1 // SPDX-License-Identifier: GPL-2.0-only
2
3 #include <linux/prctl.h>
4 #include "sched.h"
5
6 /*
7 * A simple wrapper around refcount. An allocated sched_core_cookie's
8 * address is used to compute the cookie of the task.
9 */
10 struct sched_core_cookie {
11 refcount_t refcnt;
12 };
13
sched_core_alloc_cookie(void)14 unsigned long sched_core_alloc_cookie(void)
15 {
16 struct sched_core_cookie *ck = kmalloc(sizeof(*ck), GFP_KERNEL);
17 if (!ck)
18 return 0;
19
20 refcount_set(&ck->refcnt, 1);
21 sched_core_get();
22
23 return (unsigned long)ck;
24 }
25
sched_core_put_cookie(unsigned long cookie)26 void sched_core_put_cookie(unsigned long cookie)
27 {
28 struct sched_core_cookie *ptr = (void *)cookie;
29
30 if (ptr && refcount_dec_and_test(&ptr->refcnt)) {
31 kfree(ptr);
32 sched_core_put();
33 }
34 }
35
sched_core_get_cookie(unsigned long cookie)36 unsigned long sched_core_get_cookie(unsigned long cookie)
37 {
38 struct sched_core_cookie *ptr = (void *)cookie;
39
40 if (ptr)
41 refcount_inc(&ptr->refcnt);
42
43 return cookie;
44 }
45
46 /*
47 * sched_core_update_cookie - replace the cookie on a task
48 * @p: the task to update
49 * @cookie: the new cookie
50 *
51 * Effectively exchange the task cookie; caller is responsible for lifetimes on
52 * both ends.
53 *
54 * Returns: the old cookie
55 */
sched_core_update_cookie(struct task_struct * p,unsigned long cookie)56 unsigned long sched_core_update_cookie(struct task_struct *p, unsigned long cookie)
57 {
58 unsigned long old_cookie;
59 struct rq_flags rf;
60 struct rq *rq;
61 bool enqueued;
62
63 rq = task_rq_lock(p, &rf);
64
65 /*
66 * Since creating a cookie implies sched_core_get(), and we cannot set
67 * a cookie until after we've created it, similarly, we cannot destroy
68 * a cookie until after we've removed it, we must have core scheduling
69 * enabled here.
70 */
71 SCHED_WARN_ON((p->core_cookie || cookie) && !sched_core_enabled(rq));
72
73 enqueued = sched_core_enqueued(p);
74 if (enqueued)
75 sched_core_dequeue(rq, p);
76
77 old_cookie = p->core_cookie;
78 p->core_cookie = cookie;
79
80 if (enqueued)
81 sched_core_enqueue(rq, p);
82
83 /*
84 * If task is currently running, it may not be compatible anymore after
85 * the cookie change, so enter the scheduler on its CPU to schedule it
86 * away.
87 */
88 if (task_running(rq, p))
89 resched_curr(rq);
90
91 task_rq_unlock(rq, p, &rf);
92
93 return old_cookie;
94 }
95
sched_core_clone_cookie(struct task_struct * p)96 static unsigned long sched_core_clone_cookie(struct task_struct *p)
97 {
98 unsigned long cookie, flags;
99
100 raw_spin_lock_irqsave(&p->pi_lock, flags);
101 cookie = sched_core_get_cookie(p->core_cookie);
102 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
103
104 return cookie;
105 }
106
sched_core_fork(struct task_struct * p)107 void sched_core_fork(struct task_struct *p)
108 {
109 RB_CLEAR_NODE(&p->core_node);
110 p->core_cookie = sched_core_clone_cookie(current);
111 }
112
sched_core_free(struct task_struct * p)113 void sched_core_free(struct task_struct *p)
114 {
115 sched_core_put_cookie(p->core_cookie);
116 }
117
__sched_core_set(struct task_struct * p,unsigned long cookie)118 static void __sched_core_set(struct task_struct *p, unsigned long cookie)
119 {
120 cookie = sched_core_get_cookie(cookie);
121 cookie = sched_core_update_cookie(p, cookie);
122 sched_core_put_cookie(cookie);
123 }
124
125 /* Called from prctl interface: PR_SCHED_CORE */
sched_core_share_pid(unsigned int cmd,pid_t pid,enum pid_type type,unsigned long uaddr)126 int sched_core_share_pid(unsigned int cmd, pid_t pid, enum pid_type type,
127 unsigned long uaddr)
128 {
129 unsigned long cookie = 0, id = 0;
130 struct task_struct *task, *p;
131 struct pid *grp;
132 int err = 0;
133
134 if (!static_branch_likely(&sched_smt_present))
135 return -ENODEV;
136
137 if (type > PIDTYPE_PGID || cmd >= PR_SCHED_CORE_MAX || pid < 0 ||
138 (cmd != PR_SCHED_CORE_GET && uaddr))
139 return -EINVAL;
140
141 rcu_read_lock();
142 if (pid == 0) {
143 task = current;
144 } else {
145 task = find_task_by_vpid(pid);
146 if (!task) {
147 rcu_read_unlock();
148 return -ESRCH;
149 }
150 }
151 get_task_struct(task);
152 rcu_read_unlock();
153
154 /*
155 * Check if this process has the right to modify the specified
156 * process. Use the regular "ptrace_may_access()" checks.
157 */
158 if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
159 err = -EPERM;
160 goto out;
161 }
162
163 switch (cmd) {
164 case PR_SCHED_CORE_GET:
165 if (type != PIDTYPE_PID || uaddr & 7) {
166 err = -EINVAL;
167 goto out;
168 }
169 cookie = sched_core_clone_cookie(task);
170 if (cookie) {
171 /* XXX improve ? */
172 ptr_to_hashval((void *)cookie, &id);
173 }
174 err = put_user(id, (u64 __user *)uaddr);
175 goto out;
176
177 case PR_SCHED_CORE_CREATE:
178 cookie = sched_core_alloc_cookie();
179 if (!cookie) {
180 err = -ENOMEM;
181 goto out;
182 }
183 break;
184
185 case PR_SCHED_CORE_SHARE_TO:
186 cookie = sched_core_clone_cookie(current);
187 break;
188
189 case PR_SCHED_CORE_SHARE_FROM:
190 if (type != PIDTYPE_PID) {
191 err = -EINVAL;
192 goto out;
193 }
194 cookie = sched_core_clone_cookie(task);
195 __sched_core_set(current, cookie);
196 goto out;
197
198 default:
199 err = -EINVAL;
200 goto out;
201 };
202
203 if (type == PIDTYPE_PID) {
204 __sched_core_set(task, cookie);
205 goto out;
206 }
207
208 read_lock(&tasklist_lock);
209 grp = task_pid_type(task, type);
210
211 do_each_pid_thread(grp, type, p) {
212 if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS)) {
213 err = -EPERM;
214 goto out_tasklist;
215 }
216 } while_each_pid_thread(grp, type, p);
217
218 do_each_pid_thread(grp, type, p) {
219 __sched_core_set(p, cookie);
220 } while_each_pid_thread(grp, type, p);
221 out_tasklist:
222 read_unlock(&tasklist_lock);
223
224 out:
225 sched_core_put_cookie(cookie);
226 put_task_struct(task);
227 return err;
228 }
229
230
