操作系统课程设计75303

1、课程设计说明书学 院：计算机科学与工程学院专 业：计算机科学与技术姓名: 天驹学号：0900310327指导教师：黄廷辉2012年3 月 5 日操作系统课程设计报告GeekOS操作系统的研究与实现(项目0项目2)一、实验目的：熟悉GeekOS项目编译运行环境、核态进程的实现、用户态进程的实现、 进程调度策略和算法实现、分页存储管理的实现和文件系统的实现等。二、项目设计要求：GeekOSg计项目0：1. 搭建GeekOS勺编译和调试平台，掌握 GeekOS勺核进程工作原理。2. 熟悉键盘操作函数，编程实现一个核进程。该进程的功能是：接受键盘输 入的字符并显示到屏幕上，当输入 Ctrl+D时，结束

2、进程的运行。GeekOSg计项目1：1. 修改/geekos/elf.c文件：在函数Parse_ELF_Executable()中添加代码，分 析ELF格式的可执行文件(包括分析得出ELF文件头、程序头，获取可执行 文件长度、代码段、数据段等信息)，并填充Exe_Format数据结构中的域值。2. 掌握GeekOS在核心态运行用户程序的原理，为项目2的实现做准备。GeekOSS计项目2：本项目要求用户对以下几个文件进行修改：1. src/GeekOS/user.c文件中的函数Spawn()，其功能是生成一个新的用户 级进程。2. src/GeekOS/usre.c 文件中的函数 Switch_

3、To_User_Context()，调度程序 在执行一个新的进程前调用该函数以切换用户地址空间。3. src/GeekOS/elf.c 文件中的函数 Parse_ELF_Executable()。该函数的实现 要求和项目1相同。4. src/GeekOS/userseg.c 文件中主要是实现一些为实现对 src/GeekOS/user.c中高层操作支持的函数。(1) Destroy_User_Context()函数的功能是释放用户态进程占用的存资 源。(2) Load_User_Program()函数的功能是通过加载可执行文件镜像创建 新进程的User_Context结构。(3) Copy_F

4、rom_User()和 Copy_To_User()函数的功能是在用户地址空 间和核地址空间之间复制函数，在分段存储器管理模式下，只要段有效， 调用memcpy函数就可以实现这两个函数的功能。(4) Switch_To_Address_Space()函数的功能是通过将进程的 LDT装入 到LDT寄存器来激活用户的地址空间。5. src/GeekOS/kthread.c 文件中的 Start_User_Thread 函数和 Setup_User_Thread 函 数。(1) Setup_User_Thread()函数的功能是为进程初始化核堆栈，堆栈中是为进程首次进入用户态运行时设置处理器状态要使

5、用的数据。(2) Start_User_Thread() 是一个高层操作，该函数使用User_Context对象开始一个新进程-6. src/GeekOS/Syscall.c 文件中主要是实现用户程序要求核进行服务的一些 系统调用函数定义。要求用户实现的有Sys_Exit()函数、Sys_PrintString() 函数、Sys_GetKey()、Sys_SetAttr() 、Sys_Getcursor()、Sys_PutCursor() 函数、Sys_Wait()函数和Sys_GetPID()函数。这些函数在文件中有详细的 注释，按照提示用户可以很好实现它们的功能。最后，需要在main.c文

6、件中改写生成第一个用户态进程的函数调用：Spawnnit_Process(void)。需要注意的是：作为与用户沟通的界面，GeekOS 提供了一个简单的Shell，保存在PFAT文件系统，所以GeekOS系统启动后， 应启动shell程序/c/shell.exe运行，所以需要将/c/shell.exe作为可执行文件传递给Spawn函数的program参数，创建第一个用户态进程，然后由 它来创建其他进程。添加代码运行成功后，GeekOS就可以挂载shell，并能运行测试文件c.exe和 b.exe。三、如何建立开发环境：(一) 利用linux安装盘安装了 ubuntu1O.1O版本的linux操

