Re: [Qemu-devel] [PATCH v3 for 3.0 17/18] docker: perform basic binfmt_misc validation in docker.py

[Fam Zheng]

On Wed, Jul 18, 2018 at 4:02 AM Alex Bennée <address@hidden> wrote:
>
> Setting up binfmt_misc is outside of the scope of the docker.py script
> but we can at least validate it with any given executable so we have a
> more useful error message than the sed line of deboostrap failing
> cryptically.
>
> Signed-off-by: Alex Bennée <address@hidden>
> Reported-by: Richard Henderson <address@hidden>
> ---
>  tests/docker/docker.py | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
>
> diff --git a/tests/docker/docker.py b/tests/docker/docker.py
> index 523f4b95a2..a3f5b0c1b0 100755
> --- a/tests/docker/docker.py
> +++ b/tests/docker/docker.py
> @@ -112,6 +112,31 @@ def _copy_binary_with_libs(src, dest_dir):
>              so_path = os.path.dirname(l)
>              _copy_with_mkdir(l , dest_dir, so_path)
>
> +
> +def _check_binfmt_misc(executable):
> +    """Check binfmt_misc has entry for executable in the right place.
> +
> +    The details of setting up binfmt_misc are outside the scope of
> +    this script but we should at least fail early with a useful
> +    message if it won't work."""
> +
> +    binary = os.path.basename(executable)
> +    binfmt_entry = "/proc/sys/fs/binfmt_misc/%s" % (binary)
> +
> +    if not os.path.exists(binfmt_entry):
> +        print ("No binfmt_misc entry for %s" % (binary))
> +        return False
> +
> +    with open(binfmt_entry) as x: entry = x.read()
> +
> +    qpath = "/usr/bin/%s" % (binary)

Is it intended to hardcode this to /usr/bin? I thought we were more
flexible than that..

Fam

> +    if not re.search("interpreter %s\n" % (qpath), entry):
> +        print ("binfmt_misc for %s does not point to %s" % (binary, qpath))
> +        return False
> +
> +    return True
> +
> +
>  def _read_qemu_dockerfile(img_name):
>      # special case for Debian linux-user images
>      if img_name.startswith("debian") and img_name.endswith("user"):
> @@ -315,6 +340,11 @@ class BuildCommand(SubCommand):
>              # Create a docker context directory for the build
>              docker_dir = tempfile.mkdtemp(prefix="docker_build")
>
> +            # Validate binfmt_misc will work
> +            if args.include_executable:
> +                if not _check_binfmt_misc(args.include_executable):
> +                    return 1
> +
>              # Is there a .pre file to run in the build context?
>              docker_pre = os.path.splitext(args.dockerfile)[0]+".pre"
>              if os.path.exists(docker_pre):
> --
> 2.17.1
>