235 lines
5.0 KiB
C
235 lines
5.0 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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#include <linux/prctl.h>
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#include "sched.h"
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/*
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* A simple wrapper around refcount. An allocated sched_core_cookie's
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* address is used to compute the cookie of the task.
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*/
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struct sched_core_cookie {
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refcount_t refcnt;
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};
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static unsigned long sched_core_alloc_cookie(void)
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{
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struct sched_core_cookie *ck = kmalloc(sizeof(*ck), GFP_KERNEL);
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if (!ck)
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return 0;
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refcount_set(&ck->refcnt, 1);
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sched_core_get();
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return (unsigned long)ck;
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}
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static void sched_core_put_cookie(unsigned long cookie)
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{
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struct sched_core_cookie *ptr = (void *)cookie;
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if (ptr && refcount_dec_and_test(&ptr->refcnt)) {
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kfree(ptr);
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sched_core_put();
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}
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}
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static unsigned long sched_core_get_cookie(unsigned long cookie)
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{
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struct sched_core_cookie *ptr = (void *)cookie;
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if (ptr)
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refcount_inc(&ptr->refcnt);
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return cookie;
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}
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/*
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* sched_core_update_cookie - replace the cookie on a task
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* @p: the task to update
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* @cookie: the new cookie
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*
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* Effectively exchange the task cookie; caller is responsible for lifetimes on
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* both ends.
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*
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* Returns: the old cookie
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*/
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static unsigned long sched_core_update_cookie(struct task_struct *p,
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unsigned long cookie)
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{
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unsigned long old_cookie;
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struct rq_flags rf;
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struct rq *rq;
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bool enqueued;
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rq = task_rq_lock(p, &rf);
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/*
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* Since creating a cookie implies sched_core_get(), and we cannot set
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* a cookie until after we've created it, similarly, we cannot destroy
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* a cookie until after we've removed it, we must have core scheduling
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* enabled here.
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*/
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SCHED_WARN_ON((p->core_cookie || cookie) && !sched_core_enabled(rq));
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enqueued = sched_core_enqueued(p);
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if (enqueued)
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sched_core_dequeue(rq, p);
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old_cookie = p->core_cookie;
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p->core_cookie = cookie;
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if (enqueued)
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sched_core_enqueue(rq, p);
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/*
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* If task is currently running, it may not be compatible anymore after
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* the cookie change, so enter the scheduler on its CPU to schedule it
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* away.
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*/
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if (task_running(rq, p))
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resched_curr(rq);
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task_rq_unlock(rq, p, &rf);
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return old_cookie;
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}
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static unsigned long sched_core_clone_cookie(struct task_struct *p)
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{
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unsigned long cookie, flags;
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raw_spin_lock_irqsave(&p->pi_lock, flags);
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cookie = sched_core_get_cookie(p->core_cookie);
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raw_spin_unlock_irqrestore(&p->pi_lock, flags);
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return cookie;
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}
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void sched_core_fork(struct task_struct *p)
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{
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RB_CLEAR_NODE(&p->core_node);
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p->core_cookie = sched_core_clone_cookie(current);
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}
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void sched_core_free(struct task_struct *p)
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{
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sched_core_put_cookie(p->core_cookie);
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}
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static void __sched_core_set(struct task_struct *p, unsigned long cookie)
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{
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cookie = sched_core_get_cookie(cookie);
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cookie = sched_core_update_cookie(p, cookie);
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sched_core_put_cookie(cookie);
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}
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/* Called from prctl interface: PR_SCHED_CORE */
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int sched_core_share_pid(unsigned int cmd, pid_t pid, enum pid_type type,
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unsigned long uaddr)
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{
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unsigned long cookie = 0, id = 0;
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struct task_struct *task, *p;
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struct pid *grp;
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int err = 0;
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if (!static_branch_likely(&sched_smt_present))
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return -ENODEV;
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BUILD_BUG_ON(PR_SCHED_CORE_SCOPE_THREAD != PIDTYPE_PID);
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BUILD_BUG_ON(PR_SCHED_CORE_SCOPE_THREAD_GROUP != PIDTYPE_TGID);
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BUILD_BUG_ON(PR_SCHED_CORE_SCOPE_PROCESS_GROUP != PIDTYPE_PGID);
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if (type > PIDTYPE_PGID || cmd >= PR_SCHED_CORE_MAX || pid < 0 ||
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(cmd != PR_SCHED_CORE_GET && uaddr))
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return -EINVAL;
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rcu_read_lock();
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if (pid == 0) {
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task = current;
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} else {
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task = find_task_by_vpid(pid);
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if (!task) {
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rcu_read_unlock();
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return -ESRCH;
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}
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}
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get_task_struct(task);
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rcu_read_unlock();
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/*
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* Check if this process has the right to modify the specified
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* process. Use the regular "ptrace_may_access()" checks.
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*/
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if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
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err = -EPERM;
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goto out;
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}
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switch (cmd) {
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case PR_SCHED_CORE_GET:
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if (type != PIDTYPE_PID || uaddr & 7) {
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err = -EINVAL;
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goto out;
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}
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cookie = sched_core_clone_cookie(task);
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if (cookie) {
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/* XXX improve ? */
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ptr_to_hashval((void *)cookie, &id);
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}
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err = put_user(id, (u64 __user *)uaddr);
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goto out;
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case PR_SCHED_CORE_CREATE:
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cookie = sched_core_alloc_cookie();
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if (!cookie) {
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err = -ENOMEM;
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goto out;
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}
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break;
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case PR_SCHED_CORE_SHARE_TO:
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cookie = sched_core_clone_cookie(current);
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break;
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case PR_SCHED_CORE_SHARE_FROM:
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if (type != PIDTYPE_PID) {
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err = -EINVAL;
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goto out;
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}
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cookie = sched_core_clone_cookie(task);
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__sched_core_set(current, cookie);
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goto out;
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default:
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err = -EINVAL;
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goto out;
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};
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if (type == PIDTYPE_PID) {
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__sched_core_set(task, cookie);
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goto out;
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}
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read_lock(&tasklist_lock);
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grp = task_pid_type(task, type);
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do_each_pid_thread(grp, type, p) {
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if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS)) {
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err = -EPERM;
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goto out_tasklist;
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}
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} while_each_pid_thread(grp, type, p);
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do_each_pid_thread(grp, type, p) {
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__sched_core_set(p, cookie);
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} while_each_pid_thread(grp, type, p);
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out_tasklist:
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read_unlock(&tasklist_lock);
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out:
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sched_core_put_cookie(cookie);
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put_task_struct(task);
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return err;
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}
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