1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * The USB Monitor, inspired by Dave Harding's USBMon. 4 * 5 * This is the 's' or 'stat' reader which debugs usbmon itself. 6 * Note that this code blows through locks, so make sure that 7 * /dbg/usbmon/0s is well protected from non-root users. 8 * 9 */ 10 11 #include <linux/kernel.h> 12 #include <linux/slab.h> 13 #include <linux/export.h> 14 #include <linux/usb.h> 15 #include <linux/fs.h> 16 #include <linux/uaccess.h> 17 18 #include "usb_mon.h" 19 20 #define STAT_BUF_SIZE 80 21 22 struct snap { 23 int slen; 24 char str[STAT_BUF_SIZE]; 25 }; 26 27 static int mon_stat_open(struct inode *inode, struct file *file) 28 { 29 struct mon_bus *mbus; 30 struct snap *sp; 31 32 sp = kmalloc(sizeof(struct snap), GFP_KERNEL); 33 if (sp == NULL) 34 return -ENOMEM; 35 36 mbus = inode->i_private; 37 38 sp->slen = snprintf(sp->str, STAT_BUF_SIZE, 39 "nreaders %d events %u text_lost %u\n", 40 mbus->nreaders, mbus->cnt_events, mbus->cnt_text_lost); 41 42 file->private_data = sp; 43 return 0; 44 } 45 46 static ssize_t mon_stat_read(struct file *file, char __user *buf, 47 size_t nbytes, loff_t *ppos) 48 { 49 struct snap *sp = file->private_data; 50 51 return simple_read_from_buffer(buf, nbytes, ppos, sp->str, sp->slen); 52 } 53 54 static int mon_stat_release(struct inode *inode, struct file *file) 55 { 56 struct snap *sp = file->private_data; 57 file->private_data = NULL; 58 kfree(sp); 59 return 0; 60 } 61 62 const struct file_operations mon_fops_stat = { 63 .owner = THIS_MODULE, 64 .open = mon_stat_open, 65 .llseek = no_llseek, 66 .read = mon_stat_read, 67 /* .write = mon_stat_write, */ 68 /* .poll = mon_stat_poll, */ 69 /* .unlocked_ioctl = mon_stat_ioctl, */ 70 .release = mon_stat_release, 71 }; 72