-@c -*- Texinfo -*-
-@c Copyright (c) 1990 1991 1992 1993 Free Software Foundation, Inc.
-@c This file is part of the source for the GDB manual.
-@c This text diverted to "Remote Debugging" section in general case;
-@c however, if we're doing a manual specifically for one of these, it
-@c belongs up front (in "Getting In and Out" chapter).
-
-@ifset REMOTESTUB
-@node Remote Serial
-@subsection The @value{GDBN} remote serial protocol
-
-@cindex remote serial debugging, overview
-To debug a program running on another machine (the debugging
-@dfn{target} machine), you must first arrange for all the usual
-prerequisites for the program to run by itself. For example, for a C
-program, you need
-
-@enumerate
-@item
-A startup routine to set up the C runtime environment; these usually
-have a name like @file{crt0}. The startup routine may be supplied by
-your hardware supplier, or you may have to write your own.
-
-@item
-You probably need a C subroutine library to support your program's
-subroutine calls, notably managing input and output.
-
-@item
-A way of getting your program to the other machine---for example, a
-download program. These are often supplied by the hardware
-manufacturer, but you may have to write your own from hardware
-documentation.
-@end enumerate
-
-The next step is to arrange for your program to use a serial port to
-communicate with the machine where @value{GDBN} is running (the @dfn{host}
-machine). In general terms, the scheme looks like this:
-
-@table @emph
-@item On the host,
-@value{GDBN} already understands how to use this protocol; when everything
-else is set up, you can simply use the @samp{target remote} command
-(@pxref{Targets,,Specifying a Debugging Target}).
-
-@item On the target,
-you must link with your program a few special-purpose subroutines that
-implement the @value{GDBN} remote serial protocol. The file containing these
-subroutines is called a @dfn{debugging stub}.
-@end table
-
-The debugging stub is specific to the architecture of the remote
-machine; for example, use @file{sparc-stub.c} to debug programs on
-@sc{sparc} boards.
-
-@cindex remote serial stub list
-These working remote stubs are distributed with @value{GDBN}:
-
-@table @code
-@item sparc-stub.c
-@kindex sparc-stub.c
-For @sc{sparc} architectures.
-
-@item m68k-stub.c
-@kindex m68k-stub.c
-@kindex Motorola 680x0
-@kindex 680x0
-For Motorola 680x0 architectures.
-
-@item i386-stub.c
-@kindex i386-stub.c
-@kindex Intel
-@kindex 386
-For Intel 386 and compatible architectures.
-@end table
-
-The @file{README} file in the @value{GDBN} distribution may list other
-recently added stubs.
-
-@menu
-* Stub Contents:: What the stub can do for you
-* Bootstrapping:: What you must do for the stub
-* Debug Session:: Putting it all together
-* Protocol:: Outline of the communication protocol
-@end menu
-
-@node Stub Contents
-@subsubsection What the stub can do for you
-
-@cindex remote serial stub
-The debugging stub for your architecture supplies these three
-subroutines:
-
-@table @code
-@item set_debug_traps
-@kindex set_debug_traps
-@cindex remote serial stub, initialization
-This routine arranges for @code{handle_exception} to run when your
-program stops. You must call this subroutine explicitly near the
-beginning of your program.
-
-@item handle_exception
-@kindex handle_exception
-@cindex remote serial stub, main routine
-This is the central workhorse, but your program never calls it
-explicitly---the setup code arranges for @code{handle_exception} to
-run when a trap is triggered.
-
-@code{handle_exception} takes control when your program stops during
-execution (for example, on a breakpoint), and mediates communications
-with @value{GDBN} on the host machine. This is where the communications
-protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
-representative on the target machine; it begins by sending summary
-information on the state of your program, then continues to execute,
-retrieving and transmitting any information @value{GDBN} needs, until you
-execute a @value{GDBN} command that makes your program resume; at that point,
-@code{handle_exception} returns control to your own code on the target
-machine.
-
-@item breakpoint
-@cindex @code{breakpoint} subroutine, remote
-Use this auxiliary subroutine to make your program contain a
-breakpoint. Depending on the particular situation, this may be the only
-way for @value{GDBN} to get control. For instance, if your target
-machine has some sort of interrupt button, you won't need to call this;
-pressing the interrupt button will transfer control to
-@code{handle_exception}---in effect, to @value{GDBN}. On some machines,
-simply receiving characters on the serial port may also trigger a trap;
-again, in that situation, you don't need to call @code{breakpoint} from
-your own program---simply running @samp{target remote} from the host
-@value{GDBN} session will get control.
-
-Call @code{breakpoint} if none of these is true, or if you simply want
-to make certain your program stops at a predetermined point for the
-start of your debugging session.
-@end table
-
-@node Bootstrapping
-@subsubsection What you must do for the stub
-
-@cindex remote stub, support routines
-The debugging stubs that come with @value{GDBN} are set up for a particular
-chip architecture, but they have no information about the rest of your
-debugging target machine. To allow the stub to work, you must supply
-these special low-level subroutines:
-
-@table @code
-@item int getDebugChar()
-@kindex getDebugChar
-Write this subroutine to read a single character from the serial port.
-It may be identical to @code{getchar} for your target system; a
-different name is used to allow you to distinguish the two if you wish.
-
-@item void putDebugChar(int)
-@kindex putDebugChar
-Write this subroutine to write a single character to the serial port.
-It may be identical to @code{putchar} for your target system; a
-different name is used to allow you to distinguish the two if you wish.
-
-@item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
-Write this function to install @var{exception_address} in the exception
-handling tables. You need to do this because the stub does not have any
-way of knowing what the exception handling tables on your target system
-are like (for example, the processor's table might be in @sc{rom},
-containing entries which point to a table in @sc{ram}).
-@var{exception_number} is the exception number which should be changed;
-its meaning is architecture-dependent (for example, different numbers
-might represent divide by zero, misaligned access, etc). When this
-exception occurs, control should be transferred directly to
-@var{exception_address}, and the processor state (stack, registers,
-etc.) should be just as it is when a processor exception occurs. So if
-you want to use a jump instruction to reach @var{exception_address}, it
-should be a simple jump, not a jump to subroutine.
-
-@c For the 386, doesn't the interrupt gate contain a privilege level?
-@c If so, what should it be set to? I suspect the answer is the
-@c privilege level in effect at the time that exceptionHandler is
-@c called, but I'm not sure. FIXME.
-For the 386, @var{exception_address} should be installed as an interrupt
-gate so that interrupts are masked while the handler runs. The
-@sc{sparc} and 68k stubs are able to mask interrupts themself without
-help from @code{exceptionHandler}.
-
-@item void flush_i_cache()
-@kindex flush_i_cache
-Write this subroutine to flush the instruction cache, if any, on your
-target machine. If there is no instruction cache, this subroutine may
-be a no-op.
-
-On target machines that have instruction caches, @value{GDBN} requires this
-function to make certain that the state of your program is stable.
-@end table
-
-@noindent
-You must also make sure this library routine is available:
-
-@table @code
-@item void *memset(void *, int, int)
-@kindex memset
-This is the standard library function @code{memset} that sets an area of
-memory to a known value. If you have one of the free versions of
-@code{libc.a}, @code{memset} can be found there; otherwise, you must
-either obtain it from your hardware manufacturer, or write your own.
-@end table
-
-If you do not use the GNU C compiler, you may need other standard
-library subroutines as well; this will vary from one stub to another,
-but in general the stubs are likely to use any of the common library
-subroutines which @code{gcc} generates as inline code.
-
-
-@node Debug Session
-@subsubsection Putting it all together
-
-@cindex remote serial debugging summary
-In summary, when your program is ready to debug, you must follow these
-steps.
-
-@enumerate
-@item
-Make sure you have the supporting low-level routines
-(@pxref{Bootstrapping}):
-@display
-@code{getDebugChar}, @code{putDebugChar},
-@code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
-@end display
-
-@item
-Insert these lines near the top of your program:
-
-@example
-set_debug_traps();
-breakpoint();
-@end example
-
-@item
-For the 680x0 stub only, you need to provide a variable called
-@code{exceptionHook}. Normally you just use
-
-@example
-void (*exceptionHook)() = 0;
-@end example
-
-but if before calling @code{set_debug_traps}, you set it to point to a
-function in your program, that function is called when
-@code{@value{GDBN}} continues after stopping on a trap (for example, bus
-error). The function indicated by @code{exceptionHook} is called with
-one parameter: an @code{int} which is the exception number.
-
-@item
-Compile and link together: your program, the @value{GDBN} debugging stub for
-your target architecture, and the supporting subroutines.
-
-@item
-Make sure you have a serial connection between your target machine and
-the @value{GDBN} host, and identify the serial port used for this on the host.
-
-@item
-@c The "remote" target now provides a `load' command, so we should
-@c document that. FIXME.
-Download your program to your target machine (or get it there by
-whatever means the manufacturer provides), and start it.
-
-@item
-To start remote debugging, run @value{GDBN} on the host machine, and specify
-as an executable file the program that is running in the remote machine.
-This tells @value{GDBN} how to find your program's symbols and the contents
-of its pure text.
-
-Then establish communication using the @code{target remote} command.
-Its argument is the name of the device you're using to control the
-target machine. For example:
-
-@example
-target remote /dev/ttyb
-@end example
-
-@noindent
-if the serial line is connected to the device named @file{/dev/ttyb}.
-@ignore
-@c this is from the old text, but it doesn't seem to make sense now that I've
-@c seen an example... pesch 4sep1992
-This will stop the remote machine if it is not already stopped.
-@end ignore
-@end enumerate
-
-Now you can use all the usual commands to examine and change data and to
-step and continue the remote program.
-
-To resume the remote program and stop debugging it, use the @code{detach}
-command.
-
-@cindex interrupting remote programs
-@cindex remote programs, interrupting
-Whenever @value{GDBN} is waiting for the remote program, if you type the
-interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
-program. This may or may not succeed, depending in part on the hardware
-and the serial drivers the remote system uses. If you type the
-interrupt character once again, @value{GDBN} displays this prompt:
-
-@example
-Interrupted while waiting for the program.
-Give up (and stop debugging it)? (y or n)
-@end example
-
-If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
-(If you decide you want to try again later, you can use @samp{target
-remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
-goes back to waiting.
-
-@node Protocol
-@subsubsection Outline of the communication protocol
-
-@cindex debugging stub, example
-@cindex remote stub, example
-@cindex stub example, remote debugging
-The stub files provided with @value{GDBN} implement the target side of the
-communication protocol, and the @value{GDBN} side is implemented in the
-@value{GDBN} source file @file{remote.c}. Normally, you can simply allow
-these subroutines to communicate, and ignore the details. (If you're
-implementing your own stub file, you can still ignore the details: start
-with one of the existing stub files. @file{sparc-stub.c} is the best
-organized, and therefore the easiest to read.)
