Problem booting FreeBSD from cboot FreeBSD from cdrom using grubdrom using grub

[Tony]

Hi,
  I'm trying to make an iso image that will boot FreeBSD using GRUB boot 
loader.
  Grub will boot /boot/loader and the loader will boot /boot/kernel. It 
goes well on my disk, but when I try to make a livecd, it fails. I spend 
some time figuring out that /boot/loader does not probe cd it self, it 
depends on boot2 to tell him which cd to boot from. So I did some hack 
on /boot/loader. Bellow is the diff:
*** sys/boot/i386/loader/main.c.bak     Sun Dec 11 19:32:29 2005
--- sys/boot/i386/loader/main.c Sun Dec 11 22:04:29 2005
***************
*** 228,235 ****
      if ((new_currdev.d_type == biosdisk.dv_type) &&
        ((new_currdev.d_kind.biosdisk.unit = bd_bios2unit(biosdev)) == 
-1)) {
        printf("Can't work out which disk we are booting from.\n"
!              "Guessed BIOS device 0x%x not found by probes, defaulting 
to disk0:\n", biosdev);
!       new_currdev.d_kind.biosdisk.unit = 0;
      }
      env_setenv("currdev", EV_VOLATILE, i386_fmtdev(&new_currdev),
               i386_setcurrdev, env_nounset);
--- 228,238 ----
      if ((new_currdev.d_type == biosdisk.dv_type) &&
        ((new_currdev.d_kind.biosdisk.unit = bd_bios2unit(biosdev)) == 
-1)) {
        printf("Can't work out which disk we are booting from.\n"
!              "Guessed BIOS device 0x%x not found by probes, defaulting 
to cd0(%d):\n", biosdev, biosdev);
! bc_add(biosdev);
!           new_currdev.d_type = bioscd.dv_type;
!           new_currdev.d_dev = &bioscd;
!           new_currdev.d_kind.bioscd.unit = bc_bios2unit(biosdev);
      }
      env_setenv("currdev", EV_VOLATILE, i386_fmtdev(&new_currdev),
               i386_setcurrdev, env_nounset);

Then the kernel starts, but when the kernel try to mount the root fs, it 
stops. I have the follow line in my /etc/fstab
/dev/acd0c              /               cd9660  ro          0       0

I am stranded. Can anyone help?  I'm using FreeBSD 5.4

thanks
Tony