Debugging with GDB: Configurations

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# 21. 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.

> 21.1 Native |  |
> 21.2 Embedded Operating Systems |  |
> 21.3 Embedded Processors |  |
> 21.4 Architectures |  |

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## 21.1 Native

This section describes details specific to particular native configurations.

> 21.1.1 HP-UX |  |
> 21.1.2 BSD libkvm Interface |  | Debugging BSD kernel memory images
> 21.1.3 SVR4 Process Information |  | SVR4 process information
> 21.1.4 Features for Debugging DJGPP Programs |  | Features specific to the DJGPP port
> 21.1.5 Features for Debugging MS Windows PE Executables |  | Features specific to the Cygwin port
> 21.1.6 Commands Specific to GNU Hurd Systems |  | Features specific to GNU Hurd
> 21.1.7 Darwin |  | Features specific to Darwin

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### 21.1.1 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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### 21.1.2 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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### 21.1.3 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. This includes, as of this writing, GNU/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but not HP-UX, for example.

This command may also work on core files that were created on a system that has the ``/proc'` facility.

`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 cmdline`
  Show the original command line of the process. This command is specific to GNU/Linux.

`info proc cwd`
  Show the current working directory of the process. This command is specific to GNU/Linux.

`info proc exe`
  Show the name of executable of the process. This command is specific to GNU/Linux.

`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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### 21.1.4 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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### 21.1.5 Features for Debugging MS Windows PE Executables

GDB supports native debugging of MS Windows programs, including DLLs with and without symbolic debugging information.

MS-Windows programs that call `SetConsoleMode` to switch off the special meaning of the ``Ctrl-C'` keystroke cannot be interrupted by typing `C-c`. For this reason, GDB on MS-Windows supports `C-`BREAK`` as an alternative interrupt key sequence, which can be used to interrupt the debuggee even if it ignores `C-c`.

There are various additional Cygwin-specific commands, described in this section. Working with DLLs that have no debugging symbols is described in 21.1.5.1 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 w32 thread-information-block`
  This command displays thread specific information stored in the Thread Information Block (readable on the X86 CPU family using `$fs` selector for 32-bit programs and `$gs` for 64-bit programs).

`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`, 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.

> 21.1.5.1 Support for DLLs without Debugging Symbols |  | Support for DLLs without debugging symbols

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#### 21.1.5.1 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 18.1 Commands to Specify Files, or the `dll-symbols` command in 21.1.5 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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#### 21.1.5.2 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 16. 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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#### 21.1.5.3 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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### 21.1.6 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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### 21.1.7 Darwin

GDB provides the following commands specific to the Darwin target:

`set debug darwin num`
  When set to a non zero value, enables debugging messages specific to the Darwin support. Higher values produce more verbose output.

`show debug darwin`
  Show the current state of Darwin messages.

`set debug mach-o num`
  When set to a non zero value, enables debugging messages while GDB is reading Darwin object files. (Mach-O is the file format used on Darwin for object and executable files.) Higher values produce more verbose output. This is a command to diagnose problems internal to GDB and should not be needed in normal usage.

`show debug mach-o`
  Show the current state of Mach-O file messages.

`set mach-exceptions on`
`set mach-exceptions off`
  On Darwin, faults are first reported as a Mach exception and are then mapped to a Posix signal. Use this command to turn on trapping of Mach exceptions in the inferior. This might be sometimes useful to better understand the cause of a fault. The default is off.

`show mach-exceptions`
  Show the current state of exceptions trapping.

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## 21.2 Embedded Operating Systems

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

> 21.2.1 Using GDB with VxWorks |  |

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

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### 21.2.1 Using GDB with VxWorks

Debugging on VxWorks is supported on VxWorks 5.5, all versions of Vworks 6 starting with version 6.4, and VxWorks 653. GDB does not connect directly to the target running VxWorks, but instead relies on the Target Server, which is a process running on the host. The debugger establishes a connection with that process, and sends all debugging comands (resume task execution, read memory, read register, ...) through the Target Server.

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#### 21.2.1.1 Debugging on VxWorks 5.5

Debugging a program on VxWorks 5.5 is performed by connecting to the Target Server first. To establish this connection, use the `target wtx` command (WTX is the name of the protocol used to communicate with the Target Server):

`target wtx target-server-name`
  Connect GDB to a Target Server whose name is target-server-name. Once the connection is established, GDB queries the list of modules loaded on the target, and then proceeds to load the symbol table and debugging information from these modules.

