Apply DualBoot with DualBoot Kernel Patcher

This guide will help you build a boot image with uefi/android dualboot feature.

Prepare

• An android device.
• Download UEFI FD file from Github Action(You may need to login to download artifacts) or Release Page of uefi repository.
• Magiskboot for your environment, there are prebuilt binaries on github.
• DualBoot kernel patcher binary and shellcode binaries for your devices from release page or action page.

:::Notice All these steps can be done on your android device. :::

Steps

Assume you have done the following steps on your android device.

1. Root your device with magisk.
2. Downloaded and installed termux.
3. Installed root-repo and tsu in termux with apt.

• Get Android Boot Image.

  • The boot image usually can be found at /dev/block/by-name/boot or /dev/block/by-name/boot_a (or _b).
  • Open your termux, and copy the boot image out for future use.

  tsu                             # get root shell
  mkdir /sdcard/dualboot/         # create a folder to put files.
  cp /dev/block/by-name/boot /sdcard/dualboot/boot.img  # copy to our folder and rename to boot.img. If your device has ab slot, please add _a or _b suffix.

• Unpack it with magiskboot.

  • If your device was rooted by magisk, there should be an magiskboot binary at /data/adb/magisk/magiskboot
  • By the way you can press the tab button in termux to automatically fill path, instead of typing the characters one by one.
  • Do Unpack

  cd /sdcard/dualboot/            # change working directory to our folder.
  /data/adb/magisk/magiskboot unpack boot.img # unpack

  • You will get something like this:

  /sdcard/dualboot# /data/adb/magisk/magiskboot unpack boot.img
  Parsing boot image: [boot.img]
  HEADER_VER      [1]
  KERNEL_SZ       [41576325]
  RAMDISK_SZ      [927736]
  SECOND_SZ       [0]
  RECOV_DTBO_SZ   [0]
  OS_VERSION      [9.0.0]
  OS_PATCH_LEVEL  [2021-05]
  PAGESIZE        [4096]
  NAME            []
  CMDLINE         [console=ttyMSM0,115200n8 earlycon=msm_geni_serial,0xa90000 androidboot.hardware=qcom androidboot.console=ttyMSM0 androidboot.memcg=1 lpm_levels.sleep_disabled=1 video=vfb:640x400,bpp=32,memsize=3072000 msm_rtb.filter=0x237 service_locator.enable=1 swiotlb=2048 firmware_class.path=/vendor/firmware_mnt/image loop.max_part=7 androidboot.usbcontroller=a600000.dwc3 buildvariant=user]
  CHECKSUM        [e73518a6e1edf3062d9cebd3203a51069ef2f424000000000000000000000000]
  KERNEL_DTB_SZ   [3972965]
  KERNEL_FMT      [raw]
  RAMDISK_FMT     [raw]
  /sdcard/dualboot# ls
  boot  kernel  kernel_dtb  ramdisk.cpio

::: TIP Please do not patch a patched kernel. :::

• Apply patch with dualboot kernel patcher.

  • Assume the patcher and shellcodes and config you downloaded above was saved at /sdcard/Download/
  • Unpack these zips with these cmds, or extract in file manager.

  unzip /sdcard/Download/Shellcodes.zip
  unzip /sdcard/Download/DualBootKernelPatcher-Linux-arm64.zip
  unzip /sdcard/Download/Config.zip

  • Give permission to dualboot kernel patcher

  mv DualBootKernelPatcher ~/
  chmod +x ~/DualBootKernelPatcher

  • Patch kernel with a shellcode.

  ./DualBootKernelPatcher /sdcard/dualboot/patched_kernel <Path-to>/SM8150_EFI.fd /sdcard/dualboot/kernel <Path-To>/Config/DualBoot.Sm8150.cfg <Path-To>/ShellCode.XXXX.bin

  • Repack boot image with patched kernel

  cd /sdcard/dualboot/
  mv patched_kernel kernel
  /data/adb/magisk/magiskboot repack boot.img

  • You will get a file named new-boot.img if magiskboot success.

• Test with fastboot.

  • Send new-boot.img to your computer:

  adb pull /sdcard/dualboot/new-boot.img

  • Reboot to fastboot

  adb reboot bootloader

  • Ensure OS-switch is on the correct state before it loading. Like magnet shell or tri-state key.
  • Try load boot image once.

  fastboot boot new-boot.img

  • See if the device is entering a correct os.

• Flash boot image into disk

  • If everything goes well and boot image was backuped. You can flash boot image into disk now. Then no fastboot command is required when using dualboot.
  • Flash boot:

  fastboot flash boot new-boot.img

• Recover original boot image:

  • If you want to remove dualboot, flash your backuped boot image.

  fastboot flash boot.img

Remove dualboot

Run DualBootPatchRemover on the patched kernel and rebuild the boot image. After flashing to boot parition the dualboot feature will disappear.