gdb/tui/tuiDisassem.c - third_party/binutils-gdb - Git at Google

 /* Disassembly display.

    Copyright 1998, 1999, 2000, 2001, 2002 Free Software Foundation,
    Inc.

    Contributed by Hewlett-Packard Company.

    This file is part of GDB.

    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., 59 Temple Place - Suite 330,
    Boston, MA 02111-1307, USA.  */

 /* FIXME: cagney/2002-02-28: The GDB coding standard indicates that
    "defs.h" should be included first.  Unfortunatly some systems
    (currently Debian GNU/Linux) include the <stdbool.h> via <curses.h>
    and they clash with "bfd.h"'s definiton of true/false.  The correct
    fix is to remove true/false from "bfd.h", however, until that
    happens, hack around it by including "config.h" and <curses.h>
    first.  */

 #include "config.h"
 #ifdef HAVE_NCURSES_H
 #include <ncurses.h>
 #else
 #ifdef HAVE_CURSES_H
 #include <curses.h>
 #endif
 #endif

 #include "defs.h"
 #include "symtab.h"
 #include "breakpoint.h"
 #include "frame.h"
 #include "value.h"
 #include "source.h"

 #include "tui.h"
 #include "tuiData.h"
 #include "tuiWin.h"
 #include "tuiLayout.h"
 #include "tuiSourceWin.h"
 #include "tuiStack.h"
 #include "tui-file.h"

 struct tui_asm_line
 {
   CORE_ADDR addr;
   char* addr_string;
   char* insn;
 };

 /* Function to set the disassembly window's content.
    Disassemble count lines starting at pc.
    Return address of the count'th instruction after pc.  */
 static CORE_ADDR
 tui_disassemble (struct tui_asm_line* lines, CORE_ADDR pc, int count)
 {
   struct ui_file *gdb_dis_out;
   disassemble_info asm_info;

   /* now init the ui_file structure */
   gdb_dis_out = tui_sfileopen (256);

   memcpy (&asm_info, TARGET_PRINT_INSN_INFO, sizeof (asm_info));
   asm_info.stream = gdb_dis_out;

   if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
     asm_info.endian = BFD_ENDIAN_BIG;
   else
     asm_info.endian = BFD_ENDIAN_LITTLE;

   if (TARGET_ARCHITECTURE != NULL)
     asm_info.mach = TARGET_ARCHITECTURE->mach;

   /* Now construct each line */
   for (; count > 0; count--, lines++)
     {
       if (lines->addr_string)
         xfree (lines->addr_string);
       if (lines->insn)
         xfree (lines->insn);

       print_address (pc, gdb_dis_out);
       lines->addr = pc;
       lines->addr_string = xstrdup (tui_file_get_strbuf (gdb_dis_out));

       ui_file_rewind (gdb_dis_out);

       pc = pc + TARGET_PRINT_INSN (pc, &asm_info);

       lines->insn = xstrdup (tui_file_get_strbuf (gdb_dis_out));

       /* reset the buffer to empty */
       ui_file_rewind (gdb_dis_out);
     }
   ui_file_delete (gdb_dis_out);
   return pc;
 }

 /* Find the disassembly address that corresponds to FROM lines
    above or below the PC.  Variable sized instructions are taken
    into account by the algorithm.  */
 static CORE_ADDR
 tui_find_disassembly_address (CORE_ADDR pc, int from)
 {
   register CORE_ADDR newLow;
   int maxLines;
   int i;
   struct tui_asm_line* lines;

   maxLines = (from > 0) ? from : - from;
   if (maxLines <= 1)
      return pc;

   lines = (struct tui_asm_line*) alloca (sizeof (struct tui_asm_line)
                                          * maxLines);
   memset (lines, 0, sizeof (struct tui_asm_line) * maxLines);

   newLow = pc;
   if (from > 0)
     {
       tui_disassemble (lines, pc, maxLines);
       newLow = lines[maxLines - 1].addr;
     }
   else
     {
       CORE_ADDR last_addr;
       int pos;
       struct minimal_symbol* msymbol;

       /* Find backward an address which is a symbol
          and for which disassembling from that address will fill
          completely the window.  */
       pos = maxLines - 1;
       do {
          newLow -= 1 * maxLines;
          msymbol = lookup_minimal_symbol_by_pc_section (newLow, 0);

          if (msymbol)
             newLow = SYMBOL_VALUE_ADDRESS (msymbol);
          else
             newLow += 1 * maxLines;

          tui_disassemble (lines, newLow, maxLines);
          last_addr = lines[pos].addr;
       } while (last_addr > pc && msymbol);

