Add iterate_over_lwps to gdbserver

This commit introduces a new function, iterate_over_lwps, that
shared Linux code can use to call a function for each LWP that
matches certain criteria.  This function already existed in GDB
and was in use by GDB's various low-level Linux x86 debug register
setters.  An equivalent was written for gdbserver and gdbserver's
low-level Linux x86 debug register setters were modified to use
it.

gdb/ChangeLog:

	* linux-nat.h: Include nat/linux-nat.h.
	(iterate_over_lwps): Move declaration to nat/linux-nat.h.
	* nat/linux-nat.h (struct lwp_info): New forward declaration.
	(iterate_over_lwps_ftype): New typedef.
	(iterate_over_lwps): New declaration.
	* linux-nat.h (iterate_over_lwps): Update comment.  Use
	iterate_over_lwps_ftype.  Update callback return value check.

gdb/gdbserver/ChangeLog:

	* linux-low.h: Include nat/linux-nat.h.
	* linux-low.c (iterate_over_lwps_args): New structure.
	(iterate_over_lwps_filter): New function.
	(iterate_over_lwps): Likewise.
	* linux-x86-low.c (update_debug_registers_callback):
	Update signature to what iterate_over_lwps expects.
	Remove PID check that iterate_over_lwps now performs.
	(x86_dr_low_set_addr): Use iterate_over_lwps.
	(x86_dr_low_set_control): Likewise.

8 files changed, 108 insertions, 34 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0be8425..fb5d1b4 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,15 @@
 2015-03-24  Gary Benson  <gbenson@redhat.com>
 
+	* linux-nat.h: Include nat/linux-nat.h.
+	(iterate_over_lwps): Move declaration to nat/linux-nat.h.
+	* nat/linux-nat.h (struct lwp_info): New forward declaration.
+	(iterate_over_lwps_ftype): New typedef.
+	(iterate_over_lwps): New declaration.
+	* linux-nat.h (iterate_over_lwps): Update comment.  Use
+	iterate_over_lwps_ftype.  Update callback return value check.
+
+2015-03-24  Gary Benson  <gbenson@redhat.com>
+
 	* x86-nat.h (x86_debug_reg_state): Move declaration to...
 	* nat/x86-dregs.h (x86_debug_reg_state): New declaration.
 
diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 49477df..1badce3 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,5 +1,17 @@
 2015-03-24  Gary Benson  <gbenson@redhat.com>
 
+	* linux-low.h: Include nat/linux-nat.h.
+	* linux-low.c (iterate_over_lwps_args): New structure.
+	(iterate_over_lwps_filter): New function.
+	(iterate_over_lwps): Likewise.
+	* linux-x86-low.c (update_debug_registers_callback):
+	Update signature to what iterate_over_lwps expects.
+	Remove PID check that iterate_over_lwps now performs.
+	(x86_dr_low_set_addr): Use iterate_over_lwps.
+	(x86_dr_low_set_control): Likewise.
+
+2015-03-24  Gary Benson  <gbenson@redhat.com>
+
 	* linux-x86-low.c (x86_debug_reg_state): New function.
 	(x86_linux_prepare_to_resume): Use the above.
 
diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index 7a12b4f..0c74e11 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -1397,6 +1397,60 @@ num_lwps (int pid)
   return count;
 }
 
