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@kouloumos
Created May 17, 2023 08:23
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Custom gdb command to waitfor and attach on a process
'''
To make this file available to your gdb process:
2. (gdb) source attach_helper.py
To use the custom command:
1. `attach_bitcoind` to make the debugger wait for a bitcoind process to attach on
2. Start bitcoind (e.g a functional test from another terminal)
3. Debug
'''
import gdb
import subprocess
import time
always_attach_to_the_first_process = True
def waitfor(process, target_process_index=None):
'''Helper method that waits for a process to start and returns its PID'''
print("Waiting for %s to start..." % process)
while True:
try:
output = subprocess.Popen('pgrep %s' % process, stdout=subprocess.PIPE, shell=True, text=True).communicate()[0]
if output != '':
# parse the output into a list of PIDs
pid = output.rstrip().split("\n")
if not always_attach_to_the_first_process and target_process_index is None and len(pid) > 1:
raise TypeError(
"More than one bitcoind processes are running, you might be running a functional test with multiple nodes.\
\nYou need to specify which bitcoind process you are targeting with:\
\n gdb command: attach_bitcoind <target_process_index>")
# always attach to the first bitcoind process
target_process_index = target_process_index or 0
print(f"{process} started with pid={pid}")
print(f"Ready to attach to bitcoind process with pid={pid[target_process_index]}")
# return the pid of the process that we want to attach to
return pid[target_process_index]
except gdb.error:
pass
except TypeError as e:
print(f"Error: {e}")
raise SystemExit(1) # stop the program when the TypeError occurs
time.sleep(0.1)
class AttachBitcoind(gdb.Command):
def __init__(self):
super(AttachBitcoind, self).__init__("attach_bitcoind", gdb.COMMAND_DATA)
def invoke(self, arg, from_tty):
process_index = int(arg.rstrip().split(" ")[0]) if arg.rstrip().split(" ")[0] else None
pid = waitfor("bitcoind", process_index)
gdb.execute('attach %s' % pid)
print(f'Attached to pid={pid}, process is now paused.')
# This runs on initialization when `(gdb) source extend_gdb`
print(f"Running GDB from: {gdb.PYTHONDIR}")
gdb.execute("set pagination off")
print(f"""
To make the debugger wait for a bitcoind process to attach on:
(gdb) attach_bitcoind
Then, start bitcoind (e.g a functional test from another terminal)
For more details read the source file.""")
# This registers our custom gdb commands classes to the gdb runtime at "source" time.
AttachBitcoind()
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