7、作系统环境；(二) 联网后通过系统里的更新管理器更新了系统，并安装了语言包和必要的 驱动。(三) 在ubuntu软件中心下载安装了 NASM汇编器、Bochs PC模拟器以及 bochs-x插件(保证ubuntu10.10环境下的bochs正常运行)。四、项目设计原理：Make工作原理：在默认的方式下，只要输入 make命令就可以工作。具体的处理过程如下：(1)make会在当前目录下找文件名为“ Makefile ”或“ makefile ”的文件。 如果找到，它会找文件中的第一个目标文件(target )，在上面的例子中， 它会找到“ edit ”这个文件，并把这个文件作为最终的目标文件。(

8、3) 如果edit文件不存在，或是edit所依赖的后面的.o文件的修改时间要比edit这个文件新，那么，就会执行后面所定义的命令来生成edit这个文件。(4) 如果edit所依赖的.o文件也不存在，那么make会在当前文件中找目标 为.o文件的依赖性，如果找到则再根据那一个规则生成.o文件(这有点 像一个堆栈的过程)。(5) 如果指定的C文件和H文件是存在的，make会生成.o文件，然后再用.o 文件生成make的最终任务，也就是生成执行文件 edit。GeekOS的 makefile 文件功能：(1) 指定GeekOS如何被编译，哪些源文件被编译，哪些用户程序被编译 等等。通常不同项目的编译

9、仅仅需要修改这一部分。(2) 定义了编译GeekOS要用到的工具程序。(4)指定系统编译生成的指定文件。GeekOS项目的开发流程：1. 开始一个GeekOS项目，第一步是添加相应的代码。2. 在Linux下利用make命令编译系统，生成系统镜像文件。 $ cd /projectO/build $ make depend $ make3. 编写每个项目相应的Bochs的配置文件。4. 运行Bochs模拟器，执行GeekOS核。 $ cd /bochs $ bochs 运行后，屏幕上会有一些提示。运行GeekOS选择Beginsimulation ，如果GeekOS编译成功，并且bochs的配置

10、也 没问题，将会看到一个模拟 VGA的文本窗口，Geekos就能 运行程序输出相应信息(每个环境具体运行的命令格式会有一些不同)核线程的建立流程:Spawn («ReadFuliyOParsed LF_ExcutabSe()!LLcad_User_Pr ogram ()5卜-Start User Thread ()tSetup User Thread ()Attach_User.Context ()用户态进程创建流程五、项目设计的具体实现(程序代码)：GeekOSg计项目0：Main.c 文件：#in clude vgeekos/booti nfo.h> #include &l

11、t;geekos/string.h> #i nclude <geekos/scree n.h> #i nclude <geekos/mem.h>#i nclude vgeekos/crc32.h>#in elude <geekos/tss.h>#in elude <geekos/i nt.h>#i nclude <geekos/kthread.h>#include <geekos/trap.h>#i nclude <geekos/timer.h>#i nclude <geekos/keyboa

12、rd.h>/* Kernel C code entry point.* Initializes kernel subsystems, mounts filesystems,* and spaw ns init process.*/void Mai n( struct Boot_I nfo* boot Info) _In it_BSS();Ini t_Scree n();In it_Mem(bootI nfo);In it_CRC32();In it_TSS();lnit_ln terrupts();In it_Scheduler();In it_Traps();In it_Timer()

13、;In it_Keyboard();Set_Curre nt_Attr(ATTRIB(BLACK, GREEN|BRIGHT); Prin t("Welcome to GeekOS!n");Set_Curre nt_Attr(ATTRIB(BLACK, GRAY);void EchoCo un t()Keycode keycode;int count;coun t=0;while (1)if ( Read_Key( & keycode ) _if(keycode & 0x4000) = 0x4000)if(Wait_For_Key() & 0x00f

