element of the reversed vector. It
+     * corresponds to the element preceding the first element of the non-reversed vector. This element acts as a
+     * placeholder, attempting to access it results in undefined behavior.
+     *
+     * @return Reverse iterator to the element following the last element.
+     */
+    T const * crend() const noexcept { return rbegin(); }
+
+    /**
      * @brief Returns a pointer to the underlying array serving as element storage. The pointer is such that range
      * [data(), data() + size()) is always a valid range, even if the container is empty (data() is not dereferenceable
      * in that case).
@@ -320,7 +371,7 @@ namespace teachos::arch::stl
      *
      * @return Reference to the last element.
      */
-    T & back() { return *end(); }
+    T & back() { return *rbegin(); }
 
     /**
      * @brief Returns a reference to the last element in the container. Calling back on an empty container causes
@@ -328,7 +379,7 @@ namespace teachos::arch::stl
      *
      * @return Reference to the last element.
      */
-    T const & back() const { return *end(); }
+    T const & back() const { return *rbegin(); }
 
     /**
      * @brief Increase the capacity of the vector (the total number of elements that the vector can hold without
diff --git a/arch/x86_64/src/context_switching/descriptor_table/global_descriptor_table.cpp b/arch/x86_64/src/context_switching/descriptor_table/global_descriptor_table.cpp
index 77bd3e9..21a76e8 100644
--- a/arch/x86_64/src/context_switching/descriptor_table/global_descriptor_table.cpp
+++ b/arch/x86_64/src/context_switching/descriptor_table/global_descriptor_table.cpp
@@ -54,9 +54,12 @@ namespace teachos::arch::context_switching::descriptor_table
         create_segment_descriptor(segment_descriptor_type::CODE_SEGMENT, access_level::USER);
     segment_descriptor user_data_segment =
         create_segment_descriptor(segment_descriptor_type::DATA_SEGMENT, access_level::USER);
+    // Task State Segment needs to be kept alive
+    static auto tss = new task_state_segment();
+    segment_descriptor tss_descriptor = create_task_state_segment_descriptor(tss);
 
-    global_descriptor_table global_descriptor_table{null_segment, kernel_code_segment, kernel_data_segment,
-                                                    user_code_segment, user_data_segment};
+    global_descriptor_table global_descriptor_table{null_segment,      kernel_code_segment, kernel_data_segment,
+                                                    user_code_segment, user_data_segment,   tss_descriptor};
     return global_descriptor_table;
   }
 
@@ -67,20 +70,15 @@ namespace teachos::arch::context_switching::descriptor_table
                                 access_byte::TASK_STATE_SEGMENT_AVAILABLE};
     gdt_flags tss_gdt_flags{0U, limit};
     uint64_t tss_address = reinterpret_cast<uint64_t>(tss);
-    constexpr uint64_t tss_limit = sizeof(task_state_segment) - 1;
-    segment_descriptor tss_descriptor{tss_access_byte, tss_gdt_flags, tss_address, tss_limit};
-
+    constexpr uint64_t TSS_LIMIT = sizeof(task_state_segment) - 1;
+    segment_descriptor tss_descriptor{tss_access_byte, tss_gdt_flags, tss_address, TSS_LIMIT};
     return tss_descriptor;
   }
 
-  auto initialize_global_descriptor_table() -> global_descriptor_table
+  auto initialize_global_descriptor_table() -> global_descriptor_table &
   {
-    auto gdt = create_global_descriptor_table();
-
-    // Add TSS segment descriptor to GDT
-    auto tss = new task_state_segment();
-    auto tss_descriptor = create_task_state_segment_descriptor(tss);
-    gdt.push_back(tss_descriptor);
+    // Global Descriptor Table needs to be kept alive
+    static auto gdt = create_global_descriptor_table();
 
     // Load GDT into GDTR
     global_descriptor_table_pointer gdt_pointer{static_cast<uint16_t>(gdt.size() - 1), &gdt};
@@ -91,14 +89,13 @@ namespace teachos::arch::context_switching::descriptor_table
         gdt_pointer == stored_gdt_pointer,
         "[Global Descriptor Table] Loaded GDTR value is not the same as the stored value.");
 
-    // Load Task Register (LTR) using the index of TSS descriptor
-    uint16_t tss_selector = (gdt.size() - 1) * sizeof(segment_descriptor);
+    // Calculate the offset of the gdt in bytes to the TSS descriptor
+    uint16_t const tss_selector = (gdt.size() - 1) * sizeof(segment_descriptor);
     kernel::cpu::load_task_register(tss_selector);
 
     auto stored_task_register = kernel::cpu::store_task_register();
     arch::exception_handling::assert(tss_selector == stored_task_register,
                                      "[Global Descriptor Table] Loaded TR value is not the same as the stored value.");
-
     return gdt;
   }
 }  // namespace teachos::arch::context_switching::descriptor_table
diff --git a/arch/x86_64/src/kernel/cpu/tr.cpp b/arch/x86_64/src/kernel/cpu/tr.cpp
index ad38d09..d0e037f 100644
--- a/arch/x86_64/src/kernel/cpu/tr.cpp
+++ b/arch/x86_64/src/kernel/cpu/tr.cpp
@@ -5,12 +5,12 @@ namespace teachos::arch::kernel::cpu
   auto store_task_register() -> uint16_t
   {
     uint16_t current_value{};
-    asm("str %[output]" : [output] "=m"(current_value));
+    asm("str %[output]" : [output] "=r"(current_value));
     return current_value;
   }
 
   auto load_task_register(uint16_t gdt_offset) -> void
   {
-    asm volatile("ltr %[input]" : /* no output from call */ : [input] "m"(gdt_offset));
+    asm volatile("ltr %[input]" : /* no output from call */ : [input] "r"(gdt_offset));
   }
 }  // namespace teachos::arch::kernel::cpu
diff --git a/arch/x86_64/src/kernel/main.cpp b/arch/x86_64/src/kernel/main.cpp
index c1e134a..da6d6d3 100644
--- a/arch/x86_64/src/kernel/main.cpp
+++ b/arch/x86_64/src/kernel/main.cpp
@@ -60,7 +60,7 @@ namespace teachos::arch::kernel
 
     heap_test();
 
-    auto global_descriptor_table = context_switching::descriptor_table::initialize_global_descriptor_table();
+    decltype(auto) global_descriptor_table = context_switching::descriptor_table::initialize_global_descriptor_table();
     (void)global_descriptor_table.at(1);
     video::vga::text::write("GDT FILLED", video::vga::text::common_attributes::green_on_black);
   }