Kernel: Pull apart CPU.h

This does not add any functional changes

Kernel/Arch/x86/i386/ASM_wrapper.cpp

@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Types.h>
+
+#include <Kernel/Arch/x86/ASM_wrapper.h>
+#include <Kernel/Arch/x86/CPU.h>
+#include <Kernel/Arch/x86/Processor.h>
+
+namespace Kernel {
+
+UNMAP_AFTER_INIT void write_cr0(FlatPtr value)
+{
+    asm volatile("mov %%eax, %%cr0" ::"a"(value));
+}
+
+UNMAP_AFTER_INIT void write_cr4(FlatPtr value)
+{
+    asm volatile("mov %%eax, %%cr4" ::"a"(value));
+}
+FlatPtr read_cr0()
+{
+    FlatPtr cr0;
+    asm("mov %%cr0, %%eax"
+        : "=a"(cr0));
+    return cr0;
+}
+
+FlatPtr read_cr2()
+{
+    FlatPtr cr2;
+    asm("mov %%cr2, %%eax"
+        : "=a"(cr2));
+    return cr2;
+}
+
+FlatPtr read_cr3()
+{
+    FlatPtr cr3;
+    asm("mov %%cr3, %%eax"
+        : "=a"(cr3));
+    return cr3;
+}
+
+void write_cr3(FlatPtr cr3)
+{
+    // NOTE: If you're here from a GPF crash, it's very likely that a PDPT entry is incorrect, not this!
+    asm volatile("mov %%eax, %%cr3" ::"a"(cr3)
+                 : "memory");
+}
+
+FlatPtr read_cr4()
+{
+    FlatPtr cr4;
+    asm("mov %%cr4, %%eax"
+        : "=a"(cr4));
+    return cr4;
+}
+
+#define DEFINE_DEBUG_REGISTER(index)                         \
+    FlatPtr read_dr##index()                                 \
+    {                                                        \
+        FlatPtr value;                                       \
+        asm("mov %%dr" #index ", %%eax"                      \
+            : "=a"(value));                                  \
+        return value;                                        \
+    }                                                        \
+    void write_dr##index(FlatPtr value)                      \
+    {                                                        \
+        asm volatile("mov %%eax, %%dr" #index ::"a"(value)); \
+    }
+
+DEFINE_DEBUG_REGISTER(0);
+DEFINE_DEBUG_REGISTER(1);
+DEFINE_DEBUG_REGISTER(2);
+DEFINE_DEBUG_REGISTER(3);
+DEFINE_DEBUG_REGISTER(6);
+DEFINE_DEBUG_REGISTER(7);
+
+}