Simplify syscall setup

2 files changed, 12 insertions, 29 deletions

diff --git a/arch/x86_64/src/context_switching/main.cpp b/arch/x86_64/src/context_switching/main.cpp
index 85cefe5..155d150 100644
--- a/arch/x86_64/src/context_switching/main.cpp
+++ b/arch/x86_64/src/context_switching/main.cpp
@@ -6,6 +6,7 @@
 #include "arch/kernel/cpu/call.hpp"
 #include "arch/kernel/cpu/control_register.hpp"
 #include "arch/kernel/cpu/if.hpp"
+#include "arch/kernel/cpu/msr.hpp"
 #include "arch/kernel/cpu/segment_register.hpp"
 #include "arch/kernel/cpu/tr.hpp"
 #include "arch/video/vga/text.hpp"
@@ -14,6 +15,10 @@ namespace teachos::arch::context_switching
 {
   namespace
   {
+    auto constexpr IA32_STAR_ADDRESS = 0xC0000081;
+    auto constexpr IA32_LSTAR_ADDRESS = 0xC0000082;
+    auto constexpr IA32_FMASK_ADDRESS = 0xC0000084;
+
     constexpr interrupt_descriptor_table::segment_selector KERNEL_CODE_SEGMENT_SELECTOR{
         1U, interrupt_descriptor_table::segment_selector::REQUEST_LEVEL_KERNEL};
     constexpr kernel::cpu::far_pointer KERNEL_CODE_POINTER{&kernel::cpu::reload_data_segment_registers,
@@ -74,34 +79,13 @@ namespace teachos::arch::context_switching
 
   auto setup_syscall() -> void
   {
-    uint64_t handler = reinterpret_cast<uint64_t>(syscall_handler);
-    asm volatile(
-        /* Write syscall_handler pointer in IA32_LSTAR MSR */
-        "mov $0xC0000082, %%ecx\n" /* IA32_LSTAR MSR */
-        "mov %[syscall_handler], %%rax"
-        "mov %[syscall_handler], %%rdx"
-        "shr $32, %%rdx\n"
-        "wrmsr\n"
-
-        /* Write RFLAGS Mask in IA32_LSTAR MSR */
-        "mov $0xC0000084, %%ecx\n" /* IA32_FMASK MSR */
-        "mov $0x0, %%rax\n"        /* RFLAGS Mask lower 32 bits */
-        "mov $0x0, %%rdx\n"        /* RFLAGS Mask upper 32 bits */
-        "wrmsr\n"
-
-        /* Write kernel code segment offset in IA32_STAR MSR */
-        "mov $0xC0000081, %%ecx\n" /* IA32_STAR MSR */
-        "mov $0x10, %%rax\n"       /* kernel code segment offset lower 32 bits */
-        "mov $0x0, %%rdx\n"        /* kernel code segment offset upper 32 bits */
-        "wrmsr\n"
-
-        /* Set SCE bit in MSR_EFER (enabling syscall instruction)*/
-        "mov $0xC0000080, %%ecx\n"
-        "rdmsr\n"
-        "or $0x1, %%eax\n"
-        "wrmsr"
-        : /* no output from call */
-        : [syscall_handler] "r"(handler));
+    uint64_t const syscall_function = reinterpret_cast<uint64_t>(syscall_handler);
+    uint64_t const segment_selector = *reinterpret_cast<uint64_t const *>(&KERNEL_CODE_SEGMENT_SELECTOR);
+
+    kernel::cpu::write_msr(IA32_LSTAR_ADDRESS, syscall_function);
+    kernel::cpu::write_msr(IA32_FMASK_ADDRESS, 0U);
+    kernel::cpu::write_msr(IA32_STAR_ADDRESS, segment_selector);
+    kernel::cpu::set_efer_bit(kernel::cpu::efer_flags::SCE);
   }
 
 }  // namespace teachos::arch::context_switching
diff --git a/arch/x86_64/src/context_switching/syscall_handler.cpp b/arch/x86_64/src/context_switching/syscall_handler.cpp
index 1bc4ef9..283d297 100644
--- a/arch/x86_64/src/context_switching/syscall_handler.cpp
+++ b/arch/x86_64/src/context_switching/syscall_handler.cpp
@@ -4,7 +4,6 @@
 
 namespace teachos::arch::context_switching
 {
-  [[gnu::naked]]
   auto syscall_handler() -> void
   {
     uint64_t dummy{};