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# 18. 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.

> 18.1 Native |  |
> 18.2 Embedded Operating Systems |  |
> 18.3 Embedded Processors |  |
> 18.4 Architectures |  |

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## 18.1 Native

This section describes details specific to particular native configurations.

> 18.1.1 HP-UX |  |
> 18.1.2 BSD libkvm Interface |  | Debugging BSD kernel memory images
> 18.1.3 SVR4 Process Information |  | SVR4 process information
> 18.1.4 Features for Debugging DJGPP Programs |  | Features specific to the DJGPP port
> 18.1.5 Features for Debugging MS Windows PE Executables |  | Features specific to the Cygwin port
> 18.1.6 Commands Specific to GNU Hurd Systems |  | Features specific to GNU Hurd
> 18.1.7 QNX Neutrino |  | Features specific to QNX Neutrino

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### 18.1.1 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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### 18.1.2 BSD libkvm Interface

BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory interface that provides a uniform interface for accessing kernel virtual memory images, including live systems and crash dumps. GDB uses this interface to allow you to debug live kernels and kernel crash dumps on many native BSD configurations. This is implemented as a special `kvm` debugging target. For debugging a live system, load the currently running kernel into GDB and connect to the `kvm` target:

    (gdb) target kvm

For debugging crash dumps, provide the file name of the crash dump as an argument:

    (gdb) target kvm /var/crash/bsd.0

Once connected to the `kvm` target, the following commands are available:

`kvm pcb`
  Set current context from the Process Control Block (PCB) address.

`kvm proc`
  Set current context from proc address. This command isn't available on modern FreeBSD systems.

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### 18.1.3 SVR4 Process Information

Many versions of SVR4 and compatible systems 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 information about the process running your program, or about any process running on your system. `info proc` works only on SVR4 systems that include the `procfs` code. This includes, as of this writing, GNU/Linux, OSF/1 (Digital Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.

`info proc`
`info proc process-id`
  Summarize available information about any running process. If a process ID is specified by process-id, display information about that process; otherwise display information about the program being debugged. The summary includes the debugged process ID, the command line used to invoke it, its current working directory, and its executable file's absolute file name.

  On some systems, process-id can be of the form ``[pid]/tid'` which specifies a certain thread ID within a process. If the optional pid part is missing, it means a thread from the process being debugged (the leading ``/'` still needs to be present, or else GDB will interpret the number as a process ID rather than a thread ID).

`info proc mappings`
  Report the memory address space ranges accessible in the program, with information on whether the process has read, write, or execute access rights to each range. On GNU/Linux systems, each memory range includes the object file which is mapped to that range, instead of the memory access rights to that range.

`info proc stat`
`info proc status`
  These subcommands are specific to GNU/Linux systems. They show the process-related information, including the user ID and group ID; how many threads are there in the process; its virtual memory usage; the signals that are pending, blocked, and ignored; its TTY; its consumption of system and user time; its stack size; its ``nice'` value; etc. For more information, see the ``proc'` man page (type `man 5 proc` from your shell prompt).

`info proc all`
  Show all the information about the process described under all of the above `info proc` subcommands.

`set procfs-trace`
  This command enables and disables tracing of `procfs` API calls.

`show procfs-trace`
  Show the current state of `procfs` API call tracing.

`set procfs-file file`
  Tell GDB to write `procfs` API trace to the named file. GDB appends the trace info to the previous contents of the file. The default is to display the trace on the standard output.

`show procfs-file`
  Show the file to which `procfs` API trace is written.

`proc-trace-entry`
`proc-trace-exit`
`proc-untrace-entry`
`proc-untrace-exit`
  These commands enable and disable tracing of entries into and exits from the `syscall` interface.

`info pidlist`
  For QNX Neutrino only, this command displays the list of all the processes and all the threads within each process.

`info meminfo`
  For QNX Neutrino only, this command displays the list of all mapinfos.

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### 18.1.4 Features for Debugging DJGPP Programs

DJGPP is a port of the 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 addr is a linear address which 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 a 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 shows 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 clearly shows that this DPMI server maps the addresses in conventional memory 1:1, i.e. the physical (`0x00029000` + `0x110`) and linear (`0x29110`) addresses are identical.