-
-However, there may be occasions when you need to know something about
-the protocol---for example, if there is only one serial port to your
-target machine, you might want your program to do something special if
-it recognizes a packet meant for @value{GDBN}.
-
-@cindex protocol, @value{GDBN} remote serial
-@cindex serial protocol, @value{GDBN} remote
-@cindex remote serial protocol
-All @value{GDBN} commands and responses (other than acknowledgements, which
-are single characters) are sent as a packet which includes a
-checksum. A packet is introduced with the character @samp{$}, and ends
-with the character @samp{#} followed by a two-digit checksum:
-
-@example
-$@var{packet info}#@var{checksum}
-@end example
-
-@cindex checksum, for @value{GDBN} remote
-@noindent
-@var{checksum} is computed as the modulo 256 sum of the @var{packet
-info} characters.
-
-When either the host or the target machine receives a packet, the first
-response expected is an acknowledgement: a single character, either
-@samp{+} (to indicate the package was received correctly) or @samp{-}
-(to request retransmission).
-
-The host (@value{GDBN}) sends commands, and the target (the debugging stub
-incorporated in your program) sends data in response. The target also
-sends data when your program stops.
-
-Command packets are distinguished by their first character, which
-identifies the kind of command.
-
-These are the commands currently supported:
-
-@table @code
-@item g
-Requests the values of CPU registers.
-
-@item G
-Sets the values of CPU registers.
-
-@item m@var{addr},@var{count}
-Read @var{count} bytes at location @var{addr}.
-
-@item M@var{addr},@var{count}:@dots{}
-Write @var{count} bytes at location @var{addr}.
-
-@item c
-@itemx c@var{addr}
-Resume execution at the current address (or at @var{addr} if supplied).
-
-@item s
-@itemx s@var{addr}
-Step the target program for one instruction, from either the current
-program counter or from @var{addr} if supplied.
-
-@item k
-Kill the target program.
-
-@item ?
-Report the most recent signal. To allow you to take advantage of the
-@value{GDBN} signal handling commands, one of the functions of the debugging
-stub is to report CPU traps as the corresponding POSIX signal values.
-@end table
-
-@kindex set remotedebug
-@kindex show remotedebug
-@cindex packets, reporting on stdout
-@cindex serial connections, debugging
-If you have trouble with the serial connection, you can use the command
-@code{set remotedebug}. This makes @value{GDBN} report on all packets sent
-back and forth across the serial line to the remote machine. The
-packet-debugging information is printed on the @value{GDBN} standard output
-stream. @code{set remotedebug off} turns it off, and @code{show
-remotedebug} will show you its current state.
-@end ifset
-
-@ifset I960
-@node i960-Nindy Remote
-@subsection @value{GDBN} with a remote i960 (Nindy)
-
-@cindex Nindy
-@cindex i960
-@dfn{Nindy} is a ROM Monitor program for Intel 960 target systems. When
-@value{GDBN} is configured to control a remote Intel 960 using Nindy, you can
-tell @value{GDBN} how to connect to the 960 in several ways:
-
-@itemize @bullet
-@item
-Through command line options specifying serial port, version of the
-Nindy protocol, and communications speed;
-
-@item
-By responding to a prompt on startup;
-
-@item
-By using the @code{target} command at any point during your @value{GDBN}
-session. @xref{Target Commands, ,Commands for managing targets}.
-
-@end itemize
-
-@menu
-* Nindy Startup:: Startup with Nindy
-* Nindy Options:: Options for Nindy
-* Nindy Reset:: Nindy reset command
-@end menu
-
-@node Nindy Startup
-@subsubsection Startup with Nindy
-
-If you simply start @code{@value{GDBP}} without using any command-line
-options, you are prompted for what serial port to use, @emph{before} you
-reach the ordinary @value{GDBN} prompt:
-
-@example
-Attach /dev/ttyNN -- specify NN, or "quit" to quit:
-@end example
-
-@noindent
-Respond to the prompt with whatever suffix (after @samp{/dev/tty})
-identifies the serial port you want to use. You can, if you choose,
-simply start up with no Nindy connection by responding to the prompt
-with an empty line. If you do this and later wish to attach to Nindy,
-use @code{target} (@pxref{Target Commands, ,Commands for managing targets}).
-
-@node Nindy Options
-@subsubsection Options for Nindy
-
-These are the startup options for beginning your @value{GDBN} session with a
-Nindy-960 board attached:
-
-@table @code
-@item -r @var{port}
-Specify the serial port name of a serial interface to be used to connect
-to the target system. This option is only available when @value{GDBN} is
-configured for the Intel 960 target architecture. You may specify
-@var{port} as any of: a full pathname (e.g. @samp{-r /dev/ttya}), a
-device name in @file{/dev} (e.g. @samp{-r ttya}), or simply the unique
-suffix for a specific @code{tty} (e.g. @samp{-r a}).
-
-@item -O
-(An uppercase letter ``O'', not a zero.) Specify that @value{GDBN} should use
-the ``old'' Nindy monitor protocol to connect to the target system.
-This option is only available when @value{GDBN} is configured for the Intel 960
-target architecture.
-
-@quotation
-@emph{Warning:} if you specify @samp{-O}, but are actually trying to
-connect to a target system that expects the newer protocol, the connection
-fails, appearing to be a speed mismatch. @value{GDBN} repeatedly
-attempts to reconnect at several different line speeds. You can abort
-this process with an interrupt.
-@end quotation
-
-@item -brk
-Specify that @value{GDBN} should first send a @code{BREAK} signal to the target
-system, in an attempt to reset it, before connecting to a Nindy target.
-
-@quotation
-@emph{Warning:} Many target systems do not have the hardware that this
-requires; it only works with a few boards.
-@end quotation
-@end table
-
-The standard @samp{-b} option controls the line speed used on the serial
-port.
-
-@c @group
-@node Nindy Reset
-@subsubsection Nindy reset command
-
-@table @code
-@item reset
-@kindex reset
-For a Nindy target, this command sends a ``break'' to the remote target
-system; this is only useful if the target has been equipped with a
-circuit to perform a hard reset (or some other interesting action) when
-a break is detected.
-@end table
-@c @end group
-@end ifset
-
-@ifset AMD29K
-@node UDI29K Remote
-@subsection @value{GDBN} and the UDI protocol for AMD29K
-
-@cindex UDI
-@cindex AMD29K via UDI
-@value{GDBN} supports AMD's UDI (``Universal Debugger Interface'')
-protocol for debugging the a29k processor family. To use this
-configuration with AMD targets running the MiniMON monitor, you need the
-program @code{MONTIP}, available from AMD at no charge. You can also
-use @value{GDBN} with the UDI conformant a29k simulator program
-@code{ISSTIP}, also available from AMD.
-
-@table @code
-@item target udi @var{keyword}
-@kindex udi
-Select the UDI interface to a remote a29k board or simulator, where
-@var{keyword} is an entry in the AMD configuration file @file{udi_soc}.
-This file contains keyword entries which specify parameters used to
-connect to a29k targets. If the @file{udi_soc} file is not in your
-working directory, you must set the environment variable @samp{UDICONF}
-to its pathname.
-@end table
-
-@node EB29K Remote
-@subsection @value{GDBN} and the EBMON protocol for AMD29K
-
-@cindex EB29K board
-@cindex running 29K programs
-
-AMD distributes a 29K development board meant to fit in a PC, together
-with a DOS-hosted monitor program called @code{EBMON}. As a shorthand
-term, this development system is called the ``EB29K''. To use
-@value{GDBN} from a Unix system to run programs on the EB29K board, you
-must first connect a serial cable between the PC (which hosts the EB29K
-board) and a serial port on the Unix system. In the following, we
-assume you've hooked the cable between the PC's @file{COM1} port and
-@file{/dev/ttya} on the Unix system.
-
-@menu
-* Comms (EB29K):: Communications setup
-* gdb-EB29K:: EB29K cross-debugging
-* Remote Log:: Remote log
-@end menu
-
-@node Comms (EB29K)
-@subsubsection Communications setup
-
-The next step is to set up the PC's port, by doing something like this
-in DOS on the PC:
-
-@example
-C:\> MODE com1:9600,n,8,1,none
-@end example
-
-@noindent
-This example---run on an MS DOS 4.0 system---sets the PC port to 9600
-bps, no parity, eight data bits, one stop bit, and no ``retry'' action;
-you must match the communications parameters when establishing the Unix
-end of the connection as well.
-@c FIXME: Who knows what this "no retry action" crud from the DOS manual may
-@c mean? It's optional; leave it out? ---pesch@cygnus.com, 25feb91
-
-To give control of the PC to the Unix side of the serial line, type
-the following at the DOS console:
-
-@example
-C:\> CTTY com1
-@end example
-
-@noindent
-(Later, if you wish to return control to the DOS console, you can use
-the command @code{CTTY con}---but you must send it over the device that
-had control, in our example over the @file{COM1} serial line).
-
-From the Unix host, use a communications program such as @code{tip} or
-@code{cu} to communicate with the PC; for example,
-
-@example
-cu -s 9600 -l /dev/ttya
-@end example
-
-@noindent
-The @code{cu} options shown specify, respectively, the linespeed and the
-serial port to use. If you use @code{tip} instead, your command line
-may look something like the following:
-
-@example
-tip -9600 /dev/ttya
-@end example
-
-@noindent
-Your system may require a different name where we show
-@file{/dev/ttya} as the argument to @code{tip}. The communications
-parameters, including which port to use, are associated with the
-@code{tip} argument in the ``remote'' descriptions file---normally the
-system table @file{/etc/remote}.
-@c FIXME: What if anything needs doing to match the "n,8,1,none" part of
-@c the DOS side's comms setup? cu can support -o (odd
-@c parity), -e (even parity)---apparently no settings for no parity or
-@c for character size. Taken from stty maybe...? John points out tip
-@c can set these as internal variables, eg ~s parity=none; man stty
-@c suggests that it *might* work to stty these options with stdin or
-@c stdout redirected... ---pesch@cygnus.com, 25feb91
-
-@kindex EBMON
-Using the @code{tip} or @code{cu} connection, change the DOS working
-directory to the directory containing a copy of your 29K program, then
-start the PC program @code{EBMON} (an EB29K control program supplied
-with your board by AMD). You should see an initial display from
-@code{EBMON} similar to the one that follows, ending with the
-@code{EBMON} prompt @samp{#}---
-
-@example
-C:\> G:
-
-G:\> CD \usr\joe\work29k
-
-G:\USR\JOE\WORK29K> EBMON
-Am29000 PC Coprocessor Board Monitor, version 3.0-18
-Copyright 1990 Advanced Micro Devices, Inc.
