Kernel: Pull apart CPU.h

This does not add any functional changes

Kernel/Arch/x86/common/ASM_wrapper.cpp

@@ -0,0 +1,49 @@
+/*
+ * 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 {
+
+#define XCR_XFEATURE_ENABLED_MASK 0
+
+UNMAP_AFTER_INIT u64 read_xcr0()
+{
+    u32 eax, edx;
+    asm volatile("xgetbv"
+                 : "=a"(eax), "=d"(edx)
+                 : "c"(XCR_XFEATURE_ENABLED_MASK));
+    return eax + ((u64)edx << 32);
+}
+
+UNMAP_AFTER_INIT void write_xcr0(u64 value)
+{
+    u32 eax = value;
+    u32 edx = value >> 32;
+    asm volatile("xsetbv" ::"a"(eax), "d"(edx), "c"(XCR_XFEATURE_ENABLED_MASK));
+}
+
+void stac()
+{
+    if (!Processor::current().has_feature(CPUFeature::SMAP))
+        return;
+    asm volatile("stac" ::
+                     : "cc");
+}
+
+void clac()
+{
+    if (!Processor::current().has_feature(CPUFeature::SMAP))
+        return;
+    asm volatile("clac" ::
+                     : "cc");
+}
+
+}