grub/asmstub.c

/* asmstub.c - a version of shared_src/asm.S that works under Unix */
/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 1999, 2000  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
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/* Try to use glibc's transparant LFS support. */
#define _LARGEFILE_SOURCE	1
/* lseek becomes synonymous with lseek64.  */
#define _FILE_OFFSET_BITS	64

/* Simulator entry point. */
int grub_stage2 (void);

#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <assert.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <time.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <setjmp.h>
#include <sys/time.h>
#include <termios.h>

#ifdef __linux__
# include <sys/ioctl.h>		/* ioctl */
# if !defined(__GLIBC__) || \
	((__GLIBC__ < 2) || ((__GLIBC__ == 2) && (__GLIBC_MINOR__ < 1)))
/* Maybe libc doesn't have large file support.  */
#  include <linux/unistd.h>	/* _llseek */
# endif /* (GLIBC < 2) || ((__GLIBC__ == 2) && (__GLIBC_MINOR < 1)) */
# ifndef BLKFLSBUF
#  define BLKFLSBUF	_IO (0x12,97)	/* flush buffer cache */
# endif /* ! BLKFLSBUF */
#endif /* __linux__ */

/* We want to prevent any circularararity in our stubs, as well as
   libc name clashes. */
#define WITHOUT_LIBC_STUBS 1
#include <shared.h>
#include <device.h>
#include <serial.h>

/* Simulated memory sizes. */
#define EXTENDED_MEMSIZE (3 * 1024 * 1024)	/* 3MB */
#define CONVENTIONAL_MEMSIZE (640 * 1024)	/* 640kB */

unsigned long install_partition = 0x20000;
unsigned long boot_drive = 0;
int saved_entryno = 0;
char version_string[] = VERSION;
char config_file[128] = "/boot/grub/menu.lst"; /* FIXME: arbitrary */
unsigned long linux_text_len = 0;

/* Emulation requirements. */
char *grub_scratch_mem = 0;

struct geometry *disks = 0;

/* The map between BIOS drives and UNIX device file names.  */
char **device_map = 0;

/* The jump buffer for exiting correctly.  */
static jmp_buf env_for_exit;

/* The file descriptor for a serial device.  */
static int serial_fd = -1;

/* The file name of a serial device.  */
static char *serial_device = 0;

#ifdef SIMULATE_SLOWNESS_OF_SERIAL
/* The speed of a serial device.  */
static unsigned int serial_speed;
#endif /* SIMULATE_SLOWNESS_OF_SERIAL */

/* The main entry point into this mess. */
int
grub_stage2 (void)
{
  /* These need to be static, because they survive our stack transitions. */
  static int status = 0;
  static char *realstack;
  char *scratch, *simstack;
  int i;

  /* We need a nested function so that we get a clean stack frame,
     regardless of how the code is optimized. */
  static volatile void doit ()
  {
    /* Make sure our stack lives in the simulated memory area. */
    asm volatile ("movl %%esp, %0\n\tmovl %1, %%esp\n"
		  : "=&r" (realstack) : "r" (simstack));

    /* Do a setjmp here for the stop command.  */
    if (! setjmp (env_for_exit))
      {
	/* Actually enter the generic stage2 code.  */
	status = 0;
	init_bios_info ();
      }
    else
      {
	/* If ERRNUM is non-zero, then set STATUS to non-zero.  */
	if (errnum)
	  status = 1;
      }

    /* Replace our stack before we use any local variables. */
    asm volatile ("movl %0, %%esp\n" : : "r" (realstack));
  }

  assert (grub_scratch_mem == 0);
  scratch = malloc (0x100000 + EXTENDED_MEMSIZE + 15);
  assert (scratch);
  grub_scratch_mem = (char *) ((((int) scratch) >> 4) << 4);

  /* FIXME: simulate the memory holes using mprot, if available. */

  assert (disks == 0);
  disks = malloc (NUM_DISKS * sizeof (*disks));
  assert (disks);
  /* Initialize DISKS.  */
  for (i = 0; i < NUM_DISKS; i++)
    disks[i].flags = -1;

  if (! init_device_map (&device_map, device_map_file, floppy_disks))
    return 1;
  
  /* Check some invariants. */
  assert ((SCRATCHSEG << 4) == SCRATCHADDR);
  assert ((BUFFERSEG << 4) == BUFFERADDR);
  assert (BUFFERADDR + BUFFERLEN == SCRATCHADDR);
  assert (FSYS_BUF % 16 == 0);
  assert (FSYS_BUF + FSYS_BUFLEN == BUFFERADDR);

