kernel-building error

[mess-mate]

Hi,
An error occurs when building my kernel :(
What does this mean ?? :

linking kernel
umass.o: In function `umass_cam_attach_sim':
umass.o(.text+0x17c7): undefined reference to `cam_simq_alloc'
umass.o(.text+0x1818): undefined reference to `cam_sim_alloc'
umass.o(.text+0x1827): undefined reference to `cam_simq_free'
umass.o(.text+0x1847): undefined reference to `xpt_bus_register'
umass.o: In function `umass_cam_rescan_callback':
umass.o(.text+0x1883): undefined reference to `xpt_free_path'
umass.o: In function `umass_cam_rescan':
umass.o(.text+0x18f5): undefined reference to `xpt_periph'
umass.o(.text+0x1904): undefined reference to `xpt_create_path'
umass.o(.text+0x1920): undefined reference to `xpt_setup_ccb'
umass.o(.text+0x193d): undefined reference to `xpt_action'
umass.o: In function `umass_cam_detach_sim':
umass.o(.text+0x1a2c): undefined reference to `xpt_bus_deregister'
umass.o(.text+0x1a48): undefined reference to `cam_sim_free'
umass.o: In function `umass_cam_action':
umass.o(.text+0x1ebd): undefined reference to `xpt_done'
umass.o: In function `umass_cam_cb':
umass.o(.text+0x202b): undefined reference to `xpt_done'
umass.o: In function `umass_cam_sense_cb':
umass.o(.text+0x2191): undefined reference to `xpt_done'
umass.o: In function `umass_cam_quirk_cb':
umass.o(.text+0x21bb): undefined reference to `xpt_done'
*** Error code 1

Thanks for your help.
mess-mate