haiku/src/kernel/core/fd.c

/* Operations on file descriptors
** 
** Copyright 2002, Axel Dörfler, axeld@pinc-software.de. All rights reserved.
** Distributed under the terms of the OpenBeOS License.
*/


#include <fd.h>

#include <OS.h>
#include <Errors.h>

#include <vfs.h>
#include <debug.h>

#include <malloc.h>
#include <string.h>

#define CHECK_USER_ADDR(x) \
	if ((addr)(x) >= KERNEL_BASE && (addr)(x) <= KERNEL_TOP) \
		return B_BAD_ADDRESS;

#define TRACE_FD 0
#if TRACE_FD
#	define TRACE(x) dprintf x
#	define PRINT(x) dprintf x
#else
#	define TRACE(x)
#	define PRINT(x)
#endif


/*** General fd routines ***/


#ifdef DEBUG
void dump_fd(int fd, struct file_descriptor *descriptor);

void
dump_fd(int fd,struct file_descriptor *descriptor)
{
	dprintf("fd[%d] = %p: type = %d, ref_count = %d, ops = %p, vnode = %p, cookie = %p, dummy = %x\n",
		fd, descriptor, descriptor->type, descriptor->ref_count, descriptor->ops,
		descriptor->vnode, descriptor->cookie, descriptor->dummy);
}
#endif

/** Allocates and initializes a new file_descriptor */

struct file_descriptor *
alloc_fd(void)
{
	struct file_descriptor *descriptor;

	descriptor = malloc(sizeof(struct file_descriptor));
	if (descriptor == NULL)
		return NULL;

	descriptor->u.vnode = NULL;
	descriptor->cookie = NULL;
	descriptor->ref_count = 1;
	descriptor->open_mode = 0;
	descriptor->pos = 0;

	return descriptor;
}


int
new_fd(struct io_context *context, struct file_descriptor *descriptor)
{
	int fd = -1;
	int i;

	mutex_lock(&context->io_mutex);

	for (i = 0; i < context->table_size; i++) {
		if (!context->fds[i]) {
			fd = i;
			break;
		}
	}
	if (fd < 0) {
		fd = B_NO_MORE_FDS;
		goto err;
	}

	context->fds[fd] = descriptor;
	context->num_used_fds++;

err:
	mutex_unlock(&context->io_mutex);

	return fd;
}


/**	Reduces the descriptor's reference counter, and frees all resources
 *	if necessary.
 */

void
put_fd(struct file_descriptor *descriptor)
{
	// free the descriptor if we don't need it anymore
	if (atomic_add(&descriptor->ref_count, -1) == 1) {
		// close the underlying object (and free any resources allocated there)=
		if (descriptor->ops->fd_close)
			descriptor->ops->fd_close(descriptor);
		if (descriptor->ops->fd_free)
			descriptor->ops->fd_free(descriptor);

		free(descriptor);
	}
}


struct file_descriptor *
get_fd(struct io_context *context, int fd)
{
	struct file_descriptor *descriptor = NULL;

	if (fd < 0)
		return NULL;

	mutex_lock(&context->io_mutex);

	if (fd < context->table_size)
		descriptor = context->fds[fd];
	
	if (descriptor != NULL) // fd is valid
		atomic_add(&descriptor->ref_count, 1);

	mutex_unlock(&context->io_mutex);

	return descriptor;
}


/**	Removes the file descriptor in the specified slot, and
 *	reduces its reference counter.
 */

static void
remove_fd(struct io_context *context, int fd)
{
	struct file_descriptor *descriptor = NULL;

	if (fd < 0)
		return;

	mutex_lock(&context->io_mutex);

	if (fd < context->table_size)
		descriptor = context->fds[fd];

	if (descriptor)	{	// fd is valid
		context->fds[fd] = NULL;
		context->num_used_fds--;
	}

	mutex_unlock(&context->io_mutex);

	if (descriptor)
		put_fd(descriptor);
}


static int
dup_fd(int fd, bool kernel)
{
	struct io_context *context = get_current_io_context(kernel);
	struct file_descriptor *descriptor;
	int status;

	TRACE(("dup_fd: fd = %d\n", fd));

	// Try to get the fd structure
	descriptor = get_fd(context, fd);
	if (descriptor == NULL)
		return B_FILE_ERROR;

	// now put the fd in place
	status = new_fd(context, descriptor);
	if (status < 0)
		put_fd(descriptor);

	return status;
}


static int
dup2_fd(int oldfd, int newfd, bool kernel)
{
	struct file_descriptor *evicted = NULL;
	struct io_context *context;

	TRACE(("dup2_fd: ofd = %d, nfd = %d\n", oldfd, newfd));

