.. include:: /substitutions.rst .. _debugging: ========= Debugging ========= Finding and fixing bugs is an important part of the hardware and software development process. Sometimes you also need to use debugging techniques to understand how the system works. Two tools that are helpful are debug logging and debugging using the GNU Debugger (gdb). Debug Logging ============= NuttX has a powerful system logging facility (syslog) with ``info``, ``warn``, and ``error`` levels. You can enable debugging for your build for the subsystem or feature by using the ``menuconfig`` system. The debug options are available under :menuselection:`Build Setup --> Debug Options`. You will most likely have to enable the following options: * :menuselection:`Enable Debug Features` — selecting this will turn on subsystem-level debugging options, they will become visible on the page below. You can then select the ones you want. * :menuselection:`Enable Error Output` — this will only log errors. * :menuselection:`Enable Warnings Output` — this will log warnings and errors. * :menuselection:`Enable Informational Debug Output` — this will produce informational output, warnings, and errors. You can then select from the subsystems that are available, Network, Scheduler, USB, etc. Note that you will need to separately enable the subsystem elsewhere in the ``menuconfig`` system. To see the ``CONFIG`` define that is set, use the arrow keys to highlight the subsystem (for instance, :menuselection:`Network Debug Features`) and type :kbd:`?`. This will show you that the C macro that is set is called ``CONFIG_DEBUG_NET``. ``debug.h`` defines the ``netinfo()`` logging function that will log output if this macro is set. You can search the source code for ``netinfo`` to see how it is used. .. image:: ../_static/images/menuconfig-debug.png :width: 800px :align: center :alt: Screenshot of menuconfig system main screen Note that enabling all these will produce an incredible amount of logging output. Enable the level you want and the area you're interested in, and leave the rest disabled, save the config, and then recompile. You can see the full list of debug feature logging functions in the file `debug.h `__. Syslog timestamps can be enabled in the configuration in :menuselection:`Device Drivers --> System Logging --> Prepend timestamp to syslog message` (``CONFIG_SYSLOG_TIMESTAMP``). You may need to do a little bit of experimenting to find the combination of logging settings that work for the problem you're trying to solve. See the file `debug.h `_ for available debug settings that are available. There are also subsystems that enable USB trace debugging, and you can log to memory too, if you need the logging to be faster than what the console can output. Debugging with ``openocd`` and ``gdb`` ====================================== To debug our Nucleo board using its embedded SWD debug adapter, start ``openocd`` with the following command: .. code-block:: console $ openocd -f interface/stlink-v2.cfg -f target/stm32f1x.cfg This will start a ``gdb`` server. Then, start ``gdb`` with: .. code-block:: console $ cd nuttx/ $ gdb-multiarch nuttx/nuttx Inside ``gdb`` console, connect to the ``gdb`` server with: .. code-block:: (gdb) target extended-remote :3333 You can now use standard ``gdb`` commands. For example, to reset the board: .. code-block:: (gdb) mon reset To halt the board: .. code-block:: (gdb) mon halt To set a breakpoint: .. code-block:: (gdb) breakpoint nsh_main and to finally start nuttx: .. code-block:: (gdb) continue Continuing. Breakpoint 1, nsh_main (argc=1, argv=0x200ddfac) at nsh_main.c:208 208 sched_getparam(0, ¶m); (gdb) continue Continuing. .. tip:: You can abbreviate ``gdb`` commands: ``info b`` is a shortcut for ``information breakpoints``; ``c`` works the same as ``continue``, etc. NuttX aware debugging --------------------- Since NuttX is actually an RTOS, it is useful to have ``gdb`` be aware of the different tasks/threads that are running. There are two ways to do this: via ``openocd`` itself or via ``gdb``. Note that in both cases, you need to enable debug symbols (``CONFIG_DEBUG_SYMBOLS``). With openocd ~~~~~~~~~~~~ ``openocd`` supports various RTOS directly, including NuttX. It works by reading into internal NuttX symbols which define the active tasks and their properties. As a result, the ``gdb`` server will directly be aware of each task as a different `thread`. The downside of this approach is that it depends on how you build NuttX as there are some options hardcoded into opencd. By default, it assumes: * ``CONFIG_DISABLE_MQUEUE=y`` * ``CONFIG_LEGACY_PAGING=n`` If you need these options to be set differently, you will have to edit ``./src/rtos/nuttx_header.h`` from ``openocd``, change the corresponding settings and then rebuild it. Finally, to enable NuttX