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Operating Systems Slides 1 - Introduction
 

Operating Systems Slides 1 - Introduction

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    Operating Systems Slides 1 - Introduction Operating Systems Slides 1 - Introduction Presentation Transcript

    • Operating System Introduction Wang Xiaolin September 3, 2013 u wx672ster+os@gmail.com 1 / 35
    • Textbooks A.S. Tanenbaum. Modern Operating Systems. 3rd ed. Pearson Prentice Hall, 2008. Silberschatz, Galvin, and Gagne. Operating System Concepts Essentials. John Wiley & Sons, 2011. 邹恒明. 计算机的心智:操作系统之哲学原理. 机械工业出版社, 2009. D.P. Bovet and M. Cesatı́. Understanding The Linux Kernel. 3rd ed. O’Reilly, 2005. 2 / 35
    • Course Web Site Course web site: http://cs3.swfu.edu.cn/moodle Lecture slides: http://cs2.swfu.edu.cn/∼wx672/lecture_notes/os/slides/ Source code: http://cs2.swfu.edu.cn/∼wx672/lecture_notes/os/src/ Sample lab report: http://cs2.swfu.edu.cn/∼wx672/lecture_notes/os/sample- report/ 3 / 35
    • What’s an Operating System? ▶ “Everything a vendor ships when you order an operating system” ▶ It’s the program that runs all the time ▶ It’s a resource manager - Each program gets time with the resource Each program gets space on the resource ▶ It’s a control program - Controls execution of programs to prevent errors and improper use of the computer ▶ No universally accepted definition 4 / 35
    • System Goals . Convenient vs. Efficient .. . ▶ Convenient for the user — for PCs ▶ Efficient — for mainframes, multiusers ▶ UNIX - Started with keyboard + printer, none paid to convenience - Now, still concentrating on efficiency, with GUI support 5 / 35
    • History of Operating Systems 1401 7094 1401 (a) (b) (c) (d) (e) (f) Card reader Tape drive Input tape Output tape System tape Printer Fig. 1-2. An early batch system. (a) Programmers bring cards to 1401. (b) 1401 reads batch of jobs onto tape. (c) Operator carries input tape to 7094. (d) 7094 does computing. (e) Operator carries output tape to 1401. (f) 1401 prints output. 6 / 35
    • ▶ First generation 1945 - 1955 - vacuum tubes, plug boards ▶ Second generation 1955 - 1965 - transistors, batch systems ▶ Third generation 1965 1980 - ICs and multiprogramming ▶ Fourth generation 1980 present - personal computers 7 / 35
    • Job 3 Job 2 Job 1 Operating system Memory partitions Fig. 1-4. A multiprogramming system with three jobs in memory. 8 / 35
    • . Multi-programming is the first instance where the OS must make decisions for the users .. . ▶ Job scheduling — decides which job should be loaded into the memory. ▶ Memory management — because several programs in memory at the same time ▶ CPU scheduling — choose one job among all the jobs are ready to run ▶ Process management — make sure processes don’t offend each other 9 / 35
    • The Operating System Zoo ▶ Mainframe operating systems ▶ Server operating systems ▶ Multiprocessor operating systems ▶ Personal computer operating systems ▶ Real-time operating systems ▶ Embedded operating systems ▶ Smart card operating systems 10 / 35
    • OS Services Like a government . Helping the users: .. . ▶ User interface ▶ Program execution ▶ I/O operation ▶ File system manipulation ▶ Communication ▶ Error detection . Keeping the system efficient: .. . ▶ Resource allocation ▶ Accounting ▶ Protection and security 11 / 35
    • A Computer System Banking system Airline reservation Operating system Web browser Compilers Editors Application programs Hardware System programs Command interpreter Machine language Microarchitecture Physical devices Fig. 1-1. A computer system consists of hardware, system pro- 12 / 35
