Headers for Virtual File System (VFS). More...

Macros
#define	MAX_OPEN_FD 16
	Maximum number of opened file.

Functions
void	vfs_init (void)
	Initialize the Virtual File System (VFS). This function sets up necessary resources and structures for the VFS. It must be called before any other VFS functions.

int	vfs_register_filesystem (file_system_type *fs)
	Register a new filesystem. More...

int	vfs_unregister_filesystem (file_system_type *fs)
	Unregister a new filesystem. More...

int	vfs_register_superblock (const char name, const char path, file_system_type type, vfs_file_t root)
	Register a superblock for the filesystem. More...

int	vfs_unregister_superblock (super_block_t *sb)
	Unregister a superblock. More...

super_block_t *	vfs_get_superblock (const char *absolute_path)
	Searches for the mountpoint of the given path. More...

vfs_file_t *	vfs_open_abspath (const char *absolute_path, int flags, mode_t mode)
	Open a file given its absolute path. More...

vfs_file_t *	vfs_open (const char *path, int flags, mode_t mode)
	Given a pathname for a file, vfs_open() returns a file struct, used to access the file. More...

int	vfs_close (vfs_file_t *file)
	Decreases the number of references to a given file, if the references number reaches 0, close the file. More...

ssize_t	vfs_read (vfs_file_t file, void buf, size_t offset, size_t nbytes)
	Read data from a file. More...

ssize_t	vfs_write (vfs_file_t file, const void buf, size_t offset, size_t nbytes)
	Write data to a file. More...

off_t	vfs_lseek (vfs_file_t *file, off_t offset, int whence)
	Repositions the file offset inside a file. More...

ssize_t	vfs_getdents (vfs_file_t file, dirent_t dirp, off_t off, size_t count)

int	vfs_ioctl (vfs_file_t file, int request, void data)
	Perform the I/O control operation specified by REQUEST on FD. One argument may follow; its presence and type depend on REQUEST. More...

int	vfs_unlink (const char *path)
	Delete a name and possibly the file it refers to. More...

int	vfs_mkdir (const char *path, mode_t mode)
	Creates a new directory at the given path. More...

int	vfs_rmdir (const char *path)
	Removes the given directory. More...

vfs_file_t *	vfs_creat (const char *path, mode_t mode)
	Creates a new file or rewrite an existing one. More...

ssize_t	vfs_readlink (const char path, char buffer, size_t bufsize)
	Read the symbolic link, if present. More...

int	vfs_symlink (const char linkname, const char path)
	Creates a symbolic link. More...

int	vfs_stat (const char path, stat_t buf)
	Stat the file at the given path. More...

int	vfs_fstat (vfs_file_t file, stat_t buf)
	Stat the given file. More...

int	vfs_mount (const char type, const char path, const char *args)
	Mount the path as a filesystem of the given type. More...

void	vfs_lock (vfs_file_t *file)
	Locks the access to the given file. More...

int	vfs_extend_task_fd_list (struct task_struct *task)
	Extends the file descriptor list for the given task. More...

int	vfs_init_task (struct task_struct *task)
	Initialize the file descriptor list for the given task. More...

int	vfs_dup_task (struct task_struct new_task, struct task_struct old_task)
	Duplicate the file descriptor list of old_task into new_task. More...

int	vfs_destroy_task (struct task_struct *task)
	Destroy the file descriptor list for the given task. More...

int	get_unused_fd (void)
	Find the smallest available fd. More...

int	sys_dup (int fd)
	Return new smallest available file desriptor. More...

int	vfs_valid_open_permissions (int flags, mode_t mask, uid_t uid, gid_t gid)
	Check if the requested open flags against the file mask. More...

int	vfs_valid_exec_permission (struct task_struct task, vfs_file_t file)
	Check if the file is exectuable. More...

Variables
kmem_cache_t *	vfs_file_cache
	Cache for file structures in the VFS. More...

Detailed Description

Headers for Virtual File System (VFS).

Copyright: (c) 2014-2024 This file is distributed under the MIT License. See LICENSE.md for details.

Function Documentation

◆ get_unused_fd()

int get_unused_fd ( void )

Find the smallest available fd.

Returns: -errno on fail, fd on success.

◆ sys_dup()

int sys_dup ( int fd )

Return new smallest available file desriptor.

Parameters

fd	the descriptor of the file we want to duplicate.

Returns: -errno on fail, fd on success.

◆ vfs_close()

int vfs_close ( vfs_file_t * file )

Decreases the number of references to a given file, if the references number reaches 0, close the file.

Parameters

file	A pointer to the file structure.

Returns: The result of the call.

◆ vfs_creat()

vfs_file_t* vfs_creat	(	const char *	path,
		mode_t	mode
	)

Creates a new file or rewrite an existing one.

Parameters

path	path to the file.
mode	mode for file creation.

Returns: file descriptor number, -1 otherwise and errno is set to indicate the error.