-Written by Gibbons and Associates, Inc.
-
-Enter '?' or 'H' for help
-
-PC Coprocessor Type = EB29K
-I/O Base = 0x208
-Memory Base = 0xd0000
-
-Data Memory Size = 2048KB
-Available I-RAM Range = 0x8000 to 0x1fffff
-Available D-RAM Range = 0x80002000 to 0x801fffff
-
-PageSize = 0x400
-Register Stack Size = 0x800
-Memory Stack Size = 0x1800
-
-CPU PRL = 0x3
-Am29027 Available = No
-Byte Write Available = Yes
-
-# ~.
-@end example
-
-Then exit the @code{cu} or @code{tip} program (done in the example by
-typing @code{~.} at the @code{EBMON} prompt). @code{EBMON} will keep
-running, ready for @value{GDBN} to take over.
-
-For this example, we've assumed what is probably the most convenient
-way to make sure the same 29K program is on both the PC and the Unix
-system: a PC/NFS connection that establishes ``drive @code{G:}'' on the
-PC as a file system on the Unix host. If you do not have PC/NFS or
-something similar connecting the two systems, you must arrange some
-other way---perhaps floppy-disk transfer---of getting the 29K program
-from the Unix system to the PC; @value{GDBN} will @emph{not} download it over the
-serial line.
-
-@node gdb-EB29K
-@subsubsection EB29K cross-debugging
-
-Finally, @code{cd} to the directory containing an image of your 29K
-program on the Unix system, and start @value{GDBN}---specifying as argument the
-name of your 29K program:
-
-@example
-cd /usr/joe/work29k
-@value{GDBP} myfoo
-@end example
-
-Now you can use the @code{target} command:
-
-@example
-target amd-eb /dev/ttya 9600 MYFOO
-@c FIXME: test above 'target amd-eb' as spelled, with caps! caps are meant to
-@c emphasize that this is the name as seen by DOS (since I think DOS is
-@c single-minded about case of letters). ---pesch@cygnus.com, 25feb91
-@end example
-
-@noindent
-In this example, we've assumed your program is in a file called
-@file{myfoo}. Note that the filename given as the last argument to
-@code{target amd-eb} should be the name of the program as it appears to DOS.
-In our example this is simply @code{MYFOO}, but in general it can include
-a DOS path, and depending on your transfer mechanism may not resemble
-the name on the Unix side.
-
-At this point, you can set any breakpoints you wish; when you are ready
-to see your program run on the 29K board, use the @value{GDBN} command
-@code{run}.
-
-To stop debugging the remote program, use the @value{GDBN} @code{detach}
-command.
-
-To return control of the PC to its console, use @code{tip} or @code{cu}
-once again, after your @value{GDBN} session has concluded, to attach to
-@code{EBMON}. You can then type the command @code{q} to shut down
-@code{EBMON}, returning control to the DOS command-line interpreter.
-Type @code{CTTY con} to return command input to the main DOS console,
-and type @kbd{~.} to leave @code{tip} or @code{cu}.
-
-@node Remote Log
-@subsubsection Remote log
-@kindex eb.log
-@cindex log file for EB29K
-
-The @code{target amd-eb} command creates a file @file{eb.log} in the
-current working directory, to help debug problems with the connection.
-@file{eb.log} records all the output from @code{EBMON}, including echoes
-of the commands sent to it. Running @samp{tail -f} on this file in
-another window often helps to understand trouble with @code{EBMON}, or
-unexpected events on the PC side of the connection.
-
-@end ifset
-
-@ifset ST2000
-@node ST2000 Remote
-@subsection @value{GDBN} with a Tandem ST2000
-
-To connect your ST2000 to the host system, see the manufacturer's
-manual. Once the ST2000 is physically attached, you can run
-
-@example
-target st2000 @var{dev} @var{speed}
-@end example
-
-@noindent
-to establish it as your debugging environment.
-
-The @code{load} and @code{attach} commands are @emph{not} defined for
-this target; you must load your program into the ST2000 as you normally
-would for standalone operation. @value{GDBN} will read debugging information
-(such as symbols) from a separate, debugging version of the program
-available on your host computer.
-@c FIXME!! This is terribly vague; what little content is here is
-@c basically hearsay.
-
-@cindex ST2000 auxiliary commands
-These auxiliary @value{GDBN} commands are available to help you with the ST2000
-environment:
-
-@table @code
-@item st2000 @var{command}
-@kindex st2000 @var{cmd}
-@cindex STDBUG commands (ST2000)
-@cindex commands to STDBUG (ST2000)
-Send a @var{command} to the STDBUG monitor. See the manufacturer's
-manual for available commands.
-
-@item connect
-@cindex connect (to STDBUG)
-Connect the controlling terminal to the STDBUG command monitor. When
-you are done interacting with STDBUG, typing either of two character
-sequences will get you back to the @value{GDBN} command prompt:
-@kbd{@key{RET}~.} (Return, followed by tilde and period) or
-@kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
-@end table
-@end ifset
-
-@ifset VXWORKS
-@node VxWorks Remote
-@subsection @value{GDBN} and VxWorks
-@cindex VxWorks
-
-@value{GDBN} enables developers to spawn and debug tasks running on networked
-VxWorks targets from a Unix host. Already-running tasks spawned from
-the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
-both the UNIX host and on the VxWorks target. The program
-@code{gdb} is installed and executed on the UNIX host. (It may be
-installed with the name @code{vxgdb}, to distinguish it from a
-@value{GDBN} for debugging programs on the host itself.)
-
-The following information on connecting to VxWorks was current when
-this manual was produced; newer releases of VxWorks may use revised
-procedures.
-
-The remote debugging interface (RDB) routines are installed and executed
-on the VxWorks target. These routines are included in the VxWorks library
-@file{rdb.a} and are incorporated into the system image when source-level
-debugging is enabled in the VxWorks configuration.
-
-@kindex INCLUDE_RDB
-If you wish, you can define @code{INCLUDE_RDB} in the VxWorks
-configuration file @file{configAll.h} to include the RDB interface
-routines and spawn the source debugging task @code{tRdbTask} when
-VxWorks is booted. For more information on configuring and remaking
-VxWorks, see the manufacturer's manual.
-@c VxWorks, see the @cite{VxWorks Programmer's Guide}.
-
-Once you have included the RDB interface in your VxWorks system image
-and set your Unix execution search path to find @value{GDBN}, you are ready
-to run @value{GDBN}. From your UNIX host, run @code{gdb} (or
-@code{vxgdb}, depending on your installation).
-
-@value{GDBN} comes up showing the prompt:
-
-@example
-(vxgdb)
-@end example
-
-@menu
-* VxWorks Connection:: Connecting to VxWorks
-* VxWorks Download:: VxWorks download
-* VxWorks Attach:: Running tasks
-@end menu
-
-@node VxWorks Connection
-@subsubsection Connecting to VxWorks
-
-The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
-network. To connect to a target whose host name is ``@code{tt}'', type:
-
-@example
-(vxgdb) target vxworks tt
-@end example
-
-@value{GDBN} displays messages like these:
-
-@smallexample
-Attaching remote machine across net...
-Connected to tt.
-@end smallexample
-
-@value{GDBN} then attempts to read the symbol tables of any object modules
-loaded into the VxWorks target since it was last booted. @value{GDBN} locates
-these files by searching the directories listed in the command search
-path (@pxref{Environment, ,Your program's environment}); if it fails
-to find an object file, it displays a message such as:
-
-@example
-prog.o: No such file or directory.
-@end example
-
-When this happens, add the appropriate directory to the search path with
-the @value{GDBN} command @code{path}, and execute the @code{target}
-command again.
-
-@node VxWorks Download
-@subsubsection VxWorks download
-
-@cindex download to VxWorks
-If you have connected to the VxWorks target and you want to debug an
-object that has not yet been loaded, you can use the @value{GDBN}
-@code{load} command to download a file from UNIX to VxWorks
-incrementally. The object file given as an argument to the @code{load}
-command is actually opened twice: first by the VxWorks target in order
-to download the code, then by @value{GDBN} in order to read the symbol
-table. This can lead to problems if the current working directories on
-the two systems differ. If both systems have NFS mounted the same
-filesystems, you can avoid these problems by using absolute paths.
-Otherwise, it is simplest to set the working directory on both systems
-to the directory in which the object file resides, and then to reference
-the file by its name, without any path. For instance, a program
-@file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
-and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
-program, type this on VxWorks:
-
-@example
--> cd "@var{vxpath}/vw/demo/rdb"
-@end example
-
-Then, in @value{GDBN}, type:
-
-@example
-(vxgdb) cd @var{hostpath}/vw/demo/rdb
-(vxgdb) load prog.o
-@end example
-
-@value{GDBN} displays a response similar to this:
-
-@smallexample
-Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
-@end smallexample
-
-You can also use the @code{load} command to reload an object module
-after editing and recompiling the corresponding source file. Note that
-this will cause @value{GDBN} to delete all currently-defined breakpoints,
-auto-displays, and convenience variables, and to clear the value
-history. (This is necessary in order to preserve the integrity of
-debugger data structures that reference the target system's symbol
-table.)
-
-@node VxWorks Attach
-@subsubsection Running tasks
-
-@cindex running VxWorks tasks
-You can also attach to an existing task using the @code{attach} command as
-follows:
-
-@example
-(vxgdb) attach @var{task}
-@end example
-
-@noindent
-where @var{task} is the VxWorks hexadecimal task ID. The task can be running
-or suspended when you attach to it. If running, it will be suspended at
-the time of attachment.
-@end ifset
-
-@ifset H8
-@node Hitachi Remote
-@subsection @value{GDBN} and Hitachi Microprocessors
-@value{GDBN} needs to know these things to talk to your
-Hitachi SH, H8/300, or H8/500:
-
-@enumerate
-@item
-that you want to use @samp{target hms}, the remote debugging interface
-for Hitachi microprocessors (this is the default when GDB is configured
-specifically for the Hitachi SH, H8/300, or H8/500);
-
-@item
-what serial device connects your host to your Hitachi board (the first
-serial device available on your host is the default);
-
-@ignore
-@c this is only for Unix hosts, not currently of interest.
-@item
-what speed to use over the serial device.
-@end ignore
-@end enumerate
-
-@ifclear H8EXCLUSIVE
-@c only for Unix hosts
-@kindex device
-@cindex serial device, Hitachi micros
-Use the special @code{@value{GDBP}} command @samp{device @var{port}} if you
-need to explicitly set the serial device. The default @var{port} is the
-first available port on your host. This is only necessary on Unix
-hosts, where it is typically something like @file{/dev/ttya}.
