pydbg中关于process_snapshot的质疑

保存快照和恢复快照 其实是个比较复杂的事情，因为快照前后，内存可能分配了释放，保护属性可能也改变，或内存释放了被分配，

所以，只是简单的保存commit且是带写属性的内存还是不够的。其二是前后可能涉及句柄的关闭问题，快照前打开的句柄，只是一个数字，恢复了之后，可能在

快照后被关闭过，内核已经清楚这个对象，造成打开句柄失败，影响流程。

所以，要感知内存的变化，屏蔽掉句柄的关闭操作，过滤掉释放内存分配的操作，或许可能还有其它未想到的。

def process_snapshot (self):

        '''
        Take memory / context snapshot of the debuggee. All threads must be suspended before calling this routine.

        @raise pdx: An exception is raised on failure.
        @rtype:     pydbg
        @return:    Self
        '''

        self.pydbg_log("taking debuggee snapshot")

        do_not_snapshot = [PAGE_READONLY, PAGE_EXECUTE_READ,PAGE_GUARD, PAGE_NOACCESS]
        cursor          = 0

        # reset the internal snapshot data structure lists.
        self.memory_snapshot_blocks   = []
        self.memory_snapshot_contexts = []

        # enumerate the running threads and save a copy of their contexts.
        for thread_id in self.enumerate_threads():
            context = self.get_thread_context(None, thread_id)

            self.memory_snapshot_contexts.append(memory_snapshot_context(thread_id, context))

            self.pydbg_log("saving thread context of thread id: %08x" % thread_id)

        # scan through the entire memory range and save a copy of suitable memory blocks.
        while cursor < 0xFFFFFFFF:
            save_block = True

            try:
                mbi = self.virtual_query(cursor)
            except:
                break

            # do not snapshot blocks of memory that match the following characteristics.
            # XXX - might want to drop the MEM_IMAGE check to accomodate for self modifying code.
            # or mbi.Type == MEM_IMAGE
            if mbi.State != MEM_COMMIT:
                save_block = False

            for has_protection in do_not_snapshot:
                if mbi.Protect & has_protection:
                    save_block = False
                    break

            if save_block:
                self.pydbg_log("Adding %08x +%d to memory snapsnot." % (mbi.BaseAddress, mbi.RegionSize))

                # read the raw bytes from the memory block.
                data = self.read_process_memory(mbi.BaseAddress, mbi.RegionSize)

                self.memory_snapshot_blocks.append(memory_snapshot_block(mbi, data))

            cursor += mbi.RegionSize

        return self.ret_self()