       /* Scan forward disassembling one instruction at a time
          until the last visible instruction of the window
          matches the pc.  We keep the disassembled instructions
          in the 'lines' window and shift it downward (increasing
          its addresses).  */
       if (last_addr < pc)
         do
           {
             CORE_ADDR next_addr;

             pos++;
             if (pos >= maxLines)
               pos = 0;

             next_addr = tui_disassemble (&lines[pos], last_addr, 1);

             /* If there are some problems while disassembling exit.  */
             if (next_addr <= last_addr)
               break;
             last_addr = next_addr;
           } while (last_addr <= pc);
       pos++;
       if (pos >= maxLines)
          pos = 0;
       newLow = lines[pos].addr;
     }
   for (i = 0; i < maxLines; i++)
     {
       xfree (lines[i].addr_string);
       xfree (lines[i].insn);
     }
   return newLow;
 }

 /* Function to set the disassembly window's content.  */
 TuiStatus
 tuiSetDisassemContent (CORE_ADDR pc)
 {
   TuiStatus ret = TUI_FAILURE;
   register int i;
   register int offset = disassemWin->detail.sourceInfo.horizontalOffset;
   register int lineWidth, maxLines;
   CORE_ADDR cur_pc;
   TuiGenWinInfoPtr locator = locatorWinInfoPtr ();
   int tab_len = tuiDefaultTabLen ();
   struct tui_asm_line* lines;
   int insn_pos;
   int addr_size, max_size;
   char* line;

   if (pc == 0)
     return TUI_FAILURE;

   ret = tuiAllocSourceBuffer (disassemWin);
   if (ret != TUI_SUCCESS)
     return ret;

   disassemWin->detail.sourceInfo.startLineOrAddr.addr = pc;
   cur_pc = (CORE_ADDR)
     (((TuiWinElementPtr) locator->content[0])->whichElement.locator.addr);

   maxLines = disassemWin->generic.height - 2;	/* account for hilite */

   /* Get temporary table that will hold all strings (addr & insn).  */
   lines = (struct tui_asm_line*) alloca (sizeof (struct tui_asm_line)
                                          * maxLines);
   memset (lines, 0, sizeof (struct tui_asm_line) * maxLines);

   lineWidth = disassemWin->generic.width - 1;

   tui_disassemble (lines, pc, maxLines);

   /* See what is the maximum length of an address and of a line.  */
   addr_size = 0;
   max_size = 0;
   for (i = 0; i < maxLines; i++)
     {
       size_t len = strlen (lines[i].addr_string);
       if (len > addr_size)
         addr_size = len;

       len = strlen (lines[i].insn) + tab_len;
       if (len > max_size)
         max_size = len;
     }
   max_size += addr_size + tab_len;

   /* Allocate memory to create each line.  */
   line = (char*) alloca (max_size);
   insn_pos = (1 + (addr_size / tab_len)) * tab_len;

   /* Now construct each line */
   for (i = 0; i < maxLines; i++)
     {
       TuiWinElementPtr element;
       TuiSourceElement* src;
       int curLen;

       element = (TuiWinElementPtr) disassemWin->generic.content[i];
       src = &element->whichElement.source;
       strcpy (line, lines[i].addr_string);
       curLen = strlen (line);

       /* Add spaces to make the instructions start on the same column */
       while (curLen < insn_pos)
         {
           strcat (line, " ");
           curLen++;
         }

       strcat (line, lines[i].insn);

       /* Now copy the line taking the offset into account */
       if (strlen (line) > offset)
         strcpy (src->line, &line[offset]);
       else
         src->line[0] = '\0';

       src->lineOrAddr.addr = lines[i].addr;
       src->isExecPoint = lines[i].addr == cur_pc;

       /* See whether there is a breakpoint installed.  */
       src->hasBreak = (!src->isExecPoint
                        && breakpoint_here_p (pc) != no_breakpoint_here);

       xfree (lines[i].addr_string);
       xfree (lines[i].insn);
     }
   disassemWin->generic.contentSize = i;
   return TUI_SUCCESS;
 }


