Add wrappers for the tools nbdfuse and lklfuse

3 files changed, 211 insertions, 0 deletions

diff --git a/tools/__init__.py b/tools/__init__.py
new file mode 100644
index 0000000..e25ef6f
--- /dev/null
+++ b/tools/__init__.py
@@ -0,0 +1,73 @@
+import logging
+import os
+
+from functools import wraps
+from subprocess import run
+
+__all__ = ["unmount", "rmdir"]
+
+L = logging.getLogger(__name__)
+
+
+def log(func):
+    """Simple decorator for logging function calls."""
+    @wraps(func)
+    def _log(*args, **kwargs):
+        args_repr = [repr(a) for a in args]
+        kwargs_repr = [f"{k}={v!r}" for k, v in kwargs.items()]
+        params = ", ".join(args_repr + kwargs_repr)
+        file_name = os.path.basename(func.__code__.co_filename)
+        file_name = os.path.splitext(file_name)[0]
+        func_name = func.__name__ if file_name == "__init__" \
+            else f"{file_name}.{func.__name__}"
+        L.debug("%s called with %s", func_name, params)
+        try:
+            result = func(*args, **kwargs)
+            L.debug("%s returned %s", func_name, result)
+            return result
+        except Exception as e:
+            L.error("%s raised %r", func_name, e)
+            raise e
+    return _log
+
+
+@log
+def unmount(path):
+    """Unmount a FUSE filesystem using fusermount.
+
+    See also:
+    https://manpages.debian.org/bullseye/fuse/fusermount.1.en.html
+
+    Args:
+        path (str): Path to the mounted FUSE filesystem.
+
+    Returns:
+        True if the command was successful, False otherwise.
+    """
+    cmd = ["fusermount", "-u", path]
+    try:
+        p = run(cmd, capture_output=True, check=False, text=True)
+    except Exception as e:
+        L.error("failed to execute command %s: %r", cmd, e)
+        return False
+
+    return not p.returncode
+
+
+@log
+def rmdir(path):
+    """Remove a directory.
+
+    Args:
+        path (str): Path to directory.
+
+    Returns:
+        True if the command was successful, False otherwise.
+    """
+    try:
+        os.rmdir(path)
+    except OSError as e:
+        L.error("failed to remove directory %s: %r", path, e)
+        return False
+
+    return True
diff --git a/tools/lklfuse.py b/tools/lklfuse.py
new file mode 100644
index 0000000..6982be1
--- /dev/null
+++ b/tools/lklfuse.py
@@ -0,0 +1,75 @@
+import logging
+import os
+import tempfile
+
+from subprocess import Popen, PIPE
+from time import sleep
+from . import log, rmdir
+
+__all__ = ["mount"]
+
+L = logging.getLogger(__name__)
+
+
+@log
+def mount(path, fs_type, part_nr=None):
+    """Mount a RAW image file containing an ext2/ext3/ext4/xfs/btrfs/vfat/ntfs
+    filesystem with read-only support using `lklfuse`.
+
+    Make sure you have built `LKL` from the source code:
+        $ sudo apt install build-essential flex bison bc libfuse-dev \
+            libarchive-dev xfsprogs python git
+        $ git clone https://github.com/lkl/linux.git
+        $ cd linux
+        $ echo "CONFIG_NTFS_FS=y" >> arch/lkl/configs/defconfig
+        $ make -C tools/lkl
+        $ sudo cp tools/lkl/lklfuse /usr/local/bin
+
+    Args:
+        path (str): Path to the RAW image file.
+        fs_type (str): Filesystem type.
+        part_nr (int|str): Partition number.
+
+    Returns:
+        Path to the mount point.
+    """
+    mp = tempfile.mkdtemp()
+
+    opts = f"ro,type={fs_type}"
+    if part_nr is not None:
+        opts += f",part={part_nr}"
+    if fs_type == "xfs":
+        # filesystem will be mounted without running log recovery.
+        # otherwise, the mount will fail.
+        # see also: https://man7.org/linux/man-pages/man5/xfs.5.html
+        opts += ",opts=norecovery"
+    elif fs_type == "ext3" or fs_type == "ext4":
+        # allow mounting dirty ext3 and ext4 filesystems
+        # see also: https://man7.org/linux/man-pages/man5/ext3.5.html
+        # example error message that occurs e.g. when mounting Fedora 26:
+        # JBD2: recovery failed
+        # EXT4-fs (vda): error loading journal
+        opts += ",opts=noload"
+
+    cmd = ["lklfuse", path, mp, "-f", "-o", opts]
+
+    try:
+        p = Popen(cmd, stdout=PIPE, stderr=PIPE, text=True)
+    except Exception as e:
+        L.error("failed to execute command %s: %r", cmd, e)
+        rmdir(mp)
+        return None
+
+    while p.poll() is None:
+        if os.path.ismount(mp):
+            return mp
+        sleep(1)
+
+    ret = p.poll()
+    out, err = p.communicate()
+    out, err = out.strip(), err.strip()
+    L.error("retcode: %d, stdout: %s, stderr: %s", ret, out, err)
+
+    rmdir(mp)
+
+    return None
diff --git a/tools/nbdfuse.py b/tools/nbdfuse.py
new file mode 100644
index 0000000..b7a4997
--- /dev/null
+++ b/tools/nbdfuse.py
@@ -0,0 +1,63 @@
+import logging
+import os
+import tempfile
+
+from subprocess import Popen, PIPE
+from time import sleep
+from . import log, rmdir
+
+__all__ = ["mount"]
+
+L = logging.getLogger(__name__)
+
+
+@log
+def mount(path):
+    """Mount a VMware Virtual Machine Disk (VMDK) file as a RAW image file in
+    the local filesystem with read-only support using `qemu-nbd` + `nbdfuse`.
+
+    See also:
+    https://manpages.debian.org/bullseye/qemu-utils/qemu-nbd.8.en.html
+    https://manpages.debian.org/bullseye/libnbd-bin/nbdfuse.1.en.html
+
+    Make sure you have the following packages installed:
+        $ sudo apt install qemu-utils nbdfuse
+
+    Args:
+        path (str): Path to the VMDK file.
+
+    Returns:
+        Path to the directory containing a single virtual file named `nbd`.
+    """
+    mp = tempfile.mkdtemp()
+    cmd = [
+        "nbdfuse",
+        "--readonly",
+        mp,
+        "--socket-activation",
+        "qemu-nbd",
+        "--read-only",
+        "--format=vmdk",
+        path
+    ]
+
+    try:
+        p = Popen(cmd, stdout=PIPE, stderr=PIPE, text=True)
+    except Exception as e:
+        L.error("failed to execute command %s: %r", cmd, e)
+        rmdir(mp)
+        return ""
+
+    while p.poll() is None:
+        if os.path.ismount(mp):
+            return mp
+        sleep(1)
+
+    ret = p.poll()
+    out, err = p.communicate()
+    out, err = out.strip(), err.strip()
+    L.error("retcode: %d, stdout: %s, stderr: %s", ret, out, err)
+
+    rmdir(mp)
+
+    return ""