## 一.跟踪地址翻译过程 ![实验楼](https://dn-simplecloud.shiyanlou.com/3193221518877155217-wm) 由图可得线性地址为：0x10000000+0x3004 = 0x10003004，可知页目录索引为256，页表索引为3，页内偏移为4 ![实验楼](https://dn-simplecloud.shiyanlou.com/3193221518877532238-wm) 查页目录表得到页表地址：0x00faa000 ![实验楼](https://dn-simplecloud.shiyanlou.com/3193221518877917029-wm) 查页表得到页地址为：0x00fa7000 ![实验楼](https://dn-simplecloud.shiyanlou.com/3193221518878055794-wm) 看到了变量i所在地址的内容 ![实验楼](https://dn-simplecloud.shiyanlou.com/3193221518878184492-wm) 修改内容为0后，循环退出了 ## 二.基于共享内存的生产者—消费者程序 ### 1.producer.c ``` #include /* constant */ #include #include #include /* constant */ #include /* printf() fflush() */ #include #define BUF_SIZE 10 #define COUNT 500 #define KEY 183 #define SHM_SIZE (BUF_SIZE+1)*sizeof(short) int main(int argc, char** argv) { int pid; unsigned short count = 0; int shm_id; short *shmp; sem_t *empty, *full, *mutex; shm_id = shmget(KEY, SHM_SIZE, IPC_CREAT|0666); if (shm_id == -1) { printf("shmget error\n"); return -1; } /* managed by system, read and write */ shmp = (short*)shmat(shm_id, NULL, 0); /* close old sem */ sem_unlink("empty"); sem_unlink("full"); sem_unlink("mutex"); /* open new sem */ empty = sem_open("empty", O_CREAT|O_EXCL, 0666, 10); full = sem_open("full", O_CREAT|O_EXCL, 0666, 0); mutex = sem_open("mutex", O_CREAT|O_EXCL, 0666, 1); if (empty == SEM_FAILED || full == SEM_FAILED || mutex == SEM_FAILED) printf("sem_open error\n"); pid = syscall(SYS_getpid); while (count <= COUNT) { sem_wait(empty); sem_wait(mutex); printf("Producer 1 process %d : %d\n", pid, count); fflush(stdout); *(shmp++) = count++; if (!(count % BUF_SIZE)) shmp -= 10; sem_post(mutex); sem_post(full); } return 0; } ``` ### 2.consumer.c ``` #include /* constant */ #include #include #include /* printf() fflush() */ #include #define BUF_SIZE 10 #define KEY 183 int main(int argc, char** argv) { int pid; int shm_id; short *shmp, *index; sem_t *empty, *full, *mutex; shm_id = shmget(KEY, 0, 0); if (shm_id == -1) { printf("shmget error\n"); return -1; } /* managed by system, read and write */ shmp = (short*)shmat(shm_id, NULL, 0); index = shmp+BUF_SIZE; *index = 0; /* open old sem */ empty = sem_open("empty", 0); full = sem_open("full", 0); mutex = sem_open("mutex", 0); if (empty == SEM_FAILED || full == SEM_FAILED || mutex == SEM_FAILED) printf("sem_open error\n"); if (!syscall(SYS_fork)) { pid = syscall(SYS_getpid); while (1) { sem_wait(full); sem_wait(mutex); printf("Consumer 1 process %d : %d\n", pid, shmp[*index]); fflush(stdout); if (*index == 9) *index = 0; else (*index)++; sem_post(mutex); sem_post(empty); } return 0; } if (!syscall(SYS_fork)) { pid = syscall(SYS_getpid); while (1) { sem_wait(full); sem_wait(mutex); printf("Consumer 2 process %d : %d\n", pid, shmp[*index]); fflush(stdout); if (*index == 9) *index = 0; else (*index)++; sem_post(mutex); sem_post(empty); } return 0; } pid = syscall(SYS_getpid); while (1) { sem_wait(full); sem_wait(mutex); printf("Consumer 3 process %d : %d\n", pid, shmp[*index]); fflush(stdout); if (*index == 9) *index = 0; else (*index)++; sem_post(mutex); sem_post(empty); } return 0; } ``` ### 3.结果 ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/319322/1518885558817.png-wm) ## 三.