    • CPU Working Cycle Fetch unit Fetch unit Fetch unit Decode unit Execute unit (a) Fig. 1-6. (a) A three-stage pipeline. ( 1. Fetch the first instruction from memory 2. Decode it to determine its type and operands 3. execute it . Special CPU Registers .. . ▶ Program counter(PC): keeps the memory address of the next instruction to be fetched ▶ Stack pointer(SP): points to the top of the current stack in memory ▶ Program status(PS): holds condition code bits processor state 13 / 35
    • System Bus Monitor Keyboard Floppy disk drive Hard disk drive Hard disk controller Floppy disk controller Keyboard controller Video controller MemoryCPU Bus Fig. 1-5. Some of the components of a simple personal computer. ▶ Address Bus: specifies the memory locations (addresses) for the data transfers ▶ Data Bus: holds the data transfered. bidirectional ▶ Control Bus: contains various lines used to route timing and control signals throughout the system 14 / 35
    • Controllers and Peripherals ▶ Peripherals are real devices controlled by controller chips ▶ Controllers are processors like the CPU itself, have control registers ▶ Device driver writes to the registers, thus control it ▶ Controllers are connected to the CPU and to each other by a variety of buses 15 / 35
    • ISA bridge Modem Mouse PCI bridgeCPU Main memory SCSI USB Local bus Sound card Printer Available ISA slot ISA bus IDE disk Available PCI slot Key- board Mon- itor Graphics adaptor Level 2 cache Cache bus Memory bus PCI bus 16 / 35
    • Motherboard Chipsets +--------------+ | Intel Core 2 | | Processor | | (CPU) | +--------------+ | Front Side Bus | +------------+ DDR2 +-------------+ +---------------+ | System RAM |<----------->| Northbridge |<--->| Graphics Card | +------------+ Channel | Chip | +---------------+ +-------------+ | DMI Interface | +---------------------+ +-------------+ +------------------+ | BIOS (flash memory) |<--->| |<--->| Power management | +---------------------+ | Southbridge | +------------------+ | Serial ATA Ports |<--->| Chip |<--->| Clock generation | +---------------------+ | | +------------------+ | USB Ports |<--->| |<--->| PCI Bus | +---------------------+ +-------------+ +------------------+ 17 / 35
    • ▶ The CPU doesn’t know what it’s connected to - CPU test bench? network router? toaster? brain implant? ▶ The CPU talks to the outside world through its pins - some pins to transmit the physical memory address - other pins to transmit the values ▶ The CPU’s gateway to the world is the front-side bus . Intel Core 2 QX6600 .. . ▶ 33 pins to transmit the physical memory address - so there are 233 choices of memory locations ▶ 64 pins to send or receive data - so data path is 64-bit wide, or 8-byte chunks This allows the CPU to physically address 64GB of memory (233 × 8B) 18 / 35
    • . Some physical memory addresses are mapped away! .. . ▶ only the addresses, not the spaces ▶ Memory holes - 640KB ∼ 1MB - /proc/iomem . Memory-mapped I/O .. . ▶ BIOS ROM ▶ video cards ▶ PCI cards ▶ ... This is why 32-bit OSes have problems using 4 gigs of RAM. 0xFFFFFFFF +--------------------+ 4GB Reset vector | JUMP to 0xF0000 | 0xFFFFFFF0 +--------------------+ 4GB - 16B | Unaddressable | | memory, real mode | | is limited to 1MB. | 0x100000 +--------------------+ 1MB | System BIOS | 0xF0000 +--------------------+ 960KB | Ext. System BIOS | 0xE0000 +--------------------+ 896KB | Expansion Area | | (maps ROMs for old | | peripheral cards) | 0xC0000 +--------------------+ 768KB | Legacy Video Card | | Memory Access | 0xA0000 +--------------------+ 640KB | Accessible RAM | | (640KB is enough | | for anyone - old | | DOS area) | 0 +--------------------+ 0 What if you don’t have 4G RAM? 19 / 35
