/* * procfs3.c */ #include <linux/kernel.h> #include <linux/module.h> #include <linux/proc_fs.h> #include <linux/sched.h> #include <linux/uaccess.h> #include <linux/version.h> #if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0) #define HAVE_PROC_OPS #endif #define PROCFS_MAX_SIZE 2048 #define PROCFS_ENTRY_FILENAME "buffer2k" static struct proc_dir_entry *our_proc_file; static char procfs_buffer[PROCFS_MAX_SIZE]; static unsigned long procfs_buffer_size = 0; static ssize_t procfs_read(struct file *filp, char __user *buffer, size_t length, loff_t *offset) { static int finished = 0; if (finished) { pr_debug("procfs_read: END\n"); finished = 0; return 0; } finished = 1; if (copy_to_user(buffer, procfs_buffer, procfs_buffer_size)) return -EFAULT; pr_debug("procfs_read: read %lu bytes\n", procfs_buffer_size); return procfs_buffer_size; } static ssize_t procfs_write(struct file *file, const char __user *buffer, size_t len, loff_t *off) { if (len > PROCFS_MAX_SIZE) procfs_buffer_size = PROCFS_MAX_SIZE; else procfs_buffer_size = len; if (copy_from_user(procfs_buffer, buffer, procfs_buffer_size)) return -EFAULT; pr_debug("procfs_write: write %lu bytes\n", procfs_buffer_size); return procfs_buffer_size; } static int procfs_open(struct inode *inode, struct file *file) { try_module_get(THIS_MODULE); return 0; } static int procfs_close(struct inode *inode, struct file *file) { module_put(THIS_MODULE); return 0; } #ifdef HAVE_PROC_OPS static struct proc_ops file_ops_4_our_proc_file = { .proc_read = procfs_read, .proc_write = procfs_write, .proc_open = procfs_open, .proc_release = procfs_close, }; #else static const struct file_operations file_ops_4_our_proc_file = { .read = procfs_read, .write = procfs_write, .open = procfs_open, .release = procfs_close, }; #endif static int __init procfs3_init(void) { our_proc_file = proc_create(PROCFS_ENTRY_FILENAME, 0644, NULL, &file_ops_4_our_proc_file); if (our_proc_file == NULL) { remove_proc_entry(PROCFS_ENTRY_FILENAME, NULL); pr_debug("Error: Could not initialize /proc/%s\n", PROCFS_ENTRY_FILENAME); return -ENOMEM; } proc_set_size(our_proc_file, 80); proc_set_user(our_proc_file, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID); pr_debug("/proc/%s created\n", PROCFS_ENTRY_FILENAME); return 0; } static void __exit procfs3_exit(void) { remove_proc_entry(PROCFS_ENTRY_FILENAME, NULL); pr_debug("/proc/%s removed\n", PROCFS_ENTRY_FILENAME); } module_init(procfs3_init); module_exit(procfs3_exit); MODULE_LICENSE("GPL");