Remove parameter sysret from linux_target_ops.get_syscall_trapinfo

When I implement linux_target_ops.get_syscall_trapinfo for aarch64 and arm,
I find the second parameter sysret isn't used at all.  In RSP, we don't
need syscall return value either, because GDB can figure out the return
value from registers content got by 'g' packet.

This patch is to remove them.

gdb/gdbserver:

2016-06-28  Yao Qi  <yao.qi@linaro.org>

	* linux-low.c (get_syscall_trapinfo): Remove parameter sysret.
	Callers updated.
	* linux-low.h (struct linux_target_ops) <get_syscall_trapinfo>:
	Remove parameter sysno.
	* linux-x86-low.c (x86_get_syscall_trapinfo): Remove parameter
	sysret.

gdb/gdbserver/ChangeLog

@@ -1,3 +1,12 @@
+2016-06-28  Yao Qi  <yao.qi@linaro.org>
+
+	* linux-low.c (get_syscall_trapinfo): Remove parameter sysret.
+	Callers updated.
+	* linux-low.h (struct linux_target_ops) <get_syscall_trapinfo>:
+	Remove parameter sysno.
+	* linux-x86-low.c (x86_get_syscall_trapinfo): Remove parameter
+	sysret.
+
 2016-06-21  Andreas Arnez  <arnez@linux.vnet.ibm.com>
 
 	* linux-s390-low.c (s390_emit_eq_goto): Mark function static.

gdb/gdbserver/linux-low.c

@@ -758,11 +758,10 @@ get_pc (struct lwp_info *lwp)
 }
 
 /* This function should only be called if LWP got a SYSCALL_SIGTRAP.
-   Fill *SYSNO with the syscall nr trapped.  Fill *SYSRET with the
+   Fill *SYSNO with the syscall nr trapped.  */
-   return code.  */
 
 static void
-get_syscall_trapinfo (struct lwp_info *lwp, int *sysno, int *sysret)
+get_syscall_trapinfo (struct lwp_info *lwp, int *sysno)
 {
   struct thread_info *saved_thread;
   struct regcache *regcache;
@@ -770,9 +769,8 @@ get_syscall_trapinfo (struct lwp_info *lwp, int *sysno, int *sysret)
   if (the_low_target.get_syscall_trapinfo == NULL)
     {
       /* If we cannot get the syscall trapinfo, report an unknown
-	 system call number and -ENOSYS return value.  */
+	 system call number.  */
       *sysno = UNKNOWN_SYSCALL;
-      *sysret = -ENOSYS;
       return;
     }
 
@@ -780,13 +778,10 @@ get_syscall_trapinfo (struct lwp_info *lwp, int *sysno, int *sysret)
   current_thread = get_lwp_thread (lwp);
 
   regcache = get_thread_regcache (current_thread, 1);
-  (*the_low_target.get_syscall_trapinfo) (regcache, sysno, sysret);
+  (*the_low_target.get_syscall_trapinfo) (regcache, sysno);
 
   if (debug_threads)
-    {
+    debug_printf ("get_syscall_trapinfo sysno %d\n", *sysno);
-      debug_printf ("get_syscall_trapinfo sysno %d sysret %d\n",
-		    *sysno, *sysret);
-    }
 
   current_thread = saved_thread;
 }
@@ -3116,7 +3111,7 @@ static int
 gdb_catch_this_syscall_p (struct lwp_info *event_child)
 {
   int i, iter;
-  int sysno, sysret;
+  int sysno;
   struct thread_info *thread = get_lwp_thread (event_child);
   struct process_info *proc = get_thread_process (thread);
 
@@ -3126,7 +3121,7 @@ gdb_catch_this_syscall_p (struct lwp_info *event_child)
   if (VEC_index (int, proc->syscalls_to_catch, 0) == ANY_SYSCALL)
     return 1;
 
-  get_syscall_trapinfo (event_child, &sysno, &sysret);
+  get_syscall_trapinfo (event_child, &sysno);
   for (i = 0;
        VEC_iterate (int, proc->syscalls_to_catch, i, iter);
        i++)
@@ -3734,10 +3729,8 @@ linux_wait_1 (ptid_t ptid,
 
   if (WSTOPSIG (w) == SYSCALL_SIGTRAP)
     {
-      int sysret;
-
       get_syscall_trapinfo (event_child,
-			    &ourstatus->value.syscall_number, &sysret);
+			    &ourstatus->value.syscall_number);
       ourstatus->kind = event_child->syscall_state;
     }
   else if (current_thread->last_resume_kind == resume_stop

gdb/gdbserver/linux-low.h

@@ -241,11 +241,9 @@ struct linux_target_ops
   /* See target.h.  */
   int (*supports_hardware_single_step) (void);
 
-  /* Fill *SYSNO with the syscall nr trapped.  Fill *SYSRET with the
+  /* Fill *SYSNO with the syscall nr trapped.  Only to be called when
-     return code.  Only to be called when inferior is stopped
+     inferior is stopped due to SYSCALL_SIGTRAP.  */
-     due to SYSCALL_SIGTRAP.  */
+  void (*get_syscall_trapinfo) (struct regcache *regcache, int *sysno);
-  void (*get_syscall_trapinfo) (struct regcache *regcache,
-				int *sysno, int *sysret);
 
   /* See target.h.  */
   int (*get_ipa_tdesc_idx) (void);

gdb/gdbserver/linux-x86-low.c

@@ -991,25 +991,19 @@ x86_arch_setup (void)
    code.  This should only be called if LWP got a SYSCALL_SIGTRAP.  */
 
 static void
-x86_get_syscall_trapinfo (struct regcache *regcache, int *sysno, int *sysret)
+x86_get_syscall_trapinfo (struct regcache *regcache, int *sysno)
 {
   int use_64bit = register_size (regcache->tdesc, 0) == 8;
 
   if (use_64bit)
     {
       long l_sysno;
-      long l_sysret;
 
       collect_register_by_name (regcache, "orig_rax", &l_sysno);
-      collect_register_by_name (regcache, "rax", &l_sysret);
       *sysno = (int) l_sysno;
-      *sysret = (int) l_sysret;
     }
   else
-    {
+    collect_register_by_name (regcache, "orig_eax", sysno);
-      collect_register_by_name (regcache, "orig_eax", sysno);
-      collect_register_by_name (regcache, "eax", sysret);
-    }
 }
 
 static int