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DeviceMapper: Add a mechanism to handle pluggable-once char devices

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Liav A 2023-09-23 21:50:57 +03:00 committed by Tim Schumacher
parent a30939feba
commit ac70abcb73
Notes: sideshowbarker 2024-07-17 17:40:13 +09:00 
Author: https://github.com/supercomputer7
Commit: https://github.com/SerenityOS/serenity/commit/ac70abcb73
Pull-request: https://github.com/SerenityOS/serenity/pull/20761
Reviewed-by: https://github.com/timschumi ✅
1 changed files with 32 additions and 9 deletions
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41
Userland/Services/DeviceMapper/DeviceEventLoop.cpp
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@ -186,11 +186,22 @@ ErrorOr<void> DeviceEventLoop::unregister_device(DeviceNodeFamily::Type unix_dev
return {};
}
static ErrorOr<void> create_kcov_device_node()
struct PluggableOnceCharacterDeviceNodeMatch {
StringView path;
mode_t mode;
MajorNumber major;
MinorNumber minor;
};
static constexpr PluggableOnceCharacterDeviceNodeMatch s_simple_matchers[] = {
{ "/dev/kcov"sv, 0666, 30, 0 },
};
static ErrorOr<void> create_pluggable_once_char_device_node(PluggableOnceCharacterDeviceNodeMatch const& match)
{
mode_t old_mask = umask(0);
ScopeGuard umask_guard([old_mask] { umask(old_mask); });
TRY(Core::System::create_char_device("/dev/kcov"sv, 0666, 30, 0));
TRY(Core::System::create_char_device(match.path, match.mode, match.major.value(), match.minor.value()));
return {};
}
@ -216,14 +227,26 @@ ErrorOr<void> DeviceEventLoop::drain_events_from_devctl()
continue;
if (event.state == DeviceEvent::State::Inserted) {
// NOTE: We have a special function for the KCOV device, because we don't
// want to create a new MinorNumberAllocationType (e.g. SingleInstance).
// Instead, just blindly create that device node and assume we will never
// have to worry about it, so we don't need to register that!
if (event.major_number == 30 && event.minor_number == 0 && !event.is_block_device) {
TRY(create_kcov_device_node());
continue;
if (!event.is_block_device) {
// NOTE: We have a special handling for the pluggable-once devices, etc,
// as these device (if they appear) should only "hotplug" (being inserted)
// once during the OS runtime.
// Therefore, we don't want to create a new MinorNumberAllocationType (e.g. SingleInstance).
// Instead, just blindly create such device node and assume we will never
// have to worry about it, so we don't need to register that!
auto possible_pluggable_once_char_device_match = ([](DeviceEvent& event) -> Optional<PluggableOnceCharacterDeviceNodeMatch const&> {
for (auto const& match : s_simple_matchers) {
if (event.major_number == match.major.value() && event.minor_number == match.minor.value())
return match;
}
return Optional<PluggableOnceCharacterDeviceNodeMatch const&> {};
})(event);
if (possible_pluggable_once_char_device_match.has_value()) {
TRY(create_pluggable_once_char_device_node(possible_pluggable_once_char_device_match.value()));
continue;
}
}
VERIFY(event.is_block_device == 1 || event.is_block_device == 0);
TRY(register_new_device(event.is_block_device ? DeviceNodeFamily::Type::BlockDevice : DeviceNodeFamily::Type::CharacterDevice, event.major_number, event.minor_number));
} else if (event.state == DeviceEvent::State::Removed) {