1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2017-2023 SUSE
4 * Authors: Libor Pechacek <lpechacek@suse.cz>
5 *          Nicolai Stange <nstange@suse.de>
6 *          Marcos Paulo de Souza <mpdesouza@suse.com>
7 */
8
9#include <linux/module.h>
10#include <linux/kernel.h>
11#include <linux/sched.h>
12#include <linux/slab.h>
13#include <linux/livepatch.h>
14
15#if defined(__x86_64__)
16#define FN_PREFIX __x64_
17#elif defined(__s390x__)
18#define FN_PREFIX __s390x_
19#elif defined(__aarch64__)
20#define FN_PREFIX __arm64_
21#else
22/* powerpc does not select ARCH_HAS_SYSCALL_WRAPPER */
23#define FN_PREFIX
24#endif
25
26/* Protects klp_pids */
27static DEFINE_MUTEX(kpid_mutex);
28
29static unsigned int npids, npids_pending;
30static int klp_pids[NR_CPUS];
31module_param_array(klp_pids, int, &npids_pending, 0);
32MODULE_PARM_DESC(klp_pids, "Array of pids to be transitioned to livepatched state.");
33
34static ssize_t npids_show(struct kobject *kobj, struct kobj_attribute *attr,
35			  char *buf)
36{
37	return sprintf(buf, "%u\n", npids_pending);
38}
39
40static struct kobj_attribute klp_attr = __ATTR_RO(npids);
41static struct kobject *klp_kobj;
42
43static asmlinkage long lp_sys_getpid(void)
44{
45	int i;
46
47	mutex_lock(&kpid_mutex);
48	if (npids_pending > 0) {
49		for (i = 0; i < npids; i++) {
50			if (current->pid == klp_pids[i]) {
51				klp_pids[i] = 0;
52				npids_pending--;
53				break;
54			}
55		}
56	}
57	mutex_unlock(&kpid_mutex);
58
59	return task_tgid_vnr(current);
60}
61
62static struct klp_func vmlinux_funcs[] = {
63	{
64		.old_name = __stringify(FN_PREFIX) "sys_getpid",
65		.new_func = lp_sys_getpid,
66	}, {}
67};
68
69static struct klp_object objs[] = {
70	{
71		/* name being NULL means vmlinux */
72		.funcs = vmlinux_funcs,
73	}, {}
74};
75
76static struct klp_patch patch = {
77	.mod = THIS_MODULE,
78	.objs = objs,
79};
80
81static int livepatch_init(void)
82{
83	int ret;
84
85	klp_kobj = kobject_create_and_add("test_klp_syscall", kernel_kobj);
86	if (!klp_kobj)
87		return -ENOMEM;
88
89	ret = sysfs_create_file(klp_kobj, &klp_attr.attr);
90	if (ret) {
91		kobject_put(klp_kobj);
92		return ret;
93	}
94
95	/*
96	 * Save the number pids to transition to livepatched state before the
97	 * number of pending pids is decremented.
98	 */
99	npids = npids_pending;
100
101	return klp_enable_patch(&patch);
102}
103
104static void livepatch_exit(void)
105{
106	kobject_put(klp_kobj);
107}
108
109module_init(livepatch_init);
110module_exit(livepatch_exit);
111MODULE_LICENSE("GPL");
112MODULE_INFO(livepatch, "Y");
113MODULE_AUTHOR("Libor Pechacek <lpechacek@suse.cz>");
114MODULE_AUTHOR("Nicolai Stange <nstange@suse.de>");
115MODULE_AUTHOR("Marcos Paulo de Souza <mpdesouza@suse.com>");
116MODULE_DESCRIPTION("Livepatch test: syscall transition");
117