Refactor native follow-fork.

This patch reorganizes the code that implements follow-fork and
detach-on-fork in preparation for implementation of those features for the
extended-remote target.  The function linux-nat.c:linux_child_follow_fork
contained target-independent code mixed in with target-dependent code.  The
target-independent pieces need to be accessible for the host-side
implementation of follow-fork for extended-remote Linux targets.

The changes are fairly mechanical.  A new routine, follow_fork_inferior,
is implemented in infrun.c, containing those parts of
linux_child_follow_fork that manage inferiors and the inferior list.  The
parts of linux_child_follow_fork that deal with LWPs and target-specifics
were left in-place.  Although the order of some operations was changed, the
resulting functionality was not.

Modifications were made to the other native target follow-fork functions,
inf_ttrace_follow_fork and inf_ptrace_follow_fork, that should allow them
to work with follow_fork_inferior.  Some other adjustments were necessary
in inf-ttrace.c.  The changes to inf-ttrace.c and inf-ptrace.c were not
tested.

gdb/ChangeLog:

	* inf-ptrace.c (inf_ptrace_follow_fork): Remove target-independent
	code so as to work with follow_fork_inferior.
	* inf-ttrace.c (inf_ttrace_follow_fork): Ditto.
	(inf_ttrace_create_inferior): Remove reference to
	inf_ttrace_vfork_ppid.
	(inf_ttrace_attach): Ditto.
	(inf_ttrace_detach): Ditto.
	(inf_ttrace_kill): Use current_inferior instead of
	inf_ttrace_vfork_ppid.
	(inf_ttrace_wait): Eliminate use of inf_ttrace_vfork_ppid, report
	TARGET_WAITKIND_VFORK_DONE event, delete HACK that switched the
	inferior away from the parent.
	* infrun.c (follow_fork): Call follow_fork_inferior instead of
	target_follow_fork.
	(follow_fork_inferior): New function.
	(follow_inferior_reset_breakpoints): Make function static.
	* infrun.h (follow_inferior_reset_breakpoints): Remove declaration.
	* linux-nat.c (linux_child_follow_fork): Move target-independent
	code to infrun.c:follow_fork_inferior.

1 files changed, 245 insertions, 4 deletions

diff --git a/gdb/infrun.c b/gdb/infrun.c
index 5e123be..728c160 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -60,6 +60,7 @@
 #include "completer.h"
 #include "target-descriptions.h"
 #include "target-dcache.h"
+#include "terminal.h"
 
 /* Prototypes for local functions */
 
@@ -79,6 +80,10 @@ static int restore_selected_frame (void *);
 
 static int follow_fork (void);
 
+static int follow_fork_inferior (int follow_child, int detach_fork);
+
+static void follow_inferior_reset_breakpoints (void);
+
 static void set_schedlock_func (char *args, int from_tty,
 				struct cmd_list_element *c);
 
@@ -396,6 +401,241 @@ show_follow_fork_mode_string (struct ui_file *file, int from_tty,
 }
 
