GRUB2 configure: Path to /boot/loader not found.

[Luca Renaud]

I installed FreeBSD 11 on a GPT partition: sda7 for / with freebsd-ufs,sda5
for swap with freebsd-swap.I did not use any partition for /boot and the
installer did not ask.My root Partition is this: mounted under /mnt on
Linux.

4 drwxr-xr-x  2 root root 1024 Sep 29 02:44 bin
4 drwxr-xr-x  8 root root 1536 Dec 16 21:35 boot
8 -r--r--r--  1 root root 6197 Sep 29 02:45 COPYRIGHT
4 drwxr-xr-x  2 root root  512 Dec 16 21:20 dev
4 -rw-------  1 root root 4096 Dec 16 21:35 entropy
4 drwxr-xr-x 25 root root 2048 Dec 16 21:35 etc
0 lrwxr-xr-x  1 root root    8 Dec 16 21:33 home -> usr/home
4 drwxr-xr-x  4 root root 1536 Sep 29 02:44 lib
4 drwxr-xr-x  3 root root  512 Dec 16 21:21 libexec
4 drwxr-xr-x  2 root root  512 Sep 29 02:43 media
4 drwxr-xr-x  2 root root  512 Sep 29 02:43 mnt
4 dr-xr-xr-x  2 root root  512 Sep 29 02:43 proc
4 drwxr-xr-x  2 root root 2560 Sep 29 02:44 rescue
4 drwxr-xr-x  2 root root  512 Sep 29 02:45 root
4 drwxr-xr-x  2 root root 2560 Sep 29 02:45 sbin
0 lrwxr-xr-x  1 root root   11 Sep 29 02:45 sys -> usr/src/sys
4 drwxrwxrwt  2 root root  512 Sep 29 02:43 tmp
4 drwxr-xr-x 16 root root  512 Dec 16 21:35 usr
4 drwxr-xr-x 24 root root  512 Sep 29 02:43 var

I configured GRUB2 (manages a multiboot,MultiOSs setup this way: 40_custom.

menuentry "FreeBSD 11" {
                  insmod ufs2
                  set root=(hd0,gpt7)
                  kfreebsd /boot/loader
}

GRUB2 tells me that "file /boot/loader not found" and I really don't know
because it seems everything correct.