I am having hard faults in my project (STM32, FreeRTOS, lwip). I can work around it by putting delays in a thread, but I don’t want to. I am trying to understand how to debug hard faults instead by following this guide.
I am working in VScode, I do not master gdb. So I hope I can do the work from vscode/pio.
I added something that causes a hard fault:
uint illegal_instruction_execution(void) {
uint * i = (uint*)0xFFFFFFFF;
*i = 0;
return *i;
}
When I call that function from my int main() my program immediately crashes and ends up in HardFault_Handler.
From the guide:
Regardless, the hardware will always push the same core set of registers to the very top of the stack which was active prior to entering the exception. ARM Cortex-M devices have two stack pointers,
msp&psp. Upon exception entry, the active stack pointer is encoded in bit 2 of theEXC_RETURNvalue pushed to the link register. If the bit is set, thepspwas active prior to exception entry, else themspwas active.
I can see msp and psp in vscode:
- msp = 0x2001ffb0
- psp = 0x00000000
So looks like msp is the only valid one. I double checked anyway, the 2nd bit in link register is 0, thus msp is active.
So I think I learned now that the source of the error originates from the msp stack, at 0x2001ffb0.
But the last vital step in the guide I can’t seem to get right. In the guide I think he pulls out the active stack from msp. I tried to load the address in the memory section in pio and just load any amount of bytes (200 e.g.) but all I read back are zeroes. And, reading the memory doesn’t give me a stacktrace either.
Any advice how to proceed is greatly appreciated.