计算机操作系统实验_运行用户态程序

1、西北工业大学操作系统实验实验报告一、实验目的掌握在GeekOS系统用户态模式下加载并运行可执行程序的方法。二、实验要求1.按照实验讲义P127页中的设计要求，实现在用户态模式下加载并运行可 执行程序的代码，给出关键函数的代码以与实验结果。三、实验过程与结果答：核心函数代码如下：= user.c =/产生一个进程用户态int Spaw n(const char *program, const char *ma nd, struct Kern el_Thread *pThread)TODO(Spaw n a process by read ing an executable from a file

2、system); 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 exeFormat;if (rc = Read_Fully(program, (void*) & exeFileData, & exeFileLe ngth) != 0 )Print(Failed to Read File %s!n, program);goto fail;if(rc =

3、Parse_ELF_Executable(exeFileData, exeFileLe ngth, &exeFormat) != 0 )Prin t(Failed to Parse ELF File!n ”);goto fail;if(rc = Load_User_Program(exeFileData, exeFileLe ngth, &exeFormat, mand, & userC on text) != 0)Prin t(Failed to Load User Program!n);goto fail;/在堆分配方式下释放内存并再次初始化exeFileDataFree(exeFileD

4、ata);exeFileData = 0;/*开始用户进程，调用Start_User_Thread函数创建一个进程并使其进入准备运行队列*/process = Start_User_Thread(userC on text, false);if (process != 0) KASSERT(process-refCou nt = 2);/*返回核心进程的指针*/*pThread = process;rc = process-pid;记录当前进程的IDelserc = ENOMEM;return rc;fail: /如果新进程创建失败如此注销User_Context对象if (exeFileDa

5、ta != 0)Free(exeFileData);/ 释放内存if (userCo ntext != 0)Destroy_User_Context(userContext);/ 销毁进程对象return rc; /切换至用户上下文void Switch_To_User_C on text(structKernel_Thread* kthread, struct In terrupt_State*state)static struct User_C on text* s_curre ntUserC on text; /* last user con text used */exter n in

6、t userDebug;struct User_C on text* userC on text = kthread-userC on text;KASSERT(!I nterrupts_E nabled();if (userCo ntext = 0) /userC on text为0表示此进程为核心态进程就不用切换地址空间return;if (userC on text != s_curre ntUserC on text) ulong_t esp0;/if (userDebug) Prin t(A%pn, kthread);Switch_To_Address_Space(userConte

7、xt);/为用户态进程时如此切换地址空间esp0 = (ulo ng_t) kthread-stackPage) + PAGE_SIZE;/if (userDebug)/ Prin t(S%lxn, esp0);/*新进程的核心栈 */Set_Kernel_Stack_Poi nter(espO);/ 设置内核堆栈指针/* New user con text is active */s_curre ntUserC on text = userC on text;= elf.c =int Parse_ELF_Executable(char *exeFileData, ulong_t exeFil

8、eLength, struct Exe_Format *exeFormat)int i;elfHeader *head=(elfHeader*)exeFileData;programHeader *proHeader=(programHeader *)(exeFileData+head-phoff);KASSERT(exeFileData!=NULL);KASSERT(exeFileLe ngthhead-ehsize+head-phe ntsize*head-ph nu m);KASSERT(head-e ntry%4=0);exeFormat-nu mSegme nts=head-ph n

9、um;exeFormat-e ntryAddr=head-e ntry;for(i=0;iph nu m;i+)exeFormat-segme ntListi.offset InF ile=proHeader-offset;exeFormat-segme ntListien gthI nFile=proHeader-fileSize;exeFormat-segme ntListi.startAddress=proHeader-vaddr;exeFormat-segme ntListi.sizel nM emory=proHeader-memSize;exeFormat-segme ntList

