From 125d9f3306ea4bc8888dc991ae3aa87327b0d522 Mon Sep 17 00:00:00 2001 From: Mattijs Korpershoek Date: Wed, 10 Jul 2024 10:40:05 +0200 Subject: bootstd: Add a bootmeth for Android Android boot flow is a bit different than a regular Linux distro. Android relies on multiple partitions in order to boot. A typical boot flow would be: 1. Parse the Bootloader Control Block (BCB, misc partition) 2. If BCB requested bootonce-bootloader, start fastboot and wait. 3. If BCB requested recovery or normal android, run the following: 3.a. Get slot (A/B) from BCB 3.b. Run AVB (Android Verified Boot) on boot partitions 3.c. Load boot and vendor_boot partitions 3.d. Load device-tree, ramdisk and boot The AOSP documentation has more details at [1], [2], [3] This has been implemented via complex boot scripts such as [4]. However, these boot script are neither very maintainable nor generic. Moreover, DISTRO_DEFAULTS is being deprecated [5]. Add a generic Android bootflow implementation for bootstd. For this initial version, only boot image v4 is supported. [1] https://source.android.com/docs/core/architecture/bootloader [2] https://source.android.com/docs/core/architecture/partitions [3] https://source.android.com/docs/core/architecture/partitions/generic-boot [4] https://source.denx.de/u-boot/u-boot/-/blob/master/include/configs/meson64_android.h [5] https://lore.kernel.org/r/all/20230914165615.1058529-17-sjg@chromium.org/ Reviewed-by: Simon Glass Reviewed-by: Julien Masson Tested-by: Guillaume La Roque Signed-off-by: Mattijs Korpershoek --- doc/develop/bootstd.rst | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'doc/develop') diff --git a/doc/develop/bootstd.rst b/doc/develop/bootstd.rst index 34631089ae0..bdda90fae3f 100644 --- a/doc/develop/bootstd.rst +++ b/doc/develop/bootstd.rst @@ -95,6 +95,7 @@ bootflows. Note: it is possible to have a bootmeth that uses a partition or a whole device directly, but it is more common to use a filesystem. +For example, the Android bootmeth uses a whole device. Note that some bootmeths are 'global', meaning that they select the bootdev themselves. Examples include VBE and EFI boot manager. In this case, they @@ -277,6 +278,9 @@ script_offset_f script_size_f Size of the script to load, e.g. 0x2000 +vendor_boot_comp_addr_r + Address to which to load the vendor_boot Android image, e.g. 0xe0000000 + Some variables are set by script bootmeth: devtype @@ -418,6 +422,7 @@ Bootmeth drivers are provided for: - EFI boot using bootefi from disk - VBE - EFI boot using boot manager + - Android bootflow (boot image v4) Command interface @@ -786,6 +791,7 @@ To do Some things that need to be done to completely replace the distro-boot scripts: - implement extensions (devicetree overlays with add-on boards) +- implement legacy (boot image v2) android boot flow Other ideas: -- cgit v1.2.3