-
-@kindex speed
-@cindex serial line speed, Hitachi micros
-@code{@value{GDBP}} has another special command to set the communications
-speed: @samp{speed @var{bps}}. This command also is only used from Unix
-hosts; on DOS hosts, set the line speed as usual from outside GDB with
-the DOS @kbd{mode} command (for instance, @w{@samp{mode
-com2:9600,n,8,1,p}} for a 9600 bps connection).
-
-The @samp{device} and @samp{speed} commands are available only when you
-use a Unix host to debug your Hitachi microprocessor programs. If you
-use a DOS host,
-@end ifclear
-@value{GDBN} depends on an auxiliary terminate-and-stay-resident program
-called @code{asynctsr} to communicate with the development board
-through a PC serial port. You must also use the DOS @code{mode} command
-to set up the serial port on the DOS side.
-
-@ifset DOSHOST
-The following sample session illustrates the steps needed to start a
-program under @value{GDBN} control on an H8/300. The example uses a
-sample H8/300 program called @file{t.x}. The procedure is the same for
-the Hitachi SH and the H8/500.
-
-First hook up your development board. In this example, we use a
-board attached to serial port @code{COM2}; if you use a different serial
-port, substitute its name in the argument of the @code{mode} command.
-When you call @code{asynctsr}, the auxiliary comms program used by the
-degugger, you give it just the numeric part of the serial port's name;
-for example, @samp{asyncstr 2} below runs @code{asyncstr} on
-@code{COM2}.
-
-@example
-(eg-C:\H8300\TEST) mode com2:9600,n,8,1,p
-
-Resident portion of MODE loaded
-
-COM2: 9600, n, 8, 1, p
-
-(eg-C:\H8300\TEST) asynctsr 2
-@end example
-
-@quotation
-@emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
-@code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
-disable it, or even boot without it, to use @code{asynctsr} to control
-your development board.
-@end quotation
-
-@kindex target hms
-Now that serial communications are set up, and the development board is
-connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
-the name of your program as the argument. @code{@value{GDBP}} prompts
-you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
-commands to begin your debugging session: @samp{target hms} to specify
-cross-debugging to the Hitachi board, and the @code{load} command to
-download your program to the board. @code{load} displays the names of
-the program's sections, and a @samp{*} for each 2K of data downloaded.
-(If you want to refresh @value{GDBN} data on symbols or on the
-executable file without downloading, use the @value{GDBN} commands
-@code{file} or @code{symbol-file}. These commands, and @code{load}
-itself, are described in @ref{Files,,Commands to specify files}.)
-
-@smallexample
-(eg-C:\H8300\TEST) @value{GDBP} t.x
-GDB is free software and you are welcome to distribute copies
- of it under certain conditions; type "show copying" to see
- the conditions.
-There is absolutely no warranty for GDB; type "show warranty"
-for details.
-GDB @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
-(gdb) target hms
-Connected to remote H8/300 HMS system.
-(gdb) load t.x
-.text : 0x8000 .. 0xabde ***********
-.data : 0xabde .. 0xad30 *
-.stack : 0xf000 .. 0xf014 *
-@end smallexample
-
-At this point, you're ready to run or debug your program. From here on,
-you can use all the usual @value{GDBN} commands. The @code{break} command
-sets breakpoints; the @code{run} command starts your program;
-@code{print} or @code{x} display data; the @code{continue} command
-resumes execution after stopping at a breakpoint. You can use the
-@code{help} command at any time to find out more about @value{GDBN} commands.
-
-Remember, however, that @emph{operating system} facilities aren't
-available on your development board; for example, if your program hangs,
-you can't send an interrupt---but you can press the @sc{reset} switch!
-
-Use the @sc{reset} button on the development board
-@itemize @bullet
-@item
-to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
-no way to pass an interrupt signal to the development board); and
-
-@item
-to return to the @value{GDBN} command prompt after your program finishes
-normally. The communications protocol provides no other way for @value{GDBN}
-to detect program completion.
-@end itemize
-
-In either case, @value{GDBN} will see the effect of a @sc{reset} on the
-development board as a ``normal exit'' of your program.
-@end ifset
-@end ifset
-
-@ifset MIPS
-@node MIPS Remote
-@subsection @value{GDBN} and remote MIPS boards
-
-@cindex MIPS boards
-@value{GDBN} can use the MIPS remote debugging protocol to talk to a
-MIPS board attached to a serial line. This is available when
-you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
-
-@kindex target mips @var{port}
-To run a program on the board, start up @code{@value{GDBP}} with the
-name of your program as the argument. To connect to the board, use the
-command @samp{target mips @var{port}}, where @var{port} is the name of
-the serial port connected to the board. If the program has not already
-been downloaded to the board, you may use the @code{load} command to
-download it. You can then use all the usual @value{GDBN} commands.
-
-@cindex @code{remotedebug}, MIPS protocol
-@c FIXME! For this to be useful, you must know something about the MIPS
-@c FIXME...protocol. Where is it described?
-You can see some debugging information about communications with the board
-by setting the @code{remotedebug} variable. If you set it to 1 using
-@samp{set remotedebug 1} every packet will be displayed. If you set it
-to 2 every character will be displayed. You can check the current value
-at any time with the command @samp{show remotedebug}.
-
-@cindex @code{timeout}, MIPS protocol
-@cindex @code{retransmit-timeout}, MIPS protocol
-The timeout used while waiting for a packet is controlled by the
-@code{timeout} variable. The default is 5 seconds. The timeout used
-while waiting for an acknowledgement of a packet is controlled by the
-@code{retransmit-timeout} variable. The default is 3 seconds.
-
-@kindex set mipsfpu off
-@cindex MIPS remote floating point
-@cindex floating point, MIPS remote
-If your target board does not support the MIPS floating point
-coprocessor, you should use the command @samp{set mipsfpu off} (you may
-wish to put this in your @value{GDBINIT} file). This will tell
-@value{GDBN} how to find the return value of functions which return
-floating point values, and tell it to call functions on the board
-without saving the floating point registers.
-@end ifset
-
-@ifset SIMS
-@node Simulator
-@subsection Simulated CPU target
-
-@ifset GENERIC
-@cindex simulator
-@cindex simulator, Z8000
-@cindex Z8000 simulator
-@cindex simulator, H8/300 or H8/500
-@cindex H8/300 or H8/500 simulator
-@cindex simulator, Hitachi SH
-@cindex Hitachi SH simulator
-@cindex CPU simulator
-For some configurations, @value{GDBN} includes a CPU simulator that you
-can use instead of a hardware CPU to debug your programs. Currently,
-a simulator is available when @value{GDBN} is configured to debug Zilog
-Z8000 or Hitachi microprocessor targets.
-@end ifset
-
-@ifclear GENERIC
-@ifset H8
-@cindex simulator, H8/300 or H8/500
-@cindex Hitachi H8/300 or H8/500 simulator
-@cindex simulator, Hitachi SH
-@cindex Hitachi SH simulator
-When configured for debugging Hitachi microprocessor targets,
-@value{GDBN} includes a CPU simulator for the target chip (a Hitachi SH,
-H8/300, or H8/500).
-@end ifset
-
-@ifset Z8K
-@cindex simulator, Z8000
-@cindex Zilog Z8000 simulator
-When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
-a Z8000 simulator.
-@end ifset
-@end ifclear
-
-@ifset Z8K
-For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
-unsegmented variant of the Z8000 architecture) or the Z8001 (the
-segmented variant). The simulator recognizes which architecture is
-appropriate by inspecting the object code.
-@end ifset
-
-@table @code
-@item target sim
-@kindex sim
-@kindex target sim
-Debug programs on a simulated CPU
-@ifset GENERIC
-(which CPU depends on the @value{GDBN} configuration)
-@end ifset
-@end table
-
-@noindent
-After specifying this target, you can debug programs for the simulated
-CPU in the same style as programs for your host computer; use the
-@code{file} command to load a new program image, the @code{run} command
-to run your program, and so on.
-
-As well as making available all the usual machine registers (see
-@code{info reg}), this debugging target provides three additional items
-of information as specially named registers:
-
-@table @code
-@item cycles
-Counts clock-ticks in the simulator.
-
-@item insts
-Counts instructions run in the simulator.
-
-@item time
-Execution time in 60ths of a second.
-@end table
-
-You can refer to these values in @value{GDBN} expressions with the usual
-conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
-conditional breakpoint that will suspend only after at least 5000
-simulated clock ticks.
-@end ifset
--- /dev/null
+@c -*- Texinfo -*-
+@c Copyright (c) 1990 1991 1992 1993 Free Software Foundation, Inc.
+@c This file is part of the source for the GDB manual.
+@c This text diverted to "Remote Debugging" section in general case;
+@c however, if we're doing a manual specifically for one of these, it
+@c belongs up front (in "Getting In and Out" chapter).
+
+@ifset REMOTESTUB
+@node Remote Serial
+@subsection The @value{GDBN} remote serial protocol
+
+@cindex remote serial debugging, overview
+To debug a program running on another machine (the debugging
+@dfn{target} machine), you must first arrange for all the usual
+prerequisites for the program to run by itself. For example, for a C
+program, you need
+
+@enumerate
+@item
+A startup routine to set up the C runtime environment; these usually
+have a name like @file{crt0}. The startup routine may be supplied by
+your hardware supplier, or you may have to write your own.
+
+@item
+You probably need a C subroutine library to support your program's
+subroutine calls, notably managing input and output.
+
+@item
+A way of getting your program to the other machine---for example, a
+download program. These are often supplied by the hardware
+manufacturer, but you may have to write your own from hardware
+documentation.
+@end enumerate
+
+The next step is to arrange for your program to use a serial port to
+communicate with the machine where @value{GDBN} is running (the @dfn{host}
+machine). In general terms, the scheme looks like this:
+
+@table @emph
+@item On the host,
+@value{GDBN} already understands how to use this protocol; when everything
+else is set up, you can simply use the @samp{target remote} command
+(@pxref{Targets,,Specifying a Debugging Target}).
+
+@item On the target,
+you must link with your program a few special-purpose subroutines that
+implement the @value{GDBN} remote serial protocol. The file containing these
+subroutines is called a @dfn{debugging stub}.
+
+@ifset GDBSERVER
+On certain remote targets, you can use an auxiliary program
+@code{gdbserver} instead of linking a stub into your program.
+@xref{Server,,Using the @code{gdbserver} program}, for details.
+@end ifset
+@end table
+
+The debugging stub is specific to the architecture of the remote
+machine; for example, use @file{sparc-stub.c} to debug programs on
+@sc{sparc} boards.
+
+@cindex remote serial stub list
+These working remote stubs are distributed with @value{GDBN}:
+
+@table @code
+@item sparc-stub.c
+@kindex sparc-stub.c
+For @sc{sparc} architectures.