10、tFlags=proHeader-flags;proHeader+;return 0;= userseg.c =需在此文件各函数前增加一个函数，此函数的功能是按给定的大小创建一个用户级进程上下文，具体实现如下：函数功能：按给定的大小创建一个用户级进程上下文static struct User_C on text* Create_User_C on text(u long_t size)struct User_C on text * UserC on text;size = Roun d_Up_To_Page(size);UserCo ntext = (struct User_Co n

11、text *)Malloc(sizeof(struct User_Co ntext);if (UserCo ntext != 0)UserC on text-memory = Malloc(size);/为核心态进程elsegoto fail;内存为空if (0 = UserC on text-memory)goto fail;memset(UserC on text-memory, 0, size);UserC on text-size = size;/以下为用户态进程创建LDT(段描述符表)新建一个LDT描述符UserC on text-ldtDescriptor = Allocate_S

12、egme nt_Descriptor();if (0 = UserC on text-ldtDescriptor)goto fail;/初始化段描述符In it_LDT_Descriptor(UserCo ntext-ldtDescriptor,UserCo ntext-ldt,NUM_USER_LDT_ENTRIES);新建一个LDT选择子UserCo ntext-ldtSelector=Selector(KERNEL_PRIVILEGE,true,Get_Descriptor_I ndex(UserC on text-ldtDescriptor);/新建一个文本段描述符Ini t_Code

13、_Segme nt_Descriptor(& UserCo ntext-ldt0,(ulon g_t) UserC on text-memory,size / PAGE_SIZE,USER_PRIVILEGE);/新建一个数据段Ini t_Data_Segme nt_Descriptor(& UserCo ntext-ldt1,(ulon g_t) UserC on text-memory,size / PAGE_SIZE,USER_PRIVILEGE);/新建数据段和文本段选择子UserC on text-csSelector = Selector(USER_PRIVILEGE, false

14、, 0);UserCo ntext-dsSelector = Selector(USER_PRIVILEGE, false, 1);/将引用数清0UserC on text-refCou nt = 0;retur n UserC on text;fail:if (UserCo ntext != 0)if (UserC on text-memory != 0)Free(UserC on text-memory);Free(UserC on text);return 0; /摧毁用户上下文void Destroy_User_C on text(struct User_C on text* user

15、C on text) TODO(Destroy a User_Co ntext);/释放占用的LDTFree_Segme nt_Descriptor(userC on text-ldtDescriptor);userC on text-ldtDescriptor=0;/释放内存空间Free(userC on text-memory); userC on text-memory=0;/释放userContext本身占用的内存Free(userC on text);userC on text=0;int Load_User_Program(char *exeFileData,u long_texe

16、FileLe ngth,structExe_Format*exeFormat,c onst char *ma nd,struct User_C on text *pUserC on text)TODO(Load a user executable into a user memory space using segme ntati on ”)；int i;ulong_t maxva = 0;/要分配的最大内存空间un sig ned nu mArgs;/ 进程数目ulong_t argBlockSize;/ 参数块的大小ulong_t size, argBlockAddr;/ 参数块地址str

17、uct User_C on text *userC on text = 0;/计算用户态进程所需的最大内存空间for (i = 0; i nu mSegme nts; +i) struct Exe_Segme nt *segme nt = & exeFormat-segme ntListi;ulong_t topva = segme nt-startAddress + segme nt-sizel nM emory; /* FIXME: range check */if (topva maxva)maxva = topva;Get_Argume nt_Block_Size(ma nd, &nu

18、 mArgs, &argBlockSize); 获取参数块信息size = Round_ Up_To_Page(maxva) + DEFAULT_USER_STACK_SIZE;argBlockAddr = size;size += argBlockSize;userContext = Create_User_Context(size);/ 按相应大小创建一个进程if (userContext = 0)/如果为核心态进程return -1;for (i = 0; i nu mSegme nts; +i) struct Exe_Segme nt *segme nt = & exeFormat-s

