安全体系架构与模型

信息安全模型

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1 计算机体系Computer Architecture •计算机体系结构是指组成计算机的基本组件（fundamental elements）

•主要硬件组件:

–

CPU, memory, input/output devices.

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1.1 中央处理单元CPU

–算术逻辑单元Arithmetic Logic Unit (ALU) Performa data transfer, arithmetic, data editing –控制单元Control logic: coordinate, select,

interprets of instructions

–多个一般寄存器registers

–一个指令寄存器instruction register

–一个程序计数器program counter

–片内内存on-chip local memory

•Store instructions and data needed by CPU 22:55

1.2 CPU

•Buffer overflow 缓冲区溢出

Data being processed is entered into the CPU in blocks at a time. If the software instructions do not properly set the boundaries for how much data can come in as a block, extra data can slip in and be executed.

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1.3 存储器Memory

•高速缓存Cache Memory

–Relatively small amount of very high RAM, holds instructions and data used by currently executing program.

•随机存取存储器Random Access Memory(RAM)–非永久存储-Is a volatile memory, because when power is lost -> information is lost

–Memory where locations can be directly addressed and the data can be altered

–动态DRAM-Requires that that data held within it be periodically refreshed because the data dissipates and decays.

–静态SRAM uses latches to store each bit.

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Memory

•可编程逻辑设备Programmable Logic Device (PLD)–ROM,PAL (Programmable Array Logic),FPGA

•只读存储器Read Only Memory(ROM)

–永久性non volatile storage where locations can be

directly addressed.

–Software that is stored within ROM is called firmware –EPROM－Erasable and programmable read-only

memory

–EEPROM－Electrically Erasable Programmable Read Only Memories

–EAROM

–Flash memories

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1.4 存储器映射Memory Mapping •主存储Real or primary memory

–直接可寻址,used for the storage of instructions and data –通常为高速RAM (Random Access Memory)

•次级存储Secondary memory

–速度较慢(硬盘，软盘，CD-ROM)

–永久性Non-volatile storage

•时序存储Sequential memory

–Info be obtained sequentially.

–Example: 磁带(Magnetic tape)

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存储器映射Memory Mapping

•虚存Virtual memory

–Uses secondary memory in conjunction with primary memory to present a CPU with a larger, apparent

address space of the real memory locations

–Virtual memory=Real storage + Auxiliary Storage

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内存寻址Memory addressing

•寄存器寻址Register addressing

–Addressing the registers within a CPU or special purpose registers

•直接寻址Direct addressing

–Addressing portion of primary memory by the actual address.

Without reference to a storage location containing another

address

•绝对寻址Absolute addressing

–All of the primary memory space

–=relative address+Base address

•变址寻址Indexed addressing

–By adding the contents of the address to that of an index register. 22:55