| /* |
| * linux/fs/pipe.c |
| * |
| * Copyright (C) 1991, 1992, 1999 Linus Torvalds |
| */ |
| |
| #include <linux/mm.h> |
| #include <linux/file.h> |
| #include <linux/poll.h> |
| #include <linux/slab.h> |
| #include <linux/module.h> |
| #include <linux/init.h> |
| |
| #include <asm/uaccess.h> |
| #include <asm/ioctls.h> |
| |
| /* |
| * We use a start+len construction, which provides full use of the |
| * allocated memory. |
| * -- Florian Coosmann (FGC) |
| * |
| * Reads with count = 0 should always return 0. |
| * -- Julian Bradfield 1999-06-07. |
| */ |
| |
| /* Drop the inode semaphore and wait for a pipe event, atomically */ |
| void pipe_wait(struct inode * inode) |
| { |
| DECLARE_WAITQUEUE(wait, current); |
| current->state = TASK_INTERRUPTIBLE; |
| add_wait_queue(PIPE_WAIT(*inode), &wait); |
| up(PIPE_SEM(*inode)); |
| schedule(); |
| remove_wait_queue(PIPE_WAIT(*inode), &wait); |
| current->state = TASK_RUNNING; |
| down(PIPE_SEM(*inode)); |
| } |
| |
| static ssize_t |
| pipe_read(struct file *filp, char *buf, size_t count, loff_t *ppos) |
| { |
| struct inode *inode = filp->f_dentry->d_inode; |
| ssize_t size, read, ret; |
| |
| /* Seeks are not allowed on pipes. */ |
| ret = -ESPIPE; |
| read = 0; |
| if (ppos != &filp->f_pos) |
| goto out_nolock; |
| |
| /* Always return 0 on null read. */ |
| ret = 0; |
| if (count == 0) |
| goto out_nolock; |
| |
| /* Get the pipe semaphore */ |
| ret = -ERESTARTSYS; |
| if (down_interruptible(PIPE_SEM(*inode))) |
| goto out_nolock; |
| |
| if (PIPE_EMPTY(*inode)) { |
| do_more_read: |
| ret = 0; |
| if (!PIPE_WRITERS(*inode)) |
| goto out; |
| |
| ret = -EAGAIN; |
| if (filp->f_flags & O_NONBLOCK) |
| goto out; |
| |
| for (;;) { |
| PIPE_WAITING_READERS(*inode)++; |
| pipe_wait(inode); |
| PIPE_WAITING_READERS(*inode)--; |
| ret = -ERESTARTSYS; |
| if (signal_pending(current)) |
| goto out; |
| ret = 0; |
| if (!PIPE_EMPTY(*inode)) |
| break; |
| if (!PIPE_WRITERS(*inode)) |
| goto out; |
| } |
| } |
| |
| /* Read what data is available. */ |
| ret = -EFAULT; |
| while (count > 0 && (size = PIPE_LEN(*inode))) { |
| char *pipebuf = PIPE_BASE(*inode) + PIPE_START(*inode); |
| ssize_t chars = PIPE_MAX_RCHUNK(*inode); |
| |
| if (chars > count) |
| chars = count; |
| if (chars > size) |
| chars = size; |
| |
| if (copy_to_user(buf, pipebuf, chars)) |
| goto out; |
| |
| read += chars; |
| PIPE_START(*inode) += chars; |
| PIPE_START(*inode) &= (PIPE_SIZE - 1); |
| PIPE_LEN(*inode) -= chars; |
| count -= chars; |
| buf += chars; |
| } |
| |
| /* Cache behaviour optimization */ |
| if (!PIPE_LEN(*inode)) |
| PIPE_START(*inode) = 0; |
| |
| if (count && PIPE_WAITING_WRITERS(*inode) && !(filp->f_flags & O_NONBLOCK)) { |
| /* |
| * We know that we are going to sleep: signal |
| * writers synchronously that there is more |
| * room. |
| */ |
| wake_up_interruptible_sync(PIPE_WAIT(*inode)); |
| if (!PIPE_EMPTY(*inode)) |
| BUG(); |
| goto do_more_read; |
| } |
| /* Signal writers asynchronously that there is more room. */ |
| wake_up_interruptible(PIPE_WAIT(*inode)); |
| |
| ret = read; |
| out: |
| up(PIPE_SEM(*inode)); |
| out_nolock: |
| if (read) |
| ret = read; |