19、egme ntListi;/根据段信息将用户程序中的各段内容复制到分配的用户内存空间memcpy(userC on text-memory+segme nt-startAddress,exeFileData +segme nt-offsetl nFile,segme nt-le ngthl nFile);/格式化参数块Format_Argume nt_Block(userC on text-memory+ argBlockAddr, nu mArgs, argBlockAddr,man d);/初始化数据段，堆栈段与代码段信息userC on text-e ntryAddr = exeForm

20、at-e ntryAddr;userC on text-argBlockAddr = argBlockAddr;userC on text-stackPoi nterAddr = argBlockAddr;将初始化完毕的 User_Context赋给*pUserContext *pUserC on text = userC on text;return 0;/ 成功 /将用户态的进程复制到内核缓冲区bool Copy_From_User(void* dest InKern el, ulong_t srcInU ser, ulong_t bufSize) struct User_C on tex

21、t * UserC on text = g_curre ntThread-userC on text;/-: check if memory if validatedif (!Validate_User_Memory(UserCo ntext,srcl nU ser, bufSize)return false;memcpy(destl nKern el, UserC on text-memory + srcInU ser, bufSize);return true; /将内核态的进程复制到用户态bool Copy_To_User(u long_t destl nU ser, void* src

22、InKern el, ulong_t bufSize) struct User_C on text * UserC on text = g_curre ntThread-userC on text;if (!Validate_User_Memory(UserCo ntext, destI nU ser,bufSize)return false;memcpy(UserC on text-memory + destI nU ser, srcInKern el, bufSize); return true; /切换到用户地址空间void Switch_To_Address_Space(struct

23、User_C on text *userC on text)ushort_t ldtSelector= userC on text-ldtSelector;/* Switch to the LDT of the new user con text */_asmvolatile_ (lldt %0:a(ldtSelector);= kthread.c =添加头文件 #i nclude /创建一个用户进程/*static*/ void Setup_User_Thread(struct Kern el_Thread* kthread, struct User_C on text* userC on

24、text)ulo ng_t eflags = EFLAGS_IF;unsigned csSelector=userContext-csSelector;/CS 选择子unsigned dsSelector=userContext-dsSelector;/DS 选择子Attach_User_C on text(kthread, userC on text);初始化用户态进程堆栈，使之看上去像刚被中断运行一样分别调用Push函数将以下数据压入堆栈Push (kthread, dsSelector);Push(kthread, userC on text-stackPo in terAddr);Pu

25、sh(kthread, eflags);Push(kthread, csSelector);Push(kthread, userC on text-e ntryAddr);Push (kthread, 0);Push (kthread, 0);/数据选择子堆栈指针/Eflags文本选择子/程序计数器错误代码(0)中断号(0)/初始化通用存放单元，将ESI用户传递参数块地址Push(kthread, 0); /* eax */Push(kthread, 0); /* ebx */Push(kthread, 0); /* edx */Push(kthread, 0); /* edx */Push(

26、kthread, userC on text-argBlockAddr); /* esi */Push(kthread, 0); /* edi */Push(kthread, 0); /* ebp */初始化数据段存放单元Push(kthread, dsSelector); /* ds */Push(kthread, dsSelector); /* es */Push(kthread, dsSelector); /* fs */Push(kthread, dsSelector); /* gs */开始用户进程struct Kern el_Thread* Start_User_Thread(st

27、ruct User_C on text* userC on text, bool detached) struct Kernel_Thread* kthread = Create_Thread(PRIORITY_USER, detached);if (kthread != 0)Setup_User_Thread(kthread, userC on text);Make_Ru nn able_Atomic(kthread);return kthread;syscall.c/需在此文件别的函数前增加一个函数，函数名为Copy_User_String ，它被函数Sys_PrintString调用，具

