gdbserver: Ensure all debug output uses debug functions

All debug output needs to go via debug functions to ensure it writes to the
correct output stream.

gdb/ChangeLog:

	* nat/linux-waitpid.c (linux_debug): Call debug_vprintf.

gdb/gdbserver/ChangeLog:

	* ax.c (ax_vdebug): Call debug_printf.
	* debug.c (debug_write): New function.
	* debug.h (debug_write): New declaration.
	* linux-low.c (sigchld_handler): Call debug_write.

gdb/ChangeLog

@@ -1,3 +1,7 @@
+2019-04-17  Alan Hayward  <alan.hayward@arm.com>
+
+	* nat/linux-waitpid.c (linux_debug): Call debug_vprintf.
+
 2019-04-17  Jim Wilson  <jimw@sifive.com>
 	    Andrew Burgess  <andrew.burgess@embecosm.com>
 

gdb/gdbserver/ChangeLog

@@ -1,3 +1,10 @@
+2019-04-17  Alan Hayward  <alan.hayward@arm.com>
+
+	* ax.c (ax_vdebug): Call debug_printf.
+	* debug.c (debug_write): New function.
+	* debug.h (debug_write): New declaration.
+	* linux-low.c (sigchld_handler): Call debug_write.
+
 2019-04-17  Alan Hayward  <alan.hayward@arm.com>
 
 	* debug.c (debug_set_output): New function.

gdb/gdbserver/ax.c

@@ -36,7 +36,11 @@ ax_vdebug (const char *fmt, ...)
 
   va_start (ap, fmt);
   vsprintf (buf, fmt, ap);
+#ifdef IN_PROCESS_AGENT
   fprintf (stderr, PROG "/ax: %s\n", buf);
+#else
+  debug_printf (PROG "/ax: %s\n", buf);
+#endif
   va_end (ap);
 }
 

gdb/gdbserver/debug.c

@@ -130,3 +130,12 @@ do_debug_exit (const char *function_name)
   if (function_name != NULL)
     debug_printf ("<<<< exiting %s\n", function_name);
 }
+
+/* See debug.h.  */
+
+size_t
+debug_write (const void *buf, size_t nbyte)
+{
+  int fd = fileno (debug_file);
+  return write (fd, buf, nbyte);
+}

gdb/gdbserver/debug.h

@@ -35,6 +35,9 @@ void debug_flush (void);
 void do_debug_enter (const char *function_name);
 void do_debug_exit (const char *function_name);
 
+/* Async signal safe debug output function that calls write directly.  */
+size_t debug_write (const void *buf, size_t nbyte);
+
 /* These macros are for use in major functions that produce a lot of
    debugging output.  They help identify in the mass of debugging output
    when these functions enter and exit.  debug_enter is intended to be

gdb/gdbserver/linux-low.c

@@ -6185,10 +6185,9 @@ sigchld_handler (int signo)
     {
       do
 	{
-	  /* fprintf is not async-signal-safe, so call write
-	     directly.  */
-	  if (write (2, "sigchld_handler\n",
-		     sizeof ("sigchld_handler\n") - 1) < 0)
+	  /* Use the async signal safe debug function.  */
+	  if (debug_write ("sigchld_handler\n",
+			   sizeof ("sigchld_handler\n") - 1) < 0)
 	    break; /* just ignore */
 	} while (0);
     }

gdb/nat/linux-waitpid.c

@@ -42,7 +42,7 @@ linux_debug (const char *format, ...)
     {
       va_list args;
       va_start (args, format);
-      vfprintf (stderr, format, args);
+      debug_vprintf (format, args);
       va_end (args);
     }
 #endif