DevGuide/GDB OpenOCD Debug
Commands can often be issued without typing the entire command. Here are some commonly used commands; many of them can be invoked using only the first letter:
(gdb) quit – exit the debugger (gdb) file – load an executable file (gdb) break line-number/function name -- Set a break-point on a line/at start of function (gdb) run <args> -- start running the program; if there are command-line arguments, put them after the run invocation (gdb) cont -- continue running, after a break (gdb) next -- Next program line (step over function calls) (gdb) step -- Step into function calls. (gdb) finish - Step out of the present function (gdb) print expression -- Show value of a variable or expression (gdb) list – List 10 lines of the program being debugged. The sixth line is the preset statement. Subsequent, consecutive entry of list will list the next 10 lines. (gdb) where – obtain a backtrace showing all function calls before the current statement (gdb) up – Move to the function that called the present function. Useful if your program crashes in a library function; use up to get to the last function call in your program (gdb) down – Reverses the action of up (gdb) delete – Removes breakpoint by number (see example following). If no number, all deleted. (gdb) kill – Terminates the program.
GDB - OpenOCD - Floss JTAG
Connecting OpenOCD to a Floss JTAG (Lisa/L in this case) an GDB to OpenOCD.
- Start openocd in a new shell since this process needs to remain running.
- STM targets
- To connect to the Lisa/L board run the command
openocd -f interface/lisa-l.cfg -f board/lisa-l.cfg
- To connect to the Lisa/M board via FLOSS-JTAG run the command:
openocd -f interface/flossjtag.cfg -f board/lisa-l.cfg
- NXP LPC targets
- To connect to the LPC based board via OLIMEX ARM-USB-OCD dongle run the command:
openocd -f interface/olimex-arm-usb-ocd.cfg -f target/lpc2148.cfg
- To connect to the LPC based board via OLIMEX ARM-USB-OCD-H dongle run the command:
openocd -f interface/olimex-arm-usb-ocd-h.cfg -f target/lpc2148.cfg
- Compiler Debug Options
- On LPC target build your ap file with debug options. See https://github.com/elemhsb/paparazzi/blob/v4.0/conf/Makefile.lpc21 .
- Start GDB with an argument of the elf file created and uploaded to the board.
- If you programmed with the ap target then the command would be along the lines of
- Replace <airframe> with the name of the airframe that has been built.
- Now connect GDB to the board
target remote localhost:3333
- Now we need to set some break points in the code.
- In this example the ap target was part of the rotorcraft and main.c contains the main program. Open rotorcraft sw/airborne/firmwares/rotorcraft/main.c and find a line at which you'd like to set a break point.
- Stop the currently running code
monitor reset halt
- Reset the code back to the start
monitor reset init
- Now we can run the program which will stop at the break point we set.
Black Magic Probe specific
- Start GDB for arm
- Open GDB with the correct binary file
- Set Black Magic Probe as Target over the serial link (see ls /dev/ttyACM*):
target extended-remote /dev/ttyACM0
- Probe via JTAG to get a list of devices:
- (for Lisa/S, use swdp_scan instead of jtag_scan)
- Attach to a device:
- Happy Debugging!
Useful GDB commands
Also look at DevGuide/GDB_OpenOCD_Debug#GDB for general GDB commands
To display some commands for BMP
example output fot STM32F4
General commands: version -- Display firmware version info help -- Display help for monitor commands jtag_scan -- Scan JTAG chain for devices swdp_scan -- Scan SW-DP for devices targets -- Display list of available targets morse -- Display morse error message connect_srst -- Configure connect under SRST: (enable|disable) ARM Cortex-M specific commands: vector_catch -- Catch exception vectors STM32F4 specific commands: erase_mass -- Erase entire flash memory option -- Manipulate option bytes
- We probably want to ignore the interrupt calls for the moment so we can step through the code as it's being called. Note that we don't always want to do this. (STM32 command only)
monitor cortex_m3 maskisr on
- A stack trace can be printed with the command
- show the variable of a variable
- Show (eXamine) the value of the 9 bytes hardware register at address 0x40005800 and show them in hex format:
- In some cases you may not be able to access some memory areas in the mcu, in that case you should try:
set mem inaccessible-by-default off
.gdbinit for BMP
The standard commands like setting the ttyACM0 port, searching for targets and attaching one can be automated. Either with a ".gdbinit" file or if your work with Eclipse, there is a box at Debug configutations/Startup.
One Example from armstrap
target extended-remote /dev/ttyACM0 mon swdp_scan attach 1 monitor vector_catch disable hard set mem inaccessible-by-default off set print pretty
Setting up .gdbinit for BMP and gdb-regview
If you use gdb just with a BMP, you can set some initialization commands in ~/.gdbinit that will run when gdb is started, improving workflow.
A very useful plug-in called gdb-regview (available on GitHub) can really speedup debugging stm32 processors by providing a pretty-printed summary of register contents.
A sample file for debugging Lisa/M 2.0 would be:
set target-async on set mem inaccessible-by-default off #for gdb-regview plugin source /path/to/gdb-regview/gdb-regview.py regview load /path/to/gdb-regview/defs/STM32F10X_CL.xml tar ext /dev/BMP_DEVICE mon version mon swdp_scan att 1
This should be saved in ~/.gdbinit.
Then, after one starts gdb as described above, you can view registers easily, for example:
(gdb) regview show ADC_CR1
Load new binary from gdb with BMP
It is also easy to rebuild and reload a program from inside gdb. Calling make from the gdb command line will call make in your current directory:
To load a new elf file into gdb after compiling elsewhere (only required when changing the name of the file):
(gdb) file file_name.elf
To upload the binary as per the currently loaded elf:
This assumes you have attached to the target already (as per the .gdbinit example just above).
To restart the program from the beginning:
and enter y.
gdb should detect that the elf has changed when loading the new binary, so if the file name has not changed, one should just be able to rebuild (make from inside gdb if appropriate) and then call load and run.