VxWorks does not have a concept of processes, or even programs, like most Operating Systems do. Instead of running a program, one spawns a task (a.k.a. a thread), usually using a symbol name as the entry point for that thread. Every task created can be regarded as a kernel thread, since it shares memory and code with the rest of the system.

To create a new task under debugger control, use the `run` command, passing as the first parameter the name of the symbol to use as the entry point (all other parameters are ignored):

    (gdb) run simple_main
    [...]

Instead of creating a new task, it is also possible to attach the debugger to an already existing task, using the `attach` command. The equivalent of the Unix process ID is the task ID on VxWorks, and these IDs should be used to identify the task that needs to be debugged.

    (gdb) attach 0xf70b0f0
    Attaching to task 0xf70b0f0.
    [...]

As a convenience, GDB allows the use of the task name as a parameter to the `attach` command, in place of the task ID. When a task name is specified, the first task whose name matches is selected. If there are more than one tasks with the same name, the selection process is random.

A list of all tasks currently running on the target can be obtained using the `info wtx threads` command.

`info wtx threads`
  Print the list of threads currently running on the target. Each line represents a thread, and contains 2 space-separated elements. The first element is the task ID, and the second is the task name.

      (gdb) info wtx threads
      0xf710190       tShell
      0xf712430       tWdbTask
      0xf715600       tTelnetd
      [...]

GDB offers several modes for debugging VxWorks tasks:

Task Mode
  In this mode, only a single tasks is being debugged. Any other tasks, including new tasks created by the task being debugged, are simply ignored (their execution is not controlled by the debugger).

Multitasks Mode
  This is a mode specific to Ada programs where the debugger simulates the concept of debugging a process. This is useful when trying to debug an Ada program that uses the multi-tasking features of Ada.

  When debugging in this mode, all Ada tasks controlled by the Ada run-time library are under GDB control, and their execution is automatically stopped or resumed as needed. In particular, when attaching to a task, all associated tasks in the same Ada "program" are automatically stopped and put under debugger control. New tasks being spawned by the Ada "program" are also automatically taken under debugger control.

  This mode is specific to Ada programs because it, because it relies on the Ada runtime in order to extract the list of tasks currently running as part of the Ada program.

The System Mode

  In this mode, the debugger controls the entire system as one process, including part of the system such as the scheduler, interrupt handlers, etc. To enter System Mode, simply use the `attach system` command. To leave System Mode, use `detach`.

`set multi-tasks-mode [on|off]`
  If `on`, activate multi-tasks mode. The default is `off`. This setting should be properly set before using the `attach` or `run` command. As long as GDB controls the execution of one or more tasks, attempting to change this setting will result in an error.

  This setting is ignored when debugging in System Mode.

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#### 21.2.1.2 Debugging on VxWorks 653

Debugging on VxWorks 653 is very similar to debugging on VxWorks 5, and the commands available for VxWorks 5 are also generally available for VxWorks 653.

The one important distinction is the fact that VxWorks 653 provides the concept of Partitions, as defined by the ARINC 653 specification. These partitions usually have their own address space, and allow the user to make sure that tasks running in one partition cannot affect tasks running on another partition (on VxWorks AE, which is an ancestor of VxWorks 653, these partitions were called Protection Domains, or PD in short). Please refer to your VxWorks 653 manual for more information about the various types of partitions and their use.

`info partitions`
  Print the list of existing partitions on the target system. Each line corresponds to a partition, and contains its ID and name. An asterisk ``*'` at the start of one of the lines indicates the current partition.

      (gdb) info partitions
         PD-ID         Name
      *  0x356738      coreOS
         0xd799f0      ssl
         0xd7ae20      part1
         0xd80750      part2

`partition id-or-name`
  Switch to the given partition. The id-or-name argument can be either the partition ID (an hexadecimal number), or its name.

      (gdb) partition part1
      [Switching to Partition part1 (0xd7ae20)]
      (gdb) partition 0xd80750
      [Switching to Partition part2 (0xd80750)]

`maintenance info link-path`
  This is a command mostly aimed at helping GDB maintainers. It prints the link path of each partition (the Link Path is a path associated to each partition, and is used by the loader to find requested symbols - for more information, see your Tornado 653 Manuals).

