cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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bytestream-example.c (4098B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * Sample kfifo byte stream implementation
      4 *
      5 * Copyright (C) 2010 Stefani Seibold <stefani@seibold.net>
      6 */
      7
      8#include <linux/init.h>
      9#include <linux/module.h>
     10#include <linux/proc_fs.h>
     11#include <linux/mutex.h>
     12#include <linux/kfifo.h>
     13
     14/*
     15 * This module shows how to create a byte stream fifo.
     16 */
     17
     18/* fifo size in elements (bytes) */
     19#define FIFO_SIZE	32
     20
     21/* name of the proc entry */
     22#define	PROC_FIFO	"bytestream-fifo"
     23
     24/* lock for procfs read access */
     25static DEFINE_MUTEX(read_access);
     26
     27/* lock for procfs write access */
     28static DEFINE_MUTEX(write_access);
     29
     30/*
     31 * define DYNAMIC in this example for a dynamically allocated fifo.
     32 *
     33 * Otherwise the fifo storage will be a part of the fifo structure.
     34 */
     35#if 0
     36#define DYNAMIC
     37#endif
     38
     39#ifdef DYNAMIC
     40static struct kfifo test;
     41#else
     42static DECLARE_KFIFO(test, unsigned char, FIFO_SIZE);
     43#endif
     44
     45static const unsigned char expected_result[FIFO_SIZE] = {
     46	 3,  4,  5,  6,  7,  8,  9,  0,
     47	 1, 20, 21, 22, 23, 24, 25, 26,
     48	27, 28, 29, 30, 31, 32, 33, 34,
     49	35, 36, 37, 38, 39, 40, 41, 42,
     50};
     51
     52static int __init testfunc(void)
     53{
     54	unsigned char	buf[6];
     55	unsigned char	i, j;
     56	unsigned int	ret;
     57
     58	printk(KERN_INFO "byte stream fifo test start\n");
     59
     60	/* put string into the fifo */
     61	kfifo_in(&test, "hello", 5);
     62
     63	/* put values into the fifo */
     64	for (i = 0; i != 10; i++)
     65		kfifo_put(&test, i);
     66
     67	/* show the number of used elements */
     68	printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
     69
     70	/* get max of 5 bytes from the fifo */
     71	i = kfifo_out(&test, buf, 5);
     72	printk(KERN_INFO "buf: %.*s\n", i, buf);
     73
     74	/* get max of 2 elements from the fifo */
     75	ret = kfifo_out(&test, buf, 2);
     76	printk(KERN_INFO "ret: %d\n", ret);
     77	/* and put it back to the end of the fifo */
     78	ret = kfifo_in(&test, buf, ret);
     79	printk(KERN_INFO "ret: %d\n", ret);
     80
     81	/* skip first element of the fifo */
     82	printk(KERN_INFO "skip 1st element\n");
     83	kfifo_skip(&test);
     84
     85	/* put values into the fifo until is full */
     86	for (i = 20; kfifo_put(&test, i); i++)
     87		;
     88
     89	printk(KERN_INFO "queue len: %u\n", kfifo_len(&test));
     90
     91	/* show the first value without removing from the fifo */
     92	if (kfifo_peek(&test, &i))
     93		printk(KERN_INFO "%d\n", i);
     94
     95	/* check the correctness of all values in the fifo */
     96	j = 0;
     97	while (kfifo_get(&test, &i)) {
     98		printk(KERN_INFO "item = %d\n", i);
     99		if (i != expected_result[j++]) {
    100			printk(KERN_WARNING "value mismatch: test failed\n");
    101			return -EIO;
    102		}
    103	}
    104	if (j != ARRAY_SIZE(expected_result)) {
    105		printk(KERN_WARNING "size mismatch: test failed\n");
    106		return -EIO;
    107	}
    108	printk(KERN_INFO "test passed\n");
    109
    110	return 0;
    111}
    112
    113static ssize_t fifo_write(struct file *file, const char __user *buf,
    114						size_t count, loff_t *ppos)
    115{
    116	int ret;
    117	unsigned int copied;
    118
    119	if (mutex_lock_interruptible(&write_access))
    120		return -ERESTARTSYS;
    121
    122	ret = kfifo_from_user(&test, buf, count, &copied);
    123
    124	mutex_unlock(&write_access);
    125	if (ret)
    126		return ret;
    127
    128	return copied;
    129}
    130
    131static ssize_t fifo_read(struct file *file, char __user *buf,
    132						size_t count, loff_t *ppos)
    133{
    134	int ret;
    135	unsigned int copied;
    136
    137	if (mutex_lock_interruptible(&read_access))
    138		return -ERESTARTSYS;
    139
    140	ret = kfifo_to_user(&test, buf, count, &copied);
    141
    142	mutex_unlock(&read_access);
    143	if (ret)
    144		return ret;
    145
    146	return copied;
    147}
    148
    149static const struct proc_ops fifo_proc_ops = {
    150	.proc_read	= fifo_read,
    151	.proc_write	= fifo_write,
    152	.proc_lseek	= noop_llseek,
    153};
    154
    155static int __init example_init(void)
    156{
    157#ifdef DYNAMIC
    158	int ret;
    159
    160	ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
    161	if (ret) {
    162		printk(KERN_ERR "error kfifo_alloc\n");
    163		return ret;
    164	}
    165#else
    166	INIT_KFIFO(test);
    167#endif
    168	if (testfunc() < 0) {
    169#ifdef DYNAMIC
    170		kfifo_free(&test);
    171#endif
    172		return -EIO;
    173	}
    174
    175	if (proc_create(PROC_FIFO, 0, NULL, &fifo_proc_ops) == NULL) {
    176#ifdef DYNAMIC
    177		kfifo_free(&test);
    178#endif
    179		return -ENOMEM;
    180	}
    181	return 0;
    182}
    183
    184static void __exit example_exit(void)
    185{
    186	remove_proc_entry(PROC_FIFO, NULL);
    187#ifdef DYNAMIC
    188	kfifo_free(&test);
    189#endif
    190}
    191
    192module_init(example_init);
    193module_exit(example_exit);
    194MODULE_LICENSE("GPL");
    195MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");