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Diffstat (limited to 'js/src/gdb/mozilla/jsval.py')
| -rw-r--r-- | js/src/gdb/mozilla/jsval.py | 188 |
1 files changed, 188 insertions, 0 deletions
diff --git a/js/src/gdb/mozilla/jsval.py b/js/src/gdb/mozilla/jsval.py new file mode 100644 index 0000000000..d01a5ceacc --- /dev/null +++ b/js/src/gdb/mozilla/jsval.py @@ -0,0 +1,188 @@ +# 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/. + +# Pretty-printers for SpiderMonkey's JS::Value. + +import struct + +import gdb +import gdb.types + +import mozilla.prettyprinters +from mozilla.prettyprinters import pretty_printer + +# Forget any printers from previous loads of this module. +mozilla.prettyprinters.clear_module_printers(__name__) + +# See Value.h [SMDOC] JS::Value Boxing Formats for details on the JS::Value boxing +# formats handled below. + + +class Box(object): + def __init__(self, asBits, jtc): + self.asBits = asBits + self.jtc = jtc + # Value::asBits is uint64_t, but somehow the sign bit can be botched + # here, even though Python integers are arbitrary precision. + if self.asBits < 0: + self.asBits = self.asBits + (1 << 64) + + # Return this value's type tag. + def tag(self): + raise NotImplementedError + + # Return this value as a 32-bit integer, double, or address. + def as_uint32(self): + raise NotImplementedError + + def as_double(self): + packed = struct.pack("q", self.asBits) + (unpacked,) = struct.unpack("d", packed) + return unpacked + + def as_address(self): + raise NotImplementedError + + +class Punbox(Box): + # Packed non-number boxing --- the format used on x86_64. It would be nice to + # simply call Value::toInt32, etc. here, but the debugger is likely to see many + # Values, and doing several inferior calls for each one seems like a bad idea. + + FULL_WIDTH = 64 + TAG_SHIFT = 47 + PAYLOAD_MASK = (1 << TAG_SHIFT) - 1 + TAG_MASK = (1 << (FULL_WIDTH - TAG_SHIFT)) - 1 + TAG_MAX_DOUBLE = 0x1FFF0 + TAG_TYPE_MASK = 0x0000F + + def tag(self): + tag = self.asBits >> Punbox.TAG_SHIFT + if tag <= Punbox.TAG_MAX_DOUBLE: + return self.jtc.DOUBLE + else: + return tag & Punbox.TAG_TYPE_MASK + + def as_uint32(self): + return int(self.asBits & ((1 << 32) - 1)) + + def as_address(self): + return gdb.Value(self.asBits & Punbox.PAYLOAD_MASK) + + +class Nunbox(Box): + TAG_SHIFT = 32 + TAG_CLEAR = 0xFFFF0000 + PAYLOAD_MASK = 0xFFFFFFFF + TAG_TYPE_MASK = 0x0000000F + + def tag(self): + tag = self.asBits >> Nunbox.TAG_SHIFT + if tag < Nunbox.TAG_CLEAR: + return self.jtc.DOUBLE + return tag & Nunbox.TAG_TYPE_MASK + + def as_uint32(self): + return int(self.asBits & Nunbox.PAYLOAD_MASK) + + def as_address(self): + return gdb.Value(self.asBits & Nunbox.PAYLOAD_MASK) + + +class JSValueTypeCache(object): + # Cache information about the Value type for this objfile. + + def __init__(self, cache): + # Capture the tag values. + d = gdb.types.make_enum_dict(gdb.lookup_type("JSValueType")) + + # The enum keys are prefixed when building with some compilers (clang at + # a minimum), so use a helper function to handle either key format. + def get(key): + val = d.get(key) + if val is not None: + return val + return d["JSValueType::" + key] + + self.DOUBLE = get("JSVAL_TYPE_DOUBLE") + self.INT32 = get("JSVAL_TYPE_INT32") + self.UNDEFINED = get("JSVAL_TYPE_UNDEFINED") + self.BOOLEAN = get("JSVAL_TYPE_BOOLEAN") + self.MAGIC = get("JSVAL_TYPE_MAGIC") + self.STRING = get("JSVAL_TYPE_STRING") + self.SYMBOL = get("JSVAL_TYPE_SYMBOL") + self.BIGINT = get("JSVAL_TYPE_BIGINT") + self.NULL = get("JSVAL_TYPE_NULL") + self.OBJECT = get("JSVAL_TYPE_OBJECT") + + # Let self.magic_names be an array whose i'th element is the name of + # the i'th magic value. + d = gdb.types.make_enum_dict(gdb.lookup_type("JSWhyMagic")) + self.magic_names = list(range(max(d.values()) + 1)) + for (k, v) in d.items(): + self.magic_names[v] = k + + # Choose an unboxing scheme for this architecture. + self.boxer = Punbox if cache.void_ptr_t.sizeof == 8 else Nunbox + + +@pretty_printer("JS::Value") +class JSValue(object): + def __init__(self, value, cache): + # Save the generic typecache, and create our own, if we haven't already. + self.cache = cache + if not cache.mod_JS_Value: + cache.mod_JS_Value = JSValueTypeCache(cache) + self.jtc = cache.mod_JS_Value + + self.value = value + self.box = self.jtc.boxer(value["asBits_"], self.jtc) + + def to_string(self): + tag = self.box.tag() + + if tag == self.jtc.UNDEFINED: + return "$JS::UndefinedValue()" + if tag == self.jtc.NULL: + return "$JS::NullValue()" + if tag == self.jtc.BOOLEAN: + return "$JS::BooleanValue(%s)" % str(self.box.as_uint32() != 0).lower() + if tag == self.jtc.MAGIC: + value = self.box.as_uint32() + if 0 <= value and value < len(self.jtc.magic_names): + return "$JS::MagicValue(%s)" % (self.jtc.magic_names[value],) + else: + return "$JS::MagicValue(%d)" % (value,) + + if tag == self.jtc.INT32: + value = self.box.as_uint32() + signbit = 1 << 31 + value = (value ^ signbit) - signbit + return "$JS::Int32Value(%s)" % value + + if tag == self.jtc.DOUBLE: + return "$JS::DoubleValue(%s)" % self.box.as_double() + + if tag == self.jtc.STRING: + value = self.box.as_address().cast(self.cache.JSString_ptr_t) + elif tag == self.jtc.OBJECT: + value = self.box.as_address().cast(self.cache.JSObject_ptr_t) + elif tag == self.jtc.SYMBOL: + value = self.box.as_address().cast(self.cache.JSSymbol_ptr_t) + elif tag == self.jtc.BIGINT: + return "$JS::BigIntValue()" + else: + value = "unrecognized!" + return "$JS::Value(%s)" % (value,) + + def is_undefined(self): + return self.box.tag() == self.jtc.UNDEFINED + + def get_string(self): + assert self.box.tag() == self.jtc.STRING + return self.box.as_address().cast(self.cache.JSString_ptr_t) + + def get_private(self): + assert self.box.tag() == self.jtc.DOUBLE + return self.box.asBits |