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 static 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 static 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 static 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 static unsigned long sched_core_update_cookie(struct task_struct *p,
57 unsigned long cookie)
58 {
59 unsigned long old_cookie;
60 struct rq_flags rf;
61 struct rq *rq;
62 bool enqueued;
63
64 rq = task_rq_lock(p, &rf);
65
66 /*
67 * Since creating a cookie implies sched_core_get(), and we cannot set
68 * a cookie until after we've created it, similarly, we cannot destroy
69 * a cookie until after we've removed it, we must have core scheduling
70 * enabled here.
71 */
72 SCHED_WARN_ON((p->core_cookie || cookie) && !sched_core_enabled(rq));
73
74 enqueued = sched_core_enqueued(p);
75 if (enqueued)
76 sched_core_dequeue(rq, p);
77
78 old_cookie = p->core_cookie;
79 p->core_cookie = cookie;
80
81 if (enqueued)
82 sched_core_enqueue(rq, p);
83
84 /*
85 * If task is currently running, it may not be compatible anymore after
86 * the cookie change, so enter the scheduler on its CPU to schedule it
87 * away.
88 */
89 if (task_running(rq, p))
90 resched_curr(rq);
91
92 task_rq_unlock(rq, p, &rf);
93
94 return old_cookie;
95 }
96
sched_core_clone_cookie(struct task_struct * p)97 static unsigned long sched_core_clone_cookie(struct task_struct *p)
98 {
99 unsigned long cookie, flags;
100
101 raw_spin_lock_irqsave(&p->pi_lock, flags);
102 cookie = sched_core_get_cookie(p->core_cookie);
103 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
104
105 return cookie;
106 }
107
sched_core_fork(struct task_struct * p)108 void sched_core_fork(struct task_struct *p)
109 {
110 RB_CLEAR_NODE(&p->core_node);
111 p->core_cookie = sched_core_clone_cookie(current);
112 }
113
sched_core_free(struct task_struct * p)114 void sched_core_free(struct task_struct *p)
115 {
116 sched_core_put_cookie(p->core_cookie);
117 }
118
__sched_core_set(struct task_struct * p,unsigned long cookie)119 static void __sched_core_set(struct task_struct *p, unsigned long cookie)
120 {
121 cookie = sched_core_get_cookie(cookie);
122 cookie = sched_core_update_cookie(p, cookie);
123 sched_core_put_cookie(cookie);
124 }
125
126 /* Called from prctl interface: PR_SCHED_CORE */
sched_core_share_pid(unsigned int cmd,pid_t pid,enum pid_type type,unsigned long uaddr)127 int sched_core_share_pid(unsigned int cmd, pid_t pid, enum pid_type type,
128 unsigned long uaddr)
129 {
130 unsigned long cookie = 0, id = 0;
131 struct task_struct *task, *p;
132 struct pid *grp;
133 int err = 0;
134
135 if (!static_branch_likely(&sched_smt_present))
136 return -ENODEV;
137
138 BUILD_BUG_ON(PR_SCHED_CORE_SCOPE_THREAD != PIDTYPE_PID);
139 BUILD_BUG_ON(PR_SCHED_CORE_SCOPE_THREAD_GROUP != PIDTYPE_TGID);
140 BUILD_BUG_ON(PR_SCHED_CORE_SCOPE_PROCESS_GROUP != PIDTYPE_PGID);
141
142 if (type > PIDTYPE_PGID || cmd >= PR_SCHED_CORE_MAX || pid < 0 ||
143 (cmd != PR_SCHED_CORE_GET && uaddr))
144 return -EINVAL;
145
146 rcu_read_lock();
147 if (pid == 0) {
148 task = current;
149 } else {
150 task = find_task_by_vpid(pid);
151 if (!task) {
152 rcu_read_unlock();
153 return -ESRCH;
154 }
155 }
156 get_task_struct(task);
157 rcu_read_unlock();
158
159 /*
160 * Check if this process has the right to modify the specified
161 * process. Use the regular "ptrace_may_access()" checks.
162 */
163 if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
164 err = -EPERM;
165 goto out;
166 }
167
168 switch (cmd) {
169 case PR_SCHED_CORE_GET:
170 if (type != PIDTYPE_PID || uaddr & 7) {
171 err = -EINVAL;
172 goto out;
173 }
174 cookie = sched_core_clone_cookie(task);
175 if (cookie) {
176 /* XXX improve ? */
177 ptr_to_hashval((void *)cookie, &id);
178 }
179 err = put_user(id, (u64 __user *)uaddr);
180 goto out;
181
182 case PR_SCHED_CORE_CREATE:
183 cookie = sched_core_alloc_cookie();
184 if (!cookie) {
185 err = -ENOMEM;
186 goto out;
187 }
188 break;
189
190 case PR_SCHED_CORE_SHARE_TO:
191 cookie = sched_core_clone_cookie(current);
192 break;
193
194 case PR_SCHED_CORE_SHARE_FROM:
195 if (type != PIDTYPE_PID) {
196 err = -EINVAL;
197 goto out;
198 }
199 cookie = sched_core_clone_cookie(task);
200 __sched_core_set(current, cookie);
201 goto out;
202
203 default:
204 err = -EINVAL;
205 goto out;
206 };
207
208 if (type == PIDTYPE_PID) {
209 __sched_core_set(task, cookie);
210 goto out;
211 }
212
213 read_lock(&tasklist_lock);
214 grp = task_pid_type(task, type);
215
216 do_each_pid_thread(grp, type, p) {
217 if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS)) {
218 err = -EPERM;
219 goto out_tasklist;
220 }
221 } while_each_pid_thread(grp, type, p);
222
223 do_each_pid_thread(grp, type, p) {
224 __sched_core_set(p, cookie);
225 } while_each_pid_thread(grp, type, p);
226 out_tasklist:
227 read_unlock(&tasklist_lock);
228
229 out:
230 sched_core_put_cookie(cookie);
231 put_task_struct(task);
232 return err;
233 }
234
235