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Userspace initially didn't have any sort of mechanism to handle device hotplug (either removing or inserting a device). This meant that after a short term of scanning all known devices, by fetching device events (DeviceEvent packets) from /dev/devctl, we basically never try to read it again after SystemServer initialization code. To accommodate hotplug needs, we change SystemServer by ensuring it will generate a known set of device nodes at their location during the its main initialization code. This includes devices like /dev/mem, /dev/zero and /dev/full, etc. The actual responsible userspace program to handle hotplug events is a new userspace program called DeviceMapper, with following key points: - Its current task is to to constantly read the /dev/devctl device node. Because we already created generic devices, we only handle devices that are dynamically-generated in nature, like storage devices, audio channels, etc. - Since dynamically-generated device nodes could have an infinite minor numbers, but major numbers are decoded to a device type, we create an internal registry based on two structures - DeviceNodeFamily, and RegisteredDeviceNode. DeviceNodeFamily objects are attached in the main logic code, when handling a DeviceEvent device insertion packet. A DeviceNodeFamily object has an internal HashTable to hold objects of RegisteredDeviceNode class. - Because some device nodes could still share the same major number (TTY and serial TTY devices), we have two modes of allocation - limited allocation (so a range is defined for a major number), or infinite range. Therefore, two (or more) separate DeviceNodeFamily objects can can exist albeit sharing the same major number, but they are required to allocate from a different minor numbers' range to ensure there are no collisions. - As for KCOV, we handle this device differently. In case the user compiled the kernel with such support - this happens to be a singular device node that we usually don't need, so it's dynamically-generated too, and because it has only one instance, we don't register it in our internal registry to not make it complicated needlessly. The Kernel code is modified to allow proper blocking in case of no events in the DeviceControlDevice class, because otherwise we will need to poll periodically the device to check if a new event is available, which would waste CPU time for no good reason.
243 lines
12 KiB
C++
243 lines
12 KiB
C++
/*
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* Copyright (c) 2023, Liav A. <liavalb@hotmail.co.il>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include "DeviceEventLoop.h"
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#include <AK/Debug.h>
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#include <LibCore/DirIterator.h>
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#include <LibCore/System.h>
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#include <LibIPC/MultiServer.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <unistd.h>
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namespace DeviceMapper {
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DeviceEventLoop::DeviceEventLoop(NonnullOwnPtr<Core::File> devctl_file)
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: m_devctl_file(move(devctl_file))
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{
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}
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using MinorNumberAllocationType = DeviceEventLoop::MinorNumberAllocationType;
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static constexpr DeviceEventLoop::DeviceNodeMatch s_matchers[] = {
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{ "audio"sv, "audio"sv, "audio/%digit"sv, DeviceNodeFamily::Type::CharacterDevice, 116, MinorNumberAllocationType::SequentialUnlimited, 0, 0, 0220 },
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{ {}, "render"sv, "gpu/render%digit"sv, DeviceNodeFamily::Type::CharacterDevice, 28, MinorNumberAllocationType::SequentialUnlimited, 0, 0, 0666 },
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{ "window"sv, "gpu-connector"sv, "gpu/connector%digit"sv, DeviceNodeFamily::Type::CharacterDevice, 226, MinorNumberAllocationType::SequentialUnlimited, 0, 0, 0660 },
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{ {}, "virtio-console"sv, "hvc0p%digit"sv, DeviceNodeFamily::Type::CharacterDevice, 229, MinorNumberAllocationType::SequentialUnlimited, 0, 0, 0666 },
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{ "phys"sv, "hid-mouse"sv, "input/mouse/%digit"sv, DeviceNodeFamily::Type::CharacterDevice, 10, MinorNumberAllocationType::SequentialUnlimited, 0, 0, 0666 },
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{ "phys"sv, "hid-keyboard"sv, "input/keyboard/%digit"sv, DeviceNodeFamily::Type::CharacterDevice, 85, MinorNumberAllocationType::SequentialUnlimited, 0, 0, 0666 },
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{ {}, "storage"sv, "hd%letter"sv, DeviceNodeFamily::Type::BlockDevice, 3, MinorNumberAllocationType::SequentialUnlimited, 0, 0, 0600 },
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{ "tty"sv, "console"sv, "tty%digit"sv, DeviceNodeFamily::Type::CharacterDevice, 4, MinorNumberAllocationType::SequentialLimited, 0, 63, 0620 },
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{ "tty"sv, "console"sv, "ttyS%digit"sv, DeviceNodeFamily::Type::CharacterDevice, 4, MinorNumberAllocationType::SequentialLimited, 64, 127, 0620 },
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};
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static bool is_in_minor_number_range(DeviceEventLoop::DeviceNodeMatch const& matcher, MinorNumber minor_number)
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{
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if (matcher.minor_number_allocation_type == MinorNumberAllocationType::SequentialUnlimited)
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return true;
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return matcher.minor_number_start <= minor_number && static_cast<MinorNumber>(matcher.minor_number_start.value() + matcher.minor_number_range_size) >= minor_number;
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}
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static Optional<DeviceEventLoop::DeviceNodeMatch const&> device_node_family_to_match_type(DeviceNodeFamily::Type unix_device_type, MajorNumber major_number, MinorNumber minor_number)
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{
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for (auto& matcher : s_matchers) {
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if (matcher.major_number == major_number
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&& unix_device_type == matcher.unix_device_type
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&& is_in_minor_number_range(matcher, minor_number))