integration, you need to supply an additional ``openocd`` argument: .. code-block:: console $ openocd -f interface/stlink-v2.cfg -f target/stm32f1x.cfg -c '$_TARGETNAME configure -rtos nuttx' Since ``openocd`` also needs to know the memory layout of certain datastructures, you need to have ``gdb`` run the following commands once the ``nuttx`` binary is loaded: .. code-block:: eval "monitor nuttx.pid_offset %d", &((struct tcb_s *)(0))->pid eval "monitor nuttx.xcpreg_offset %d", &((struct tcb_s *)(0))->xcp.regs eval "monitor nuttx.state_offset %d", &((struct tcb_s *)(0))->task_state eval "monitor nuttx.name_offset %d", &((struct tcb_s *)(0))->name eval "monitor nuttx.name_size %d", sizeof(((struct tcb_s *)(0))->name) One way to do this is to define a gdb `hook` function that will be called when running ``file`` command: .. code-block:: define hookpost-file eval "monitor nuttx.pid_offset %d", &((struct tcb_s *)(0))->pid eval "monitor nuttx.xcpreg_offset %d", &((struct tcb_s *)(0))->xcp.regs eval "monitor nuttx.state_offset %d", &((struct tcb_s *)(0))->task_state eval "monitor nuttx.name_offset %d", &((struct tcb_s *)(0))->name eval "monitor nuttx.name_size %d", sizeof(((struct tcb_s *)(0))->name) end You will see that ``openocd`` has received the memory offsets in its output: .. code-block:: Open On-Chip Debugger 0.10.0+dev-01514-ga8edbd020-dirty (2020-11-20-14:23) Licensed under GNU GPL v2 For bug reports, read http://openocd.org/doc/doxygen/bugs.html Info : auto-selecting first available session transport "swd". To override use 'transport select '. Info : target type name = cortex_m Info : Listening on port 6666 for tcl connections Info : Listening on port 4444 for telnet connections 15:41:23: Debugging starts Info : CMSIS-DAP: SWD Supported Info : CMSIS-DAP: FW Version = 1.10 Info : CMSIS-DAP: Interface Initialised (SWD) Info : SWCLK/TCK = 1 SWDIO/TMS = 1 TDI = 0 TDO = 0 nTRST = 0 nRESET = 1 Info : CMSIS-DAP: Interface ready Info : clock speed 1000 kHz Info : SWD DPIDR 0x2ba01477 Info : nrf52.cpu: hardware has 6 breakpoints, 4 watchpoints Info : starting gdb server for nrf52.cpu on 3333 Info : Listening on port 3333 for gdb connections Info : accepting 'gdb' connection on tcp/3333 Error: No symbols for NuttX Info : nRF52832-QFAA(build code: B0) 512kB Flash, 64kB RAM undefined debug reason 8 - target needs reset Warn : Prefer GDB command "target extended-remote 3333" instead of "target remote 3333" Info : pid_offset: 12 Info : xcpreg_offset: 132 Info : state_offset: 26 Info : name_offset: 208 Info : name_size: 32 target halted due to debug-request, current mode: Thread xPSR: 0x01000000 pc: 0x000000dc msp: 0x20000cf0 target halted due to debug-request, current mode: Thread xPSR: 0x01000000 pc: 0x000000dc msp: 0x20000cf0 .. note:: You will probably see the ``Error: No symbols for NuttX`` error appear once at startup. This is OK unless you see it every time you step the debugger. In this case, it would mean you did not enable debug symbols. Now, You can now inspect threads: .. code-block:: (gdb) info threads Id Target Id Frame * 1 Remote target nx_start_application () at init/nx_bringup.c:261 (gdb) info registers r0 0x0 0 r1 0x2f 47 r2 0x0 0 r3 0x0 0 r4 0x0 0 r5 0x0 0 r6 0x0 0 r7 0x20000ca0 536874144 r8 0x0 0 r9 0x0 0 r10 0x0 0 r11 0x0 0 r12 0x9 9 sp 0x20000c98 0x20000c98 lr 0x19c5 6597 pc 0x1996 0x1996 xPSR 0x41000000 1090519040 fpscr 0x0 0 msp 0x20000c98 0x20000c98 psp 0x0 0x0 <_vectors> primask 0x0 0 basepri 0xe0 -32 faultmask 0x0 0 control 0x0 0 With gdb ~~~~~~~~ You can also do NuttX aware debugging using ``gdb`` scripting support. The benefit is that it works also for the sim build where ``openocd`` is not applicable. For this to work, you will need to enable PROC filesystem support which will expose required task information (``CONFIG_FS_PROCFS=y``). To use this approach, you can load the ``nuttx/tools/gdb/__init__.py`` file. An easy way to do this is to add an extra command: .. code-block:: console $ gdb nuttx -ix=tools/gdb/__init__.py gdb can need to set the current elf support architecture, for example, the prefix is arm-ebai-none-. .. code-block:: (gdb) info threads Id Thread Info Frame *0 Thread 0x20000398 (Name: Idle Task, State: Running, Priority: 0, Stack: 1000) 0x80001ac __start() at chip/stm32_start.c:111 1 Thread 0x10000188 (Name: nsh_main, State: Waiting,Semaphore, Priority: 100, Stack: 2000) 0x800aa06 sys_call2() at /home/ajh/work/vela_all/nuttx/include/arch/syscall.h:187 The python script has extended many commands like ``thread `` , ``thread apply cmd``, ``nxsetargs`` etc. You can use ``help `` to get help. Note that if you need to continue debugging after using the thread command, please use ``c`` instead of ``continue``, because thread will force the register to be set, and the `c` command will restore the register before conitune.