[PATCH RFC] Make lin-lwp.c functions use target vectors, 3rd try

[John S. Kallal <jskallal at home dot com>]

Hi Mark,

	Here is my revised patch.  
	
	Sorry about the blank mail message.  I send it in error. 
	I need to get some sleep.

	This patch comes from my work trying to get Linux threaded
	debugging working through GDBSERVER.  As a start the following
	patch somewhat makes the routines in lin-lwp.c work through 
	the target stack.  However even with this patch, the lin-lwp.c 
	code still does many system calls and otherwise bypasses the 
	target vectors.

	How am I not following the coding standards?

	Am I coding this change correctly?  
	
	Is this change, the correct thing to do?

	Whould it be better to place the lin-lwp target 
	into the target stack at some new stratum?  Read
	http://sources.redhat.com/ml/gdb/2001-05/msg00302.html.

	Is it even practical to do threaded debugging 
	Linux to Linux via GDBSERVER, without doing major 
	changes to the GDB remote serial protocal and/or 
	GDBSERVER?  I think it can be done but some of 
	the remote serial command may not be as abstract 
	as we would desire.  
	

2001-05-22  John S. Kallal  <jskallal@home.com>

	* lin-lwp.c (get_target_below) : New function to get the current
	target at the process_stratum.

	* lin-lwp.c (find_target_stratum) : New function. This function 
	acts as a helper function to get_target_below.

	* lin-lwp.c (lin_lwp_attach) : Change code to call target 
	function via target vector.  (lin_lwp_attach) : Ditto.
	(lin_lwp_detach) : Ditto. (resume_callback) : Ditto.
	(lin_lwp_resume) : Ditto. (lin_lwp_wait) : Ditto at three places. 
	(lin_lwp_kill) : Ditto.  (lin_lwp_create_inferior) : Ditto.
	(lin_lwp_mourn_inferio) : Ditto. (lin_lwp_fetch_registers) :
	Ditto. (lin_lwp_store_registers) : Ditto 
	(lin_lwp_xfer_memory) : Ditto.  
	* lin-lwp.c : Disable reference to external struct child_ops.
	
--- ../gdb+dejagnu-20010518-org/gdb/lin-lwp.c	Tue May 22 17:23:22 2001
+++ gdb/lin-lwp.c	Tue May 22 13:48:47 2001
@@ -118,7 +118,9 @@ ptid_t trap_ptid;
 static struct target_ops lin_lwp_ops;
 
 /* The standard child operations.  */
+#if 0
 extern struct target_ops child_ops;
+#endif
 
 /* Since we cannot wait (in lin_lwp_wait) for the initial process and
    any cloned processes with a single call to waitpid, we have to use
@@ -144,6 +146,7 @@ static sigset_t blocked_mask;
 
 /* Prototypes for local functions.  */
 static int stop_wait_callback (struct lwp_info *lp, void *data);
+static struct target_ops *get_target_below (void);
 
 
 /* Initialize the list of LWPs.  Note that this module, contrary to
@@ -334,10 +337,14 @@ static void
 lin_lwp_attach (char *args, int from_tty)
 {
   struct lwp_info *lp;
+  struct target_ops *process_ops;
 
+  process_ops = get_target_below ();
   /* FIXME: We should probably accept a list of process id's, and
      attach all of them.  */
-  child_ops.to_attach (args, from_tty);
+  if (process_ops!=NULL)
+      if ((process_ops->to_attach)!=NULL)
+          process_ops->to_attach (args, from_tty);
 
   /* Add the initial process as the first LWP to the list.  */
   lp = add_lwp (BUILD_LWP (PIDGET (inferior_ptid), PIDGET (inferior_ptid)));
@@ -392,6 +399,8 @@ detach_callback (struct lwp_info *lp, vo
 static void
 lin_lwp_detach (char *args, int from_tty)
 {
+  struct target_ops *process_ops;
+
   iterate_over_lwps (detach_callback, NULL);
 
   /* Only the initial (uncloned) process should be left right now.  */
@@ -407,7 +416,11 @@ lin_lwp_detach (char *args, int from_tty
   sigemptyset (&blocked_mask);
 
   inferior_ptid = pid_to_ptid (GET_PID (inferior_ptid));
-  child_ops.to_detach (args, from_tty);
+
+  process_ops = get_target_below ();
+  if (process_ops!=NULL)
+      if ((process_ops->to_detach)!=NULL)
+          (process_ops->to_detach) (args, from_tty);
 }
 
 
@@ -435,6 +448,8 @@ find_lwp_callback (struct thread_info *t
 static int
 resume_callback (struct lwp_info *lp, void *data)
 {
+  struct target_ops *process_ops;
+
   if (lp->stopped && lp->status == 0)
     {
       struct thread_info *tp;
@@ -460,7 +475,12 @@ resume_callback (struct lwp_info *lp, vo
 	}
 #endif
 