#ifdef HAVE_LIBCURSES
  /* Get into char-at-a-time mode. */
  if (use_curses)
    {
      initscr ();
      cbreak ();
      noecho ();
      nonl ();
      scrollok (stdscr, TRUE);
      keypad (stdscr, TRUE);
      wtimeout (stdscr, 100);
    }
#endif

  /* Make sure that actual writing is done.  */
  sync ();

  /* Set our stack, and go for it. */
  simstack = (char *) PROTSTACKINIT;
  doit ();

  /* I don't know if this is necessary really.  */
  sync ();

#ifdef HAVE_LIBCURSES
  if (use_curses)
    endwin ();
#endif

  /* Close off the file descriptors we used. */
  for (i = 0; i < NUM_DISKS; i ++)
    if (disks[i].flags != -1)
      {
#ifdef __linux__
	/* In Linux, invalidate the buffer cache. In other OSes, reboot
	   is one of the solutions...  */
	ioctl (disks[i].flags, BLKFLSBUF, 0);
#else
# warning "In your operating system, the buffer cache will not be flushed."
#endif
	close (disks[i].flags);
      }

  if (serial_fd >= 0)
    close (serial_fd);
  
  /* Release memory. */
  restore_device_map (device_map);
  device_map = 0;
  free (disks);
  disks = 0;
  free (scratch);
  grub_scratch_mem = 0;

  if (serial_device)
    free (serial_device);
  serial_device = 0;
  
  /* Ahh... at last we're ready to return to caller. */
  return status;
}

/* Assign DRIVE to a device name DEVICE.  */
void
assign_device_name (int drive, const char *device)
{
  /* If DRIVE is already assigned, free it.  */
  if (device_map[drive])
    free (device_map[drive]);

  /* If the old one is already opened, close it.  */
  if (disks[drive].flags != -1)
    {
      close (disks[drive].flags);
      disks[drive].flags = -1;
    }

  /* Assign DRIVE to DEVICE.  */
  if (! device)
    device_map[drive] = 0;
  else
    device_map[drive] = strdup (device);
}

void
stop (void)
{
#ifdef HAVE_LIBCURSES
  if (use_curses)
    endwin ();
#endif

  /* Jump to doit.  */
  longjmp (env_for_exit, 1);
}

void
grub_reboot (void)
{
  stop ();
}

void
grub_halt (int no_apm)
{
  stop ();
}

/* calls for direct boot-loader chaining */
void
chain_stage1 (unsigned long segment, unsigned long offset,
	      unsigned long part_table_addr)
{
  stop ();
}


void
chain_stage2 (unsigned long segment, unsigned long offset)
{
  stop ();
}


/* do some funky stuff, then boot linux */
void
linux_boot (void)
{
  stop ();
}


/* For bzImage kernels. */
void
big_linux_boot (void)
{
  stop ();
}


/* booting a multiboot executable */
void
multi_boot (int start, int mb_info)
{
  stop ();
}

/* sets it to linear or wired A20 operation */
void
gateA20 (int linear)
{
  /* Nothing to do in the simulator. */
}

/* Set up the int15 handler.  */
void
set_int15_handler (void)
{
  /* Nothing to do in the simulator.  */
}

/* Restore the original int15 handler.  */
void
unset_int15_handler (void)
{
  /* Nothing to do in the simulator.  */
}

/* The key map.  */
unsigned short bios_key_map[KEY_MAP_SIZE + 1];
unsigned short ascii_key_map[KEY_MAP_SIZE + 1];

/* Copy MAP to the drive map and set up the int13 handler.  */
void
set_int13_handler (unsigned short *map)
{
  /* Nothing to do in the simulator.  */
}

int
get_code_end (void)
{
  /* Just return a little area for simulation. */
  return BOOTSEC_LOCATION + (60 * 1024);
}


/* memory probe routines */
int
get_memsize (int type)
{
  if (! type)
    return CONVENTIONAL_MEMSIZE >> 10;
  else
    return EXTENDED_MEMSIZE >> 10;
}


/* get_eisamemsize() :  return packed EISA memory map, lower 16 bits is
 *		memory between 1M and 16M in 1K parts, upper 16 bits is
 *		memory above 16M in 64K parts.  If error, return -1.
 */
int
get_eisamemsize (void)
{
  return (EXTENDED_MEMSIZE >> 10);
}


