Exception during QNX6 mount of images with different block size or sector size

[masto-pn]

Exception during QNX6 mount of images with different block size or sector size

I experience exceptions during mounting of QNX6 images that presumably use a different block size or sector size than defined in the qnx6 kaitaistruct parser definition.

Reproduce

To reproduce, I've created a minimal image on a live QNX as follows:

# uname -a
QNX localhost 7.1.0S 2024/11/01-14:27:36EDT  aarch64le
# touch /tmp/image.qnx6
# mkqnx6fs -b 4096 -n 1024 /tmp/image.qnx6

The generated image is attached.

To mount this image, I've simply installed the project as described in the README.md and mounted it as follows:

$ python3 -m venv venv
$ source ./venv/bin/activate
$ pip install .
$ python3 -m qnxmount qnx6 /tmp/image.qnx6 /tmp/mountpoint/
2026-02-05 13:21:46,947 — qnxmount — INFO — Logging started
2026-02-05 13:21:46,947 — qnxmount — INFO — Python version: 3.13.11 (main, Dec  8 2025, 11:43:54) [GCC 15.2.0]
2026-02-05 13:21:46,947 — qnxmount — INFO — Script started by me on ac10
2026-02-05 13:21:46,947 — qnxmount — INFO — Called with sys.argv:
 /home/me/qnxmount/qnxmount/__main__.py qnx6 /tmp/image.qnx6 /tmp/mountpoint/
2026-02-05 13:21:46,961 — qnxmount — INFO — Current qnxmount version: 0.1.9
2026-02-05 13:21:46,961 — qnxmount — INFO — Selected mounter type: qnx6
2026-02-05 13:21:46,961 — qnxmount — INFO — Mounting image /tmp/image.qnx6 on mount point /tmp/mountpoint
Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/home/me/qnxmount/qnxmount/__main__.py", line 58, in <module>
    sys.exit(mount(args))
             ~~~~~^^^^^^
  File "/home/me/qnxmount/qnxmount/__main__.py", line 18, in mount
    qnx6.mount(args.image, args.mount_point, args.offset)
    ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/me/qnxmount/qnxmount/qnx6/mount.py", line 132, in mount
    qnx6 = FuseQNX6(stream)
  File "/home/me/qnxmount/qnxmount/qnx6/mount.py", line 23, in __init__
    self.qnx6fs = QNX6FS(stream)
                  ~~~~~~^^^^^^^^
  File "/home/me/qnxmount/qnxmount/qnx6/interface.py", line 29, in __init__
    self.check_superblock_crc()
    ~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/home/me/qnxmount/qnxmount/qnx6/interface.py", line 209, in check_superblock_crc
    "object": self.parser.qnx6_bootblock.superblock0,
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/me/qnxmount/qnxmount/qnx6/parser.py", line 218, in superblock0
    self._m_superblock0 = Parser.Superblock(io, self, self._root)
                          ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
  File "/home/me/qnxmount/qnxmount/qnx6/parser.py", line 79, in __init__
    self._read()
    ~~~~~~~~~~^^
  File "/home/me/qnxmount/qnxmount/qnx6/parser.py", line 84, in _read
    raise kaitaistruct.ValidationNotEqualError(b"\x22\x11\x19\x68", self.magic, self._io, u"/types/superblock/seq/0")
kaitaistruct.ValidationNotEqualError: /types/superblock/seq/0: at pos 1028: validation failed: not equal, expected b'"\x11\x19h', but got b'\x00f\xd3\xe0'

Hot Fix

When I change the constant 512 in the instances part of the qnx6/parser.ksy with 4096 as follows:

(venv) me@workspace:~/qnxmount/qnxmount/qnx6$ git diff
diff --git a/qnxmount/qnx6/parser.ksy b/qnxmount/qnx6/parser.ksy
index f54cd5d..04ec090 100644
--- a/qnxmount/qnx6/parser.ksy
+++ b/qnxmount/qnx6/parser.ksy
@@ -23,19 +23,19 @@ types:
     instances:
       superblock0:
         io: _root._io
-        pos: sblk0*512
+        pos: sblk0*4096
         type: superblock
       superblock1:
         io: _root._io
-        pos: sblk1*512
+        pos: sblk1*4096
         type: superblock
       superblock0_raw:
         io: _root._io
-        pos: sblk0*512
+        pos: sblk0*4096
         size: 512
       superblock1_raw:
         io: _root._io
-        pos: sblk1*512
+        pos: sblk1*4096
         size: 512

   superblock:

and regenerate the parser.py code, this image can be mounted successfully.

However, I currently don't understand the QNX6 FS and kaitaistruct well enough to come up with a fix that works for all images, and I also currently don't understand what the constant 512 actually refers to.

Attachments

A minimal reproducer Image that triggers the exception is attached.

image.zip