    • . the northbridge .. . 1. receives a physical memory request 2. decides where to route it - to RAM? to video card? to ...? - decision made via the memory address map 20 / 35
    • Bootstrapping . Can you pull yourself up by your own bootstraps? .. . A computer cannot run without first loading software but must be running before any software can be loaded. BIOS Initialization MBR Initialization Kernel Early Boot Loader Initialization Kernel Full User Mode Process First Kernel Services Protected Mode Switch to BIOS Services Hardware CPU in Real Mode CPU in Protected Mode Time Flow 21 / 35
    • Intel x86 Bootstrapping 1. BIOS (0xfffffff0) 1). POST 2). HW init 3). Find a boot device (FD,CD,HD...) 4). Copy sector zero (MBR) of the boot device (e.g. HD) to RAM (0x00007c00) 2. MBR – the first 512 bytes, contains ▶ Small code (< 446 Bytes), e.g. GRUB stage 1, for loading GRUB stage 2 ▶ the primary partition table (= 64 Bytes) ▶ its job is to load the second-stage boot loader. 3. GRUB stage 2 — load the OS kernel into RAM 4. startup 5. init — the first user-space program |<-------------Master Boot Record (512 Bytes)------------>| 0 439 443 445 509 511 +----//-----+----------+------+------//---------+---------+ | code area | disk-sig | null | partition table | MBR-sig | | 440 | 4 | 2 | 16x4=64 | 0xAA55 | +----//-----+----------+------+------//---------+---------+ sudo hd -n512 /dev/sda 22 / 35
    • Why Interrupt? . While a process is reading a disk file, can we do... .. . while(!done_reading_a_file()) { let_CPU_wait(); // or... lend_CPU_to_others(); } operate_on_the_file(); 23 / 35
    • Modern OS are Interrupt Driven ▶ Hardware INT by sending a signal to CPU ▶ Software INT by executing a system call ▶ Trap (exception) is a software-generated INT coursed by an error or by a specific request from an user program ▶ Interrupt vector is an array of pointers pointing to the memory addresses of interrupt handlers. This array is indexed by a unique device number ∼$ less /proc/devices ∼$ less /proc/interrupts 24 / 35
    • Programmable Interrupt Controllers Interrupt INT IRQ 0 (clock) IRQ 1 (keyboard) IRQ 3 (tty 2) IRQ 4 (tty 1) IRQ 5 (XT Winchester) IRQ 6 (floppy) IRQ 7 (printer) IRQ 8 (real time clock) IRQ 9 (redirected IRQ 2) IRQ 10 IRQ 11 IRQ 12 IRQ 13 (FPU exception) IRQ 14 (AT Winchester) IRQ 15 ACK Master interrupt controller INT ACK Slave interrupt controller INT CPU INTA Interrupt ack s y s t ^ e m d a t ^ a b u s Figure 2-33. Interrupt processing hardware on a 32-bit Intel PC. 25 / 35
    • Interrupt Processing CPU Interrupt controller Disk controller Disk drive Current instruction Next instruction 1. Interrupt 3. Return 2. Dispatch to handler Interrupt handler (b)(a) 1 3 4 2 Fig. 1-10. (a) The steps in starting an I/O device and getting an interrupt. (b) Interrupt processing involves taking the interrupt, running the interrupt handler, and returning to the user program. 26 / 35
    • Interrupt Timeline 1.2 Computer-System Organization 9 user process executing CPU I/O interrupt processing I/O request transfer done I/O request transfer done I/O device idle transferring Figure 1.3 Interrupt time line for a single process doing output. the interrupting device. Operating systems as different as Windows and UNIX dispatch interrupts in this manner. 27 / 35
    • System Calls . A System Call .. . ▶ is how a program requests a service from an OS kernel ▶ provides the interface between a process and the OS 28 / 35
