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Diffstat (limited to 'js/src/gdb/mozilla/unwind.py')
| -rw-r--r-- | js/src/gdb/mozilla/unwind.py | 596 |
1 files changed, 596 insertions, 0 deletions
diff --git a/js/src/gdb/mozilla/unwind.py b/js/src/gdb/mozilla/unwind.py new file mode 100644 index 0000000000..8dd0ec8311 --- /dev/null +++ b/js/src/gdb/mozilla/unwind.py @@ -0,0 +1,596 @@ +# This Source Code Form is subject to the terms of the Mozilla Public +# License, v. 2.0. If a copy of the MPL was not distributed with this file, +# You can obtain one at http://mozilla.org/MPL/2.0/. + +# mozilla/unwind.py --- unwinder and frame filter for SpiderMonkey + +import gdb +import gdb.types +from gdb.FrameDecorator import FrameDecorator +import platform + +# For ease of use in Python 2, we use "long" instead of "int" +# everywhere. +try: + long +except NameError: + long = int + +# The Python 3 |map| built-in works lazily, but in Python 2 we need +# itertools.imap to get this. +try: + from itertools import imap +except ImportError: + imap = map + +_have_unwinder = True +try: + from gdb.unwinder import Unwinder +except ImportError: + _have_unwinder = False + # We need something here; it doesn't matter what as no unwinder + # will ever be instantiated. + Unwinder = object + + +def debug(something): + # print("@@ " + something) + pass + + +# Maps frametype enum base names to corresponding class. +SizeOfFramePrefix = { + "FrameType::IonJS": "ExitFrameLayout", + "FrameType::BaselineJS": "JitFrameLayout", + "FrameType::BaselineStub": "BaselineStubFrameLayout", + "FrameType::IonStub": "JitStubFrameLayout", + "FrameType::CppToJSJit": "JitFrameLayout", + "FrameType::WasmToJSJit": "JitFrameLayout", + "FrameType::JSJitToWasm": "JitFrameLayout", + "FrameType::Rectifier": "RectifierFrameLayout", + "FrameType::IonAccessorIC": "IonAccessorICFrameLayout", + "FrameType::IonICCall": "IonICCallFrameLayout", + "FrameType::Exit": "ExitFrameLayout", + "FrameType::Bailout": "JitFrameLayout", +} + + +# We cannot have semi-colon as identifier names, so use a colon instead, +# and forward the name resolution to the type cache class. +class UnwinderTypeCacheFrameType(object): + def __init__(self, tc): + self.tc = tc + + def __getattr__(self, name): + return self.tc.__getattr__("FrameType::" + name) + + +class UnwinderTypeCache(object): + # All types and symbols that we need are attached to an object that we + # can dispose of as needed. + + def __init__(self): + self.d = None + self.frame_enum_names = {} + self.frame_class_types = {} + + # We take this bizarre approach to defer trying to look up any + # symbols until absolutely needed. Without this, the loading + # approach taken by the gdb-tests would cause spurious exceptions. + def __getattr__(self, name): + if self.d is None: + self.initialize() + if name == "frame_type": + return UnwinderTypeCacheFrameType(self) + return self.d[name] + + def value(self, name): + return long(gdb.lookup_symbol(name)[0].value()) + + def jit_value(self, name): + return self.value("js::jit::" + name) + + def initialize(self): + self.d = {} + self.d["FRAMETYPE_MASK"] = (1 << self.jit_value("FRAMETYPE_BITS")) - 1 + self.d["FRAMESIZE_SHIFT"] = self.jit_value("FRAMESIZE_SHIFT") + self.d["FRAME_HEADER_SIZE_SHIFT"] = self.jit_value("FRAME_HEADER_SIZE_SHIFT") + self.d["FRAME_HEADER_SIZE_MASK"] = self.jit_value("FRAME_HEADER_SIZE_MASK") + + self.compute_frame_info() + commonFrameLayout = gdb.lookup_type("js::jit::CommonFrameLayout") + self.d["typeCommonFrameLayout"] = commonFrameLayout + self.d["typeCommonFrameLayoutPointer"] = commonFrameLayout.pointer() + self.d["per_tls_context"] = gdb.lookup_global_symbol("js::TlsContext") + + self.d["void_starstar"] = gdb.lookup_type("void").pointer().pointer() + + jitframe = gdb.lookup_type("js::jit::JitFrameLayout") + self.d["jitFrameLayoutPointer"] = jitframe.pointer() + + self.d["CalleeToken_Function"] = self.jit_value("CalleeToken_Function") + self.d["CalleeToken_FunctionConstructing"] = self.jit_value( + "CalleeToken_FunctionConstructing" + ) + self.d["CalleeToken_Script"] = self.jit_value("CalleeToken_Script") + self.d["JSFunction"] = gdb.lookup_type("JSFunction").pointer() + self.d["JSScript"] = gdb.lookup_type("JSScript").pointer() + self.d["Value"] = gdb.lookup_type("JS::Value") + + self.d["SOURCE_SLOT"] = self.value("js::ScriptSourceObject::SOURCE_SLOT") + self.d["NativeObject"] = gdb.lookup_type("js::NativeObject").pointer() + self.d["HeapSlot"] = gdb.lookup_type("js::HeapSlot").pointer() + self.d["ScriptSource"] = gdb.lookup_type("js::ScriptSource").pointer() + + # ProcessExecutableMemory, used