  This command is supported only with some DPMI servers.

In addition to native debugging, the DJGPP port supports remote debugging via a serial data link. The following commands are specific to remote serial debugging in the DJGPP port of GDB.

`set com1base addr`
  This command sets the base I/O port address of the ``COM1'` serial port.

`set com1irq irq`
  This command sets the Interrupt Request (`IRQ`) line to use for the ``COM1'` serial port.

  There are similar commands ``set com2base'`, ``set com3irq'`, etc. for setting the port address and the `IRQ` lines for the other 3 COM ports.

  The related commands ``show com1base'`, ``show com1irq'` etc. display the current settings of the base address and the `IRQ` lines used by the COM ports.

`info serial`
  This command prints the status of the 4 DOS serial ports. For each port, it prints whether it's active or not, its I/O base address and IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the counts of various errors encountered so far.

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### 18.1.5 Features for Debugging MS Windows PE Executables

GDB supports native debugging of MS Windows programs, including DLLs with and without symbolic debugging information. There are various additional Cygwin-specific commands, described in this section. Working with DLLs that have no debugging symbols is described in 18.1.5.1 Support for DLLs without Debugging Symbols.

`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 six segment registers.

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

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

`set cygwin-exceptions mode`
  If mode is `on`, GDB will break on exceptions that happen inside the Cygwin DLL. If mode is `off`, GDB will delay recognition of exceptions, and may ignore some exceptions which seem to be caused by internal Cygwin DLL "bookkeeping". This option is meant primarily for debugging the Cygwin DLL itself; the default value is `off` to avoid annoying GDB users with false `SIGSEGV` signals.

`show cygwin-exceptions`
  Displays whether GDB will break on exceptions that happen inside the Cygwin DLL itself.

`set new-console mode`
  If mode is `on` the debuggee will be started in a new console on next start. If mode is `off`i, 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 kernel events related to the debuggee seen by the debugger. This includes events that signal thread and process creation and exit, DLL loading and unloading, console interrupts, and debugging messages produced by the Windows `OutputDebugString` API call.

`set debugexec`
  This boolean value adds debug output concerning execute events (such as resume thread) seen by the debugger.

`set debugexceptions`
  This boolean value adds debug output concerning exceptions in the debuggee seen by the debugger.

`set debugmemory`
  This boolean value adds debug output concerning debuggee memory reads and writes 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.

> 18.1.5.1 Support for DLLs without Debugging Symbols |  | Support for DLLs without debugging symbols

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#### 18.1.5.1 Support for DLLs without Debugging Symbols

Very often on windows, some of the DLLs that your program relies on do not include symbolic debugging information (for example, ``kernel32.dll'`). When GDB doesn't recognize any debugging symbols in a DLL, it relies on the minimal amount of symbolic information contained in the DLL's export table. This section describes working with such symbols, known internally to GDB as "minimal symbols".

Note that before the debugged program has started execution, no DLLs will have been loaded. The easiest way around this problem is simply to start the program -- either by setting a breakpoint or letting the program run once to completion. It is also possible to force GDB to load a particular DLL before starting the executable --- see the shared library information in 15.1 Commands to Specify Files, or the `dll-symbols` command in 18.1.5 Features for Debugging MS Windows PE Executables. Currently, explicitly loading symbols from a DLL with no debugging information will cause the symbol names to be duplicated in GDB's lookup table, which may adversely affect symbol lookup performance.

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#### 18.1.5.2 DLL Name Prefixes

In keeping with the naming conventions used by the Microsoft debugging tools, DLL export symbols are made available with a prefix based on the DLL name, for instance `KERNEL32!CreateFileA`. The plain name is also entered into the symbol table, so `CreateFileA` is often sufficient. In some cases there will be name clashes within a program (particularly if the executable itself includes full debugging symbols) necessitating the use of the fully qualified name when referring to the contents of the DLL. Use single-quotes around the name to avoid the exclamation mark ("!") being interpreted as a language operator.

