bootloader/lk: add support for UC20 lk bootloader with V2 lkenv structs

This commit adds support for the UC20 LittleKernel bootloader to snapd.

The big changes for using V2 are that we now use a secure bootloader set kernel
command line parameter to identify what disk to look for bootloader environment
structures, and that we use different lkenv structs for different role
bootloaders.

Eventually we should make V1 also use a secure bootloader set kernel command
line parameter to identify what disk to look for bootloader environment
structures on too, as using the partition label like this is vulnerable to
attack by attaching a USB disk with the same partition label to the system.

Signed-off-by: Ian Johnson <ian.johnson@canonical.com>

bootloader/export_test.go

@@ -28,6 +28,8 @@ import (
 
 	"github.com/snapcore/snapd/bootloader/lkenv"
 	"github.com/snapcore/snapd/bootloader/ubootenv"
+	"github.com/snapcore/snapd/osutil"
+	"github.com/snapcore/snapd/osutil/disks"
 )
 
 // creates a new Androidboot bootloader object
@@ -72,14 +74,16 @@ func MockGrubFiles(c *C, rootdir string) {
 	c.Assert(err, IsNil)
 }
 
-func NewLk(rootdir string, opts *Options) Bootloader {
+func NewLk(rootdir string, opts *Options) ExtractedRecoveryKernelImageBootloader {
 	if opts == nil {
-		opts = &Options{}
+		opts = &Options{
+			Role: RoleSole,
+		}
 	}
-	return newLk(rootdir, opts)
+	return newLk(rootdir, opts).(ExtractedRecoveryKernelImageBootloader)
 }
 
-func LkConfigFile(b Bootloader) string {
+func LkConfigFile(b Bootloader) (string, error) {
 	lk := b.(*lk)
 	return lk.envFile()
 }
@@ -89,23 +93,98 @@ func UbootConfigFile(b Bootloader) string {
 	return u.envFile()
 }
 
-func MockLkFiles(c *C, rootdir string, opts *Options) {
+func MockLkFiles(c *C, rootdir string, opts *Options) (restore func()) {
+	var cleanups []func()
 	if opts == nil {
-		opts = &Options{}
+		// default to v1, uc16/uc18 version for test simplicity
+		opts = &Options{
+			Role: RoleSole,
+		}
+	}
+
+	l := &lk{
+		rootdir:       rootdir,
+		inRuntimeMode: !opts.PrepareImageTime,
+		role:          opts.Role,
+	}
+
+	var version lkenv.Version
+	switch opts.Role {
+	case RoleSole:
+		version = lkenv.V1
+	case RoleRunMode:
+		version = lkenv.V2Run
+	case RoleRecovery:
+		version = lkenv.V2Recovery
+	}
+
+	// setup some role specific things
+	if opts.Role == RoleRunMode || opts.Role == RoleRecovery {
+		// then we need to setup some additional files - namely the kernel
+		// command line and a mock disk for that
+		lkBootDisk := &disks.MockDiskMapping{
+			FilesystemLabelToPartUUID: map[string]string{
+				"snapbootsel":        "snapbootsel-partuuid",
+				"snapbootselbak":     "snapbootselbak-partuuid",
+				"snaprecoverysel":    "snaprecoverysel-partuuid",
+				"snaprecoveryselbak": "snaprecoveryselbak-partuuid",
+				"boot_a":             "boot-a-partuuid",
+				"boot_b":             "boot-b-partuuid",
+			},
+			DiskHasPartitions: true,
+			DevNum:            "lk-boot-disk-dev-num",
+		}
+
+		m := map[string]*disks.MockDiskMapping{
+			"lk-boot-disk": lkBootDisk,
+		}
+
+		// mock the disk
+		r := disks.MockDeviceNameDisksToPartitionMapping(m)
+		cleanups = append(cleanups, r)
+
+		// create the disk files so they exist for
+
+		// now mock the kernel command line
+		cmdLine := filepath.Join(c.MkDir(), "cmdline")
+		ioutil.WriteFile(cmdLine, []byte("snapd_lk_boot_disk=lk-boot-disk"), 0644)
+		r = osutil.MockProcCmdline(cmdLine)
+		cleanups = append(cleanups, r)
 	}
-	l := &lk{rootdir: rootdir, inRuntimeMode: !opts.PrepareImageTime}
-	err := os.MkdirAll(l.dir(), 0755)
-	c.Assert(err, IsNil)
 
-	// first create empty env file
+	// next create empty env file
 	buf := make([]byte, 4096)
-	err = ioutil.WriteFile(l.envFile(), buf, 0660)
+	f, err := l.envFile()
 	c.Assert(err, IsNil)
+
+	c.Assert(os.MkdirAll(filepath.Dir(f), 0755), IsNil)
+	err = ioutil.WriteFile(f, buf, 0660)
+	c.Assert(err, IsNil)
+
 	// now write env in it with correct crc
-	env := lkenv.NewEnv(l.envFile(), lkenv.V1)
+	env := lkenv.NewEnv(f, version)
 	env.InitializeBootPartitions("boot_a", "boot_b")
 	err = env.Save()
 	c.Assert(err, IsNil)
+
+	// also make the empty files for the boot_a and boot_b partitions for uc20
+	// roles
+	if opts.Role == RoleRunMode || opts.Role == RoleRecovery {
+		for _, label := range []string{"boot_a", "boot_b"} {
+			disk, err := disks.DiskFromDeviceName("lk-boot-disk")
+			c.Assert(err, IsNil)
+			partUUID, err := disk.FindMatchingPartitionUUID(label)
+			c.Assert(err, IsNil)
+			bootFile := filepath.Join(rootdir, "/dev/disk/by-partuuid", partUUID)
+			c.Assert(os.MkdirAll(filepath.Dir(bootFile), 0755), IsNil)
+			c.Assert(ioutil.WriteFile(bootFile, nil, 0755), IsNil)
+		}
+	}
+	return func() {
+		for _, r := range cleanups {
+			r()
+		}
+	}
 }
 
 func LkRuntimeMode(b Bootloader) bool {