Kernel: Introduce the new ProcFS design

The new ProcFS design consists of two main parts:
1. The representative ProcFS class, which is derived from the FS class.
The ProcFS and its inodes are much more lean - merely 3 classes to
represent the common type of inodes - regular files, symbolic links and
directories. They're backed by a ProcFSExposedComponent object, which
is responsible for the functional operation behind the scenes.
2. The backend of the ProcFS - the ProcFSComponentsRegistrar class
and all derived classes from the ProcFSExposedComponent class. These
together form the entire backend and handle all the functions you can
expect from the ProcFS.

The ProcFSExposedComponent derived classes split to 3 types in the
manner of lifetime in the kernel:
1. Persistent objects - this category includes all basic objects, like
the root folder, /proc/bus folder, main blob files in the root folders,
etc. These objects are persistent and cannot die ever.
2. Semi-persistent objects - this category includes all PID folders,
and subdirectories to the PID folders. It also includes exposed objects
like the unveil JSON'ed blob. These object are persistent as long as the
the responsible process they represent is still alive.
3. Dynamic objects - this category includes files in the subdirectories
of a PID folder, like /proc/PID/fd/* or /proc/PID/stacks/*. Essentially,
these objects are always created dynamically and when no longer in need
after being used, they're deallocated.
Nevertheless, the new allocated backend objects and inodes try to use
the same InodeIndex if possible - this might change only when a thread
dies and a new thread is born with a new thread stack, or when a file
descriptor is closed and a new one within the same file descriptor
number is opened. This is needed to actually be able to do something
useful with these objects.

The new design assures that many ProcFS instances can be used at once,
with one backend for usage for all instances.

1 files changed, 159 insertions, 0 deletions

diff --git a/Kernel/Devices/USB/UHCIController.cpp b/Kernel/Devices/USB/UHCIController.cpp
index 153c825b58..9c68018c92 100644
--- a/Kernel/Devices/USB/UHCIController.cpp
+++ b/Kernel/Devices/USB/UHCIController.cpp
@@ -5,12 +5,17 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/JsonArray.h>
+#include <AK/JsonArraySerializer.h>
+#include <AK/JsonObjectSerializer.h>
 #include <AK/Platform.h>
 #include <Kernel/CommandLine.h>
 #include <Kernel/Debug.h>
 #include <Kernel/Devices/USB/UHCIController.h>
 #include <Kernel/Devices/USB/USBRequest.h>
+#include <Kernel/KBufferBuilder.h>
 #include <Kernel/Process.h>
+#include <Kernel/ProcessExposed.h>
 #include <Kernel/Sections.h>
 #include <Kernel/StdLib.h>
 #include <Kernel/Time/TimeManagement.h>
@@ -65,6 +70,144 @@ static constexpr u16 UHCI_PORTSC_SUSPEND = 0x1000;
 static constexpr u8 UHCI_NUMBER_OF_ISOCHRONOUS_TDS = 128;
 static constexpr u16 UHCI_NUMBER_OF_FRAMES = 1024;
 
