magiskboot can't modify kernel

[AlexLiuDev233]

magiskboot can't repack boot.img when kernel change, keeps reporting

! Recompressed kernel is too large, using original kernel

Full log:

Parsing boot image: [boot.img]
HEADER_VER      [0]
KERNEL_SZ       [6044953]
RAMDISK_SZ      [734108]
SECOND_SZ       [0]
EXTRA_SZ        [0]
OS_VERSION      [11.0.0]
OS_PATCH_LEVEL  [2020-11]
PAGESIZE        [2048]
NAME            []
CMDLINE         [androidboot.hardware=qcom androidboot.bootdevice=msm_sdcc.1 ehci-hcd.park=3 buildvariant=userdebug]
CHECKSUM        [d364514792c193a4eca7c42711738f3fc8df67fb000000000000000000000000]
KERNEL_DTB_SZ   [1075105]
ZIMAGE_KERNEL
KERNEL_FMT      [dtb]
RAMDISK_FMT     [xz]
Repack to boot image: [new-boot.img]
! Recompressed kernel is too large, using original kernel
HEADER_VER      [0]
KERNEL_SZ       [11015073]
RAMDISK_SZ      [732828]
SECOND_SZ       [0]
EXTRA_SZ        [0]
OS_VERSION      [11.0.0]
OS_PATCH_LEVEL  [2020-11]
PAGESIZE        [2048]
NAME            []
CMDLINE         [androidboot.hardware=qcom androidboot.bootdevice=msm_sdcc.1 ehci-hcd.park=3 buildvariant=userdebug]
CHECKSUM        [fdf19409eb0a97a23257b6a367529bd601463365000000000000000000000000]

How to reproduce:

1. Download the boot image and zImage
2. execute magiskboot unpack boot.img
3. replace zImage to kernel file
4. execute magiskboot repack boot.img
5. Problem Reproduced

zImage and boot.img generated by same Android build, generated by command m bootimage
Device tree: https://github.com/YumeMichi/device_oneplus_onyx
Kernel tree: https://github.com/YumeMichi/kernel_oneplus_onyx

Looks that's caused by magiskboot dumped invalid kernel file, it think the kernel file is "dtb"

Device: OnePlus ONE 1001 (codename onyx)
Android version: 11 (LinegaeOS 18.1)
Magisk version name: v30.7
Magisk version code: 30700

[osm0sis]

Likely a duplicate of #9808 ?

[Pzqqt]

KERNEL_FMT      [dtb]

It can be found that magiskboot incorrectly parsed the boot image.

Tracing back through all versions of magiskboot, it was found that v29.0 also had the same problem, but v28.1 worked fine.

Therefore, it can be basically confirmed that this commit was the cause:

Support zImage compression types other than gzip.