The current mechanism for specifying boot devices on Android systems
involves passing a set of "boot_devices" though command line,
bootconfig, or device tree.
The bootdevices are specified as strings and, in general, need to
match a sysfs path but without the "/sys/devices" or
"/sys/devices/platform" prefix. The sysfs path is generally the path
to the closest parent of the block device that is a "platform" device.
As an example, if the sysfs path of the expected boot device is:
/sys/devices/platform/soc@0/7c4000.mmc/mmc_host/mmc1/mmc1:0001/block/mmcblk1
The bootloader would specify it as "soc@0/7c4000.mmc" since:
* We strip off "/sys/devices/platform/"
* As we move up directories, we don't find one whose subsystem is
"platform" until we get up to
"/sys/devices/platform/soc@0/7c4000.mmc".
The current mechanism is a bit brittle. Specifically:
* The sysfs path isn't _really_ stable and can change across kernel
upgrades. For instance, during one kernel upgrade the device tree
for a product changed so that the root node changed from "soc" to
"soc@0" and this changed all sysfs paths. In the past device tree
folks have asserted that we shouldn't rely on dts node names to stay
consistent, yet those node names are used to construct sysfs paths.
* For some devices, like USB, the path of the closest "platform"
device tends to be the path of the USB controller. This means that
if two USB disks are plugged in we can't guarantee which one will be
identified as the boot device.
Add a new method of finding the boot device by passing the partition
UUID that we loaded the kernel from. Using the partition UUID to
identify the boot device is standard on Linux. You can see this
because when you're not using an initramfs you can use the syntax
"root=PARTUUID=<valid-uuid-id>[/PARTNROFF=n]" to specify the root.
Using the same idea for Android's boot code makes sense.
With this new method for finding the boot device, we can make the code
much more specific about matching sysfs paths. Once we find the sysfs
path for the kernel we can make sure that all of the other boot
partition share the same "scsi" or "mmc" parent instead of going all
the way to the closest platform device. In the above example, this
means that we'd make sure that all boot devices are found under this
sysfs node:
/sys/devices/platform/soc@0/7c4000.mmc/mmc_host/mmc1/mmc1:0001/block/mmcblk1
...instead of just making sure they are under:
/sys/devices/platform/soc@0/7c4000.mmc
There is the question of what we should do if the bootloader passes
_both_ an old style "boot_devices" and also a partition UUID. In this
case, we'll issue a warning and then ignore the old "boot_devices".
Considering it a warning rather than an error could allow switching to
the "boot_part_uuid" method even if an old bootloader is still
hardcoding some old "boot_devices".
NOTE: Using partition UUID won't cause any security problems even
though someone _could_ plug in an external device crafted to have the
same UUID as the normal boot device's kernel partition. We already
have "verity" in the system making sure our filesystems are not
tampered with and this would also protect us from booting a tampered
disk. That means that the worst someone could do in this case would be
to confuse the system and make the device non-bootable. Chromebooks
have been using the partition UUID to find the root filesystems for
years and this has never been a problem.
NOTE: this new method relies on the commit ("init: Add partition_uuid
to Uevent") which in turn relies upstream kernel commit 74f4a8dc0dd8
("block: add partition uuid into uevent as "PARTUUID"").
Bug: 316324155
Test: Use partition UUID to boot
Change-Id: If824cb700ca3696a442a28e6ad02d7c522c3b495
This reverts commit 5bfb93678f.
Reason for revert: b/376468452 and trusty boot up on arm64. This CL is causing a lot of troubles (now only on emulator, but may affect more devices in field) and shall be reverted. Desktop team will handle support for selecting single boot source (while having more than one) as part of boot_part_uuid support (at aosp/3318438).
Change-Id: I2804c119631f592d0862f3472ffe18dbb23b17e5
This reverts commit 8d71220df2.
Reason for revert: Fix for gcar emulator (basically all QEMU-based emulators) landed at aosp/3315253 and aosp/3160116.
Change-Id: If4eddd3f7e224c31019ad3bd752e2375c7567780
Init code is bailing out as soon as `super` partition was
found in the system, ignoring rest of uevents.
In case given device contains multiple boot sources, `super`
partition as well as all other partitions shall be taken
from the same boot source, instead of relying on
`which uevent came first`.
Bug: 309244873, 349144493
Test: Plug secondary USB boot device to device that supports multiple
boot sources. Select boot from USB. Device boots properly.
Signed-off-by: Jan Dabros <dabros@google.com>
Signed-off-by: Konrad Adamczyk <konrada@google.com>
Change-Id: I70eb7d4223258ec273faa523cb67ddab0b7c32a0
This change allows init to ensure that a specified virtio-console
device file (`/dev/hvc*`) is available before `ueventd` coldboot.
Times out if device path is not encountered within 10 seconds.
Bug: 325538592
Test: build bertha_x86_64 and bertha_arm64
Change-Id: Ia1512e69ea607bf4d235595caa53668e2dac500c
The derivation happens in the derive_microdroid_vendor_dice_node binary
which first_stage_init forks and execvs.
Since the derivation requires talking to the dice driver, its
initialisation is also moved to the first stage init.
The derivation happens before the microdroid vendor partition is
verified & mounted. This should be safe because the first_stage_init
will fail the boot if the verification of the microdroid vendor
partition fails.
Bug: 287593065
Test: run microdroid with and without vendor partition
Test: atest MicrodroidTests
Change-Id: I0d83772eb98a56c315617e66ec64bd03639cfde6
Allow mapping of raw block devices (those without a partition table)
to partition names for first stage mount and ueventd. For example, a
block device `vdb` that contains only an ext4 metadata partition could
be mapped to `metadata` such that /dev/block/by-name/metadata is
created.
The mapping is provided by the `androidboot.partition_map` bootconfig
or kernel command line parameter.
Bug: 159943320
Test: boot with raw vdb,metadata;vdc,userdata partitions
Change-Id: Ib6a939d6fb88b85c46c81d613425a127627a734b
In first-stage init, libsnapshot needs to know how to wait for device
paths, since ueventd isn't running yet. We do this by passing a callback
wrapping BlockDevInitializer.
Bug: 173476209
Test: device boots into first-stage init after full VABC ota
Change-Id: I9a87f98824e65a9379cb0b99c001e28cccd9d205
This allows init to easily ensure misc devices other than device-mapper
are present.
Bug: 154536437
Test: manual test
Change-Id: I49495684edee322f9787ce7ab7f79d0e8060171d
This will make it possible to re-use in second-stage init.
Bug: 150315914
Test: first-stage init boots
Change-Id: I6a0f13d5c71ab5529a76751f68ac0f15834323d1
