fbchisellldbbase.py

#!/usr/bin/python

# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.

import json
import shlex

import lldb


class FBCommandArgument:  # noqa B903
    def __init__(
        self, short="", long="", arg="", type="", help="", default="", boolean=False
    ):
        self.shortName = short
        self.longName = long
        self.argName = arg
        self.argType = type
        self.help = help
        self.default = default
        self.boolean = boolean


class FBCommand:
    def name(self):
        return None

    def options(self):
        return []

    def args(self):
        return []

    def description(self):
        return ""

    def lex(self, commandLine):
        return shlex.split(commandLine)

    def run(self, arguments, option):
        pass


def isSuccess(error):
    # When evaluating a `void` expression, the returned value will indicate an
    # error. This error is named: kNoResult. This error value does *not* mean
    # there was a problem. This logic follows what the builtin `expression`
    # command does. See: https://git.io/vwpjl (UserExpression.h)
    kNoResult = 0x1001
    return error.success or error.value == kNoResult


def importModule(frame, module):
    options = lldb.SBExpressionOptions()
    options.SetLanguage(lldb.eLanguageTypeObjC)
    value = frame.EvaluateExpression("@import " + module, options)
    return isSuccess(value.error)


# evaluates expression in Objective-C++ context, so it will work even for
# Swift projects
def evaluateExpressionValue(
    expression,
    printErrors=True,
    language=lldb.eLanguageTypeObjC_plus_plus,
    tryAllThreads=False,
):
    frame = (
        lldb.debugger.GetSelectedTarget()
        .GetProcess()
        .GetSelectedThread()
        .GetSelectedFrame()
    )
    options = lldb.SBExpressionOptions()
    options.SetLanguage(language)

    # Allow evaluation that contains a @throw/@catch.
    #   By default, ObjC @throw will cause evaluation to be aborted. At the time
    #   of a @throw, it's not known if the exception will be handled by a @catch.
    #   An exception that's caught, should not cause evaluation to fail.
    options.SetTrapExceptions(False)

    # Give evaluation more time.
    options.SetTimeoutInMicroSeconds(5000000)  # 5s

    # Most Chisel commands are not multithreaded.
    options.SetTryAllThreads(tryAllThreads)

    value = frame.EvaluateExpression(expression, options)
    error = value.GetError()

    # Retry if the error could be resolved by first importing UIKit.
    if (
        error.type == lldb.eErrorTypeExpression
        and error.value == lldb.eExpressionParseError
        and importModule(frame, "UIKit")
    ):
        value = frame.EvaluateExpression(expression, options)
        error = value.GetError()

    if printErrors and not isSuccess(error):
        print(error)

    return value


def evaluateInputExpression(expression, printErrors=True):
    # HACK
    if expression.startswith("(id)"):
        return evaluateExpressionValue(expression, printErrors=printErrors).GetValue()

    frame = (
        lldb.debugger.GetSelectedTarget()
        .GetProcess()
        .GetSelectedThread()
        .GetSelectedFrame()
    )
    options = lldb.SBExpressionOptions()
    options.SetTrapExceptions(False)
    value = frame.EvaluateExpression(expression, options)
    error = value.GetError()

    if printErrors and error.Fail():
        print(error)

    return value.GetValue()


def evaluateIntegerExpression(expression, printErrors=True):
    output = evaluateExpression("(int)(" + expression + ")", printErrors).replace(
        "'", ""
    )
    if output.startswith("\\x"):  # Booleans may display as \x01 (Hex)
        output = output[2:]
    elif output.startswith("\\"):  # Or as \0 (Dec)
        output = output[1:]
    return int(output, 0)


def evaluateBooleanExpression(expression, printErrors=True):
    return (
        int(evaluateIntegerExpression("(BOOL)(" + expression + ")", printErrors)) != 0
    )


def evaluateExpression(expression, printErrors=True):
    return evaluateExpressionValue(expression, printErrors=printErrors).GetValue()


def describeObject(expression, printErrors=True):
    return evaluateExpressionValue(
        "(id)(" + expression + ")", printErrors
    ).GetObjectDescription()


def evaluateEffect(expression, printErrors=True):
    evaluateExpressionValue("(void)(" + expression + ")", printErrors=printErrors)


def evaluateObjectExpression(expression, printErrors=True):
    return evaluateExpression("(id)(" + expression + ")", printErrors)


def evaluateCStringExpression(expression, printErrors=True):
    ret = evaluateExpression(expression, printErrors)

    process = lldb.debugger.GetSelectedTarget().GetProcess()
    error = lldb.SBError()
    ret = process.ReadCStringFromMemory(int(ret, 16), 256, error)
    if error.Success():
        return ret
    else:
        if printErrors:
            print(error)
        return None


RETURN_MACRO = """
#define IS_JSON_OBJ(obj)\
    (obj != nil && ((bool)[NSJSONSerialization isValidJSONObject:obj] ||\
    (bool)[obj isKindOfClass:[NSString class]] ||\
    (bool)[obj isKindOfClass:[NSNumber class]]))
#define RETURN(ret) ({\
    if (!IS_JSON_OBJ(ret)) {\
        (void)[NSException raise:@"Invalid RETURN argument" format:@""];\
    }\
    NSDictionary *__dict = @{@"return":ret};\
    NSData *__data = (id)[NSJSONSerialization dataWithJSONObject:__dict options:0 error:NULL];\
    NSString *__str = (id)[[NSString alloc] initWithData:__data encoding:4];\
    (char *)[__str UTF8String];})
#define RETURNCString(ret)\
    ({NSString *___cstring_ret = [NSString stringWithUTF8String:ret];\
    RETURN(___cstring_ret);})
"""


def check_expr(expr):
    return expr.strip().split(";")[-2].find("RETURN") != -1


# evaluate a batch of Objective-C expressions, the last expression
# must contain a RETURN marco and it will automatic transform the
# Objective-C object to Python object
# Example:
#       >>> fbchisellldbbase.evaluate('NSString *str = @"hello world"; RETURN(@{@"key": str});')
#       {u'key': u'hello world'}
def evaluate(expr):
    if not check_expr(expr):
        raise Exception(
            "Invalid Expression, the last expression not include a RETURN family marco"
        )

    command = "({" + RETURN_MACRO + "\n" + expr + "})"
    ret = evaluateExpressionValue(command, printErrors=True)
    if not ret.GetError().Success():
        print(ret.GetError())
        return None
    else:
        process = lldb.debugger.GetSelectedTarget().GetProcess()
        error = lldb.SBError()
        ret = process.ReadCStringFromMemory(int(ret.GetValue(), 16), 2**20, error)
        if not error.Success():
            print(error)
            return None
        else:
            ret = json.loads(ret)
            return ret["return"]


def currentLanguage():
    return (
        lldb.debugger.GetSelectedTarget()
        .GetProcess()
        .GetSelectedThread()
        .GetSelectedFrame()
        .GetCompileUnit()
        .GetLanguage()
    )