While nearly all GDB commands are available for all native and cross versions of the debugger, there are some exceptions. This chapter describes things that are only available in certain configurations.
There are three major categories of configurations: native configurations, where the host and target are the same, embedded operating system configurations, which are usually the same for several different processor architectures, and bare embedded processors, which are quite different from each other.
This section describes details specific to particular native configurations.
On HP-UX systems, if you refer to a function or variable name that begins with a dollar sign, GDB searches for a user or system name first, before it searches for a convenience variable.
Many versions of SVR4 provide a facility called `/proc' that can be
used to examine the image of a running process using file-system
subroutines. If GDB is configured for an operating system with
this facility, the command info proc is available to report on
several kinds of information about the process running your program.
info proc works only on SVR4 systems that include the
procfs code. This includes OSF/1 (Digital Unix), Solaris, Irix,
and Unixware, but not HP-UX or Linux, for example.
info proc
info proc mappings
info proc times
info proc id
info proc status
info proc all
DJGPP is the port of GNU development tools to MS-DOS and MS-Windows. DJGPP programs are 32-bit protected-mode programs that use the DPMI (DOS Protected-Mode Interface) API to run on top of real-mode DOS systems and their emulations.
GDB supports native debugging of DJGPP programs, and defines a few commands specific to the DJGPP port. This subsection describes those commands.
info dos
info dos sysinfo
info dos gdt
info dos ldt
info dos idt
This comes in handy when you want to see whether a pointer is outside the data segment's limit (i.e. garbled).(gdb) info dos ldt $ds0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)
info dos pde
info dos pte
info dos address-pte addr
i is stored:
This says that(gdb) info dos address-pte __djgpp_base_address + (char *)&iPage Table entry for address 0x11a00d30:Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30
i is stored at offset 0xd30 from the page
whose physical base address is 0x02698000, and prints all the
attributes of that page.
Note that you must cast the addresses of variables to a char *,
since otherwise the value of __djgpp_base_address, the base
address of all variables and functions in a DJGPP program, will
be added using the rules of C pointer arithmetics: if i is
declared an int, GDB will add 4 times the value of
__djgpp_base_address to the address of i.
Here's another example, it displays the Page Table entry for the
transfer buffer:
(The(gdb) info dos address-pte *((unsigned *)&_go32_info_block + 3)Page Table entry for address 0x29110:Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110
+ 3 offset is because the transfer buffer's address is the
3rd member of the _go32_info_block structure.) The output of
this command clearly shows that addresses in conventional memory are
mapped 1:1, i.e. the physical and linear addresses are identical.
This command is supported only with some DPMI servers.
This section describes configurations involving the debugging of embedded operating systems that are available for several different architectures.
GDB includes the ability to debug programs running on various real-time operating systems.
target vxworks machinename
On VxWorks, load links filename dynamically on the
current target system as well as adding its symbols in GDB.
GDB 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. GDB uses code that runs on
both the Unix host and on the VxWorks target. The program
gdb is installed and executed on the Unix host. (It may be
installed with the name vxgdb, to distinguish it from a
GDB for debugging programs on the host itself.)
VxWorks-timeout args
vxworks-timeout.
This option is set by the user, and args represents the number of
seconds GDB waits for responses to rpc's. You might use this if
your VxWorks target is a slow software simulator or is on the far side
of a thin network line.
The following information on connecting to VxWorks was current when this manual was produced; newer releases of VxWorks may use revised procedures.
To use GDB with VxWorks, you must rebuild your VxWorks kernel
to include the remote debugging interface routines in the VxWorks
library `rdb.a'. To do this, define INCLUDE_RDB in the
VxWorks configuration file `configAll.h' and rebuild your VxWorks
kernel. The resulting kernel contains `rdb.a', and spawns the
source debugging task tRdbTask when VxWorks is booted. For more
information on configuring and remaking VxWorks, see the manufacturer's
manual.
Once you have included `rdb.a' in your VxWorks system image and set
your Unix execution search path to find GDB, you are ready to
run GDB. From your Unix host, run gdb (or
vxgdb, depending on your installation).
