Fix recursive include using extra file

10 files changed, 73 insertions, 59 deletions

diff --git a/arch/x86_64/CMakeLists.txt b/arch/x86_64/CMakeLists.txt
index 1ce2731..3d6d2c7 100644
--- a/arch/x86_64/CMakeLists.txt
+++ b/arch/x86_64/CMakeLists.txt
@@ -101,6 +101,7 @@ target_sources("_context" PRIVATE
   "src/context_switching/segment_descriptor_table/segment_descriptor_extension.cpp"
   "src/context_switching/main.cpp"
   "src/context_switching/syscall/main.cpp"
+  "src/context_switching/syscall/syscall_enable.cpp"
   "src/context_switching/syscall/syscall_handler.cpp"
   "src/context_switching/interrupt_descriptor_table/gate_descriptor.cpp"
   "src/context_switching/interrupt_descriptor_table/idt_flags.cpp"
diff --git a/arch/x86_64/include/arch/context_switching/syscall/main.hpp b/arch/x86_64/include/arch/context_switching/syscall/main.hpp
index c75268a..ae4c2db 100644
--- a/arch/x86_64/include/arch/context_switching/syscall/main.hpp
+++ b/arch/x86_64/include/arch/context_switching/syscall/main.hpp
@@ -1,14 +1,22 @@
 #ifndef TEACHOS_ARCH_X86_64_CONTEXT_SWITCHING_SYSCALL_MAIN_HPP
 #define TEACHOS_ARCH_X86_64_CONTEXT_SWITCHING_SYSCALL_MAIN_HPP
 
-#include "arch/context_switching/syscall/syscall_handler.hpp"
-
-#include <array>
 #include <cstdint>
-#include <optional>
 
 namespace teachos::arch::context_switching::syscall
 {
+  enum class type : uint64_t
+  {
+    WRITE = 1U
+  };
+
+  enum class error
+  {
+    OK = 0U,
+  };
+
+  constexpr bool operator!(error e) { return e == error::OK; }
+
   struct arguments
   {
     uint64_t arg_0{};
@@ -19,9 +27,7 @@ namespace teachos::arch::context_switching::syscall
     uint64_t arg_5{};
   };
 
-  auto enable_syscall() -> void;
-
-  auto syscall(type syscall_number, arguments args = {}) -> uint64_t;
+  auto syscall(type syscall_number, arguments args = {}) -> error;
 
 }  // namespace teachos::arch::context_switching::syscall
 
diff --git a/arch/x86_64/include/arch/context_switching/syscall/syscall_enable.hpp b/arch/x86_64/include/arch/context_switching/syscall/syscall_enable.hpp
new file mode 100644
index 0000000..59b97b2
--- /dev/null
+++ b/arch/x86_64/include/arch/context_switching/syscall/syscall_enable.hpp
@@ -0,0 +1,10 @@
+#ifndef TEACHOS_ARCH_X86_64_CONTEXT_SWITCHING_SYSCALL_SYSCALL_ENABLE_HPP
+#define TEACHOS_ARCH_X86_64_CONTEXT_SWITCHING_SYSCALL_SYSCALL_ENABLE_HPP
+
+namespace teachos::arch::context_switching::syscall
+{
+  auto enable_syscall() -> void;
+
+}  // namespace teachos::arch::context_switching::syscall
+
+#endif  // TEACHOS_ARCH_X86_64_CONTEXT_SWITCHING_SYSCALL_SYSCALL_ENABLE_HPP
diff --git a/arch/x86_64/include/arch/context_switching/syscall/syscall_handler.hpp b/arch/x86_64/include/arch/context_switching/syscall/syscall_handler.hpp
index e076995..2e7bcd1 100644
--- a/arch/x86_64/include/arch/context_switching/syscall/syscall_handler.hpp
+++ b/arch/x86_64/include/arch/context_switching/syscall/syscall_handler.hpp
@@ -5,16 +5,11 @@
 
 namespace teachos::arch::context_switching::syscall
 {
-  enum type : uint64_t
-  {
-    WRITE = 1U
-  };
-
   /**
    * @brief Handler for SYSCALL instruction. Calls a specific implementation based
    * on the register RAX.
    *
-   * @return Returns with SYSRETQ
+   * @return Returns with LEAVE, SYSRETQ
    */
   auto syscall_handler() -> void;
 
diff --git a/arch/x86_64/include/arch/user/main.hpp b/arch/x86_64/include/arch/user/main.hpp
index 7127d07..4f1d005 100644
--- a/arch/x86_64/include/arch/user/main.hpp
+++ b/arch/x86_64/include/arch/user/main.hpp
@@ -7,4 +7,4 @@ namespace teachos::arch::user
 