 /*
    ** tuiShowDisassem().
    **        Function to display the disassembly window with disassembled code.
  */
 void
 tuiShowDisassem (CORE_ADDR startAddr)
 {
   struct symtab *s = find_pc_symtab (startAddr);
   TuiWinInfoPtr winWithFocus = tuiWinWithFocus ();
   TuiLineOrAddress val;

   val.addr = startAddr;
   tuiAddWinToLayout (DISASSEM_WIN);
   tuiUpdateSourceWindow (disassemWin, s, val, FALSE);
   /*
      ** if the focus was in the src win, put it in the asm win, if the
      ** source view isn't split
    */
   if (currentLayout () != SRC_DISASSEM_COMMAND && winWithFocus == srcWin)
     tuiSetWinFocusTo (disassemWin);

   return;
 }				/* tuiShowDisassem */


 /*
    ** tuiShowDisassemAndUpdateSource().
    **        Function to display the disassembly window.
  */
 void
 tuiShowDisassemAndUpdateSource (CORE_ADDR startAddr)
 {
   struct symtab_and_line sal;

   tuiShowDisassem (startAddr);
   if (currentLayout () == SRC_DISASSEM_COMMAND)
     {
       TuiLineOrAddress val;

       /*
          ** Update what is in the source window if it is displayed too,
          ** note that it follows what is in the disassembly window and visa-versa
        */
       sal = find_pc_line (startAddr, 0);
       val.lineNo = sal.line;
       tuiUpdateSourceWindow (srcWin, sal.symtab, val, TRUE);
       if (sal.symtab)
 	{
 	  set_current_source_symtab_and_line (&sal);
 	  tuiUpdateLocatorFilename (sal.symtab->filename);
 	}
       else
 	tuiUpdateLocatorFilename ("?");
     }

   return;
 }				/* tuiShowDisassemAndUpdateSource */

 /*
    ** tuiGetBeginAsmAddress().
  */
 CORE_ADDR
 tuiGetBeginAsmAddress (void)
 {
   TuiGenWinInfoPtr locator;
   TuiLocatorElementPtr element;
   CORE_ADDR addr;

   locator = locatorWinInfoPtr ();
   element = &((TuiWinElementPtr) locator->content[0])->whichElement.locator;

   if (element->addr == 0)
     {
       struct minimal_symbol *main_symbol;

       /* Find address of the start of program.
          Note: this should be language specific.  */
       main_symbol = lookup_minimal_symbol ("main", NULL, NULL);
       if (main_symbol == 0)
         main_symbol = lookup_minimal_symbol ("MAIN", NULL, NULL);
       if (main_symbol == 0)
         main_symbol = lookup_minimal_symbol ("_start", NULL, NULL);
       if (main_symbol)
         addr = SYMBOL_VALUE_ADDRESS (main_symbol);
       else
         addr = 0;
     }
   else				/* the target is executing */
     addr = element->addr;

   return addr;
 }				/* tuiGetBeginAsmAddress */

 /* Determine what the low address will be to display in the TUI's
    disassembly window.  This may or may not be the same as the
    low address input.  */
 CORE_ADDR
 tuiGetLowDisassemblyAddress (CORE_ADDR low, CORE_ADDR pc)
 {
   int pos;

   /* Determine where to start the disassembly so that the pc is about in the
      middle of the viewport.  */
   pos = tuiDefaultWinViewportHeight (DISASSEM_WIN, DISASSEM_COMMAND) / 2;
   pc = tui_find_disassembly_address (pc, -pos);

   if (pc < low)
     pc = low;
   return pc;
 }

 /*
    ** tuiVerticalDisassemScroll().
    **      Scroll the disassembly forward or backward vertically
  */
 void
 tuiVerticalDisassemScroll (TuiScrollDirection scrollDirection,
                            int numToScroll)
 {
   if (disassemWin->generic.content != (OpaquePtr) NULL)
     {
       CORE_ADDR pc;
       TuiWinContent content;
       struct symtab *s;
       TuiLineOrAddress val;
       int maxLines, dir;
       struct symtab_and_line cursal = get_current_source_symtab_and_line ();

       content = (TuiWinContent) disassemWin->generic.content;
       if (cursal.symtab == (struct symtab *) NULL)
 	s = find_pc_symtab (deprecated_selected_frame->pc);
       else
 	s = cursal.symtab;

       /* account for hilite */
       maxLines = disassemWin->generic.height - 2;
       pc = content[0]->whichElement.source.lineOrAddr.addr;
       dir = (scrollDirection == FORWARD_SCROLL) ? maxLines : - maxLines;

       val.addr = tui_find_disassembly_address (pc, dir);
       tuiUpdateSourceWindowAsIs (disassemWin, s, val, FALSE);
     }
 }
	/* Disassembly display.

