[Qemu-devel] [PATCH] scripts/qemu-binfmt-conf.sh: allow clearing of entries

["Alex Bennée" <alex.bennee@linaro.org>]

Currently running the script twice will fail with "sh: echo: I/O
error" as the registration is already complete. Add a new option
--clear to reset the entries to save the user doing it by hand.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 scripts/qemu-binfmt-conf.sh | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/scripts/qemu-binfmt-conf.sh b/scripts/qemu-binfmt-conf.sh
index d7eefda0b8..13ef4713e6 100755
--- a/scripts/qemu-binfmt-conf.sh
+++ b/scripts/qemu-binfmt-conf.sh
@@ -160,7 +160,7 @@ qemu_get_family() {
 usage() {
     cat <<EOF
 Usage: qemu-binfmt-conf.sh [--qemu-path PATH][--debian][--systemd CPU]
-                           [--help][--credential yes|no][--exportdir PATH]
+                           [--help][--clear][--credential yes|no][--exportdir PATH]
 
        Configure binfmt_misc to use qemu interpreter
 
@@ -176,6 +176,7 @@ Usage: qemu-binfmt-conf.sh [--qemu-path PATH][--debian][--systemd CPU]
                      (default: $SYSTEMDDIR or $DEBIANDIR)
        --credential: if yes, credential and security tokens are
                      calculated according to the binary to interpret
+       --clear:      clear existing qemu binfmt registrations
 
     To import templates with update-binfmts, use :
 
@@ -249,6 +250,13 @@ qemu_register_interpreter() {
     qemu_generate_register > /proc/sys/fs/binfmt_misc/register
 }
 
+qemu_clear_interpreter() {
+    if [ -e /proc/sys/fs/binfmt_misc/qemu-$cpu ]; then
+        echo "Removing qemu-$cpu as binfmt interpreter for $cpu"
+        echo -1 > /proc/sys/fs/binfmt_misc/qemu-$cpu
+    fi
+}
+
 qemu_generate_systemd() {
     echo "Setting $qemu as binfmt interpreter for $cpu for systemd-binfmt.service"
     qemu_generate_register > "$EXPORTDIR/qemu-$cpu.conf"
@@ -302,7 +310,7 @@ DEBIANDIR="/usr/share/binfmts"
 QEMU_PATH=/usr/local/bin
 FLAGS=""
 
-options=$(getopt -o ds:Q:e:hc: -l debian,systemd:,qemu-path:,exportdir:,help,credential: -- "$@")
+options=$(getopt -o ds:Q:e:hc: -l debian,systemd:,qemu-path:,exportdir:,help,clear,credential: -- "$@")
 eval set -- "$options"
 
 while true ; do
@@ -354,6 +362,10 @@ while true ; do
             FLAGS=""
         fi
         ;;
+    --clear)
+        shift
+        BINFMT_SET=qemu_clear_interpreter
+        ;;
     *)
         break
         ;;
-- 
2.17.1