gdb script to emulate the trace command for logging memory reads/writes on Cortex-M targets

gdb-trace.py

import re
from collections import OrderedDict

register_names = "pc sp lr r0 r1 r2 r3 r4 r5 r6 r7 r8 r9 r10 r11 r12 xPSR".split(" ")

addr_pattern = re.compile(r";\s+\((0x[0-9a-fA-F]{1,8})\)")

def get_registers(names=register_names):
    uint32_t = gdb.lookup_type("unsigned long")
    d = OrderedDict()
    for name in names:
        value = gdb.parse_and_eval("$"+name).cast(uint32_t)
        d[name] = int(value)
    return d

def step_and_record_while(log, predicate):
    prev_registers = {}
    while True:
        registers = get_registers()
        changeset = [(reg,val) for (reg,val) in registers.items() if val != prev_registers.get(reg)]
        prev_registers = registers
        inst = gdb.execute("x /i $pc", to_string=True)
        if inst.startswith("=> "):
            inst = inst[3:]
        log.write(inst.strip())
        if ";" in inst:
            m = addr_pattern.search(inst)
            if m is not None:
                word = gdb.parse_and_eval("*(unsigned long*)({})".format(m.group(1)))
                log.write(" @#MEM=" + ("0x{:08X}".format(int(word))))
        
        if changeset:
            log.write(" @#")
            log.write(",".join("{:s}=0x{:08X}".format(reg,val) for (reg,val) in changeset) + "\n")
        if not predicate(registers):
            break
        gdb.execute("si", to_string=True)

def step_through_bootloader(log):
    def not_in_user_code(registers):
        return (registers["pc"] <= 0x08004000)
    
    step_and_record_while(log, not_in_user_code)

def step_until_before_loop(log):
    def before_loop(registers):
        if registers["pc"] == 0x8001292:
            return False
        return True
    step_and_record_while(log, before_loop)