Re: [PATCH] [gdbserver] Disable conditional breakpoints on no-hardware-single-step targets

[Pedro Alves <palves at redhat dot com>]

On 05/07/2015 12:45 PM, Antoine Tremblay wrote:

> Just fyi, I'm working on doing this at the moment, my investigation is 
> still incomplete...
> 
> So far I mainly plan to port the arm_get_next code to gdbserver, to 
> accomplish 1. , the code doesn't have so many deps so it should be ok
> 2. by looking at $cpsr
> 3. should be fine as 1 and 2 are done...
> 
> I don't know however yet the best strategy to share the code but I'm 
> guessing I could make the parts that don't have any deps to gdbarch etc 
> in a shared function with gdb/gdbserver... Any pointers on this are 
> welcome...

Yeah, sharing is good.

Maybe adding an abstraction layer object, like:

struct get_next_pc;

struct get_next_pc_ops
{
   void (*read_memory) (struct get_next_pc *self, ...);
   void (*read_register) (struct get_next_pc *self, ...);
   ...
};

struct get_next_pcs
{
   struct get_next_pc_ops *vtable;

   VEC(CORE_ADDR) *result;

   enum bfd_endian byte_order;
   enum bfd_endian byte_order_for_code;
   whatever_type whatever_other_context;
   ...
};

And then both GDB and GDBserver would instantiate
a struct get_next_pc object, like:

struct get_next_pc_ops gdb_get_next_pc_ops = {
   gdb_get_next_pc_read_memory,
   gdb_get_next_pc_read_register,
   ...
}

struct gdb_get_next_pcs
{
  struct get_next_pc base;

  // add whatever other context only gdb needs.
};

int
arm_software_single_step (struct frame_info *frame)
{
  struct gdbarch *gdbarch = get_frame_arch (frame);
  struct gdb_get_next_pc next_pc;
  CORE_ADDR pc;

  next_pc.vtable = gdb_get_next_pc_ops;
  next_pc.byte_order = gdbarch_byte_order (gdbarch);
  next_pc.byte_order_for_code = gdbarch_byte_order_for_code (gdbarch);

  // arm_get_next_pcs is the existing gdb code adjusted to the
  // new interface.
  arm_get_next_pcs (&next_pc);

  // walk result vec (a VEC of CORE_ADDRs) and insert breakpoints.
  // alternatively add a insert_breakpoint callback to struct get_next_pc_ops
  // and insert breakpoints from within arm_get_next_pcs, as currently.
  for (i = 0;
       VEC_iterate (CORE_ADDR, next_pcs.result, i, pc);
       ++i)
    {
       arm_insert_single_step_breakpoint (gdbarch, aspace, pc);
    }

  return 1;
}

Thanks,
Pedro Alves