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 
mon_stat_open(struct inode * inode,struct file * file)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 = scnprintf(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 
mon_stat_read(struct file * file,char __user * buf,size_t nbytes,loff_t * ppos)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 
mon_stat_release(struct inode * inode,struct file * file)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 	.read =		mon_stat_read,
66 	/* .write =	mon_stat_write, */
67 	/* .poll =		mon_stat_poll, */
68 	/* .unlocked_ioctl =	mon_stat_ioctl, */
69 	.release =	mon_stat_release,
70 };
71