#define MMAR_DESC_TYPE_AVAILABLE 1 /* available to OS */
#define MMAR_DESC_TYPE_RESERVED 2 /* not available */
#define MMAR_DESC_TYPE_ACPI_RECLAIM 3 /* usable by OS after reading ACPI */
#define MMAR_DESC_TYPE_ACPI_NVS 4 /* required to save between NVS sessions */

#define MMAR_DESC_LENGTH	20

/* Fetch the next entry in the memory map and return the continuation
   value.  DESC is a pointer to the descriptor buffer, and CONT is the
   previous continuation value (0 to get the first entry in the
   map).  */
int
get_mmap_entry (struct mmar_desc *desc, int cont)
{
  /* Record the memory map statically.  */
  static struct mmar_desc desc_table[] =
  {
    /* The conventional memory.  */
    {
      MMAR_DESC_LENGTH,
      0,
      CONVENTIONAL_MEMSIZE,
      MMAR_DESC_TYPE_AVAILABLE
    },
    /* BIOS RAM and ROM (such as video memory).  */
    {
      MMAR_DESC_LENGTH,
      CONVENTIONAL_MEMSIZE,
      0x100000 - CONVENTIONAL_MEMSIZE,
      MMAR_DESC_TYPE_RESERVED
    },
    /* The extended memory.  */
    {
      MMAR_DESC_LENGTH,
      0x100000,
      EXTENDED_MEMSIZE,
      MMAR_DESC_TYPE_AVAILABLE
    }
  };
  
  int num = sizeof (desc_table) / sizeof (*desc_table);

  if (cont < 0 || cont >= num)
    {
      /* Should not happen.  */
      desc->desc_len = 0;
    }
  else
    {
      /* Copy the entry.  */
      *desc = desc_table[cont++];

      /* If the next entry exists, return the index.  */
      if (cont < num)
	return cont;
    }
  
  return 0;
}


/* low-level timing info */
int
getrtsecs (void)
{
  /* FIXME: exact value is not important, so just return time_t for now. */
  return time (0);
}

int
currticks (void)
{
  struct timeval tv;
  long csecs;
  int ticks_per_csec, ticks_per_usec;

  /* Note: 18.2 ticks/sec.  */

  /* Get current time.  */
  gettimeofday (&tv, 0);

  /* Compute centiseconds.  */
  csecs = tv.tv_sec / 10;

  /* Ticks per centisecond.  */
  ticks_per_csec = csecs * 182;

  /* Ticks per microsecond.  */
  ticks_per_usec = (((tv.tv_sec - csecs * 10) * 1000000 + tv.tv_usec)
		    * 182 / 10000000);

  /* Sum them.  */
  return ticks_per_csec + ticks_per_usec;
}

/* low-level character I/O */
void
console_cls (void)
{
#ifdef HAVE_LIBCURSES
  if (use_curses)
    clear ();
#endif
}


/* returns packed values, LSB+1 is x, LSB is y */
int
console_getxy (void)
{
  int y, x;
#ifdef HAVE_LIBCURSES
  if (use_curses)
    getyx (stdscr, y, x);
  else
#endif
  y = x = 0;
  return (x << 8) | (y & 0xff);
}


void
console_gotoxy (int x, int y)
{
#ifdef HAVE_LIBCURSES
  if (use_curses)
    move (y, x);
#endif
}

/* displays an ASCII character.  IBM displays will translate some
   characters to special graphical ones */
void
console_putchar (int c)
{
#ifdef HAVE_LIBCURSES
  if (use_curses)
    {
      /* In ncurses, a newline is treated badly, so we emulate it in our
	 own way.  */
      if (c == '\n')
	{
	  int x, y;

	  getyx (stdscr, y, x);
	  if (y + 1 == LINES)
	    scroll (stdscr);
	  else
	    move (y + 1, x);
	}
      else
	{
	  addch (c);
#ifdef REFRESH_IMMEDIATELY
	  refresh ();
#endif
	}
    }
  else
#endif
  putchar (c);
}


/* The store for ungetch simulation. This is necessary, because
   ncurses-1.9.9g is still used in the world and its ungetch is
   completely broken.  */
#ifdef HAVE_LIBCURSES
static int save_char = ERR;
#endif

/* returns packed BIOS/ASCII code */
int
console_getkey (void)
{
  int c;

