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17. Configuration-Specific Information

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.

17.1 Native  
17.2 Embedded Operating Systems  
17.3 Embedded Processors  
17.4 Architectures  

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17.1 Native

This section describes details specific to particular native configurations.

17.1.1 HP-UX  
17.1.2 SVR4 process information  
17.1.3 Features for Debugging DJGPP Programs  Features specific to the DJGPP port
17.1.4 Features for Debugging MS Windows PE executables  Features specific to the Cygwin port

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17.1.1 HP-UX

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.

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17.1.2 SVR4 process information

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
Summarize available information about the process.

info proc mappings
Report on the address ranges accessible in the program, with information on whether your program may read, write, or execute each range.

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17.1.3 Features for Debugging DJGPP Programs

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
This is a prefix of DJGPP-specific commands which print information about the target system and important OS structures.

info dos sysinfo
This command displays assorted information about the underlying platform: the CPU type and features, the OS version and flavor, the DPMI version, and the available conventional and DPMI memory.

info dos gdt
info dos ldt
info dos idt
These 3 commands display entries from, respectively, Global, Local, and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor tables are data structures which store a descriptor for each segment that is currently in use. The segment's selector is an index into a descriptor table; the table entry for that index holds the descriptor's base address and limit, and its attributes and access rights.

A typical DJGPP program uses 3 segments: a code segment, a data segment (used for both data and the stack), and a DOS segment (which allows access to DOS/BIOS data structures and absolute addresses in conventional memory). However, the DPMI host will usually define additional segments in order to support the DPMI environment.

These commands allow to display entries from the descriptor tables. Without an argument, all entries from the specified table are displayed. An argument, which should be an integer expression, means display a single entry whose index is given by the argument. For example, here's a convenient way to display information about the debugged program's data segment:

(gdb) info dos ldt $ds
0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)

This comes in handy when you want to see whether a pointer is outside the data segment's limit (i.e. garbled).

info dos pde
info dos pte
These two commands display entries from, respectively, the Page Directory and the Page Tables. Page Directories and Page Tables are data structures which control how virtual memory addresses are mapped into physical addresses. A Page Table includes an entry for every page of memory that is mapped into the program's address space; there may be several Page Tables, each one holding up to 4096 entries. A Page Directory has up to 4096 entries, one each for every Page Table that is currently in use.

Without an argument, info dos pde displays the entire Page Directory, and info dos pte displays all the entries in all of the Page Tables. An argument, an integer expression, given to the info dos pde command means display only that entry from the Page Directory table. An argument given to the info dos pte command means display entries from a single Page Table, the one pointed to by the specified entry in the Page Directory.

These commands are useful when your program uses DMA (Direct Memory Access), which needs physical addresses to program the DMA controller.

These commands are supported only with some DPMI servers.

info dos address-pte addr
This command displays the Page Table entry for a specified linear address. The argument linear address addr should already have the appropriate segment's base address added to it, because this command accepts addresses which may belong to any segment. For example, here's how to display the Page Table entry for the page where the variable i is stored:

(gdb) info dos address-pte __djgpp_base_address + (char *)&i
Page Table entry for address 0x11a00d30:
Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30 

This says that 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:

(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

(The + 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.

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17.1.4 Features for Debugging MS Windows PE executables

GDB supports native debugging of MS Windows programs, and defines a few commands specific to the Cygwin port. This subsection describes those commands.

info w32
This is a prefix of MS Windows specific commands which print information about the target system and important OS structures.

info w32 selector
This command displays information returned by the Win32 API GetThreadSelectorEntry function. It takes an optional argument that is evaluated to a long value to give the information about this given selector. Without argument, this command displays information about the the six segment registers.

info dll
This is a Cygwin specific alias of info shared.

This command loads symbols from a dll similarly to add-sym command but without the need to specify a base address.

set new-console mode
If mode is on the debuggee will be started in a new console on next start. If mode is offi, the debuggee will be started in the same console as the debugger.

show new-console
Displays whether a new console is used when the debuggee is started.

set new-group mode
This boolean value controls whether the debuggee should start a new group or stay in the same group as the debugger. This affects the way the Windows OS handles Ctrl-C.

show new-group
Displays current value of new-group boolean.

set debugevents
This boolean value adds debug output concerning events seen by the debugger.

set debugexec
This boolean value adds debug output concerning execute events seen by the debugger.

set debugexceptions
This boolean value adds debug ouptut concerning exception events seen by the debugger.

set debugmemory
This boolean value adds debug ouptut concerning memory events seen by the debugger.

set shell
This boolean values specifies whether the debuggee is called via a shell or directly (default value is on).

show shell
Displays if the debuggee will be started with a shell.

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17.2 Embedded Operating Systems

This section describes configurations involving the debugging of embedded operating systems that are available for several different architectures.

17.2.1 Using GDB with VxWorks  

GDB includes the ability to debug programs running on various real-time operating systems.