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return matcher;
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}
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return {};
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}
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static bool is_in_family_minor_number_range(DeviceNodeFamily const& family, MinorNumber minor_number)
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{
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return family.base_minor_number() <= minor_number && static_cast<MinorNumber>(family.base_minor_number().value() + family.devices_symbol_suffix_allocation_map().size()) >= minor_number;
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}
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Optional<DeviceNodeFamily&> DeviceEventLoop::find_device_node_family(DeviceNodeFamily::Type unix_device_type, MajorNumber major_number, MinorNumber minor_number) const
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{
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for (auto const& family : m_device_node_families) {
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if (family->major_number() == major_number && family->type() == unix_device_type && is_in_family_minor_number_range(*family, minor_number))
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return *family.ptr();
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}
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return {};
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}
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ErrorOr<NonnullRefPtr<DeviceNodeFamily>> DeviceEventLoop::find_or_register_new_device_node_family(DeviceNodeMatch const& match, DeviceNodeFamily::Type unix_device_type, MajorNumber major_number, MinorNumber minor_number)
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{
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if (auto possible_family = find_device_node_family(unix_device_type, major_number, minor_number); possible_family.has_value())
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return possible_family.release_value();
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unsigned allocation_map_size = 1024;
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if (match.minor_number_allocation_type == MinorNumberAllocationType::SequentialLimited)
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allocation_map_size = match.minor_number_range_size;
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auto bitmap = TRY(Bitmap::create(allocation_map_size, false));
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auto node = TRY(adopt_nonnull_ref_or_enomem(new (nothrow) DeviceNodeFamily(move(bitmap),
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match.family_type_literal,
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unix_device_type,
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major_number,
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minor_number)));
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TRY(m_device_node_families.try_append(node));
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return node;
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}
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static ErrorOr<String> build_suffix_with_letters(size_t allocation_index)
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{
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auto base_string = TRY(String::from_utf8(""sv));
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while (true) {
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base_string = TRY(String::formatted("{:c}{}", 'a' + (allocation_index % 26), base_string));
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allocation_index = (allocation_index / 26);
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if (allocation_index == 0)
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break;
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allocation_index = allocation_index - 1;
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}
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return base_string;
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}
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static ErrorOr<String> build_suffix_with_numbers(size_t allocation_index)
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{
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return String::number(allocation_index);
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}
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static ErrorOr<void> prepare_permissions_after_populating_devtmpfs(StringView path, DeviceEventLoop::DeviceNodeMatch const& match)
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{
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if (match.permission_group.is_null())
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return {};
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auto group = TRY(Core::System::getgrnam(match.permission_group));
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VERIFY(group.has_value());
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TRY(Core::System::endgrent());
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TRY(Core::System::chown(path, 0, group.value().gr_gid));
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return {};
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}
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ErrorOr<void> DeviceEventLoop::register_new_device(DeviceNodeFamily::Type unix_device_type, MajorNumber major_number, MinorNumber minor_number)
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{
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auto possible_match = device_node_family_to_match_type(unix_device_type, major_number, minor_number);
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if (!possible_match.has_value())
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return {};
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auto const& match = possible_match.release_value();
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auto device_node_family = TRY(find_or_register_new_device_node_family(match, unix_device_type, major_number, minor_number));
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static constexpr StringView devtmpfs_base_path = "/dev/"sv;
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auto path_pattern = TRY(String::from_utf8(match.path_pattern));
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auto& allocation_map = device_node_family->devices_symbol_suffix_allocation_map();
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auto possible_allocated_suffix_index = allocation_map.find_first_unset();
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if (!possible_allocated_suffix_index.has_value()) {
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// FIXME: Make the allocation map bigger?
