Hold a fatal error on the framebuffer and reboot in five minutes rather than exiting, since init's death drops the kernel's panic screen over the cause

fatal.go

@@ -0,0 +1,112 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"os/signal"
+	"strings"
+	"syscall"
+	"time"
+
+	"golang.org/x/sys/unix"
+)
+
+const fatalRebootDelay = 5 * time.Minute
+
+var fatalCh = make(chan any, 1)
+
+// Deferred in every goroutine that can panic: as PID 1 the message is shown by
+// the run loop instead of killing init; anywhere else the panic keeps its stack.
+func holdPanic() {
+	p := recover()
+	if p == nil {
+		return
+	}
+	if os.Getpid() != 1 {
+		panic(p)
+	}
+	select {
+	case fatalCh <- p:
+	default:
+	}
+}
+
+// Exiting would take init with it and the kernel's panic screen would cover
+// the cause, so it is drawn and held instead, with a reboot to retry.
+func fatal(cause error) {
+	if os.Getpid() != 1 {
+		panic(cause)
+	}
+	if err := drawFatal(cause); err != nil {
+		panic(fmt.Sprintf("%v; drawing it: %v", cause, err))
+	}
+	sig := make(chan os.Signal, 1)
+	signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
+	select {
+	case <-sig:
+	case <-time.After(fatalRebootDelay):
+	}
+	if err := unix.Reboot(unix.LINUX_REBOOT_CMD_RESTART); err != nil {
+		panic(err)
+	}
+}
+
+func drawFatal(cause error) error {
+	fb, err := openFramebuffer()
+	if err != nil {
+		return err
+	}
+	title, err := loadFace(true, 40)
+	if err != nil {
+		return err
+	}
+	body, err := loadFace(false, 34)
+	if err != nil {
+		return err
+	}
+
+	fb.fill(uiBg)
+	noteY := fb.h - spaceRow - body.lineH
+	y := spaceRow
+	title.draw(fb, spaceRow, y-title.capTop, "FATAL", uiRed)
+	y += title.lineH + spaceRow
+	for _, line := range wrapWords(cause.Error(), (fb.w-2*spaceRow)/body.cellW) {
+		if y+body.lineH > noteY-spaceRow {
+			body.draw(fb, spaceRow, y-body.capTop, "...", uiFg)
+			break
+		}
+		body.draw(fb, spaceRow, y-body.capTop, line, uiFg)
+		y += body.lineH + spaceTight
+	}
+	note := fmt.Sprintf("rebooting in %d minutes", int(fatalRebootDelay.Minutes()))
+	body.draw(fb, spaceRow, noteY-body.capTop, note, uiDim)
+	return fb.flush()
+}
+
+func wrapWords(s string, cols int) []string {
+	var lines []string
+	line := ""
+	for _, w := range strings.Fields(s) {
+		for len(w) > cols {
+			if line != "" {
+				lines = append(lines, line)
+				line = ""
+			}
+			lines = append(lines, w[:cols])
+			w = w[cols:]
+		}
+		switch {
+		case line == "":
+			line = w
+		case len(line)+1+len(w) <= cols:
+			line += " " + w
+		default:
+			lines = append(lines, line)
+			line = w
+		}
+	}
+	if line != "" {
+		lines = append(lines, line)
+	}
+	return lines
+}