Kernel+Userland: Introduce a new way to reboot and poweroff the machine

This change removes the halt and reboot syscalls, and create a new
mechanism to change the power state of the machine.
Instead of how power state was changed until now, put a SysFS node as
writable only for the superuser, that with a defined value, can result
in either reboot or poweroff.
In the future, a power group can be assigned to this node (which will be
the GroupID responsible for power management).

This opens an opportunity to permit to shutdown/reboot without superuser
permissions, so in the future, a userspace daemon can take control of
this node to perform power management operations without superuser
permissions, if we enforce different UserID/GroupID on that node.

Kernel/Firmware/PowerStateSwitch.cpp

@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <Kernel/FileSystem/FileSystem.h>
+#include <Kernel/Firmware/ACPI/Parser.h>
+#include <Kernel/Firmware/PowerStateSwitch.h>
+#include <Kernel/IO.h>
+#include <Kernel/Process.h>
+#include <Kernel/Sections.h>
+#include <Kernel/TTY/ConsoleManagement.h>
+
+namespace Kernel {
+
+mode_t PowerStateSwitchNode::permissions() const
+{
+    return S_IRUSR | S_IRGRP | S_IWUSR | S_IWGRP;
+}
+
+UNMAP_AFTER_INIT NonnullRefPtr<PowerStateSwitchNode> PowerStateSwitchNode::must_create(FirmwareSysFSDirectory& firmware_directory)
+{
+    return adopt_ref_if_nonnull(new (nothrow) PowerStateSwitchNode(firmware_directory)).release_nonnull();
+}
+
+UNMAP_AFTER_INIT PowerStateSwitchNode::PowerStateSwitchNode(FirmwareSysFSDirectory&)
+    : SysFSComponent("power_state")
+{
+}
+
+KResultOr<size_t> PowerStateSwitchNode::write_bytes(off_t offset, size_t count, UserOrKernelBuffer const& data, OpenFileDescription*)
+{
+    if (Checked<off_t>::addition_would_overflow(offset, count))
+        return EOVERFLOW;
+    if (offset > 0)
+        return EINVAL;
+    if (count > 1)
+        return EINVAL;
+
+    char buf[1];
+    TRY(data.read(buf, 1));
+    switch (buf[0]) {
+    case '0':
+        return EINVAL;
+    case '1':
+        reboot();
+        VERIFY_NOT_REACHED();
+    case '2':
+        poweroff();
+        VERIFY_NOT_REACHED();
+    default:
+        return EINVAL;
+    }
+    VERIFY_NOT_REACHED();
+}
+
+void PowerStateSwitchNode::reboot()
+{
+    MutexLocker locker(Process::current().big_lock());
+
+    dbgln("acquiring FS locks...");
+    FileSystem::lock_all();
+    dbgln("syncing mounted filesystems...");
+    FileSystem::sync();
+    dbgln("attempting reboot via ACPI");
+    if (ACPI::is_enabled())
+        ACPI::Parser::the()->try_acpi_reboot();
+    dbgln("attempting reboot via KB Controller...");
+    IO::out8(0x64, 0xFE);
+    dbgln("reboot attempts failed, applications will stop responding.");
+    dmesgln("Reboot can't be completed. It's safe to turn off the computer!");
+    Processor::halt();
+}
+
+void PowerStateSwitchNode::poweroff()
+{
+    MutexLocker locker(Process::current().big_lock());
+
+    ConsoleManagement::the().switch_to_debug();
+
+    dbgln("acquiring FS locks...");
+    FileSystem::lock_all();
+    dbgln("syncing mounted filesystems...");
+    FileSystem::sync();
+    dbgln("attempting system shutdown...");
+    // QEMU Shutdown
+    IO::out16(0x604, 0x2000);
+    // If we're here, the shutdown failed. Try VirtualBox shutdown.
+    IO::out16(0x4004, 0x3400);
+    // VirtualBox shutdown failed. Try Bochs/Old QEMU shutdown.
+    IO::out16(0xb004, 0x2000);
+    dbgln("shutdown attempts failed, applications will stop responding.");
+    dmesgln("Shutdown can't be completed. It's safe to turn off the computer!");
+    Processor::halt();
+}
+
+}