Kernel/LibC: Add basic pipe() syscall and command

You can now create pipes :)

kernel/include/kernel/FS/Inode.h

@@ -76,6 +76,7 @@ namespace Kernel
 		virtual dev_t rdev() const = 0;
 
 		virtual bool is_device() const { return false; }
+		virtual bool is_pipe() const { return false; }
 
 		virtual BAN::StringView name() const = 0;
 

kernel/include/kernel/FS/Pipe.h

@@ -0,0 +1,54 @@
+#pragma once
+
+#include <kernel/FS/Inode.h>
+#include <kernel/Semaphore.h>
+#include <kernel/SpinLock.h>
+
+namespace Kernel
+{
+
+	class Pipe : public Inode
+	{
+	public:
+		static BAN::ErrorOr<BAN::RefPtr<Inode>> create(const Credentials&);
+
+		virtual bool is_pipe() const override { return true; }
+		void clone_writing();
+		void close_writing();
+
+		virtual ino_t ino() const override { return 0; } // FIXME
+		virtual Mode mode() const override { return { Mode::IFIFO | Mode::IRUSR | Mode::IWUSR }; }
+		virtual nlink_t nlink() const override { return 1; }
+		virtual uid_t uid() const override { return m_uid; }
+		virtual gid_t gid() const override { return m_gid; }
+		virtual off_t size() const override { return 0; }
+		virtual timespec atime() const override { return m_atime; }
+		virtual timespec mtime() const override { return m_mtime; }
+		virtual timespec ctime() const override { return m_ctime; }
+		virtual blksize_t blksize() const override { return 4096; }
+		virtual blkcnt_t blocks() const override { return 0; }
+		virtual dev_t dev() const override { return 0; } // FIXME
+		virtual dev_t rdev() const override { return 0; } // FIXME
+
+		virtual BAN::StringView name() const override { return ""sv; }
+
+		virtual BAN::ErrorOr<size_t> read(size_t, void*, size_t) override;
+		virtual BAN::ErrorOr<size_t> write(size_t, const void*, size_t) override;
+
+	private:
+		Pipe(const Credentials&);
+
+	private:
+		const uid_t m_uid;
+		const gid_t m_gid;
+		timespec m_atime {};
+		timespec m_mtime {};
+		timespec m_ctime {};
+		BAN::Vector<uint8_t> m_buffer;
+		SpinLock m_lock;
+		Semaphore m_semaphore;
+
+		uint32_t m_writing_count { 1 };
+	};
+
+}

kernel/include/kernel/Process.h

@@ -84,6 +84,8 @@ namespace Kernel
 		BAN::ErrorOr<long> sys_write(int fd, const void* buffer, size_t count);
 		BAN::ErrorOr<long> sys_creat(BAN::StringView name, mode_t);
 
+		BAN::ErrorOr<long> sys_pipe(int fildes[2]);
+
 		BAN::ErrorOr<long> sys_seek(int fd, off_t offset, int whence);
 		BAN::ErrorOr<long> sys_tell(int fd);
 
@@ -136,6 +138,7 @@ namespace Kernel
 		BAN::ErrorOr<void> validate_fd(int);
 		OpenFileDescription& open_file_description(int);
 		BAN::ErrorOr<int> get_free_fd();
+		BAN::ErrorOr<void> get_free_fd_pair(int fds[2]);
 
 
 		struct ExitStatus