-      child_resume (pid_to_ptid (GET_LWP (lp->ptid)), 0, TARGET_SIGNAL_0);
+       process_ops = get_target_below ();
+       if (process_ops!=NULL)
+          if ((process_ops->to_resume)!=NULL)
+              (process_ops->to_resume) (pid_to_ptid (GET_LWP (lp->ptid)),
+                    0, TARGET_SIGNAL_0);
+
       lp->stopped = 0;
       lp->step = 0;
     }
@@ -471,6 +491,7 @@ resume_callback (struct lwp_info *lp, vo
 static void
 lin_lwp_resume (ptid_t ptid, int step, enum target_signal signo)
 {
+  struct target_ops *process_ops;
   struct lwp_info *lp;
   int resume_all;
 
@@ -511,7 +532,10 @@ lin_lwp_resume (ptid_t ptid, int step, e
   if (resume_all)
     iterate_over_lwps (resume_callback, NULL);
 
-  child_resume (ptid, step, signo);
+  process_ops = get_target_below ();
+  if (process_ops!=NULL)
+      if ((process_ops->to_resume)!=NULL)
+         (process_ops->to_resume) (ptid, step, signo);
 }
 
 
@@ -653,6 +677,7 @@ running_callback (struct lwp_info *lp, v
 static ptid_t
 lin_lwp_wait (ptid_t ptid, struct target_waitstatus *ourstatus)
 {
+  struct target_ops *process_ops;
   struct lwp_info *lp = NULL;
   int options = 0;
   int status = 0;
@@ -727,8 +752,12 @@ lin_lwp_wait (ptid_t ptid, struct target
 
       /* Resume the thread.  It should halt immediately returning the
 	 pending SIGSTOP.  */
-      child_resume (pid_to_ptid (GET_LWP (lp->ptid)), lp->step,
-                    TARGET_SIGNAL_0);
+      process_ops = get_target_below ();
+      if (process_ops!=NULL)
+          if ((process_ops->to_resume)!=NULL)
+              (process_ops->to_resume) (pid_to_ptid (GET_LWP (lp->ptid)),
+              		lp->step,TARGET_SIGNAL_0);
+              		
       lp->stopped = 0;
 
       /* This should catch the pending SIGSTOP.  */
@@ -813,8 +842,12 @@ lin_lwp_wait (ptid_t ptid, struct target
 	      /* This is a delayed SIGSTOP.  */
 	      lp->signalled = 0;
 
-	      child_resume (pid_to_ptid (GET_LWP (lp->ptid)), lp->step,
-	                    TARGET_SIGNAL_0);
+	      process_ops = get_target_below ();
+      	      if (process_ops!=NULL)
+           	  if ((process_ops->to_resume)!=NULL)
+              	       (process_ops->to_resume) (pid_to_ptid (GET_LWP (lp->ptid)),
+              	       		lp->step, TARGET_SIGNAL_0);
+	
 	      lp->stopped = 0;
 
 	      /* Discard the event.  */
@@ -859,7 +892,13 @@ lin_lwp_wait (ptid_t ptid, struct target
 	  && signal_print_state (signo) == 0
 	  && signal_pass_state (signo) == 1)
 	{
-	  child_resume (pid_to_ptid (GET_LWP (lp->ptid)), lp->step, signo);
+	
+	  process_ops = get_target_below ();
+      	  if (process_ops!=NULL)
+              if ((process_ops->to_resume)!=NULL)
+              (process_ops->to_resume) (pid_to_ptid (GET_LWP (lp->ptid)),
+              		lp->step, signo);
+              		
 	  lp->stopped = 0;
 	  status = 0;
 	  goto retry;
@@ -931,24 +970,36 @@ kill_wait_callback (struct lwp_info *lp,
 static void
 lin_lwp_kill (void)
 {
+  struct target_ops *process_ops;
+
   /* Kill all LWP's ...  */
   iterate_over_lwps (kill_callback, NULL);
 
   /* ... and wait until we've flushed all events.  */
   iterate_over_lwps (kill_wait_callback, NULL);
 
-  target_mourn_inferior ();
+  process_ops = get_target_below ();
+  if (process_ops!=NULL)
+      if ((process_ops->to_mourn_inferior)!=NULL)
+          (process_ops->to_mourn_inferior) ();
 }
 
 static void
 lin_lwp_create_inferior (char *exec_file, char *allargs, char **env)
 {
-  child_ops.to_create_inferior (exec_file, allargs, env);
+  struct target_ops *process_ops;
+
+  process_ops = get_target_below ();
+  if (process_ops!=NULL)
+      if ((process_ops->to_create_inferior)!=NULL)
+          (process_ops->to_create_inferior) (exec_file, allargs, env);
 }
 