to identify if a pc is in the section + # pre-allocated by the JIT. + self.d["MaxCodeBytesPerProcess"] = self.jit_value("MaxCodeBytesPerProcess") + self.d["execMemory"] = gdb.lookup_symbol("::execMemory")[0].value() + + # Compute maps related to jit frames. + def compute_frame_info(self): + t = gdb.lookup_type("enum js::jit::FrameType") + for field in t.fields(): + # Strip off "js::jit::", remains: "FrameType::*". + name = field.name[9:] + enumval = long(field.enumval) + self.d[name] = enumval + self.frame_enum_names[enumval] = name + class_type = gdb.lookup_type("js::jit::" + SizeOfFramePrefix[name]) + self.frame_class_types[enumval] = class_type.pointer() + + +class FrameSymbol(object): + "A symbol/value pair as expected from gdb frame decorators." + + def __init__(self, sym, val): + self.sym = sym + self.val = val + + def symbol(self): + return self.sym + + def value(self): + return self.val + + +class JitFrameDecorator(FrameDecorator): + """This represents a single JIT frame for the purposes of display. + That is, the frame filter creates instances of this when it sees a + JIT frame in the stack.""" + + def __init__(self, base, info, cache): + super(JitFrameDecorator, self).__init__(base) + self.info = info + self.cache = cache + + def _decode_jitframe(self, this_frame): + calleetoken = long(this_frame["calleeToken_"]) + tag = calleetoken & 3 + calleetoken = calleetoken ^ tag + function = None + script = None + if ( + tag == self.cache.CalleeToken_Function + or tag == self.cache.CalleeToken_FunctionConstructing + ): + fptr = gdb.Value(calleetoken).cast(self.cache.JSFunction) + try: + atom = fptr["atom_"] + if atom: + function = str(atom) + except gdb.MemoryError: + function = "(could not read function name)" + script = fptr["u"]["scripted"]["s"]["script_"] + elif tag == self.cache.CalleeToken_Script: + script = gdb.Value(calleetoken).cast(self.cache.JSScript) + return {"function": function, "script": script} + + def function(self): + if self.info["name"] is None: + return FrameDecorator.function(self) + name = self.info["name"] + result = "<<" + name + # If we have a frame, we can extract the callee information + # from it for display here. + this_frame = self.info["this_frame"] + if this_frame is not None: + if gdb.types.has_field(this_frame.type.target(), "calleeToken_"): + function = self._decode_jitframe(this_frame)["function"] + if function is not None: + result = result + " " + function + return result + ">>" + + def filename(self): + this_frame = self.info["this_frame"] + if this_frame is not None: + if gdb.types.has_field(this_frame.type.target(), "calleeToken_"): + script = self._decode_jitframe(this_frame)["script"] + if script is not None: + obj = script["sourceObject_"]["value"] + # Verify that this is a ScriptSource object. + # FIXME should also deal with wrappers here. + nativeobj = obj.cast(self.cache.NativeObject) + # See bug 987069 and despair. At least this + # approach won't give exceptions. + class_name = nativeobj["group_"]["value"]["clasp_"]["name"].string( + "ISO-8859-1" + ) + if class_name != "ScriptSource": + return FrameDecorator.filename(self) + scriptsourceobj = (nativeobj + 1).cast(self.cache.HeapSlot)[ + self.cache.SOURCE_SLOT + ] + scriptsource = scriptsourceobj["value"]["asBits_"] << 1 + scriptsource = scriptsource.cast(self.cache.ScriptSource) + return scriptsource["filename_"]["mTuple"]["mFirstA"].string() + return FrameDecorator.filename(self) + + def frame_args(self): + this_frame = self.info["this_frame"] + if this_frame is None: + return FrameDecorator.frame_args(self) + if not gdb.types.has_field(this_frame.type.target(), "numActualArgs_"): + return FrameDecorator.frame_args(self) + # See if this is a function call. + if self._decode_jitframe(this_frame)["function"] is None: + return FrameDecorator.frame_args(self) + # Construct and return an iterable of all the arguments. + result = [] + num_args = long(this_frame["numActualArgs_"]) + # Sometimes we see very large values here, so truncate it to + # bypass the damage. + if num_args > 10: + num_args = 10 + args_ptr = (this_frame + 