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#!/usr/bin/env python3
import collections
import itertools
import gdb
import gdb.printing
import gdb.types
import gdb.unwinder
import gdb.xmethod
class FiberPrinter:
"""Print a folly::fibers::Fiber"""
def __init__(self, val):
self.val = val
state = self.val["state_"]
d = gdb.types.make_enum_dict(state.type)
d = dict((v, k) for k, v in d.items())
self.state = d[int(state)]
def state_to_string(self):
if self.state == "folly::fibers::Fiber::INVALID":
return "Invalid"
if self.state == "folly::fibers::Fiber::NOT_STARTED":
return "Not started"
if self.state == "folly::fibers::Fiber::READY_TO_RUN":
return "Ready to run"
if self.state == "folly::fibers::Fiber::RUNNING":
return "Running"
if self.state == "folly::fibers::Fiber::AWAITING":
return "Awaiting"
if self.state == "folly::fibers::Fiber::AWAITING_IMMEDIATE":
return "Awaiting immediate"
if self.state == "folly::fibers::Fiber::YIELDED":
return "Yielded"
return "Unknown"
def backtrace_available(self):
return (
self.state != "folly::fibers::Fiber::INVALID"
and self.state != "folly::fibers::Fiber::NOT_STARTED"
and self.state != "folly::fibers::Fiber::RUNNING"
)
def children(self):
result = collections.OrderedDict()
result["state"] = self.state_to_string()
result["backtrace available"] = self.backtrace_available()
return result.items()
def to_string(self):
return "folly::fibers::Fiber"
def display_hint(self):
return "folly::fibers::Fiber"
class GetFiberXMethodWorker(gdb.xmethod.XMethodWorker):
def get_arg_types(self):
return gdb.lookup_type("int")
def get_result_type(self):
return gdb.lookup_type("int")
def __call__(self, *args):
fm = args[0]
index = int(args[1])
fiber = next(itertools.islice(fiber_manager_active_fibers(fm), index, None))
if fiber is None:
raise gdb.GdbError("Index out of range")
else:
return fiber
class GetFiberXMethodMatcher(gdb.xmethod.XMethodMatcher):
def __init__(self):
super(GetFiberXMethodMatcher, self).__init__("Fiber address method matcher")
self.worker = GetFiberXMethodWorker()
def match(self, class_type, method_name):
if (
class_type.name == "folly::fibers::FiberManager"
and method_name == "get_fiber"
):
return self.worker
return None
def fiber_manager_active_fibers(fm):
all_fibers = fm["allFibers_"]["data_"]["root_plus_size_"]["m_header"]
fiber_hook = all_fibers["next_"]
fiber_count = 0
while fiber_hook != all_fibers.address:
fiber = fiber_hook.cast(gdb.lookup_type("int64_t"))
fiber = fiber - gdb.parse_and_eval(
"(int64_t)&'folly::fibers::Fiber'::globalListHook_"
)
fiber = fiber.cast(
gdb.lookup_type("folly::fibers::Fiber").pointer()
).dereference()
if FiberPrinter(fiber).state != "folly::fibers::Fiber::INVALID":
yield fiber
fiber_hook = fiber_hook.dereference()["next_"]
fiber_count = fiber_count + 1
class FiberManagerPrinter:
"""Print a folly::fibers::Fiber"""
fiber_print_limit = 100
def __init__(self, fm):
self.fm = fm
def children(self):
def limit_with_dots(fibers_iterator):
num_items = 0
for fiber in fibers_iterator:
if num_items >= self.fiber_print_limit:
yield ("...", "...")
return
yield (str(fiber.address), fiber)
num_items += 1
return limit_with_dots(fiber_manager_active_fibers(self.fm))
def to_string(self):
return "folly::fibers::FiberManager"
def display_hint(self):
return "folly::fibers::FiberManager"
class FiberPrintLimitCommand(gdb.Command):
def __init__(self):
super(FiberPrintLimitCommand, self).__init__(
"fiber-print-limit", gdb.COMMAND_USER
)
def invoke(self, arg, from_tty):
if not arg:
print("New limit has to be passed to 'fiber_print_limit' command")
return
FiberManagerPrinter.fiber_print_limit = int(arg)
print(
"New fiber limit for FiberManager printer set to "
+ str(FiberManagerPrinter.fiber_print_limit)
)
class FrameId(object):
def __init__(self, sp, pc):
self.sp = sp
self.pc = pc
class FiberUnwinderFrameFilter:
instance = None
@classmethod
def set_skip_frame_sp(cls, skip_frame_sp):
if cls.instance is None:
cls.instance = FiberUnwinderFrameFilter()
cls.instance.skip_frame_sp = skip_frame_sp
def __init__(self):
self.name = "FiberUnwinderFrameFilter"
self.priority = 100
self.enabled = True
gdb.frame_filters[self.name] = self
def filter(self, frame_iter):
if not self.skip_frame_sp:
return frame_iter
return self.filter_impl(frame_iter)
def filter_impl(self, frame_iter):
for frame in frame_iter:
frame_sp = frame.inferior_frame().read_register("rsp")
if frame_sp == self.skip_frame_sp:
continue
yield frame
class FiberUnwinder(gdb.unwinder.Unwinder):
instance = None
@classmethod
def set_fiber(cls, fiber):
if cls.instance is None:
cls.instance = FiberUnwinder()
gdb.unwinder.register_unwinder(None, cls.instance)
fiber_impl = fiber["fiberImpl_"]
cls.instance.fiber_context_ptr = fiber_impl["fiberContext_"]
def __init__(self):
super(FiberUnwinder, self).__init__("Fiber unwinder")
self.fiber_context_ptr = None
def __call__(self, pending_frame):
if not self.fiber_context_ptr:
return None
orig_sp = pending_frame.read_register("rsp")
orig_pc = pending_frame.read_register("rip")
void_star_star = gdb.lookup_type("uint64_t").pointer()
ptr = self.fiber_context_ptr.cast(void_star_star)
