#跟踪地址翻译过程: ##实验环境准备 1.源文件拷贝 ``` cd ~/oslab cp -r /home/teacher/oslab/* ./ ``` 2.编译Linux-0.11 ``` make all ``` 3.挂载hdc ``` sudo ./mount-hdc ``` 4.在usr/root下添加test.c文件用来测试地址映射 ``` #include int i = 0x12345678; int main(void) { printf("The logical/virtual address of i is 0x%08x", &i); fflush(stdout); while (i) ; return 0; } ``` ##调试Linux-0.11 ###准备编译好 Linux 0.11 后，首先通过运行 ./dbg-asm 启动调试器，此时 Bochs 的窗口处于黑屏状态 ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210515-1621037013236) 直接输入命令 c，continue 程序的运行，Bochs 启动了 Linux 0.11。![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210515-1621037308820) 编译并运行test.c ``` gcc -o test test.c ./test ``` 打印如下信息： ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210515-1621037402343) 只要 test 不变，0x00003004 这个值在任何人的机器上都是一样的。即使在同一个机器上多次运行 test，也是一样的。 test 是一个死循环，只会不停占用 CPU，不会退出。 ###暂停切换到ubuntu终端，按下Ctrl+c暂停bochs。如果中断在内核中，就c，然后再 ctrl+c，直到变为 000f 为止。![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210515-1621038155902)如果显示的下一条指令不是 cmp ...（这里指语句以 cmp 开头），就用 n 命令单步运行几步，直到停在 cmp ...。![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210515-1621038201477) 使用命令 u /8，显示从当前位置开始 8 条指令的反汇编代码，结构如下：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210515-1621038318659) ##开始寻找 ds:0x3004 对应的物理地址。到ubuntu终端，输入sreg命令 ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210515-1621043866385) 用 xp /32w 0x00005cb8 查看从该地址开始，32 个字的内容，及 GDT 表的前 16 项，如下： ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210515-1621043903909) 输入 ``` xp /2w 0x00005cb8+13*8 ``` 得到： ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210515-1621044028036) 输入 ``` xp /8w 0x00fd52d0 ``` 得到： ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210518-1621349554782) ##段描述符看看 ds 选择子的内容，还是用 sreg 命令可以看到ds的值是0x0017，段选择子是一个16位寄存器，它的各位的函数如下: ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210518-1621349844890) ##段地址段基址，即段描述符0x0**0000** 3fff 0x**10**c0f3**00** 中加粗部分组合而成的 0x10000000，段基址 + 段内偏移 = 线性地址 0x10000000 + 0x3004 = 0x10003004 用命令验证线性地址是不是对的: ``` calc ds:0x3004 ``` ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210518-1621350126794) 发现是对的，当前已经找到了该进程在虚拟内存中的线性地址了，然后需要找物理地址 ##物理地址 ###页表从线性地址计算物理地址，需要查找页表，线性地址翻译成物理地址的过程如下: ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210518-1621350298745) 首先需要找出页目录号 + 页表号 + 页内偏移，它们分别对应了32位线性地址10位 + 10位 + 12位，所以0x10003004的页目录号=64,页号=3,页内偏移=4。在IA-32(英特尔的32位CPU架构)下，页目录表的位置由CR3寄存器指引，用creg命令 ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210518-1621350733950) 说明页目录表的基址为0，看看其内容用命令: ``` xp /68w 0 ``` ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210518-1621350793686) 页目录表和页表中的内容很简单，是1024个32位数，这32位中前20位是物理页框号，后面是一些属性信息(最重要的是最后一位P)，其中第65个页目录项就是要找的内容，用命令查看: ``` xp /w 0 + 64*4 ``` ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210518-1621350885694) 其中的027是属性，显然P=1，这里还也可以分析出其它的属性。页表所在的物理页框号为0x00fa7，即页表在物理内存为0x00fa7000处，从该位置开始查找3号页表项(每个页表项4个字节)，用命令: ``` xp /w 0x00fa7000 + 3*4 ``` ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210518-1621351205962) 其中的067是属性，显然P=1。 **物理地址** 线性地址0x10003004对应的物理页框号为0x00fa6，和页内偏移0x004接到一起，得到0x00fa6004，这就是变量i的物理地址，可以通过两种方法验证: 1.用命令: page 0x10003004，可以得到信息:“linear page 0x10003000 maps to physical page 0x00fa6000”。 2.