[RTEMS Project] #4131: "fdisk DISK_NAME mount" in bdpart-mount.c uses non-existing file system type "msdos"

RTEMS trac trac at rtems.org
Mon Oct 12 11:19:08 UTC 2020

#4131: "fdisk DISK_NAME mount" in bdpart-mount.c uses non-existing file system
type "msdos"
 Reporter:  Frank Kuehndel           |       Owner:  Frank Kühndel
                                     |  <frank.kuehndel@…>
     Type:  defect                   |      Status:  closed
 Priority:  normal                   |   Milestone:  6.1
Component:  shell                    |     Version:
 Severity:  minor                    |  Resolution:  fixed
 Keywords:  fdisk shell bdpart       |  Blocked By:
  mount bdpart-mount.c msdos         |
 Blocking:                           |
Changes (by Frank Kühndel <frank.kuehndel@…>):

 * owner:  (none) => Frank Kühndel <frank.kuehndel@…>
 * status:  assigned => closed
 * resolution:   => fixed


 In [changeset:"a479686c112144119866391ceb21c48be6a3eca9/rtems"
 #!CommitTicketReference repository="rtems"
 shell: Remove not functioning fdisk mount/unmount

 The shell has an 'fdisk' command which has sub-commands 'mount' and
 These two sub-commands have a bug which causes them to be not able
 to mount anything. This proposed patch removes the buggy file
 cpukit/libblock/src/bdpart-mount.c and the mount/unmount commands
 from 'fdisk' as bug fix. The 'fdisk' command itself is not removed.
 The reasons for removing the sub-commands (instead of fixing the issue)

   1) The bug has been introduced on 2010-May-31 with commit
      29e92b090c8bc35745aa5c89231ce806bcb11e57. Since ten years no one
      can use this feature, nor has anybody complained about it.

   2) Besides of the 'fdisk' 'mount' sub-command, the shell has the
      usual 'mount' and 'unmount' commands which can serve as

   3) There are additional minor issues (see further down) which needed to
      be addressed when the file will be kept.

 What follows below is the precise bug description.

 The bug is in function rtems_bdpart_mount() which is only be used
 by the 'fdisk' shell command to mount all partitions of a disk with a
 single command:

 > fdisk DISK_NAME mount
 >         mounts the file system of each partition of the disk
 > fdisk DISK_NAME unmount
 >         unmounts the file system of each partition of the disk

 The whole command does not work because in file
 cpukit/libblock/src/bdpart-mount.c line 103 specifies the file system type
 of each partition to be "msdos". Yet, "msdos" does not exist. The name
 must be "dosfs".

 Beside of this fundamental problem, there are more issues with the code
 in bdpart-mount.c:

   1) The function returns RTEMS_SUCCESSFUL despite the mount always fails.

   2) The reason for errors is not written to the terminal.

   3) The directory '/mnt' is created but not deleted later on (failure or

   3) There is no documentation about this special 'fdisk' feature in the
      RTEMS Shell Guide ('fdisk' is mentioned but its documentation is a
      bit short):

   4) Only "msdos" formatted partitions can be mounted and all partitions
      are mounted read-only. This is hard coded and cannot be changed by
      options. Moreover, there is no information about this to the user of
      the shell (i.e. using 'fdisk' mount requires insider knowledge).

 How to reproduce:

   1) For testing, I use the 'testsuites/samples/fileio.exe' sample with

 > cd rtems
 > env QEMU_AUDIO_DRV="none" qemu-system-arm -net none -nographic \
 > -M realview-pbx-a9 -m 256M -kernel \
 > build/arm/realview_pbx_a9_qemu/testsuites/samples/fileio.exe

   2) Type any key to stop the timer and enter the sample tool.
      Type 's' to enter the shell, login as 'root' with the password
      shown in the terminal.

   3) Type the following shell commands (they create a RAM disk,
      partition it, register it, format it and try to mount it):

 > mkrd
 > fdisk /dev/rda fat32 16 write mbr
 > fdisk /dev/rda register
 > mkdos /dev/rda1
 > fdisk /dev/rda mount

   4) The last line above is the command which fails - without an error
   message. There exists a '/mnt' directory but no '/mnt/rda1' directory
   as it should be:

 > ls -la /mnt

   5) If you change line 103 of 'cpukit/libblock/src/bdpart-mount.c'
      from "msdos" to "dosfs", compile and build the executable and
      re-run the above test, '/mnt/rda1' exists (but the file system
      is mounted read-only).

 Close #4131

Ticket URL: <http://devel.rtems.org/ticket/4131#comment:1>
RTEMS Project <http://www.rtems.org/>
RTEMS Project

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