'f' - Will call oom_kill to kill a memory hog process.
-'g' - Used by kgdb on ppc and sh platforms.
+'g' - Used by kgdb (kernel debugger)
'h' - Will display help (actually any other key than those listed
here will display help. but 'h' is easy to remember :-)
'u' - Will attempt to remount all mounted filesystems read-only.
-'v' - Dumps Voyager SMP processor info to your console.
+'v' - Forcefully restores framebuffer console
+'v' - Causes ETM buffer dump [ARM-specific]
'w' - Dumps tasks that are in uninterruptable (blocked) state.
'x' - Used by xmon interface on ppc/powerpc platforms.
+'y' - Show global CPU Registers [SPARC-64 specific]
+
'z' - Dump the ftrace buffer
'0'-'9' - Sets the console log level, controlling which kernel messages