macosx (darwin) fail to boot from Grub2

[danjde]

Hi friends,
I've just installed successifully Ubuntu 14.04 on iMac 9.1 (Darwin).

The partitions are so suddivided:


|-EFI-FAT32-|---MAC-HFS+---|--/BOOT-EXT4--|----/ROOT-EXT4----|----/HOME-REISERFS-----|---SWAP---|


On sda is installed rEFIT.
Grub2 is installed on sda3 (/BOOT)

Linux boot correctly from Grub2, MAC not (only from rEFIT). Booting 
from Grub2 MAC, it does't found the system partition.


Here the Grub2 (macosx) entry:


menuentry 'Mac OS X (32 bit) (su /dev/sda2)' --class osx --class darwin 
--class os $menuentry_id_option 'osprober-xnu-32-86296317cf88a9f9'  {
        insmod part_gpt
        insmod hfsplus
        set root='hd0,gpt2'
        if [ x$feature_platform_search_hint = xy ]; then
          search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt2 
--hint-efi=hd0,gpt2 --hint-baremetal=ahci0,gpt2  86296317cf88a9f9
        else
          search --no-floppy --fs-uuid --set=root 86296317cf88a9f9
        fi
        load_video
        set do_resume=0
        if [ /var/vm/sleepimage -nt10 / ]; then
           if xnu_resume /var/vm/sleepimage; then
             set do_resume=1
           fi
        fi
        if [ $do_resume = 0 ]; then
           xnu_uuid 86296317cf88a9f9 uuid
           if [ -f /Extra/DSDT.aml ]; then
              acpi -e /Extra/DSDT.aml
           fi
           if [ /kernelcache -nt /System/Library/Extensions ]; then
              xnu_kernel /kernelcache boot-uuid=${uuid} rd=*uuid
           else
              xnu_kernel /mach_kernel boot-uuid=${uuid} rd=*uuid
              if [ /System/Library/Extensions.mkext -nt 
/System/Library/Extensions ]; then
                xnu_mkext /System/Library/Extensions.mkext
              else
                xnu_kextdir /System/Library/Extensions
              fi
           fi
           if [ -f /Extra/Extensions.mkext ]; then
              xnu_mkext /Extra/Extensions.mkext
           fi
           if [ -d /Extra/Extensions ]; then
              xnu_kextdir /Extra/Extensions
           fi
           if [ -f /Extra/devprop.bin ]; then
              xnu_devprop_load /Extra/devprop.bin
           fi
           if [ -f /Extra/splash.jpg ]; then
              insmod jpeg
              xnu_splash /Extra/splash.jpg
           fi
           if [ -f /Extra/splash.png ]; then
              insmod png
              xnu_splash /Extra/splash.png
           fi
           if [ -f /Extra/splash.tga ]; then
              insmod tga
              xnu_splash /Extra/splash.tga
           fi
        fi
}



This the two last kernel entry, before it hang:

Waiting for boot volume with UUID 5105a848-08a7-3b8d-aca6-6bb4a78ba26b
Waiting on <dict ID="0"><key>IOProviderClass</key><string 
ID="1">IOResources</string><key>IOResourceMatch</key><string 
ID="2">boot-uuid-media</string></dict>



What do you suggest for make MAC bootable from Grub2?

many many thanks!