+class ProcFSUSBBusFolder;
+static ProcFSUSBBusFolder* s_procfs_usb_bus_folder;
+
+class ProcFSUSBDeviceInformation : public ProcFSGlobalInformation {
+    friend class ProcFSUSBBusFolder;
+
+public:
+    virtual ~ProcFSUSBDeviceInformation() override {};
+
+    static NonnullRefPtr<ProcFSUSBDeviceInformation> create(USB::Device&);
+
+    RefPtr<USB::Device> device() const { return m_device; }
+
+protected:
+    explicit ProcFSUSBDeviceInformation(USB::Device& device)
+        : ProcFSGlobalInformation(String::formatted("{}", device.address()))
+        , m_device(device)
+    {
+    }
+    virtual bool output(KBufferBuilder& builder) override
+    {
+        VERIFY(m_device); // Something has gone very wrong if this isn't true
+
+        JsonArraySerializer array { builder };
+
+        auto obj = array.add_object();
+        obj.add("usb_spec_compliance_bcd", m_device->device_descriptor().usb_spec_compliance_bcd);
+        obj.add("device_class", m_device->device_descriptor().device_class);
+        obj.add("device_sub_class", m_device->device_descriptor().device_sub_class);
+        obj.add("device_protocol", m_device->device_descriptor().device_protocol);
+        obj.add("max_packet_size", m_device->device_descriptor().max_packet_size);
+        obj.add("vendor_id", m_device->device_descriptor().vendor_id);
+        obj.add("product_id", m_device->device_descriptor().product_id);
+        obj.add("device_release_bcd", m_device->device_descriptor().device_release_bcd);
+        obj.add("manufacturer_id_descriptor_index", m_device->device_descriptor().manufacturer_id_descriptor_index);
+        obj.add("product_string_descriptor_index", m_device->device_descriptor().product_string_descriptor_index);
+        obj.add("serial_number_descriptor_index", m_device->device_descriptor().serial_number_descriptor_index);
+        obj.add("num_configurations", m_device->device_descriptor().num_configurations);
+        obj.finish();
+        array.finish();
+        return true;
+    }
+    IntrusiveListNode<ProcFSUSBDeviceInformation, RefPtr<ProcFSUSBDeviceInformation>> m_list_node;
+    RefPtr<USB::Device> m_device;
+};
+
+class ProcFSUSBBusFolder final : public ProcFSExposedFolder {
+    friend class ProcFSComponentsRegistrar;
+
+public:
+    static void initialize();
+    void plug(USB::Device&);
+    void unplug(USB::Device&);
+
+    virtual KResultOr<size_t> entries_count() const override;
+    virtual KResult traverse_as_directory(unsigned, Function<bool(const FS::DirectoryEntryView&)>) const override;
+    virtual RefPtr<ProcFSExposedComponent> lookup(StringView name) override;
+
+private:
+    ProcFSUSBBusFolder(const ProcFSBusDirectory&);
+
+    RefPtr<ProcFSUSBDeviceInformation> device_node_for(USB::Device& device);
+
+    IntrusiveList<ProcFSUSBDeviceInformation, RefPtr<ProcFSUSBDeviceInformation>, &ProcFSUSBDeviceInformation::m_list_node> m_device_nodes;
+    mutable SpinLock<u8> m_lock;
+};
+
+KResultOr<size_t> ProcFSUSBBusFolder::entries_count() const
+{
+    ScopedSpinLock lock(m_lock);
+    return m_device_nodes.size_slow();
+}
+KResult ProcFSUSBBusFolder::traverse_as_directory(unsigned fsid, Function<bool(const FS::DirectoryEntryView&)> callback) const
+{
+    ScopedSpinLock lock(m_lock);
+    VERIFY(m_parent_folder);
+    callback({ ".", { fsid, component_index() }, 0 });
+    callback({ "..", { fsid, m_parent_folder->component_index() }, 0 });
+
+    for (auto& device_node : m_device_nodes) {
+        InodeIdentifier identifier = { fsid, device_node.component_index() };
+        callback({ device_node.name(), identifier, 0 });
+    }
+    return KSuccess;
+}
+RefPtr<ProcFSExposedComponent> ProcFSUSBBusFolder::lookup(StringView name)
+{
+    ScopedSpinLock lock(m_lock);
+    for (auto& device_node : m_device_nodes) {
+        if (device_node.name() == name) {
+            return device_node;
+        }
+    }
+    return {};
+}
+
+RefPtr<ProcFSUSBDeviceInformation> ProcFSUSBBusFolder::device_node_for(USB::Device& device)
+{
+    RefPtr<USB::Device> checked_device = device;
+    for (auto& device_node : m_device_nodes) {
+        if (device_node.device().ptr() == checked_device.ptr())
+            return device_node;
+    }
+    return {};
+}
+
+void ProcFSUSBBusFolder::plug(USB::Device& new_device)
+{
+    ScopedSpinLock lock(m_lock);
+    auto device_node = device_node_for(new_device);
+    VERIFY(!device_node);
+    m_device_nodes.append(ProcFSUSBDeviceInformation::create(new_device));
+}
+void ProcFSUSBBusFolder::unplug(USB::Device& deleted_device)
+{
+    ScopedSpinLock lock(m_lock);
+    auto device_node = device_node_for(deleted_device);
+    VERIFY(device_node);
+    device_node->m_list_node.remove();
+}
+
+UNMAP_AFTER_INIT ProcFSUSBBusFolder::ProcFSUSBBusFolder(const ProcFSBusDirectory& buses_folder)
+    : ProcFSExposedFolder("usb"sv, buses_folder)
+{
+}
+
+UNMAP_AFTER_INIT void ProcFSUSBBusFolder::initialize()
+{
+    auto folder = adopt_ref(*new ProcFSUSBBusFolder(ProcFSComponentsRegistrar::the().buses_folder()));
+    ProcFSComponentsRegistrar::the().register_new_bus_folder(folder);
+    s_procfs_usb_bus_folder = folder;
+}
+
+NonnullRefPtr<ProcFSUSBDeviceInformation> ProcFSUSBDeviceInformation::create(USB::Device& device)
+{
+    return adopt_ref(*new ProcFSUSBDeviceInformation(device));
+}
+
 UHCIController& UHCIController::the()
 {
     return *s_the;
@@ -75,6 +218,10 @@ UNMAP_AFTER_INIT void UHCIController::detect()
     if (kernel_command_line().disable_uhci_controller())
         return;
 
+    // FIXME: We create the /proc/bus/usb representation here, but it should really be handled
+    // in a more broad singleton than this once we refactor things in USB subsystem.
+    ProcFSUSBBusFolder::initialize();
+
     PCI::enumerate([&](const PCI::Address& address, PCI::ID id) {
         if (address.is_null())
             return;
@@ -569,8 +716,14 @@ void UHCIController::spawn_port_proc()
                                 dmesgln("UHCI: Device creation failed on port 1 ({})", device.error());
 
                             m_devices.at(0) = device.value();
+                            VERIFY(s_procfs_usb_bus_folder);
+                            s_procfs_usb_bus_folder->plug(device.value());
                         } else {
+                            // FIXME: Clean up (and properly) the RefPtr to the device in m_devices
+                            VERIFY(s_procfs_usb_bus_folder);
+                            VERIFY(m_devices.at(0));
                             dmesgln("UHCI: Device detach detected on Root Port 1");
+                            s_procfs_usb_bus_folder->unplug(*m_devices.at(0));
                         }
                     }
                 } else {
@@ -601,8 +754,14 @@ void UHCIController::spawn_port_proc()
                                 dmesgln("UHCI: Device creation failed on port 2 ({})", device.error());
 
                             m_devices.at(1) = device.value();
+                            VERIFY(s_procfs_usb_bus_folder);
+                            s_procfs_usb_bus_folder->plug(device.value());
                         } else {
+                            // FIXME: Clean up (and properly) the RefPtr to the device in m_devices
+                            VERIFY(s_procfs_usb_bus_folder);
+                            VERIFY(m_devices.at(1));
                             dmesgln("UHCI: Device detach detected on Root Port 2");
+                            s_procfs_usb_bus_folder->unplug(*m_devices.at(1));
                         }
                     }
                 }