+/* The arguments passed to iterate_over_lwps.  */
+
+struct iterate_over_lwps_args
+{
+  /* The FILTER argument passed to iterate_over_lwps.  */
+  ptid_t filter;
+
+  /* The CALLBACK argument passed to iterate_over_lwps.  */
+  iterate_over_lwps_ftype *callback;
+
+  /* The DATA argument passed to iterate_over_lwps.  */
+  void *data;
+};
+
+/* Callback for find_inferior used by iterate_over_lwps to filter
+   calls to the callback supplied to that function.  Returning a
+   nonzero value causes find_inferiors to stop iterating and return
+   the current inferior_list_entry.  Returning zero indicates that
+   find_inferiors should continue iterating.  */
+
+static int
+iterate_over_lwps_filter (struct inferior_list_entry *entry, void *args_p)
+{
+  struct iterate_over_lwps_args *args
+    = (struct iterate_over_lwps_args *) args_p;
+
+  if (ptid_match (entry->id, args->filter))
+    {
+      struct thread_info *thr = (struct thread_info *) entry;
+      struct lwp_info *lwp = get_thread_lwp (thr);
+
+      return (*args->callback) (lwp, args->data);
+    }
+
+  return 0;
+}
+
+/* See nat/linux-nat.h.  */
+
+struct lwp_info *
+iterate_over_lwps (ptid_t filter,
+		   iterate_over_lwps_ftype callback,
+		   void *data)
+{
+  struct iterate_over_lwps_args args = {filter, callback, data};
+  struct inferior_list_entry *entry;
+
+  entry = find_inferior (&all_threads, iterate_over_lwps_filter, &args);
+  if (entry == NULL)
+    return NULL;
+
+  return get_thread_lwp ((struct thread_info *) entry);
+}
+
 /* Detect zombie thread group leaders, and "exit" them.  We can't reap
    their exits until all other threads in the group have exited.  */
 
diff --git a/gdb/gdbserver/linux-low.h b/gdb/gdbserver/linux-low.h
index bbff3aa..2cfe140 100644
--- a/gdb/gdbserver/linux-low.h
+++ b/gdb/gdbserver/linux-low.h
@@ -16,6 +16,7 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
+#include "nat/linux-nat.h"
 #include "nat/gdb_thread_db.h"
 #include <signal.h>
 
diff --git a/gdb/gdbserver/linux-x86-low.c b/gdb/gdbserver/linux-x86-low.c
index fe4fd25..3425492 100644
--- a/gdb/gdbserver/linux-x86-low.c
+++ b/gdb/gdbserver/linux-x86-low.c
@@ -575,25 +575,16 @@ x86_linux_dr_set (ptid_t ptid, int regnum, unsigned long value)
 }
 
 static int
-update_debug_registers_callback (struct inferior_list_entry *entry,
-				 void *pid_p)
+update_debug_registers_callback (struct lwp_info *lwp, void *arg)
 {
-  struct thread_info *thr = (struct thread_info *) entry;
-  struct lwp_info *lwp = get_thread_lwp (thr);
-  int pid = *(int *) pid_p;
+  /* The actual update is done later just before resuming the lwp,
+     we just mark that the registers need updating.  */
+  lwp->arch_private->debug_registers_changed = 1;
 
-  /* Only update the threads of this process.  */
-  if (pid_of (thr) == pid)
-    {
-      /* The actual update is done later just before resuming the lwp,
-	 we just mark that the registers need updating.  */
-      lwp->arch_private->debug_registers_changed = 1;
-
-      /* If the lwp isn't stopped, force it to momentarily pause, so
-	 we can update its debug registers.  */
-      if (!lwp->stopped)
-	linux_stop_lwp (lwp);
-    }
+  /* If the lwp isn't stopped, force it to momentarily pause, so
+     we can update its debug registers.  */
+  if (!lwp->stopped)
+    linux_stop_lwp (lwp);
 
   return 0;
 }
@@ -604,11 +595,11 @@ static void
 x86_dr_low_set_addr (int regnum, CORE_ADDR addr)
 {
   /* Only update the threads of this process.  */
-  int pid = pid_of (current_thread);
+  ptid_t pid_ptid = pid_to_ptid (ptid_get_pid (current_lwp_ptid ()));
 
   gdb_assert (DR_FIRSTADDR <= regnum && regnum <= DR_LASTADDR);
 
-  find_inferior (&all_threads, update_debug_registers_callback, &pid);
+  iterate_over_lwps (pid_ptid, update_debug_registers_callback, NULL);
 }
 
