Booting the ELF kernel without ubldr on Raspberry Pi

[Sylvain Garrigues]

Hello,

I’d like to boot FreeBSD directly with u-boot, without ubldr, using an image provided by the u-boot mkimage tool. The reason is simple: mkimage can deal with compressed kernels and will therefore speed my boot time. And I want to try it anyway, as it seems possible reading http://bsdcan.org/2008/schedule/attachments/49_2008_uboot_freebsd.pdf <http://bsdcan.org/2008/schedule/attachments/49_2008_uboot_freebsd.pdf> and various other 

Before going there and using an mkimage, I’d like to boot the kernel image just with the same bootelf version provided by the sysutils/u-boot-rpi2 port. It doesn’t display anything and crashes (I think I can see « illegal instruction » just before the board reboots). I don’t understand why, and this is my first question.

Then I looked at the mkimage utility, although we can specify and freebsd kernel type through the -O flag, the bootm command only understands linux and NetBSD. I guess I should use linux there?

Thanks for your help,
Sylvain


PS: FYI, below is:

1/ info about my kernel (I can see the entry point is at 0xc0100100), copied into the fat partition

# readelf -h /root/crochet/work/obj/arm.armv6/root/crochet/src/sys/RPI2/kernel                          
ELF Header:
  Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF32
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           ARM
  Version:                           0x1
  Entry point address:               0xc0100100
  Start of program headers:          52 (bytes into file)
  Start of section headers:          6235080 (bytes into file)
  Flags:                             0x5000202, has entry point, Version5 EABI, <unknown>
  Size of this header:               52 (bytes)
  Size of program headers:           32 (bytes)
  Number of program headers:         6
  Size of section headers:           40 (bytes)
  Number of section headers:         38
  Section header string table index: 35
[root at clad /usr/ports/sysutils/u-boot-rpi2]#  

2/ the interesting part of my include/configs/rpi-common.h from u-boot:

#define CONFIG_EXTRA_ENV_SETTINGS \
        ENV_DEVICE_SETTINGS \
        "loadaddr=0x02000000\0" \
        "Fatboot=" \
          "env exists loaderdev || env set loaderdev ${fatdev}; " \
          "echo Booting from: ${fatdev} ${bootfile}; " \
          "fatload ${fatdev} ${loadaddr} ${bootfile} && bootelf ${loadaddr}; " \
        "\0" \
        "preboot=" \
          "fdt addr 0x100; " \
          "env set bootfile kernel; " \  
          "env set fatdev 'mmc 0'; " \
        "\0"
#undef  CONFIG_BOOTCOMMAND
#define CONFIG_BOOTCOMMAND     "run Fatboot"
#undef  CONFIG_PREBOOT
#define CONFIG_PREBOOT         "run preboot"