Ensure that a serial port is set up before used.

stage2/builtins.c

@@ -3914,9 +3914,18 @@ terminal_func (char *arg, int flags)
 #ifdef SUPPORT_SERIAL
       else if (grub_memcmp (arg, "serial", sizeof ("serial") - 1) == 0)
 	{
-	  terminal |= TERMINAL_SERIAL;
-	  if (! default_terminal)
-	    default_terminal = TERMINAL_SERIAL;
+	  if (serial_exists ())
+	    {
+	      terminal |= TERMINAL_SERIAL;
+	      if (! default_terminal)
+		default_terminal = TERMINAL_SERIAL;
+	    }
+	  else
+	    {
+	      terminal = saved_terminal;
+	      errnum = ERR_NEED_SERIAL;
+	      return 1;
+	    }
 	}
 #endif /* SUPPORT_SERIAL */
       else

stage2/common.c

@@ -2,7 +2,7 @@
 /*
  *  GRUB  --  GRand Unified Bootloader
  *  Copyright (C) 1996  Erich Boleyn  <erich@uruk.org>
- *  Copyright (C) 1999, 2000  Free Software Foundation, Inc.
+ *  Copyright (C) 1999, 2000, 2001  Free Software Foundation, Inc.
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -73,6 +73,7 @@ char *err_list[] =
   [ERR_GEOM] = "Selected cylinder exceeds maximum supported by BIOS",
   [ERR_NEED_LX_KERNEL] = "Linux kernel must be loaded before initrd",
   [ERR_NEED_MB_KERNEL] = "Multiboot kernel must be loaded before modules",
+  [ERR_NEED_SERIAL] = "Serial device not configured",
   [ERR_NO_DISK] = "Selected disk does not exist",
   [ERR_NO_PART] = "No such partition",
   [ERR_NUMBER_PARSING] = "Error while parsing number",

stage2/serial.c

@@ -1,7 +1,7 @@
 /* serial.c - serial device interface */
 /*
  *  GRUB  --  GRand Unified Bootloader
- *  Copyright (C) 2000  Free Software Foundation, Inc.
+ *  Copyright (C) 2000, 2001  Free Software Foundation, Inc.
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -31,7 +31,7 @@ struct divisor
 };
 
 /* Store the port number of a serial unit.  */
-static unsigned short serial_port;
+static unsigned short serial_port = -1;
 
 /* The table which lists common configurations.  */
 static struct divisor divisor_tab[] =
@@ -102,6 +102,13 @@ serial_putchar (int c)
   outb (serial_port + UART_TX, c);
 }
 
+/* Check if a serial port is set up.  */
+int
+serial_exists (void)
+{
+  return serial_port != -1;
+}
+
 /* Return the port number for the UNITth serial device.  */
 unsigned short
 serial_get_port (int unit)

stage2/serial.h

@@ -1,7 +1,7 @@
 /* serial.h - serial device interface */
 /*
  *  GRUB  --  GRand Unified Bootloader
- *  Copyright (C) 2000  Free Software Foundation, Inc.
+ *  Copyright (C) 2000, 2001  Free Software Foundation, Inc.
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -93,6 +93,9 @@ unsigned short serial_get_port (int unit);
 int serial_init (unsigned short port, unsigned int speed,
 		 int word_len, int parity, int stop_bit_len);
 
+/* Check if a serial port is set up.  */
+int serial_exists (void);
+
 #ifdef GRUB_UTIL
 /* Set the file name of a serial device (or a pty device). This is a
    function specific to the grub shell.  */

stage2/shared.h

@@ -541,6 +541,7 @@ typedef enum
   ERR_BAD_ARGUMENT,
   ERR_UNALIGNED,
   ERR_PRIVILEGED,
+  ERR_NEED_SERIAL,
 
   MAX_ERR_NUM
 } grub_error_t;