pb-plugin: Implement plugin ABI versioning

If a future update to plugins is not compatbile with the installed
plugin infrastructure, we want to abort the scan / install process.

This change adds an ABI version to the script, as well as version (and
minimum-supported version) to the plugin metadata. This means we can
check before plugin execution.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

diff --git a/utils/pb-plugin b/utils/pb-plugin
index c6c9ef97ccc4dd7f7e02196f03a978c48ce7bc41..f87e5fb0e6f15f2ec9c151704c15529722a3c4d8 100755 (executable)
--- a/utils/pb-plugin
+++ b/utils/pb-plugin
@@ -2,6 +2,7 @@
 
 __dest=/
 __pb_mount_dir=/var/petitboot/mnt/dev/
+plugin_abi=1
 plugin_ext=pb-plugin
 plugin_meta=pb-plugin.conf
 plugin_meta_dir=etc/preboot-plugins/
@@ -62,6 +63,23 @@ plugin_info()
        echo "  (version $PLUGIN_VERSION)"
 }
 
+# How the ABI versioning works:
+#
+#  - This script has an ABI defined ($plugin_abi)
+#
+#  - Plugins have a current ABI number ($PLUGIN_ABI), and a minimum supported
+#    ABI number ($PLUGIN_ABI_MIN).
+#
+#  - A plugin is OK to run if:
+#    - the plugin's ABI matches the script ABI, or
+#    - the plugin's minimum ABI is lower than or equal to the script ABI
+plugin_abi_check()
+{
+       [ -n "$PLUGIN_ABI" ] &&
+               ( [ $PLUGIN_ABI -eq $plugin_abi ] ||
+                 [ $PLUGIN_ABI_MIN -le $plugin_abi ] )
+}
+
 do_wrap()
 {
        local base binary dir
@@ -145,6 +163,7 @@ do_install()
        echo
        sha256sum "$file" | cut -f1 -d' '
        echo
+
        echo "Do you want to install this plugin? (y/N)"
        read resp
 
@@ -169,6 +188,14 @@ do_install()
 
        . $__dest/$plugin_meta_path
 
+       if ! plugin_abi_check
+       then
+               echo "Plugin at $url is incompatible with this firmware," \
+                       "exiting."
+               rm -rf $__dest
+               exit 1
+       fi
+
        for binary in ${PLUGIN_EXECUTABLES}
        do
                __create_wrapper "$__dest" "$binary"
@@ -203,6 +230,8 @@ do_scan_mount()
                (
                        . $__meta_tmp/$plugin_meta_path
 
+                       plugin_abi_check || exit 1
+
                        printf "Plugin found on %s:\n" $dev
                        plugin_info
                        printf "\n"
@@ -210,8 +239,11 @@ do_scan_mount()
                        printf "  $0 run $plugin_path\n"
                        printf "\n"
                )
+               if [ $? = 0 ]
+               then
+                       found=1
+               fi
                rm -rf $__meta_tmp
-               found=1
        done
 }
 
@@ -290,6 +322,8 @@ EOF
        mkdir -p $(dirname $file)
 
        cat <<EOF > $file
+PLUGIN_ABI='$plugin_abi'
+PLUGIN_ABI_MIN='1'
 PLUGIN_VENDOR='$vendorname'
 PLUGIN_VENDOR_ID='$vendorshortname'
 PLUGIN_NAME='$pluginname'
@@ -337,6 +371,15 @@ do_create()
 
        # Sanity check metadata file
        . $meta_file
+       if [ ! -n "$PLUGIN_ABI" ]
+       then
+               echo "error: no PLUGIN_ABI defined in metadata" &>2
+               exit 1
+       fi
+       if [ "$PLUGIN_ABI" != "$plugin_abi" ]
+       then
+               echo "warning: PLUGIN_ABI (=$PLUGIN_ABI) is not $plugin_abi" &>2
+       fi
        if [ ! -n "$PLUGIN_VENDOR" ]
        then
                echo "error: no PLUGIN_VENDOR defined in metadata" &>2
@@ -436,12 +479,23 @@ test_ftp_download()
        cmp -s "$ref" "$tmp"
 }
 
+test_abi_check()
+{
+       (
+               plugin_abi=$1
+               PLUGIN_ABI=$2
+               PLUGIN_ABI_MIN=$3
+               plugin_abi_check
+       )
+}
+
 test_scan()
 {
        __pb_mount_dir="$test_tmpdir/mnt"
        mnt_dir="$__pb_mount_dir/sda"
        mkdir -p $mnt_dir/$plugin_meta_dir
        (
+               echo "PLUGIN_ABI=$plugin_abi"
                echo "PLUGIN_NAME=test"
                echo "PLUGIN_VERSION=1"
                echo "PLUGIN_EXECUTABLES=/bin/sh"
@@ -510,6 +564,7 @@ test_scan_multiple()
        do
                mkdir -p $mnt_dir/$plugin_meta_dir
                (
+                       echo "PLUGIN_ABI=$plugin_abi"
                        echo "PLUGIN_NAME=test-$i"
                        echo "PLUGIN_VERSION=1"
                        echo "PLUGIN_EXECUTABLES=/bin/sh"
@@ -526,6 +581,26 @@ test_scan_multiple()
        grep -q 'test-1' $outfile && grep -q 'test-2' $outfile
 }
 
+test_scan_wrongabi()
+{
+       __pb_mount_dir="$test_tmpdir/mnt"
+       mnt_dir="$__pb_mount_dir/sda"
+       mkdir -p $mnt_dir/$plugin_meta_dir
+       (
+               echo "PLUGIN_ABI=$(($plugin_abi + 1))"
+               echo "PLUGIN_ABI_MIN=$(($plugin_abi + 1))"
+               echo "PLUGIN_NAME=test"
+               echo "PLUGIN_VERSION=1"
+               echo "PLUGIN_EXECUTABLES=/bin/sh"
+       ) > $mnt_dir/$plugin_meta_path
+       (
+               cd $mnt_dir;
+               find -mindepth 1 | cpio -o -Hnewc 2>/dev/null
+       ) | gzip -c > $mnt_dir/test.$plugin_ext
+
+       do_scan | grep -q 'No plugins'
+}
+
 test_empty_scan()
 {
        __pb_mount_dir="$test_tmpdir/mnt"
@@ -590,10 +665,18 @@ do_tests()
        do_test is_url "git+ssh://example.com/path"
        do_test test_http_download
        do_test test_ftp_download
+       do_test ! test_abi_check
+       do_test ! test_abi_check 1
+       do_test test_abi_check 1 1
+       do_test test_abi_check 1 1 1
+       do_test test_abi_check 1 2 0
+       do_test test_abi_check 1 2 1
+       do_test ! test_abi_check 1 2 2
        do_test test_scan
        do_test test_scan_nogzip
        do_test test_scan_nocpio
        do_test test_scan_multiple
+       do_test test_scan_wrongabi
        do_test test_empty_scan
 
        if [ $test_failed = 0 ]