14、f) = 'd')/Pri nt("%c",Wait_For_Key();Set_Curre nt_Attr(ATTRIB(BLACK, RED);Print("Ctrl+dIs Entered! Program Ended!");Exit(1);elseif ( !(keycode & KEY_SPECIAL_FLAG&&!(keycode &KEY_RELEASE_FLAG)keycode &= Oxff;coun t=co un t+1;Set_Current_Attr(ATTRIB(BLAC

15、K, CYAN); Print( "%c", (keycode = 'r') ? 'n' : keycode );if(keycode='r')coun t=co un t-1;Set_Curre nt_Attr(ATTRIB(AMBER, BLUE);Prin t("The counnts is %d ",co un t);Prin t("n");coun t=0;struct Kern el_Thread *kerThd;kerThd = Start_Kernel_Thread(&a

16、mp;EchoCou nt, 0 , PRIORITY_NORMAL, false);/* Now this thread is done. */Exit(O);GeekOS设计项目1：Elf.c文件： #i nclude <geekos/err no .h> #in clude <geekos/kassert.h> #i nclude <geekos/ktypes.h>#i nclude vgeekos/scree n.h> /* for debug Prin t() stateme nts */#in clude <geekos/pfat.h

17、>#i nclude <geekos/malloc.h>#include <geekos/string.h>#include <geekos/elf.h>/* From the data of an ELF executable, determ ine how its segme nts* n eed to be loaded into memory.* param exeFileData buffer containing the executable file* param exeFileLength length of the executabl

18、e file in bytes* param exeFormat structure describ ing the executable's segme nts* and entry address; to be filled in* retur n 0 if successful, < 0 on error*/int Parse_ELF_Executable(char *exeFileData, ulong_t exeFileLe ngth, struct Exe_Format *exeFormat) _/* TODO("Parse an ELF executabl

19、e image");*/int i;elfHeader *head=(elfHeader*)exeFileData;programHeader*proHeader=(programHeader*)(exeFileData+head->phoff);KASSERT(exeFileData!=NULL);KASSERT(exeFileLe ngth>head->ehsize+head->phe ntsize*head->ph nu m); KASSERT(head->e ntry%4=0);exeFormat- >nu mSegme nts=he

20、ad->ph num;exeFormat->e ntryAddr=head->e ntry;for(i=0;i<head->ph nu m;i+)exeFormat->segme ntListi.offset InF ile=proHeader->offset;exeFormat->segme ntListi .len gthI nF ile=proHeader->fileSize;exeFormat->segme ntListi.startAddress=proHeader->vaddr;exeFormat->segme

21、 ntListi.size In Memory=proHeader->memSize;exeFormat->segme ntLtFlags=proHeader->flags;proHeader+;return 0;GeekOS设计项目2：Src/GeekOS/user.c 文件中的函数 Spawn()：int Spawn(const char *program, const char *command, struct Kernel_Thread*pThread)/* Hi nts:* - Call Read_Fully() to load the en tir

22、e executable into a memory buffer* - Call Parse_ELF_Executable() to verify that the executable is* valid, and to populate an Exe_Format data structure describ ing* how the executable should be loaded* - Call Load_User_Program() to create a User_C on text with the loaded* program* - Call Start_User_T

23、hread() with the new User_Co ntext* If all goes well, store the pointer to the new thread in* pThread and return 0. Otherwise, return an error code. */int rc;char *exeFileData = 0;ulong_t exeFileLe ngth;struct User_C on text *userC on text = 0;struct Kern el_Thread *process = 0;struct Exe_Format exe

24、Format;/* Load the executable file data, parse ELF headers,* and load code and data segme nts into user memory.*/if(rc = Read_Fully(program, (void*) &exeFileData,& exeFileLe ngth) != 0 |(rc= Parse_ELF_Executable(exeFileData,exeFileLe ngth,& exeFormat) != 0 |(rc = Load_User_Program(exeFil

