LXR linux/drivers/usb/mon/mon

   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
  22struct snap {
  23        int slen;
  24        char str[STAT_BUF_SIZE];
  25};
  26
  27static 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
  46static 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
  54static 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
  62const 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