	Copyright 1998, 1999, 2000, 2001, 2002 Free Software Foundation,
	Inc.

	Contributed by Hewlett-Packard Company.

	This file is part of GDB.

	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., 59 Temple Place - Suite 330,
	Boston, MA 02111-1307, USA. */

	/* FIXME: cagney/2002-02-28: The GDB coding standard indicates that
	"defs.h" should be included first. Unfortunatly some systems
	(currently Debian GNU/Linux) include the <stdbool.h> via <curses.h>
	and they clash with "bfd.h"'s definiton of true/false. The correct
	fix is to remove true/false from "bfd.h", however, until that
	happens, hack around it by including "config.h" and <curses.h>
	first. */

	#include "config.h"
	#ifdef HAVE_NCURSES_H
	#include <ncurses.h>
	#else
	#ifdef HAVE_CURSES_H
	#include <curses.h>
	#endif
	#endif

	#include "defs.h"
	#include "symtab.h"
	#include "breakpoint.h"
	#include "frame.h"
	#include "value.h"
	#include "source.h"

	#include "tui.h"
	#include "tuiData.h"
	#include "tuiWin.h"
	#include "tuiLayout.h"
	#include "tuiSourceWin.h"
	#include "tuiStack.h"
	#include "tui-file.h"

	struct tui_asm_line
	{
	CORE_ADDR addr;
	char* addr_string;
	char* insn;
	};

	/* Function to set the disassembly window's content.
	Disassemble count lines starting at pc.
	Return address of the count'th instruction after pc. */
	static CORE_ADDR
	tui_disassemble (struct tui_asm_line* lines, CORE_ADDR pc, int count)
	{
	struct ui_file *gdb_dis_out;
	disassemble_info asm_info;

	/* now init the ui_file structure */
	gdb_dis_out = tui_sfileopen (256);

	memcpy (&asm_info, TARGET_PRINT_INSN_INFO, sizeof (asm_info));
	asm_info.stream = gdb_dis_out;

	if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
	asm_info.endian = BFD_ENDIAN_BIG;
	else
	asm_info.endian = BFD_ENDIAN_LITTLE;

	if (TARGET_ARCHITECTURE != NULL)
	asm_info.mach = TARGET_ARCHITECTURE->mach;

	/* Now construct each line */
	for (; count > 0; count--, lines++)
	{
	if (lines->addr_string)
	xfree (lines->addr_string);
	if (lines->insn)
	xfree (lines->insn);

	print_address (pc, gdb_dis_out);
	lines->addr = pc;
	lines->addr_string = xstrdup (tui_file_get_strbuf (gdb_dis_out));

	ui_file_rewind (gdb_dis_out);

	pc = pc + TARGET_PRINT_INSN (pc, &asm_info);

	lines->insn = xstrdup (tui_file_get_strbuf (gdb_dis_out));

	/* reset the buffer to empty */
	ui_file_rewind (gdb_dis_out);
	}
	ui_file_delete (gdb_dis_out);
	return pc;
	}

	/* Find the disassembly address that corresponds to FROM lines
	above or below the PC. Variable sized instructions are taken
	into account by the algorithm. */
	static CORE_ADDR
	tui_find_disassembly_address (CORE_ADDR pc, int from)
	{
	register CORE_ADDR newLow;
	int maxLines;
	int i;
	struct tui_asm_line* lines;

	maxLines = (from > 0) ? from : - from;
	if (maxLines <= 1)
	return pc;

	lines = (struct tui_asm_line*) alloca (sizeof (struct tui_asm_line)
	* maxLines);
	memset (lines, 0, sizeof (struct tui_asm_line) * maxLines);

	newLow = pc;
	if (from > 0)
	{
	tui_disassemble (lines, pc, maxLines);
	newLow = lines[maxLines - 1].addr;
	}
	else
	{
	CORE_ADDR last_addr;
	int pos;
	struct minimal_symbol* msymbol;

	/* Find backward an address which is a symbol
	and for which disassembling from that address will fill
	completely the window. */
	pos = maxLines - 1;
	do {
	newLow -= 1 * maxLines;
	msymbol = lookup_minimal_symbol_by_pc_section (newLow, 0);

	if (msymbol)
	newLow = SYMBOL_VALUE_ADDRESS (msymbol);
	else
	newLow += 1 * maxLines;

	tui_disassemble (lines, newLow, maxLines);
	last_addr = lines[pos].addr;
	} while (last_addr > pc && msymbol);