用命令: xp /w 0x00fa6004: ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210518-1621351854531) 直接修改物理地址的值，使得变量i为0 命令: setpmem 0x00fa6004 4 0(表示从0x00fa6004地址开始设置4个字节都为0) 然后输入命令c(如上)，继续从调试状态的程序运行下去 ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210518-1621351961436) 就会看到在Bochs中程序顺利退出: ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210518-1621351974580) 到这里第一个部分也正式完成了 #在Ubuntu下实现基于共享内存的生产者—消费者程序 ##编写producer.c和consumer.c ``` /*producer.c*/ #include #include #include #include #include #include #include #define PRODUCE_NUM 200 #define BUFFER_SIZE 10 #define SHM_KEY 2018 int main(int argc, char* argv[]) { sem_t *Empty,*Full,*Mutex; int i, shm_id, location=0; int *p; Empty = sem_open("Empty",O_CREAT,0600,BUFFER_SIZE); Full = sem_open("Full", O_CREAT,0600, 0); Mutex = sem_open("Mutex",O_CREAT,0600, 1); if((shm_id = shmget(SHM_KEY, BUFFER_SIZE*sizeof(int), IPC_CREAT|0666)) == -1) printf("shmget failed!"); if((p = (int * )shmat(shm_id, NULL, 0)) == -1) printf("shmat error!"); for(i=0; i #include #include #include #include #include #include #define PRODUCE_NUM 200 #define BUFFER_SIZE 10 #define SHM_KEY 2018 int main(int argc, char* argv[]) { sem_t *Empty,*Full,*Mutex; int used, shm_id,location = 0; int *p; Empty = sem_open("Empty", O_CREAT,0600,BUFFER_SIZE); Full = sem_open("Full", O_CREAT,0600, 0); Mutex = sem_open("Mutex", O_CREAT,0600, 1); if((shm_id = shmget(SHM_KEY, BUFFER_SIZE*sizeof(int), IPC_CREAT|0666)) == -1) printf("shmget failed!\n"); if((p = (int * )shmat(shm_id, NULL, 0)) == -1) printf("link error!\n"); while(1) { sem_wait(Full); sem_wait(Mutex); printf("pid %d:\tconsumer consumes item %d\n", getpid(), p[location]); fflush(stdout); sem_post(Mutex); sem_post(Empty); location = (location+1) % BUFFER_SIZE; if(++used == PRODUCE_NUM) break; } if(shmdt(p) == -1) printf("csm shmdt error.\n"); if(shmctl(shm_id,IPC_RMID,NULL) == -1) printf("shmctl error.\n"); sem_unlink("Mutex"); sem_unlink("Full"); sem_unlink("Empty"); return 0; } ``` ##编译运行输入命令 ``` gcc -o producer producer.c -lpthread gcc -o consumer consumer.c -lpthread ``` 运行，输入下列指令运行即得到输出 ``` ./producer & ./consumer ``` ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210519-1621415589203) #基于共享内存的生产者-消费者程序: ##实验环境准备 1.源文件拷贝 ``` cd ~/oslab cp -r /home/teacher/oslab/* ./ ``` ##在Linux-0.11中实现共享内存 ###1.修改unistd.h ``` /* add */ #include /* end */ /* add */ #define __NR_sem_open 72 #define __NR_sem_wait 73 #define __NR_sem_post 74 #define __NR_sem_unlink 75 #define __NR_shmget 76 #define __NR_shmat 77 /* end */ ``` ``` #define SHM_SIZE 64 typedef struct shm_ds { unsigned int key; unsigned int size; unsigned long page; }shm_ds; int sys_shmget(unsigned int key,size_t size); void * sys_shmat(int shmid); ``` ###2.新建sem.h ``` #ifndef _SEM_H #define _SEM_H /* include task_struct */ #include #define NAME_SIZE 10 typedef struct { char name[NAME_SIZE]; unsigned int value; struct task_struct *wait; char used; } sem_t; #endif ``` ###3.修改system_call.s ``` nr_system_calls = 78 ``` ###4.修改sys.h ``` extern int sys_sem_open(); extern int sys_sem_wait(); extern int sys_sem_post(); extern int sys_sem_unlink(); extern int sys_shmget(); extern int sys_shmat(); fn_ptr sys_call_table[] = { sys_setup, sys_exit, sys_fork, sys_read, sys_write, sys_open, sys_close, sys_waitpid, sys_creat, sys_link, sys_unlink, sys_execve, sys_chdir, sys_time, sys_mknod, sys_chmod, sys_chown, sys_break, sys_stat, sys_lseek, sys_getpid, sys_mount, sys_umount, sys_setuid, sys_getuid, sys_stime, sys_ptrace, sys_alarm, sys_fstat, sys_pause, sys_utime, sys_stty, sys_gtty, sys_access, sys_nice, sys_ftime, sys_sync, sys_kill, sys_rename, sys_mkdir, sys_rmdir, sys_dup, sys_pipe, sys_times, sys_prof, sys_brk, sys_setgid, sys_getgid, sys_signal, sys_geteuid, sys_getegid, sys_acct, sys_phys, sys_lock, sys_ioctl, sys_fcntl, sys_mpx, sys_setpgid, sys_ulimit, sys_uname, sys_umask, sys_chroot, sys_ustat, sys_dup2, sys_getppid, sys_getpgrp, sys_setsid, sys_sigaction, sys_sgetmask, sys_ssetmask, sys_setreuid, sys_setregid, sys_sem_open, sys_sem_wait, sys_sem_post, sys_sem_unlink, sys_shmget,sys_shmat }; ``` ###5.