| |
| UPDATE_ATIME(inode); |
| return ret; |
| } |
| |
| static ssize_t |
| pipe_write(struct file *filp, const char *buf, size_t count, loff_t *ppos) |
| { |
| struct inode *inode = filp->f_dentry->d_inode; |
| ssize_t free, written, ret; |
| |
| /* Seeks are not allowed on pipes. */ |
| ret = -ESPIPE; |
| written = 0; |
| if (ppos != &filp->f_pos) |
| goto out_nolock; |
| |
| /* Null write succeeds. */ |
| ret = 0; |
| if (count == 0) |
| goto out_nolock; |
| |
| ret = -ERESTARTSYS; |
| if (down_interruptible(PIPE_SEM(*inode))) |
| goto out_nolock; |
| |
| /* No readers yields SIGPIPE. */ |
| if (!PIPE_READERS(*inode)) |
| goto sigpipe; |
| |
| /* If count <= PIPE_BUF, we have to make it atomic. */ |
| free = (count <= PIPE_BUF ? count : 1); |
| |
| /* Wait, or check for, available space. */ |
| if (filp->f_flags & O_NONBLOCK) { |
| ret = -EAGAIN; |
| if (PIPE_FREE(*inode) < free) |
| goto out; |
| } else { |
| while (PIPE_FREE(*inode) < free) { |
| PIPE_WAITING_WRITERS(*inode)++; |
| pipe_wait(inode); |
| PIPE_WAITING_WRITERS(*inode)--; |
| ret = -ERESTARTSYS; |
| if (signal_pending(current)) |
| goto out; |
| |
| if (!PIPE_READERS(*inode)) |
| goto sigpipe; |
| } |
| } |
| |
| /* Copy into available space. */ |
| ret = -EFAULT; |
| while (count > 0) { |
| int space; |
| char *pipebuf = PIPE_BASE(*inode) + PIPE_END(*inode); |
| ssize_t chars = PIPE_MAX_WCHUNK(*inode); |
| |
| if ((space = PIPE_FREE(*inode)) != 0) { |
| if (chars > count) |
| chars = count; |
| if (chars > space) |
| chars = space; |
| |
| if (copy_from_user(pipebuf, buf, chars)) |
| goto out; |
| |
| written += chars; |
| PIPE_LEN(*inode) += chars; |
| count -= chars; |
| buf += chars; |
| space = PIPE_FREE(*inode); |
| continue; |
| } |
| |
| ret = written; |
| if (filp->f_flags & O_NONBLOCK) |
| break; |
| |
| do { |
| /* |
| * Synchronous wake-up: it knows that this process |
| * is going to give up this CPU, so it doesn't have |
| * to do idle reschedules. |
| */ |
| wake_up_interruptible_sync(PIPE_WAIT(*inode)); |
| PIPE_WAITING_WRITERS(*inode)++; |
| pipe_wait(inode); |
| PIPE_WAITING_WRITERS(*inode)--; |
| if (signal_pending(current)) |
| goto out; |
| if (!PIPE_READERS(*inode)) |
| goto sigpipe; |
| } while (!PIPE_FREE(*inode)); |
| ret = -EFAULT; |
| } |
| |
| /* Signal readers asynchronously that there is more data. */ |
| wake_up_interruptible(PIPE_WAIT(*inode)); |
| |
| update_mctime(inode); |
| |
| out: |
| up(PIPE_SEM(*inode)); |
| out_nolock: |
| if (written) |
| ret = written; |
| return ret; |
| |
| sigpipe: |
| if (written) |
| goto out; |
| up(PIPE_SEM(*inode)); |
| send_sig(SIGPIPE, current, 0); |
| return -EPIPE; |
| } |
| |
| static ssize_t |
| bad_pipe_r(struct file *filp, char *buf, size_t count, loff_t *ppos) |
| { |
| return -EBADF; |
| } |
| |
| static ssize_t |
| bad_pipe_w(struct file *filp, const char *buf, size_t count, loff_t *ppos) |
| { |
| return -EBADF; |
| } |
| |
| static int |
| pipe_ioctl(struct inode *pino, struct file *filp, |
| unsigned int cmd, unsigned long arg) |
| { |
| switch (cmd) { |
| case FIONREAD: |
| return put_user(PIPE_LEN(*pino), (int *)arg); |
| default: |
| return -EINVAL; |
| } |