      (gdb) maintenance info link-path
      Partition        Name        [Link Path]
         0x356738      coreOS      [.]
         0xd799f0      ssl         [.]
         0xd7ae20      part1       [.:ssl:ssl]
         0xd80750      part2       [.:ssl]

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#### 21.2.1.3 Commands and Settings Related to WTX

The following Settings are provided:

`set wtx tool-name name`
  This command can be used to change the name of the tool given to the Target Server when establishing the connection. This is only for documentation and logging purposes as this has no effect on the debugging session. The default is `gdb`.

`show wtx tool-name`
  Display the tool name used when establishing a connection with the WTX server.

`set wtx load-timeout timeout`
  Change the timeout (in seconds) used when loading new modules on the target. The default is 30 seconds.

`show wtx load-timeout`
  Print the timeout duration used when loading modules on the target.

`set wtx stack-size size`
  Change the stack size (in bytes) of the tasks spawned by the debugger (using the `run` command). This does not affect the stack size of a task spawned by other tasks, even if those tasks are under debugger control. The default is 0x10000 bytes.

`show wtx stack-size`
  Display the size of the stack allocated when spawning a new task from the debugger (using the `run` command).

`set wtx task-options val`
  Change the options argument used when spawning a new task from GDB. Bits in this options argument are defined in ``wpwr/target/h/taskLib.h'`. The default value is 0.

`show wtx task-options`
  Show the options argument used when spawning a new task from GDB.

`set wtx task-priority priority`
  Change the priority of new tasks spawned by the debugger. The default is 100.

`show wtx task-priority`
  Print the task priority used when spawning new tasks from the debugger.

Some commands are also available to query the Target Server about the system running on the target.

`info wtx`
`info wtx version`
  Display the version of the WTX protocol in use.

      (gdb) info wtx
      WTX protocol version 2

`info wtx vxworks-version`
  Display the version of the VxWorks system running on the target.

      (gdb) info wtx vxworks-version
      VxWorks version 5.5

`info wtx target-server`
  Display the target specifications provided by the target server.

      (gdb) info wtx target-server
      Target agent:
      version: 2.0
      max transfer size in bytes: 1372
      available agent modes: 3

      Runtime:
      name: VxWorks
      version: 5.5
      target processor type: 94
      has write protect: 0
      page size: 4096
      endianness: 1234
      BSP: Motorola MVME5110-2153 - MPC 7410
      boot file: myhost:/path/to/vxWorks
      target main memory base address: 0
      target memory size: 268435456
      number of memory regions: 0
      target server memory pool base: 0x1ff558
      target server memory pool size: 16646314

Some of the information (such as the list of tasks currently running on the system) can only be retrieved by using some of TCL procedures provided by VxWorks. A minimal TCL intepreter is therefore included in GDB.

`tcl `tcl-command``
  Use the TCL interpreter to evaluate the `tcl-command`.

Finally, the following commands may be useful to GDB maintainers wishing to instrument the part of the code in GDB responsible for supporting the WTX protocol.

`set wtx debug events level`
  If level is nonzero, print debug traces related to WTX event handling. The events being traced are all the events that wtxEventGet returns (Eg: breakpoint events, watchpoint events, new modules loaded, etc...).

`show wtx debug events`
  Print the current trace level for WTX event handling.

`set wtx debug objfiles level`
  If level is nonzero, print debug traces related to module handling for WTX (modules are stored as objfiles in GDB).

`show wtx debug objfiles`
  Print th current trace level for WTX module handling.

`set wtx debug breakpoints level`
  If level is nonzero, print debug traces related to WTX breakpoint handling.

`show wtx debug breakpoints`
  Print the current trace level for WTX breakpoint event handling.

`set wtx debug watchpoints level`
  If level is nonzero, print debug traces related to WTX watchpoint handling.

`show wtx debug watchpoints`
  Print the current trace level for WTX watchpoint event handling.

`set wtx debug tcl level`
  Set the verbosity level of error messages from the TCL interpreter.

`show wtx debug tcl`
  Show the verbosity level of error messages from the TCL interpreter.

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#### 21.2.1.4 Debugging on VxWorks 6

Debugging on VxWorks 6 follows the same principles as those for debugging VxWorks 5. The main difference is that GDB needs to connect to a DFW server in addition to the Target Server. The DFW server is another server running on the host (see your VxWorks 6 Manuals for more information about this process).

To start a debugging session, use the `target dfw` command. It will get both DFW and WTX connections established (therefore, do not use the `target wtx` command with VxWorks 6).

