mmu | 易学教程

How do Operating Systems prevent programs from accessing memory?

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问题 My understanding currently is, I can write an operating system in C I can write a program for that operating system in C When I write an operating system I can see all of the memory When I write a program the operating system hides memory from other programs from me. Whenever a program runs inside an OS it appears to the program as if the memory it is allocated is all the memory the computer has How does the CPU / OS achieve this? Is this something purely implemented on the software level? Or

How do Operating Systems prevent programs from accessing memory?

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How do Operating Systems prevent programs from accessing memory?

阅读更多关于 How do Operating Systems prevent programs from accessing memory?

How do Operating Systems prevent programs from accessing memory?

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What enforces memory protection in an OS?

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来源： https://stackoverflow.com/questions/15045375/what-enforces-memory-protection-in-an-os

What enforces memory protection in an OS?

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来源： https://stackoverflow.com/questions/15045375/what-enforces-memory-protection-in-an-os

When accessing memory, will the page table accessed/dirty bit be set under a cache hit situation?

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问题 As far as I know, a memory access of CPU involves CPU cache and MMU. CPU will try to find its target in cache and if a cache miss happens, CPU will turn to MMU. During accessing by MMU, the accessed/dirty bit of correspondent page table entry will be set by hardware. However to the best of my knowledge, most CPU design won't trigger the MMU unless there's a cache miss, and here my problem is, will the accessed/dirty bit of page table entry still be set under a cache hit? Or it's architecture

Why does ARM have 64KB Large Pages? [closed]

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问题 Closed . This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed 3 years ago . The ARM720T user manual mentions small and large pages. Since the ARM 720T requires a 64KB page table entry to be duplicated 16 times in the page table, why not place 16 small page (4KB) entries to mimic a 64KB page entry instead of using a large page in the first place? 回答1:

嵌入式学习-MMU

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原文： https://blog.csdn.net/u011003120/article/details/51812188 参考： https://blog.csdn.net/groundhappy/article/details/54889677 MMU 存储器管理单元，在之前因为是操作物理地址，不需要MMU,因此是处于关闭状态的，而这次则是打开MMU并且使用MMU. 一、MMU的作用 1.将虚拟地址转化为物理地址 2.进行访问权限的管理看上图可以得知，有三个运行的程序，他们的虚拟地址都为0x400000,但是若要使用物理地址，他们的物理地址不能够相同，因此就需要一个机制，使他们的相同的虚拟地址对应不同的物理地址，这个机制就是上图中的Page tables（即页表），虚拟地址通过查表的方式对应到不同的物理地址上。二、地址转化首先需要知道的是，以段(Section，1M)的方式进行转换时只用到一级页表，而页(Page)的方式进行转换时用到两级页表，有粗也转换和细页转换两种，页的大小有3种：大页(64KB)、小页(4KB)和极小页（1KB）。 1.地址转化总体分析整个地址转换的过程分为了两步，为一级转换和二级转换。虚拟地址的[31:20]位作为一个表的索引，表的名字为translation table，即TTB,如果表的后两位为00，则为无效的转换，如上图，如果后两位为01

进程和程序之间的区别CPU和MMU

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进程和程序的区别程序，只占用磁盘的空间。进程运行在操作系统之上，占用内存，cpu等系统资源。并发同一时间运行多个程序，多个进程同时在运行单道程序设计 A堵塞，B只能进行等待，即使CPU处于空闲状态，而在人机交互的时候堵塞的时候是必然的结果多道程序设计时钟中断，到了指定的时间程序必须中断 CPU和MMU 存储的介质越大速度越慢内存使用的是电信号，速度是非常快的 cache缓存是在寄存器和内存之间的来源： https://www.cnblogs.com/fandx/p/12518395.html