| } |
| |
| /* No kernel lock held - fine */ |
| static unsigned int |
| pipe_poll(struct file *filp, poll_table *wait) |
| { |
| unsigned int mask; |
| struct inode *inode = filp->f_dentry->d_inode; |
| |
| poll_wait(filp, PIPE_WAIT(*inode), wait); |
| |
| /* Reading only -- no need for acquiring the semaphore. */ |
| mask = POLLIN | POLLRDNORM; |
| if (PIPE_EMPTY(*inode)) |
| mask = POLLOUT | POLLWRNORM; |
| if (!PIPE_WRITERS(*inode) && filp->f_version != PIPE_WCOUNTER(*inode)) |
| mask |= POLLHUP; |
| if (!PIPE_READERS(*inode)) |
| mask |= POLLERR; |
| |
| return mask; |
| } |
| |
| /* FIXME: most Unices do not set POLLERR for fifos */ |
| #define fifo_poll pipe_poll |
| |
| static int |
| pipe_release(struct inode *inode, int decr, int decw) |
| { |
| down(PIPE_SEM(*inode)); |
| PIPE_READERS(*inode) -= decr; |
| PIPE_WRITERS(*inode) -= decw; |
| if (!PIPE_READERS(*inode) && !PIPE_WRITERS(*inode)) { |
| struct pipe_inode_info *info = inode->i_pipe; |
| inode->i_pipe = NULL; |
| free_page((unsigned long) info->base); |
| kfree(info); |
| } else { |
| wake_up_interruptible(PIPE_WAIT(*inode)); |
| } |
| up(PIPE_SEM(*inode)); |
| |
| return 0; |
| } |
| |
| static int |
| pipe_read_release(struct inode *inode, struct file *filp) |
| { |
| return pipe_release(inode, 1, 0); |
| } |
| |
| static int |
| pipe_write_release(struct inode *inode, struct file *filp) |
| { |
| return pipe_release(inode, 0, 1); |
| } |
| |
| static int |
| pipe_rdwr_release(struct inode *inode, struct file *filp) |
| { |
| int decr, decw; |
| |
| decr = (filp->f_mode & FMODE_READ) != 0; |
| decw = (filp->f_mode & FMODE_WRITE) != 0; |
| return pipe_release(inode, decr, decw); |
| } |
| |
| static int |
| pipe_read_open(struct inode *inode, struct file *filp) |
| { |
| int ret = -ENOENT; |
| |
| down(PIPE_SEM(*inode)); |
| if (inode->i_pipe) { |
| ret = 0; |
| PIPE_READERS(*inode)++; |
| } |
| up(PIPE_SEM(*inode)); |
| |
| return ret; |
| } |
| |
| static int |
| pipe_write_open(struct inode *inode, struct file *filp) |
| { |
| int ret = -ENOENT; |
| |
| down(PIPE_SEM(*inode)); |
| if (inode->i_pipe) { |
| ret = 0; |
| PIPE_WRITERS(*inode)++; |
| } |
| up(PIPE_SEM(*inode)); |
| |
| return ret; |
| } |
| |
| static int |
| pipe_rdwr_open(struct inode *inode, struct file *filp) |
| { |
| int ret = -ENOENT; |
| |
| down(PIPE_SEM(*inode)); |
| if (inode->i_pipe) { |
| ret = 0; |
| if (filp->f_mode & FMODE_READ) |
| PIPE_READERS(*inode)++; |
| if (filp->f_mode & FMODE_WRITE) |
| PIPE_WRITERS(*inode)++; |
| } |
| up(PIPE_SEM(*inode)); |
| |
| return ret; |
| } |
| |
| /* |
| * The file_operations structs are not static because they |
| * are also used in linux/fs/fifo.c to do operations on FIFOs. |
| */ |
| struct file_operations read_fifo_fops = { |
| llseek: no_llseek, |
| read: pipe_read, |
| write: bad_pipe_w, |
| poll: fifo_poll, |
| ioctl: pipe_ioctl, |
| open: pipe_read_open, |
| release: pipe_read_release, |
| }; |
| |
| struct file_operations write_fifo_fops = { |
| llseek: no_llseek, |
| read: bad_pipe_r, |
| write: pipe_write, |
| poll: fifo_poll, |
| ioctl: pipe_ioctl, |
| open: pipe_write_open, |
| release: pipe_write_release, |
