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This is ./gdb.info, produced by Makeinfo version 3.12f from gdb.texinfo.
INFO-DIR-SECTION Programming & development tools.
START-INFO-DIR-ENTRY
* Gdb: (gdb). The GNU debugger.
END-INFO-DIR-ENTRY
This file documents the GNU debugger GDB.
This is the Eighth Edition, March 2000, of `Debugging with GDB: the
GNU Source-Level Debugger' for GDB Version 5.0.
Copyright (C) 1988-2000 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.
Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided also
that the entire resulting derived work is distributed under the terms
of a permission notice identical to this one.
Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions.
File: gdb.info, Node: Bootstrapping, Next: Debug Session, Prev: Stub Contents, Up: Remote Serial
What you must do for the stub
.............................
The debugging stubs that come with GDB are set up for a particular
chip architecture, but they have no information about the rest of your
debugging target machine.
First of all you need to tell the stub how to communicate with the
serial port.
`int getDebugChar()'
Write this subroutine to read a single character from the serial
port. It may be identical to `getchar' for your target system; a
different name is used to allow you to distinguish the two if you
wish.
`void putDebugChar(int)'
Write this subroutine to write a single character to the serial
port. It may be identical to `putchar' for your target system; a
different name is used to allow you to distinguish the two if you
wish.
If you want GDB to be able to stop your program while it is running,
you need to use an interrupt-driven serial driver, and arrange for it
to stop when it receives a `^C' (`\003', the control-C character).
That is the character which GDB uses to tell the remote system to stop.
Getting the debugging target to return the proper status to GDB
probably requires changes to the standard stub; one quick and dirty way
is to just execute a breakpoint instruction (the "dirty" part is that
GDB reports a `SIGTRAP' instead of a `SIGINT').
Other routines you need to supply are:
`void exceptionHandler (int EXCEPTION_NUMBER, void *EXCEPTION_ADDRESS)'
Write this function to install 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 ROM, containing entries which point to a table in RAM).
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 EXCEPTION_ADDRESS, and the processor state (stack, registers,
and so on) should be just as it is when a processor exception
occurs. So if you want to use a jump instruction to reach
EXCEPTION_ADDRESS, it should be a simple jump, not a jump to
subroutine.
For the 386, EXCEPTION_ADDRESS should be installed as an interrupt
gate so that interrupts are masked while the handler runs. The
gate should be at privilege level 0 (the most privileged level).
The SPARC and 68k stubs are able to mask interrupts themselves
without help from `exceptionHandler'.
`void flush_i_cache()'
On SPARC and SPARCLITE only, 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, GDB requires this
function to make certain that the state of your program is stable.
You must also make sure this library routine is available:
`void *memset(void *, int, int)'
This is the standard library function `memset' that sets an area of
memory to a known value. If you have one of the free versions of
`libc.a', `memset' can be found there; otherwise, you must either
obtain it from your hardware manufacturer, or write your own.
If you do not use the GNU C compiler, you may need other standard
library subroutines as well; this varies from one stub to another, but
in general the stubs are likely to use any of the common library
subroutines which `gcc' generates as inline code.
File: gdb.info, Node: Debug Session, Next: Protocol, Prev: Bootstrapping, Up: Remote Serial
Putting it all together
.......................
In summary, when your program is ready to debug, you must follow
these steps.
1. Make sure you have defined the supporting low-level routines
(*note What you must do for the stub: Bootstrapping.):
`getDebugChar', `putDebugChar',
`flush_i_cache', `memset', `exceptionHandler'.
2. Insert these lines near the top of your program:
set_debug_traps();
breakpoint();
3. For the 680x0 stub only, you need to provide a variable called
`exceptionHook'. Normally you just use:
void (*exceptionHook)() = 0;
but if before calling `set_debug_traps', you set it to point to a
function in your program, that function is called when `GDB'
continues after stopping on a trap (for example, bus error). The
function indicated by `exceptionHook' is called with one
parameter: an `int' which is the exception number.