#ifdef HAVE_LIBCURSES
  if (use_curses)
    {
      /* If checkkey has already got a character, then return it.  */
      if (save_char != ERR)
	{
	  c = save_char;
	  save_char = ERR;
	  return c;
	}

      wtimeout (stdscr, -1);
      c = getch ();
      wtimeout (stdscr, 100);
    }
  else
#endif
    c = getchar ();

  /* Quit if we get EOF. */
  if (c == -1)
    stop ();
  return c;
}


/* like 'getkey', but doesn't wait, returns -1 if nothing available */
int
console_checkkey (void)
{
#ifdef HAVE_LIBCURSES
  if (use_curses)
    {
      int c;

      /* Check for SAVE_CHAR. This should not be true, because this
	 means checkkey is called twice continuously.  */
      if (save_char != ERR)
	return save_char;

      c = getch ();
      /* If C is not ERR, then put it back in the input queue.  */
      if (c != ERR)
	save_char = c;
      return c;
    }
#endif

  /* Just pretend they hit the space bar, then read the real key when
     they call getkey. */
  return ' ';
}


/* sets text mode character attribute at the cursor position */
void
set_attrib (int attr)
{
#ifdef HAVE_LIBCURSES
  if (use_curses)
    {
      /* FIXME: I don't know why, but chgat doesn't work as expected, so
	 use this dirty way... - okuji  */
      chtype ch = inch ();
      addch ((ch & A_CHARTEXT) | attr);
# if 0
      chgat (1, attr, 0, NULL);
# endif
    }
#endif
}

/* Low-level disk I/O.  Our stubbed version just returns a file
   descriptor, not the actual geometry. */
int
get_diskinfo (int drive, struct geometry *geometry)
{
  /* FIXME: this function is truly horrid.  We try opening the device,
     then severely abuse the GEOMETRY->flags field to pass a file
     descriptor to biosdisk.  Thank God nobody's looking at this comment,
     or my reputation would be ruined. --Gord */

  /* See if we have a cached device. */
  if (disks[drive].flags == -1)
    {
      /* The unpartitioned device name: /dev/XdX */
      char *devname = device_map[drive];
      char buf[512];

      if (! devname)
	return -1;

      if (verbose)
	grub_printf ("Attempt to open drive 0x%x (%s)\n",
		     drive, devname);

      /* Open read/write, or read-only if that failed. */
      if (! read_only)
	disks[drive].flags = open (devname, O_RDWR);

      if (disks[drive].flags == -1)
	{
	  if (read_only || errno == EACCES || errno == EROFS)
	    {
	      disks[drive].flags = open (devname, O_RDONLY);
	      if (disks[drive].flags == -1)
		{
		  assign_device_name (drive, 0);
		  return -1;
		}
	    }
	  else
	    {
	      assign_device_name (drive, 0);
	      return -1;
	    }
	}

      /* Attempt to read the first sector.  */
      if (read (disks[drive].flags, buf, 512) != 512)
	{
	  close (disks[drive].flags);
	  disks[drive].flags = -1;
	  assign_device_name (drive, 0);
	  return -1;
	}

      if (disks[drive].flags != -1)
	get_drive_geometry (&disks[drive], device_map, drive);
    }

  if (disks[drive].flags == -1)
    return -1;

#ifdef __linux__
  /* In Linux, invalidate the buffer cache, so that left overs
     from other program in the cache are flushed and seen by us */
  ioctl (disks[drive].flags, BLKFLSBUF, 0);
#endif

  *geometry = disks[drive];
  return 0;
}

/* Read LEN bytes from FD in BUF. Return less than or equal to zero if an
   error occurs, otherwise return LEN.  */
static int
nread (int fd, char *buf, size_t len)
{
  int size = len;

  while (len)
    {
      int ret = read (fd, buf, len);

      if (ret <= 0)
	{
	  if (errno == EINTR)
	    continue;
	  else
	    return ret;
	}

      len -= ret;
      buf += ret;
    }

  return size;
}

/* Write LEN bytes from BUF to FD. Return less than or equal to zero if an
   error occurs, otherwise return LEN.  */
static int
nwrite (int fd, char *buf, size_t len)
{
  int size = len;

  while (len)
    {
      int ret = write (fd, buf, len);

      if (ret <= 0)
	{
	  if (errno == EINTR)
	    continue;
	  else
	    return ret;
	}

      len -= ret;
      buf += ret;
    }

  return size;
}

/* Dump BUF in the format of hexadecimal numbers.  */
static void
hex_dump (void *buf, size_t size)
{
  /* FIXME: How to determine which length is readable?  */
#define MAX_COLUMN	70

