From 1b65136a11453fe7e89320dfe6170a0cd75e60dd Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Thu, 24 Jul 2025 16:33:10 +0000
Subject: x86_64: clean up hw details

---
 arch/x86_64/src/cpu/registers.cpp | 64 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 arch/x86_64/src/cpu/registers.cpp

(limited to 'arch/x86_64/src/cpu/registers.cpp')

diff --git a/arch/x86_64/src/cpu/registers.cpp b/arch/x86_64/src/cpu/registers.cpp
new file mode 100644
index 0000000..7ade98d
--- /dev/null
+++ b/arch/x86_64/src/cpu/registers.cpp
@@ -0,0 +1,64 @@
+#include "x86_64/cpu/registers.hpp"
+
+#include <type_traits>
+
+namespace teachos::x86_64::cpu
+{
+  auto read_control_register(control_register cr) -> uint64_t
+  {
+    uint64_t current_value;
+    switch (cr)
+    {
+      case control_register::cr0:
+        asm volatile("mov %%cr0, %[output]" : [output] "=r"(current_value));
+        break;
+      case control_register::cr2:
+        asm volatile("mov %%cr2, %[output]" : [output] "=r"(current_value));
+        break;
+      case control_register::cr3:
+        asm volatile("mov %%cr3, %[output]" : [output] "=r"(current_value));
+        break;
+      case control_register::cr4:
+        asm volatile("mov %%cr4, %[output]" : [output] "=r"(current_value));
+        break;
+    }
+    return current_value;
+  }
+
+  auto write_control_register(control_register cr, uint64_t new_value) -> void
+  {
+    switch (cr)
+    {
+      case control_register::cr0:
+        asm volatile("mov %[input], %%cr0"
+                     : /* no output from call */
+                     : [input] "r"(new_value)
+                     : "memory");
+        break;
+      case control_register::cr2:
+        asm volatile("mov %[input], %%cr2"
+                     : /* no output from call */
+                     : [input] "r"(new_value)
+                     : "memory");
+        break;
+      case control_register::cr3:
+        asm volatile("mov %[input], %%cr3"
+                     : /* no output from call */
+                     : [input] "r"(new_value)
+                     : "memory");
+        break;
+      case control_register::cr4:
+        asm volatile("mov %[input], %%cr4"
+                     : /* no output from call */
+                     : [input] "r"(new_value)
+                     : "memory");
+        break;
+    }
+  }
+
+  auto set_cr0_bit(cr0_flags flag) -> void
+  {
+    auto const cr0 = read_control_register(control_register::cr0);
+    write_control_register(control_register::cr0, static_cast<std::underlying_type<cr0_flags>::type>(flag) | cr0);
+  }
+}  // namespace teachos::x86_64::cpu
-- 
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