共享内存的实现主要是2个系统调用函数，生产者消费者程序在Ubuntu上好像没触发写时复制，在linux上肯定会的，所以需做些调整。 ### 1.shm.c ``` #include /* printk() */ #include #include /* get_free_page() PAGE_SIZE */ #include #include shm_t shms[SHMS_SIZE] = {{0, 0, 0}}; int sys_shmget(key_t key, size_t size) { int i; /* get old shm */ for (i=0; i PAGE_SIZE) return -EINVAL; shms[i].size = size; shms[i].key = key; if (!(shms[i].addr = get_free_page())) return -ENOMEM; return i; } void* sys_shmat(int shmid) { unsigned long logical_addr; if (shmid < 0 || shmid >= SHMS_SIZE) return -EINVAL; logical_addr = current->brk; current->brk += PAGE_SIZE; if (!put_page(shms[shmid].addr, current->start_code+logical_addr)) return -ENOMEM; return (void*)logical_addr; } ``` ### 2.consumer.c ``` #define __LIBRARY__ #include #include #include /* printf() fflush() */ #include _syscall0(int, fork); _syscall0(int, getpid) _syscall2(sem_t *, sem_open, const char *, name, unsigned int, value) _syscall1(int, sem_wait, sem_t *, sem) _syscall1(int, sem_post, sem_t *, sem) _syscall1(int, sem_unlink, const char *, name) _syscall2(int, shmget, key_t, key, size_t, size) _syscall1(void*, shmat, int, shmid) #define BUF_SIZE 10 #define KEY 183 int main(int argc, char** argv) { int pid; int shm_id; short *shmp, *index; sem_t *empty, *full, *mutex; shm_id = shmget(KEY, 0); if (shm_id == -1) { printf("shmget error\n"); return -1; } /* open old sem */ empty = sem_open("empty", 0); full = sem_open("full", 0); mutex = sem_open("mutex", 0); if (empty == -1 || full == -1 || mutex == -1) printf("sem_open error\n"); /* consumer 1 */ if (!fork()) { /* managed by system, read and write */ shmp = (short*)shmat(shm_id); if (shmp == -1) printf("sem_open error\n"); index = shmp+BUF_SIZE; *index = 0; pid = getpid(); while (1) { sem_wait(full); sem_wait(mutex); printf("Consumer 1 process %d : %d\n", pid, shmp[*index]); fflush(stdout); if (*index == BUF_SIZE-1) *index = 0; else (*index)++; sem_post(mutex); sem_post(empty); } return 0; } /* consumer 2 */ if (!fork()) { /* managed by system, read and write */ shmp = (short*)shmat(shm_id); if (shmp == -1) printf("sem_open error\n"); index = shmp+BUF_SIZE; *index = 0; pid = getpid(); while (1) { sem_wait(full); sem_wait(mutex); printf("Consumer 2 process %d : %d\n", pid, shmp[*index]); fflush(stdout); if (*index == BUF_SIZE-1) *index = 0; else (*index)++; sem_post(mutex); sem_post(empty); } return 0; } /* consumer 3 */ /* managed by system, read and write */ shmp = (short*)shmat(shm_id); if (shmp == -1) printf("sem_open error\n"); index = shmp+BUF_SIZE; *index = 0; pid = getpid(); while (1) { sem_wait(full); sem_wait(mutex); printf("Consumer 3 process %d : %d\n", pid, shmp[*index]); fflush(stdout); if (*index == BUF_SIZE-1) *index = 0; else (*index)++; sem_post(mutex); sem_post(empty); } return 0; } ``` ### 3.结果 ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/319322/1518927818267.png-wm) ## 四.回答问题完成实验后，在实验报告中回答如下问题： * 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。 * 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？ 1.通过GDT找到LDT，通过LDT找到进程基址，通过页目录中找到页表，通过页表找到页 2.没做，估计物理内存可能会变，线性地址不变。因为使用同一进程数组项，但因为前一次运行占用了一页内存。

“操作系统原理与实践”实验报告