28、体实现如下：static int Copy_User_Stri ng(u long_t uaddr, ulon g_t le n, ulong_t maxLe n, char *pStr) int rc = 0;char *str;if (le n maxLe n)/超过最大长度return EINV ALID;str = (char*) Malloc(le n+1);/ 为字符串分配空间if (0 = str)rc = ENOMEM;goto fail;if (!Copy_From_User(str, uaddr, le n)从用户空间中复制数据rc = EINV ALID;Free(str

29、);goto fail;strle n = 0：/成功*pStr = str;fail:return rc; static int Sys_Exit(struct Interrupt_State* state) Exit(state-ebx); static int Sys_PrintString(struct Interrupt_State* state)int rc = 0;/ 返回值uint_t length = state-ecx;/ 字符串长度uchar_t* buf = 0;if (le ngth 0) if (rc = Copy_User_String(state-ebx, le

30、ngth, 1023, (char*) &buf) != 0) goto done;Put_Buf(buf, le ngth);done:if (buf != 0)Free(buf);return rc; static int Sys_GetKey(struct Interrupt_State* state)return Wait_For_Key(); / 返回按键码 keyboard.c/Wait_For_Key() static int Sys_SetAttr(struct In terrupt_State* state) Set_Curre nt_Attr(uchar_t) state-

31、ebx); return 0; static int Sys_GetCursor(struct Interrupt_State* state)int row, col;Get_Cursor(&row, & col);if (!Copy_To_User(state-ebx, &row, sizeof( in t) |!Copy_To_User(state-ecx, &col, sizeof( in t) return -1;return 0; static int Sys_PutCursor(struct Interrupt_State* state) retur n Put_Cursor(st

32、ate-ebx, state-ecx) ? 0 : -1; static int Sys_Spaw n( struct In terrupt_State* state)int rc;/函数返回值char *program = 0;进程名称char *ma nd = 0;/ 用户命令struct Kern el_Thread *process;if (rc = Copy_User_Stri ng(state-ebx, state-ecx, VFS_MAX_PATH_LEN, & program) != 0) goto fail;if(rc = Copy_User_Stri ng(state-ed

33、x, state-esi, 1023, &man d) != 0)/从用户空间复制用户命令goto fail;En able_I nterrupts();/ 开中断rc = Spawn(program, mand, &process);/得到进程名称和用户命令后便可生成一个新进程if (rc = 0) /假如成功如此返回新进程 ID号KASSERT(process != 0);rc = process-pid;Disable_Interrupts();/ 关中断if (program != 0) Free(program);if (ma nd != 0)Free(ma nd); return

34、rc; static int Sys_Wait(struct Interrupt_State* state) /TODO(Wait system call);int exitCode;struct Kernel_Thread *kthread = Lookup_Thread(state-ebx); if (kthread = 0)return -12;En able_I nterrupts();exitCode = Join( kthread);Disable_I nterrupts();retur n exitCode; static int Sys_GetPID(struct Interr

35、upt_State* state) /TODO(GetPID system call);retur n g_curre ntThread-pid;= main.c = static void Spaw n_lni t_Process(void) /TODO(Spaw n the in it process);struct Kernel_Thread *pThread;Spaw n(”/c/shell.exe,/c/shell.exe,&pThread);实验结果如下列图:C Q dcKhs xB6 emulator, http:;/bochs.sourceforgcnetit- .| | ji

36、iTsijiirercWiSrfcgI ist 1G48E7G bytes in kernEi Jheapkry br)Ard .DHA Caintpoller.-. Cloppy contro1ier.06, hcods2, sectors 18IEE duh tibuller.1333313333 H |jlL,frZl. . FI7TTk35 *|蹿% 廉逊缓空,5.航*通耳百ij原理：Geekos提供了一个简单的shell,保存在PFAT文件系统内，所以geekos系统启动后，启动shell程序/c/shell.exe运行，将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。运行后，geekos就可以挂在这shell，并能运行测试文件c.exe和b.exeo四、实验分析GeekOS系统最早创建的内核进程有Idle、Reaper和Main三个进程，它们 由Ini t