Define page table entry type

kernel/mem/vmm/pte.go

@@ -0,0 +1,44 @@
+package vmm
+
+import (
+	"github.com/achilleasa/gopher-os/kernel/mem"
+	"github.com/achilleasa/gopher-os/kernel/mem/pmm"
+)
+
+// PageTableEntryFlag describes a flag that can be applied to a page table entry.
+type PageTableEntryFlag uintptr
+
+// pageTableEntry describes a page table entry. These entries encode
+// a physical frame address and a set of flags. The actual format
+// of the entry and flags is architecture-dependent.
+type pageTableEntry uintptr
+
+// HasFlags returns true if this entry has all the input flags set.
+func (pte pageTableEntry) HasFlags(flags PageTableEntryFlag) bool {
+	return (uintptr(pte) & uintptr(flags)) == uintptr(flags)
+}
+
+// HasAnyFlag returns true if this entry has at least one of the input flags set.
+func (pte pageTableEntry) HasAnyFlag(flags PageTableEntryFlag) bool {
+	return (uintptr(pte) & uintptr(flags)) != 0
+}
+
+// SetFlags sets the input list of flags to the page table entry.
+func (pte *pageTableEntry) SetFlags(flags PageTableEntryFlag) {
+	*pte = (pageTableEntry)(uintptr(*pte) | uintptr(flags))
+}
+
+// ClearFlags unsets the input list of flags from the page table entry.
+func (pte *pageTableEntry) ClearFlags(flags PageTableEntryFlag) {
+	*pte = (pageTableEntry)(uintptr(*pte) &^ uintptr(flags))
+}
+
+// Frame returns the physical page frame that this page table entry points to.
+func (pte pageTableEntry) Frame() pmm.Frame {
+	return pmm.Frame((uintptr(pte) & ptePhysPageMask) >> mem.PageShift)
+}
+
+// SetFrame updates the page table entry to point the the given physical frame .
+func (pte *pageTableEntry) SetFrame(frame pmm.Frame) {
+	*pte = (pageTableEntry)((uintptr(*pte) &^ ptePhysPageMask) | frame.Address())
+}

kernel/mem/vmm/pte_test.go

@@ -0,0 +1,61 @@
+package vmm
+
+import (
+	"testing"
+
+	"github.com/achilleasa/gopher-os/kernel/mem/pmm"
+)
+
+func TestPageTableEntryFlags(t *testing.T) {
+	var (
+		pte   pageTableEntry
+		flag1 = PageTableEntryFlag(1 << 10)
+		flag2 = PageTableEntryFlag(1 << 21)
+	)
+
+	if pte.HasAnyFlag(flag1 | flag2) {
+		t.Fatalf("expected HasAnyFlags to return false")
+	}
+
+	pte.SetFlags(flag1 | flag2)
+
+	if !pte.HasAnyFlag(flag1 | flag2) {
+		t.Fatalf("expected HasAnyFlags to return true")
+	}
+
+	if !pte.HasFlags(flag1 | flag2) {
+		t.Fatalf("expected HasFlags to return true")
+	}
+
+	pte.ClearFlags(flag1)
+
+	if !pte.HasAnyFlag(flag1 | flag2) {
+		t.Fatalf("expected HasAnyFlags to return true")
+	}
+
+	if pte.HasFlags(flag1 | flag2) {
+		t.Fatalf("expected HasFlags to return false")
+	}
+
+	pte.ClearFlags(flag1 | flag2)
+
+	if pte.HasAnyFlag(flag1 | flag2) {
+		t.Fatalf("expected HasAnyFlags to return false")
+	}
+
+	if pte.HasFlags(flag1 | flag2) {
+		t.Fatalf("expected HasFlags to return false")
+	}
+}
+
+func TestPageTableEntryFrameEncoding(t *testing.T) {
+	var (
+		pte       pageTableEntry
+		physFrame = pmm.Frame(123)
+	)
+
+	pte.SetFrame(physFrame)
+	if got := pte.Frame(); got != physFrame {
+		t.Fatalf("expected pte.Frame() to return %v; got %v", physFrame, got)
+	}
+}