 /* Return the inferior's debug register REGNUM.  */
@@ -627,9 +618,9 @@ static void
 x86_dr_low_set_control (unsigned long control)
 {
   /* Only update the threads of this process.  */
-  int pid = pid_of (current_thread);
+  ptid_t pid_ptid = pid_to_ptid (ptid_get_pid (current_lwp_ptid ()));
 
-  find_inferior (&all_threads, update_debug_registers_callback, &pid);
+  iterate_over_lwps (pid_ptid, update_debug_registers_callback, NULL);
 }
 
 /* Return the inferior's DR7 debug control register.  */
diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 8eb73d9..5a2cba5 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -834,14 +834,11 @@ find_lwp_pid (ptid_t ptid)
   return NULL;
 }
 
-/* Call CALLBACK with its second argument set to DATA for every LWP in
-   the list.  If CALLBACK returns 1 for a particular LWP, return a
-   pointer to the structure describing that LWP immediately.
-   Otherwise return NULL.  */
+/* See nat/linux-nat.h.  */
 
 struct lwp_info *
 iterate_over_lwps (ptid_t filter,
-		   int (*callback) (struct lwp_info *, void *),
+		   iterate_over_lwps_ftype callback,
 		   void *data)
 {
   struct lwp_info *lp, *lpnext;
@@ -852,7 +849,7 @@ iterate_over_lwps (ptid_t filter,
 
       if (ptid_match (lp->ptid, filter))
 	{
-	  if ((*callback) (lp, data))
+	  if ((*callback) (lp, data) != 0)
 	    return lp;
 	}
     }
diff --git a/gdb/linux-nat.h b/gdb/linux-nat.h
index 87bc75b..4dd3932 100644
--- a/gdb/linux-nat.h
+++ b/gdb/linux-nat.h
@@ -17,8 +17,8 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
+#include "nat/linux-nat.h"
 #include "target.h"
-
 #include <signal.h>
 
 struct arch_lwp_info;
@@ -151,12 +151,6 @@ extern void linux_stop_and_wait_all_lwps (void);
    left stopped.)  */
 extern void linux_unstop_all_lwps (void);
 
-/* Iterator function for lin-lwp's lwp list.  */
-struct lwp_info *iterate_over_lwps (ptid_t filter,
-				    int (*callback) (struct lwp_info *,
-						     void *), 
-				    void *data);
-
 /* Create a prototype generic GNU/Linux target.  The client can
    override it with local methods.  */
 struct target_ops * linux_target (void);
diff --git a/gdb/nat/linux-nat.h b/gdb/nat/linux-nat.h
index c06f72d..c534944 100644
--- a/gdb/nat/linux-nat.h
+++ b/gdb/nat/linux-nat.h
@@ -20,6 +20,8 @@
 #ifndef LINUX_NAT_H
 #define LINUX_NAT_H
 
+struct lwp_info;
+
 /* Unlike other extended result codes, WSTOPSIG (status) on
    PTRACE_O_TRACESYSGOOD syscall events doesn't return SIGTRAP, but
    instead SIGTRAP with bit 7 set.  */
@@ -32,4 +34,17 @@
 
 extern ptid_t current_lwp_ptid (void);
 
+/* Function type for the CALLBACK argument of iterate_over_lwps.  */
+typedef int (iterate_over_lwps_ftype) (struct lwp_info *lwp, void *arg);
+
+/* Iterate over all LWPs.  Calls CALLBACK with its second argument set
+   to DATA for every LWP in the list.  If CALLBACK returns nonzero for
+   a particular LWP, return a pointer to the structure describing that
+   LWP immediately.  Otherwise return NULL.  This function must be
+   provided by the client.  */
+
+extern struct lwp_info *iterate_over_lwps (ptid_t filter,
+					   iterate_over_lwps_ftype callback,
+					   void *data);
+
 #endif /* LINUX_NAT_H */