From ab6f0b6358549a345be3bdeab734d364ca141acd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mika=C3=ABl=20Cluseau?= <mikael.cluseau@gmail.com>
Date: Tue, 22 Jul 2025 11:00:33 +0200
Subject: [PATCH] remove dep on udev

- remove the need to map host's /dev
- remove race issues or need to have a working `udevadm settle`
---
 cmd/dkl-local-server/boot-img.go |  6 ++-
 cmd/dkl-local-server/udev.go     | 63 ++++++++++++++++++++++++++++++++
 2 files changed, 67 insertions(+), 2 deletions(-)
 create mode 100644 cmd/dkl-local-server/udev.go

diff --git a/cmd/dkl-local-server/boot-img.go b/cmd/dkl-local-server/boot-img.go
index 5d95783..dd1a17a 100644
--- a/cmd/dkl-local-server/boot-img.go
+++ b/cmd/dkl-local-server/boot-img.go
@@ -148,6 +148,7 @@ func setupBootImage(bootImg *os.File, ctx *renderContext) (err error) {
 	}()
 
 	log.Print("device: ", dev)
+	syncSysToDev()
 
 	tempDir := bootImg.Name() + ".p1.mount"
 
@@ -161,9 +162,10 @@ func setupBootImage(bootImg *os.File, ctx *renderContext) (err error) {
 		os.RemoveAll(tempDir)
 	}()
 
-	err = syscall.Mount(dev+"p1", tempDir, "vfat", 0, "")
+	devp1 := dev + "p1"
+	err = syscall.Mount(devp1, tempDir, "vfat", 0, "")
 	if err != nil {
-		return fmt.Errorf("failed to mount %s to %s: %v", dev+"p1", tempDir, err)
+		return fmt.Errorf("failed to mount %s to %s: %v", devp1, tempDir, err)
 	}
 
 	defer func() {
diff --git a/cmd/dkl-local-server/udev.go b/cmd/dkl-local-server/udev.go
new file mode 100644
index 0000000..e2e49e0
--- /dev/null
+++ b/cmd/dkl-local-server/udev.go
@@ -0,0 +1,63 @@
+package main
+
+import (
+	"bytes"
+	"log"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"syscall"
+
+	"golang.org/x/sys/unix"
+)
+
+// Simulate a udev run for our needs
+func syncSysToDev() {
+	// loop devices
+	sysPaths, _ := filepath.Glob("/sys/devices/virtual/block/loop*/**/dev")
+	for _, sysPath := range sysPaths {
+		mknodBlk(sysPath)
+	}
+}
+
+func mknodBlk(sysPath string) {
+	devPath := "/dev/" + filepath.Base(filepath.Dir(sysPath))
+	if _, err := os.Stat(devPath); os.IsNotExist(err) {
+		// ok
+	} else if err != nil {
+		log.Printf("stat %s failed: %v", devPath, err)
+		return
+	} else {
+		return // exists
+	}
+
+	devBytes, err := os.ReadFile(sysPath)
+	if err != nil {
+		log.Printf("read %s failed: %v", sysPath, err)
+		return
+	}
+	devBytes = bytes.TrimSpace(devBytes)
+
+	// rust: let Some(dev) = devBytes.split_once(':').filter_map(|a,b| Some(mkdev(a.parse().ok()?, b.parse().ok()?)));
+	majorStr, minorStr, ok := strings.Cut(string(devBytes), ":")
+	if !ok {
+		log.Printf("%s: invalid dev string: %s", sysPath, string(devBytes))
+		return
+	}
+	major, err := strconv.ParseUint(majorStr, 10, 32)
+	if err != nil {
+		log.Printf("%s: invalid major: %q", sysPath, majorStr)
+		return
+	}
+	minor, err := strconv.ParseUint(minorStr, 10, 32)
+	if err != nil {
+		log.Printf("%s: invalid minor: %q", sysPath, minorStr)
+		return
+	}
+
+	devMajMin := int(unix.Mkdev(uint32(major), uint32(minor)))
+
+	log.Printf("mknod %s b %d %d", devPath, major, minor)
+	unix.Mknod(devPath, syscall.S_IFBLK|0o0600, devMajMin)
+}