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