##跟踪地址翻译过程首先把test.c程序写好 ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517627064152-wm) 编译好内核，接着把test.c程序复制到linux0.11中输入```./dbg-asm``` ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517627937838-wm) 输入c运行，编译运行，打印出如下信息 ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517628180807-wm) 单步运行至出现cmp，输入```u/7```反汇编7条汇编语句 ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517629523780-wm) 用```sreg```命令 ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517629932453-wm) 可以看到ldtr的值是0x0068=0000000001101000（二进制），表示LDT表存放在GDT表的1101(二进制)=13（十进制）号位置（每位数据的意义参考后文叙述的段选择子）。而GDT的位置已经由gdtr明确给出，在物理地址的0x00005cb8。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 ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517630035737-wm) GDT表中的每一项占64位（8个字节），所以我们要查找的项的地址是“0x00005cb8 + 13*8” ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517630767458-wm) 重新组合之后得到“0x00fd52d0”输入```xp /8w 0x00fd52d0```，得到ldt表前4项 ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517631194746-wm) 看ds选择子的内容，用```sreg```命令 ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517631366877-wm) 输入```calc ds:0x3004```，与推论一致 ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517631816894-wm) 输入```creg```命令，得到如下图 ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517631963392-wm) 用```xp /68w 0``` 查看内容 ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517632028773-wm) 经过一顿推断查找 ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517632509101-wm) 可知0x00fa6004为其物理地址，输入命令```xp /w 0x00fa6004``` ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517633219019-wm) 现在，通过直接修改内存来改变i的值为0，命令是： ```setpmem 0x00fa6004 4 0```，表示从0x00fa7004地址开始的4个字节都设为0。然后再用“c”命令继续Bochs的运行，可以看到test退出了，说明i的修改成功了，此项实验结束。 ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517633387322-wm) ##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; } ``` 输入命令```gcc -o producer producer.c -lpthread```和```gcc -o consumer consumer.c -lpthread```编译，输入下列指令运行即得到输出 ``` # ./producer & # ./consumer ``` ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517669087935-wm) ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517668923273-wm) 运行正常 ##在linux 0.11实现基于共享内存的生产者消费者再一次进行信号量实验的套路 ###unistd.h ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517741026761-wm) ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517740998058-wm) ###sys.h ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517736751042-wm) ###system_call.s ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517736827943-wm) ###sem.c 略 ###shm.c ``` #define __LIBRARY__ #include #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); } ``` ###Makefile ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517738816336-wm) ###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; } ``` ###producer.c 因输出问题，此处把producer的输出删去 ``` /*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 ``` ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517742621214-wm) 输入```sudo less hdc/usr/root/output```查看 ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517742928135-wm) ![实验楼](https://dn-simplecloud.shiyanlou.com/5633351517742943651-wm) 正常输出，实验结束 ##实验问题 ####1. 对于地址映射实验部分，列出你认为最重要的那几步（不超过4步），并给出你获得的实验数据。略 ####2. test.c退出后，如果马上再运行一次，并再进行地址跟踪，你发现有哪些异同？为什么？得到的i的物理地址可能会不同。在linux0.11中，因为有虚拟内存和段页结合的内存管理机制，get_free_page()在物理页框中找出空闲页是很随意的一一一只要是空闲的页框就直接拿来用。而test.exe重启后，其各个段在上一次执行时使用的物理页框很可能已经被其他进程占用了。所以这一次其data段有可能会被分配到别的物理页框中去。所以得到的i的物理地址可能会不同。

“操作系统原理与实践”实验报告