Android eMMC Booting

时间：2023-12-24 15:38:07

Android eMMC Booting

Contents

[hide]

[edit]eMMC
binaries

This is the efi partition table as exists on the emmc

Sector#    Size Name

    256     128K xloader

    512     256K bootloader

   2048       8M recovery

  18432       8M boot

  34816     512M system

1083392     256M cache

1607680     512M userdata

2656256    2183M media

[edit]Creating
the GPT table

On Target
  1. Connect a USB cable to the OTG port on your platform
  2. Boot your platform up with a stock u-boot and MLO
  3. Once you platform is booted you will see the following:
Fastboot entered...
On Host Machine

locate fastboot in you android filesystem

cd $mydroid/out/host/linux-x86/bin/fastboot

Search for fastboot devices

fastboot devices

Create GPT table on eMMC/SD card

fastboot oem format

From the android build these are the binaries that go into each partition:

 Sector#    Size Name            Binary

    256     128K xloader         MLO

    512     256K bootloader      u-boot.bin

   2048       8M recovery        recovery.img

  18432       8M boot            boot.img

  34816     512M system          system.img

1083392     256M cache           cache.img

1607680     512M userdata        userdata.img

2656256    2183M media           none
File locations

  • MLO --> x-loader/MLO
  • u-boot --> u-boot/u-boot.bin
  • boot.img --> need to create using zImage + ramdisk.img
  • recovery.img ---> need to create using zImage + ramdisk-recovery.img
  • system.img --> $mydroid/out/target/product/<platform>/system.img
  • cache.img -->
  • userdata.img --> $mydroid/out/target/product/<platform>/userdata.img

All these partitions can be flashed with the given binary using fastboot.

 fastboot flash <name> <binary>

Example flashing of all partitions

 fastboot flash xloader     MLO

 fastboot flash bootloader  u-boot.bin

 fastboot flash recovery    recovery.img

 fastboot flash boot        boot.img

 fastboot flash system      system.img

 fastboot flash cache       cache.img

 fastboot flash userdata    userdata.img

[edit]Modifying
.IMG Files

Typically when you want to modify any of the partitions, you would need to unzip-modify-rezip and then fastboot flash.

Following section talks about how to do that for each partition

BOOT.IMG

 boot.img = zImage + ramdisk.img

 zImage = kernel image

 ramdisk.img = out/target/product/blaze/root/

 %./out/host/linux-x86/bin/mkbootimg

 --kernel zImage

 --ramdisk ramdisk.img

 --base 0x80000000

 --cmdline "console=ttyO2,115200n8 mem=456M@0x80000000 mem=512M@0xA0000000 init=/init vram=10M omapfb.vram=0:4M androidboot.console=ttyO2"

 --board omap4

 -o boot.img.new

 Output: boot.img.new

 **Note: bootarg is passed to kernel via --cmdline option above

To "just" boot boot.img (before flashing) you can use:

%fastboot boot boot.img

RAMDISK.IMG

 %mkdir root

 %cd root

 %gunzip -c ../ramdisk.img | cpio -i

 <make changes to root/ contents...>

 %./out/host/linux-x86/bin/mkbootfs root/ | ./out/host/linux-x86/bin/minigzip >ramdisk.img.new

 #output: ramdisk.img.new

 ** Note: any init.rc changes will need to use this method

RECOVERY.IMG

Is just like boot.img.

recovery.img = zImage + ramdisk-recovery.img

*Follow the same steps as boot.img for packing/unpacking

SYSTEM.IMG

 #uncompress

 %./out/host/linux-x86/bin/simg2img system.img system.img.raw

 #mount to directory mnt-point/

 %mkdir mnt-point

 %sudo mount -t ext4 -o loop system.img.raw mnt-point/

 #modify any .so or apk in the mnt-point/ directory

 #rezip

 %sudo out/host/linux-x86/bin/make_ext4fs -s -l 512M -a system system.img.new mnt-point/

 %sudo umount mnt-point/

 Output: system.img.new

Instead of having to reflash the whole big system.img, one can selective update any binary in /system folder on running target

%adb remount

%adb push <local> <remote>

Eg:

%adb remount

%adb push out/target/product/blaze/obj/lib/overlay.omap4.so /system/lib/hw/overlay.omap4.so

%adb sync

USERDATA.IMG

 #uncompress

 %./out/host/linux-x86/bin/simg2img userdata.img userdata.img.raw

 #mount to directory mnt-point/

 %mkdir mnt-point

 %sudo mount -t ext4 -o loop userdata.img.raw mnt-point/

 #modify any .so or apk in the mnt-point/ directory

 #rezip

 #%sudo ./out/host/linux-x86/bin/make_ext4fs -s -l 512M -a userdata userdata.img.new mnt-point/

 # Above command won't work on GB/HC. For GB/HC, please use the following updated command

 %sudo ./out/host/linux-x86/bin/make_ext4fs -s -l 512M -a data userdata.img.new mnt-point/

 %sudo umount mnt-point/

 Output: userdata.img.new

CACHE.IMG

 #This is empty ext4 fs image

 %mkdir mnt-point/

 %sudo ./make_ext4fs -s -l 256M -a cache cache.img mnt-point/

 Output: cache.img

[edit]TI
Android build setup

Copy kernel zImage, u-boot.bin and MLO for your board in folder device/ti/blaze/boot/.

Rename as:

 %mv MLO MLO_es2.2_emu

 or

 %mv MLO MLO_es2.2_gp

 (based on your board being GP or EMU)

Next start standard android build and all img files are generated in:

out/target/product/blaze/*.img

A script is introduced in TI Android release to make this flashing process easier: device/ti/blaze/boot/fastboot.sh

Usage:

cd device/ti/blaze/boot/

%fastboot.sh --emu

or

%fastboot.sh --gp

Running this script will flash whole android system on your board.

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