Kernel: Implement basic random device to /dev/random

kernel/CMakeLists.txt

@@ -20,6 +20,7 @@ set(KERNEL_SOURCES
 	kernel/Device/Device.cpp
 	kernel/Device/FramebufferDevice.cpp
 	kernel/Device/NullDevice.cpp
+	kernel/Device/RandomDevice.cpp
 	kernel/Device/ZeroDevice.cpp
 	kernel/Errors.cpp
 	kernel/FS/DevFS/FileSystem.cpp

kernel/include/kernel/Device/DeviceNumbers.h

@@ -12,6 +12,7 @@ namespace Kernel
 		PTSMaster,
 		Null,
 		Zero,
+		Random,
 		Debug,
 		Keyboard,
 		Mouse,

kernel/include/kernel/Device/RandomDevice.h

@@ -0,0 +1,32 @@
+#include <kernel/Device/Device.h>
+
+namespace Kernel
+{
+
+	class RandomDevice : public CharacterDevice
+	{
+	public:
+		static BAN::ErrorOr<BAN::RefPtr<RandomDevice>> create(mode_t, uid_t, gid_t);
+
+		virtual dev_t rdev() const override { return m_rdev; }
+
+		virtual BAN::StringView name() const override { return "random"_sv; }
+
+	protected:
+		RandomDevice(mode_t mode, uid_t uid, gid_t gid, dev_t rdev)
+			: CharacterDevice(mode, uid, gid)
+			, m_rdev(rdev)
+		{ }
+
+		virtual BAN::ErrorOr<size_t> read_impl(off_t, BAN::ByteSpan) override;
+		virtual BAN::ErrorOr<size_t> write_impl(off_t, BAN::ConstByteSpan buffer) override { return buffer.size(); };
+
+		virtual bool can_read_impl() const override { return true; }
+		virtual bool can_write_impl() const override { return false; }
+		virtual bool has_error_impl() const override { return false; }
+
+	private:
+		const dev_t m_rdev;
+	};
+
+}

kernel/kernel/Device/RandomDevice.cpp

@@ -0,0 +1,32 @@
+#include <kernel/Device/DeviceNumbers.h>
+#include <kernel/Device/RandomDevice.h>
+#include <kernel/Random.h>
+
+#include <sys/sysmacros.h>
+
+namespace Kernel
+{
+
+	BAN::ErrorOr<BAN::RefPtr<RandomDevice>> RandomDevice::create(mode_t mode, uid_t uid, gid_t gid)
+	{
+		static uint32_t minor = 0;
+		auto* result = new RandomDevice(mode, uid, gid, makedev(DeviceNumber::Random, minor++));
+		if (result == nullptr)
+			return BAN::Error::from_errno(ENOMEM);
+		return BAN::RefPtr<RandomDevice>::adopt(result);
+	}
+
+	BAN::ErrorOr<size_t> RandomDevice::read_impl(off_t, BAN::ByteSpan buffer)
+	{
+		size_t nwritten = 0;
+		while (nwritten < buffer.size())
+		{
+			const uint64_t random = Random::get_u64();
+			const size_t to_copy = BAN::Math::min(buffer.size() - nwritten, sizeof(random));
+			memcpy(buffer.data() + nwritten, &random, to_copy);
+			nwritten += to_copy;
+		}
+		return buffer.size();
+	}
+
+}

kernel/kernel/FS/DevFS/FileSystem.cpp

@@ -2,6 +2,7 @@
 #include <kernel/Device/DebugDevice.h>
 #include <kernel/Device/FramebufferDevice.h>
 #include <kernel/Device/NullDevice.h>
+#include <kernel/Device/RandomDevice.h>
 #include <kernel/Device/ZeroDevice.h>
 #include <kernel/FS/DevFS/FileSystem.h>
 #include <kernel/FS/TmpFS/Inode.h>
@@ -26,6 +27,7 @@ namespace Kernel
 		MUST(s_instance->TmpFileSystem::initialize(0755, 0, 0));
 		s_instance->add_device(MUST(DebugDevice::create(0666, 0, 0)));
 		s_instance->add_device(MUST(NullDevice::create(0666, 0, 0)));
+		s_instance->add_device(MUST(RandomDevice::create(0666, 0, 0)));
 		s_instance->add_device(MUST(ZeroDevice::create(0666, 0, 0)));
 		s_instance->add_device(MUST(KeyboardDevice::create(0440, 0, 901)));
 		s_instance->add_device(MUST(MouseDevice::create(0440, 0, 901)));