1).cast(self.cache.Value.pointer()) + for i in range(num_args + 1): + # Synthesize names, since there doesn't seem to be + # anything better to do. + if i == 0: + name = "this" + else: + name = "arg%d" % i + result.append(FrameSymbol(name, args_ptr[i])) + return result + + +class SpiderMonkeyFrameFilter(object): + "A frame filter for SpiderMonkey." + + # |state_holder| is either None, or an instance of + # SpiderMonkeyUnwinder. If the latter, then this class will + # reference the |unwinder_state| attribute to find the current + # unwinder state. + def __init__(self, cache, state_holder): + self.name = "SpiderMonkey" + self.enabled = True + self.priority = 100 + self.state_holder = state_holder + self.cache = cache + + def maybe_wrap_frame(self, frame): + if self.state_holder is None or self.state_holder.unwinder_state is None: + return frame + base = frame.inferior_frame() + info = self.state_holder.unwinder_state.get_frame(base) + if info is None: + return frame + return JitFrameDecorator(frame, info, self.cache) + + def filter(self, frame_iter): + return imap(self.maybe_wrap_frame, frame_iter) + + +class SpiderMonkeyFrameId(object): + "A frame id class, as specified by the gdb unwinder API." + + def __init__(self, sp, pc): + self.sp = sp + self.pc = pc + + +class UnwinderState(object): + """This holds all the state needed during a given unwind. Each time a + new unwind is done, a new instance of this class is created. It + keeps track of all the state needed to unwind JIT frames. Note that + this class is not directly instantiated. + + This is a base class, and must be specialized for each target + architecture, both because we need to use arch-specific register + names, and because entry frame unwinding is arch-specific. + See https://sourceware.org/bugzilla/show_bug.cgi?id=19286 for info + about the register name issue. + + Each subclass must define SP_REGISTER, PC_REGISTER, and + SENTINEL_REGISTER (see x64UnwinderState for info); and implement + unwind_entry_frame_registers.""" + + def __init__(self, typecache): + self.next_sp = None + self.next_type = None + self.activation = None + # An unwinder instance is specific to a thread. Record the + # selected thread for later verification. + self.thread = gdb.selected_thread() + self.frame_map = {} + self.typecache = typecache + + # If the given gdb.Frame was created by this unwinder, return the + # corresponding informational dictionary for the frame. + # Otherwise, return None. This is used by the frame filter to + # display extra information about the frame. + def get_frame(self, frame): + sp = long(frame.read_register(self.SP_REGISTER)) + if sp in self.frame_map: + return self.frame_map[sp] + return None + + # Add information about a frame to the frame map. This map is + # queried by |self.get_frame|. |sp| is the frame's stack pointer, + # and |name| the frame's type as a string, e.g. "FrameType::Exit". + def add_frame(self, sp, name=None, this_frame=None): + self.frame_map[long(sp)] = {"name": name, "this_frame": this_frame} + + # See whether |pc| is claimed by the Jit. + def is_jit_address(self, pc): + execMem = self.typecache.execMemory + base = long(execMem["base_"]) + length = self.typecache.MaxCodeBytesPerProcess + + # If the base pointer is null, then no memory got allocated yet. + if long(base) == 0: + return False + + # If allocated, then we allocated MaxCodeBytesPerProcess. + return base <= pc and pc < base + length + + # Check whether |self| is valid for the selected thread. + def check(self): + return gdb.selected_thread() is self.thread + + # Essentially js::TlsContext.get(). + def get_tls_context(self): + return self.typecache.per_tls_context.value()["mValue"] + + # |common| is a pointer to a CommonFrameLayout object. Return a + # tuple (local_size, header_size, frame_type), where |size| is the + # integer size of the previous frame's locals; |header_size| is + # the size of this frame's header; and |frame_type| is an integer + # representing the previous frame's type. + def unpack_descriptor(self, common): + value = long(common["descriptor_"]) + local_size = value >> self.typecache.FRAMESIZE_SHIFT + header_size = ( + value >> self.typecache.FRAME_HEADER_SIZE_SHIFT + ) & self.typecache.FRAME_HEADER_SIZE_MASK + header_size = header_size * self.typecache.void_starstar.sizeof + frame_type = long(value & self.typecache.FRAMETYPE_MASK) + if