	// quick check
	if (oldfd < 0 || newfd < 0)
		return B_FILE_ERROR;

	// Get current I/O context and lock it
	context = get_current_io_context(kernel);
	mutex_lock(&context->io_mutex);

	// Check if the fds are valid (mutex must be locked because
	// the table size could be changed)
	if (oldfd >= context->table_size
		|| newfd >= context->table_size
		|| context->fds[oldfd] == NULL) {
		mutex_unlock(&context->io_mutex);
		return B_FILE_ERROR;
	}

	// Check for identity, note that it cannot be made above
	// because we always want to return an error on invalid
	// handles
	if (oldfd != newfd) {
		// Now do the work
		evicted = context->fds[newfd];
		atomic_add(&context->fds[oldfd]->ref_count, 1);
		context->fds[newfd] = context->fds[oldfd];
	}

	mutex_unlock(&context->io_mutex);

	// Say bye bye to the evicted fd
	if (evicted)
		put_fd(evicted);

	return newfd;
}


status_t
select_fd(int fd, uint8 event, uint32 ref, struct select_sync *sync, bool kernel)
{
	struct file_descriptor *descriptor;
	status_t status;

	PRINT(("select_fd(fd = %d, event = %u, ref = %lu, selectsync = %p)\n", fd, event, ref, sync));

	descriptor = get_fd(get_current_io_context(kernel), fd);
	if (descriptor == NULL)
		return B_FILE_ERROR;

	if (descriptor->ops->fd_select) {
		status = descriptor->ops->fd_select(descriptor, event, ref, sync);
	} else {
		// if the I/O subsystem doesn't support select(), we will
		// immediately notify the select call
		status = notify_select_event((void *)sync, ref);
	}

	put_fd(descriptor);
	return status;
}


status_t
deselect_fd(int fd, uint8 event, struct select_sync *sync, bool kernel)
{
	struct file_descriptor *descriptor;
	status_t status;

	PRINT(("deselect_fd(fd = %d, event = %u, ref = %lu, selectsync = %p)\n", fd, event, ref, sync));

	descriptor = get_fd(get_current_io_context(kernel), fd);
	if (descriptor == NULL)
		return B_FILE_ERROR;

	if (descriptor->ops->fd_deselect)
		status = descriptor->ops->fd_deselect(descriptor, event, sync);
	else
		status = B_OK;

	put_fd(descriptor);
	return status;
}


/** This function checks if the specified fd is valid in the current
 *	context. It can be used for a quick check; the fd is not locked
 *	so it could become invalid immediately after this check.
 */

bool
fd_is_valid(int fd, bool kernel)
{
	struct file_descriptor *descriptor = get_fd(get_current_io_context(kernel), fd);
	if (descriptor == NULL)
		return false;
	
	put_fd(descriptor);
	return true;
}


//	#pragma mark -
/*** USER routines ***/ 


ssize_t
user_read(int fd, off_t pos, void *buffer, size_t length)
{
	struct file_descriptor *descriptor;
	ssize_t retval;

	/* This is a user_function, so abort if we have a kernel address */
	if (!CHECK_USER_ADDRESS(buffer))
		return B_BAD_ADDRESS;

	descriptor = get_fd(get_current_io_context(false), fd);
	if (!descriptor)
		return B_FILE_ERROR;

	if (descriptor->ops->fd_read) {
		retval = descriptor->ops->fd_read(descriptor, pos, buffer, &length);
		if (retval >= 0)
			retval = (ssize_t)length;
	} else
		retval = EINVAL;

	put_fd(descriptor);
	return retval;
}


ssize_t
user_write(int fd, off_t pos, const void *buffer, size_t length)
{
	struct file_descriptor *descriptor;
	ssize_t retval = 0;

	CHECK_USER_ADDR(buffer)

	descriptor = get_fd(get_current_io_context(false), fd);
	if (!descriptor)
		return B_FILE_ERROR;

	if (descriptor->ops->fd_write) {
		retval = descriptor->ops->fd_write(descriptor, pos, buffer, &length);
		if (retval >= 0)
			retval = (ssize_t)length;
	} else
		retval = EINVAL;

	put_fd(descriptor);
	return retval;
}


off_t
user_seek(int fd, off_t pos, int seekType)
{
	struct file_descriptor *descriptor;

	descriptor = get_fd(get_current_io_context(false), fd);
	if (!descriptor)
		return B_FILE_ERROR;

	TRACE(("user_seek(descriptor = %p)\n", descriptor));

	if (descriptor->ops->fd_seek)
		pos = descriptor->ops->fd_seek(descriptor, pos, seekType);
	else
		pos = ESPIPE;

	put_fd(descriptor);
	return pos;
}


int
user_ioctl(int fd, ulong op, void *buffer, size_t length)
{
	struct file_descriptor *descriptor;
	int status;

