Cannot insert breakpoint -1.

["Anmol P. Paralkar" <anmol@freescale.com>]

Hello,

  Is there a reason why GDB will try to set a breakpoint (breakpoint number: -1) at
  the entry point address on a 'c', after a 'target remote'? (I am using a GDB stub
  at the remote end that resides in a hypervisor upon which guest OS'es run).

  I am using gdb-6.8.50.20090717; but, I suppose that this is general GDB behaviour.

--------------------------------------------------------------------------------
  (gdb) target remote :12007
Remote debugging using :12007
warning: Loadable segment "cpu0_heap_stack" outside of ELF segments
warning: Loadable segment "cpu1_heap_stack" outside of ELF segments
warning: Loadable segment "cpu2_heap_stack" outside of ELF segments
warning: Loadable segment "cpu3_heap_stack" outside of ELF segments
warning: Loadable segment "cpu4_heap_stack" outside of ELF segments
warning: Loadable segment "cpu5_heap_stack" outside of ELF segments
warning: Loadable segment "cpu6_heap_stack" outside of ELF segments
warning: Loadable segment ".stats_heap" outside of ELF segments
warning: Loadable segment ".dpa_mem" outside of ELF segments
0x0013c880 in ?? ()
(gdb) p $pc
$1 = (void (*)()) 0x13c880
(gdb) c
Continuing.
Warning:
Cannot insert breakpoint -1.
Error accessing memory address 0x110000: Unknown error 18446744073709551615.
--------------------------------------------------------------------------------

  (The entry point is likely not mapped into the TLB at that stage and so it is
  really a visible problem, else it just does this silently without it getting
  any attention).

  I tried to work around the issue by using set remote-<name>-packet, where <name>
  equalled software-breakpoint - but that does not work (it did not send a Z0, but
  sent an X packet instead (verified with an earlier GDB compiled with tracing on)):

--------------------------------------------------------------------------------
(gdb) c
Continuing.
^C
Program received signal SIGTRAP, Trace/breakpoint trap.
0x0013c888 in ?? ()
(gdb) c
Continuing.
Warning:
Cannot insert breakpoint -1.
Error accessing memory address 0x110000: Input/output error.
--------------------------------------------------------------------------------

  I then also re-tried with <name> equal to binary-download - but that does not work
  (it did not send the X, but sent an M packet instead):

--------------------------------------------------------------------------------
(gdb) c
Continuing.
^C
Program received signal SIGTRAP, Trace/breakpoint trap.
Cannot remove breakpoints because program is no longer writable.
Further execution is probably impossible.
0x0013c880 in ?? ()
(gdb) 
--------------------------------------------------------------------------------

  Please could someone kindly shed light on this GDB behaviour?

  Thank you.

Anmol.