+
+@item m68k-stub.c
+@kindex m68k-stub.c
+@kindex Motorola 680x0
+@kindex 680x0
+For Motorola 680x0 architectures.
+
+@item i386-stub.c
+@kindex i386-stub.c
+@kindex Intel
+@kindex 386
+For Intel 386 and compatible architectures.
+@end table
+
+The @file{README} file in the @value{GDBN} distribution may list other
+recently added stubs.
+
+@menu
+* Stub Contents:: What the stub can do for you
+* Bootstrapping:: What you must do for the stub
+* Debug Session:: Putting it all together
+* Protocol:: Outline of the communication protocol
+@ifset GDBSERVER
+* Server:: Using the `gdbserver' program
+@end ifset
+@end menu
+
+@node Stub Contents
+@subsubsection What the stub can do for you
+
+@cindex remote serial stub
+The debugging stub for your architecture supplies these three
+subroutines:
+
+@table @code
+@item set_debug_traps
+@kindex set_debug_traps
+@cindex remote serial stub, initialization
+This routine arranges for @code{handle_exception} to run when your
+program stops. You must call this subroutine explicitly near the
+beginning of your program.
+
+@item handle_exception
+@kindex handle_exception
+@cindex remote serial stub, main routine
+This is the central workhorse, but your program never calls it
+explicitly---the setup code arranges for @code{handle_exception} to
+run when a trap is triggered.
+
+@code{handle_exception} takes control when your program stops during
+execution (for example, on a breakpoint), and mediates communications
+with @value{GDBN} on the host machine. This is where the communications
+protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
+representative on the target machine; it begins by sending summary
+information on the state of your program, then continues to execute,
+retrieving and transmitting any information @value{GDBN} needs, until you
+execute a @value{GDBN} command that makes your program resume; at that point,
+@code{handle_exception} returns control to your own code on the target
+machine.
+
+@item breakpoint
+@cindex @code{breakpoint} subroutine, remote
+Use this auxiliary subroutine to make your program contain a
+breakpoint. Depending on the particular situation, this may be the only
+way for @value{GDBN} to get control. For instance, if your target
+machine has some sort of interrupt button, you won't need to call this;
+pressing the interrupt button will transfer control to
+@code{handle_exception}---in effect, to @value{GDBN}. On some machines,
+simply receiving characters on the serial port may also trigger a trap;
+again, in that situation, you don't need to call @code{breakpoint} from
+your own program---simply running @samp{target remote} from the host
+@value{GDBN} session will get control.
+
+Call @code{breakpoint} if none of these is true, or if you simply want
+to make certain your program stops at a predetermined point for the
+start of your debugging session.
+@end table
+
+@node Bootstrapping
+@subsubsection What you must do for the stub
+
+@cindex remote stub, support routines
+The debugging stubs that come with @value{GDBN} are set up for a particular
+chip architecture, but they have no information about the rest of your
+debugging target machine. To allow the stub to work, you must supply
+these special low-level subroutines:
+
+@table @code
+@item int getDebugChar()
+@kindex getDebugChar
+Write this subroutine to read a single character from the serial port.
+It may be identical to @code{getchar} for your target system; a
+different name is used to allow you to distinguish the two if you wish.
+
+@item void putDebugChar(int)
+@kindex putDebugChar
+Write this subroutine to write a single character to the serial port.
+It may be identical to @code{putchar} for your target system; a
+different name is used to allow you to distinguish the two if you wish.
+
+@item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
+Write this function to install @var{exception_address} in the exception
+handling tables. You need to do this because the stub does not have any
+way of knowing what the exception handling tables on your target system
+are like (for example, the processor's table might be in @sc{rom},
+containing entries which point to a table in @sc{ram}).
+@var{exception_number} is the exception number which should be changed;
+its meaning is architecture-dependent (for example, different numbers
+might represent divide by zero, misaligned access, etc). When this
+exception occurs, control should be transferred directly to
+@var{exception_address}, and the processor state (stack, registers,
+etc.) should be just as it is when a processor exception occurs. So if
+you want to use a jump instruction to reach @var{exception_address}, it
+should be a simple jump, not a jump to subroutine.
+
+@c For the 386, doesn't the interrupt gate contain a privilege level?
+@c If so, what should it be set to? I suspect the answer is the
+@c privilege level in effect at the time that exceptionHandler is
+@c called, but I'm not sure. FIXME.
+For the 386, @var{exception_address} should be installed as an interrupt
+gate so that interrupts are masked while the handler runs. The
+@sc{sparc} and 68k stubs are able to mask interrupts themself without
+help from @code{exceptionHandler}.
+
+@item void flush_i_cache()
+@kindex flush_i_cache
+Write this subroutine to flush the instruction cache, if any, on your
+target machine. If there is no instruction cache, this subroutine may
+be a no-op.
+
+On target machines that have instruction caches, @value{GDBN} requires this
+function to make certain that the state of your program is stable.
+@end table
+
+@noindent
+You must also make sure this library routine is available:
+
+@table @code
+@item void *memset(void *, int, int)
+@kindex memset
+This is the standard library function @code{memset} that sets an area of
+memory to a known value. If you have one of the free versions of
+@code{libc.a}, @code{memset} can be found there; otherwise, you must
+either obtain it from your hardware manufacturer, or write your own.
+@end table
+
+If you do not use the GNU C compiler, you may need other standard
+library subroutines as well; this will vary from one stub to another,
+but in general the stubs are likely to use any of the common library
+subroutines which @code{gcc} generates as inline code.
+
+
+@node Debug Session
+@subsubsection Putting it all together
+
+@cindex remote serial debugging summary
+In summary, when your program is ready to debug, you must follow these
+steps.
+
+@enumerate
+@item
+Make sure you have the supporting low-level routines
+(@pxref{Bootstrapping}):
+@display
+@code{getDebugChar}, @code{putDebugChar},
+@code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
+@end display
+
+@item
+Insert these lines near the top of your program:
+
+@example
+set_debug_traps();
+breakpoint();
+@end example
+
+@item
+For the 680x0 stub only, you need to provide a variable called
+@code{exceptionHook}. Normally you just use
+
+@example
+void (*exceptionHook)() = 0;
+@end example
+
+but if before calling @code{set_debug_traps}, you set it to point to a
+function in your program, that function is called when
+@code{@value{GDBN}} continues after stopping on a trap (for example, bus
+error). The function indicated by @code{exceptionHook} is called with
+one parameter: an @code{int} which is the exception number.
+
+@item
+Compile and link together: your program, the @value{GDBN} debugging stub for
+your target architecture, and the supporting subroutines.
+
+@item
+Make sure you have a serial connection between your target machine and
+the @value{GDBN} host, and identify the serial port used for this on the host.
+
+@item
+@c The "remote" target now provides a `load' command, so we should
+@c document that. FIXME.
+Download your program to your target machine (or get it there by
+whatever means the manufacturer provides), and start it.
+
+@item
+To start remote debugging, run @value{GDBN} on the host machine, and specify
+as an executable file the program that is running in the remote machine.
+This tells @value{GDBN} how to find your program's symbols and the contents
+of its pure text.
+
+@cindex serial line, @code{target remote}
+Then establish communication using the @code{target remote} command.
+Its argument specifies how to communicate with the target
+machine---either via a devicename attached to a direct serial line, or a
+TCP port (usually to a terminal server which in turn has a serial line
+to the target). For example, to use a serial line connected to the
+device named @file{/dev/ttyb}:
+
+@example
+target remote /dev/ttyb
+@end example
+
+@cindex TCP port, @code{target remote}
+To use a TCP connection, use an argument of the form
+@code{@var{host}:port}. For example, to connect to port 2828 on a
+terminal server named @code{manyfarms}:
+
+@example
+target remote manyfarms:2828
+@end example
+@end enumerate
+
+Now you can use all the usual commands to examine and change data and to
+step and continue the remote program.
+
+To resume the remote program and stop debugging it, use the @code{detach}
+command.
+
+@cindex interrupting remote programs
+@cindex remote programs, interrupting
+Whenever @value{GDBN} is waiting for the remote program, if you type the
+interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
+program. This may or may not succeed, depending in part on the hardware
+and the serial drivers the remote system uses. If you type the
+interrupt character once again, @value{GDBN} displays this prompt:
+
+@example
+Interrupted while waiting for the program.
+Give up (and stop debugging it)? (y or n)
+@end example
+
+If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
+(If you decide you want to try again later, you can use @samp{target
+remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
+goes back to waiting.
+
+@node Protocol
+@subsubsection Outline of the communication protocol
+
+@cindex debugging stub, example
+@cindex remote stub, example
+@cindex stub example, remote debugging
+The stub files provided with @value{GDBN} implement the target side of the
+communication protocol, and the @value{GDBN} side is implemented in the
+@value{GDBN} source file @file{remote.c}. Normally, you can simply allow
+these subroutines to communicate, and ignore the details. (If you're
+implementing your own stub file, you can still ignore the details: start
+with one of the existing stub files. @file{sparc-stub.c} is the best
+organized, and therefore the easiest to read.)
+
+However, there may be occasions when you need to know something about
+the protocol---for example, if there is only one serial port to your
+target machine, you might want your program to do something special if
+it recognizes a packet meant for @value{GDBN}.
+
+@cindex protocol, @value{GDBN} remote serial
+@cindex serial protocol, @value{GDBN} remote
+@cindex remote serial protocol
+All @value{GDBN} commands and responses (other than acknowledgements, which
+are single characters) are sent as a packet which includes a
+checksum. A packet is introduced with the character @samp{$}, and ends
+with the character @samp{#} followed by a two-digit checksum:
+
+@example
+$@var{packet info}#@var{checksum}
+@end example
+
+@cindex checksum, for @value{GDBN} remote
+@noindent
+@var{checksum} is computed as the modulo 256 sum of the @var{packet
+info} characters.
+
+When either the host or the target machine receives a packet, the first
+response expected is an acknowledgement: a single character, either
+@samp{+} (to indicate the package was received correctly) or @samp{-}
+(to request retransmission).
+
+The host (@value{GDBN}) sends commands, and the target (the debugging stub
+incorporated in your program) sends data in response. The target also
+sends data when your program stops.
+
+Command packets are distinguished by their first character, which
+identifies the kind of command.
+
+These are the commands currently supported:
+
+@table @code
+@item g
+Requests the values of CPU registers.
+
+@item G
+Sets the values of CPU registers.
+
+@item m@var{addr},@var{count}
+Read @var{count} bytes at location @var{addr}.
+
+@item M@var{addr},@var{count}:@dots{}
+Write @var{count} bytes at location @var{addr}.