Note that the internal name of the DLL may be all upper-case, even though the file name of the DLL is lower-case, or vice-versa. Since symbols within GDB are case-sensitive this may cause some confusion. If in doubt, try the `info functions` and `info variables` commands or even `maint print msymbols` (see section 13. Examining the Symbol Table). Here's an example:

    (gdb) info function CreateFileA
    All functions matching regular expression "CreateFileA":

    Non-debugging symbols:
    0x77e885f4  CreateFileA
    0x77e885f4  KERNEL32!CreateFileA

    (gdb) info function !
    All functions matching regular expression "!":

    Non-debugging symbols:
    0x6100114c  cygwin1!__assert
    0x61004034  cygwin1!_dll_crt0@0
    0x61004240  cygwin1!dll_crt0(per_process *)
    [etc...]

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#### 18.1.5.3 Working with Minimal Symbols

Symbols extracted from a DLL's export table do not contain very much type information. All that GDB can do is guess whether a symbol refers to a function or variable depending on the linker section that contains the symbol. Also note that the actual contents of the memory contained in a DLL are not available unless the program is running. This means that you cannot examine the contents of a variable or disassemble a function within a DLL without a running program.

Variables are generally treated as pointers and dereferenced automatically. For this reason, it is often necessary to prefix a variable name with the address-of operator ("&") and provide explicit type information in the command. Here's an example of the type of problem:

    (gdb) print 'cygwin1!__argv'
    $1 = 268572168

    (gdb) x 'cygwin1!__argv'
    0x10021610:      "\230y\""

And two possible solutions:

    (gdb) print ((char **)'cygwin1!__argv')[0]
    $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"

    (gdb) x/2x &'cygwin1!__argv'
    0x610c0aa8 <cygwin1!__argv>:    0x10021608      0x00000000
    (gdb) x/x 0x10021608
    0x10021608:     0x0022fd98
    (gdb) x/s 0x0022fd98
    0x22fd98:        "/cygdrive/c/mydirectory/myprogram"

Setting a break point within a DLL is possible even before the program starts execution. However, under these circumstances, GDB can't examine the initial instructions of the function in order to skip the function's frame set-up code. You can work around this by using "*&" to set the breakpoint at a raw memory address:

    (gdb) break *&'python22!PyOS_Readline'
    Breakpoint 1 at 0x1e04eff0

The author of these extensions is not entirely convinced that setting a break point within a shared DLL like ``kernel32.dll'` is completely safe.

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### 18.1.6 Commands Specific to GNU Hurd Systems

This subsection describes GDB commands specific to the GNU Hurd native debugging.

`set signals`
`set sigs`
  This command toggles the state of inferior signal interception by GDB. Mach exceptions, such as breakpoint traps, are not affected by this command. `sigs` is a shorthand alias for `signals`.

`show signals`
`show sigs`
  Show the current state of intercepting inferior's signals.

`set signal-thread`
`set sigthread`
  This command tells GDB which thread is the `libc` signal thread. That thread is run when a signal is delivered to a running process. `set sigthread` is the shorthand alias of `set signal-thread`.

`show signal-thread`
`show sigthread`
  These two commands show which thread will run when the inferior is delivered a signal.

`set stopped`
  This commands tells GDB that the inferior process is stopped, as with the `SIGSTOP` signal. The stopped process can be continued by delivering a signal to it.

`show stopped`
  This command shows whether GDB thinks the debuggee is stopped.

`set exceptions`
  Use this command to turn off trapping of exceptions in the inferior. When exception trapping is off, neither breakpoints nor single-stepping will work. To restore the default, set exception trapping on.

`show exceptions`
  Show the current state of trapping exceptions in the inferior.

`set task pause`
  This command toggles task suspension when GDB has control. Setting it to on takes effect immediately, and the task is suspended whenever GDB gets control. Setting it to off will take effect the next time the inferior is continued. If this option is set to off, you can use `set thread default pause on` or `set thread pause on` (see below) to pause individual threads.

`show task pause`
  Show the current state of task suspension.

`set task detach-suspend-count`
  This command sets the suspend count the task will be left with when GDB detaches from it.

`show task detach-suspend-count`
  Show the suspend count the task will be left with when detaching.

