Re: [Qemu-devel] [PATCH v4 8/10] qemu-binfmt-conf.sh: add option --clear

[Laurent Vivier]

On 11/03/2019 11:31, Unai Martinez-Corral wrote:
> This is a partial implementation.
> 
> Allows to remove a single or a list of already registered binfmt
> interpreters. Valid values are those in qemu_target_list.
> If TARGETS is empty, all the existing 'qemu-*' interpreters are
> removed.
> 
> This is partial because 'debian' and 'systemd' configurations are not
> supported. The script will exit with error 'option clear not
> implemented for this mode yet'.
> 
> Removal is done by printing '-1' as explained at:
> https://www.kernel.org/doc/Documentation/admin-guide/binfmt-misc.rst
> 
> Signed-off-by: Unai Martinez-Corral <address@hidden>
> ---
>  scripts/qemu-binfmt-conf.sh | 41 ++++++++++++++++++++++++++++++++++---
>  1 file changed, 38 insertions(+), 3 deletions(-)
> 
> diff --git a/scripts/qemu-binfmt-conf.sh b/scripts/qemu-binfmt-conf.sh
> index fde78517ff..07d1ee1f04 100755
> --- a/scripts/qemu-binfmt-conf.sh
> +++ b/scripts/qemu-binfmt-conf.sh
> @@ -196,7 +196,7 @@ Options and associated environment variables:
> 
>  Argument             Env-variable     Description
>  TARGETS              QEMU_TARGETS     A single arch name or a list of them 
> (see all names below);
> -                                      if empty, configure all known targets;
> +                                      if empty, configure/clear all known 
> targets;
>                                        if 'NONE', no interpreter is 
> configured.
>  -h|--help                             display this usage
>  -Q|--path PATH:      QEMU_PATH        set path to qemu interpreter(s)
> @@ -206,9 +206,10 @@ TARGETS              QEMU_TARGETS     A single arch name 
> or a list of them (see
>                                        systemd-binfmt.service; environment 
> variable HOST_ARCH
>                                        allows to override 'uname' to generate 
> configuration files
>                                        for a different architecture than the 
> current one.
> -
>  -e|--exportdir PATH: DEBIANDIR        define where to write configuration 
> files
>                       SYSTEMDDIR
> +-c|--clear:          QEMU_CLEAR       (yes) remove registered interpreters 
> for target TARGETS;
> +                                      then exit.
>  -c|--credential:     QEMU_CREDENTIAL  (yes) credential and security tokens 
> are calculated according
>                                        to the binary to interpret
>  -p|--persistent:     QEMU_PERSISTENT  (yes) load the interpreter and keep it 
> in memory; all future
> @@ -336,6 +337,25 @@ qemu_set_binfmts() {
>      done
>  }
> 
> +qemu_clear_notimplemented() {
> +    echo "ERROR: option clear not implemented for this mode yet" 1>&2
> +    usage
> +    exit 1
> +}
> +
> +qemu_clear_interpreter() {
> +    names='qemu-*'
> +    if [ $# -ne 0 ] ; then
> +        qemu_check_target_list $1
> +        unset names pre
> +        for t in $checked_target_list ; do
> +            names="${names}${pre}qemu-$t"
> +            pre=' -o -name '
> +        done
> +    fi
> +    find /proc/sys/fs/binfmt_misc/ -type f -name $names -exec sh -c 'printf 
> %s -1 > {}' \;

The qemu-* will be expanded here if you have a qemu-XXX in the current
directory. You must use "$names".

But:

To remove all, you can do:
sh -c 'printf %s -1 > /proc/sys/fs/binfmt_misc/status'

so something like

if [ $# -eq 0 ] ; then
  sh -c 'printf %s -1 > /proc/sys/fs/binfmt_misc/status
fi
qemu_check_target_list $1
for t in $checked_target_list ; do
   sh -c 'printf %s -1 > /proc/sys/fs/binfmt_misc/qemu-$t'
done

But I think you should also taking care of the suffix.

> +}
> +
>  CHECK=qemu_check_bintfmt_misc
>  BINFMT_SET=qemu_register_interpreter
> 
> @@ -347,12 +367,16 @@ QEMU_PATH="${QEMU_PATH:-/usr/local/bin}"
>  QEMU_SUFFIX="${QEMU_SUFFIX:-}"
>  QEMU_CREDENTIAL="${QEMU_CREDENTIAL:-no}"
>  QEMU_PERSISTENT="${QEMU_PERSISTENT:-no}"
> +QEMU_CLEAR="${QEMU_CLEAR:-no}"
> 
> -options=$(getopt -o dsQ:S:e:hcp -l 
> debian,systemd,path:,suffix:,exportdir:,help,credential,persistent -- "$@")
> +options=$(getopt -o cdsQ:S:e:hcp -l 
> clear,debian,systemd,path:,suffix:,exportdir:,help,credential,persistent -- 
> "$@")
>  eval set -- "$options"
> 
>  while true ; do
>      case "$1" in
> +    -c|--clear)
> +        QEMU_CLEAR="yes"
> +        ;;
>      -d|--debian)
>          CHECK=qemu_check_debian
>          BINFMT_SET=qemu_generate_debian
> @@ -395,4 +419,15 @@ done
>  shift
> 
>  $CHECK
> +
> +if [ "x$QEMU_CLEAR" = "xyes" ] ; then
> +  case "$BINFMT_SET" in
> +    *debian)  BINFMT_CLEAR=qemu_clear_notimplemented ;;
> +    *systemd) BINFMT_CLEAR=qemu_clear_notimplemented ;;
> +    *)        BINFMT_CLEAR=qemu_clear_interpreter
> +  esac

Put this in the previous case for decoding options, please.

> +  $BINFMT_CLEAR "$@"
> +  exit
> +fi
> +
>  qemu_set_binfmts "$@"
> --
> 2.21.0
>