drivers/usb/mon/mon_stat.c

   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 };