【angr源码分析】2. Block

工具

angr\block.py

Block类

factory中的block方法返回了Block的对象

class Block(object):

def _init_():

参数也没有注释，心累。

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def __init__(self, 
             addr, 
             project=None,
             arch=None,
             size=None,
             byte_string=None, #之前编译了什么东西，然后传进来
             vex=None, #该block的中间语言，没有设置的话就用engine生成
             thumb=False, #是否是ARM的thumb指令集
             backup_state=None,
             opt_level=None, 
             num_inst=None, #number of instructions
             traceflags=0, 
             strict_block_end=None):

    # set up arch
    if project is not None:
        self.arch = project.arch
    else:
        self.arch = arch

    .... ....
    
    self._project = project
    self.thumb = thumb
    self.addr = addr
    self._opt_level = opt_level
    
    #byte_string和project不能同时为空。目前还不清楚byte_string的用途
    if self._project is None and byte_string is None:
        raise ValueError('"byte_string" has to be specified if "project" is not provided.')
    
    if size is None:
        if byte_string is not None:
            size = len(byte_string)
        elif vex is not None:
            size = vex.size
        else:
            #lift方法用于获取中间语言（具体功能未知）
            #_vex_engine实际上调用了factory.default_engine
            vex = self._vex_engine.lift(
                    clemory=project.loader.memory,
                    state=backup_state,
                    insn_bytes=byte_string,
                    addr=addr,
                    thumb=thumb,
                    opt_level=opt_level,
                    num_inst=num_inst,
                    traceflags=traceflags,
                    strict_block_end=strict_block_end)
            size = vex.size

可以看到，调用了vex = self._vex_engine.lift(... ...) 。在engine中，_vex_engine实际上是factory.default_engine，而default_engine在 ‘default’ preset中使用的实际上是 SimEngineVEX的对象。所以调用的lift方法实际上是SimEngineVEX.lift ，返回一个IRSB对象。