4. Compile and link together: your program, the GDB debugging stub for
your target architecture, and the supporting subroutines.
5. Make sure you have a serial connection between your target machine
and the GDB host, and identify the serial port on the host.
6. Download your program to your target machine (or get it there by
whatever means the manufacturer provides), and start it.
7. To start remote debugging, run GDB on the host machine, and specify
as an executable file the program that is running in the remote
machine. This tells GDB how to find your program's symbols and
the contents of its pure text.
8. Establish communication using the `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 `/dev/ttyb':
target remote /dev/ttyb
To use a TCP connection, use an argument of the form `HOST:port'.
For example, to connect to port 2828 on a terminal server named
`manyfarms':
target remote manyfarms:2828
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 `detach'
command.
Whenever GDB is waiting for the remote program, if you type the
interrupt character (often <C-C>), GDB 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, GDB displays this prompt:
Interrupted while waiting for the program.
Give up (and stop debugging it)? (y or n)
If you type `y', GDB abandons the remote debugging session. (If you
decide you want to try again later, you can use `target remote' again
to connect once more.) If you type `n', GDB goes back to waiting.
File: gdb.info, Node: Protocol, Next: Server, Prev: Debug Session, Up: Remote Serial
Communication protocol
......................
The stub files provided with GDB implement the target side of the
communication protocol, and the GDB side is implemented in the GDB
source 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. `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 GDB.
In the examples below, `<-' and `->' are used to indicate
transmitted and received data respectfully.
All GDB commands and responses (other than acknowledgments) are sent
as a PACKET. A PACKET is introduced with the character `$', the actual
PACKET-DATA, and the terminating character `#' followed by a two-digit
CHECKSUM:
`$'PACKET-DATA`#'CHECKSUM
The two-digit CHECKSUM is computed as the modulo 256 sum of all
characters between the leading `$' and the trailing `#' (an eight bit
unsigned checksum).
Implementors should note that prior to GDB 5.0 the protocol
specification also included an optional two-digit SEQUENCE-ID:
`$'SEQUENCE-ID`:'PACKET-DATA`#'CHECKSUM
That SEQUENCE-ID was appended to the acknowledgment. GDB has never
output SEQUENCE-IDs. Stubs that handle packets added since GDB 5.0
must not accept SEQUENCE-ID.
When either the host or the target machine receives a packet, the
first response expected is an acknowledgment: either `+' (to indicate
the package was received correctly) or `-' (to request retransmission):
<- `$'PACKET-DATA`#'CHECKSUM
-> `+'
The host (GDB) sends COMMANDs, and the target (the debugging stub
incorporated in your program) sends a RESPONSE. In the case of step
and continue COMMANDs, the response is only sent when the operation has
completed (the target has again stopped).
PACKET-DATA consists of a sequence of characters with the exception
of `#' and `$' (see `X' packet for additional exceptions).
Fields within the packet should be separated using `,' `;' or `:'.
Except where otherwise noted all numbers are represented in HEX with
leading zeros suppressed.
Implementors should note that prior to GDB 5.0, the character `:'
could not appear as the third character in a packet (as it would
potentially conflict with the SEQUENCE-ID).
Response DATA can be run-length encoded to save space. A `*' means
that the next character is an ASCII encoding giving a repeat count
which stands for that many repetitions of the character preceding the
`*'. The encoding is `n+29', yielding a printable character where `n
>=3' (which is where rle starts to win). The printable characters `$',
`#', `+' and `-' or with a numeric value greater than 126 should not be
used.
Some remote systems have used a different run-length encoding
mechanism loosely refered to as the cisco encoding. Following the `*'
character are two hex digits that indicate the size of the packet.
So:
"`0* '"
means the same as "0000".
The error response returned for some packets includes a two character
error number. That number is not well defined.
For any COMMAND not supported by the stub, an empty response
(`$#00') should be returned. That way it is possible to extend the
protocol. A newer GDB can tell if a packet is supported based on that
response.
