gdb.md

GDB commands related to embedded devices

The document contains gdb command useful when debugging embedded programs.

Commands like resetting and flashing a device can be done from gdb using the monitor command to send commands to openocd. One way to work with this is to have gdb connected to openocd and place gdb in the background (CTRL+Z) to recompile, and the use fg to bring gdb to the forground again. Then reset halt and flash the device.

$ arm-none-eabi-gdb spi.elf
(gdb) target remote localhost:3333

Halt the program:

(gdb) monitor reset halt

Run the program:

(gdb) monitor reset run

Flash the device:

(gdb) monitor flash write_image erase spi.elf.hex

(gdb) monitor flash list
{name stm32f1x base 134217728 size 131072 bus_width 0 chip_width 0}

(gdb) monitor flash banks
#0 : stm32f0x.flash (stm32f1x) at 0x08000000, size 0x00020000, buswidth 0, chipwidth 0

Get the current state for the device:

(gdb) monitor stm32f0x.cpu curstate
halted

Load/reload a program

This is useful when debugging and you want to restart the debugging session.

(gdb) load 
Loading section .text, size 0x1d8 lma 0x8000000
Start address 0x08000008, load size 472
Transfer rate: 1 KB/sec, 472 bytes/write.

Enable inaccessible memory

If memory is outside of the memory map this command is useful to be able to read/write this memory (this can happen if one want to inspect the registers related to SysTick for example):

(gdb) set mem inaccessible-by-default off