GDB comes up showing the prompt:
(vxgdb)
The GDB command target lets you connect to a VxWorks target on the
network. To connect to a target whose host name is "tt", type:
(vxgdb) target vxworks tt
GDB displays messages like these:
Attaching remote machine across net... Connected to tt.
GDB then attempts to read the symbol tables of any object modules loaded into the VxWorks target since it was last booted. GDB locates these files by searching the directories listed in the command search path (see section Your program's environment); if it fails to find an object file, it displays a message such as:
prog.o: No such file or directory.
When this happens, add the appropriate directory to the search path with
the GDB command path, and execute the target
command again.
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 GDB
load command to download a file from Unix to VxWorks
incrementally. The object file given as an argument to the load
command is actually opened twice: first by the VxWorks target in order
to download the code, then by GDB 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
`prog.o' may reside in `vxpath/vw/demo/rdb' in VxWorks
and in `hostpath/vw/demo/rdb' on the host. To load this
program, type this on VxWorks:
-> cd "vxpath/vw/demo/rdb"
Then, in GDB, type:
(vxgdb) cd hostpath/vw/demo/rdb (vxgdb) load prog.o
GDB displays a response similar to this:
Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
You can also use the load command to reload an object module
after editing and recompiling the corresponding source file. Note that
this makes GDB 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's data structures that reference the target system's symbol
table.)
You can also attach to an existing task using the attach command as
follows:
(vxgdb) attach task
where task is the VxWorks hexadecimal task ID. The task can be running or suspended when you attach to it. Running tasks are suspended at the time of attachment.
This section goes into details specific to particular embedded configurations.
target adapt dev
target amd-eb dev speed PROG
target remote;
speed allows you to specify the linespeed; and PROG is the
name of the program to be debugged, as it appears to DOS on the PC.
See section EBMON protocol for AMD29K.
GDB 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 MONTIP, available from AMD at no charge. You can also
use GDB with the UDI-conformant a29k simulator program
ISSTIP, also available from AMD.
target udi keyword
AMD distributes a 29K development board meant to fit in a PC, together
with a DOS-hosted monitor program called EBMON. As a shorthand
term, this development system is called the "EB29K". To use
GDB 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 `COM1' port and
`/dev/ttya' on the Unix system.
The next step is to set up the PC's port, by doing something like this in DOS on the PC:
C:\> MODE com1:9600,n,8,1,none
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.
To give control of the PC to the Unix side of the serial line, type the following at the DOS console:
C:\> CTTY com1
(Later, if you wish to return control to the DOS console, you can use
the command CTTY con---but you must send it over the device that
had control, in our example over the `COM1' serial line.)
From the Unix host, use a communications program such as tip or
cu to communicate with the PC; for example,
cu -s 9600 -l /dev/ttya
The cu options shown specify, respectively, the linespeed and the
serial port to use. If you use tip instead, your command line
may look something like the following:
tip -9600 /dev/ttya
Your system may require a different name where we show
`/dev/ttya' as the argument to tip. The communications
parameters, including which port to use, are associated with the
tip argument in the "remote" descriptions file--normally the
system table `/etc/remote'.
Using the tip or cu connection, change the DOS working
directory to the directory containing a copy of your 29K program, then
start the PC program EBMON (an EB29K control program supplied
with your board by AMD). You should see an initial display from
EBMON similar to the one that follows, ending with the
EBMON prompt `#'---
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 # ~.
Then exit the cu or tip program (done in the example by
typing ~. at the EBMON prompt). EBMON keeps
running, ready for GDB 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 `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; GDB does not download it over the serial line.
Finally, cd to the directory containing an image of your 29K
program on the Unix system, and start GDB---specifying as argument the
name of your 29K program:
cd /usr/joe/work29k gdb myfoo
Now you can use the target command:
target amd-eb /dev/ttya 9600 MYFOO
In this example, we've assumed your program is in a file called
`myfoo'. Note that the filename given as the last argument to
target amd-eb should be the name of the program as it appears to DOS.
In our example this is simply 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 GDB command
run.
To stop debugging the remote program, use the GDB detach
command.