A stub is required to support the `g', `G', `m', `M', `c', and `s'
COMMANDs. All other COMMANDs are optional.
Below is a complete list of all currently defined COMMANDs and their
corresponding response DATA:
Packet Request Description
extended ops `!' Use the extended remote
protocol. Sticky--only
needs to be set once. The
extended remote protocol
supports the `R' packet.
reply `' Stubs that support the
extended remote protocol
return `' which,
unfortunately, is identical
to the response returned by
stubs that do not support
protocol extensions.
last signal `?' Indicate the reason the
target halted. The reply is
the same as for step and
continue.
reply see below
reserved `a' Reserved for future use
set program arguments `A'ARGLEN`,'ARGNUM`,'ARG`,...'
*(reserved)*
Initialized `argv[]' array
passed into program. ARGLEN
specifies the number of
bytes in the hex encoded
byte stream ARG. See
`gdbserver' for more details.
reply `OK'
reply `E'NN
set baud `b'BAUD Change the serial line speed
*(deprecated)* to BAUD. JTC: _When does the
transport layer state
change? When it's received,
or after the ACK is
transmitted. In either
case, there are problems if
the command or the
acknowledgment packet is
dropped._ Stan: _If people
really wanted to add
something like this, and get
it working for the first
time, they ought to modify
ser-unix.c to send some kind
of out-of-band message to a
specially-setup stub and
have the switch happen "in
between" packets, so that
from remote protocol's point
of view, nothing actually
happened._
set breakpoint `B'ADDR,MODE Set (MODE is `S') or clear
*(deprecated)* (MODE is `C') a breakpoint
at ADDR. _This has been
replaced by the `Z' and `z'
packets._
continue `c'ADDR ADDR is address to resume.
If ADDR is omitted, resume at
current address.
reply see below
continue with signal `C'SIG`;'ADDR Continue with signal SIG
(hex signal number). If
`;'ADDR is omitted, resume
at same address.
reply see below
toggle debug `d' toggle debug flag.
*(deprecated)*
detach `D' Detach GDB from the remote
system. Sent to the remote
target before GDB
disconnects.
reply _no response_ GDB does not check for any
response after sending this
packet.
reserved `e' Reserved for future use
reserved `E' Reserved for future use
reserved `f' Reserved for future use
reserved `F' Reserved for future use
read registers `g' Read general registers.
reply XX... Each byte of register data
is described by two hex
digits. The bytes with the
register are transmitted in
target byte order. The size
of each register and their
position within the `g'
PACKET are determined by the
GDB internal macros
REGISTER_RAW_SIZE and
REGISTER_NAME macros. The
specification of several
standard `g' packets is
specified below.
`E'NN for an error.
write regs `G'XX... See `g' for a description of
the XX... data.
reply `OK' for success
reply `E'NN for an error
reserved `h' Reserved for future use
set thread `H'CT... Set thread for subsequent
operations (`m', `M', `g',
`G', et.al.). C = `c' for
thread used in step and
continue; T... can be -1 for
all threads. C = `g' for
thread used in other
operations. If zero, pick a
thread, any thread.
reply `OK' for success
reply `E'NN for an error
cycle step *(draft)* `i'ADDR`,'NNN Step the remote target by a
single clock cycle. If
`,'NNN is present, cycle
step NNN cycles. If ADDR is
present, cycle step starting
at that address.
signal then cycle `I' See `i' and `S' for likely
step *(reserved)* syntax and semantics.
reserved `j' Reserved for future use
reserved `J' Reserved for future use
kill request `k' FIXME: _There is no
description of how operate
when a specific thread
context has been selected
(ie. does 'k' kill only that
thread?)_.
reserved `l' Reserved for future use
reserved `L' Reserved for future use
read memory `m'ADDR`,'LENGTH Read LENGTH bytes of memory
starting at address ADDR.
