1 files changed, 9 insertions, 0 deletions
diff --git a/arch/x86_64/src/context_switching/main.cpp b/arch/x86_64/src/context_switching/main.cpp
index 287ced4..4e13b1c 100644
--- a/arch/x86_64/src/context_switching/main.cpp
+++ b/arch/x86_64/src/context_switching/main.cpp
@@ -62,7 +62,16 @@ namespace teachos::arch::context_switching
       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 kernel_cs = KERNEL_CODE_SEGMENT_SELECTOR;    // Your 64-bit kernel code segment selector
+      uint64_t user_cs = USER_CODE_SEGMENT_SELECTOR + 0x3;  // User mode code segment selector (RPL=3)
+
+      uint64_t star_value = (user_cs << 48) | (kernel_cs << 32);
+
+      kernel::cpu::write_msr(IA32_STAR_ADDRESS, star_value);
       kernel::cpu::write_msr(IA32_STAR_ADDRESS, KERNEL_CODE_SEGMENT_SELECTOR);
+
+      // kernel::cpu::write_msr(IA32_STAR_ADDRESS, KERNEL_CODE_SEGMENT_SELECTOR);
       kernel::cpu::set_efer_bit(kernel::cpu::efer_flags::SCE);
     }