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import os
import signal
import socket
import subprocess
import sys
import termios
import tty
import select
import ptrace.debugger
from ptrace.debugger import (
ProcessSignal,
ProcessExit,
NewProcessEvent,
)
# ----------------------------------------------------------------------
# Configuration
# ----------------------------------------------------------------------
# Scheduler timeout in seconds.
# 0 => purely non-blocking (never waits for scheduler input).
SCHED_TIMEOUT = 0.1
# ----------------------------------------------------------------------
# Scheduler logic via non-blocking UNIX socket
# ----------------------------------------------------------------------
def schedule_next_nonblocking(sock, processes, current_proc):
"""
Try to read the next TID from 'sock' within SCHED_TIMEOUT.
If valid and present in 'processes', return that PtraceProcess.
Otherwise return current_proc.
"""
# Handle timeout = 0 (purely non-blocking)
timeout = SCHED_TIMEOUT if SCHED_TIMEOUT > 0 else 0
r, _, _ = select.select([sock], [], [], timeout)
if not r:
# No scheduler input
return current_proc
data = sock.recv(64)
if not data:
return current_proc
try:
tid = int(data.strip())
except ValueError:
print(f"Scheduler sent invalid data: {data!r}")
return current_proc
if tid in processes:
print(f"Scheduler selected TID {tid}")
return processes[tid]
print(f"TID {tid} not active; ignoring")
return current_proc
# ----------------------------------------------------------------------
# First clone handling
# ----------------------------------------------------------------------
def run_until_first_clone(debugger, process):
"""
Continue execution until the first clone (new thread/process) event occurs.
"""
process.cont()
while True:
try:
sig = debugger.waitSignals()
sig.process.cont(sig.signum)
except NewProcessEvent as event:
new_proc = event.process
print(f"First clone: TID {new_proc.pid}")
return
except ProcessExit as event:
print(f"Process {event.process.pid} exited before cloning")
raise
# ----------------------------------------------------------------------
# Main Trace Function
# ----------------------------------------------------------------------
def trace(pid, sched_socket_path):
debugger = ptrace.debugger.PtraceDebugger()
debugger.traceClone()
debugger.traceFork()
debugger.traceExec()
print(f"Attach process {pid}")
proc0 = debugger.addProcess(pid, False)
# ------------------------------------------------------------------
# Create Unix scheduling socket
# ------------------------------------------------------------------
if os.path.exists(sched_socket_path):
os.unlink(sched_socket_path)
srv = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
srv.bind(sched_socket_path)
srv.listen(1)
print(f"Waiting for scheduler connection on {sched_socket_path}")
conn, _ = srv.accept()
print("Scheduler connected")
# ------------------------------------------------------------------
# 1) Run until the first clone happens
# ------------------------------------------------------------------
run_until_first_clone(debugger, proc0)
# ------------------------------------------------------------------
# 2) Attach all threads in the process
# ------------------------------------------------------------------
for tid_str in os.listdir(f"/proc/{pid}/task"):
tid = int(tid_str)
if tid not in debugger.dict:
try:
debugger.addProcess(tid, False)
except Exception as e:
print(f"Failed to attach TID {tid}: {e}")
# Choose an initial thread arbitrarily
tids = list(debugger.dict.keys())
if not tids:
print("No threads to trace")
return
proc = debugger.dict[tids[0]]
# ------------------------------------------------------------------
# 3) Main scheduling / syscall loop
# ------------------------------------------------------------------
while len(debugger.list) != 0:
# Obtain next thread to schedule (possibly the same one)
proc = schedule_next_nonblocking(conn, debugger.dict, proc)
tid = proc.pid
try:
# Continue execution until next syscall entry or exit
proc.syscall()
proc.waitSyscall()
ip = proc.getInstrPointer()
print(f"TID {tid} syscall-stop at {hex(ip)}")
except ProcessSignal as ev:
# Forward non-TRAP signals
ev.process.cont(ev.signum)
except ProcessExit as ev:
print(f"Thread {ev.process.pid} exited (exitcode={ev.exitcode})")
try:
ev.process.detach()
except Exception:
pass
debugger.deleteProcess(ev.process)
# If the thread was the current one, pick another
if proc not in debugger.list and len(debugger.list) > 0:
proc = debugger.list[0]
except Exception as e:
print(f"TID {tid} exception: {e}")
try:
proc.detach()
except Exception:
pass
debugger.deleteProcess(proc)
if len(debugger.list) > 0:
proc = debugger.list[0]
# Attach new threads created while tracing
for p in list(debugger.list):
t = p.pid
if t not in debugger.dict:
debugger.dict[t] = p
conn.close()
srv.close()
debugger.quit()
# ----------------------------------------------------------------------
# Entry point
# ----------------------------------------------------------------------
def quoted(s: str) -> str:
return f'"{s}"'
if __name__ == "__main__":
env = os.environ.copy()
qemu = [
"qemu-x86_64",
"/nix/store/dmpq06y392i752zwhcna07kb2x5l58l5-memcached-static-x86_64-unknown-linux-musl-1.6.37/bin/memcached",
"-p", "11211",
"-t", "4",
"-vv",
]
sched_path = "/tmp/memcached_scheduler.sock"
proc = subprocess.Popen(qemu, env=env)
try:
trace(proc.pid, sched_path)
except Exception as e:
print(f"Got exception: {e}")
proc.kill()
exit(2)
exit(0)
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