	/* Scan forward disassembling one instruction at a time
	until the last visible instruction of the window
	matches the pc. We keep the disassembled instructions
	in the 'lines' window and shift it downward (increasing
	its addresses). */
	if (last_addr < pc)
	do
	{
	CORE_ADDR next_addr;

	pos++;
	if (pos >= maxLines)
	pos = 0;

	next_addr = tui_disassemble (&lines[pos], last_addr, 1);

	/* If there are some problems while disassembling exit. */
	if (next_addr <= last_addr)
	break;
	last_addr = next_addr;
	} while (last_addr <= pc);
	pos++;
	if (pos >= maxLines)
	pos = 0;
	newLow = lines[pos].addr;
	}
	for (i = 0; i < maxLines; i++)
	{
	xfree (lines[i].addr_string);
	xfree (lines[i].insn);
	}
	return newLow;
	}

	/* Function to set the disassembly window's content. */
	TuiStatus
	tuiSetDisassemContent (CORE_ADDR pc)
	{
	TuiStatus ret = TUI_FAILURE;
	register int i;
	register int offset = disassemWin->detail.sourceInfo.horizontalOffset;
	register int lineWidth, maxLines;
	CORE_ADDR cur_pc;
	TuiGenWinInfoPtr locator = locatorWinInfoPtr ();
	int tab_len = tuiDefaultTabLen ();
	struct tui_asm_line* lines;
	int insn_pos;
	int addr_size, max_size;
	char* line;

	if (pc == 0)
	return TUI_FAILURE;

	ret = tuiAllocSourceBuffer (disassemWin);
	if (ret != TUI_SUCCESS)
	return ret;

	disassemWin->detail.sourceInfo.startLineOrAddr.addr = pc;
	cur_pc = (CORE_ADDR)
	(((TuiWinElementPtr) locator->content[0])->whichElement.locator.addr);

	maxLines = disassemWin->generic.height - 2; /* account for hilite */

	/* Get temporary table that will hold all strings (addr & insn). */
	lines = (struct tui_asm_line*) alloca (sizeof (struct tui_asm_line)
	* maxLines);
	memset (lines, 0, sizeof (struct tui_asm_line) * maxLines);

	lineWidth = disassemWin->generic.width - 1;

	tui_disassemble (lines, pc, maxLines);

	/* See what is the maximum length of an address and of a line. */
	addr_size = 0;
	max_size = 0;
	for (i = 0; i < maxLines; i++)
	{
	size_t len = strlen (lines[i].addr_string);
	if (len > addr_size)
	addr_size = len;

	len = strlen (lines[i].insn) + tab_len;
	if (len > max_size)
	max_size = len;
	}
	max_size += addr_size + tab_len;

	/* Allocate memory to create each line. */
	line = (char*) alloca (max_size);
	insn_pos = (1 + (addr_size / tab_len)) * tab_len;

	/* Now construct each line */
	for (i = 0; i < maxLines; i++)
	{
	TuiWinElementPtr element;
	TuiSourceElement* src;
	int curLen;

	element = (TuiWinElementPtr) disassemWin->generic.content[i];
	src = &element->whichElement.source;
	strcpy (line, lines[i].addr_string);
	curLen = strlen (line);

	/* Add spaces to make the instructions start on the same column */
	while (curLen < insn_pos)
	{
	strcat (line, " ");
	curLen++;
	}

	strcat (line, lines[i].insn);

	/* Now copy the line taking the offset into account */
	if (strlen (line) > offset)
	strcpy (src->line, &line[offset]);
	else
	src->line[0] = '\0';

	src->lineOrAddr.addr = lines[i].addr;
	src->isExecPoint = lines[i].addr == cur_pc;

	/* See whether there is a breakpoint installed. */
	src->hasBreak = (!src->isExecPoint
	&& breakpoint_here_p (pc) != no_breakpoint_here);

	xfree (lines[i].addr_string);
	xfree (lines[i].insn);
	}
	disassemWin->generic.contentSize = i;
	return TUI_SUCCESS;
	}


