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import os
import signal
import socket
import subprocess
import select
import ptrace.debugger
from ptrace.debugger import (
ProcessExit,
ProcessEvent,
ProcessSignal,
NewProcessEvent,
ProcessExecution,
)
# If scheduler does not provide input within this time (seconds),
# continue running the last chosen thread.
SCHED_TIMEOUT = 0
class Scheduler:
def __init__(self, sched_socket_path: str = '/tmp/memcached_scheduler.sock'):
self.debugger = ptrace.debugger.PtraceDebugger()
self.debugger.traceClone()
self.debugger.traceFork()
self.debugger.traceExec()
self._first_clone_ignored = False
self._ignored_tid = None
if os.path.exists(sched_socket_path):
os.unlink(sched_socket_path)
self.srv = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
self.srv.bind(sched_socket_path)
self.srv.listen(1)
print(f"Waiting for scheduler connection on {sched_socket_path}")
self.conn, _ = self.srv.accept()
print("Scheduler connected")
def _next(self, processes, current_proc):
"""
processes: dict[tid] -> PtraceProcess
current_proc: PtraceProcess or None
"""
timeout = SCHED_TIMEOUT if SCHED_TIMEOUT > 0 else 0
r, _, _ = select.select([self.conn], [], [], timeout)
if not r:
return current_proc # no input → continue with current
data = self.conn.recv(8)
if not data:
return current_proc
try:
tid = int.from_bytes(data, byteorder='little', signed=False)
except ValueError:
print(f"Scheduler: invalid data {data!r}")
return current_proc
proc = processes.get(tid)
if proc is not None:
print(f"Scheduler picked TID {tid}")
return proc
print(f"Scheduler sent inactive TID {tid}, ignoring")
return current_proc
def _handle_signal(self, event: ProcessSignal):
proc: PtraceProcess = event.process
try:
proc.syscall(event.signum)
except Exception as e:
print(f"Error arming TID {proc.pid} after signal {event.signum}: {e}")
try:
self.debugger.deleteProcess(proc)
except Exception:
pass
def _handle_clone(self, event: NewProcessEvent):
child = event.process
parent = child.parent
child_tid = child.pid
if not self._first_clone_ignored:
# FIRST clone is ignored
self._first_clone_ignored = True
self._ignored_tid = child_tid
print(f"First clone: created TID {child_tid} — IGNORING it")
# Detach ignored child so it runs untraced
try:
child.detach()
except Exception:
pass
# Remove from debugger
try:
self.debugger.deleteProcess(child)
except Exception:
pass
# Resume parent so clone() completes
try:
parent.syscall()
except Exception as e:
print(f"Error resuming parent {parent.pid} after ignored clone: {e}")
else:
# LATER clones are traced
print(f"New traced thread {child_tid} (parent {parent.pid})")
# Arm both child and parent again
try:
child.syscall()
except Exception as e:
print(f"Error arming child {child_tid}: {e}")
try:
self.debugger.deleteProcess(child)
except Exception:
pass
try:
parent.syscall()
except Exception as e:
print(f"Error arming parent {parent.pid}: {e}")
try:
self.debugger.deleteProcess(parent)
except Exception:
pass
def _handle_exit(self, event: ProcessExit):
dead_proc: PtraceProcess = event.process
tid: int = dead_proc.pid
print(f"TID {tid} exited (exitcode={event.exitcode})")
dead_proc.detach()
self.debugger.deleteProcess(dead_proc)
def _handle_syscall(self, event: ProcessExecution):
proc = event.process
tid = proc.pid
try:
ip = proc.getInstrPointer()
print(f"TID {tid} syscall-stop at {hex(ip)}")
except Exception as e:
print(f"Error reading IP for TID {tid}: {e}")
# Build fresh pid->process map from debugger.list
processes = {p.pid: p for p in self.debugger.list}
# Scheduler decides what to run next
current_proc = self._next(processes, proc)
if current_proc is None or current_proc not in self.debugger.list:
if self.is_exited():
return
current_proc = self.debugger.list[0]
# Resume chosen thread
try:
current_proc.syscall()
except Exception as e:
print(f"Error arming TID {current_proc.pid}: {e}")
try:
self.debugger.deleteProcess(current_proc)
except Exception:
pass
def is_exited(self):
return len(self.debugger.list) == 0
def schedule(self, pid: int):
print(f"Attach process {pid}")
proc0 = self.debugger.addProcess(pid, False)
# ------------------------------------------------------------------
# Initial state
# ------------------------------------------------------------------
current_proc = proc0
# Arm the first process: run until its first event/syscall
current_proc.syscall()
while not self.is_exited():
try:
event: ProcessEvent = self.debugger.waitSyscall()
except NewProcessEvent as event:
self._handle_clone(event)
continue
except ProcessSignal as event:
self._handle_signal(event)
continue
except ProcessExit as event:
self._handle_exit(event)
continue
self._handle_syscall(event)
def __del__(self):
self.conn.close()
self.srv.close()
self.debugger.quit()
# ----------------------------------------------------------------------
# Entry point
# ----------------------------------------------------------------------
def quoted(s: str) -> str:
return f'"{s}"'
if __name__ == "__main__":
env = os.environ.copy()
qemu = [
"qemu-x86_64",
"-g",
"12348",
"/nix/store/dmpq06y392i752zwhcna07kb2x5l58l5-memcached-static-x86_64-unknown-linux-musl-1.6.37/bin/memcached",
"-p",
"11211",
"-t",
"4",
"-vv"
]
proc = subprocess.Popen(qemu, env=env)
try:
scheduler = Scheduler()
scheduler.schedule(proc.pid)
except Exception as e:
print(f"Scheduling failed: {e}")
proc.kill()
raise
exit(0)
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