[archiso] Add support to mount iso in loopback mode.

Add two parameters:

img_dev=/dev/sdNM
   where /dev/sdNM is the device where .iso is located.
img_loop=/path/to/arch.iso
   where /path/to/arch.iso is the full path of the .iso in the device img_dev.

Original idea from Baurzhan Muftakhidinov.

Signed-off-by: Gerardo Exequiel Pozzi <vmlinuz386@yahoo.com.ar>

archiso/Makefile

@@ -10,6 +10,8 @@ install: all
 	install -D -m 644 install/archiso $(DESTDIR)/lib/initcpio/install/archiso
 	install -D -m 644 hooks/archiso_pxe_nbd $(DESTDIR)/lib/initcpio/hooks/archiso_pxe_nbd
 	install -D -m 644 install/archiso_pxe_nbd $(DESTDIR)/lib/initcpio/install/archiso_pxe_nbd
+	install -D -m 644 hooks/archiso_loop_mnt $(DESTDIR)/lib/initcpio/hooks/archiso_loop_mnt
+	install -D -m 644 install/archiso_loop_mnt $(DESTDIR)/lib/initcpio/install/archiso_loop_mnt
 	# install docs and examples
 	install -d -m 755 $(DESTDIR)/usr/share/archiso/
 	cp -r ../configs $(DESTDIR)/usr/share/archiso/configs

archiso/hooks/archiso_loop_mnt

@@ -0,0 +1,33 @@
+# vim: set ft=sh:
+
+run_hook () {
+    if [ -n "${img_dev}" ] && [ -n "${img_loop}" ]; then
+        mount_handler="archiso_loop_mount_handler"
+    fi
+}
+
+archiso_loop_mount_handler () {
+    newroot="${1}"
+
+    while [ ! -b "${img_dev}" ]; do
+        sleep 1
+    done
+
+    msg "::: Setup a loop device from ${img_loop} located at device ${img_dev}"
+    FSTYPE=$(blkid -o value -s TYPE -p ${img_dev} 2> /dev/null)
+    if [ -n "${FSTYPE}" ]; then
+        if mount -r -t "${FSTYPE}" ${img_dev} /img_dev > /dev/null 2>&1; then
+            _dev_loop=$(losetup -f)
+            losetup ${_dev_loop} /img_dev/${img_loop}
+        fi
+    fi
+
+    archiso_mount_handler ${newroot}
+
+    if [ "${copytoram}" = "y" ]; then
+        msg "::: Deataching loop device ${_dev_loop}"
+        losetup -d ${_dev_loop}
+        msg "::: Unmounting ${img_dev}"
+        umount ${img_dev}
+    fi
+}

archiso/install/archiso_loop_mnt

@@ -0,0 +1,18 @@
+# vim: set ft=sh:
+
+install ()
+{
+    MODULES=""
+
+    BINARIES=""
+    FILES=""
+    add_dir /img_dev
+    SCRIPT="archiso_loop_mnt"
+}
+
+help ()
+{
+cat<<HELPEOF
+  This hook loads the necessary modules for boot via loop device.
+HELPEOF
+}

configs/syslinux-iso/mkinitcpio.conf

@@ -2,5 +2,5 @@
 MODULES=""
 BINARIES=""
 FILES=""
-HOOKS="base udev memdisk archiso archiso_pxe_nbd pata scsi sata usb fw pcmcia filesystems usbinput"
+HOOKS="base udev memdisk archiso archiso_pxe_nbd archiso_loop_mnt pata scsi sata usb fw pcmcia filesystems usbinput"
 COMPRESSION="lzma"