To return control of the PC to its console, use tip or cu
once again, after your GDB session has concluded, to attach to
EBMON. You can then type the command q to shut down
EBMON, returning control to the DOS command-line interpreter.
Type CTTY con to return command input to the main DOS console,
and type ~. to leave tip or cu.
The target amd-eb command creates a file `eb.log' in the
current working directory, to help debug problems with the connection.
`eb.log' records all the output from EBMON, including echoes
of the commands sent to it. Running `tail -f' on this file in
another window often helps to understand trouble with EBMON, or
unexpected events on the PC side of the connection.
target rdi dev
target rdp dev
target hms dev
device and speed to control the serial
line and the communications speed used.
target e7000 dev
target sh3 dev
target sh3e dev
When you select remote debugging to a Hitachi SH, H8/300, or H8/500
board, the load command downloads your program to the Hitachi
board and also opens it as the current executable target for
GDB on your host (like the file command).
GDB needs to know these things to talk to your Hitachi SH, H8/300, or H8/500:
Use the special GDB command `device port' if you
need to explicitly set the serial device. The default port is the
first available port on your host. This is only necessary on Unix
hosts, where it is typically something like `/dev/ttya'.
GDB has another special command to set the communications
speed: `speed 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 mode command (for instance,
mode com2:9600,n,8,1,p for a 9600bps connection).
The `device' and `speed' commands are available only when you
use a Unix host to debug your Hitachi microprocessor programs. If you
use a DOS host,
GDB depends on an auxiliary terminate-and-stay-resident program
called asynctsr to communicate with the development board
through a PC serial port. You must also use the DOS mode command
to set up the serial port on the DOS side.
The following sample session illustrates the steps needed to start a program under GDB control on an H8/300. The example uses a sample H8/300 program called `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 COM2; if you use a different serial
port, substitute its name in the argument of the mode command.
When you call asynctsr, the auxiliary comms program used by the
debugger, you give it just the numeric part of the serial port's name;
for example, `asyncstr 2' below runs asyncstr on
COM2.
C:\H8300\TEST> asynctsr 2 C:\H8300\TEST> mode com2:9600,n,8,1,p Resident portion of MODE loaded COM2: 9600, n, 8, 1, p
Warning: We have noticed a bug in PC-NFS that conflicts with
asynctsr. If you also run PC-NFS on your DOS host, you may need to disable it, or even boot without it, to useasynctsrto control your development board.
Now that serial communications are set up, and the development board is
connected, you can start up GDB. Call gdb with
the name of your program as the argument. GDB prompts
you, as usual, with the prompt `(gdb)'. Use two special
commands to begin your debugging session: `target hms' to specify
cross-debugging to the Hitachi board, and the load command to
download your program to the board. load displays the names of
the program's sections, and a `*' for each 2K of data downloaded.
(If you want to refresh GDB data on symbols or on the
executable file without downloading, use the GDB commands
file or symbol-file. These commands, and load
itself, are described in section Commands to specify files.)
(eg-C:\H8300\TEST) gdb 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 5.1.1, 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 *
At this point, you're ready to run or debug your program. From here on,
you can use all the usual GDB commands. The break command
sets breakpoints; the run command starts your program;
print or x display data; the continue command
resumes execution after stopping at a breakpoint. You can use the
help command at any time to find out more about GDB commands.
Remember, however, that 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 RESET switch!
Use the RESET button on the development board
In either case, GDB sees the effect of a RESET on the development board as a "normal exit" of your program.
You can use the E7000 in-circuit emulator to develop code for either the Hitachi SH or the H8/300H. Use one of these forms of the `target e7000' command to connect GDB to your E7000:
target e7000 port speed
target e7000 hostname
telnet to connect.
Some GDB commands are available only for the H8/300:
set machine h8300
set machine h8300h
set memory mod
show memory
small,
big, medium, and compact.
target mon960 dev
target nindy devicename
Nindy is a ROM Monitor program for Intel 960 target systems. When GDB is configured to control a remote Intel 960 using Nindy, you can tell GDB how to connect to the 960 in several ways:
target command at any point during your GDB
session. See section Commands for managing targets.
With the Nindy interface to an Intel 960 board, load
downloads filename to the 960 as well as adding its symbols in
GDB.