Neither GDB nor the stub
assume that sized memory
transfers are assumed using
word alligned accesses.
FIXME: _A word aligned memory
transfer mechanism is
needed._
reply XX... XX... is mem contents. Can
be fewer bytes than
requested if able to read
only part of the data.
Neither GDB nor the stub
assume that sized memory
transfers are assumed using
word alligned accesses.
FIXME: _A word aligned
memory transfer mechanism is
needed._
reply `E'NN NN is errno
write mem `M'ADDR,LENGTH`:'XX... Write LENGTH bytes of memory
starting at address ADDR.
XX... is the data.
reply `OK' for success
reply `E'NN for an error (this includes
the case where only part of
the data was written).
reserved `n' Reserved for future use
reserved `N' Reserved for future use
reserved `o' Reserved for future use
reserved `O' Reserved for future use
read reg *(reserved)* `p'N... See write register.
return R.... The hex encoded value of the
register in target byte
order.
write reg `P'N...`='R... Write register N... with
value R..., which contains
two hex digits for each byte
in the register (target byte
order).
reply `OK' for success
reply `E'NN for an error
general query `q'QUERY Request info about QUERY.
In general GDB queries have
a leading upper case letter.
Custom vendor queries
should use a company prefix
(in lower case) ex:
`qfsf.var'. QUERY may
optionally be followed by a
`,' or `;' separated list.
Stubs must ensure that they
match the full QUERY name.
reply `XX...' Hex encoded data from query.
The reply can not be empty.
reply `E'NN error reply
reply `' Indicating an unrecognized
QUERY.
general set `Q'VAR`='VAL Set value of VAR to VAL.
See `q' for a discussing of
naming conventions.
reset *(deprecated)* `r' Reset the entire system.
remote restart `R'XX Restart the remote server.
XX while needed has no clear
definition. FIXME: _An
example interaction
explaining how this packet
is used in extended-remote
mode is needed_.
step `s'ADDR ADDR is address to resume.
If ADDR is omitted, resume at
same address.
reply see below
step with signal `S'SIG`;'ADDR Like `C' but step not
continue.
reply see below
search `t'ADDR`:'PP`,'MM Search backwards starting at
address ADDR for a match
with pattern PP and mask MM.
PP and MM are 4 bytes.
ADDR must be at least 3
digits.
thread alive `T'XX Find out if the thread XX is
alive.
reply `OK' thread is still alive
reply `E'NN thread is dead
reserved `u' Reserved for future use
reserved `U' Reserved for future use
reserved `v' Reserved for future use
reserved `V' Reserved for future use
reserved `w' Reserved for future use
reserved `W' Reserved for future use
reserved `x' Reserved for future use
write mem (binary) `X'ADDR`,'LENGTH:XX... ADDR is address, LENGTH is
number of bytes, XX... is
binary data. The characters
`$', `#', and `0x7d' are
escaped using `0x7d'.
reply `OK' for success
reply `E'NN for an error
reserved `y' Reserved for future use
reserved `Y' Reserved for future use
remove break or `z'T`,'ADDR`,'LENGTH See `Z'.
watchpoint *(draft)*
insert break or `Z'T`,'ADDR`,'LENGTH T is type: `0' - software
watchpoint *(draft)* breakpoint, `1' - hardware
breakpoint, `2' - write
watchpoint, `3' - read
watchpoint, `4' - access
watchpoint; ADDR is address;
LENGTH is in bytes. For a
software breakpoint, LENGTH
specifies the size of the
instruction to be patched.
For hardware breakpoints and
watchpoints LENGTH specifies
the memory region to be
monitored. To avoid
potential problems with
duplicate packets, the
operations should be
implemented in an idempotent
way.
reply `E'NN for an error
reply `OK' for success
`' If not supported.
reserved <other> Reserved for future use
The `C', `c', `S', `s' and `?' packets can receive any of the below
as a reply. In the case of the `C', `c', `S' and `s' packets, that
reply is only returned when the target halts. In the below the exact
meaning of `signal number' is poorly defined. In general one of the
UNIX signal numbering conventions is used.