`set task exception-port`
`set task excp`
  This command sets the task exception port to which GDB will forward exceptions. The argument should be the value of the send rights of the task. `set task excp` is a shorthand alias.

`set noninvasive`
  This command switches GDB to a mode that is the least invasive as far as interfering with the inferior is concerned. This is the same as using `set task pause`, `set exceptions`, and `set signals` to values opposite to the defaults.

`info send-rights`
`info receive-rights`
`info port-rights`
`info port-sets`
`info dead-names`
`info ports`
`info psets`
  These commands display information about, respectively, send rights, receive rights, port rights, port sets, and dead names of a task. There are also shorthand aliases: `info ports` for `info port-rights` and `info psets` for `info port-sets`.

`set thread pause`
  This command toggles current thread suspension when GDB has control. Setting it to on takes effect immediately, and the current thread is suspended whenever GDB gets control. Setting it to off will take effect the next time the inferior is continued. Normally, this command has no effect, since when GDB has control, the whole task is suspended. However, if you used `set task pause off` (see above), this command comes in handy to suspend only the current thread.

`show thread pause`
  This command shows the state of current thread suspension.

`set thread run`
  This command sets whether the current thread is allowed to run.

`show thread run`
  Show whether the current thread is allowed to run.

`set thread detach-suspend-count`
  This command sets the suspend count GDB will leave on a thread when detaching. This number is relative to the suspend count found by GDB when it notices the thread; use `set thread takeover-suspend-count` to force it to an absolute value.

`show thread detach-suspend-count`
  Show the suspend count GDB will leave on the thread when detaching.

`set thread exception-port`
`set thread excp`
  Set the thread exception port to which to forward exceptions. This overrides the port set by `set task exception-port` (see above). `set thread excp` is the shorthand alias.

`set thread takeover-suspend-count`
  Normally, GDB's thread suspend counts are relative to the value GDB finds when it notices each thread. This command changes the suspend counts to be absolute instead.

`set thread default`
`show thread default`
  Each of the above `set thread` commands has a `set thread default` counterpart (e.g., `set thread default pause`, `set thread default exception-port`, etc.). The `thread default` variety of commands sets the default thread properties for all threads; you can then change the properties of individual threads with the non-default commands.

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### 18.1.7 QNX Neutrino

GDB provides the following commands specific to the QNX Neutrino target:

`set debug nto-debug`
  When set to on, enables debugging messages specific to the QNX Neutrino support.

`show debug nto-debug`
  Show the current state of QNX Neutrino messages.

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## 18.2 Embedded Operating Systems

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

> 18.2.1 Using GDB with VxWorks |  |

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

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### 18.2.1 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)

> 18.2.1.1 Connecting to VxWorks |  |
> 18.2.1.2 VxWorks Download |  | VxWorks download
> 18.2.1.3 Running Tasks |  | Running tasks

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#### 18.2.1.1 Connecting to VxWorks

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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#### 18.2.1.2 VxWorks Download

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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#### 18.2.1.3 Running Tasks

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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## 18.3 Embedded Processors

This section goes into details specific to particular embedded configurations.

Whenever a specific embedded processor has a simulator, GDB allows to send an arbitrary command to the simulator.

`sim command`
  Send an arbitrary command string to the simulator. Consult the documentation for the specific simulator in use for information about acceptable commands.

> 18.3.1 ARM |  | ARM RDI
> 18.3.2 Renesas M32R/D and M32R/SDI |  | Renesas M32R/D
> 18.3.3 M68k |  | Motorola M68K
> 18.3.4 MIPS Embedded |  |
> 18.3.5 OpenRISC 1000 |  | OpenRisc 1000
> 18.3.7 HP PA Embedded |  |
> 18.3.6 PowerPC Embedded |  |
> 18.3.8 Tsqware Sparclet |  |
> 18.3.9 Fujitsu Sparclite |  |
> 18.3.10 Zilog Z8000 |  |
> 18.3.11 Atmel AVR |  |
> 18.3.12 CRIS |  |
> 18.3.13 Renesas Super-H |  |

[ < ] | [ > ] |  | [ << ] | [ Up ] | [ >> ] |  |  |  |  | [Top] | [Contents] | [Index] | [ ? ]

### 18.3.1 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.

GDB provides the following ARM-specific commands:

`set arm disassembler`
  This commands selects from a list of disassembly styles. The `"std"` style is the standard style.