# This code may need to be adjusted to newer versions of boost::context.
#
# The easiest way to get these offsets is to first attach to any
# program which uses folly::fibers and add a break point in
# boost::context::jump_fcontext. You then need to save information about
# frame 1 via 'info frame 1' command.
#
# After that you need to resume program until fiber switch is complete
# and expore the contents of saved fiber context via
# 'x/16gx {fiber pointer}->fiberImpl_.fiberContext_' command.
# You then need to match those to the following values you've previously
# observed in the output of 'info frame 1' command.
#
# Value found at "rbp at X" of 'info frame 1' output:
rbp = (ptr + 6).dereference()
# Value found at "rip = X" of 'info frame 1' output:
rip = (ptr + 7).dereference()
# Value found at "caller of frame at X" of 'info frame 1' output:
rsp = rbp - 96
frame_id = FrameId(rsp, orig_pc)
unwind_info = pending_frame.create_unwind_info(frame_id)
unwind_info.add_saved_register("rbp", rbp)
unwind_info.add_saved_register("rsp", rsp)
unwind_info.add_saved_register("rip", rip)
self.fiber_context_ptr = None
FiberUnwinderFrameFilter.set_skip_frame_sp(orig_sp)
return unwind_info
def fiber_activate(fiber):
fiber_type = gdb.lookup_type("folly::fibers::Fiber")
if fiber.type != fiber_type:
fiber = fiber.cast(fiber_type.pointer()).dereference()
if not FiberPrinter(fiber).backtrace_available():
return "Can not activate a non-waiting fiber."
gdb.invalidate_cached_frames()
FiberUnwinder.set_fiber(fiber)
return "Fiber 0x{:12x} activated. You can call 'bt' now.".format(int(fiber.address))
def fiber_deactivate():
FiberUnwinderFrameFilter.set_skip_frame_sp(None)
gdb.invalidate_cached_frames()
return "Fiber de-activated."
class FiberActivateCommand(gdb.Command):
def __init__(self):
super(FiberActivateCommand, self).__init__("fiber", gdb.COMMAND_USER)
def invoke(self, arg, from_tty):
if not arg:
print("folly::fibers::Fiber* has to be passed to 'fiber' command")
return
fiber_ptr = gdb.parse_and_eval(arg)
print(fiber_activate(fiber_ptr))
class FiberDeactivateCommand(gdb.Command):
def __init__(self):
super(FiberDeactivateCommand, self).__init__(
"fiber-deactivate", gdb.COMMAND_USER
)
def invoke(self, arg, from_tty):
print(fiber_deactivate())
class FiberXMethodWorker(gdb.xmethod.XMethodWorker):
def get_arg_types(self):
return None
def get_result_type(self):
return None
def __call__(self, *args):
return fiber_activate(args[0])
class FiberXMethodMatcher(gdb.xmethod.XMethodMatcher):
def __init__(self):
super(FiberXMethodMatcher, self).__init__("Fiber method matcher")
self.worker = FiberXMethodWorker()
def match(self, class_type, method_name):
if class_type.name == "folly::fibers::Fiber" and method_name == "activate":
return self.worker
return None
class Shortcut(gdb.Function):
def __init__(self, function_name, value_lambda):
super(Shortcut, self).__init__(function_name)
self.value_lambda = value_lambda
def invoke(self):
return self.value_lambda()
def get_fiber_manager_map(evb_type):
try:
# Exception thrown if unable to find type
# Probably because of missing debug symbols
global_cache_type = gdb.lookup_type(
"folly::fibers::(anonymous namespace)::GlobalCache<" + evb_type + ">"
)
except gdb.error:
raise gdb.GdbError(
"Unable to find types. "
"Please make sure debug info is available for this binary.\n"
"Have you run 'fbload debuginfo_fbpkg'?"
)
global_cache_instance_ptr_ptr = gdb.parse_and_eval(
"&'" + global_cache_type.name + "::instance()::ret'"
)
global_cache_instance_ptr = global_cache_instance_ptr_ptr.cast(
global_cache_type.pointer().pointer()
).dereference()
if global_cache_instance_ptr == 0x0:
raise gdb.GdbError("FiberManager map is empty.")
global_cache_instance = global_cache_instance_ptr.dereference()
return global_cache_instance["map_"]
def get_fiber_manager_map_evb():
return get_fiber_manager_map("folly::EventBase")
def get_fiber_manager_map_vevb():
return get_fiber_manager_map("folly::VirtualEventBase")
def build_pretty_printer():
pp = gdb.printing.RegexpCollectionPrettyPrinter("folly_fibers")
pp.add_printer("fibers::Fiber", "^folly::fibers::Fiber$", FiberPrinter)
pp.add_printer(
"fibers::FiberManager", "^folly::fibers::FiberManager$", FiberManagerPrinter
)
return pp
def load():
gdb.printing.register_pretty_printer(gdb, build_pretty_printer())
gdb.xmethod.register_xmethod_matcher(gdb, FiberXMethodMatcher())
gdb.xmethod.register_xmethod_matcher(gdb, GetFiberXMethodMatcher())
FiberPrintLimitCommand()
FiberActivateCommand()
FiberDeactivateCommand()
Shortcut("get_fiber_manager_map_evb", get_fiber_manager_map_evb)
Shortcut("get_fiber_manager_map_vevb", get_fiber_manager_map_vevb)
def info():
return "Pretty printers for folly::fibers"