`S'AA AA is the signal number
`T'AAN...`:'R...`;'N...`:'R...`;'N...`:'R...`;'AA = two hex digit signal number; N... =
register number (hex), R... = target byte
ordered register contents, size defined by
`REGISTER_RAW_SIZE'; N... = `thread', R...
= thread process ID, this is a hex
integer; N... = other string not starting
with valid hex digit. GDB should ignore
this N..., R... pair and go on to the
next. This way we can extend the protocol.
`W'AA The process exited, and AA is the exit
status. This is only applicable for
certains sorts of targets.
`X'AA The process terminated with signal AA.
`N'AA`;'T...`;'D...`;'B... AA = signal number; T... = address of
*(obsolete)* symbol "_start"; D... = base of data
section; B... = base of bss section.
_Note: only used by Cisco Systems targets.
The difference between this reply and the
"qOffsets" query is that the 'N' packet
may arrive spontaneously whereas the
'qOffsets' is a query initiated by the host
debugger._
`O'XX... XX... is hex encoding of ASCII data. This
can happen at any time while the program
is running and the debugger should
continue to wait for 'W', 'T', etc.
The following set and query packets have already been defined.
current thread `q'`C' Return the current thread id.
reply `QC'PID Where PID is a HEX encoded 16 bit process
id.
reply * Any other reply implies the old pid.
all thread ids `q'`fThreadInfo'
`q'`sThreadInfo'Obtain a list of active thread ids from
the target (OS). Since there may be too
many active threads to fit into one reply
packet, this query works iteratively: it
may require more than one query/reply
sequence to obtain the entire list of
threads. The first query of the sequence
will be the `qf'`ThreadInfo' query;
subsequent queries in the sequence will be
the `qs'`ThreadInfo' query.
NOTE: replaces the `qL' query (see below).
reply `m'<ID> A single thread id
reply a comma-separated list of thread ids
`m'<ID>,<ID>...
reply `l' (lower case 'el') denotes end of list.
In response to each query, the target will
reply with a list of one or more thread
ids, in big-endian hex, separated by
commas. GDB will respond to each reply
with a request for more thread ids (using
the `qs' form of the query), until the
target responds with `l' (lower-case el,
for `'last'').
extra thread `q'`ThreadExtraInfo'`,'ID
info
Where <ID> is a thread-id in big-endian
hex. Obtain a printable string
description of a thread's attributes from
the target OS. This string may contain
anything that the target OS thinks is
interesting for GDB to tell the user about
the thread. The string is displayed in
GDB's `info threads' display. Some
examples of possible thread extra info
strings are "Runnable", or "Blocked on
Mutex".
reply XX... Where XX... is a hex encoding of ASCII
data, comprising the printable string
containing the extra information about the
thread's attributes.
query LIST or `q'`L'STARTFLAGTHREADCOUNTNEXTTHREAD
THREADLIST
*(deprecated)*
Obtain thread information from RTOS.
Where: STARTFLAG (one hex digit) is one to
indicate the first query and zero to
indicate a subsequent query; THREADCOUNT
(two hex digits) is the maximum number of
threads the response packet can contain;
and NEXTTHREAD (eight hex digits), for
subsequent queries (STARTFLAG is zero), is
returned in the response as ARGTHREAD.
NOTE: this query is replaced by the
`q'`fThreadInfo' query (see above).
reply
`q'`M'COUNTDONEARGTHREADTHREAD...
Where: COUNT (two hex digits) is the
number of threads being returned; DONE
(one hex digit) is zero to indicate more
threads and one indicates no further
threads; ARGTHREADID (eight hex digits) is
NEXTTHREAD from the request packet;
THREAD... is a sequence of thread IDs from
the target. THREADID (eight hex digits).
