L4/Fiasco kernel debugger (jdb) and step over command

Hi. I'm trying to debug my program with jdb. (I'm using the old 
L4/Fiasco / L4Env, not the current Fiasco.OC / L4Re). I enabled the 
permanent single step mode (with the S+ command) and a permanent show 
the Thread Control Block (with the t+ command) option. So, I was able to 
single-step with "g" command. Also, I found "jr" (go until return (ret 
or iret) is encountered) and "jb" (go until the next branch instruction, 
like jmp/call/int) commands, but they don't seem to work. When I enter 
them, I see only a single step to the next instruction. Are these two 
commands broken? How do I step over a "call"/"int" instruction?


Thanks in advance,

valery