Fix breakpoint size when stepping over a permanent breakpoint in GDBServer.

When manually stepping over a permanent breakpoint on ARM we need to fetch the
right breakpoint size based on the current instruction set used.

Since this is not encoded in the stop_pc, the instruction mode needs to be
fetched from the CPSR register.

This is done by introducing a new target operation called :
breakpoint_kind_from_current_state.

For other targets that do not need this, breakpoint_kind_from_pc is used.

No regressions, tested on ubuntu 14.04 ARMv7 and x86.
With gdbserver-{native,extended} / { -marm -mthumb }

gdb/gdbserver/ChangeLog:

	* linux-arm-low.c (arm_is_thumb_mode): New function.
	(arm_breakpoint_at): Use arm_is_thumb_mode.
	(arm_breakpoint_kind_from_current_state): New function.
	(struct linux_target_ops) <breakpoint_kind_from_current_state>:
	Initialize.
	* linux-low.c (linux_wait_1): Call breakpoint_kind_from_current_state.
	(linux_breakpoint_kind_from_current_state): New function.
	(struct target_ops <breakpoint_kind_from_current_state>: Initialize.
	* linux-low.h (struct linux_target_ops)
	<breakpoint_kind_from_current_state>: New field.
	* target.h (struct target_ops): Likewise.
	(target_breakpoint_kind_from_current_state): New macro.

1 files changed, 11 insertions, 0 deletions

diff --git a/gdb/gdbserver/target.h b/gdb/gdbserver/target.h
index a09ba2f..d3fcb36 100644
--- a/gdb/gdbserver/target.h
+++ b/gdb/gdbserver/target.h
@@ -457,6 +457,12 @@ struct target_ops
   /* Return the thread's name, or NULL if the target is unable to determine it.
      The returned value must not be freed by the caller.  */
   const char *(*thread_name) (ptid_t thread);
+
+  /* Return the breakpoint kind for this target based on the current
+     processor state (e.g. the current instruction mode on ARM) and the
+     PC.  The PCPTR is adjusted to the real memory location in case a flag
+     (e.g., the Thumb bit on ARM) is present in the PC.  */
+  int (*breakpoint_kind_from_current_state) (CORE_ADDR *pcptr);
 };
 
 extern struct target_ops *the_target;
@@ -644,6 +650,11 @@ int kill_inferior (int);
    ? (*the_target->breakpoint_kind_from_pc) (pcptr) \
    : default_breakpoint_kind_from_pc (pcptr))
 
+#define target_breakpoint_kind_from_current_state(pcptr) \
+  (the_target->breakpoint_kind_from_current_state \
+   ? (*the_target->breakpoint_kind_from_current_state) (pcptr) \
+   : target_breakpoint_kind_from_pc (pcptr))
+
 /* Start non-stop mode, returns 0 on success, -1 on failure.   */
 
 int start_non_stop (int nonstop);