Ensure Symbols are Loaded Correctly
- It is crucial that GDB is provided with the correct symbols from your firmware project. If breakpoints are not being hit, verify that the firmware being debugged matches the binary where symbols were extracted. Rebuild your firmware using the
-g flag to ensure debugging symbols are included. Ensure that the paths to source files are accessible to GDB.
Check if Optimizations are Affecting Breakpoints
- Compiler optimizations can often inline or remove code, making it difficult to set breakpoints on certain lines or to analyze stepping behavior. Use the
-O0 optimization level during code compilation to minimize these issues:
gcc -O0 -g -o my_firmware my_firmware.c
Use Hardware Breakpoints
- Embedded systems often have limited hardware abilities, including available breakpoints. If you're facing issues with software breakpoints, switch to using hardware breakpoints. Use the
hbreak command in GDB:
hbreak main
- Note that the number of hardware breakpoints is limited by your hardware's capabilities.
Verify Target is Stopping Execution
- Embedded targets might not halt properly when a breakpoint is hit, especially in a real-time environment. Ensure that your target hardware is genuinely pausing execution by checking status with:
info threads
- Confirm that the target hasn't reset due to a watchdog timer or other interrupts by inspecting logs or the register state.
Confirm GDBServer/Probe Connectivity
- Ensure that there are no connectivity issues between GDB and the target debug server or probe (e.g., OpenOCD, J-Link). Check connection status and logs. Use the following command to provide detailed connection information:
target remote :1234
- Use the
monitor command to send probe-specific commands that might be necessary to configure breakpoints correctly.
Manually Set Breakpoints on Address
- If setting breakpoints by source line isn't working, manually set breakpoints at specific memory addresses by using:
break *0x08001234
- Disassembly (
disas) can help find the correct address locations.
Recheck the Build Process
- Ensure your build system isn't inadvertently stripping out debugging information or using incorrect build flags. Inspect your build files and logs to verify that each component of your firmware is compiled with the correct flags and paths to the symbol files.
Utilize a .gdbinit File
- Define default startup commands in a
.gdbinit file placed in your project's root. This can automate the setup of memory regions, breakpoints, or execution commands that you may forget to perform manually.
set breakpoint pending on
target remote localhost:1234
By carefully examining the above aspects, firmware developers can diagnose and resolve stepping and breakpoint issues in GDB, ensuring an efficient debugging process for embedded systems.