`show arm disassembler`
  Show the current disassembly style.

`set arm apcs32`
  This command toggles ARM operation mode between 32-bit and 26-bit.

`show arm apcs32`
  Display the current usage of the ARM 32-bit mode.

`set arm fpu fputype`
  This command sets the ARM floating-point unit (FPU) type. The argument fputype can be one of these:

  `auto`
    Determine the FPU type by querying the OS ABI.
  `softfpa`
    Software FPU, with mixed-endian doubles on little-endian ARM processors.
  `fpa`
    GCC-compiled FPA co-processor.
  `softvfp`
    Software FPU with pure-endian doubles.
  `vfp`
    VFP co-processor.

`show arm fpu`
  Show the current type of the FPU.

`set arm abi`
  This command forces GDB to use the specified ABI.

`show arm abi`
  Show the currently used ABI.

`set debug arm`
  Toggle whether to display ARM-specific debugging messages from the ARM target support subsystem.

`show debug arm`
  Show whether ARM-specific debugging messages are enabled.

The following commands are available when an ARM target is debugged using the RDI interface:

`rdilogfile [file]`
  Set the filename for the ADP (Angel Debugger Protocol) packet log. With an argument, sets the log file to the specified file. With no argument, show the current log file name. The default log file is ``rdi.log'`.

`rdilogenable [arg]`
  Control logging of ADP packets. With an argument of 1 or `"yes"` enables logging, with an argument 0 or `"no"` disables it. With no arguments displays the current setting. When logging is enabled, ADP packets exchanged between GDB and the RDI target device are logged to a file.

`set rdiromatzero`
  Tell GDB whether the target has ROM at address 0. If on, vector catching is disabled, so that zero address can be used. If off (the default), vector catching is enabled. For this command to take effect, it needs to be invoked prior to the `target rdi` command.

`show rdiromatzero`
  Show the current setting of ROM at zero address.

`set rdiheartbeat`
  Enable or disable RDI heartbeat packets. It is not recommended to turn on this option, since it confuses ARM and EPI JTAG interface, as well as the Angel monitor.

`show rdiheartbeat`
  Show the setting of RDI heartbeat packets.

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### 18.3.2 Renesas M32R/D and M32R/SDI

`target m32r dev`
  Renesas M32R/D ROM monitor.

`target m32rsdi dev`
  Renesas M32R SDI server, connected via parallel port to the board.

The following GDB commands are specific to the M32R monitor:

`set download-path path`
  Set the default path for finding downloadable SREC files.

`show download-path`
  Show the default path for downloadable SREC files.

`set board-address addr`
  Set the IP address for the M32R-EVA target board.

`show board-address`
  Show the current IP address of the target board.

`set server-address addr`
  Set the IP address for the download server, which is the GDB's host machine.

`show server-address`
  Display the IP address of the download server.

`upload [file]`
  Upload the specified SREC file via the monitor's Ethernet upload capability. If no file argument is given, the current executable file is uploaded.

`tload [file]`
  Test the `upload` command.

The following commands are available for M32R/SDI:

`sdireset`
  This command resets the SDI connection.

`sdistatus`
  This command shows the SDI connection status.

`debug_chaos`
  Instructs the remote that M32R/Chaos debugging is to be used.

`use_debug_dma`
  Instructs the remote to use the DEBUG_DMA method of accessing memory.

`use_mon_code`
  Instructs the remote to use the MON_CODE method of accessing memory.

`use_ib_break`
  Instructs the remote to set breakpoints by IB break.

`use_dbt_break`
  Instructs the remote to set breakpoints by DBT.

[ < ] | [ > ] |  | [ << ] | [ Up ] | [ >> ] |  |  |  |  | [Top] | [Contents] | [Index] | [ ? ]

### 18.3.3 M68k

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

`target dbug dev`
  dBUG ROM monitor for Motorola ColdFire.

