Map physical address of the vga text console framebuffer in DriverInit

Currently, the kernel can write to 0xb80000 because this is part of the
initial identify mapping set up by the rt0 code. When we establish new
mappings for the kernel using its real VMA address then writes to the
framebuffer will cause a page fault unless we explicitly map it.

src/gopheros/device/video/console/probe.go

@@ -1,9 +1,15 @@
 package console
 
-import "gopheros/device"
-import "gopheros/kernel/hal/multiboot"
+import (
+	"gopheros/device"
+	"gopheros/kernel/cpu"
+	"gopheros/kernel/hal/multiboot"
+	"gopheros/kernel/mem/vmm"
+)
 
 var (
+	mapRegionFn          = vmm.MapRegion
+	portWriteByteFn      = cpu.PortWriteByte
 	getFramebufferInfoFn = multiboot.GetFramebufferInfo
 
 	// ProbeFuncs is a slice of device probe functions that is used by

src/gopheros/device/video/console/vga_text.go

@@ -3,16 +3,17 @@ package console
 import (
 	"gopheros/device"
 	"gopheros/kernel"
-	"gopheros/kernel/cpu"
 	"gopheros/kernel/hal/multiboot"
+	"gopheros/kernel/kfmt"
+	"gopheros/kernel/mem"
+	"gopheros/kernel/mem/pmm"
+	"gopheros/kernel/mem/vmm"
 	"image/color"
 	"io"
 	"reflect"
 	"unsafe"
 )
 
-var portWriteByteFn = cpu.PortWriteByte
-
 // VgaTextConsole implements an EGA-compatible 80x25 text console using VGA
 // mode 0x3. The console supports the default 16 EGA colors which can be
 // overridden using the SetPaletteColor method.
@@ -28,6 +29,7 @@ type VgaTextConsole struct {
 	width  uint32
 	height uint32
 
+	fbPhysAddr uintptr
 	fb         []uint16
 
 	palette   color.Palette
@@ -42,13 +44,8 @@ func NewVgaTextConsole(columns, rows uint32, fbPhysAddr uintptr) *VgaTextConsole
 	return &VgaTextConsole{
 		width:      columns,
 		height:     rows,
+		fbPhysAddr: fbPhysAddr,
 		clearChar:  uint16(' '),
-		// overlay a 16bit slice over the fbPhysAddr
-		fb: *(*[]uint16)(unsafe.Pointer(&reflect.SliceHeader{
-			Len:  int(columns * rows),
-			Cap:  int(columns * rows),
-			Data: fbPhysAddr,
-		})),
 		palette: color.Palette{
 			color.RGBA{R: 0, G: 0, B: 1},       /* black */
 			color.RGBA{R: 0, G: 0, B: 128},     /* blue */
@@ -198,7 +195,29 @@ func (cons *VgaTextConsole) DriverVersion() (uint16, uint16, uint16) {
 }
 
 // DriverInit initializes this driver.
-func (cons *VgaTextConsole) DriverInit(_ io.Writer) *kernel.Error { return nil }
+func (cons *VgaTextConsole) DriverInit(w io.Writer) *kernel.Error {
+	// Map the framebuffer so we can write to it
+	fbSize := mem.Size(cons.width * cons.height * 2)
+	fbPage, err := mapRegionFn(
+		pmm.Frame(cons.fbPhysAddr>>mem.PageShift),
+		fbSize,
+		vmm.FlagPresent|vmm.FlagRW,
+	)
+
+	if err != nil {
+		return err
+	}
+
+	cons.fb = *(*[]uint16)(unsafe.Pointer(&reflect.SliceHeader{
+		Len:  int(fbSize >> 1),
+		Cap:  int(fbSize >> 1),
+		Data: fbPage.Address(),
+	}))
+
+	kfmt.Fprintf(w, "mapped framebuffer to 0x%x\n", fbPage.Address())
+
+	return nil
+}
 
 // probeForVgaTextConsole checks for the presence of a vga text console.
 func probeForVgaTextConsole() device.Driver {

src/gopheros/device/video/console/vga_text_test.go

@@ -2,8 +2,12 @@ package console
 
 import (
 	"gopheros/device"
+	"gopheros/kernel"
 	"gopheros/kernel/cpu"
 	"gopheros/kernel/hal/multiboot"
+	"gopheros/kernel/mem"
+	"gopheros/kernel/mem/pmm"
+	"gopheros/kernel/mem/vmm"
 	"image/color"
 	"testing"
 	"unsafe"
@@ -63,6 +67,7 @@ func TestVgaTextFill(t *testing.T) {
 
 	fb := make([]uint16, 80*25)
 	cons := NewVgaTextConsole(80, 25, uintptr(unsafe.Pointer(&fb[0])))
+	cons.fb = fb
 	cw, ch := cons.Dimensions()
 
 	testPat := uint16(0xDEAD)
@@ -101,6 +106,7 @@ nextSpec:
 func TestVgaTextScroll(t *testing.T) {
 	fb := make([]uint16, 80*25)
 	cons := NewVgaTextConsole(80, 25, uintptr(unsafe.Pointer(&fb[0])))
+	cons.fb = fb
 	cw, ch := cons.Dimensions()
 
 	t.Run("up", func(t *testing.T) {
@@ -176,6 +182,7 @@ func TestVgaTextScroll(t *testing.T) {
 func TestVgaTextWrite(t *testing.T) {
 	fb := make([]uint16, 80*25)
 	cons := NewVgaTextConsole(80, 25, uintptr(unsafe.Pointer(&fb[0])))
+	cons.fb = fb
 	defaultFg, defaultBg := cons.DefaultColors()
 
 	t.Run("off-screen", func(t *testing.T) {
@@ -309,12 +316,11 @@ func TestVgaTextSetPaletteColor(t *testing.T) {
 }
 
 func TestVgaTextDriverInterface(t *testing.T) {
+	defer func() {
+		mapRegionFn = vmm.MapRegion
+	}()
 	var dev device.Driver = NewVgaTextConsole(80, 25, 0)
 
-	if err := dev.DriverInit(nil); err != nil {
-		t.Fatal(err)
-	}
-
 	if dev.DriverName() == "" {
 		t.Fatal("DriverName() returned an empty string")
 	}
@@ -322,6 +328,27 @@ func TestVgaTextDriverInterface(t *testing.T) {
 	if major, minor, patch := dev.DriverVersion(); major+minor+patch == 0 {
 		t.Fatal("DriverVersion() returned an invalid version number")
 	}
+
+	t.Run("init success", func(t *testing.T) {
+		mapRegionFn = func(_ pmm.Frame, _ mem.Size, _ vmm.PageTableEntryFlag) (vmm.Page, *kernel.Error) {
+			return 0xb8000, nil
+		}
+
+		if err := dev.DriverInit(nil); err != nil {
+			t.Fatal(err)
+		}
+	})
+
+	t.Run("init fail", func(t *testing.T) {
+		expErr := &kernel.Error{Module: "test", Message: "something went wrong"}
+		mapRegionFn = func(_ pmm.Frame, _ mem.Size, _ vmm.PageTableEntryFlag) (vmm.Page, *kernel.Error) {
+			return 0, expErr
+		}
+
+		if err := dev.DriverInit(nil); err != expErr {
+			t.Fatalf("expected error: %v; got %v", expErr, err)
+		}
+	})
 }
 
 func TestVgaTextProbe(t *testing.T) {