  /* use unsigned char for numerical computations */
  unsigned char *ptr = buf;
  /* count the width of the line */
  int column = 0;
  /* how many bytes written */
  int count = 0;

  while (size > 0)
    {
      /* high 4 bits */
      int hi = *ptr >> 4;
      /* low 4 bits */
      int low = *ptr & 0xf;

      /* grub_printf does not handle prefix number, such as %2x, so
	 format the number by hand...  */
      grub_printf ("%x%x", hi, low);
      column += 2;
      count++;
      ptr++;
      size--;

      /* Insert space or newline with the interval 4 bytes.  */
      if (size != 0 && (count % 4) == 0)
	{
	  if (column < MAX_COLUMN)
	    {
	      grub_printf (" ");
	      column++;
	    }
	  else
	    {
	      grub_printf ("\n");
	      column = 0;
	    }
	}
    }

  /* Add a newline at the end for readability.  */
  grub_printf ("\n");
}

int
biosdisk (int subfunc, int drive, struct geometry *geometry,
	  int sector, int nsec, int segment)
{
  char *buf;
  int fd = geometry->flags;

  /* Get the file pointer from the geometry, and make sure it matches. */
  if (fd == -1 || fd != disks[drive].flags)
    return BIOSDISK_ERROR_GEOMETRY;

  /* Seek to the specified location. */
#if defined(__linux__) && (!defined(__GLIBC__) || \
	((__GLIBC__ < 2) || ((__GLIBC__ == 2) && (__GLIBC_MINOR__ < 1))))
  /* Maybe libc doesn't have large file support.  */
  {
    loff_t offset, result;
    static int _llseek (uint filedes, ulong hi, ulong lo,
			loff_t *res, uint wh);
    _syscall5 (int, _llseek, uint, filedes, ulong, hi, ulong, lo,
	       loff_t *, res, uint, wh);

    offset = (loff_t) sector * (loff_t) SECTOR_SIZE;
    if (_llseek (fd, offset >> 32, offset & 0xffffffff, &result, SEEK_SET))
      return -1;
  }
#else
  {
    off_t offset = (off_t) sector * (off_t) SECTOR_SIZE;

    if (lseek (fd, offset, SEEK_SET) != offset)
      return -1;
  }
#endif

  buf = (char *) (segment << 4);

  switch (subfunc)
    {
    case BIOSDISK_READ:
      if (nread (fd, buf, nsec * SECTOR_SIZE) != nsec * SECTOR_SIZE)
	return -1;
      break;

    case BIOSDISK_WRITE:
      if (verbose)
	{
	  grub_printf ("Write %d sectors starting from %d sector"
		       " to drive 0x%x (%s)\n",
		       nsec, sector, drive, device_map[drive]);
	  hex_dump (buf, nsec * SECTOR_SIZE);
	}
      if (! read_only)
	if (nwrite (fd, buf, nsec * SECTOR_SIZE) != nsec * SECTOR_SIZE)
	  return -1;
      break;

    default:
      grub_printf ("unknown subfunc %d\n", subfunc);
      break;
    }

  return 0;
}


void
stop_floppy (void)
{
  /* NOTUSED */
}

/* The serial version of getkey.  */
int
serial_getkey (void)
{
  char c;
#ifdef SIMULATE_SLOWNESS_OF_SERIAL
  struct timeval otv, tv;

  gettimeofday (&otv, 0);
#endif /* SIMULATE_SLOWNESS_OF_SERIAL */
  
  if (nread (serial_fd, &c, 1) != 1)
    stop ();

#ifdef SIMULATE_SLOWNESS_OF_SERIAL
  while (1)
    {
      long delta;
      
      gettimeofday (&tv, 0);
      delta = tv.tv_usec - otv.tv_usec;
      if (delta < 0)
	delta += 1000000;
      
      if (delta >= 1000000 / (serial_speed >> 3))
	break;
    }
#endif /* SIMULATE_SLOWNESS_OF_SERIAL */
  
  return c;
}

/* The serial version of checkkey.  */
int
serial_checkkey (void)
{
  fd_set fds;
  struct timeval to;

  /* Wait only for the serial device.  */
  FD_ZERO (&fds);
  FD_SET (serial_fd, &fds);