+
+@item c
+@itemx c@var{addr}
+Resume execution at the current address (or at @var{addr} if supplied).
+
+@item s
+@itemx s@var{addr}
+Step the target program for one instruction, from either the current
+program counter or from @var{addr} if supplied.
+
+@item k
+Kill the target program.
+
+@item ?
+Report the most recent signal. To allow you to take advantage of the
+@value{GDBN} signal handling commands, one of the functions of the debugging
+stub is to report CPU traps as the corresponding POSIX signal values.
+@end table
+
+@kindex set remotedebug
+@kindex show remotedebug
+@cindex packets, reporting on stdout
+@cindex serial connections, debugging
+If you have trouble with the serial connection, you can use the command
+@code{set remotedebug}. This makes @value{GDBN} report on all packets sent
+back and forth across the serial line to the remote machine. The
+packet-debugging information is printed on the @value{GDBN} standard output
+stream. @code{set remotedebug off} turns it off, and @code{show
+remotedebug} will show you its current state.
+
+@ifset GDBSERVER
+@node Server
+@subsubsection Using the @code{gdbserver} program
+
+@kindex gdbserver
+@cindex remote connection without stubs
+@code{gdbserver} is a control program for Unix-like systems, which
+allows you to connect your program with a remote @value{GDBN} via
+@code{target remote}---but without linking in the usual debugging stub.
+
+@code{gdbserver} is not a complete replacement for the debugging stubs,
+because it requires essentially the same operating-system facilities
+that @value{GDBN} itself does. In fact, a system that can run
+@code{gdbserver} to connect to a remote @value{GDBN} could also run
+@var{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
+because it is a much smaller program than @value{GDBN} itself. It is
+also easier to port than all of @var{GDBN}, so you may be able to get
+started more quickly on a new system by using @code{gdbserver}.
+
+@value{GDBN} and @code{gdbserver} communicate via either a serial line
+or a TCP connection, using the standard @value{GDBN} remote serial
+protocol.
+
+@table @emph
+@item On the target,
+you need to have a copy of the program you want to debug.
+@code{gdbserver} does not need your program's symbol table, so you can
+strip the program if necessary to save space. @value{GDBN} on the host
+system does all the symbol handling.
+
+To use the server, you must tell it how to communicate with @value{GDB};
+the name of your program; and the arguments for your program. The
+syntax is:
+
+@smallexample
+target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
+@end smallexample
+
+@var{comm} is either a device name (to use a serial line) or a TCP
+hostname and portnumber. For example, to debug emacs with the argument
+@samp{foo.txt} and communicate with @value{GDBN} over the serial port
+@file{/dev/com1}:
+
+@smallexample
+target> gdbserver /dev/com1 emacs foo.txt
+@end smallexample
+
+@code{gdbserver} waits passively for the host @value{GDBN} to communicate
+with it.
+
+To use a TCP connection instead of a serial line:
+
+@smallexample
+target> gdbserver host:2345 emacs foo.txt
+@end smallexample
+
+The only difference from the previous example is the first argument,
+specifying that you are communicating with the host @value{GDBN} via
+TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
+expect a TCP connection from machine @samp{host} to local TCP port 2345.
+(Currently, the @samp{host} part is ignored.) You can choose any number
+you want for the port number as long as it does not conflict with any
+TCP ports already in use on the target system.@footnote{If you choose a
+port number that conflicts with another service, @code{gdbserver} prints
+an error message and exits.} You must use the same port number with the
+host @value{GDBN} @code{target remote} command.
+
+@item On the host,
+you need an unstripped copy of your program, since
+@value{GDBN} needs symbols and debugging information. Start up
+@value{GDBN} as usual, using the name of the local copy of your program
+as the first argument. (You may also need the
+@samp{--baud} option if the serial line is running at anything other than 9600 bps.)
+After that, use @code{target remote} to establish communications with @code{gdbserver}. Its argument is either
+a device name (usually a serial device, like @file{/dev/ttyb}), or a TCP
+port descriptof in the form @code{@var{host}:@var{PORT}}. For example:
+
+@smallexample
+(@value{GDBP}) target remote /dev/ttyb
+@end smallexample
+
+@noindent
+communicates with the server via serial line @file{/dev/ttyb}, and
+
+@smallexample
+(@value{GDBP}) target remote the-target:2345
+@end smallexample
+
+@noindent
+communicates via a TCP connection to port 2345 on host @file{the-target}.
+For TCP connections, you must start up @code{gdbserver} prior to using
+the @code{target remote} command. Otherwise you may get an error whose
+text depends on the host system, but which usually looks something like
+@samp{Connection refused}.
+@end table
+@end ifset
+
+@end ifset
+
+@ifset I960
+@node i960-Nindy Remote
+@subsection @value{GDBN} with a remote i960 (Nindy)
+
+@cindex Nindy
+@cindex i960
+@dfn{Nindy} is a ROM Monitor program for Intel 960 target systems. When
+@value{GDBN} is configured to control a remote Intel 960 using Nindy, you can
+tell @value{GDBN} how to connect to the 960 in several ways:
+
+@itemize @bullet
+@item
+Through command line options specifying serial port, version of the
+Nindy protocol, and communications speed;
+
+@item
+By responding to a prompt on startup;
+
+@item
+By using the @code{target} command at any point during your @value{GDBN}
+session. @xref{Target Commands, ,Commands for managing targets}.
+
+@end itemize
+
+@menu
+* Nindy Startup:: Startup with Nindy
+* Nindy Options:: Options for Nindy
+* Nindy Reset:: Nindy reset command
+@end menu
+
+@node Nindy Startup
+@subsubsection Startup with Nindy
+
+If you simply start @code{@value{GDBP}} without using any command-line
+options, you are prompted for what serial port to use, @emph{before} you
+reach the ordinary @value{GDBN} prompt:
+
+@example
+Attach /dev/ttyNN -- specify NN, or "quit" to quit:
+@end example
+
+@noindent
+Respond to the prompt with whatever suffix (after @samp{/dev/tty})
+identifies the serial port you want to use. You can, if you choose,
+simply start up with no Nindy connection by responding to the prompt
+with an empty line. If you do this and later wish to attach to Nindy,
+use @code{target} (@pxref{Target Commands, ,Commands for managing targets}).
+
+@node Nindy Options
+@subsubsection Options for Nindy
+
+These are the startup options for beginning your @value{GDBN} session with a
+Nindy-960 board attached:
+
+@table @code
+@item -r @var{port}
+Specify the serial port name of a serial interface to be used to connect
+to the target system. This option is only available when @value{GDBN} is
+configured for the Intel 960 target architecture. You may specify
+@var{port} as any of: a full pathname (e.g. @samp{-r /dev/ttya}), a
+device name in @file{/dev} (e.g. @samp{-r ttya}), or simply the unique
+suffix for a specific @code{tty} (e.g. @samp{-r a}).
+
+@item -O
+(An uppercase letter ``O'', not a zero.) Specify that @value{GDBN} should use
+the ``old'' Nindy monitor protocol to connect to the target system.
+This option is only available when @value{GDBN} is configured for the Intel 960
+target architecture.
+
+@quotation
+@emph{Warning:} if you specify @samp{-O}, but are actually trying to
+connect to a target system that expects the newer protocol, the connection
+fails, appearing to be a speed mismatch. @value{GDBN} repeatedly
+attempts to reconnect at several different line speeds. You can abort
+this process with an interrupt.
+@end quotation
+
+@item -brk
+Specify that @value{GDBN} should first send a @code{BREAK} signal to the target
+system, in an attempt to reset it, before connecting to a Nindy target.
+
+@quotation
+@emph{Warning:} Many target systems do not have the hardware that this
+requires; it only works with a few boards.
+@end quotation
+@end table
+
+The standard @samp{-b} option controls the line speed used on the serial
+port.
+
+@c @group
+@node Nindy Reset
+@subsubsection Nindy reset command
+
+@table @code
+@item reset
+@kindex reset
+For a Nindy target, this command sends a ``break'' to the remote target
+system; this is only useful if the target has been equipped with a
+circuit to perform a hard reset (or some other interesting action) when
+a break is detected.
+@end table
+@c @end group
+@end ifset
+
+@ifset AMD29K
+@node UDI29K Remote
+@subsection @value{GDBN} and the UDI protocol for AMD29K
+
+@cindex UDI
+@cindex AMD29K via UDI
+@value{GDBN} supports AMD's UDI (``Universal Debugger Interface'')
+protocol for debugging the a29k processor family. To use this
+configuration with AMD targets running the MiniMON monitor, you need the
+program @code{MONTIP}, available from AMD at no charge. You can also
+use @value{GDBN} with the UDI conformant a29k simulator program
+@code{ISSTIP}, also available from AMD.
+
+@table @code
+@item target udi @var{keyword}
+@kindex udi
+Select the UDI interface to a remote a29k board or simulator, where
+@var{keyword} is an entry in the AMD configuration file @file{udi_soc}.
+This file contains keyword entries which specify parameters used to
+connect to a29k targets. If the @file{udi_soc} file is not in your
+working directory, you must set the environment variable @samp{UDICONF}
+to its pathname.
+@end table
+
+@node EB29K Remote
+@subsection @value{GDBN} and the EBMON protocol for AMD29K
+
+@cindex EB29K board
+@cindex running 29K programs
+
+AMD distributes a 29K development board meant to fit in a PC, together
+with a DOS-hosted monitor program called @code{EBMON}. As a shorthand
+term, this development system is called the ``EB29K''. To use
+@value{GDBN} from a Unix system to run programs on the EB29K board, you
+must first connect a serial cable between the PC (which hosts the EB29K
+board) and a serial port on the Unix system. In the following, we
+assume you've hooked the cable between the PC's @file{COM1} port and
+@file{/dev/ttya} on the Unix system.
+
+@menu
+* Comms (EB29K):: Communications setup
+* gdb-EB29K:: EB29K cross-debugging
+* Remote Log:: Remote log
+@end menu
+
+@node Comms (EB29K)
+@subsubsection Communications setup
+
+The next step is to set up the PC's port, by doing something like this
+in DOS on the PC:
+
+@example
+C:\> MODE com1:9600,n,8,1,none
+@end example
+
+@noindent
+This example---run on an MS DOS 4.0 system---sets the PC port to 9600
+bps, no parity, eight data bits, one stop bit, and no ``retry'' action;
+you must match the communications parameters when establishing the Unix
+end of the connection as well.
+@c FIXME: Who knows what this "no retry action" crud from the DOS manual may
+@c mean? It's optional; leave it out? ---pesch@cygnus.com, 25feb91
+
+To give control of the PC to the Unix side of the serial line, type
+the following at the DOS console:
+
+@example
+C:\> CTTY com1
+@end example
+
+@noindent
+(Later, if you wish to return control to the DOS console, you can use
+the command @code{CTTY con}---but you must send it over the device that
+had control, in our example over the @file{COM1} serial line).