It is equivalent to: open(path, O_WRONLY|O_CREAT|O_TRUNC, mode)

◆ vfs_destroy_task()

int vfs_destroy_task ( struct task_struct * task )

Destroy the file descriptor list for the given task.

Parameters

task	The task for which we destroy the file descriptor list.

Returns: 0 on fail, 1 on success.

◆ vfs_dup_task()

int vfs_dup_task	(	struct task_struct *	new_task,
		struct task_struct *	old_task
	)

Duplicate the file descriptor list of old_task into new_task.

Parameters

new_task	The task where we clone the file descriptor list.
old_task	The task from which we clone the file descriptor list.

Returns: 0 on fail, 1 on success.

◆ vfs_extend_task_fd_list()

int vfs_extend_task_fd_list ( struct task_struct * task )

Extends the file descriptor list for the given task.

Parameters

task	The task for which we extend the file descriptor list.

Returns: 0 on fail, 1 on success.

◆ vfs_fstat()

int vfs_fstat	(	vfs_file_t *	file,
		stat_t *	buf
	)

Stat the given file.

Parameters

file	Pointer to the file for which we are retrieving the statistics.
buf	Buffer where we are storing the statistics.

Returns: 0 on success, -errno on failure.

◆ vfs_get_superblock()

super_block_t* vfs_get_superblock ( const char * absolute_path )

Searches for the mountpoint of the given path.

Parameters

absolute_path Path for which we want to search the mountpoint.

Returns: Pointer to the super_block_t of the mountpoint, or NULL if not found.

◆ vfs_getdents()

ssize_t vfs_getdents	(	vfs_file_t *	file,
		dirent_t *	dirp,
		off_t	off,
		size_t	count
	)

Provide access to the directory entries.

Parameters

file	The directory for which we accessing the entries.
dirp	The buffer where de data should be placed.
off	The offset from which we start reading the entries.
count	The size of the buffer.

Returns: On success, the number of bytes read is returned. On end of directory, 0 is returned. On error, -1 is returned, and errno is set appropriately.

◆ vfs_init_task()

int vfs_init_task ( struct task_struct * task )

Initialize the file descriptor list for the given task.

Parameters

task	The task for which we initialize the file descriptor list.

Returns: 0 on fail, 1 on success.

◆ vfs_ioctl()

int vfs_ioctl	(	vfs_file_t *	file,
		int	request,
		void *	data
	)

Perform the I/O control operation specified by REQUEST on FD. One argument may follow; its presence and type depend on REQUEST.

Parameters

file	The file for which we are executing the operations.
request	The device-dependent request code
data	An untyped pointer to memory.

Returns: Return value depends on REQUEST. Usually -1 indicates error.

◆ vfs_lock()

void vfs_lock ( vfs_file_t * file )

Locks the access to the given file.

Parameters

file	The file to lock.

◆ vfs_lseek()

off_t vfs_lseek	(	vfs_file_t *	file,
		off_t	offset,
		int	whence
	)

Repositions the file offset inside a file.

Parameters

file	The file for which we reposition the offest.
offset	The offest to use for the operation.
whence	The type of operation.

Returns: Upon successful completion, returns the resulting offset location as measured in bytes from the beginning of the file. On error, the value (off_t) -1 is returned and errno is set to indicate the error.

◆ vfs_mkdir()

int vfs_mkdir	(	const char *	path,
		mode_t	mode
	)

Creates a new directory at the given path.

Parameters

path	The path of the new directory.
mode	The permission of the new directory.

Returns: Returns a negative value on failure.

◆ vfs_mount()

int vfs_mount	(	const char *	type,
		const char *	path,
		const char *	args
	)

Mount the path as a filesystem of the given type.

Parameters

type	The type of filesystem
path	The path to where it should be mounter.
args	The arguments passed to the filesystem mount callback.

Returns: 0 on success, a negative number if fails and errno is set.

◆ vfs_open()

vfs_file_t* vfs_open	(	const char *	path,
		int	flags,
		mode_t	mode
	)

Given a pathname for a file, vfs_open() returns a file struct, used to access the file.

Parameters

path	A pathname for a file.
flags	Used to set the file status flags and file access modes of the open file description.
mode	Specifies the file mode bits be applied when a new file is created.

Returns: Returns a file struct, or NULL.

◆ vfs_open_abspath()

vfs_file_t* vfs_open_abspath	(	const char *	absolute_path,
		int	flags,
		mode_t	mode
	)

Open a file given its absolute path.

Parameters

absolute_path	An absolute path to the file.
flags	Used to set the file status flags and access modes.
mode	Specifies the file mode bits to apply when creating a new file.

Returns: Pointer to the opened vfs_file_t structure, or NULL on error.

◆ vfs_read()

ssize_t vfs_read	(	vfs_file_t *	file,
		void *	buf,
		size_t	offset,
		size_t	nbytes
	)

Read data from a file.

