GEMini Atari/GEMini_Atari_CD-ROM_Walnut_Creek_December_1993.iso/files/program/szadbbin/szadb.doc

Text File | 1990-02-24 | 11.4 KB | 347 lines

NAME

    szadb - Sozobon debugger

USAGE

    szadb  program

SUMMARY

Szadb is a machine language debugger with symbols which is similar
to the old UNIX 'adb' command.  Szadb is used to control and monitor
another program.  This program is loaded into memory and relocated
when szadb is first started.  Commands to szadb allow the user to
examine and modify memory and machine registers, single step and set
breakpoints.


WINDOWS

Szadb uses its own window or screen.  Thus commands and output will
not interfere with the program's window.  In fact, szadb does output
without using the BIOS so as not to confuse the program's cursor.

Use <cntl-w> to view the program's screen when you are in the szadb
window.  Type another character to get back.


ONLINE HELP

A summary of this manual is available by typing the 'help' key.  Use 'q'
to get back to the szadb prompt.  Typing any other key will advance to the
next help screen.

People in other countries are encouraged to come up with versions of szadb
with the messages in their language.  You should only have to change the one
file "lang.h".


SYNTAX

In the following description of commands, certain syntactic abbreviations
are used.

    {expr}   - any valid expression consisting of numbers, symbols and
           operators.  See the section on EXPRESSIONS
       ,{count}  - a repeat count for the command.  Can be any expression
    {format} - a string of characters which specifies how values are printed
           See the section on FORMATS
    {args}     - The arguments or parameters to be passed to the program
    {value}  - an additional expression used by the command


FORMAT OF COMMANDS

The general format for command X is

    {expr},{count}X            for most commands
or    {expr},{count}X{format}        for / or ? or =
or    {expr},{count}X{args}        for :c or :s
or    {expr},{count}X{value}        for /w or /W

Spaces and tabs can be input to improve readability.  They are always
ignored.

All fields are optional.  If {count} is missing, we do the command once.
If {format} is missing we re-use the last {format}.  If {args} are missing,
no parameters are passed.  If {values} are missing, nothing is written.

If {expr} is missing, we use the value of DOT.  DOT is set to the PC after
we single step or hit a breakpoint.  DOT is set to {expr} by most commands.
DOT is set to the next address after locations that were printed by
the / or ? command.

If the command is missing, we use the last command.  Thus an empty line
repeats the last command with DOT for the {expr} and 1 for the {count}
(and {format} the same as before).


THE ':' GROUP

    :s or :S

    This command is used to single step the program.  It will use the
    trace bit of the 68000 to force a trap after one instruction.
    We do not switch to the program window for single stepping.

    :c or :C

    This command is used to continue the program.  We will switch to
    the program window and run at full speed until a breakpoint is
    hit, a trap occurs or the program exits.

    The upper case versions of each command print all the machine
    registers after running the program.

    The first :c or :s can be followed by {args} which specify the
    parameters to be passed to the program.

    If an {expr} field is given to the :c or :s, the PC is set to
    that value.  This should be used with care!

    :b  -  set a breakpoint at {expr}
    :d  -  delete the breakpoint at {expr}

Note that the only way to re-start the program is to exit szadb and start
over.

THE '$' GROUP

    $q    - quit szadb
    $r    - print all register values
    $e    - print all external symbols and their values
    $o    - use octal numbers
    $x    - use hex numbers
    $d    - use decimal numbers
      $s    - set the maximum symbol offset to {expr}
          When address are printed by szadb, they are printed as
          symbol+offset if offset is <= to this value
    $b    - print all breakpoints
    $c    - print a stack backtrace
    $C    - print a stack backtrace with arguments
          If szadb cannot determine the number of arguments
          (because there were none or because the optimizer was used),
          it prints the location on the stack where they might be
    $p    - print the basepage of the program


THE '/' or '?' GROUP

UNIX adb uses '?' to examine a program file and '/' to look at running
process's memory.  Since szadb only looks at memory, either can be used.
We recommend using '/' since later versions of szadb may use '?' for files.

    /

    Print values from memory according to a format.  See FORMATS.
    {expr} gives the starting address to fetch values from.
    If there is more than one format character, we increment the
    address used by the size of the value printed.

    /w    - Write a 2-byte value to memory at address {expr}
    /W    - Write a 4-byte value to memory at address {expr}

THE '=' COMMAND

    =

    Print the value of {expr} according to a format.  See FORMATS.
    If there is more than one format character, we print the same
    value each time.

THE '>' GROUP

Register values can be changed using '>' followed by the register name.
This sets that register to the value of {expr}.  See REGISTER NAMES


FORMATS

Formats are similar to printf() format strings.  They specify the way
values are printed.  However, since we almost always want to print a
value and not some literal string, the '%' before each format is missing.
Also, we usually use upper case for long values instead of a leading 'l'.
Thus %d%lx%o becomes dXo.

    d  - print 2-bytes as decimal
    D  - print 4-bytes as decimal
    x  - print 2-bytes as hex
    X  - print 4-bytes as hex
    o  - print 2-bytes as octal
    O  - print 4-bytes as octal
    c  - print a single character
    b  - print 1-byte as octal
    s  - print a string

In addition, we add the following non-printf-like formats:

    i  - print a single machine language instruction
    S  - print a string with '.' for special characters
    p  - print the current value of DOT as a symbol plus offset
    a  - same as p except also print a ':' and tab
    r  - print a space
    n  - print a newline
 "string"  - print a literal string
    +  - increment DOT (nothing printed)
    -  - decrement DOT (nothing printed)
    ^  - backup DOT by the last size printed

Formats can also be preceeded by a decimal number.  This number is
usually the repeat count for the next format.  Thus instead of saying
main/iiiiXXXXXX you can say main/4i6X

The 't' format is always preceed by a number.  This format advances to
the next tab stop which a multiple of that number.