    • Program 1 Program 2 Program 3 +---------+ +---------+ +---------+ | fork() | | vfork() | | clone() | +---------+ +---------+ +---------+ | | | V V V +-----------------------------------+ | C Library | +-----------------o-----------------+ | User space ------------------|----------------------------------- | Kernel space | | +---------+ V : ... : +-------------+ 3 +---------+ | System call |--o---->| fork() |--> sys_fork() ---. +-------------+ | +---------+ | | : ... : | | 120 +---------+ | |---->| clone() |--> sys_clone() --| | +---------+ | | : ... : | | 289 +---------+ | ‘---->| vfork() |--> sys_vfork() --| +---------+ | : ... : V +---------+ do_fork() System Call Table 29 / 35
    • User program 2  User program 1  Kernel call Service  procedure  Dispatch table  User programs  run in user mode  Operating  system  runs in  kernel mode 4  3  1 2  Mainmemory Figure 1-16. How a system call can be made: (1) User pro- gram traps to the kernel. (2) Operating system determines ser- vice number required. (3) Operating system calls service pro- cedure. (4) Control is returned to user program. 30 / 35
    • . The 11 steps in making the system call read(fd,buffer,nbytes) .. . Return to caller 4 10 6 0 9 7 8 3 2 1 11 Dispatch Sys call handler Address 0xFFFFFFFF User space Kernel space (Operating system) Library procedure read User program calling read Trap to the kernel Put code for read in register Increment SP Call read Push fd Push &buffer Push nbytes 5 31 / 35
    • Process management Call Description pid = fork( ) Create a child process identical to the parent pid = waitpid(pid, &statloc, options) Wait for a child to terminate s = execve(name, argv, environp) Replace a process’ core image exit(status) Terminate process execution and return status File management Call Description fd = open(file, how, ...) Open a file for reading, writing or both s = close(fd) Close an open file n = read(fd, buffer, nbytes) Read data from a file into a buffer n = write(fd, buffer, nbytes) Write data from a buffer into a file position = lseek(fd, offset, whence) Move the file pointer s = stat(name, &buf) Get a file’s status information Directory and file system management Call Description s = mkdir(name, mode) Create a new directory s = rmdir(name) Remove an empty directory s = link(name1, name2) Create a new entry, name2, pointing to name1 s = unlink(name) Remove a directory entry s = mount(special, name, flag) Mount a file system s = umount(special) Unmount a file system Miscellaneous Call Description s = chdir(dirname) Change the working directory s = chmod(name, mode) Change a file’s protection bits s = kill(pid, signal) Send a signal to a process 32 / 35
    • System Call Examples . fork() .. . 1 #include <stdio.h> 2 #include <unistd.h> 3 4 int main () 5 { 6 printf("Hello World!n"); 7 fork(); 8 printf("Goodbye Cruel World!n"); 9 } man 2 fork 33 / 35
    • . exec() .. . 1 #include <stdio.h> 2 #include <unistd.h> 3 4 int main () 5 { 6 printf("Hello World!n"); 7 if(fork() != 0 ) 8 printf("I am the parent process.n"); 9 else { 10 printf("A child is listing the directory contents...n"); 11 execl("/bin/ls", "ls", "-al", NULL); 12 } 13 return 0; 14 } man 3 exec 34 / 35
    • Hardware INT vs. Software INT Device: Send electrical signal to interrupt controller. Controller: 1. Interrupt CPU. 2. Send digital identification of interrupting device. Kernel: 1. Save registers. 2. Execute driver software to read I/O device. 3. Send message. 4. Restart a process (not necessarily interrupted process). Caller: 1. Put message pointer and destination of message into CPU registers. 2. Execute software interrupt instruction. Kernel: 1. Save registers. 2. Send and/or receive message. 3. Restart a process (not necessarily calling process). (a) (b) Figure 2-34. (a) How a hardware interrupt is processed. (b) How a system call is made. 35 / 35