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#### 21.2.1.5 Commands and Settings Related to DFW

The following settings are provided:

`set dfw timeout duration`
  Change the timeout (in seconds) used when trying to read from the connection with the DFW server. The default value is 30 seconds.

`show dfw timeout`
  Show the duration in seconds before an attempt to read data from the DFW server should time out.

`set dfw server-name name`
  Set the name of the DFW server as registered in the WIND registry. By default, it is set to `dfw`; if only one DFW server is registered in the registry, GDB will connect to this server by default.

`show dfw server-name`
  Show the name of the DFW server.

The following commands may be useful to GDB maintainers wishing to instrument the part of the code in GDB responsible for supporting the DFW protocol.

`dfw send`
  Send a request to the current DFW server.

`set dfw debug requests`
`set dfw debug requests on`
  Print the requests sent to the DFW server to stdout.

`set dfw debug requests off`
  Do not print the requests sent to the DFW server to stdout.

`show dfw debug requests`
  Show whether to show the requests sent to the DFW server.

`set dfw debug responses`
`set dfw debug responses on`
  Print the responses of the DFW server to stdout.

`set dfw debug responses off`
  Do not print the responses of the DFW server to stdout.

`show dfw debug responses`
  Show whether to show the responses sent by the DFW server.

`set dfw debug unknown-identifiers`
`set dfw debug unknown-identifiers on`
  Print a warning if the DFW server returns an identifier that is not known for task types (e.g. "RTP"), task states (e.g. "running"), event kinds (e.g. "download-failed").

`set dfw debug unknown-identifiers off`
  Disable warnings about unknown task types, task states, event kinds.

`show dfw debug unknown-identifiers`
  Show whether to warn about unknown task types, task states, event kinds.

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#### 21.2.1.6 VxWorks Module Handling

Unlike most Operating Systems, the loading of modules in memory has to be performed manually by the user. Modules can be a self-contained program, or just part of a program consisting of multiple modules (this is similar to programs depending on shared libraries).

To load a new module on the target, use the `load` command. In addition to loading the module on the target, the debugger will also load its symbol table and debugging information.

Modules may also be unloaded at any time, using the `unload` command.

`wtx add-symbol-file file`
  This command is similar to the `add-symbol-file` command, except that it does not require base addresses to be provided. Instead, these addresses are automatically computed based on some information provided by the Target Server.

  This command is normally rarely needed, since GDB should automatically load the symbols from all modules either when connecting to the target, or when the module is loaded on the target. But this may become useful when the module fullpath provided by the target server does not correspond to the module's fullpath on the host where GDB is running.

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## 21.3 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.

> 21.3.1 ARM |  | ARM RDI
> 21.3.2 Renesas M32R/D and M32R/SDI |  | Renesas M32R/D
> 21.3.3 M68k |  | Motorola M68K
> 21.3.4 MicroBlaze |  | Xilinx MicroBlaze
> 21.3.5 MIPS Embedded |  | MIPS Embedded
> 21.3.6 PowerPC Embedded |  |
> 21.3.7 HP PA Embedded |  |
> 21.3.8 Tsqware Sparclet |  |
> 21.3.9 Fujitsu Sparclite |  |
> 21.3.10 Zilog Z8000 |  |
> 21.3.11 Atmel AVR |  |
> 21.3.12 CRIS |  |
> 21.3.13 Renesas Super-H |  |

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### 21.3.1 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 arm fallback-mode (arm|thumb|auto)`
  GDB uses the symbol table, when available, to determine whether instructions are ARM or Thumb. This command controls GDB's default behavior when the symbol table is not available. The default is ``auto'`, which causes GDB to use the current execution mode (from the `T` bit in the `CPSR` register).

`show arm fallback-mode`
  Show the current fallback instruction mode.

`set arm force-mode (arm|thumb|auto)`
  This command overrides use of the symbol table to determine whether instructions are ARM or Thumb. The default is ``auto'`, which causes GDB to use the symbol table and then the setting of ``set arm fallback-mode'`.

`show arm force-mode`
  Show the current forced instruction mode.

`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.

`target sim [simargs] ...`
  The GDB ARM simulator accepts the following optional arguments.

  `--swi-support=type`
    Tell the simulator which SWI interfaces to support. type may be a comma separated list of the following values. The default value is `all`.

    `none`
    `demon`
    `angel`
    `redboot`
    `all`

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### 21.3.2 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.

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### 21.3.3 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.

