Fix recursive include using extra file

3 files changed, 43 insertions, 37 deletions

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");
   }