| }; |
| |
| struct file_operations rdwr_fifo_fops = { |
| llseek: no_llseek, |
| read: pipe_read, |
| write: pipe_write, |
| poll: fifo_poll, |
| ioctl: pipe_ioctl, |
| open: pipe_rdwr_open, |
| release: pipe_rdwr_release, |
| }; |
| |
| struct file_operations read_pipe_fops = { |
| llseek: no_llseek, |
| read: pipe_read, |
| write: bad_pipe_w, |
| poll: pipe_poll, |
| ioctl: pipe_ioctl, |
| open: pipe_read_open, |
| release: pipe_read_release, |
| }; |
| |
| struct file_operations write_pipe_fops = { |
| llseek: no_llseek, |
| read: bad_pipe_r, |
| write: pipe_write, |
| poll: pipe_poll, |
| ioctl: pipe_ioctl, |
| open: pipe_write_open, |
| release: pipe_write_release, |
| }; |
| |
| struct file_operations rdwr_pipe_fops = { |
| llseek: no_llseek, |
| read: pipe_read, |
| write: pipe_write, |
| poll: pipe_poll, |
| ioctl: pipe_ioctl, |
| open: pipe_rdwr_open, |
| release: pipe_rdwr_release, |
| }; |
| |
| struct inode* pipe_new(struct inode* inode) |
| { |
| unsigned long page; |
| |
| page = __get_free_page(GFP_USER); |
| if (!page) |
| return NULL; |
| |
| inode->i_pipe = kmalloc(sizeof(struct pipe_inode_info), GFP_KERNEL); |
| if (!inode->i_pipe) |
| goto fail_page; |
| |
| init_waitqueue_head(PIPE_WAIT(*inode)); |
| PIPE_BASE(*inode) = (char*) page; |
| PIPE_START(*inode) = PIPE_LEN(*inode) = 0; |
| PIPE_READERS(*inode) = PIPE_WRITERS(*inode) = 0; |
| PIPE_WAITING_READERS(*inode) = PIPE_WAITING_WRITERS(*inode) = 0; |
| PIPE_RCOUNTER(*inode) = PIPE_WCOUNTER(*inode) = 1; |
| |
| return inode; |
| fail_page: |
| free_page(page); |
| return NULL; |
| } |
| |
| static struct vfsmount *pipe_mnt; |
| static int pipefs_delete_dentry(struct dentry *dentry) |
| { |
| return 1; |
| } |
| static struct dentry_operations pipefs_dentry_operations = { |
| d_delete: pipefs_delete_dentry, |
| }; |
| |
| static struct inode * get_pipe_inode(void) |
| { |
| struct inode *inode = new_inode(pipe_mnt->mnt_sb); |
| |
| if (!inode) |
| goto fail_inode; |
| |
| if(!pipe_new(inode)) |
| goto fail_iput; |
| PIPE_READERS(*inode) = PIPE_WRITERS(*inode) = 1; |
| inode->i_fop = &rdwr_pipe_fops; |
| |
| /* |
| * Mark the inode dirty from the very beginning, |
| * that way it will never be moved to the dirty |
| * list because "mark_inode_dirty()" will think |
| * that it already _is_ on the dirty list. |
| */ |
| inode->i_state = I_DIRTY; |
| inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR; |
| inode->i_uid = current->fsuid; |
| inode->i_gid = current->fsgid; |
| inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; |
| inode->i_blksize = PAGE_SIZE; |
| return inode; |
| |
| fail_iput: |
| iput(inode); |
| fail_inode: |
| return NULL; |
| } |
| |
| int do_pipe(int *fd) |
| { |
| struct qstr this; |
| char name[32]; |
| struct dentry *dentry; |
| struct inode * inode; |
| struct file *f1, *f2; |
| int error; |
| int i,j; |
| |
| error = -ENFILE; |
| f1 = get_empty_filp(); |
| if (!f1) |
| goto no_files; |
| |
| f2 = get_empty_filp(); |
| if (!f2) |
| goto close_f1; |
| |
| inode = get_pipe_inode(); |
| if (!inode) |
| goto close_f12; |
| |
| error = get_unused_fd(); |
| if (error < 0) |
| goto close_f12_inode; |
| i = error; |