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### 21.3.4 MicroBlaze

The MicroBlaze is a soft-core processor supported on various Xilinx FPGAs, such as Spartan or Virtex series. Boards with these processors usually have JTAG ports which connect to a host system running the Xilinx Embedded Development Kit (EDK) or Software Development Kit (SDK). This host system is used to download the configuration bitstream to the target FPGA. The Xilinx Microprocessor Debugger (XMD) program communicates with the target board using the JTAG interface and presents a `gdbserver` interface to the board. By default `xmd` uses port `1234`. (While it is possible to change this default port, it requires the use of undocumented `xmd` commands. Contact Xilinx support if you need to do this.)

Use these GDB commands to connect to the MicroBlaze target processor.

`target remote :1234`
  Use this command to connect to the target if you are running GDB on the same system as `xmd`.

`target remote xmd-host:1234`
  Use this command to connect to the target if it is connected to `xmd` running on a different system named xmd-host.

`load`
  Use this command to download a program to the MicroBlaze target.

`set debug microblaze n`
  Enable MicroBlaze-specific debugging messages if non-zero.

`show debug microblaze n`
  Show MicroBlaze-specific debugging level.

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### 21.3.5 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-elf'`.

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 acknowledgment 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-elf'`.)

  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.

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### 21.3.6 PowerPC Embedded

GDB supports using the DVC (Data Value Compare) register to implement in hardware simple hardware watchpoint conditions of the form:

    (gdb) watch ADDRESS|VARIABLE \
      if  ADDRESS|VARIABLE == CONSTANT EXPRESSION

The DVC register will be automatically used when GDB detects such pattern in a condition expression, and the created watchpoint uses one debug register (either the `exact-watchpoints` option is on and the variable is scalar, or the variable has a length of one byte). This feature is available in native GDB running on a Linux kernel version 2.6.34 or newer.

When running on PowerPC embedded processors, GDB automatically uses ranged hardware watchpoints, unless the `exact-watchpoints` option is on, in which case watchpoints using only one debug register are created when watching variables of scalar types.

You can create an artificial array to watch an arbitrary memory region using one of the following commands (see section 10.1 Expressions):

    (gdb) watch *((char *) address)@length
    (gdb) watch {char[length]} address

PowerPC embedded processors support masked watchpoints. See the discussion about the `mask` argument in 5.1.2 Setting Watchpoints.

PowerPC embedded processors support hardware accelerated ranged breakpoints. A ranged breakpoint stops execution of the inferior whenever it executes an instruction at any address within the range it specifies. To set a ranged breakpoint in GDB, use the `break-range` command.

GDB provides the following PowerPC-specific commands:

`break-range start-location, end-location`
  Set a breakpoint for an address range. start-location and end-location can specify a function name, a line number, an offset of lines from the current line or from the start location, or an address of an instruction (see 9.2 Specifying a Location, for a list of all the possible ways to specify a location.) The breakpoint will stop execution of the inferior whenever it executes an instruction at any address within the specified range, (including start-location and end-location.)

`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.

`set powerpc exact-watchpoints`
`show powerpc exact-watchpoints`
  Allow GDB to use only one debug register when watching a variable of scalar type, thus assuming that the variable is accessed through the address of its first byte.

`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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### 21.3.7 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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### 21.3.8 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)

> 21.3.8.1 Setting File to Debug |  | Setting the file to debug
> 21.3.8.2 Connecting to Sparclet |  |
> 21.3.8.3 Sparclet Download |  | Sparclet download
> 21.3.8.4 Running and Debugging |  | Running and debugging

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#### 21.3.8.1 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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#### 21.3.8.2 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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#### 21.3.8.3 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.

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#### 21.3.8.4 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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### 21.3.9 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.

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### 21.3.10 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.

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### 21.3.11 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.

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### 21.3.12 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.

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### 21.3.13 Renesas Super-H

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

`set sh calling-convention convention`
  Set the calling-convention used when calling functions from GDB. Allowed values are ``gcc'`, which is the default setting, and ``renesas'`. With the ``gcc'` setting, functions are called using the GCC calling convention. If the DWARF-2 information of the called function specifies that the function follows the Renesas calling convention, the function is called using the Renesas calling convention. If the calling convention is set to ``renesas'`, the Renesas calling convention is always used, regardless of the DWARF-2 information. This can be used to override the default of ``gcc'` if debug information is missing, or the compiler does not emit the DWARF-2 calling convention entry for a function.

`show sh calling-convention`
  Show the current calling convention setting.