	/*
	** tuiShowDisassem().
	** Function to display the disassembly window with disassembled code.
	*/
	void
	tuiShowDisassem (CORE_ADDR startAddr)
	{
	struct symtab *s = find_pc_symtab (startAddr);
	TuiWinInfoPtr winWithFocus = tuiWinWithFocus ();
	TuiLineOrAddress val;

	val.addr = startAddr;
	tuiAddWinToLayout (DISASSEM_WIN);
	tuiUpdateSourceWindow (disassemWin, s, val, FALSE);
	/*
	** if the focus was in the src win, put it in the asm win, if the
	** source view isn't split
	*/
	if (currentLayout () != SRC_DISASSEM_COMMAND && winWithFocus == srcWin)
	tuiSetWinFocusTo (disassemWin);

	return;
	} /* tuiShowDisassem */


	/*
	** tuiShowDisassemAndUpdateSource().
	** Function to display the disassembly window.
	*/
	void
	tuiShowDisassemAndUpdateSource (CORE_ADDR startAddr)
	{
	struct symtab_and_line sal;

	tuiShowDisassem (startAddr);
	if (currentLayout () == SRC_DISASSEM_COMMAND)
	{
	TuiLineOrAddress val;

	/*
	** Update what is in the source window if it is displayed too,
	** note that it follows what is in the disassembly window and visa-versa
	*/
	sal = find_pc_line (startAddr, 0);
	val.lineNo = sal.line;
	tuiUpdateSourceWindow (srcWin, sal.symtab, val, TRUE);
	if (sal.symtab)
	{
	set_current_source_symtab_and_line (&sal);
	tuiUpdateLocatorFilename (sal.symtab->filename);
	}
	else
	tuiUpdateLocatorFilename ("?");
	}

	return;
	} /* tuiShowDisassemAndUpdateSource */

	/*
	** tuiGetBeginAsmAddress().
	*/
	CORE_ADDR
	tuiGetBeginAsmAddress (void)
	{
	TuiGenWinInfoPtr locator;
	TuiLocatorElementPtr element;
	CORE_ADDR addr;

	locator = locatorWinInfoPtr ();
	element = &((TuiWinElementPtr) locator->content[0])->whichElement.locator;

	if (element->addr == 0)
	{
	struct minimal_symbol *main_symbol;

	/* Find address of the start of program.
	Note: this should be language specific. */
	main_symbol = lookup_minimal_symbol ("main", NULL, NULL);
	if (main_symbol == 0)
	main_symbol = lookup_minimal_symbol ("MAIN", NULL, NULL);
	if (main_symbol == 0)
	main_symbol = lookup_minimal_symbol ("_start", NULL, NULL);
	if (main_symbol)
	addr = SYMBOL_VALUE_ADDRESS (main_symbol);
	else
	addr = 0;
	}
	else /* the target is executing */
	addr = element->addr;

	return addr;
	} /* tuiGetBeginAsmAddress */

	/* Determine what the low address will be to display in the TUI's
	disassembly window. This may or may not be the same as the
	low address input. */
	CORE_ADDR
	tuiGetLowDisassemblyAddress (CORE_ADDR low, CORE_ADDR pc)
	{
	int pos;

	/* Determine where to start the disassembly so that the pc is about in the
	middle of the viewport. */
	pos = tuiDefaultWinViewportHeight (DISASSEM_WIN, DISASSEM_COMMAND) / 2;
	pc = tui_find_disassembly_address (pc, -pos);

	if (pc < low)
	pc = low;
	return pc;
	}

	/*
	** tuiVerticalDisassemScroll().
	** Scroll the disassembly forward or backward vertically
	*/
	void
	tuiVerticalDisassemScroll (TuiScrollDirection scrollDirection,
	int numToScroll)
	{
	if (disassemWin->generic.content != (OpaquePtr) NULL)
	{
	CORE_ADDR pc;
	TuiWinContent content;
	struct symtab *s;
	TuiLineOrAddress val;
	int maxLines, dir;
	struct symtab_and_line cursal = get_current_source_symtab_and_line ();

	content = (TuiWinContent) disassemWin->generic.content;
	if (cursal.symtab == (struct symtab *) NULL)
	s = find_pc_symtab (deprecated_selected_frame->pc);
	else
	s = cursal.symtab;

	/* account for hilite */
	maxLines = disassemWin->generic.height - 2;
	pc = content[0]->whichElement.source.lineOrAddr.addr;
	dir = (scrollDirection == FORWARD_SCROLL) ? maxLines : - maxLines;

	val.addr = tui_find_disassembly_address (pc, dir);
	tuiUpdateSourceWindowAsIs (disassemWin, s, val, FALSE);
	}
	}