EXPRESSIONS

    Expressions are a lot like C expressions.  They include numbers
and symbols with unary and binary operators.  Expressions are always
evaluated using long (4-byte) arithmetic.  Parenthesis can be used for
grouping.  There is no precedence among binary operators - evaluation is
strictly left to right.

    NUMBERS

    Numbers can be entered in any base.  A base is specified using one
of the following prefixes:

    0x - hex
    0t - decimal
    0o - octal

    If there is no such prefix, the default base will be used.  The
default base when you start szadb is hex.  Use a leading 0 if you need
to enter a hex number which starts with a letter.

    SYMBOLS

    If your program has a symbol table, these symbol names can be
used in expressions.  The value of a symbol is the address of that
variable or function.  Although the C compiler adds a leading '_' to
all symbols, the symbol name will be found with or without the '_'.

    OTHER VALUES

    Character literals can be entered by enclosing one to four
characters in single quotes.  Multi-character literals put the first
character in the highest byte.

    The value of DOT can be used in an expression by typing "."

    Use "&" to represent the last typed {expr} field.  (DOT
changes when you print with / or ?.  "&" does not.)

    UNARY OPERATORS

    -   unary minus (2-s complement)
    ~   bitwise complement (1-s complement)
    *   fetch of 4 bytes from an address
    @   fetch of 2 bytes from an address

    BINARY OPERATORS

    +   addition
    -   subtraction
    *   multiplication
    %   division (NOT '/' !)
    &   bitwise and
    |   bitwise or


REGISTER NAMES

Szadb uses the standard Motorola register names with 'sp' for 'a7'.
Actually, there are two stack pointers which Motorola calls 'usp' for
the user stack pointer and 'ssp' for the supervisor stack pointer.
Szadb calls the other stack pointer 'xsp'.  This will be 'ssp' if
your program is running in user mode (as it usually is) or 'usp' if
it is running in supervisor mode.


SPECIAL CHARACTERS

When entering a command, use the left-arrow (backspace) to erase typed
characters.  When a lot of output is being printed, you can use cntl-S
to suspend output temporarily or cntl-C to stop the command.

Use the help key to get a summary of this document from within szadb.


MAGIC STUFF

Szadb works by changing the trap vectors to point to itself.  If you
try to debug any program which changes the trap vectors, szadb will not
work.

Breakpoints cannot be set on ROM locations, but szadb will not give you
an error if you try.

Various shells do funny things to parameters.  Szadb does not Upper-case
arguments and does not pass more than 128 bytes of parameters.

Programs compiled with the dLibs startup routine (e.g. most programs
compiled with Sozobon C) do funny things to try to determine argv[0].
In particular a pointer to the parent's basepage is followed.  Szadb
does not set up this pointer, so argv[0] is not passed under szadb.

Certain programs only work when loaded at a certain address (or only
fail when loaded at a certain address).  Running a program under szadb
changes where that program is loaded.  Thus behavior under szadb may
be different from what happens otherwise.

Programs with bugs may modify random locations of memory.  If they
happen to modify a value that is part of szadb, szadb will probably
die.  Unfortunately, this isn't UNIX.


WHERE TO GET SOZOBON C

Sozobon C is freely distributed through many bulletin boards and computer
networks worldwide.  If you cannot find it anywhere locally, you can
always order the newest release from us directly.  Send $10 US to cover
shipping, handling and floppies (add a couple $ for European orders) to

        Tony Andrews
        5902E Gunbarrel Ave.
        Boulder, Colorado USA  80301

After March 30, 1990 this will change to

        Tony Andrews
        4704 Berkshire Court
        Boulder, Colorado USA  80301

Make checks payable to Tony Andrews.  Specify single or double sided
floppies (you will get double sided if you don't say anything).

If you don't need the release, but you want to encourage further product
development from Sozobon Ltd, we will gladly accept money, ST software
such as games you don't play anymore, freeware or shareware you have
written with Sozobon and/or simple words of encouragement.


LEGALESE

/* Copyright (c) 1990 by Sozobon, Limited.  Authors: Johann Ruegg, Don Dugger
 *
 * Permission is granted to anyone to use this software for any purpose
 * on any computer system, and to redistribute it freely, with the
 * following restrictions:
 * 1) No charge may be made other than reasonable charges for reproduction.
 * 2) Modified versions must be clearly marked as such.
 * 3) The authors are not responsible for any harmful consequences
 *    of using this software, even if they result from defects in it.
 */

UNIX is a trademark of AT&T (it used to be a trademark of Bell Labs)


AUTHORS

    Johann Ruegg    uunet!dunike!onecom!wldrdg!hans
    Don Dugger    uunet!dunike!onecom!wldrdg!n0ano