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## 21.4 Architectures

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

> 21.4.1 AArch64 |  |
> 21.4.2 x86 Architecture-specific Issues |  |
> 21.4.3 Alpha |  |
> 21.4.4 MIPS |  |
> 21.4.5 HPPA |  | HP PA architecture
> 21.4.6 Cell Broadband Engine SPU architecture |  |
> 21.4.7 PowerPC |  |
> 21.4.8 Nios II |  |

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### 21.4.1 AArch64

When GDB is debugging the AArch64 architecture, it provides the following special commands:

`set debug aarch64`
  This command determines whether AArch64 architecture-specific debugging messages are to be displayed.

`show debug aarch64`
  Show whether AArch64 debugging messages are displayed.

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### 21.4.2 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.

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#### 21.4.2.1 Intel(R) Memory Protection Extensions (MPX).

Memory Protection Extension (MPX) adds the bound registers ``BND0'` (14) through ``BND3'`. Bound registers store a pair of 64-bit values which are the lower bound and upper bound. Bounds are effective addresses or memory locations. The upper bounds are architecturally represented in 1's complement form. A bound having lower bound = 0, and upper bound = 0 (1's complement of all bits set) will allow access to the entire address space.

``BND0'` through ``BND3'` are represented in GDB as ``bnd0raw'` through ``bnd3raw'`. Pseudo registers ``bnd0'` through ``bnd3'` display the upper bound performing the complement of one operation on the upper bound value, i.e. when upper bound in ``bnd0raw'` is 0 in the GDB ``bnd0'` it will be `0xfff...`. In this sense it can also be noted that the upper bounds are inclusive.

As an example, assume that the register BND0 holds bounds for a pointer having access allowed for the range between 0x32 and 0x71. The values present on bnd0raw and bnd registers are presented as follows:

    	bnd0raw = {0x32, 0xffffffff8e}
    	bnd0 = {lbound = 0x32, ubound = 0x71} : size 64

This way the raw value can be accessed via bnd0raw...bnd3raw. Any change on bnd0...bnd3 or bnd0raw...bnd3raw is reflect on its counterpart. When the bnd0...bnd3 registers are displayed via Python, the display includes the memory size, in bits, accessible to the pointer.

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### 21.4.3 Alpha

See the following section.

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### 21.4.4 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'`

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

`set mips compression arg`
  Tell GDB which MIPS compressed ISA, Instruction Set Architecture encoding is used by the inferior. GDB uses this for code disassembly and other internal interpretation purposes. This setting is only referred to when no executable has been associated with the debugging session or the executable does not provide information about the encoding it uses. Otherwise this setting is automatically updated from information provided by the executable.

  Possible values of arg are ``mips16'` and ``micromips'`. The default compressed ISA encoding is ``mips16'`, as executables containing MIPS16 code frequently are not identified as such.

  This setting is "sticky"; that is, it retains its value across debugging sessions until reset either explicitly with this command or implicitly from an executable.

  The compiler and/or assembler typically add symbol table annotations to identify functions compiled for the MIPS16 or microMIPS ISAs. If these function-scope annotations are present, GDB uses them in preference to the global compressed ISA encoding setting.

`show mips compression`
  Show the MIPS compressed ISA encoding 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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### 21.4.5 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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### 21.4.6 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.

When GDB is debugging a combined PowerPC/SPU application on the Cell Broadband Engine, it provides in addition the following special commands:

`set spu stop-on-load arg`
  Set whether to stop for new SPE threads. When set to `on`, GDB will give control to the user when a new SPE thread enters its `main` function. The default is `off`.

`show spu stop-on-load`
  Show whether to stop for new SPE threads.

`set spu auto-flush-cache arg`
  Set whether to automatically flush the software-managed cache. When set to `on`, GDB will automatically cause the SPE software-managed cache to be flushed whenever SPE execution stops. This provides a consistent view of PowerPC memory that is accessed via the cache. If an application does not use the software-managed cache, this option has no effect.

`show spu auto-flush-cache`
  Show whether to automatically flush the software-managed cache.

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### 21.4.7 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.

For POWER7 processors, GDB provides a set of pseudo-registers, the 64-bit wide Extended Floating Point Registers (``f32'` through ``f63'`).

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### 21.4.8 Nios II

When GDB is debugging the Nios II architecture, it provides the following special commands:

`set debug nios2`
  This command turns on and off debugging messages for the Nios II target code in GDB.

`show debug nios2`
  Show the current setting of Nios II debugging messages.

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