Parameters

file	The file structure used to reference a file.
buf	The buffer.
offset	The offset from which the function starts to read.
nbytes	The number of bytes to read.

Returns: The number of read characters.

◆ vfs_readlink()

ssize_t vfs_readlink	(	const char *	path,
		char *	buffer,
		size_t	bufsize
	)

Read the symbolic link, if present.

Parameters

path	the path to the symbolic link.
buffer	the buffer where we will store the symbolic link path.
bufsize	the size of the buffer.

Returns: The number of read characters on success, -1 otherwise and errno is set to indicate the error.

◆ vfs_register_filesystem()

int vfs_register_filesystem ( file_system_type * fs )

Register a new filesystem.

Parameters

fs	A pointer to the information concerning the new filesystem.

Returns: The outcome of the operation, 0 if fails.

◆ vfs_register_superblock()

int vfs_register_superblock	(	const char *	name,
		const char *	path,
		file_system_type *	type,
		vfs_file_t *	root
	)

Register a superblock for the filesystem.

Parameters

name	The name of the superblock.
path	The path associated with the superblock.
type	A pointer to the filesystem type.
root	A pointer to the root file of the filesystem.

Returns: 1 on success, 0 on failure.

◆ vfs_rmdir()

int vfs_rmdir ( const char * path )

Removes the given directory.

Parameters

path	The path to the directory to remove.

Returns: Returns a negative value on failure.

◆ vfs_stat()

int vfs_stat	(	const char *	path,
		stat_t *	buf
	)

Stat the file at the given path.

Parameters

path	Path to the file for which we are retrieving the statistics.
buf	Buffer where we are storing the statistics.

Returns: 0 on success, -errno on failure.

◆ vfs_symlink()

int vfs_symlink	(	const char *	linkname,
		const char *	path
	)

Creates a symbolic link.

Parameters

linkname	the name of the link.
path	the entity it is linking to.

Returns: 0 on success, a negative number if fails and errno is set.

◆ vfs_unlink()

int vfs_unlink ( const char * path )

Delete a name and possibly the file it refers to.

Parameters

path	The path to the file.

Returns: On success, zero is returned. On error, -1 is returned, and errno is set appropriately.

◆ vfs_unregister_filesystem()

int vfs_unregister_filesystem ( file_system_type * fs )

Unregister a new filesystem.

Parameters

fs	A pointer to the information concerning the filesystem.

Returns: The outcome of the operation, 0 if fails.

◆ vfs_unregister_superblock()

int vfs_unregister_superblock ( super_block_t * sb )

Unregister a superblock.

Parameters

sb	A pointer to the superblock to unregister.

Returns: 1 on success, 0 on failure.

◆ vfs_valid_exec_permission()

int vfs_valid_exec_permission	(	struct task_struct *	task,
		vfs_file_t *	file
	)

Check if the file is exectuable.

Parameters

task	The task to execute the file.
file	The file to execute.

Returns: 0 on fail, 1 on success.

◆ vfs_valid_open_permissions()

int vfs_valid_open_permissions	(	int	flags,
		mode_t	mask,
		uid_t	uid,
		gid_t	gid
	)

Check if the requested open flags against the file mask.

Parameters

flags	The requested open flags.
mask	The permissions of the file.
uid	The owner of the task opening the file.
gid	The group of the task opening the file.

Returns: 0 on fail, 1 on success.

◆ vfs_write()

ssize_t vfs_write	(	vfs_file_t *	file,
		const void *	buf,
		size_t	offset,
		size_t	nbytes
	)

Write data to a file.

Parameters

file	The file structure used to reference a file.
buf	The buffer.
offset	The offset from which the function starts to write.
nbytes	The number of bytes to write.

Returns: The number of written characters.

Variable Documentation

◆ vfs_file_cache

kmem_cache_t* vfs_file_cache

extern

Cache for file structures in the VFS.

Macros

Functions

Variables

Detailed Description

Function Documentation

◆ get_unused_fd()

◆ sys_dup()

◆ vfs_close()

◆ vfs_creat()

◆ vfs_destroy_task()

◆ vfs_dup_task()

◆ vfs_extend_task_fd_list()

◆ vfs_fstat()

◆ vfs_get_superblock()

◆ vfs_getdents()

◆ vfs_init_task()

◆ vfs_ioctl()

◆ vfs_lock()

◆ vfs_lseek()

◆ vfs_mkdir()

◆ vfs_mount()

◆ vfs_open()

◆ vfs_open_abspath()

◆ vfs_read()

◆ vfs_readlink()

◆ vfs_register_filesystem()

◆ vfs_register_superblock()

◆ vfs_rmdir()

◆ vfs_stat()

◆ vfs_symlink()

◆ vfs_unlink()

◆ vfs_unregister_filesystem()

◆ vfs_unregister_superblock()

◆ vfs_valid_exec_permission()

◆ vfs_valid_open_permissions()

◆ vfs_write()

Variable Documentation

◆ vfs_file_cache