 
+/* Handle changes to the inferior list based on the type of fork,
+   which process is being followed, and whether the other process
+   should be detached.  On entry inferior_ptid must be the ptid of
+   the fork parent.  At return inferior_ptid is the ptid of the
+   followed inferior.  */
+
+static int
+follow_fork_inferior (int follow_child, int detach_fork)
+{
+  int has_vforked;
+  int parent_pid, child_pid;
+
+  has_vforked = (inferior_thread ()->pending_follow.kind
+		 == TARGET_WAITKIND_VFORKED);
+  parent_pid = ptid_get_lwp (inferior_ptid);
+  if (parent_pid == 0)
+    parent_pid = ptid_get_pid (inferior_ptid);
+  child_pid
+    = ptid_get_pid (inferior_thread ()->pending_follow.value.related_pid);
+
+  if (has_vforked
+      && !non_stop /* Non-stop always resumes both branches.  */
+      && (!target_is_async_p () || sync_execution)
+      && !(follow_child || detach_fork || sched_multi))
+    {
+      /* The parent stays blocked inside the vfork syscall until the
+	 child execs or exits.  If we don't let the child run, then
+	 the parent stays blocked.  If we're telling the parent to run
+	 in the foreground, the user will not be able to ctrl-c to get
+	 back the terminal, effectively hanging the debug session.  */
+      fprintf_filtered (gdb_stderr, _("\
+Can not resume the parent process over vfork in the foreground while\n\
+holding the child stopped.  Try \"set detach-on-fork\" or \
+\"set schedule-multiple\".\n"));
+      /* FIXME output string > 80 columns.  */
+      return 1;
+    }
+
+  if (!follow_child)
+    {
+      /* Detach new forked process?  */
+      if (detach_fork)
+	{
+	  struct cleanup *old_chain;
+
+	  /* Before detaching from the child, remove all breakpoints
+	     from it.  If we forked, then this has already been taken
+	     care of by infrun.c.  If we vforked however, any
+	     breakpoint inserted in the parent is visible in the
+	     child, even those added while stopped in a vfork
+	     catchpoint.  This will remove the breakpoints from the
+	     parent also, but they'll be reinserted below.  */
+	  if (has_vforked)
+	    {
+	      /* Keep breakpoints list in sync.  */
+	      remove_breakpoints_pid (ptid_get_pid (inferior_ptid));
+	    }
+
+	  if (info_verbose || debug_infrun)
+	    {
+	      target_terminal_ours ();
+	      fprintf_filtered (gdb_stdlog,
+				"Detaching after fork from "
+				"child process %d.\n",
+				child_pid);
+	    }
+	}
+      else
+	{
+	  struct inferior *parent_inf, *child_inf;
+	  struct cleanup *old_chain;
+
+	  /* Add process to GDB's tables.  */
+	  child_inf = add_inferior (child_pid);
+
+	  parent_inf = current_inferior ();
+	  child_inf->attach_flag = parent_inf->attach_flag;
+	  copy_terminal_info (child_inf, parent_inf);
+	  child_inf->gdbarch = parent_inf->gdbarch;
+	  copy_inferior_target_desc_info (child_inf, parent_inf);
+
+	  old_chain = save_inferior_ptid ();
+	  save_current_program_space ();
+
+	  inferior_ptid = ptid_build (child_pid, child_pid, 0);
+	  add_thread (inferior_ptid);
+	  child_inf->symfile_flags = SYMFILE_NO_READ;
+
+	  /* If this is a vfork child, then the address-space is
+	     shared with the parent.  */
+	  if (has_vforked)
+	    {
+	      child_inf->pspace = parent_inf->pspace;
+	      child_inf->aspace = parent_inf->aspace;
+
+	      /* The parent will be frozen until the child is done
+		 with the shared region.  Keep track of the
+		 parent.  */
+	      child_inf->vfork_parent = parent_inf;
+	      child_inf->pending_detach = 0;
+	      parent_inf->vfork_child = child_inf;
+	      parent_inf->pending_detach = 0;
+	    }
+	  else
+	    {
+	      child_inf->aspace = new_address_space ();
+	      child_inf->pspace = add_program_space (child_inf->aspace);
+	      child_inf->removable = 1;
+	      set_current_program_space (child_inf->pspace);
+	      clone_program_space (child_inf->pspace, parent_inf->pspace);
+
+	      /* Let the shared library layer (e.g., solib-svr4) learn
+		 about this new process, relocate the cloned exec, pull
+		 in shared libraries, and install the solib event
+		 breakpoint.  If a "cloned-VM" event was propagated
+		 better throughout the core, this wouldn't be
+		 required.  */
+	      solib_create_inferior_hook (0);
+	    }
+
+	  do_cleanups (old_chain);
+	}
+
+      if (has_vforked)
+	{
+	  struct inferior *parent_inf;
+
+	  parent_inf = current_inferior ();
+
+	  /* If we detached from the child, then we have to be careful
+	     to not insert breakpoints in the parent until the child
+	     is done with the shared memory region.  However, if we're
+	     staying attached to the child, then we can and should