	CHECK_USER_ADDR(buffer)

	PRINT(("user_ioctl: fd %d\n", fd));

	descriptor = get_fd(get_current_io_context(false), fd);
	if (!descriptor)
		return B_FILE_ERROR;

	if (descriptor->ops->fd_ioctl)
		status = descriptor->ops->fd_ioctl(descriptor, op, buffer, length);
	else
		status = EOPNOTSUPP;

	put_fd(descriptor);
	return status;
}


ssize_t
user_read_dir(int fd, struct dirent *buffer, size_t bufferSize, uint32 maxCount)
{
	struct file_descriptor *descriptor;
	ssize_t retval;

	CHECK_USER_ADDR(buffer)

	PRINT(("user_read_dir(fd = %d, buffer = %p, bufferSize = %ld, count = %d)\n", fd, buffer, bufferSize, maxCount));

	descriptor = get_fd(get_current_io_context(false), fd);
	if (descriptor == NULL)
		return B_FILE_ERROR;

	if (descriptor->ops->fd_read_dir) {
		uint32 count = maxCount;
		retval = descriptor->ops->fd_read_dir(descriptor, buffer, bufferSize, &count);
		if (retval >= 0)
			retval = count;
	} else
		retval = EOPNOTSUPP;

	put_fd(descriptor);
	return retval;
}


status_t
user_rewind_dir(int fd)
{
	struct file_descriptor *descriptor;
	status_t status;

	PRINT(("user_rewind_dir(fd = %d)\n", fd));

	descriptor = get_fd(get_current_io_context(false), fd);
	if (descriptor == NULL)
		return B_FILE_ERROR;

	if (descriptor->ops->fd_rewind_dir)
		status = descriptor->ops->fd_rewind_dir(descriptor);
	else
		status = EOPNOTSUPP;

	put_fd(descriptor);
	return status;
}


int
user_read_stat(int fd, struct stat *userStat)
{
	struct file_descriptor *descriptor;
	status_t status;

	/* This is a user_function, so abort if we have a kernel address */
	CHECK_USER_ADDR(userStat)

	descriptor = get_fd(get_current_io_context(false), fd);
	if (descriptor == NULL)
		return B_FILE_ERROR;

	TRACE(("user_read_stat(descriptor = %p)\n", descriptor));

	if (descriptor->ops->fd_read_stat) {
		// we're using the stat buffer on the stack to not have to
		// lock the given stat buffer in memory
		struct stat stat;

		status = descriptor->ops->fd_read_stat(descriptor, &stat);
		if (status >= 0)
			status = user_memcpy(userStat, &stat, sizeof(stat));
	} else
		status = EOPNOTSUPP;

	put_fd(descriptor);
	return status;
}


int
user_write_stat(int fd, const struct stat *userStat, int statMask)
{
	struct file_descriptor *descriptor;
	status_t status;

	CHECK_USER_ADDR(userStat)

	descriptor = get_fd(get_current_io_context(false), fd);
	if (descriptor == NULL)
		return B_FILE_ERROR;

	TRACE(("user_write_stat(descriptor = %p)\n", descriptor));

	if (descriptor->ops->fd_write_stat) {
		// we're using the stat buffer on the stack to not have to
		// lock the given stat buffer in memory
		struct stat stat;
		status = user_memcpy(&stat, userStat, sizeof(stat));
		if (status == B_OK)
			status = descriptor->ops->fd_write_stat(descriptor, &stat, statMask);
	} else
		status = EOPNOTSUPP;

	put_fd(descriptor);
	return status;
}


int
user_close(int fd)
{
	struct io_context *io = get_current_io_context(false);
	struct file_descriptor *descriptor = get_fd(io, fd);

	if (descriptor == NULL)
		return B_FILE_ERROR;

	TRACE(("user_close(descriptor = %p)\n", descriptor));

	remove_fd(io, fd);

	put_fd(descriptor);
	return B_OK;
}


int
user_dup(int fd)
{
	return dup_fd(fd, false);
}


int
user_dup2(int ofd, int nfd)
{
	return dup2_fd(ofd, nfd, false);
}


//	#pragma mark -
/*** SYSTEM functions ***/


ssize_t
sys_read(int fd, off_t pos, void *buffer, size_t length)
{
	struct file_descriptor *descriptor;
	ssize_t retval;

	descriptor = get_fd(get_current_io_context(true), fd);
	if (!descriptor)
		return B_FILE_ERROR;

	if (descriptor->ops->fd_read) {
		retval = descriptor->ops->fd_read(descriptor, pos, buffer, &length);
		if (retval >= 0)
			retval = (ssize_t)length;
	} else
		retval = EINVAL;

	put_fd(descriptor);
	return retval;
}


ssize_t
sys_write(int fd, off_t pos, const void *buffer, size_t length)
{
	struct file_descriptor *descriptor;
	ssize_t retval;

	descriptor = get_fd(get_current_io_context(true), fd);
	if (descriptor == NULL)
		return B_FILE_ERROR;

	if (descriptor->ops->fd_write) {
		retval = descriptor->ops->fd_write(descriptor, pos, buffer, &length);
		if (retval >= 0)
			retval = (ssize_t)length;

