1 files changed, 84 insertions, 0 deletions
diff --git a/src/shared/control_regs.rs b/src/shared/control_regs.rs
new file mode 100644
index 0000000..4893445
--- /dev/null
+++ b/src/shared/control_regs.rs
@@ -0,0 +1,84 @@
+//! Functions to read and write control registers.
+//! See Intel Vol. 3a Section 2.5, especially Figure 2.6.
+
+bitflags! {
+    pub flags Cr0: usize {
+        const EnablePaging = 1 << 31,
+        const CacheDisable = 1 << 30,
+        const NotWriteThrough = 1 << 29,
+        const AlignmentMask = 1 << 18,
+        const WriteProtect = 1 << 16,
+        const NumericError = 1 << 5,
+        const ExtensionType = 1 << 4,
+        const TaskSwitched = 1 << 3,
+        const EmulateCoprocessor = 1 << 2,
+        const MonitorCoprocessor = 1 << 1,
+        const ProtectedMode = 1 << 0,
+    }
+}
+
+bitflags! {
+    pub flags Cr4: usize {
+        const EnableSmap = 1 << 21,
+        const EnableSmep = 1 << 20,
+        const EnableOsXSave = 1 << 18,
+        const EnablePcid = 1 << 17,
+        const EnableSmx = 1 << 14,
+        const EnableVmx = 1 << 13,
+        const UnmaskedSse = 1 << 10,
+        const EnableSse = 1 << 9,
+        const EnablePpmc = 1 << 8,
+        const EnableGlobalPages = 1 << 7,
+        const EnableMachineCheck = 1 << 6,
+        const EnablePae = 1 << 5,
+        const EnablePse = 1 << 4,
+        const DebuggingExtensions = 1 << 3,
+        const TimeStampDisable = 1 << 2,
+        const VirtualInterrupts = 1 << 1,
+        const EnableVme = 1 << 0,
+    }
+}
+
+
+/// Read cr0
+pub unsafe fn cr0() -> Cr0 {
+    let ret: usize;
+    asm!("mov %cr0, $0" : "=r" (ret));
+    Cr0::from_bits_truncate(ret)
+}
+
+/// Write cr0.
+pub unsafe fn cr0_write(val: Cr0) {
+    asm!("mov $0, %cr0" :: "r" (val.bits) : "memory");
+}
+
+/// Contains page-fault linear address.
+pub unsafe fn cr2() -> usize {
+    let ret: usize;
+    asm!("mov %cr2, $0" : "=r" (ret));
+    ret
+}
+
+/// Contains page-table root pointer.
+pub unsafe fn cr3() -> usize {
+    let ret: usize;
+    asm!("mov %cr3, $0" : "=r" (ret));
+    ret
+}
+
+/// Switch page-table PML4 pointer.
+pub unsafe fn cr3_write(val: usize) {
+    asm!("mov $0, %cr3" :: "r" (val) : "memory");
+}
+
+/// Contains various flags to control operations in protected mode.
+pub unsafe fn cr4() -> Cr4 {
+    let ret: usize;
+    asm!("mov %cr4, $0" : "=r" (ret));
+    Cr4::from_bits_truncate(ret)
+}
+
+/// Write cr4.
+pub unsafe fn cr4_write(val: Cr4) {
+    asm!("mov $0, %cr4" :: "r" (val.bits) : "memory");
+}