Code
Introduction
Very brief instructions on how to build the FreeBSD kernel using the code in the repository and then booting it on the BeagleBoard.
Disclaimer
These instructions work for me, however it's entirely likely that I may have missed some files that I should have uploaded to the repo, or my build system produces different binaries.
In addition, I build my kernel on OSX using a modified CodeSourcery ARM toolchain, I haven't tried building the kernel on an actual FreeBSD system.
Building the Kernel
Copy the files from the repo into the FreeBSD tree, I suggest you use some graphical merge program as some of my changes might not be applicable and unnecessary. To build type the following command.
make buildkernel KERNCONF=BEAGLEBOARD TARGET=arm MACHINE_ARCH=armIf you've already built the kernel once and just modified one or two files you can run the following commands which just builds the changed files and re-links.
make buildkernel KERNFAST=BEAGLEBOARD TARGET=arm MACHINE_ARCH=armThe build process should produce a **kernel.bin** binary file and a **kernel** ELF file. # Running the Kernel # ## Running the flat binary kernel ## Copy the **kernel.bin** file onto the root directory of a MMC or SD card and chuck it in the BeagleBoard. At the u-boot prompt, type the following:
*OMAP3 beagleboard.org #* mmc init
*OMAP3 beagleboard.org #* fatload mmc 0 0x80200000 kernel.bin
*OMAP3 beagleboard.org #* go 0x80200000
Note: On older versions of the Beagleboard and u-boot the mmc init command might be just mmcinit. i.e.
*OMAP3 beagleboard.org #* mmcinit
*OMAP3 beagleboard.org #* fatload mmc 0 0x80200000 kernel.bin
*OMAP3 beagleboard.org #* go 0x80200000
After that you should see the kernel start-up messages coming out the serial port.
Running the ELF kernel
The process is a bit more complex, because u-boot expects a special header in front of ELF files. You will need the mkimage binary that can be installed from ports in devel/u-boot. To get it installed, type in the following commands:
*host %* cd /usr/ports/devel/u-boot
*host %* sudo make install
Once mkimage is installed, you can convert your kernel image file into an image that u-boot can load and run. Since u-boot doesn't support FreeBSD images, the following command instructs it to treat the kernel as a NetBSD image. Luckily, the behavior of u-boot in the case of a NetBSD image is generic enough so that things work anyway.
*host %* mkimage -A arm -O netbsd -T kernel -C none -a 80200000 -e 802000e0 -n "FreeBSD" -d _path_to_kernel_/kernel ukernel
You should obtain a ukernel file, that you can stick into the FAT partition of your SD card. Once you get to the u-boot prompt, type in the following commands:
*OMAP3 beagleboard.org #* mmcinit
*OMAP3 beagleboard.org #* fatload mmc 0:1 81000000 ukernel
*OMAP3 beagleboard.org #* bootm 81000000
You should see the kernel traces as well.
Reducing the amount of typing
Instead of typing this each time, it is of course possible to set the bootcmd environment variable whose content u-boot will execute if the boot command is used.
At the U-boot prompt, just type:
OMAP3 beagleboard.org # setenv bootcmd 'mmcinit ; fatload mmc 0:1 81000000 ukernel ; bootm 81000000'
Beware, on some versions of U-boot, spaces are important. Then, save this environment variable to persistent storage so that it's available across reboots by typing:
OMAP3 beagleboard.org # saveenv
Saving Environment to NAND...
Erasing Nand...Writing to Nand... done
Now, and each time you start the board, you only have to type:
OMAP3 beagleboard.org # boot
U-boot also supports automatically executing the content of bootcmd when starting up, but it is really not recommended at this stage of the development process.