[ < ] | [ > ] |  | [ << ] | [ Up ] | [ >> ] |  |  |  |  | [Top] | [Contents] | [Index] | [ ? ]

### 18.3.4 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 mipsfpu double`
`set mipsfpu single`
`set mipsfpu none`
`set mipsfpu auto`
`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 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.

`set syn-garbage-limit num`
  Limit the maximum number of characters GDB should ignore when it tries to synchronize with the remote target. The default is 10 characters. Setting the limit to -1 means there's no limit.

`show syn-garbage-limit`
  Show the current limit on the number of characters to ignore when trying to synchronize with the remote system.

`set monitor-prompt prompt`
  Tell GDB to expect the specified prompt string from the remote monitor. The default depends on the target:
  pmon target
    ``PMON'`
  ddb target
    ``NEC010'`
  lsi target
    ``PMON>'`

`show monitor-prompt`
  Show the current strings GDB expects as the prompt from the remote monitor.

`set monitor-warnings`
  Enable or disable monitor warnings about hardware breakpoints. This has effect only for the `lsi` target. When on, GDB will display warning messages whose codes are returned by the `lsi` PMON monitor for breakpoint commands.

`show monitor-warnings`
  Show the current setting of printing monitor warnings.

`pmon command`
  This command allows sending an arbitrary command string to the monitor. The monitor must be in debug mode for this to work.

[ < ] | [ > ] |  | [ << ] | [ Up ] | [ >> ] |  |  |  |  | [Top] | [Contents] | [Index] | [ ? ]

### 18.3.5 OpenRISC 1000

See OR1k Architecture document (www.opencores.org) for more information about platform and commands.

`target jtag jtag://host:port`

  Connects to remote JTAG server. JTAG remote server can be either an or1ksim or JTAG server, connected via parallel port to the board.

  Example: `target jtag jtag://localhost:9999`

`or1ksim command`
  If connected to `or1ksim` OpenRISC 1000 Architectural Simulator, proprietary commands can be executed.

`info or1k spr`
  Displays spr groups.

`info or1k spr group`
`info or1k spr groupno`
  Displays register names in selected group.

`info or1k spr group register`
`info or1k spr register`
`info or1k spr groupno registerno`
`info or1k spr registerno`
  Shows information about specified spr register.

`spr group register value`
`spr register value`
`spr groupno registerno value`
`spr registerno value`
  Writes value to specified spr register.

Some implementations of OpenRISC 1000 Architecture also have hardware trace. It is very similar to GDB trace, except it does not interfere with normal program execution and is thus much faster. Hardware breakpoints/watchpoint triggers can be set using:

`$LEA/$LDATA`
  Load effective address/data
`$SEA/$SDATA`
  Store effective address/data
`$AEA/$ADATA`
  Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
`$FETCH`
  Fetch data

When triggered, it can capture low level data, like: `PC`, `LSEA`, `LDATA`, `SDATA`, `READSPR`, `WRITESPR`, `INSTR`.

`htrace` commands:

`hwatch conditional`
  Set hardware watchpoint on combination of Load/Store Effective Address(es) or Data. For example:

  `hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)`

  `hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)`

`htrace info`
  Display information about current HW trace configuration.

`htrace trigger conditional`
  Set starting criteria for HW trace.

`htrace qualifier conditional`
  Set acquisition qualifier for HW trace.

`htrace stop conditional`
  Set HW trace stopping criteria.

`htrace record [data]*`
  Selects the data to be recorded, when qualifier is met and HW trace was triggered.

`htrace enable`
`htrace disable`
  Enables/disables the HW trace.

`htrace rewind [filename]`
  Clears currently recorded trace data.

  If filename is specified, new trace file is made and any newly collected data will be written there.

`htrace print [start [len]]`
  Prints trace buffer, using current record configuration.

`htrace mode continuous`
  Set continuous trace mode.

`htrace mode suspend`
  Set suspend trace mode.

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### 18.3.6 PowerPC Embedded

GDB provides the following PowerPC-specific commands:

`set powerpc soft-float`
`show powerpc soft-float`
  Force GDB to use (or not use) a software floating point calling convention. By default, GDB selects the calling convention based on the selected architecture and the provided executable file.

