One of the most highly touted advantages of Linux is the fact that it is open so

Question

One of the most highly touted advantages of Linux is the fact that it is open source and anyone can view, modify, and contribute to the Linux source code. In this project, you will make a small change to the Linux source code.

Follow the instructions called Linux Kernel Modules beginning on page 96 of the textbook. Take screenshots of the code that you add to the Linux source as you go and paste them into a Word document.

In the final part of the assignment, you will also need to take screenshots of the kernel log buffer to show successful addition, traversal, and deletion of the linked list elements. Finally, you will need to write a one to two-page reflection paper documenting the steps you have been through to complete the project, lesson learned, things that you like and dislike most about this project, difficulties you encountered and how you solved them, and what you should have done to avoid such difficulties.

Explanation / Answer

asmlinkage long sys_silly_copy(unsigned long *src, unsigned long *dst, unsigned long len) { unsigned long buf; if (copy_from_user(&buf, src, len)) return -EFAULT; ... } #include /* We're doing kernel work */ #include /* Specifically, a module */ #include #include /* for get_user and put_user */ #include "chardev.h" #define SUCCESS 0 #define DEVICE_NAME "char_dev" #define BUF_LEN 80 /* * Is the device open right now? Used to prevent * concurent access into the same device */ static int Device_Open = 0; /* * The message the device will give when asked */ static char Message[BUF_LEN]; /* * How far did the process reading the message get? * Useful if the message is larger than the size of the * buffer we get to fill in device_read. */ static char *Message_Ptr; /* * This is called whenever a process attempts to open the device file */ static int device_open(struct inode *inode, struct file *file) { #ifdef DEBUG printk(KERN_INFO "device_open(%p) ", file); #endif /* * We don't want to talk to two processes at the same time */ if (Device_Open) return -EBUSY; Device_Open++; /* * Initialize the message */ Message_Ptr = Message; try_module_get(THIS_MODULE); return SUCCESS; } static int device_release(struct inode *inode, struct file *file) { #ifdef DEBUG printk(KERN_INFO "device_release(%p,%p) ", inode, file); #endif /* * We're now ready for our next caller */ Device_Open--; module_put(THIS_MODULE); return SUCCESS; } /* * This function is called whenever a process which has already opened the * device file attempts to read from it. */ static ssize_t device_read(struct file *file, /* see include/linux/fs.h */ char __user * buffer, /* buffer to be * filled with data */ size_t length, /* length of the buffer */ loff_t * offset) { /* * Number of bytes actually written to the buffer */ int bytes_read = 0; #ifdef DEBUG printk(KERN_INFO "device_read(%p,%p,%d) ", file, buffer, length); #endif /* * If we're at the end of the message, return 0 * (which signifies end of file) */ if (*Message_Ptr == 0) return 0; /* * Actually put the data into the buffer */ while (length && *Message_Ptr) { /* * Because the buffer is in the user data segment, * not the kernel data segment, assignment wouldn't * work. Instead, we have to use put_user which * copies data from the kernel data segment to the * user data segment. */ put_user(*(Message_Ptr++), buffer++); length--; bytes_read++; } #ifdef DEBUG printk(KERN_INFO "Read %d bytes, %d left ", bytes_read, length); #endif /* * Read functions are supposed to return the number * of bytes actually inserted into the buffer */ return bytes_read; } /* * This function is called when somebody tries to * write into our device file. */ static ssize_t device_write(struct file *file, const char __user * buffer, size_t length, loff_t * offset) { int i; #ifdef DEBUG printk(KERN_INFO "device_write(%p,%s,%d)", file, buffer, length); #endif for (i = 0; i

Related Questions

Navigate

• Browse (All)
• Browse O
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.