| |
| error = get_unused_fd(); |
| if (error < 0) |
| goto close_f12_inode_i; |
| j = error; |
| |
| error = -ENOMEM; |
| sprintf(name, "[%lu]", inode->i_ino); |
| this.name = name; |
| this.len = strlen(name); |
| this.hash = inode->i_ino; /* will go */ |
| dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &this); |
| if (!dentry) |
| goto close_f12_inode_i_j; |
| dentry->d_op = &pipefs_dentry_operations; |
| d_add(dentry, inode); |
| f1->f_vfsmnt = f2->f_vfsmnt = mntget(mntget(pipe_mnt)); |
| f1->f_dentry = f2->f_dentry = dget(dentry); |
| |
| /* read file */ |
| f1->f_pos = f2->f_pos = 0; |
| f1->f_flags = O_RDONLY; |
| f1->f_op = &read_pipe_fops; |
| f1->f_mode = 1; |
| f1->f_version = 0; |
| |
| /* write file */ |
| f2->f_flags = O_WRONLY; |
| f2->f_op = &write_pipe_fops; |
| f2->f_mode = 2; |
| f2->f_version = 0; |
| |
| fd_install(i, f1); |
| fd_install(j, f2); |
| fd[0] = i; |
| fd[1] = j; |
| return 0; |
| |
| close_f12_inode_i_j: |
| put_unused_fd(j); |
| close_f12_inode_i: |
| put_unused_fd(i); |
| close_f12_inode: |
| free_page((unsigned long) PIPE_BASE(*inode)); |
| kfree(inode->i_pipe); |
| inode->i_pipe = NULL; |
| iput(inode); |
| close_f12: |
| put_filp(f2); |
| close_f1: |
| put_filp(f1); |
| no_files: |
| return error; |
| } |
| |
| /* |
| * pipefs should _never_ be mounted by userland - too much of security hassle, |
| * no real gain from having the whole whorehouse mounted. So we don't need |
| * any operations on the root directory. However, we need a non-trivial |
| * d_name - pipe: will go nicely and kill the special-casing in procfs. |
| */ |
| static int pipefs_statfs(struct super_block *sb, struct statfs *buf) |
| { |
| buf->f_type = PIPEFS_MAGIC; |
| buf->f_bsize = 1024; |
| buf->f_namelen = 255; |
| return 0; |
| } |
| |
| static struct super_operations pipefs_ops = { |
| statfs: pipefs_statfs, |
| }; |
| |
| static struct super_block * pipefs_read_super(struct super_block *sb, void *data, int silent) |
| { |
| struct inode *root = new_inode(sb); |
| if (!root) |
| return NULL; |
| root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR; |
| root->i_uid = root->i_gid = 0; |
| root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME; |
| sb->s_blocksize = 1024; |
| sb->s_blocksize_bits = 10; |
| sb->s_magic = PIPEFS_MAGIC; |
| sb->s_op = &pipefs_ops; |
| sb->s_root = d_alloc(NULL, &(const struct qstr) { "pipe:", 5, 0 }); |
| if (!sb->s_root) { |
| iput(root); |
| return NULL; |
| } |
| sb->s_root->d_sb = sb; |
| sb->s_root->d_parent = sb->s_root; |
| d_instantiate(sb->s_root, root); |
| return sb; |
| } |
| |
| static DECLARE_FSTYPE(pipe_fs_type, "pipefs", pipefs_read_super, FS_NOMOUNT); |
| |
| static int __init init_pipe_fs(void) |
| { |
| int err = register_filesystem(&pipe_fs_type); |
| if (!err) { |
| pipe_mnt = kern_mount(&pipe_fs_type); |
| err = PTR_ERR(pipe_mnt); |
| if (IS_ERR(pipe_mnt)) |
| unregister_filesystem(&pipe_fs_type); |
| else |
| err = 0; |
| } |
| return err; |
| } |
| |
| static void __exit exit_pipe_fs(void) |
| { |
| unregister_filesystem(&pipe_fs_type); |
| mntput(pipe_mnt); |
| } |
| |
| module_init(init_pipe_fs) |
| module_exit(exit_pipe_fs) |