Kernel: Add base support for VirtRNG (VirtIO based Hardware RNG)

This is a very basic implementation that only requests 4096 bytes
of entropy from the host once, but its still high quality entropy
so it should be a good fix for #4490 (boot-time entropy starvation)
for virtualized environments.

Co-authored-by: Sahan <sahan.h.fernando@gmail.com>

Kernel/CMakeLists.txt

@@ -223,6 +223,7 @@ set(KERNEL_SOURCES
     VirtIO/VirtIO.cpp
     VirtIO/VirtIOConsole.cpp
     VirtIO/VirtIOQueue.cpp
+    VirtIO/VirtIORNG.cpp
     VM/AnonymousVMObject.cpp
     VM/ContiguousVMObject.cpp
     VM/InodeVMObject.cpp

Kernel/VirtIO/VirtIO.cpp

@@ -26,6 +26,7 @@
 
 #include <Kernel/VirtIO/VirtIO.h>
 #include <Kernel/VirtIO/VirtIOConsole.h>
+#include <Kernel/VirtIO/VirtIORNG.h>
 
 namespace Kernel {
 
@@ -41,6 +42,10 @@ void VirtIO::detect()
             [[maybe_unused]] auto& unused = adopt(*new VirtIOConsole(address)).leak_ref();
             break;
         }
+        case VIRTIO_ENTROPY_PCI_DEVICE_ID: {
+            [[maybe_unused]] auto& unused = adopt(*new VirtIORNG(address)).leak_ref();
+            break;
+        }
         default:
             dbgln_if(VIRTIO_DEBUG, "VirtIO: Unknown VirtIO device with ID: {}", id.device_id);
             break;

Kernel/VirtIO/VirtIORNG.cpp

@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <Kernel/VirtIO/VirtIORNG.h>
+
+namespace Kernel {
+
+VirtIORNG::VirtIORNG(PCI::Address address)
+    : CharacterDevice(10, 183)
+    , VirtIODevice(address, "VirtIORNG")
+{
+    bool success = negotiate_features([&](auto) {
+        return 0;
+    });
+    if (success) {
+        success = setup_queues(1);
+    }
+    if (success) {
+        finish_init();
+        m_entropy_buffer = MM.allocate_contiguous_kernel_region(PAGE_SIZE, "VirtIORNG", Region::Access::Read | Region::Access::Write);
+        if (m_entropy_buffer) {
+            memset(m_entropy_buffer->vaddr().as_ptr(), 0, m_entropy_buffer->size());
+            supply_buffer_and_notify(REQUESTQ, ScatterGatherList::create_from_physical(m_entropy_buffer->physical_page(0)->paddr(), m_entropy_buffer->size()), BufferType::DeviceWritable, m_entropy_buffer->vaddr().as_ptr());
+        }
+    }
+}
+
+VirtIORNG::~VirtIORNG()
+{
+}
+
+bool VirtIORNG::handle_device_config_change()
+{
+    VERIFY_NOT_REACHED(); // Device has no config
+}
+
+void VirtIORNG::handle_queue_update(u16 queue_index)
+{
+    VERIFY(queue_index == REQUESTQ);
+    size_t available_entropy = 0;
+    if (!get_queue(REQUESTQ).get_buffer(&available_entropy))
+        return;
+    dbgln_if(VIRTIO_DEBUG, "VirtIORNG: received {} bytes of entropy!", available_entropy);
+    for (auto i = 0u; i < available_entropy; i++) {
+        m_entropy_source.add_random_event(m_entropy_buffer->vaddr().as_ptr()[i]);
+    }
+    // TODO: when should we ask for more entropy from the host?
+}
+
+}

Kernel/VirtIO/VirtIORNG.h

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <Kernel/Devices/CharacterDevice.h>
+#include <Kernel/Random.h>
+#include <Kernel/VirtIO/VirtIO.h>
+
+namespace Kernel {
+
+#define VIRTIO_ENTROPY_PCI_DEVICE_ID 0x1005
+
+#define REQUESTQ 0
+
+class VirtIORNG final : public CharacterDevice
+    , public VirtIODevice {
+public:
+    virtual const char* class_name() const override { return m_class_name.characters(); }
+
+    virtual bool can_read(const FileDescription&, size_t) const override { return false; }
+    virtual KResultOr<size_t> read(FileDescription&, u64, UserOrKernelBuffer&, size_t) override { return 0; }
+    virtual bool can_write(const FileDescription&, size_t) const override { return false; }
+    virtual KResultOr<size_t> write(FileDescription&, u64, const UserOrKernelBuffer&, size_t) override { return 0; }
+
+    virtual mode_t required_mode() const override { return 0666; }
+    virtual String device_name() const override { return "hwrng"; }
+
+    VirtIORNG(PCI::Address);
+    virtual ~VirtIORNG() override;
+
+private:
+    virtual bool handle_device_config_change() override;
+    virtual void handle_queue_update(u16 queue_index) override;
+
+    OwnPtr<Region> m_entropy_buffer;
+    EntropySource m_entropy_source;
+};
+
+}

Meta/run.sh

@@ -57,6 +57,7 @@ $SERENITY_EXTRA_QEMU_ARGS
 -chardev stdio,id=stdout,mux=on
 -device virtconsole,chardev=stdout
 -device isa-debugcon,chardev=stdout
+-device virtio-rng-pci
 -soundhw pcspk
 -device sb16
 "
@@ -77,6 +78,7 @@ $SERENITY_EXTRA_QEMU_ARGS
 -chardev stdio,id=stdout,mux=on
 -device virtconsole,chardev=stdout
 -device isa-debugcon,chardev=stdout
+-device virtio-rng-pci
 -soundhw pcspk
 -device sb16
 "