If you simply start gdb without using any command-line
options, you are prompted for what serial port to use, before you
reach the ordinary GDB prompt:
Attach /dev/ttyNN -- specify NN, or "quit" to quit:
Respond to the prompt with whatever suffix (after `/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 target (see section Commands for managing targets).
These are the startup options for beginning your GDB session with a Nindy-960 board attached:
-r port
tty (e.g. `-r a').
-O
Warning: if you specify `-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. GDB repeatedly attempts to reconnect at several different line speeds. You can abort this process with an interrupt.
-brk
BREAK signal to the target
system, in an attempt to reset it, before connecting to a Nindy target.
Warning: Many target systems do not have the hardware that this requires; it only works with a few boards.
The standard `-b' option controls the line speed used on the serial port.
reset
target m32r dev
The Motorola m68k configuration includes ColdFire support, and target command for the following ROM monitors.
target abug dev
target cpu32bug dev
target dbug dev
target est dev
target rom68k dev
If GDB is configured with m68*-ericsson-*, it will
instead have only a single special target command:
target es1800 dev
[context?]
target rombug dev
target bug dev
GDB can use the MIPS remote debugging protocol to talk to a MIPS board attached to a serial line. This is available when you configure GDB with `--target=mips-idt-ecoff'.
Use these GDB commands to specify the connection to your target board:
target mips port
gdb with the
name of your program as the argument. To connect to the board, use the
command `target mips port', where 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 load command to
download it. You can then use all the usual GDB commands.
For example, this sequence connects to the target board through a serial
port, and loads and runs a program called prog through the
debugger:
host$ gdb prog GDB is free software and ... (gdb) target mips /dev/ttyb (gdb) load prog (gdb) run
target mips hostname:portnumber
target pmon port
target ddb port
target lsi port
target r3900 dev
target array dev
GDB also supports these special commands for MIPS targets:
set processor args
show processor
set processor command to set the type of MIPS
processor when you want to access processor-type-specific registers.
For example, set processor r3041 tells GDB
to use the CPU registers appropriate for the 3041 chip.
Use the show processor command to see what MIPS processor GDB
is using. Use the info reg command to see what registers
GDB is using.
set mipsfpu double
set mipsfpu single
set mipsfpu none
show mipsfpu
mipsfpu variable with
`show mipsfpu'.
set remotedebug n
show remotedebug
remotedebug variable. If you set it to 1 using
`set remotedebug 1', every packet is displayed. If you set it
to 2, every character is displayed. You can check the current value
at any time with the command `show remotedebug'.
set timeout seconds
set retransmit-timeout seconds
show timeout
show retransmit-timeout
set timeout seconds command. The
default is 5 seconds. Similarly, you can control the timeout used while
waiting for an acknowledgement of a packet with the set
retransmit-timeout seconds command. The default is 3 seconds.
You can inspect both values with show timeout and show
retransmit-timeout. (These commands are only available when
GDB is configured for `--target=mips-idt-ecoff'.)
The timeout set by set timeout does not apply when GDB
is waiting for your program to stop. In that case, GDB waits
forever because it has no way of knowing how long the program is going
to run before stopping.
target dink32 dev
target ppcbug dev
target ppcbug1 dev
target sds dev
target op50n dev
target w89k dev
target hms dev
device and speed to control the serial line and
the communications speed used.
target e7000 dev
target sh3 dev
target sh3e dev
GDB enables developers to debug tasks running on
Sparclet targets from a Unix host.
GDB uses code that runs on
both the Unix host and on the Sparclet target. The program
gdb is installed and executed on the Unix host.
remotetimeout args
remotetimeout.
This option is set by the user, and args represents the number of
seconds GDB waits for responses.
When compiling for debugging, include the options `-g' to get debug information and `-Ttext' to relocate the program to where you wish to load it on the target. You may also want to add the options `-n' or `-N' in order to reduce the size of the sections. Example:
sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
You can use objdump to verify that the addresses are what you intended:
sparclet-aout-objdump --headers --syms prog
Once you have set
your Unix execution search path to find GDB, you are ready to
run GDB. From your Unix host, run gdb
(or sparclet-aout-gdb, depending on your installation).