 }  // namespace teachos::arch::user
 
-#endif  // TEACHOS_ARCH_X86_64_USER_MAIN_HPP
\ No newline at end of file
+#endif  // TEACHOS_ARCH_X86_64_USER_MAIN_HPP
diff --git a/arch/x86_64/src/context_switching/main.cpp b/arch/x86_64/src/context_switching/main.cpp
index a112924..9539428 100644
--- a/arch/x86_64/src/context_switching/main.cpp
+++ b/arch/x86_64/src/context_switching/main.cpp
@@ -1,15 +1,12 @@
 #include "arch/context_switching/main.hpp"
 
 #include "arch/boot/pointers.hpp"
-#include "arch/context_switching/syscall/main.hpp"
-#include "arch/exception_handling/assert.hpp"
+#include "arch/context_switching/syscall/syscall_enable.hpp"
 #include "arch/kernel/cpu/call.hpp"
-#include "arch/kernel/cpu/control_register.hpp"
 #include "arch/kernel/cpu/if.hpp"
 #include "arch/kernel/cpu/segment_register.hpp"
 #include "arch/kernel/cpu/tr.hpp"
 #include "arch/user/main.hpp"
-#include "arch/video/vga/text.hpp"
 
 namespace teachos::arch::context_switching
 {
diff --git a/arch/x86_64/src/context_switching/syscall/main.cpp b/arch/x86_64/src/context_switching/syscall/main.cpp
index 9ac63ce..a226e23 100644
--- a/arch/x86_64/src/context_switching/syscall/main.cpp
+++ b/arch/x86_64/src/context_switching/syscall/main.cpp
@@ -1,39 +1,8 @@
 #include "arch/context_switching/syscall/main.hpp"
 
-#include "arch/context_switching/interrupt_descriptor_table/segment_selector.hpp"
-#include "arch/exception_handling/assert.hpp"
-#include "arch/exception_handling/panic.hpp"
-#include "arch/kernel/cpu/msr.hpp"
-
-#include <cstdint>
-
 namespace teachos::arch::context_switching::syscall
 {
-  namespace
-  {
-    constexpr interrupt_descriptor_table::segment_selector KERNEL_CODE_SEGMENT_SELECTOR{
-        1U, interrupt_descriptor_table::segment_selector::REQUEST_LEVEL_KERNEL};
-
-    auto constexpr IA32_STAR_ADDRESS = 0xC0000081;
-    auto constexpr IA32_LSTAR_ADDRESS = 0xC0000082;
-    auto constexpr IA32_FMASK_ADDRESS = 0xC0000084;
-
-  }  // namespace
-
-  auto enable_syscall() -> void
-  {
-    uint64_t const syscall_function = reinterpret_cast<uint64_t>(syscall_handler);
-    kernel::cpu::write_msr(IA32_LSTAR_ADDRESS, syscall_function);
-    kernel::cpu::write_msr(IA32_FMASK_ADDRESS, 0U);
-
-    uint64_t const kernel_cs = KERNEL_CODE_SEGMENT_SELECTOR;
-    uint64_t const star_value = (kernel_cs << 32) | (kernel_cs << 48);
-    kernel::cpu::write_msr(IA32_STAR_ADDRESS, star_value);
-
-    kernel::cpu::set_efer_bit(kernel::cpu::efer_flags::SCE);
-  }
-
-  auto syscall(type syscall_number, arguments args) -> uint64_t
+  auto syscall(type syscall_number, arguments args) -> error
   {
     asm volatile("mov %[input], %%rax"
                  : /* no output from call */
@@ -49,7 +18,7 @@ namespace teachos::arch::context_switching::syscall
 
     asm volatile("syscall");
 