  /* Set the timeout to 100ms.  */
  to.tv_sec = 0;
  to.tv_usec = 100000;
  
  return select (serial_fd + 1, &fds, 0, 0, &to) > 0 ? : -1;
}

/* The serial version of grub_putchar.  */
void
serial_putchar (int c)
{
  char ch = (char) c;
#ifdef SIMULATE_SLOWNESS_OF_SERIAL
  struct timeval otv, tv;
  
  gettimeofday (&otv, 0);
#endif /* SIMULATE_SLOWNESS_OF_SERIAL */
  
  if (nwrite (serial_fd, &ch, 1) != 1)
    stop ();
  
#ifdef SIMULATE_SLOWNESS_OF_SERIAL
  while (1)
    {
      long delta;
      
      gettimeofday (&tv, 0);
      delta = tv.tv_usec - otv.tv_usec;
      if (delta < 0)
	delta += 1000000;
      
      if (delta >= 1000000 / (serial_speed >> 3))
	break;
    }
#endif /* SIMULATE_SLOWNESS_OF_SERIAL */
}

static speed_t
get_termios_speed (int speed)
{
  switch (speed)
    {
    case 2400: return B2400;
    case 4800: return B4800;
    case 9600: return B9600;
    case 19200: return B19200;
    case 38400: return B38400;
#ifdef B57600
    case 57600: return B57600;
#endif
#ifdef B115200      
    case 115200: return B115200;
#endif
    }

  return B0;
}

/* Get the port number of the unit UNIT. In the grub shell, this doesn't
   make sense.  */
unsigned short
serial_get_port (int unit)
{
  return 0;
}

/* Initialize a serial device. In the grub shell, PORT is unused.  */
int
serial_init (unsigned short port, unsigned int speed,
	     int word_len, int parity, int stop_bit_len)
{
  struct termios termios;
  speed_t termios_speed;
  
  /* Check if the file name is specified.  */
  if (! serial_device)
    return 0;

  /* If a serial device is already opened, close it first.  */
  if (serial_fd >= 0)
    close (serial_fd);
  
  /* Open the device file.  */
  serial_fd = open (serial_device, O_RDWR | O_NOCTTY | O_SYNC);
  if (serial_fd < 0)
    return 0;

  /* Get the termios parameters.  */
  if (tcgetattr (serial_fd, &termios))
    goto fail;

  /* Raw mode.  */
  cfmakeraw (&termios);

  /* Set the speed.  */
  termios_speed = get_termios_speed (speed);
  if (termios_speed == B0)
    goto fail;
  
  cfsetispeed (&termios, termios_speed);
  cfsetospeed (&termios, termios_speed);

  /* Set the word length.  */
  termios.c_cflag &= ~CSIZE;
  switch (word_len)
    {
    case UART_5BITS_WORD:
      termios.c_cflag |= CS5;
      break;
    case UART_6BITS_WORD:
      termios.c_cflag |= CS6;
      break;
    case UART_7BITS_WORD:
      termios.c_cflag |= CS7;
      break;
    case UART_8BITS_WORD:
      termios.c_cflag |= CS8;
      break;
    default:
      goto fail;
    }

  /* Set the parity.  */
  switch (parity)
    {
    case UART_NO_PARITY:
      termios.c_cflag &= ~PARENB;
      break;
    case UART_ODD_PARITY:
      termios.c_cflag |= PARENB;
      termios.c_cflag |= PARODD;
      break;
    case UART_EVEN_PARITY:
      termios.c_cflag |= PARENB;
      termios.c_cflag &= ~PARODD;
      break;
    default:
      goto fail;
    }

  /* Set the length of stop bit.  */
  switch (stop_bit_len)
    {
    case UART_1_STOP_BIT:
      termios.c_cflag &= ~CSTOPB;
      break;
    case UART_2_STOP_BITS:
      termios.c_cflag |= CSTOPB;
      break;
    default:
      goto fail;
    }

  /* Set the parameters.  */
  if (tcsetattr (serial_fd, TCSANOW, &termios))
    goto fail;

#ifdef SIMULATE_SLOWNESS_OF_SERIAL
  serial_speed = speed;
#endif /* SIMUATE_SLOWNESS_OF_SERIAL */
  
  return 1;

 fail:
  close (serial_fd);
  serial_fd = -1;
  return 0;
}

/* Set the file name of a serial device (or a pty device). This is a
   function specific to the grub shell.  */
void
set_serial_device (const char *device)
{
  if (serial_device)
    free (serial_device);
  
  serial_device = strdup (device);
}