GDB comes up showing the prompt:
(gdbslet)
The GDB command file lets you choose with program to debug.
(gdbslet) file prog
GDB then attempts to read the symbol table of `prog'. GDB locates the file by searching the directories listed in the command search path. If the file was compiled with debug information (option "-g"), source files will be searched as well. GDB locates the source files by searching the directories listed in the directory search path (see section Your program's environment). If it fails to find a file, it displays a message such as:
prog: No such file or directory.
When this happens, add the appropriate directories to the search paths with
the GDB commands path and dir, and execute the
target command again.
The GDB command target lets you connect to a Sparclet target.
To connect to a target on serial port "ttya", type:
(gdbslet) target sparclet /dev/ttya Remote target sparclet connected to /dev/ttya main () at ../prog.c:3
GDB displays messages like these:
Connected to ttya.
Once connected to the Sparclet target,
you can use the GDB
load command to download the file from the host to the target.
The file name and load offset should be given as arguments to the load
command.
Since the file format is aout, the program must be loaded to the starting
address. You can use objdump to find out what this value is. The load
offset is an offset which is added to the VMA (virtual memory address)
of each of the file's sections.
For instance, if the program
`prog' was linked to text address 0x1201000, with data at 0x12010160
and bss at 0x12010170, in GDB, type:
(gdbslet) load prog 0x12010000 Loading section .text, size 0xdb0 vma 0x12010000
If the code is loaded at a different address then what the program was linked
to, you may need to use the section and add-symbol-file commands
to tell GDB where to map the symbol table.
You can now begin debugging the task using GDB's execution control
commands, b, step, run, etc. See the GDB
manual for the list of commands.
(gdbslet) b main Breakpoint 1 at 0x12010000: file prog.c, line 3. (gdbslet) run Starting program: prog Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3 3 char *symarg = 0; (gdbslet) step 4 char *execarg = "hello!"; (gdbslet)
target sparclite dev
GDB may be used with a Tandem ST2000 phone switch, running Tandem's STDBUG protocol.
To connect your ST2000 to the host system, see the manufacturer's manual. Once the ST2000 is physically attached, you can run:
target st2000 dev speed
to establish it as your debugging environment. dev is normally
the name of a serial device, such as `/dev/ttya', connected to the
ST2000 via a serial line. You can instead specify dev as a TCP
connection (for example, to a serial line attached via a terminal
concentrator) using the syntax hostname:portnumber.
The load and attach commands are not defined for
this target; you must load your program into the ST2000 as you normally
would for standalone operation. GDB reads debugging information
(such as symbols) from a separate, debugging version of the program
available on your host computer.
These auxiliary GDB commands are available to help you with the ST2000 environment:
st2000 command
connect
When configured for debugging Zilog Z8000 targets, GDB includes a Z8000 simulator.
For the Z8000 family, `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.
target sim args
After specifying this target, you can debug programs for the simulated
CPU in the same style as programs for your host computer; use the
file command to load a new program image, the run command
to run your program, and so on.
As well as making available all the usual machine registers (see section Registers), the Z8000 simulator provides three additional items of information as specially named registers:
cycles
insts
time
You can refer to these values in GDB expressions with the usual conventions; for example, `b fputc if $cycles>5000' sets a conditional breakpoint that suspends only after at least 5000 simulated clock ticks.
This section describes characteristics of architectures that affect all uses of GDB with the architecture, both native and cross.
set rstack_high_address address
set rstack_high_address command. The argument should be an
address, which you probably want to precede with `0x' to specify in
hexadecimal.
show rstack_high_address
See the following section.
Alpha- and MIPS-based computers use an unusual stack frame, which sometimes requires GDB to search backward in the object code to find the beginning of a function.
To improve response time (especially for embedded applications, where GDB may be restricted to a slow serial line for this search) you may want to limit the size of this search, using one of these commands:
set heuristic-fence-post limit
heuristic-fence-post must search
and therefore the longer it takes to run.
show heuristic-fence-post
These commands are available only when GDB is configured for debugging programs on Alpha or MIPS processors.
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