`set powerpc vector-abi`
`show powerpc vector-abi`
  Force GDB to use the specified calling convention for vector arguments and return values. The valid options are ``auto'`; ``generic'`, to avoid vector registers even if they are present; ``altivec'`, to use AltiVec registers; and ``spe'` to use SPE registers. By default, GDB selects the calling convention based on the selected architecture and the provided executable file.

`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).

The following commands specific to the SDS protocol are supported by GDB:

`set sdstimeout nsec`
  Set the timeout for SDS protocol reads to be nsec seconds. The default is 2 seconds.

`show sdstimeout`
  Show the current value of the SDS timeout.

`sds command`
  Send the specified command string to the SDS monitor.

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### 18.3.7 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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### 18.3.8 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)

> 18.3.8.1 Setting File to Debug |  | Setting the file to debug
> 18.3.8.2 Connecting to Sparclet |  |
> 18.3.8.3 Sparclet Download |  | Sparclet download
> 18.3.8.4 Running and Debugging |  | Running and debugging

[ < ] | [ > ] |  | [ << ] | [ Up ] | [ >> ] |  |  |  |  | [Top] | [Contents] | [Index] | [ ? ]

#### 18.3.8.1 Setting File to Debug

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.

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#### 18.3.8.2 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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#### 18.3.8.3 Sparclet Download

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] | [ ? ]

#### 18.3.8.4 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!";
    (gdbslet)

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### 18.3.9 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.

[ < ] | [ > ] |  | [ << ] | [ Up ] | [ >> ] |  |  |  |  | [Top] | [Contents] | [Index] | [ ? ]

### 18.3.10 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:

`cycles`
  Counts clock-ticks in the simulator.

`insts`
  Counts instructions run in the simulator.

`time`
  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.

[ < ] | [ > ] |  | [ << ] | [ Up ] | [ >> ] |  |  |  |  | [Top] | [Contents] | [Index] | [ ? ]

### 18.3.11 Atmel AVR

When configured for debugging the Atmel AVR, GDB supports the following AVR-specific commands:

`info io_registers`
  This command displays information about the AVR I/O registers. For each register, GDB prints its number and value.

[ < ] | [ > ] |  | [ << ] | [ Up ] | [ >> ] |  |  |  |  | [Top] | [Contents] | [Index] | [ ? ]

### 18.3.12 CRIS

When configured for debugging CRIS, GDB provides the following CRIS-specific commands:

`set cris-version ver`
  Set the current CRIS version to ver, either ``10'` or ``32'`. The CRIS version affects register names and sizes. This command is useful in case autodetection of the CRIS version fails.

`show cris-version`
  Show the current CRIS version.

`set cris-dwarf2-cfi`
  Set the usage of DWARF-2 CFI for CRIS debugging. The default is ``on'`. Change to ``off'` when using `gcc-cris` whose version is below `R59`.

`show cris-dwarf2-cfi`
  Show the current state of using DWARF-2 CFI.

`set cris-mode mode`
  Set the current CRIS mode to mode. It should only be changed when debugging in guru mode, in which case it should be set to ``guru'` (the default is ``normal'`).

`show cris-mode`
  Show the current CRIS mode.

[ < ] | [ > ] |  | [ << ] | [ Up ] | [ >> ] |  |  |  |  | [Top] | [Contents] | [Index] | [ ? ]

### 18.3.13 Renesas Super-H

For the Renesas Super-H processor, GDB provides these commands:

`regs`
  Show the values of all Super-H registers.

[ < ] | [ > ] |  | [ << ] | [ Up ] | [ >> ] |  |  |  |  | [Top] | [Contents] | [Index] | [ ? ]

## 18.4 Architectures

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

> 18.4.1 x86 Architecture-specific Issues |  |
> 18.4.2 A29K |  |
> 18.4.3 Alpha |  |
> 18.4.4 MIPS |  |
> 18.4.5 HPPA |  | HP PA architecture
> 18.4.6 Cell Broadband Engine SPU architecture |  |
> 18.4.7 PowerPC |  |

[ < ] | [ > ] |  | [ << ] | [ Up ] | [ >> ] |  |  |  |  | [Top] | [Contents] | [Index] | [ ? ]

### 18.4.1 x86 Architecture-specific Issues

`set struct-convention mode`
  Set the convention used by the inferior to return `struct`s and `union`s from functions to mode. Possible values of mode are `"pcc"`, `"reg"`, and `"default"` (the default). `"default"` or `"pcc"` means that `struct`s are returned on the stack, while `"reg"` means that a `struct` or a `union` whose size is 1, 2, 4, or 8 bytes will be returned in a register.