-static void  
+static void
 lin_lwp_mourn_inferior (void)
 {
+  struct target_ops *process_ops;
+
   trap_ptid = null_ptid;
 
   /* Destroy LWP info; it's no longer valid.  */
@@ -958,18 +1009,25 @@ lin_lwp_mourn_inferior (void)
   sigprocmask (SIG_SETMASK, &normal_mask, NULL);
   sigemptyset (&blocked_mask);
 
-  child_ops.to_mourn_inferior ();
+  process_ops = get_target_below ();
+  if (process_ops!=NULL)
+      if ((process_ops->to_mourn_inferior)!=NULL)
+         (process_ops->to_mourn_inferior) ();
 }
 
 static void
 lin_lwp_fetch_registers (int regno)
 {
+  struct target_ops *process_ops;
   struct cleanup *old_chain = save_inferior_ptid ();
 
   if (is_lwp (inferior_ptid))
     inferior_ptid = pid_to_ptid (GET_LWP (inferior_ptid));
 
-  fetch_inferior_registers (regno);
+  process_ops = get_target_below ();
+  if (process_ops!=NULL)
+      if ((process_ops->to_fetch_registers)!=NULL)
+         (process_ops->to_fetch_registers) (regno);
 
   do_cleanups (old_chain);
 }
@@ -977,12 +1035,16 @@ lin_lwp_fetch_registers (int regno)
 static void
 lin_lwp_store_registers (int regno)
 {
+  struct target_ops *process_ops;
   struct cleanup *old_chain = save_inferior_ptid ();
 
   if (is_lwp (inferior_ptid))
     inferior_ptid = pid_to_ptid (GET_LWP (inferior_ptid));
 
-  store_inferior_registers (regno);
+  process_ops = get_target_below ();
+  if (process_ops!=NULL)
+      if ((process_ops->to_store_registers)!=NULL)
+         (process_ops->to_store_registers) (regno);
 
   do_cleanups (old_chain);
 }
@@ -992,13 +1054,17 @@ lin_lwp_xfer_memory (CORE_ADDR memaddr, 
 		     struct mem_attrib *attrib,
 		     struct target_ops *target)
 {
+  struct target_ops *process_ops;
   struct cleanup *old_chain = save_inferior_ptid ();
-  int xfer;
+  int xfer = 0;
 
   if (is_lwp (inferior_ptid))
     inferior_ptid = pid_to_ptid (GET_LWP (inferior_ptid));
 
-  xfer = child_xfer_memory (memaddr, myaddr, len, write, attrib, target);
+  process_ops = get_target_below ();
+  if (process_ops!=NULL)
+      if ((process_ops->to_xfer_memory)!=NULL)
+         xfer = (process_ops->to_xfer_memory) (memaddr, myaddr, len, write, attrib, target);
 
   do_cleanups (old_chain);
   return xfer;
@@ -1160,4 +1226,53 @@ lin_thread_get_thread_signals (sigset_t 
 
   /* ... except during a sigsuspend.  */
   sigdelset (&suspend_mask, cancel);
+}
+
+/* FIXME: I truely should use a target stack macro/function
+   that returns the next lower target that has a non-NULL
+   pointer in a given function pointer.  What if a new
+   stratum is added just above the process_stratum?  Should
+   the process_stratum or the new stratum's function be called.
+   I think in general that it should be the next lower startum
+   that has the non-NULL given function pointer.  This is a
+   job for a portable C coding wizard.
+   John S. Kallal  2001-MAY-18  */
+
+
+/* FIXME: Maybe function find_target_stratum should go
+   into the target.c file?  But for now only this file needs
+   this function.  Better yet, put the lwp-layer target into
+   the target stack.  John S. Kallal  2001-MAY-18 */
+
+/* Find a single target at the given stratum level in the
+   target stack and return a pointer to it.  If there is no
+   target at the given stratum level in the target stack,
+   return NULL.  */
+
+static struct target_ops *
+find_target_stratum (enum strata level)
+{
+  struct target_stack_item *cur;
+
+  for (cur = target_stack; cur; cur = cur->next)
+    {
+       if (cur->target_ops->to_stratum == level)
+          return cur->target_ops;
+    }
+
+  return NULL;
+}
+
+/* Find the target below the thread_stratum
+   (i.e process_stratum).  This is needed because
+   currently the lwp-layer is NOT stacked. */
+
+static struct target_ops *
+get_target_below (void)
+{
+  struct target_ops *process_ops;
+
+  process_ops = find_target_stratum( process_stratum );
+
+  return process_ops;
 }