Implement early page allocator

kernel/hal/multiboot/multiboot.go

@@ -101,6 +101,15 @@ const (
 	memUnknown
 )
 
+var (
+	infoData uintptr
+)
+
+// MemRegionVisitor defies a visitor function that gets invoked by VisitMemRegions
+// for each memory region provided by the boot loader. The visitor must return true
+// to continue or false to abort the scan.
+type MemRegionVisitor func(entry *MemoryMapEntry) bool
+
 // MemoryMapEntry describes a memory region entry, namely its physical address,
 // its length and its type.
 type MemoryMapEntry struct {
@@ -114,14 +123,21 @@ type MemoryMapEntry struct {
 	Type MemoryEntryType
 }
 
-var (
-	infoData uintptr
-)
-
-// MemRegionVisitor defies a visitor function that gets invoked by VisitMemRegions
-// for each memory region provided by the boot loader. The visitor must return true
-// to continue or false to abort the scan.
-type MemRegionVisitor func(entry *MemoryMapEntry) bool
+// String implements fmt.Stringer for MemoryEntryType.
+func (t MemoryEntryType) String() string {
+	switch t {
+	case MemAvailable:
+		return "available"
+	case MemReserved:
+		return "reserved"
+	case MemAcpiReclaimable:
+		return "ACPI (reclaimable)"
+	case MemNvs:
+		return "NVS"
+	default:
+		return "unknown"
+	}
+}
 
 // SetInfoPtr updates the internal multiboot information pointer to the given
 // value. This function must be invoked before invoking any other function

kernel/hal/multiboot/multiboot_test.go

@@ -102,6 +102,25 @@ func TestVisitMemRegion(t *testing.T) {
 	}
 }
 
+func TestMemoryEntryTypeStringer(t *testing.T) {
+	specs := []struct {
+		input MemoryEntryType
+		exp   string
+	}{
+		{MemAvailable, "available"},
+		{MemReserved, "reserved"},
+		{MemAcpiReclaimable, "ACPI (reclaimable)"},
+		{MemNvs, "NVS"},
+		{MemoryEntryType(123), "unknown"},
+	}
+
+	for specIndex, spec := range specs {
+		if got := spec.input.String(); got != spec.exp {
+			t.Errorf("[spec %d] expected MemoryEntryType(%d).String() to return %q; got %q", specIndex, spec.input, spec.exp, got)
+		}
+	}
+}
+
 func TestGetFramebufferInfo(t *testing.T) {
 	SetInfoPtr(uintptr(unsafe.Pointer(&emptyInfoData[0])))