Move kernel panic implementation to the kfmt package

src/gopheros/kernel/kfmt/panic.go

@@ -0,0 +1,49 @@
+package kfmt
+
+import (
+	"gopheros/kernel"
+	"gopheros/kernel/cpu"
+	"gopheros/kernel/kfmt/early"
+)
+
+var (
+	// cpuHaltFn is mocked by tests and is automatically inlined by the compiler.
+	cpuHaltFn = cpu.Halt
+
+	errRuntimePanic = &kernel.Error{Module: "rt", Message: "unknown cause"}
+)
+
+// Panic outputs the supplied error (if not nil) to the console and halts the
+// CPU. Calls to Panic never return. Panic also works as a redirection target
+// for calls to panic() (resolved via runtime.gopanic)
+//go:redirect-from runtime.gopanic
+func Panic(e interface{}) {
+	var err *kernel.Error
+
+	switch t := e.(type) {
+	case *kernel.Error:
+		err = t
+	case string:
+		panicString(t)
+		return
+	case error:
+		errRuntimePanic.Message = t.Error()
+		err = errRuntimePanic
+	}
+
+	early.Printf("\n-----------------------------------\n")
+	if err != nil {
+		early.Printf("[%s] unrecoverable error: %s\n", err.Module, err.Message)
+	}
+	early.Printf("*** kernel panic: system halted ***")
+	early.Printf("\n-----------------------------------\n")
+
+	cpuHaltFn()
+}
+
+// panicString serves as a redirect target for runtime.throw
+//go:redirect-from runtime.throw
+func panicString(msg string) {
+	errRuntimePanic.Message = msg
+	Panic(errRuntimePanic)
+}

src/gopheros/kernel/kfmt/panic_test.go

@@ -0,0 +1,121 @@
+package kfmt
+
+import (
+	"bytes"
+	"errors"
+	"gopheros/kernel"
+	"gopheros/kernel/cpu"
+	"gopheros/kernel/driver/video/console"
+	"gopheros/kernel/hal"
+	"testing"
+	"unsafe"
+)
+
+func TestPanic(t *testing.T) {
+	defer func() {
+		cpuHaltFn = cpu.Halt
+	}()
+
+	var cpuHaltCalled bool
+	cpuHaltFn = func() {
+		cpuHaltCalled = true
+	}
+
+	t.Run("with *kernel.Error", func(t *testing.T) {
+		cpuHaltCalled = false
+		fb := mockTTY()
+		err := &kernel.Error{Module: "test", Message: "panic test"}
+
+		Panic(err)
+
+		exp := "\n-----------------------------------\n[test] unrecoverable error: panic test\n*** kernel panic: system halted ***\n-----------------------------------"
+
+		if got := readTTY(fb); got != exp {
+			t.Fatalf("expected to get:\n%q\ngot:\n%q", exp, got)
+		}
+
+		if !cpuHaltCalled {
+			t.Fatal("expected cpu.Halt() to be called by Panic")
+		}
+	})
+
+	t.Run("with error", func(t *testing.T) {
+		cpuHaltCalled = false
+		fb := mockTTY()
+		err := errors.New("go error")
+
+		Panic(err)
+
+		exp := "\n-----------------------------------\n[rt] unrecoverable error: go error\n*** kernel panic: system halted ***\n-----------------------------------"
+
+		if got := readTTY(fb); got != exp {
+			t.Fatalf("expected to get:\n%q\ngot:\n%q", exp, got)
+		}
+
+		if !cpuHaltCalled {
+			t.Fatal("expected cpu.Halt() to be called by Panic")
+		}
+	})
+
+	t.Run("with string", func(t *testing.T) {
+		cpuHaltCalled = false
+		fb := mockTTY()
+		err := "string error"
+
+		Panic(err)
+
+		exp := "\n-----------------------------------\n[rt] unrecoverable error: string error\n*** kernel panic: system halted ***\n-----------------------------------"
+
+		if got := readTTY(fb); got != exp {
+			t.Fatalf("expected to get:\n%q\ngot:\n%q", exp, got)
+		}
+
+		if !cpuHaltCalled {
+			t.Fatal("expected cpu.Halt() to be called by Panic")
+		}
+	})
+
+	t.Run("without error", func(t *testing.T) {
+		cpuHaltCalled = false
+		fb := mockTTY()
+
+		Panic(nil)
+
+		exp := "\n-----------------------------------\n*** kernel panic: system halted ***\n-----------------------------------"
+
+		if got := readTTY(fb); got != exp {
+			t.Fatalf("expected to get:\n%q\ngot:\n%q", exp, got)
+		}
+
+		if !cpuHaltCalled {
+			t.Fatal("expected cpu.Halt() to be called by Panic")
+		}
+	})
+}
+
+func readTTY(fb []byte) string {
+	var buf bytes.Buffer
+	for i := 0; i < len(fb); i += 2 {
+		ch := fb[i]
+		if ch == 0 {
+			if i+2 < len(fb) && fb[i+2] != 0 {
+				buf.WriteByte('\n')
+			}
+			continue
+		}
+
+		buf.WriteByte(ch)
+	}
+
+	return buf.String()
+}
+
+func mockTTY() []byte {
+	// Mock a tty to handle early.Printf output
+	mockConsoleFb := make([]byte, 160*25)
+	mockConsole := &console.Ega{}
+	mockConsole.Init(80, 25, uintptr(unsafe.Pointer(&mockConsoleFb[0])))
+	hal.ActiveTerminal.AttachTo(mockConsole)
+
+	return mockConsoleFb
+}