25、eData, exeFileLe ngth, &exeFormat, comma nd, &userC on text) != 0)goto fail;/* User program has bee n loaded, so we can free the* executable file data now.*/Free(exeFileData);exeFileData = 0;/* Start the process! */process = Start_User_Thread(userC on text, false); if (process != 0) KASSERT(

26、process->refCou nt = 2);/* Retur n Kern el_Thread poin ter */*pThread = process; elserc = ENOMEM;return rc;fail:if (exeFileData != 0)Free(exeFileData);if (userCo ntext != 0)Destroy_User_C on text(userC on text);return rc;structuserSrc/GeekOS/user.c 文件中的函数 Switch_To_User_C on text (): voidSwitch_T

27、o_User_C on text(structKern el_Thread*kthread,In terrupt_State* state) _/* Hint: Before executi ng in user mode, you will n eed to call* the Set_Kernel_Stack_Poi nter() and Switch_To_Address_Space()* functions.*/static structUser_C on text* s_curre ntUserC on text;/* lastcon text used */struct User_

28、C on text* userC on text = kthread->userC on text;/* FIXME: could avoid resetting ss0/esp0 if not returning* to user space.*/KASSERT(!I nterrupts_E nabled();if (userC on text = 0) /* Kernel mode thread: no n eed to switch address space. */ return;/* Switch only if the user con text is in deed dif

29、fere nt */if (userC on text != s_curre ntUserC on text) ulong_t esp0;/* Switch to address space of user con text */ Switch_To_Address_Space(userC on text);/* By definition, when returning to user mode there is no* con text remai ning on the kernel stack.*/esp0 = (ulo ng_t) kthread->stackPage) + P

30、AGE_SIZE;/* Change to the kernel stack of the new process. */ Set_Kernel_Stack_Poi nter(espO);/* New user con text is active */ s_curre ntUserC on text = userC on text; _src/GeekOS/elf.c 文件中的函数 Parse_ELF_Executable ():int Parse_ELF_Executable(char *exeFileData, ulong_t exeFileLe ngth, struct Exe_For

31、mat *exeFormat) _elfHeader *hdr;programHeader *phdr;int i;hdr = (elfHeader *) exeFileData;/* FIXME: when checking offsets, we really ought to be* check ing overflow cases. Need to use fun cti ons from* ran ge.h (which n eeds to be impleme nted, too)*/if (exeFileLe ngth < sizeof(elfHeader) | strnc

32、mp(exeFileData, "x7F""ELF", 4) != 0) if (elfDebug) Print("Not an ELF executablen"); return ENOEXEC;if (hdr->ph num > EXE_MAX_SEGMENTS) if (elfDebug) Prin t("Too man ysegme nts (%d) in ELFexecutablen", hdr->ph nu m);return ENOEXEC;if(exeFileLe ngth<

33、 hdr->phoff +(hdr->ph num*sizeof(programHeader) if (elfDebug) Prin t("Not eno ugh room for program header n"); return ENOEXEC;exeFormat- >nu mSegme nts = hdr->ph num;exeFormat->e ntryAddr = hdr->e ntry;phdr = (programHeader *) (exeFileData + hdr->phoff);for (i = 0; i &

34、lt; hdr->ph num; +i) struct Exe_Segme nt *segme nt = &exeFormat->segme ntListi;/* Fill in segme nt offset, le ngth, address* FIXME: should check that segme nts are valid*/segme nt->offset InF ile = phdri.offset;segme nt->le ngthl nF ile = phdri.fileSize;segme nt->startAddress = ph

35、dri.vaddr; segme nt->size In Memory = phdri.memSize;if (segme nt->le ngthl nF ile > segme nt->sizel nM emory) if(elfDebug) Print("Segment %d: length in file (%lu) exceedssize in memory (%lu)n",i, segment->lengthlnFile, segment->sizelnMemory); return ENOEXEC;/* Groovy */re

