m/{n,t}/installer: init
This adds partial implementation of the installer [1].
It needs to be integrated with the installer bundle to become
functional.
[1] https://github.com/monogon-dev/monogon/issues/44
Change-Id: I6223e50dc02bc1ad1a8d1351b556ecba43f30a2f
Reviewed-on: https://review.monogon.dev/c/monogon/+/408
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
diff --git a/metropolis/pkg/sysfs/block.go b/metropolis/pkg/sysfs/block.go
new file mode 100644
index 0000000..f253777
--- /dev/null
+++ b/metropolis/pkg/sysfs/block.go
@@ -0,0 +1,127 @@
+// Copyright 2020 The Monogon Project Authors.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Implementation included in this file was written with the aim of easing
+// integration with the interface exposed at /sys/class/block. It assumes sysfs
+// is already mounted at /sys.
+package sysfs
+
+import (
+ "fmt"
+ "os"
+ "path/filepath"
+ "strconv"
+ "strings"
+)
+
+// PartUUIDMap returns a mapping between partition UUIDs and block device
+// names based on information exposed by uevent. UUID keys of the returned
+// map are represented as lowercase strings.
+func PartUUIDMap() (map[string]string, error) {
+ m := make(map[string]string)
+ // Get a list of block device symlinks from sysfs.
+ const blkDirPath = "/sys/class/block"
+ blkDevs, err := os.ReadDir(blkDirPath)
+ if err != nil {
+ return m, fmt.Errorf("couldn't read %q: %w", blkDirPath, err)
+ }
+ // Iterate over block device symlinks present in blkDevs, creating a mapping
+ // in m for each device with both PARTUUID and DEVNAME keys present in their
+ // respective uevent files.
+ for _, devInfo := range blkDevs {
+ // Read the uevent file and transform it into a string->string map.
+ kv, err := ReadUevents(filepath.Join(blkDirPath, devInfo.Name(), "uevent"))
+ if err != nil {
+ return m, fmt.Errorf("while reading uevents: %w", err)
+ }
+ // Check that the required keys are present in the map.
+ if uuid, name := kv["PARTUUID"], kv["DEVNAME"]; uuid != "" && name != "" {
+ m[uuid] = name
+ }
+ }
+ return m, nil
+}
+
+// DeviceByPartUUID returns a block device name, given its corresponding
+// partition UUID.
+func DeviceByPartUUID(uuid string) (string, error) {
+ pm, err := PartUUIDMap()
+ if err != nil {
+ return "", err
+ }
+ if bdev, ok := pm[strings.ToLower(uuid)]; ok {
+ return bdev, nil
+ }
+ return "", fmt.Errorf("couldn't find a block device matching the partition UUID %q", uuid)
+}
+
+// ParentBlockDevice transforms the block device name of a partition, eg
+// "sda1", to the name of the block device hosting it, eg "sda".
+func ParentBlockDevice(dev string) (string, error) {
+ // Build a path pointing to a sysfs block device symlink.
+ partLink := filepath.Join("/sys/class/block", dev)
+ // Read the symlink at partLink. This should leave us with a path of the form
+ // (...)/sda/sdaN.
+ linkTgt, err := os.Readlink(partLink)
+ if err != nil {
+ return "", fmt.Errorf("couldn't read the block device symlink at %q: %w", partLink, err)
+ }
+ // Remove the last element from the path, leaving us with a path pointing to
+ // the block device containting the installer partition, of the form
+ // (...)/sda.
+ devPath := filepath.Dir(linkTgt)
+ // Get the last element of the path, leaving us with just the block device
+ // name, eg sda
+ devName := filepath.Base(devPath)
+ return devName, nil
+}
+
+// PartitionBlockDevice returns the name of a block device associated with the
+// partition at index in the containing block device dev, eg "nvme0n1pN" for
+// "nvme0n1" or "sdaN" for "sda".
+func PartitionBlockDevice(dev string, index int) (string, error) {
+ dp := filepath.Join("/sys/class/block", dev)
+ dir, err := os.ReadDir(dp)
+ if err != nil {
+ return "", err
+ }
+ for _, info := range dir {
+ // Skip non-directories
+ if !info.IsDir() {
+ continue
+ }
+ // Check whether the directory contains a file named 'partition'. If that's
+ // the case, read the partition index from it and compare it with the one
+ // supplied as a function parameter. If they're equal, return the directory
+ // name.
+ istr, err := os.ReadFile(filepath.Join(dp, info.Name(), "partition"))
+ if os.IsNotExist(err) {
+ continue
+ }
+ if err != nil {
+ return "", err
+ }
+ // istr holds a newline-terminated ASCII-encoded decimal number.
+ pi, err := strconv.Atoi(strings.TrimSuffix(string(istr), "\n"))
+ if err != nil {
+ return "", fmt.Errorf("failed to parse partition index: %w", err)
+ }
+ if pi == index {
+ return info.Name(), nil
+ }
+ }
+ return "", fmt.Errorf("couldn't find partition %d of %q", index, dev)
+}