+
+From the Unix host, use a communications program such as @code{tip} or
+@code{cu} to communicate with the PC; for example,
+
+@example
+cu -s 9600 -l /dev/ttya
+@end example
+
+@noindent
+The @code{cu} options shown specify, respectively, the linespeed and the
+serial port to use. If you use @code{tip} instead, your command line
+may look something like the following:
+
+@example
+tip -9600 /dev/ttya
+@end example
+
+@noindent
+Your system may require a different name where we show
+@file{/dev/ttya} as the argument to @code{tip}. The communications
+parameters, including which port to use, are associated with the
+@code{tip} argument in the ``remote'' descriptions file---normally the
+system table @file{/etc/remote}.
+@c FIXME: What if anything needs doing to match the "n,8,1,none" part of
+@c the DOS side's comms setup? cu can support -o (odd
+@c parity), -e (even parity)---apparently no settings for no parity or
+@c for character size. Taken from stty maybe...? John points out tip
+@c can set these as internal variables, eg ~s parity=none; man stty
+@c suggests that it *might* work to stty these options with stdin or
+@c stdout redirected... ---pesch@cygnus.com, 25feb91
+
+@kindex EBMON
+Using the @code{tip} or @code{cu} connection, change the DOS working
+directory to the directory containing a copy of your 29K program, then
+start the PC program @code{EBMON} (an EB29K control program supplied
+with your board by AMD). You should see an initial display from
+@code{EBMON} similar to the one that follows, ending with the
+@code{EBMON} prompt @samp{#}---
+
+@example
+C:\> G:
+
+G:\> CD \usr\joe\work29k
+
+G:\USR\JOE\WORK29K> EBMON
+Am29000 PC Coprocessor Board Monitor, version 3.0-18
+Copyright 1990 Advanced Micro Devices, Inc.
+Written by Gibbons and Associates, Inc.
+
+Enter '?' or 'H' for help
+
+PC Coprocessor Type = EB29K
+I/O Base = 0x208
+Memory Base = 0xd0000
+
+Data Memory Size = 2048KB
+Available I-RAM Range = 0x8000 to 0x1fffff
+Available D-RAM Range = 0x80002000 to 0x801fffff
+
+PageSize = 0x400
+Register Stack Size = 0x800
+Memory Stack Size = 0x1800
+
+CPU PRL = 0x3
+Am29027 Available = No
+Byte Write Available = Yes
+
+# ~.
+@end example
+
+Then exit the @code{cu} or @code{tip} program (done in the example by
+typing @code{~.} at the @code{EBMON} prompt). @code{EBMON} will keep
+running, ready for @value{GDBN} to take over.
+
+For this example, we've assumed what is probably the most convenient
+way to make sure the same 29K program is on both the PC and the Unix
+system: a PC/NFS connection that establishes ``drive @code{G:}'' on the
+PC as a file system on the Unix host. If you do not have PC/NFS or
+something similar connecting the two systems, you must arrange some
+other way---perhaps floppy-disk transfer---of getting the 29K program
+from the Unix system to the PC; @value{GDBN} will @emph{not} download it over the
+serial line.
+
+@node gdb-EB29K
+@subsubsection EB29K cross-debugging
+
+Finally, @code{cd} to the directory containing an image of your 29K
+program on the Unix system, and start @value{GDBN}---specifying as argument the
+name of your 29K program:
+
+@example
+cd /usr/joe/work29k
+@value{GDBP} myfoo
+@end example
+
+Now you can use the @code{target} command:
+
+@example
+target amd-eb /dev/ttya 9600 MYFOO
+@c FIXME: test above 'target amd-eb' as spelled, with caps! caps are meant to
+@c emphasize that this is the name as seen by DOS (since I think DOS is
+@c single-minded about case of letters). ---pesch@cygnus.com, 25feb91
+@end example
+
+@noindent
+In this example, we've assumed your program is in a file called
+@file{myfoo}. Note that the filename given as the last argument to
+@code{target amd-eb} should be the name of the program as it appears to DOS.
+In our example this is simply @code{MYFOO}, but in general it can include
+a DOS path, and depending on your transfer mechanism may not resemble
+the name on the Unix side.
+
+At this point, you can set any breakpoints you wish; when you are ready
+to see your program run on the 29K board, use the @value{GDBN} command
+@code{run}.
+
+To stop debugging the remote program, use the @value{GDBN} @code{detach}
+command.
+
+To return control of the PC to its console, use @code{tip} or @code{cu}
+once again, after your @value{GDBN} session has concluded, to attach to
+@code{EBMON}. You can then type the command @code{q} to shut down
+@code{EBMON}, returning control to the DOS command-line interpreter.
+Type @code{CTTY con} to return command input to the main DOS console,
+and type @kbd{~.} to leave @code{tip} or @code{cu}.
+
+@node Remote Log
+@subsubsection Remote log
+@kindex eb.log
+@cindex log file for EB29K
+
+The @code{target amd-eb} command creates a file @file{eb.log} in the
+current working directory, to help debug problems with the connection.
+@file{eb.log} records all the output from @code{EBMON}, including echoes
+of the commands sent to it. Running @samp{tail -f} on this file in
+another window often helps to understand trouble with @code{EBMON}, or
+unexpected events on the PC side of the connection.
+
+@end ifset
+
+@ifset ST2000
+@node ST2000 Remote
+@subsection @value{GDBN} with a Tandem ST2000
+
+To connect your ST2000 to the host system, see the manufacturer's
+manual. Once the ST2000 is physically attached, you can run
+
+@example
+target st2000 @var{dev} @var{speed}
+@end example
+
+@noindent
+to establish it as your debugging environment. @var{dev} is normally
+the name of a serial device, such as @file{/dev/ttya}, connected to the
+ST2000 via a serial line. You can instead specify @var{dev} as a TCP
+connection (for example, to a serial line attached via a terminal
+concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
+
+The @code{load} and @code{attach} commands are @emph{not} defined for
+this target; you must load your program into the ST2000 as you normally
+would for standalone operation. @value{GDBN} will read debugging information
+(such as symbols) from a separate, debugging version of the program
+available on your host computer.
+@c FIXME!! This is terribly vague; what little content is here is
+@c basically hearsay.
+
+@cindex ST2000 auxiliary commands
+These auxiliary @value{GDBN} commands are available to help you with the ST2000
+environment:
+
+@table @code
+@item st2000 @var{command}
+@kindex st2000 @var{cmd}
+@cindex STDBUG commands (ST2000)
+@cindex commands to STDBUG (ST2000)
+Send a @var{command} to the STDBUG monitor. See the manufacturer's
+manual for available commands.
+
+@item connect
+@cindex connect (to STDBUG)
+Connect the controlling terminal to the STDBUG command monitor. When
+you are done interacting with STDBUG, typing either of two character
+sequences will get you back to the @value{GDBN} command prompt:
+@kbd{@key{RET}~.} (Return, followed by tilde and period) or
+@kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
+@end table
+@end ifset
+
+@ifset VXWORKS
+@node VxWorks Remote
+@subsection @value{GDBN} and VxWorks
+@cindex VxWorks
+
+@value{GDBN} enables developers to spawn and debug tasks running on networked
+VxWorks targets from a Unix host. Already-running tasks spawned from
+the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
+both the UNIX host and on the VxWorks target. The program
+@code{gdb} is installed and executed on the UNIX host. (It may be
+installed with the name @code{vxgdb}, to distinguish it from a
+@value{GDBN} for debugging programs on the host itself.)
+
+The following information on connecting to VxWorks was current when
+this manual was produced; newer releases of VxWorks may use revised
+procedures.
+
+The remote debugging interface (RDB) routines are installed and executed
+on the VxWorks target. These routines are included in the VxWorks library
+@file{rdb.a} and are incorporated into the system image when source-level
+debugging is enabled in the VxWorks configuration.
+
+@kindex INCLUDE_RDB
+If you wish, you can define @code{INCLUDE_RDB} in the VxWorks
+configuration file @file{configAll.h} to include the RDB interface
+routines and spawn the source debugging task @code{tRdbTask} when
+VxWorks is booted. For more information on configuring and remaking
+VxWorks, see the manufacturer's manual.
+@c VxWorks, see the @cite{VxWorks Programmer's Guide}.
+
+Once you have included the RDB interface in your VxWorks system image
+and set your Unix execution search path to find @value{GDBN}, you are ready
+to run @value{GDBN}. From your UNIX host, run @code{gdb} (or
+@code{vxgdb}, depending on your installation).
+
+@value{GDBN} comes up showing the prompt:
+
+@example
+(vxgdb)
+@end example
+
+@menu
+* VxWorks Connection:: Connecting to VxWorks
+* VxWorks Download:: VxWorks download
+* VxWorks Attach:: Running tasks
+@end menu
+
+@node VxWorks Connection
+@subsubsection Connecting to VxWorks
+
+The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
+network. To connect to a target whose host name is ``@code{tt}'', type:
+
+@example
+(vxgdb) target vxworks tt
+@end example
+
+@value{GDBN} displays messages like these:
+
+@smallexample
+Attaching remote machine across net...
+Connected to tt.
+@end smallexample
+
+@value{GDBN} then attempts to read the symbol tables of any object modules
+loaded into the VxWorks target since it was last booted. @value{GDBN} locates
+these files by searching the directories listed in the command search
+path (@pxref{Environment, ,Your program's environment}); if it fails
+to find an object file, it displays a message such as:
+
+@example
+prog.o: No such file or directory.
+@end example
+
+When this happens, add the appropriate directory to the search path with
+the @value{GDBN} command @code{path}, and execute the @code{target}
+command again.
+
+@node VxWorks Download
+@subsubsection VxWorks download
+
+@cindex download to VxWorks
+If you have connected to the VxWorks target and you want to debug an
+object that has not yet been loaded, you can use the @value{GDBN}
+@code{load} command to download a file from UNIX to VxWorks
+incrementally. The object file given as an argument to the @code{load}
+command is actually opened twice: first by the VxWorks target in order
+to download the code, then by @value{GDBN} in order to read the symbol
+table. This can lead to problems if the current working directories on
+the two systems differ. If both systems have NFS mounted the same
+filesystems, you can avoid these problems by using absolute paths.