-    uint64_t error{};
+    error error{};
     asm volatile("mov %%rax, %[output]" : [output] "=m"(error));
     return error;
   }
diff --git a/arch/x86_64/src/context_switching/syscall/syscall_enable.cpp b/arch/x86_64/src/context_switching/syscall/syscall_enable.cpp
new file mode 100644
index 0000000..e6265d3
--- /dev/null
+++ b/arch/x86_64/src/context_switching/syscall/syscall_enable.cpp
@@ -0,0 +1,32 @@
+#include "arch/context_switching/syscall/syscall_enable.hpp"
+
+#include "arch/context_switching/interrupt_descriptor_table/segment_selector.hpp"
+#include "arch/context_switching/syscall/syscall_handler.hpp"
+#include "arch/kernel/cpu/msr.hpp"
+
+namespace teachos::arch::context_switching::syscall
+{
+  namespace
+  {
+    constexpr interrupt_descriptor_table::segment_selector KERNEL_CODE_SEGMENT_SELECTOR{
+        1U, interrupt_descriptor_table::segment_selector::REQUEST_LEVEL_KERNEL};
+
+    auto constexpr IA32_STAR_ADDRESS = 0xC0000081;
+    auto constexpr IA32_LSTAR_ADDRESS = 0xC0000082;
+    auto constexpr IA32_FMASK_ADDRESS = 0xC0000084;
+
+  }  // namespace
+
+  auto enable_syscall() -> void
+  {
+    uint64_t const syscall_function = reinterpret_cast<uint64_t>(syscall_handler);
+    kernel::cpu::write_msr(IA32_LSTAR_ADDRESS, syscall_function);
+    kernel::cpu::write_msr(IA32_FMASK_ADDRESS, 0U);
+
+    uint64_t const kernel_cs = KERNEL_CODE_SEGMENT_SELECTOR;
+    uint64_t const star_value = (kernel_cs << 32) | (kernel_cs << 48);
+    kernel::cpu::write_msr(IA32_STAR_ADDRESS, star_value);
+
+    kernel::cpu::set_efer_bit(kernel::cpu::efer_flags::SCE);
+  }
+}  // namespace teachos::arch::context_switching::syscall
\ No newline at end of file
diff --git a/arch/x86_64/src/context_switching/syscall/syscall_handler.cpp b/arch/x86_64/src/context_switching/syscall/syscall_handler.cpp
index 759a092..fbfecc0 100644
--- a/arch/x86_64/src/context_switching/syscall/syscall_handler.cpp
+++ b/arch/x86_64/src/context_switching/syscall/syscall_handler.cpp
@@ -1,5 +1,6 @@
 #include "arch/context_switching/syscall/syscall_handler.hpp"
 
+#include "arch/context_switching/syscall/main.hpp"
 #include "arch/exception_handling/panic.hpp"
 #include "arch/video/vga/text.hpp"
 
@@ -8,11 +9,12 @@ namespace teachos::arch::context_switching::syscall
 
   namespace
   {
-    auto write_to_vga_buffer(uint64_t buffer)
+    auto write_to_vga_buffer(uint64_t buffer) -> error
     {
       video::vga::text::write(reinterpret_cast<const char *>(buffer),
                               video::vga::text::common_attributes::green_on_black);
       video::vga::text::newline();
+      return error::OK;
     }
   }  // namespace
 
@@ -38,17 +40,17 @@ namespace teachos::arch::context_switching::syscall
     // and now.
     asm volatile("mov %%rax, %[output]" : [output] "=m"(syscall_number));
 
+    error result = error::OK;
     switch (static_cast<type>(syscall_number))
     {
-      case WRITE:
-        write_to_vga_buffer(arg_0);
+      case type::WRITE:
+        result = write_to_vga_buffer(arg_0);
         break;
       default:
         teachos::arch::exception_handling::panic("[Syscall Handler] Invalid syscall number");
         break;
     }
 
-    uint64_t result = 0U;
     asm volatile("mov %[input], %%rax"
                  : /* no output from call */
                  : [input] "m"(result)
@@ -63,6 +65,9 @@ namespace teachos::arch::context_switching::syscall
                  : [input] "m"(rflags)
                  : "memory");
 
+    // Additionally call leave, because x86 allocates tack space for the internal variables. If we do not clean up this
+    // newly created stack frame the syscall instruction that landed in this syscall_handler, will never return to the
+    // method that originally called it, becuase the RIP has not been restored from the previous stack frame.
     asm volatile("leave\n"
                  "sysretq");
   }
diff --git a/arch/x86_64/src/user/main.cpp b/arch/x86_64/src/user/main.cpp
index 6d8eea7..8ce21ba 100644
--- a/arch/x86_64/src/user/main.cpp
+++ b/arch/x86_64/src/user/main.cpp
@@ -7,7 +7,6 @@
 
 namespace teachos::arch::user
 {
-
   [[gnu::section(".user_text")]]
   auto main() -> void
   {
@@ -23,9 +22,9 @@ namespace teachos::arch::user
     // Actual Source: https://man7.org/linux/man-pages/man2/syscall.2.html More cleare documentation:
     // https://sys.readthedocs.io/en/latest/doc/05_calling_system_calls.html
 
-    const char syscall_message[68] = "Successfully entered user mode and wrote to VGA buffer via syscall!";
-    auto error = context_switching::syscall::syscall(context_switching::syscall::WRITE,
-                                                     {reinterpret_cast<uint64_t>(&syscall_message)});
+    char constexpr syscall_message[] = "Successfully entered user mode and wrote to VGA buffer via syscall!";
+    auto const error = context_switching::syscall::syscall(context_switching::syscall::type::WRITE,
+                                                           {reinterpret_cast<uint64_t>(&syscall_message)});
 
     if (!error)
     {