#!/bin/sh

setxkbmap us -option        # clean slate
xkbcomp $DISPLAY out.xkb    # output current keymap
xkbcomp out.xkb $DISPLAY    # work with xkbcomp-produced keymap
xkbcomp $DISPLAY out.xkb    # remove some meaningless diff

patch out.xkb -o patched.xkb << 'EOF'
--- out.xkb	2014-05-16 17:28:18.000000000 +0300
+++ patched.xkb	2014-05-16 17:31:29.000000000 +0300
@@ -590,6 +590,16 @@
         level_name[Level3]= "Alt Base";
         level_name[Level4]= "Alt Number";
     };
+    type "CTRL+ALT_ACTUALLY" {
+        modifiers= Control+Alt;
+        map[Control]= Level2;
+        map[Alt]= Level3;
+        map[Control+Alt]= Level4;
+        level_name[Level1]= "Base";
+        level_name[Level2]= "Ctrl";
+        level_name[Level3]= "Alt";
+        level_name[Level4]= "Ctrl+Alt";
+    };
 };
 
 xkb_compatibility "complete" {
@@ -1322,7 +1332,12 @@
     };
     key <LNFD> {         [        Linefeed ] };
     key <HOME> {         [            Home ] };
-    key   <UP> {         [              Up ] };
+    key   <UP> {
+        type= "CTRL+ALT_ACTUALLY",
+        repeat= Yes,
+        symbols[Group1]= [              Up,              Up,           Prior,            Home ],
+        actions[Group1]= [ NoAction(), NoAction(), RedirectKey(key=<PGUP>,clearMods= Alt), RedirectKey(key=<HOME>,clearMods= Control+Alt) ]
+    };
     key <PGUP> {         [           Prior ] };
     key <LEFT> {         [            Left ] };
     key <RGHT> {         [           Right ] };
EOF

xkbcomp patched.xkb $DISPLAY
xkbcomp $DISPLAY out2.xkb

diff -u patched.xkb out2.xkb # does this show something?