frame_type == self.typecache.frame_type.CppToJSJit: + # Trampoline-x64.cpp pushes a JitFrameLayout object, but + # the stack pointer is actually adjusted as if a + # CommonFrameLayout object was pushed. + header_size = self.typecache.typeCommonFrameLayout.sizeof + return (local_size, header_size, frame_type) + + # Create a new frame for gdb. This makes a new unwind info object + # and fills it in, then returns it. It also registers any + # pertinent information with the frame filter for later display. + # + # |pc| is the PC from the pending frame + # |sp| is the stack pointer to use + # |frame| points to the CommonFrameLayout object + # |frame_type| is a integer, one of the |enum FrameType| values, + # describing the current frame. + # |pending_frame| is the pending frame (see the gdb unwinder + # documentation). + def create_frame(self, pc, sp, frame, frame_type, pending_frame): + # Make a frame_id that claims that |frame| is sort of like a + # frame pointer for this frame. + frame_id = SpiderMonkeyFrameId(frame, pc) + + # Read the frame layout object to find the next such object. + # This lets us unwind the necessary registers for the next + # frame, and also update our internal state to match. + common = frame.cast(self.typecache.typeCommonFrameLayoutPointer) + next_pc = common["returnAddress_"] + (local_size, header_size, next_type) = self.unpack_descriptor(common) + next_sp = frame + header_size + local_size + + # Compute the type of the next oldest frame's descriptor. + this_class_type = self.typecache.frame_class_types[frame_type] + this_frame = frame.cast(this_class_type) + + # Register this frame so the frame filter can find it. This + # is registered using SP because we don't have any other good + # approach -- you can't get the frame id from a gdb.Frame. + # https://sourceware.org/bugzilla/show_bug.cgi?id=19800 + frame_name = self.typecache.frame_enum_names[frame_type] + self.add_frame(sp, name=frame_name, this_frame=this_frame) + + # Update internal state for the next unwind. + self.next_sp = next_sp + self.next_type = next_type + + unwind_info = pending_frame.create_unwind_info(frame_id) + unwind_info.add_saved_register(self.PC_REGISTER, next_pc) + unwind_info.add_saved_register(self.SP_REGISTER, next_sp) + # FIXME it would be great to unwind any other registers here. + return unwind_info + + # Unwind an "ordinary" JIT frame. This is used for JIT frames + # other than enter and exit frames. Returns the newly-created + # unwind info for gdb. + def unwind_ordinary(self, pc, pending_frame): + return self.create_frame( + pc, self.next_sp, self.next_sp, self.next_type, pending_frame + ) + + # Unwind an exit frame. Returns None if this cannot be done; + # otherwise returns the newly-created unwind info for gdb. + def unwind_exit_frame(self, pc, pending_frame): + if self.activation == 0: + # Reached the end of the list. + return None + elif self.activation is None: + cx = self.get_tls_context() + self.activation = cx["jitActivation"]["value"] + else: + self.activation = self.activation["prevJitActivation_"] + + packedExitFP = self.activation["packedExitFP_"] + if packedExitFP == 0: + return None + + exit_sp = pending_frame.read_register(self.SP_REGISTER) + frame_type = self.typecache.frame_type.Exit + return self.create_frame(pc, exit_sp, packedExitFP, frame_type, pending_frame) + + # A wrapper for unwind_entry_frame_registers that handles + # architecture-independent boilerplate. + def unwind_entry_frame(self, pc, pending_frame): + sp = self.next_sp + # Notify the frame filter. + self.add_frame(sp, name="FrameType::CppToJSJit") + # Make an unwind_info for the per-architecture code to fill in. + frame_id = SpiderMonkeyFrameId(sp, pc) + unwind_info = pending_frame.create_unwind_info(frame_id) + self.unwind_entry_frame_registers(sp, unwind_info) + self.next_sp = None + self.next_type = None + return unwind_info + + # The main entry point that is called to try to unwind a JIT frame + # of any type. Returns None if this cannot be done; otherwise + # returns the newly-created unwind info for gdb. + def unwind(self, pending_frame): + pc = pending_frame.read_register(self.PC_REGISTER) + + # If the jit does not claim this address, bail. GDB defers to our + # unwinder by default, but we don't really want that kind of power. + if not self.is_jit_address(long(pc)): + return None + + if self.next_sp