36、turn 0; src/GeekOS/userseg.c 文件中的函数 Destroy_User_Context () void Destroy_User_C on text(struct User_C on text* userC on text) 一/* Hi nts:* - you n eed to free the memory allocated for the user process* - don't forget to free the segme nt descriptor allocated* for the process's LDT*/ TODO(&qu

37、ot;Destroy a User_Co ntext");/* Free the con text's LDT descriptor */Free_Segme nt_Descriptor(userC on text->ldtDescriptor); userC on text->ldtDescriptor=0;/* Free the con text's memory */Free(userC on text->memory);userC on text->memory=0;Free(userC on text);userC on text=0

38、; src/GeekOS/userseg.c 文件中的函数 Load_User_Program() int Load_User_Program(char *exeFileData, ulong_t exeFileLe ngth, struct Exe_Format *exeFormat, const char *comma nd, struct User_C on text *pUserC on text) _/* Hi nts:* - Determine where in memoryeach executable segment will be placed* - Determine si

39、ze of argument block and where it memory it will* be placed* - Copy each executable segme nt into memory* - Format argume nt block in memory* - In the created User_C on text object, set code entry point* address, argument block address, and initial kernel stack poi nter* address*/int i;ulong_t maxva

40、 = 0;un sig ned nu mArgs;ulong_t argBlockSize;ulong_t size, argBlockAddr;struct User_C on text *userC on text = 0;/* Find maximum virtual address */for (i = 0; i < exeFormat- >nu mSegme nts; +i) struct Exe_Segme nt *segme nt = &exeFormat->segme ntListi; ulong_t topva = segme nt->star

41、tAddress + segme nt->sizel nM emory;/* FIXME: range check */if (topva > maxva)maxva = topva;/* Determi ne size required for argume nt block */Get_Argume nt_Block_Size(comma nd, &nu mArgs, & argBlockSize);/* Now we can determ ine the size of the memory block n eeded* to run the process.

42、*/size = Roun d_Up_To_Page(maxva) + DEFAULT_USER_STACK_SIZE; argBlockAddr = size;size += argBlockSize;/* Create User_C on text */userC on text = Create_User_C on text(size);if (userC on text = 0)return -1;/* Load segme nt data into memory */for (i = 0; i < exeFormat- >nu mSegme nts; +i) struct

43、 Exe_Segme nt *segme nt = &exeFormat->segme ntListi;memcpy(userC on text->memory + segme nt->startAddress, exeFileData + segme nt->offsetl nF ile, segme nt->le ngthl nFile);/* Format argume nt block */Format_Argume nt_Block(userC on text->memory+ argBlockAddr, nu mArgs,argBlock

44、Addr, comma nd);/* Fill in code entry point */userC on text->e ntryAddr = exeFormat->e ntryAddr;/* Fill in addresses of argume nt block and stack* (They happe n to be the same)*/userCo ntext->argBlockAddr = argBlockAddr;userCo ntext->stackPoi nterAddr = argBlockAddr;*pUserC on text = use

45、rC on text;return 0;src/GeekOS/kthread.c 文件中的函数 Setup_User_Thread() void Setup_User_Thread(struct Kern el_Thread* kthread, struct User_C on text* userC on text) 一 一/* Hi nts:* - Call Attach_User_C on text() to attach the user con text* to the Kern el_Thread* - Set up initial thread stack to make it

46、appear that* the thread was in terrupted while in user mode* just before the entry point in structi on was executed* - The esi register should contain the address of* the argume nt block*/* In terrupts in user mode MUST be en abled.* All other EFLAGS bits will be clear.*/ulo ng_t eflags = EFLAGS_IF;

47、un sig ned csSelector = userC on text->csSelector;un sig ned dsSelector = userC on text->dsSelector;Attach_User_C on text(kthread, userC on text);/* Make the thread's stack look like it was in terrupted* while in user mode.*/* Stack segme nt and stack poin ter with in user mode. */Push(kth