+Otherwise, it is simplest to set the working directory on both systems
+to the directory in which the object file resides, and then to reference
+the file by its name, without any path. For instance, a program
+@file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
+and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
+program, type this on VxWorks:
+
+@example
+-> cd "@var{vxpath}/vw/demo/rdb"
+@end example
+
+Then, in @value{GDBN}, type:
+
+@example
+(vxgdb) cd @var{hostpath}/vw/demo/rdb
+(vxgdb) load prog.o
+@end example
+
+@value{GDBN} displays a response similar to this:
+
+@smallexample
+Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
+@end smallexample
+
+You can also use the @code{load} command to reload an object module
+after editing and recompiling the corresponding source file. Note that
+this will cause @value{GDBN} to delete all currently-defined breakpoints,
+auto-displays, and convenience variables, and to clear the value
+history. (This is necessary in order to preserve the integrity of
+debugger data structures that reference the target system's symbol
+table.)
+
+@node VxWorks Attach
+@subsubsection Running tasks
+
+@cindex running VxWorks tasks
+You can also attach to an existing task using the @code{attach} command as
+follows:
+
+@example
+(vxgdb) attach @var{task}
+@end example
+
+@noindent
+where @var{task} is the VxWorks hexadecimal task ID. The task can be running
+or suspended when you attach to it. If running, it will be suspended at
+the time of attachment.
+@end ifset
+
+@ifset H8
+@node Hitachi Remote
+@subsection @value{GDBN} and Hitachi Microprocessors
+@value{GDBN} needs to know these things to talk to your
+Hitachi SH, H8/300, or H8/500:
+
+@enumerate
+@item
+that you want to use @samp{target hms}, the remote debugging interface
+for Hitachi microprocessors (this is the default when GDB is configured
+specifically for the Hitachi SH, H8/300, or H8/500);
+
+@item
+what serial device connects your host to your Hitachi board (the first
+serial device available on your host is the default);
+
+@ignore
+@c this is only for Unix hosts, not currently of interest.
+@item
+what speed to use over the serial device.
+@end ignore
+@end enumerate
+
+@ifclear H8EXCLUSIVE
+@c only for Unix hosts
+@kindex device
+@cindex serial device, Hitachi micros
+Use the special @code{@value{GDBP}} command @samp{device @var{port}} if you
+need to explicitly set the serial device. The default @var{port} is the
+first available port on your host. This is only necessary on Unix
+hosts, where it is typically something like @file{/dev/ttya}.
+
+@kindex speed
+@cindex serial line speed, Hitachi micros
+@code{@value{GDBP}} has another special command to set the communications
+speed: @samp{speed @var{bps}}. This command also is only used from Unix
+hosts; on DOS hosts, set the line speed as usual from outside GDB with
+the DOS @kbd{mode} command (for instance, @w{@samp{mode
+com2:9600,n,8,1,p}} for a 9600 bps connection).
+
+The @samp{device} and @samp{speed} commands are available only when you
+use a Unix host to debug your Hitachi microprocessor programs. If you
+use a DOS host,
+@end ifclear
+@value{GDBN} depends on an auxiliary terminate-and-stay-resident program
+called @code{asynctsr} to communicate with the development board
+through a PC serial port. You must also use the DOS @code{mode} command
+to set up the serial port on the DOS side.
+
+@ifset DOSHOST
+The following sample session illustrates the steps needed to start a
+program under @value{GDBN} control on an H8/300. The example uses a
+sample H8/300 program called @file{t.x}. The procedure is the same for
+the Hitachi SH and the H8/500.
+
+First hook up your development board. In this example, we use a
+board attached to serial port @code{COM2}; if you use a different serial
+port, substitute its name in the argument of the @code{mode} command.
+When you call @code{asynctsr}, the auxiliary comms program used by the
+degugger, you give it just the numeric part of the serial port's name;
+for example, @samp{asyncstr 2} below runs @code{asyncstr} on
+@code{COM2}.
+
+@example
+(eg-C:\H8300\TEST) mode com2:9600,n,8,1,p
+
+Resident portion of MODE loaded
+
+COM2: 9600, n, 8, 1, p
+
+(eg-C:\H8300\TEST) asynctsr 2
+@end example
+
+@quotation
+@emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
+@code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
+disable it, or even boot without it, to use @code{asynctsr} to control
+your development board.
+@end quotation
+
+@kindex target hms
+Now that serial communications are set up, and the development board is
+connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
+the name of your program as the argument. @code{@value{GDBP}} prompts
+you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
+commands to begin your debugging session: @samp{target hms} to specify
+cross-debugging to the Hitachi board, and the @code{load} command to
+download your program to the board. @code{load} displays the names of
+the program's sections, and a @samp{*} for each 2K of data downloaded.
+(If you want to refresh @value{GDBN} data on symbols or on the
+executable file without downloading, use the @value{GDBN} commands
+@code{file} or @code{symbol-file}. These commands, and @code{load}
+itself, are described in @ref{Files,,Commands to specify files}.)
+
+@smallexample
+(eg-C:\H8300\TEST) @value{GDBP} t.x
+GDB is free software and you are welcome to distribute copies
+ of it under certain conditions; type "show copying" to see
+ the conditions.
+There is absolutely no warranty for GDB; type "show warranty"
+for details.
+GDB @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
+(gdb) target hms
+Connected to remote H8/300 HMS system.
+(gdb) load t.x
+.text : 0x8000 .. 0xabde ***********
+.data : 0xabde .. 0xad30 *
+.stack : 0xf000 .. 0xf014 *
+@end smallexample
+
+At this point, you're ready to run or debug your program. From here on,
+you can use all the usual @value{GDBN} commands. The @code{break} command
+sets breakpoints; the @code{run} command starts your program;
+@code{print} or @code{x} display data; the @code{continue} command
+resumes execution after stopping at a breakpoint. You can use the
+@code{help} command at any time to find out more about @value{GDBN} commands.
+
+Remember, however, that @emph{operating system} facilities aren't
+available on your development board; for example, if your program hangs,
+you can't send an interrupt---but you can press the @sc{reset} switch!
+
+Use the @sc{reset} button on the development board
+@itemize @bullet
+@item
+to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
+no way to pass an interrupt signal to the development board); and
+
+@item
+to return to the @value{GDBN} command prompt after your program finishes
+normally. The communications protocol provides no other way for @value{GDBN}
+to detect program completion.
+@end itemize
+
+In either case, @value{GDBN} will see the effect of a @sc{reset} on the
+development board as a ``normal exit'' of your program.
+@end ifset
+@end ifset
+
+@ifset MIPS
+@node MIPS Remote
+@subsection @value{GDBN} and remote MIPS boards
+
+@cindex MIPS boards
+@value{GDBN} can use the MIPS remote debugging protocol to talk to a
+MIPS board attached to a serial line. This is available when
+you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
+
+@kindex target mips @var{port}
+To run a program on the board, start up @code{@value{GDBP}} with the
+name of your program as the argument. To connect to the board, use the
+command @samp{target mips @var{port}}, where @var{port} is the name of
+the serial port connected to the board. If the program has not already
+been downloaded to the board, you may use the @code{load} command to
+download it. You can then use all the usual @value{GDBN} commands.
+
+You can also specify @var{port} as a TCP connection (for instance, to a
+serial line managed by a terminal concentrator), using the syntax
+@code{@var{hostname}:@var{portnumber}}.
+
+@cindex @code{remotedebug}, MIPS protocol
+@c FIXME! For this to be useful, you must know something about the MIPS
+@c FIXME...protocol. Where is it described?
+You can see some debugging information about communications with the board
+by setting the @code{remotedebug} variable. If you set it to 1 using
+@samp{set remotedebug 1} every packet will be displayed. If you set it
+to 2 every character will be displayed. You can check the current value
+at any time with the command @samp{show remotedebug}.
+
+@cindex @code{timeout}, MIPS protocol
+@cindex @code{retransmit-timeout}, MIPS protocol
+The timeout used while waiting for a packet is controlled by the
+@code{timeout} variable. The default is 5 seconds. The timeout used
+while waiting for an acknowledgement of a packet is controlled by the
+@code{retransmit-timeout} variable. The default is 3 seconds.
+
+@kindex set mipsfpu off
+@cindex MIPS remote floating point
+@cindex floating point, MIPS remote
+If your target board does not support the MIPS floating point
+coprocessor, you should use the command @samp{set mipsfpu off} (you may
+wish to put this in your @value{GDBINIT} file). This will tell
+@value{GDBN} how to find the return value of functions which return
+floating point values, and tell it to call functions on the board
+without saving the floating point registers.
+@end ifset
+
+@ifset SIMS
+@node Simulator
+@subsection Simulated CPU target
+
+@ifset GENERIC
+@cindex simulator
+@cindex simulator, Z8000
+@cindex Z8000 simulator
+@cindex simulator, H8/300 or H8/500
+@cindex H8/300 or H8/500 simulator
+@cindex simulator, Hitachi SH
+@cindex Hitachi SH simulator
+@cindex CPU simulator
+For some configurations, @value{GDBN} includes a CPU simulator that you
+can use instead of a hardware CPU to debug your programs. Currently,
+a simulator is available when @value{GDBN} is configured to debug Zilog
+Z8000 or Hitachi microprocessor targets.
+@end ifset
+
+@ifclear GENERIC
+@ifset H8
+@cindex simulator, H8/300 or H8/500
+@cindex Hitachi H8/300 or H8/500 simulator
+@cindex simulator, Hitachi SH
+@cindex Hitachi SH simulator
+When configured for debugging Hitachi microprocessor targets,
+@value{GDBN} includes a CPU simulator for the target chip (a Hitachi SH,
+H8/300, or H8/500).
+@end ifset
+
+@ifset Z8K
+@cindex simulator, Z8000
+@cindex Zilog Z8000 simulator
+When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
+a Z8000 simulator.
+@end ifset
+@end ifclear
+
+@ifset Z8K
+For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
+unsegmented variant of the Z8000 architecture) or the Z8001 (the
+segmented variant). The simulator recognizes which architecture is
+appropriate by inspecting the object code.
+@end ifset
+
+@table @code
+@item target sim
+@kindex sim
+@kindex target sim
+Debug programs on a simulated CPU
+@ifset GENERIC
+(which CPU depends on the @value{GDBN} configuration)
+@end ifset
+@end table
+
+@noindent
+After specifying this target, you can debug programs for the simulated
+CPU in the same style as programs for your host computer; use the
+@code{file} command to load a new program image, the @code{run} command
+to run your program, and so on.
+
+As well as making available all the usual machine registers (see
+@code{info reg}), this debugging target provides three additional items
+of information as specially named registers:
+
+@table @code
+@item cycles
+Counts clock-ticks in the simulator.
+
+@item insts
+Counts instructions run in the simulator.
+
+@item time
+Execution time in 60ths of a second.
+@end table
+
+You can refer to these values in @value{GDBN} expressions with the usual
+conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
+conditional breakpoint that will suspend only after at least 5000
+simulated clock ticks.
+@end ifset
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