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return Error::from_errno(ERANGE);
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}
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auto allocated_suffix_index = possible_allocated_suffix_index.release_value();
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auto path = TRY(String::from_utf8(path_pattern));
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if (match.path_pattern.contains("%digit"sv)) {
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auto replacement = TRY(build_suffix_with_numbers(allocated_suffix_index));
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path = TRY(path.replace("%digit"sv, replacement, ReplaceMode::All));
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}
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if (match.path_pattern.contains("%letter"sv)) {
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auto replacement = TRY(build_suffix_with_letters(allocated_suffix_index));
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path = TRY(path.replace("%letter"sv, replacement, ReplaceMode::All));
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}
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VERIFY(!path.is_empty());
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path = TRY(String::formatted("{}{}", devtmpfs_base_path, path));
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mode_t old_mask = umask(0);
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if (unix_device_type == DeviceNodeFamily::Type::BlockDevice)
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TRY(Core::System::create_block_device(path.bytes_as_string_view(), match.create_mode, major_number.value(), minor_number.value()));
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else
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TRY(Core::System::create_char_device(path.bytes_as_string_view(), match.create_mode, major_number.value(), minor_number.value()));
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umask(old_mask);
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TRY(prepare_permissions_after_populating_devtmpfs(path.bytes_as_string_view(), match));
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auto result = TRY(device_node_family->registered_nodes().try_set(RegisteredDeviceNode { move(path), minor_number }, AK::HashSetExistingEntryBehavior::Keep));
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VERIFY(result != HashSetResult::ReplacedExistingEntry);
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if (result == HashSetResult::KeptExistingEntry) {
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// FIXME: Handle this case properly.
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return Error::from_errno(EEXIST);
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}
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allocation_map.set(allocated_suffix_index, true);
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return {};
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}
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ErrorOr<void> DeviceEventLoop::unregister_device(DeviceNodeFamily::Type unix_device_type, MajorNumber major_number, MinorNumber minor_number)
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{
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if (!device_node_family_to_match_type(unix_device_type, major_number, minor_number).has_value())
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return {};
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auto possible_family = find_device_node_family(unix_device_type, major_number, minor_number);
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if (!possible_family.has_value()) {
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// FIXME: Handle cases where we can't remove a device node.
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// This could happen when the DeviceMapper program was restarted
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// so the previous state was not preserved and a device was removed.
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return Error::from_errno(ENODEV);
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}
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auto& family = possible_family.release_value();
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for (auto& node : family.registered_nodes()) {
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if (node.minor_number() == minor_number)
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TRY(Core::System::unlink(node.device_path()));
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}
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auto removed_anything = family.registered_nodes().remove_all_matching([minor_number](auto& device) { return device.minor_number() == minor_number; });
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if (!removed_anything) {
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// FIXME: Handle cases where we can't remove a device node.
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// This could happen when the DeviceMapper program was restarted
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// so the previous state was not preserved and a device was removed.
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return Error::from_errno(ENODEV);
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}
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return {};
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}
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static ErrorOr<void> create_kcov_device_node()
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{
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mode_t old_mask = umask(0);
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ScopeGuard umask_guard([old_mask] { umask(old_mask); });
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TRY(Core::System::create_char_device("/dev/kcov"sv, 0666, 30, 0));
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return {};
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}
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ErrorOr<void> DeviceEventLoop::read_one_or_eof(DeviceEvent& event)
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{
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if (m_devctl_file->read_until_filled({ bit_cast<u8*>(&event), sizeof(DeviceEvent) }).is_error()) {
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// Bad! Kernel and SystemServer apparently disagree on the record size,
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// which means that previous data is likely to be invalid.
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return Error::from_string_view("File ended after incomplete record? /dev/devctl seems broken!"sv);
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}
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return {};
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}
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ErrorOr<void> DeviceEventLoop::drain_events_from_devctl()
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{
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for (;;) {
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DeviceEvent event;
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TRY(read_one_or_eof(event));
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// NOTE: Ignore any event related to /dev/devctl device node - normally
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// it should never disappear from the system and we already use it in this
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// code.
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if (event.major_number == 2 && event.minor_number == 10 && !event.is_block_device)
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continue;
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if (event.state == DeviceEvent::State::Inserted) {
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// NOTE: We have a special function for the KCOV device, because we don't
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// want to create a new MinorNumberAllocationType (e.g. SingleInstance).
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// Instead, just blindly create that device node and assume we will never
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// have to worry about it, so we don't need to register that!
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if (event.major_number == 30 && event.minor_number == 0 && !event.is_block_device) {
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TRY(create_kcov_device_node());
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continue;
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}
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VERIFY(event.is_block_device == 1 || event.is_block_device == 0);
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TRY(register_new_device(event.is_block_device ? DeviceNodeFamily::Type::BlockDevice : DeviceNodeFamily::Type::CharacterDevice, event.major_number, event.minor_number));
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} else if (event.state == DeviceEvent::State::Removed) {
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if (event.major_number == 30 && event.minor_number == 0 && !event.is_block_device) {
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dbgln("DeviceMapper: unregistering device failed: kcov tried to de-register itself!?");
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continue;
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}
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if (auto error_or_void = unregister_device(event.is_block_device ? DeviceNodeFamily::Type::BlockDevice : DeviceNodeFamily::Type::CharacterDevice, event.major_number, event.minor_number); error_or_void.is_error())
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dbgln("DeviceMapper: unregistering device failed: {}", error_or_void.error());
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} else {
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dbgln("DeviceMapper: Unhandled device event ({:x})!", event.state);
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}
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}
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VERIFY_NOT_REACHED();
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}
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}
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