Buildroot + U-Boot + Rpi4 : Error zImage Bad Magic - raspberry-pi

Question

I am working on a project where I want to create my own embedded linux with U-Boot. Therefore I am working with buildroot, which i recently start learning. After successfully creating my own rasberrypi4_defconfig i am currently struggling at the problem to get u-boot work correctly.
What versions I am working with:
Rpi 4
buildroot-2019.11
u-boot (therefore i pull everyday the new changes)
Current State of the work:
I build on a Ubuntu(32bit). I configure buildroot with the raspberrypi4_defconfig and make it without changes. Then i make a u-boot defconfig for rpi_4_32b_defconfig and create the u-boot.bin with make CROSS_COMPILE=arm-linux-gnueabihf- u-boot.bin
Now my next step was to configure the config.txt and exchange the content with following:
enalbe_uart=1
kernel=u-boot.bin
In addition i copyied my u-boot.bin into my sd-card.
The last step that i actually did is to build my own boot.scr.uimg with following content
fatload mmc O:1 ${fdt_addr_r} bcm2711-rpi-4-b.dtb
fatload mmc 0:1 ${kernel_addr_r} Image.4.8
setenv bootargs console=ttyS0, 115200 \
root=/dev/mmcblk0p2 rootfstype=ext4 rootwait rw
bootz ${kernel_addr_r} - ${fdt_addr_r}
Problem
So far i am archieving to reach the U-boot menu but on booting i get the error: zimage Bad Magic
I actually thing that my boot.scr.uimg is maybe not correct but dont get it.
Boot Log
After calling boot following is printed:
U-Boot 2020.01-rc4-00066-g7e5ee346fc (Dec 05 2019 - 16:55:27 +0100)
DRAM: 948 MiB
RPI 4 Model B (0xc03111)
MMC: emmc2#7e340000: 0, mmcnr#7e300000: 1
Loading Environment from FAT... *** Warning - bad CRC, using default environment
In: serial
Out: serial
Err: serial
Net: Net Initialization Skipped
No ethernet found.
Hit any key to stop autoboot: 0
switch to partitions #0, OK
mmc0 is current device
Scanning mmc 0:1...
Found U-Boot script /boot.scr.uimg
291 bytes read in 17 ms (16.6 KiB/s)
## Executing script at 02400000
40559 bytes read in 33 ms (1.2 MiB/s)
zimage: Bad magic!
SCRIPT FAILED: continuing...
40559 bytes read in 29 ms (1.3 MiB/s)
Card did not respond to voltage select!
No ethernet found.
missing environment variable: pxeuuid
missing environment variable: bootfile
Retrieving file: pxelinux.cfg/00000000
No ethernet found.
missing environment variable: bootfile
Retrieving file: pxelinux.cfg/0000000
No ethernet found.
missing environment variable: bootfile
Retrieving file: pxelinux.cfg/000000
No ethernet found.
missing environment variable: bootfile
Retrieving file: pxelinux.cfg/00000
No ethernet found.
missing environment variable: bootfile
Retrieving file: pxelinux.cfg/0000
No ethernet found.
missing environment variable: bootfile
Retrieving file: pxelinux.cfg/000
No ethernet found.
missing environment variable: bootfile
Retrieving file: pxelinux.cfg/00
No ethernet found.
missing environment variable: bootfile
Retrieving file: pxelinux.cfg/0
No ethernet found.
missing environment variable: bootfile
Retrieving file: pxelinux.cfg/default-arm-bcm283x-rpi
No ethernet found.
missing environment variable: bootfile
Retrieving file: pxelinux.cfg/default-arm-bcm283x
No ethernet found.
missing environment variable: bootfile
Retrieving file: pxelinux.cfg/default-arm
No ethernet found.
missing environment variable: bootfile
Retrieving file: pxelinux.cfg/default
No ethernet found.
Config file not found
No ethernet found.
No ethernet found.
Environment
arch=arm
baudrate=115200
board=rpi
board_name=4 Model B
board_rev=0x11
board_rev_scheme=1
board_revision=0xC03111
boot_a_script=load ${devtype} ${devnum}:${distro_bootpart} ${scriptaddr} ${prefix}${script}; source ${scriptaddr}
boot_efi_binary=if fdt addr ${fdt_addr_r}; then bootefi bootmgr ${fdt_addr_r};else bootefi bootmgr ${fdtcontroladdr};fi;load ${devty
pe} ${devnum}:${distro_bootpart} ${kernel_addr_r} efi/boot/bootarm.efi; if fdt addr ${fdt_addr_r}; then bootefi ${kernel_addr_r} ${f
dt_addr_r};else bootefi ${kernel_addr_r} ${fdtcontroladdr};fi
boot_extlinux=sysboot ${devtype} ${devnum}:${distro_bootpart} any ${scriptaddr} ${prefix}${boot_syslinux_conf}
boot_prefixes=/ /boot/
boot_script_dhcp=boot.scr.uimg
boot_scripts=boot.scr.uimg boot.scr
boot_syslinux_conf=extlinux/extlinux.conf
boot_targets=mmc0 mmc1 pxe dhcp
