Unable to boot 64bit hello

Hi,

I tried booting a 64bit hello world program on L4/Fiasco but that fails 
with a region overlap:

=============================================
xc: info: VIRTUAL MEMORY ARRANGEMENT:
   Loader:        0000000000100000->000000000019dd88
   TOTAL:         0000000000000000->000000007f800000
   ENTRY ADDRESS: 0000000000100000
xc: info: PHYSICAL MEMORY ALLOCATION:
   4KB PAGES: 0x0000000000000200
   2MB PAGES: 0x00000000000003fb
   1GB PAGES: 0x0000000000000000
Daemon running with PID 9320 net0: 00:16:3e:72:79:e5 using rtl8139 on 
PCI00:04.0 (open)
   [Link:up, TX:0 TXE:0 RX:0 RXE:0]
DHCP (net0 00:16:3e:72:79:e5)... ok
net0: 192.168.178.200/255.255.255.0 gw 192.168.178.54
Booting from PXE menu
boot
PXEBS (net0 type 128).... ok
Next server: 192.168.178.54
Filename: pxeboot.0
tftp://192.168.178.54/pxeboot.0... ok

L4 Bootstrapper
   Build: #7 Sun Jun  9 16:51:46 CEST 2013, x86-64, 4.6.3
   RAM: 0000000000000000 - 000000000009a7ff: 618kB
   RAM: 0000000000100000 - 000000007f7b9fff: 2087656kB
   Total RAM: 2039MB
   New region for list regions:        [   20d000,    4c62c9] { 2b92ca} 
Root   Module
   overlaps with:                 [   2d0080,    2e45c7] {    14548} 
Boot   bootstrap
Regions of list 'regions'
     [        0,       fff] {     1000} Arch   BIOS
     [    e0000,     fffff] {    20000} Arch   BIOS
     [   106000,    1a646f] {    a0470} Root   Module
     [   1a7000,    20c9bd] {    659be} Root   Module
     [   2d0080,    2e45c7] {    14548} Boot   bootstrap
     [  1013000,   10a8fff] {    96000} Boot   bootstrap-ptab64
     [ fc000000,  ffffffff] {  4000000} Arch   BIOS
region overlap

Key press reboots...
=============================================

Everything works for 32bit. I took a look at 
bootstrap/server/src/startup.cc. I verified that modaddr is correctly 
passed to boostrap in both cases (32 and 64bit; it is 0x2000000 
everytime). It appears that the failure happens in the call to 
add_boot_modules_region():

   /* we're just a GRUB-booted kernel! */
   add_boot_modules_region(mbi);

   if (_mod_addr)
     move_modules(mbi, _mod_addr);

I do not fully understand all this code but to me this looks like a 
logic error: first the move should happen to honor "-modaddr" and only 
then the overlap check should be done.

Here is the output for 32bit:
=============================================
L4 Bootstrapper
   Build: #3 Sun Jun  9 16:55:38 CEST 2013, x86-32, 4.6.3
   RAM: 0000000000000000 - 000000000009a7ff: 618kB
   RAM: 0000000000100000 - 000000007f7b9fff: 2087656kB
   Total RAM: 2039MB
   Moving up to 7 modules behind 2000000
   moving module 00 { 139000-1ba783 } -> { 2829000-28aa783 } [530308]
   moving module 01 { 1bb000-21015e } -> { 28ab000-290015e } [348511]
   moving module 02 { 2e5000-51f51c } -> { 2901000-2b3b51c } [2336029]
   moving module 03 { 520000-762e3b } -> { 2000000-2242e3b } [2371132]
   moving module 04 { 763000-8880c6 } -> { 2243000-23680c6 } [1200327]
   moving module 05 { 211000-211080 } -> { 2369000-2369080 } [129]
   moving module 06 { 889000-9616a6 } -> { 236a000-24426a6 } [886439]
   Scanning /fiasco -serial -serial_esc -comspeed 115200 -comport 1 -nokdb
   Scanning /sigma0
   Scanning /moe rom/hello.lua
   Bootloader MMAP:
     [        0,     9a800) RAM (1)
     [    e0000,    100000) reserved (2)
     [   100000,  7f7ba000) RAM (1)
     [ fc000000, 100000000) reserved (2)
   Relocated mbi to [0x2e0000-0x2e043f]
   Loading /fiasco
   Loading /sigma0
   Loading /moe
   find kernel info page...
   found kernel info page at 0x400000
...
=============================================

Since the module addresses are also different between the two version 
this might also be an issue with the linker scripts (and thus just luck 
that the 32bit version boots), I would guess. I am using a Xen VM for 
testing.
Any help would be appreciated.

Thanks,
Daniel