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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kobject-example.c (3455B)

      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 * Sample kobject implementation
      4 *
      5 * Copyright (C) 2004-2007 Greg Kroah-Hartman <greg@kroah.com>
      6 * Copyright (C) 2007 Novell Inc.
      7 */
      8#include <linux/kobject.h>
      9#include <linux/string.h>
     10#include <linux/sysfs.h>
     11#include <linux/module.h>
     12#include <linux/init.h>
     13
     14/*
     15 * This module shows how to create a simple subdirectory in sysfs called
     16 * /sys/kernel/kobject-example  In that directory, 3 files are created:
     17 * "foo", "baz", and "bar".  If an integer is written to these files, it can be
     18 * later read out of it.
     19 */
     20
     21static int foo;
     22static int baz;
     23static int bar;
     24
     25/*
     26 * The "foo" file where a static variable is read from and written to.
     27 */
     28static ssize_t foo_show(struct kobject *kobj, struct kobj_attribute *attr,
     29			char *buf)
     30{
     31	return sysfs_emit(buf, "%d\n", foo);
     32}
     33
     34static ssize_t foo_store(struct kobject *kobj, struct kobj_attribute *attr,
     35			 const char *buf, size_t count)
     36{
     37	int ret;
     38
     39	ret = kstrtoint(buf, 10, &foo);
     40	if (ret < 0)
     41		return ret;
     42
     43	return count;
     44}
     45
     46/* Sysfs attributes cannot be world-writable. */
     47static struct kobj_attribute foo_attribute =
     48	__ATTR(foo, 0664, foo_show, foo_store);
     49
     50/*
     51 * More complex function where we determine which variable is being accessed by
     52 * looking at the attribute for the "baz" and "bar" files.
     53 */
     54static ssize_t b_show(struct kobject *kobj, struct kobj_attribute *attr,
     55		      char *buf)
     56{
     57	int var;
     58
     59	if (strcmp(attr->attr.name, "baz") == 0)
     60		var = baz;
     61	else
     62		var = bar;
     63	return sysfs_emit(buf, "%d\n", var);
     64}
     65
     66static ssize_t b_store(struct kobject *kobj, struct kobj_attribute *attr,
     67		       const char *buf, size_t count)
     68{
     69	int var, ret;
     70
     71	ret = kstrtoint(buf, 10, &var);
     72	if (ret < 0)
     73		return ret;
     74
     75	if (strcmp(attr->attr.name, "baz") == 0)
     76		baz = var;
     77	else
     78		bar = var;
     79	return count;
     80}
     81
     82static struct kobj_attribute baz_attribute =
     83	__ATTR(baz, 0664, b_show, b_store);
     84static struct kobj_attribute bar_attribute =
     85	__ATTR(bar, 0664, b_show, b_store);
     86
     87
     88/*
     89 * Create a group of attributes so that we can create and destroy them all
     90 * at once.
     91 */
     92static struct attribute *attrs[] = {
     93	&foo_attribute.attr,
     94	&baz_attribute.attr,
     95	&bar_attribute.attr,
     96	NULL,	/* need to NULL terminate the list of attributes */
     97};
     98
     99/*
    100 * An unnamed attribute group will put all of the attributes directly in
    101 * the kobject directory.  If we specify a name, a subdirectory will be
    102 * created for the attributes with the directory being the name of the
    103 * attribute group.
    104 */
    105static struct attribute_group attr_group = {
    106	.attrs = attrs,
    107};
    108
    109static struct kobject *example_kobj;
    110
    111static int __init example_init(void)
    112{
    113	int retval;
    114
    115	/*
    116	 * Create a simple kobject with the name of "kobject_example",
    117	 * located under /sys/kernel/
    118	 *
    119	 * As this is a simple directory, no uevent will be sent to
    120	 * userspace.  That is why this function should not be used for
    121	 * any type of dynamic kobjects, where the name and number are
    122	 * not known ahead of time.
    123	 */
    124	example_kobj = kobject_create_and_add("kobject_example", kernel_kobj);
    125	if (!example_kobj)
    126		return -ENOMEM;
    127
    128	/* Create the files associated with this kobject */
    129	retval = sysfs_create_group(example_kobj, &attr_group);
    130	if (retval)
    131		kobject_put(example_kobj);
    132
    133	return retval;
    134}
    135
    136static void __exit example_exit(void)
    137{
    138	kobject_put(example_kobj);
    139}
    140
    141module_init(example_init);
    142module_exit(example_exit);
    143MODULE_LICENSE("GPL v2");
    144MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>");