problem debugging assembler functions

[Vladimir Prus]

Hello,
I'm trying to port gdb to a new architecture (with it's own compiler), and
run into problems with assembler functions. I can successfully step into
an assembler function, but when I run "step", instead of moving to the 
next instruction, gdb sets breakpoint at return address and continues.
Looking at the code, I see this (in infrun.c)

Line 2285:

 if (frame_id_eq (frame_unwind_id (get_current_frame ()), step_frame_id))
 {
     ......
 }

Line 2428:

 if (step_over_calls == STEP_OVER_UNDEBUGGABLE
      && ecs->stop_func_name == NULL)
  {
       /* The inferior just stepped into, or returned to, an
         undebuggable function (where there is no symbol, not even a
         minimal symbol, corresponding to the address where the
         inferior stopped). 
        */

        ........

        insert_step_resume_breakpoint_at_frame (
             get_prev_frame (get_current_frame ()));  
  }


The condition is the second code block is taken and breakpoint is indeed
set. I have two questions:

1. Is "just stepped into ... function" comment accurate? I think that all
cases of steppin into function are handled by the previous

 if (frame_id_eq (frame_unwind_id (get_current_frame ()), step_frame_id)) {}

condition, and all code paths inside that condition end with return. So, the
second code block is not executed when we've just stepped into a function.
Is the code intended to handle only the case when we've *returned* to
undebuggable function?

2. In my case, no function names for assembler modules are present in debug
info, but line information is there, so the function is debuggable. Is
there a way to check of line info in condition, not for function name?

Thanks in advance,
Volodya