+	     insert breakpoints, so that we can debug it.  A
+	     subsequent child exec or exit is enough to know when does
+	     the child stops using the parent's address space.  */
+	  parent_inf->waiting_for_vfork_done = detach_fork;
+	  parent_inf->pspace->breakpoints_not_allowed = detach_fork;
+	}
+    }
+  else
+    {
+      /* Follow the child.  */
+      struct inferior *parent_inf, *child_inf;
+      struct program_space *parent_pspace;
+
+      if (info_verbose || debug_infrun)
+	{
+	  target_terminal_ours ();
+	  if (has_vforked)
+	    fprintf_filtered (gdb_stdlog,
+			      _("Attaching after process %d "
+				"vfork to child process %d.\n"),
+			      parent_pid, child_pid);
+	  else
+	    fprintf_filtered (gdb_stdlog,
+			      _("Attaching after process %d "
+				"fork to child process %d.\n"),
+			      parent_pid, child_pid);
+	}
+
+      /* Add the new inferior first, so that the target_detach below
+	 doesn't unpush the target.  */
+
+      child_inf = add_inferior (child_pid);
+
+      parent_inf = current_inferior ();
+      child_inf->attach_flag = parent_inf->attach_flag;
+      copy_terminal_info (child_inf, parent_inf);
+      child_inf->gdbarch = parent_inf->gdbarch;
+      copy_inferior_target_desc_info (child_inf, parent_inf);
+
+      parent_pspace = parent_inf->pspace;
+
+      /* If we're vforking, we want to hold on to the parent until the
+	 child exits or execs.  At child exec or exit time we can
+	 remove the old breakpoints from the parent and detach or
+	 resume debugging it.  Otherwise, detach the parent now; we'll
+	 want to reuse it's program/address spaces, but we can't set
+	 them to the child before removing breakpoints from the
+	 parent, otherwise, the breakpoints module could decide to
+	 remove breakpoints from the wrong process (since they'd be
+	 assigned to the same address space).  */
+
+      if (has_vforked)
+	{
+	  gdb_assert (child_inf->vfork_parent == NULL);
+	  gdb_assert (parent_inf->vfork_child == NULL);
+	  child_inf->vfork_parent = parent_inf;
+	  child_inf->pending_detach = 0;
+	  parent_inf->vfork_child = child_inf;
+	  parent_inf->pending_detach = detach_fork;
+	  parent_inf->waiting_for_vfork_done = 0;
+	}
+      else if (detach_fork)
+	target_detach (NULL, 0);
+
+      /* Note that the detach above makes PARENT_INF dangling.  */
+
+      /* Add the child thread to the appropriate lists, and switch to
+	 this new thread, before cloning the program space, and
+	 informing the solib layer about this new process.  */
+
+      inferior_ptid = ptid_build (child_pid, child_pid, 0);
+      add_thread (inferior_ptid);
+
+      /* If this is a vfork child, then the address-space is shared
+	 with the parent.  If we detached from the parent, then we can
+	 reuse the parent's program/address spaces.  */
+      if (has_vforked || detach_fork)
+	{
+	  child_inf->pspace = parent_pspace;
+	  child_inf->aspace = child_inf->pspace->aspace;
+	}
+      else
+	{
+	  child_inf->aspace = new_address_space ();
+	  child_inf->pspace = add_program_space (child_inf->aspace);
+	  child_inf->removable = 1;
+	  child_inf->symfile_flags = SYMFILE_NO_READ;
+	  set_current_program_space (child_inf->pspace);
+	  clone_program_space (child_inf->pspace, parent_pspace);
+
+	  /* Let the shared library layer (e.g., solib-svr4) learn
+	     about this new process, relocate the cloned exec, pull in
+	     shared libraries, and install the solib event breakpoint.
+	     If a "cloned-VM" event was propagated better throughout
+	     the core, this wouldn't be required.  */
+	  solib_create_inferior_hook (0);
+	}
+    }
+
+  return target_follow_fork (follow_child, detach_fork);
+}
+
 /* Tell the target to follow the fork we're stopped at.  Returns true
    if the inferior should be resumed; false, if the target for some
    reason decided it's best not to resume.  */
@@ -486,9 +726,10 @@ follow_fork (void)
 	parent = inferior_ptid;
 	child = tp->pending_follow.value.related_pid;
 
-	/* Tell the target to do whatever is necessary to follow
-	   either parent or child.  */
-	if (target_follow_fork (follow_child, detach_fork))
+	/* Set up inferior(s) as specified by the caller, and tell the
+	   target to do whatever is necessary to follow either parent
+	   or child.  */
+	if (follow_fork_inferior (follow_child, detach_fork))
 	  {
 	    /* Target refused to follow, or there's some other reason
 	       we shouldn't resume.  */
@@ -560,7 +801,7 @@ follow_fork (void)
   return should_resume;
 }
 
-void
+static void
 follow_inferior_reset_breakpoints (void)
 {
   struct thread_info *tp = inferior_thread ();