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17.2.1 Using GDB with VxWorks

target vxworks machinename
A VxWorks system, attached via TCP/IP. The argument machinename is the target system's machine name or IP address.

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
All VxWorks-based targets now support the option 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) Connecting to VxWorks VxWorks download Running tasks  

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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.

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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.)

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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.

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17.3 Embedded Processors

This section goes into details specific to particular embedded configurations.

17.3.1 ARM  
17.3.2 Hitachi H8/300  
17.3.3 H8/500  Hitachi H8/500
17.3.4 Intel i960  
17.3.5 Mitsubishi M32R/D  
17.3.6 M68k  Motorola M68K
17.3.7 M88K  Motorola M88K
17.3.8 MIPS Embedded  
17.3.10 HP PA Embedded  
17.3.9 PowerPC  
17.3.11 Hitachi SH  
17.3.12 Tsqware Sparclet  
17.3.13 Fujitsu Sparclite  
17.3.14 Tandem ST2000  
17.3.15 Zilog Z8000  

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17.3.1 ARM

target rdi dev
ARM Angel monitor, via RDI library interface to ADP protocol. You may use this target to communicate with both boards running the Angel monitor, or with the EmbeddedICE JTAG debug device.

target rdp dev
ARM Demon monitor.

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17.3.2 Hitachi H8/300

target hms dev
A Hitachi SH, H8/300, or H8/500 board, attached via serial line to your host. Use special commands device and speed to control the serial line and the communications speed used.

target e7000 dev
E7000 emulator for Hitachi H8 and SH.

target sh3 dev
target sh3e dev
Hitachi SH-3 and SH-3E target systems.

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:

  1. that you want to use `target hms', the remote debugging interface for Hitachi microprocessors, or `target e7000', the in-circuit emulator for the Hitachi SH and the Hitachi 300H. (`target hms' is the default when GDB is configured specifically for the Hitachi SH, H8/300, or H8/500.)

  2. what serial device connects your host to your Hitachi board (the first serial device available on your host is the default).

  3. what speed to use over the serial device. Connecting to Hitachi boards Using the E7000 in-circuit emulator  Using the E7000 In-Circuit Emulator. Special GDB commands for Hitachi micros  

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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 use asynctsr to 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 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 20020330, 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.

[ < ] [ > ]   [ << ] [ Up ] [ >> ]         [Top] [Contents] [Index] [ ? ] Using the E7000 in-circuit emulator

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
Use this form if your E7000 is connected to a serial port. The port argument identifies what serial port to use (for example, `com2'). The third argument is the line speed in bits per second (for example, `9600').

target e7000 hostname
If your E7000 is installed as a host on a TCP/IP network, you can just specify its hostname; GDB uses telnet to connect.

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Some GDB commands are available only for the H8/300:

set machine h8300
set machine h8300h
Condition GDB for one of the two variants of the H8/300 architecture with `set machine'. You can use `show machine' to check which variant is currently in effect.

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17.3.3 H8/500

set memory mod
show memory
Specify which H8/500 memory model (mod) you are using with `set memory'; check which memory model is in effect with `show memory'. The accepted values for mod are small, big, medium, and compact.

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17.3.4 Intel i960

target mon960 dev
MON960 monitor for Intel i960.

target nindy devicename
An Intel 960 board controlled by a Nindy Monitor. devicename is the name of the serial device to use for the connection, e.g. `/dev/ttya'.

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:

With the Nindy interface to an Intel 960 board, load downloads filename to the 960 as well as adding its symbols in GDB. Startup with Nindy Options for Nindy Nindy reset command  

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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).

[ < ] [ > ]   [ << ] [ Up ] [ >> ]         [Top] [Contents] [Index] [ ? ] Options for Nindy

These are the startup options for beginning your GDB session with a Nindy-960 board attached:

-r 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 GDB is configured for the Intel 960 target architecture. You may specify port as any of: a full pathname (e.g. `-r /dev/ttya'), a device name in `/dev' (e.g. `-r ttya'), or simply the unique suffix for a specific tty (e.g. `-r a').

(An uppercase letter "O", not a zero.) Specify that GDB should use the "old" Nindy monitor protocol to connect to the target system. This option is only available when GDB is configured for the Intel 960 target architecture.

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.

Specify that GDB should first send a 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.

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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.

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17.3.5 Mitsubishi M32R/D

target m32r dev
Mitsubishi M32R/D ROM monitor.

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17.3.6 M68k

The Motorola m68k configuration includes ColdFire support, and target command for the following ROM monitors.

target abug dev
ABug ROM monitor for M68K.

target cpu32bug dev
CPU32BUG monitor, running on a CPU32 (M68K) board.

target dbug dev
dBUG ROM monitor for Motorola ColdFire.

target est dev
EST-300 ICE monitor, running on a CPU32 (M68K) board.

target rom68k dev
ROM 68K monitor, running on an M68K IDP board.