新增sem.c 和shm.c ``` #include #include /* include get_fs_byte() */ #include /* include NULL */ #include /* include cli() sti() */ #include /* include prknik() */ #include #define KSEM_SIZE 5 sem_t ksem[KSEM_SIZE] = {{{'0', }, 0, NULL, 0}, {{'\0', }, 0, NULL, 0}, {{'0', }, 0, NULL, 0}, {{'0', }, 0, NULL, 0}, {{'0', }, 0, NULL, 0}}; char buf[NAME_SIZE]; int str_equ(const char * sa,const char * sb) { int i; for (i=0; sa[i] && sb[i]; i++) if (sa[i] != sb[i]) return 0; return 1; } void str_cpy(char * dest,const char * src) { int i; for (i=0; dest[i] = src[i]; i++) ; } sem_t * sys_sem_open(const char *name, unsigned int value) { int i; /* get name */ for (i=0; buf[i] = get_fs_byte(name+i); i++) ; /* return old sem */ for (i=0; ivalue) sleep_on(&sem->wait); sem->value--; sti(); return 0; } int sys_sem_post(sem_t *sem) { cli(); if (!sem->value) wake_up(&sem->wait); sem->value++; sti(); return 0; } int sys_sem_unlink(const char *name) { int i; /* get name */ for (i=0; buf[i] = get_fs_byte(name+i); i++) ; /* try to delete sem */ for (i=0; i #include #include #include #include static shm_ds shm_list[SHM_SIZE] = {{0,0,0}}; int sys_shmget(unsigned int key, size_t size) { int i; void *page; if(size > PAGE_SIZE) return -EINVAL; page = get_free_page(); if(!page) return -ENOMEM; printk("shmget get memory's address is 0x%08x\n",page); for(i=0; ildt[2]); printk("current's data_base = 0x%08x,new page = 0x%08x\n",data_base,shm_list[shmid].page); brk = current->brk + data_base; current->brk += PAGE_SIZE; if(put_page(shm_list[shmid].page, brk) == 0) return (void *)-ENOMEM; return (void *)(current->brk - PAGE_SIZE); } ``` ###6.修改makefile ``` OBJS = sched.o system_call.o traps.o asm.o fork.o \ panic.o printk.o vsprintf.o sys.o exit.o \ signal.o mktime.o sem.o shm.o ``` ###编译 ###挂载hdc 在文件系统中修改include文件中的头文件即修改unistd.h和新增sem.h ###编写consumer.c ``` /*consumer*/ #define __LIBRARY__ #include #include #include #include #include _syscall2(sem_t *,sem_open,const char *,name,int,value); _syscall1(int,sem_post,sem_t *,sem); _syscall1(int,sem_wait,sem_t *,sem); _syscall1(int,sem_unlink,const char*,name); _syscall1(int, shmat, int, shmid); _syscall2(int, shmget, unsigned int, key, size_t, size); #define PRODUCE_NUM 200 #define BUFFER_SIZE 10 #define SHM_KEY 2018 int main(int argc, char* argv[]) { sem_t *Empty,*Full,*Mutex; int used = 0, shm_id,location = 0; int *p; Empty = sem_open("Empty", BUFFER_SIZE); Full = sem_open("Full", 0); Mutex = sem_open("Mutex", 1); if((shm_id = shmget(SHM_KEY, BUFFER_SIZE*sizeof(int))) < 0) printf("shmget failed!\n"); if((p = (int * )shmat(shm_id)) < 0) printf("link error!\n"); while(1) { sem_wait(Full); sem_wait(Mutex); printf("pid %d:\tconsumer consumes item %d\n", getpid(), p[location]); fflush(stdout); sem_post(Mutex); sem_post(Empty); location = (location+1) % BUFFER_SIZE; if(++used == PRODUCE_NUM) break; } sem_unlink("Mutex"); sem_unlink("Full"); sem_unlink("Empty"); return 0; } ``` ###编写producer.c ``` /*producer*/ #define __LIBRARY__ #include #include #include #include #include _syscall2(sem_t *,sem_open,const char *,name,int,value); _syscall1(int,sem_post,sem_t *,sem); _syscall1(int,sem_wait,sem_t *,sem); _syscall1(int, shmat, int, shmid); _syscall2(int, shmget, unsigned int, key, size_t, size); #define PRODUCE_NUM 200 #define BUFFER_SIZE 10 #define SHM_KEY 2018 int main(int argc, char* argv[]) { sem_t *Empty,*Full,*Mutex; int i, shm_id, location=0; int *p; Empty = sem_open("Empty", BUFFER_SIZE); Full = sem_open("Full", 0); Mutex = sem_open("Mutex", 1); if((shm_id = shmget(SHM_KEY, BUFFER_SIZE*sizeof(int))) < 0) printf("shmget failed!"); if((p = (int * )shmat(shm_id)) < 0) printf("shmat error!"); for(i=0; i output & sync ``` ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1692362-20210519-1621415074698)

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