See `remote.c:parse_threadlist_response()'.
compute CRC `q'`CRC:'ADDR`,'LENGTH
of memory
block
reply `E'NN An error (such as memory fault)
reply `C'CRC32 A 32 bit cyclic redundancy check of the
specified memory region.
query sect `q'`Offsets' Get section offsets that the target used
offs when re-locating the downloaded image.
_Note: while a `Bss' offset is included in
the response, GDB ignores this and instead
applies the `Data' offset to the `Bss'
section._
reply
`Text='XXX`;Data='YYY`;Bss='ZZZ
thread info `q'`P'MODETHREADID
request
Returns information on THREADID. Where:
MODE is a hex encoded 32 bit mode;
THREADID is a hex encoded 64 bit thread ID.
reply * See
`remote.c:remote_unpack_thread_info_response()'.
remote command `q'`Rcmd,'COMMAND
COMMAND (hex encoded) is passed to the
local interpreter for execution. Invalid
commands should be reported using the
output string. Before the final result
packet, the target may also respond with a
number of intermediate `O'OUTPUT console
output packets. _Implementors should note
that providing access to a stubs's
interpreter may have security
implications_.
reply `OK' A command response with no output.
reply OUTPUT A command response with the hex encoded
output string OUTPUT.
reply `E'NN Indicate a badly formed request.
reply `' When `q'`Rcmd' is not recognized.
The following `g'/`G' packets have previously been defined. In the
below, some thirty-two bit registers are transferred as sixty-four
bits. Those registers should be zero/sign extended (which?) to fill the
space allocated. Register bytes are transfered in target byte order.
The two nibbles within a register byte are transfered most-significant -
least-significant.
MIPS32 All registers are transfered as
thirty-two bit quantities in the
order: 32 general-purpose; sr; lo;
hi; bad; cause; pc; 32
floating-point registers; fsr; fir;
fp.
MIPS64 All registers are transfered as
sixty-four bit quantities (including
thirty-two bit registers such as
`sr'). The ordering is the same as
`MIPS32'.
Example sequence of a target being re-started. Notice how the
restart does not get any direct output:
<- `R00'
-> `+'
_target restarts_
<- `?'
-> `+'
-> `T001:1234123412341234'
<- `+'
Example sequence of a target being stepped by a single instruction:
<- `G1445...'
-> `+'
<- `s'
-> `+'
_time passes_
-> `T001:1234123412341234'
<- `+'
<- `g'
-> `+'
-> `1455...'
<- `+'
File: gdb.info, Node: Server, Next: NetWare, Prev: Protocol, Up: Remote Serial
Using the `gdbserver' program
.............................
`gdbserver' is a control program for Unix-like systems, which allows
you to connect your program with a remote GDB via `target remote'--but
without linking in the usual debugging stub.
`gdbserver' is not a complete replacement for the debugging stubs,
because it requires essentially the same operating-system facilities
that GDB itself does. In fact, a system that can run `gdbserver' to
connect to a remote GDB could also run GDB locally! `gdbserver' is
sometimes useful nevertheless, because it is a much smaller program
than GDB itself. It is also easier to port than all of GDB, so you may
be able to get started more quickly on a new system by using
`gdbserver'. Finally, if you develop code for real-time systems, you
may find that the tradeoffs involved in real-time operation make it
more convenient to do as much development work as possible on another
system, for example by cross-compiling. You can use `gdbserver' to
make a similar choice for debugging.
GDB and `gdbserver' communicate via either a serial line or a TCP
connection, using the standard GDB remote serial protocol.
_On the target machine,_
you need to have a copy of the program you want to debug.
`gdbserver' does not need your program's symbol table, so you can
strip the program if necessary to save space. GDB on the host
system does all the symbol handling.
To use the server, you must tell it how to communicate with GDB;
the name of your program; and the arguments for your program. The
syntax is:
target> gdbserver COMM PROGRAM [ ARGS ... ]
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 `foo.txt' and communicate with GDB over the serial port
`/dev/com1':
target> gdbserver /dev/com1 emacs foo.txt
`gdbserver' waits passively for the host GDB to communicate with
it.