If GDB is configured with m68*-ericsson-*, it will instead have only a single special target command:

target es1800 dev
ES-1800 emulator for M68K.


target rombug dev
ROMBUG ROM monitor for OS/9000.

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17.3.7 M88K

target bug dev
BUG monitor, running on a MVME187 (m88k) board.

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17.3.8 MIPS Embedded

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
To run a program on the board, start up 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
On some GDB host configurations, you can specify a TCP connection (for instance, to a serial line managed by a terminal concentrator) instead of a serial port, using the syntax `hostname:portnumber'.

target pmon port
PMON ROM monitor.

target ddb port
NEC's DDB variant of PMON for Vr4300.

target lsi port
LSI variant of PMON.

target r3900 dev
Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.

target array dev
Array Tech LSI33K RAID controller board.

GDB also supports these special commands for MIPS targets:

set processor args
show processor
Use the 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
If your target board does not support the MIPS floating point coprocessor, you should use the command `set mipsfpu none' (if you need this, you may wish to put the command in your GDB init file). This tells GDB how to find the return value of functions which return floating point values. It also allows GDB to avoid saving the floating point registers when calling functions on the board. If you are using a floating point coprocessor with only single precision floating point support, as on the R4650 processor, use the command `set mipsfpu single'. The default double precision floating point coprocessor may be selected using `set mipsfpu double'.

In previous versions the only choices were double precision or no floating point, so `set mipsfpu on' will select double precision and `set mipsfpu off' will select no floating point.

As usual, you can inquire about the mipsfpu variable with `show mipsfpu'.

set remotedebug n
show remotedebug
You can see some debugging information about communications with the board by setting the 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
You can control the timeout used while waiting for a packet, in the MIPS remote protocol, with the 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.

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17.3.9 PowerPC

target dink32 dev
DINK32 ROM monitor.

target ppcbug dev
target ppcbug1 dev
PPCBUG ROM monitor for PowerPC.

target sds dev
SDS monitor, running on a PowerPC board (such as Motorola's ADS).

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17.3.10 HP PA Embedded

target op50n dev
OP50N monitor, running on an OKI HPPA board.

target w89k dev
W89K monitor, running on a Winbond HPPA board.

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17.3.11 Hitachi SH

target hms dev
A Hitachi SH board attached via serial line to your host. Use special commands device and speed to control the serial line and the communications speed used.

target e7000 dev
E7000 emulator for Hitachi SH.

target sh3 dev
target sh3e dev
Hitachi SH-3 and SH-3E target systems.

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17.3.12 Tsqware Sparclet

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
GDB supports the option 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) Setting file to debug  Setting the file to debug Connecting to Sparclet Sparclet download Running and debugging  

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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.

[ < ] [ > ]   [ << ] [ Up ] [ >> ]         [Top] [Contents] [Index] [ ? ] Connecting to Sparclet

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.

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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.

[ < ] [ > ]   [ << ] [ Up ] [ >> ]         [Top] [Contents] [Index] [ ? ] Running and debugging

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!";

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17.3.13 Fujitsu Sparclite

target sparclite dev
Fujitsu sparclite boards, used only for the purpose of loading. You must use an additional command to debug the program. For example: target remote dev using GDB standard remote protocol.

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17.3.14 Tandem ST2000

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
Send a command to the STDBUG monitor. See the manufacturer's manual for available commands.

Connect the controlling terminal to the STDBUG command monitor. When you are done interacting with STDBUG, typing either of two character sequences gets you back to the GDB command prompt: RET~. (Return, followed by tilde and period) or RET~C-d (Return, followed by tilde and control-D).

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17.3.15 Zilog Z8000

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
Debug programs on a simulated CPU. If the simulator supports setup options, specify them via 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:

Counts clock-ticks in the simulator.

Counts instructions run in the simulator.

Execution time in 60ths of a second.

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.

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17.4 Architectures

This section describes characteristics of architectures that affect all uses of GDB with the architecture, both native and cross.

17.4.1 A29K  
17.4.2 Alpha  
17.4.3 MIPS  

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17.4.1 A29K

set rstack_high_address address
On AMD 29000 family processors, registers are saved in a separate register stack. There is no way for GDB to determine the extent of this stack. Normally, GDB just assumes that the stack is "large enough". This may result in GDB referencing memory locations that do not exist. If necessary, you can get around this problem by specifying the ending address of the register stack with the 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
Display the current limit of the register stack, on AMD 29000 family processors.

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17.4.2 Alpha

See the following section.

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17.4.3 MIPS

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
Restrict GDB to examining at most limit bytes in its search for the beginning of a function. A value of 0 (the default) means there is no limit. However, except for 0, the larger the limit the more bytes heuristic-fence-post must search and therefore the longer it takes to run.

show heuristic-fence-post
Display the current limit.

These commands are available only when GDB is configured for debugging programs on Alpha or MIPS processors.

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