range stepping: gdbserver (x86 GNU/Linux)

This patch adds support for range stepping to GDBserver, teaching it
about vCont;r.

It'd be easy to enable this for all hardware single-step targets
without needing the linux_target_ops hook, however, at least PPC needs
special care, due to the fact that PPC atomic sequences can't be
hardware single-stepped through, a thing which GDBserver doesn't know
about.  So this leaves the support limited to x86/x86_64.

gdb/
2013-05-23  Pedro Alves  <palves@redhat.com>

	* NEWS: Mention GDBserver range stepping support.

gdb/gdbserver/
2013-05-23  Yao Qi  <yao@codesourcery.com>
	    Pedro Alves  <palves@redhat.com>

	* linux-low.c (lwp_in_step_range): New function.
	(linux_wait_1): If the thread was range stepping and stopped
	outside the stepping range, report the stop to GDB.  Otherwise,
	continue stepping.  Add range stepping debug output.
	(linux_set_resume_request): Copy the step range from the resume
	request to the lwp.
	(linux_supports_range_stepping): New.
	(linux_target_ops) <supports_range_stepping>: Set to
	linux_supports_range_stepping.
	* linux-low.h (struct linux_target_ops)
	<supports_range_stepping>: New field.
	(struct lwp_info) <step_range_start, step_range_end>: New fields.
	* linux-x86-low.c (x86_supports_range_stepping): New.
	(the_low_target) <supports_range_stepping>: Set to
	x86_supports_range_stepping.
	* server.c (handle_v_cont): Handle 'r' action.
	(handle_v_requests): Append ";r" if the target supports range
	stepping.
	* target.h (struct thread_resume) <step_range_start,
	step_range_end>: New fields.
	(struct target_ops) <supports_range_stepping>:
	New field.
	(target_supports_range_stepping): New macro.

1 files changed, 15 insertions, 0 deletions

diff --git a/gdb/gdbserver/target.h b/gdb/gdbserver/target.h
index f257459..c57cb40 100644
--- a/gdb/gdbserver/target.h
+++ b/gdb/gdbserver/target.h
@@ -57,6 +57,15 @@ struct thread_resume
      linux; SuspendThread on win32).  This is a host signal value (not
      enum gdb_signal).  */
   int sig;
+
+  /* Range to single step within.  Valid only iff KIND is resume_step.
+
+     Single-step once, and then continuing stepping as long as the
+     thread stops in this range.  (If the range is empty
+     [STEP_RANGE_START == STEP_RANGE_END], then this is a single-step
+     request.)  */
+  CORE_ADDR step_range_start;	/* Inclusive */
+  CORE_ADDR step_range_end;	/* Exclusive */
 };
 
 /* Generally, what has the program done?  */
@@ -414,6 +423,8 @@ struct target_ops
      to break a cyclic dependency.  */
   void (*read_btrace) (struct btrace_target_info *, struct buffer *, int type);
 
+  /* Return true if target supports range stepping.  */
+  int (*supports_range_stepping) (void);
 };
 
 extern struct target_ops *the_target;
@@ -549,6 +560,10 @@ int kill_inferior (int);
 #define target_read_btrace(tinfo, buffer, type)	\
   (*the_target->read_btrace) (tinfo, buffer, type)
 
+#define target_supports_range_stepping() \
+  (the_target->supports_range_stepping ? \
+   (*the_target->supports_range_stepping) () : 0)
+
 /* Start non-stop mode, returns 0 on success, -1 on failure.   */
 
 int start_non_stop (int nonstop);