is not None: + if self.next_type == self.typecache.frame_type.CppToJSJit: + return self.unwind_entry_frame(pc, pending_frame) + return self.unwind_ordinary(pc, pending_frame) + # Maybe we've found an exit frame. FIXME I currently don't + # know how to identify these precisely, so we'll just hope for + # the time being. + return self.unwind_exit_frame(pc, pending_frame) + + +class x64UnwinderState(UnwinderState): + "The UnwinderState subclass for x86-64." + + SP_REGISTER = "rsp" + PC_REGISTER = "rip" + + # A register unique to this architecture, that is also likely to + # have been saved in any frame. The best thing to use here is + # some arch-specific name for PC or SP. + SENTINEL_REGISTER = "rip" + + # Must be in sync with Trampoline-x64.cpp:generateEnterJIT. Note + # that rip isn't pushed there explicitly, but rather by the + # previous function's call. + PUSHED_REGS = ["r15", "r14", "r13", "r12", "rbx", "rbp", "rip"] + + # Fill in the unwound registers for an entry frame. + def unwind_entry_frame_registers(self, sp, unwind_info): + sp = sp.cast(self.typecache.void_starstar) + # Skip the "result" push. + sp = sp + 1 + for reg in self.PUSHED_REGS: + data = sp.dereference() + sp = sp + 1 + unwind_info.add_saved_register(reg, data) + if reg == "rbp": + unwind_info.add_saved_register(self.SP_REGISTER, sp) + + +class SpiderMonkeyUnwinder(Unwinder): + """The unwinder object. This provides the "user interface" to the JIT + unwinder, and also handles constructing or destroying UnwinderState + objects as needed.""" + + # A list of all the possible unwinders. See |self.make_unwinder|. + UNWINDERS = [x64UnwinderState] + + def __init__(self, typecache): + super(SpiderMonkeyUnwinder, self).__init__("SpiderMonkey") + self.typecache = typecache + self.unwinder_state = None + + # Disabled by default until we figure out issues in gdb. + self.enabled = False + gdb.write( + "SpiderMonkey unwinder is disabled by default, to enable it type:\n" + + "\tenable unwinder .* SpiderMonkey\n" + ) + # Some versions of gdb did not flush the internal frame cache + # when enabling or disabling an unwinder. This was fixed in + # the same release of gdb that added the breakpoint_created + # event. + if not hasattr(gdb.events, "breakpoint_created"): + gdb.write("\tflushregs\n") + + # We need to invalidate the unwinder state whenever the + # inferior starts executing. This avoids having a stale + # cache. + gdb.events.cont.connect(self.invalidate_unwinder_state) + assert self.test_sentinels() + + def test_sentinels(self): + # Self-check. + regs = {} + for unwinder in self.UNWINDERS: + if unwinder.SENTINEL_REGISTER in regs: + return False + regs[unwinder.SENTINEL_REGISTER] = 1 + return True + + def make_unwinder(self, pending_frame): + # gdb doesn't provide a good way to find the architecture. + # See https://sourceware.org/bugzilla/show_bug.cgi?id=19399 + # So, we look at each known architecture and see if the + # corresponding "unique register" is known. + for unwinder in self.UNWINDERS: + try: + pending_frame.read_register(unwinder.SENTINEL_REGISTER) + except Exception: + # Failed to read the register, so let's keep going. + # This is more fragile than it might seem, because it + # fails if the sentinel register wasn't saved in the + # previous frame. + continue + return unwinder(self.typecache) + return None + + def __call__(self, pending_frame): + if self.unwinder_state is None or not self.unwinder_state.check(): + self.unwinder_state = self.make_unwinder(pending_frame) + if not self.unwinder_state: + return None + return self.unwinder_state.unwind(pending_frame) + + def invalidate_unwinder_state(self, *args, **kwargs): + self.unwinder_state = None + + +def register_unwinder(objfile): + """Register the unwinder and frame filter with |objfile|. If |objfile| + is None, register them globally.""" + + type_cache = UnwinderTypeCache() + unwinder = None + # This currently only works on Linux, due to parse_proc_maps. + if _have_unwinder and platform.system() == "Linux": + unwinder = SpiderMonkeyUnwinder(type_cache) + gdb.unwinder.register_unwinder(objfile, unwinder, replace=True) + # We unconditionally register the frame filter, because at some + # point we'll add interpreter frame filtering. + filt = SpiderMonkeyFrameFilter(type_cache, unwinder) + if objfile is None: + objfile = gdb + objfile.frame_filters[filt.name] = filt |