jcs.org
Serenity Operating System
1/*
2 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
3 * Copyright (c) 2022, kleines Filmröllchen <filmroellchen@serenityos.org>
4 *
5 * SPDX-License-Identifier: BSD-2-Clause
6 */
7
8#include <Kernel/API/Syscall.h>
9#include <Kernel/Process.h>
10#include <Kernel/Scheduler.h>
11
12namespace Kernel {
13
14ErrorOr<FlatPtr> Process::sys$yield()
15{
16 VERIFY_NO_PROCESS_BIG_LOCK(this);
17 TRY(require_promise(Pledge::stdio));
18 Thread::current()->yield_without_releasing_big_lock();
19 return 0;
20}
21
22ErrorOr<NonnullRefPtr<Thread>> Process::get_thread_from_pid_or_tid(pid_t pid_or_tid, Syscall::SchedulerParametersMode mode)
23{
24 VERIFY(g_scheduler_lock.is_locked_by_current_processor());
25 Thread* peer;
26 switch (mode) {
27 case Syscall::SchedulerParametersMode::Thread: {
28 peer = Thread::current();
29 if (pid_or_tid != 0)
30 peer = Thread::from_tid(pid_or_tid);
31
32 // Only superuser can access other processes' threads.
33 if (!credentials()->is_superuser() && peer && &peer->process() != this)
34 return EPERM;
35
36 break;
37 }
38 case Syscall::SchedulerParametersMode::Process: {
39 auto* searched_process = this;
40 if (pid_or_tid != 0)
41 searched_process = Process::from_pid_in_same_jail(pid_or_tid);
42
43 if (searched_process == nullptr)
44 return ESRCH;
45 auto pid = searched_process->pid().value();
46 // Main thread has tid == pid
47 this->thread_list().for_each([&](auto& thread) {
48 if (thread.tid().value() == pid)
49 peer = &thread;
50 });
51 break;
52 }
53 default:
54 VERIFY_NOT_REACHED();
55 }
56 if (!peer)
57 return ESRCH;
58 return NonnullRefPtr<Thread> { *peer };
59}
60
61ErrorOr<FlatPtr> Process::sys$scheduler_set_parameters(Userspace<Syscall::SC_scheduler_parameters_params const*> user_param)
62{
63 VERIFY_NO_PROCESS_BIG_LOCK(this);
64 TRY(require_promise(Pledge::proc));
65 auto parameters = TRY(copy_typed_from_user(user_param));
66
67 if (parameters.parameters.sched_priority < THREAD_PRIORITY_MIN || parameters.parameters.sched_priority > THREAD_PRIORITY_MAX)
68 return EINVAL;
69
70 SpinlockLocker lock(g_scheduler_lock);
71 auto peer = TRY(get_thread_from_pid_or_tid(parameters.pid_or_tid, parameters.mode));
72
73 auto credentials = this->credentials();
74 auto peer_credentials = peer->process().credentials();
75 if (!credentials->is_superuser() && credentials->euid() != peer_credentials->uid() && credentials->uid() != peer_credentials->uid())
76 return EPERM;
77
78 peer->set_priority((u32)parameters.parameters.sched_priority);
79 // POSIX says that process scheduling parameters have precedence over thread scheduling parameters.
80 // We don't track them separately, so overwrite the thread scheduling settings manually for now.
81 if (parameters.mode == Syscall::SchedulerParametersMode::Process) {
82 peer->process().for_each_thread([&](auto& thread) {
83 thread.set_priority((u32)parameters.parameters.sched_priority);
84 });
85 }
86
87 return 0;
88}
89
90ErrorOr<FlatPtr> Process::sys$scheduler_get_parameters(Userspace<Syscall::SC_scheduler_parameters_params*> user_param)
91{
92 VERIFY_NO_PROCESS_BIG_LOCK(this);
93 TRY(require_promise(Pledge::proc));
94
95 Syscall::SC_scheduler_parameters_params parameters;
96 TRY(copy_from_user(¶meters, user_param));
97
98 int priority;
99 {
100 SpinlockLocker lock(g_scheduler_lock);
101 auto peer = TRY(get_thread_from_pid_or_tid(parameters.pid_or_tid, parameters.mode));
102
103 auto credentials = this->credentials();
104 auto peer_credentials = peer->process().credentials();
105 if (!credentials->is_superuser() && credentials->euid() != peer_credentials->uid() && credentials->uid() != peer_credentials->uid())
106 return EPERM;
107
108 priority = (int)peer->priority();
109 }
110
111 parameters.parameters.sched_priority = priority;
112
113 TRY(copy_to_user(user_param, ¶meters));
114 return 0;
115}
116
117}