		PRINT(("sys_write(%d) = %ld (rlen = %ld)\n", fd, retval, length));
	} else
		retval = EINVAL;

	put_fd(descriptor);
	return retval;
}


off_t
sys_seek(int fd, off_t pos, int seekType)
{
	struct file_descriptor *descriptor;

	descriptor = get_fd(get_current_io_context(true), fd);
	if (!descriptor)
		return B_FILE_ERROR;

	if (descriptor->ops->fd_seek)
		pos = descriptor->ops->fd_seek(descriptor, pos, seekType);
	else
		pos = ESPIPE;

	put_fd(descriptor);
	return pos;
}


int
sys_ioctl(int fd, ulong op, void *buffer, size_t length)
{
	struct file_descriptor *descriptor;
	int status;

	PRINT(("sys_ioctl: fd %d\n", fd));

	descriptor = get_fd(get_current_io_context(true), fd);
	if (descriptor == NULL)
		return B_FILE_ERROR;

	if (descriptor->ops->fd_ioctl)
		status = descriptor->ops->fd_ioctl(descriptor, op, buffer, length);
	else
		status = EOPNOTSUPP;

	put_fd(descriptor);
	return status;
}


ssize_t
sys_read_dir(int fd, struct dirent *buffer, size_t bufferSize, uint32 maxCount)
{
	struct file_descriptor *descriptor;
	ssize_t retval;

	PRINT(("sys_read_dir(fd = %d, buffer = %p, bufferSize = %ld, count = %u)\n",fd, buffer, bufferSize, maxCount));

	descriptor = get_fd(get_current_io_context(true), fd);
	if (descriptor == NULL)
		return B_FILE_ERROR;

	if (descriptor->ops->fd_read_dir) {
		uint32 count = maxCount;
		retval = descriptor->ops->fd_read_dir(descriptor, buffer, bufferSize, &count);
		if (retval >= 0)
			retval = count;
	} else
		retval = EOPNOTSUPP;

	put_fd(descriptor);
	return retval;
}


status_t
sys_rewind_dir(int fd)
{
	struct file_descriptor *descriptor;
	status_t status;

	PRINT(("sys_rewind_dir(fd = %d)\n",fd));

	descriptor = get_fd(get_current_io_context(true), fd);
	if (descriptor == NULL)
		return B_FILE_ERROR;

	if (descriptor->ops->fd_rewind_dir)
		status = descriptor->ops->fd_rewind_dir(descriptor);
	else
		status = EOPNOTSUPP;

	put_fd(descriptor);
	return status;
}


int
sys_read_stat(int fd, struct stat *stat)
{
	struct file_descriptor *descriptor;
	status_t status;

	descriptor = get_fd(get_current_io_context(true), fd);
	if (descriptor == NULL)
		return B_FILE_ERROR;

	TRACE(("sys_read_stat(descriptor = %p)\n", descriptor));

	if (descriptor->ops->fd_read_stat)
		status = descriptor->ops->fd_read_stat(descriptor, stat);
	else
		status = EOPNOTSUPP;

	put_fd(descriptor);
	return status;
}


int
sys_write_stat(int fd, const struct stat *stat, int statMask)
{
	struct file_descriptor *descriptor;
	status_t status;

	descriptor = get_fd(get_current_io_context(true), fd);
	if (descriptor == NULL)
		return B_FILE_ERROR;

	TRACE(("sys_write_stat(descriptor = %p)\n", descriptor));

	if (descriptor->ops->fd_write_stat)
		status = descriptor->ops->fd_write_stat(descriptor, stat, statMask);
	else
		status = EOPNOTSUPP;

	put_fd(descriptor);
	return status;
}


int
sys_close(int fd)
{
	struct io_context *io = get_current_io_context(true);
	struct file_descriptor *descriptor = get_fd(io, fd);

	if (descriptor == NULL)
		return B_FILE_ERROR;

	remove_fd(io, fd);

	put_fd(descriptor);
	return B_OK;
}


int
sys_dup(int fd)
{
	return dup_fd(fd, true);
}


int
sys_dup2(int ofd, int nfd)
{
	return dup2_fd(ofd, nfd, true);
}