bootargs=console=ttyS0,115200 \
root=/dev/mmcblk0p2 rootfstype=ext4 rootwait rw
bootcmd=run distro_bootcmd
bootcmd_dhcp=if dhcp ${scriptaddr} ${boot_script_dhcp}; then source ${scriptaddr}; fi;setenv efi_fdtfile ${fdtfile}; if test -z "${f
dtfile}" -a -n "${soc}"; then setenv efi_fdtfile ${soc}-${board}${boardver}.dtb; fi; setenv efi_old_vci ${bootp_vci};setenv efi_old_
arch ${bootp_arch};setenv bootp_vci PXEClient:Arch:00010:UNDI:003000;setenv bootp_arch 0xa;if dhcp ${kernel_addr_r}; then tftpboot $
{fdt_addr_r} dtb/${efi_fdtfile};if fdt addr ${fdt_addr_r}; then bootefi ${kernel_addr_r} ${fdt_addr_r}; else bootefi ${kernel_addr_r
} ${fdtcontroladdr};fi;fi;setenv bootp_vci ${efi_old_vci};setenv bootp_arch ${efi_old_arch};setenv efi_fdtfile;setenv efi_old_arch;s
etenv efi_old_vci;
bootcmd_mmc0=devnum=0; run mmc_boot
bootcmd_mmc1=devnum=1; run mmc_boot
bootcmd_pxe=dhcp; if pxe get; then pxe boot; fi
bootdelay=2
bootfstype=fat
cpu=armv7
dhcpuboot=usb start; dhcp u-boot.uimg; bootm
distro_bootcmd=for target in ${boot_targets}; do run bootcmd_${target}; done
efi_dtb_prefixes=/ /dtb/ /dtb/current/
ethaddr=dc:a6:32:45:1f:d1
fdt_addr=2eff5d00
fdt_addr_r=0x02600000
fdt_high=ffffffff
fdtcontroladdr=3af6ac98
fdtfile=bcm2711-rpi-4-b.dtb
fileaddr=2600000
filesize=9e6f
initrd_high=ffffffff
kernel_addr_r=0x00080000
load_efi_dtb=load ${devtype} ${devnum}:${distro_bootpart} ${fdt_addr_r} ${prefix}${efi_fdtfile}
loadaddr=0x00200000
mmc_boot=if mmc dev ${devnum}; then devtype=mmc; run scan_dev_for_boot_part; fi
pxefile_addr_r=0x02500000
ramdisk_addr_r=0x02700000
scan_dev_for_boot=echo Scanning ${devtype} ${devnum}:${distro_bootpart}...; for prefix in ${boot_prefixes}; do run scan_dev_for_extlinux; run scan_dev_for_scripts; done;run scan_dev_for_efi;
scan_dev_for_boot_part=part list ${devtype} ${devnum} -bootable devplist; env exists devplist || setenv devplist 1; for distro_bootpart in ${devplist}; do if fstype ${devtype} ${devnum}:${distro_bootpart} bootfstype; then run scan_dev_for_boot; fi; done; setenv devplist
scan_dev_for_efi=setenv efi_fdtfile ${fdtfile}; if test -z "${fdtfile}" -a -n "${soc}"; then setenv efi_fdtfile ${soc}-${board}${boardver}.dtb; fi; for prefix in ${efi_dtb_prefixes}; do if test -e ${devtype} ${devnum}:${distro_bootpart} ${prefix}${efi_fdtfile}; then run load_efi_dtb; fi;done;if test -e ${devtype} ${devnum}:${distro_bootpart} efi/boot/bootarm.efi; then echo Found EFI removable media binary efi/boot/bootarm.efi; run boot_efi_binary; echo EFI LOAD FAILED: continuing...; fi; setenv efi_fdtfile
scan_dev_for_extlinux=if test -e ${devtype} ${devnum}:${distro_bootpart} ${prefix}${boot_syslinux_conf}; then echo Found ${prefix}${boot_syslinux_conf}; run boot_extlinux; echo SCRIPT FAILED: continuing...; fi
scan_dev_for_scripts=for script in ${boot_scripts}; do if test -e ${devtype} ${devnum}:${distro_bootpart} ${prefix}${script}; then echo Found U-Boot script ${prefix}${script}; run boot_a_script; echo SCRIPT FAILED: continuing...; fi; done
scriptaddr=0x02400000
serial#=10000000f58b842c
soc=bcm283x
stderr=serial,vidconsole
stdin=serial,usbkbd
stdout=serial,vidconsole
usbethaddr=dc:a6:32:45:1f:d1
vendor=raspberrypi
Environment size: 3996/16380 bytes

Answer 1

So far i am archieving to reach the U-boot menu but on booting i get the error: zimage Bad Magic I actually thing that my boot.scr.uimg is maybe not correct but dont get it.
That error message traces back to the contents of your boot.scr.uimg:
fatload mmc 0:1 ${kernel_addr_r} Image.4.8
...
bootz ${kernel_addr_r} - ${fdt_addr_r}
The bootz command expects a zImage file at the first memory address.
But the prior fatload command has copied a file named Image.4.8 into memory.
By convention an Image file is the generic Linux kernel binary image file, whereas a zImage file is a compressed version of the Linux kernel image that is self-extracting.
You need to install the zImage that you built (instead of the Image file) to the SD card. Edit your boot.scr.uimg to indicate the proper file type/name.
ADDENDUM
U-Boot does have a booti command for the generic Linux kernel binary Image file, but that command is intended only for ARM64, e.g. the built-in help text is boot arm64 Linux Image image from memory.
See the patch that configures that command.