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 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 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 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 */ 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 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 } 107 108 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 } 113 114 void sched_core_free(struct task_struct *p) 115 { 116 sched_core_put_cookie(p->core_cookie); 117 } 118 119 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 */ 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