`show struct-convention`
  Show the current setting of the convention to return `struct`s from functions.

[ < ] | [ > ] |  | [ << ] | [ Up ] | [ >> ] |  |  |  |  | [Top] | [Contents] | [Index] | [ ? ]

### 18.4.2 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.

[ < ] | [ > ] |  | [ << ] | [ Up ] | [ >> ] |  |  |  |  | [Top] | [Contents] | [Index] | [ ? ]

### 18.4.3 Alpha

See the following section.

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### 18.4.4 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. You should only need to use this command when debugging a stripped executable.

`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.

Several MIPS-specific commands are available when debugging MIPS programs:

`set mips abi arg`
  Tell GDB which MIPS ABI is used by the inferior. Possible values of arg are:

  ``auto'`
    The default ABI associated with the current binary (this is the default).
  ``o32'`
  ``o64'`
  ``n32'`
  ``n64'`
  ``eabi32'`
  ``eabi64'`
  ``auto'`

`show mips abi`
  Show the MIPS ABI used by GDB to debug the inferior.

`set mipsfpu`
`show mipsfpu`
  See section set mipsfpu.

`set mips mask-address arg`
  This command determines whether the most-significant 32 bits of 64-bit MIPS addresses are masked off. The argument arg can be ``on'`, ``off'`, or ``auto'`. The latter is the default setting, which lets GDB determine the correct value.

`show mips mask-address`
  Show whether the upper 32 bits of MIPS addresses are masked off or not.

`set remote-mips64-transfers-32bit-regs`
  This command controls compatibility with 64-bit MIPS targets that transfer data in 32-bit quantities. If you have an old MIPS 64 target that transfers 32 bits for some registers, like SR and FSR, and 64 bits for other registers, set this option to ``on'`.

`show remote-mips64-transfers-32bit-regs`
  Show the current setting of compatibility with older MIPS 64 targets.

`set debug mips`
  This command turns on and off debugging messages for the MIPS-specific target code in GDB.

`show debug mips`
  Show the current setting of MIPS debugging messages.

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### 18.4.5 HPPA

When GDB is debugging the HP PA architecture, it provides the following special commands:

`set debug hppa`
  This command determines whether HPPA architecture-specific debugging messages are to be displayed.

`show debug hppa`
  Show whether HPPA debugging messages are displayed.

`maint print unwind address`
  This command displays the contents of the unwind table entry at the given address.

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### 18.4.6 Cell Broadband Engine SPU architecture

When GDB is debugging the Cell Broadband Engine SPU architecture, it provides the following special commands:

`info spu event`
  Display SPU event facility status. Shows current event mask and pending event status.

`info spu signal`
  Display SPU signal notification facility status. Shows pending signal-control word and signal notification mode of both signal notification channels.

`info spu mailbox`
  Display SPU mailbox facility status. Shows all pending entries, in order of processing, in each of the SPU Write Outbound, SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.

`info spu dma`
  Display MFC DMA status. Shows all pending commands in the MFC DMA queue. For each entry, opcode, tag, class IDs, effective and local store addresses and transfer size are shown.

`info spu proxydma`
  Display MFC Proxy-DMA status. Shows all pending commands in the MFC Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective and local store addresses and transfer size are shown.

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### 18.4.7 PowerPC

When GDB is debugging the PowerPC architecture, it provides a set of pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point numbers stored in the floating point registers. These values must be stored in two consecutive registers, always starting at an even register like `f0` or `f2`.

The pseudo-registers go from `$dl0` through `$dl15`, and are formed by joining the even/odd register pairs `f0` and `f1` for `$dl0`, `f2` and `f3` for `$dl1` and so on.

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