To use a TCP connection instead of a serial line:
target> gdbserver host:2345 emacs foo.txt
The only difference from the previous example is the first
argument, specifying that you are communicating with the host GDB
via TCP. The `host:2345' argument means that `gdbserver' is to
expect a TCP connection from machine `host' to local TCP port 2345.
(Currently, the `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 (for example,
`23' is reserved for `telnet').(1) You must use the same port
number with the host GDB `target remote' command.
_On the GDB host machine,_
you need an unstripped copy of your program, since GDB needs
symbols and debugging information. Start up GDB as usual, using
the name of the local copy of your program as the first argument.
(You may also need the `--baud' option if the serial line is
running at anything other than 9600bps.) After that, use `target
remote' to establish communications with `gdbserver'. Its argument
is either a device name (usually a serial device, like
`/dev/ttyb'), or a TCP port descriptor in the form `HOST:PORT'.
For example:
(gdb) target remote /dev/ttyb
communicates with the server via serial line `/dev/ttyb', and
(gdb) target remote the-target:2345
communicates via a TCP connection to port 2345 on host
`the-target'. For TCP connections, you must start up `gdbserver'
prior to using the `target remote' command. Otherwise you may get
an error whose text depends on the host system, but which usually
looks something like `Connection refused'.
---------- Footnotes ----------
(1) If you choose a port number that conflicts with another service,
`gdbserver' prints an error message and exits.
File: gdb.info, Node: NetWare, Prev: Server, Up: Remote Serial
Using the `gdbserve.nlm' program
................................
`gdbserve.nlm' is a control program for NetWare systems, which
allows you to connect your program with a remote GDB via `target
remote'.
GDB and `gdbserve.nlm' communicate via a serial line, using the
standard GDB remote serial protocol.
_On the target machine,_
you need to have a copy of the program you want to debug.
`gdbserve.nlm' does not need your program's symbol table, so you
can strip the program if necessary to save space. GDB on the host
system does all the symbol handling.
To use the server, you must tell it how to communicate with GDB;
the name of your program; and the arguments for your program. The
syntax is:
load gdbserve [ BOARD=BOARD ] [ PORT=PORT ]
[ BAUD=BAUD ] PROGRAM [ ARGS ... ]
BOARD and PORT specify the serial line; BAUD specifies the baud
rate used by the connection. PORT and NODE default to 0, BAUD
defaults to 9600bps.
For example, to debug Emacs with the argument `foo.txt'and
communicate with GDB over serial port number 2 or board 1 using a
19200bps connection:
load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
_On the GDB host machine,_
you need an unstripped copy of your program, since GDB needs
symbols and debugging information. Start up GDB as usual, using
the name of the local copy of your program as the first argument.
(You may also need the `--baud' option if the serial line is
running at anything other than 9600bps. After that, use `target
remote' to establish communications with `gdbserve.nlm'. Its
argument is a device name (usually a serial device, like
`/dev/ttyb'). For example:
(gdb) target remote /dev/ttyb
communications with the server via serial line `/dev/ttyb'.
File: gdb.info, Node: KOD, Prev: Remote, Up: Targets
Kernel Object Display
=====================
Some targets support kernel object display. Using this facility,
GDB communicates specially with the underlying operating system and can
display information about operating system-level objects such as
mutexes and other synchronization objects. Exactly which objects can be
displayed is determined on a per-OS basis.
Use the `set os' command to set the operating system. This tells
GDB which kernel object display module to initialize:
(gdb) set os cisco
If `set os' succeeds, GDB will display some information about the
operating system, and will create a new `info' command which can be
used to query the target. The `info' command is named after the
operating system:
(gdb) info cisco
List of Cisco Kernel Objects
Object Description
any Any and all objects
Further subcommands can be used to query about particular objects
known by the kernel.
There is currently no way to determine whether a given operating
system is supported other than to try it.
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