48、read, dsSelector); /* user ss */Push(kthread, userC on text->stackPoi nterAddr); /* user esp */* eflags, cs, eip */Push(kthread, eflags);Push(kthread, csSelector);Push(kthread, userC on text->e ntryAddr);Print("Entry addr=%lxn", userContext->entryAddr);/* Push fake error code and

49、interrupt number. */Push(kthread, 0);Push(kthread, 0);/* Push in itial values for gen eral-purpose registers.* The on ly importa nt register is esi, which we use to* pass the address of the argume nt block.*/Push(kthread, 0); /* eax */Push(kthread, 0); /* ebx */Push(kthread, 0); /* edx */Push(kthrea

50、d, 0); /* edx */Push(kthread, userCo ntext->argBlockAddr); /* esi */Push(kthread, 0); /* edi */Push(kthread, 0); /* ebp */* Push in itial values for the data segme nt registers. */Push(kthread, dsSelector); /* ds */Push(kthread, dsSelector); /* es */Push(kthread, dsSelector); /* fs */Push(kthread

51、, dsSelector); /* gs */src/GeekOS/kthread.c 文件中的函数 Start_User_Thread()struct Kern el_Thread*Start_User_Thread(struct User_C on text* userC on text, bool detached) 一/* Hi nts:* - Use Create_Thread() to create a new "raw" thread object* - Call Setup_User_Thread() to get the thread ready to*

52、execute in user mode* - Call Make_R unn able_Atomic() to schedule the process* for executi on*/struct Kernel_Thread* kthread = Create_Thread(PRIORITY_USER, detached);if (kthread != 0) /* Set up the thread, and put it on the run queue */ Setup_User_Thread(kthread, userC on text); Make_Ru nn able_Atom

53、ic(kthread); 一 一return kthread;src/GeekOS/Syscall.c 文件：#i nclude <geekos/syscall.h>#i nclude <geekos/err no .h>#i nclude <geekos/kthread.h>#in clude <geekos/i nt.h>#include <geekos/elf.h>#i nclude <geekos/malloc.h>#i nclude <geekos/scree n.h>#i nclude <ge

54、ekos/keyboard.h>#include <geekos/string.h>#in clude <geekos/user.h>#i nclude <geekos/timer.h>#i nclude <geekos/vfs.h>/* Allocate a buffer for a user stri ng, and* copy it into kernel space.* In terrupts must be disabled.*/maxLe n,static int Copy_User_String(ulong_tuaddr, u

55、long_t len, ulong_tchar *pStr)int rc = 0;char *str;/* En sure that stri ng isn't too long. */if (le n > maxLe n)return EINVALID;/* Allocate space for the string. */ str = (char*) Malloc(le n+1);if (str = 0) rc = ENOMEM;goto done;/* Copy data from user space. */if (!Copy_From_User(str, uaddr,

56、le n) rc = EINVALID;Free(str);goto done;strle n = '0'/* Success! */*pStr = str;done:return rc;/* Null system call.* Does no thi ng except immediately retur n con trol back* to the in terrupted user program.* Params:* state - processor registers from user mode* Returns:* always returns the va

57、lue 0 (zero)*/static int Sys_Null(struct In terrupt_State* state) 一 一return 0;/* Exit system call.* The in terrupted user process is term in ated.* Params:* state->ebx - process exit code* Returns:* Never retur ns to user mode!*/static int Sys_Exit(struct Interrupt_State* state)Exit(state->ebx);/* Print a stri ng to the con sole.* Params:* state->ebx - user poin ter of stri ng to be prin ted* state->ecx - nu mber of characters to print* Retur ns: 0 if successful, -1 if not*/static int Sys_Pri ntStri ng(struct In terrupt_State* state) 一 一int rc = 0;ui nt_t len