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linux
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fs
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pipe.c
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/* * 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 <linux/fs.h> #include <linux/log2.h> #include <linux/mount.h> #include <linux/magic.h> #include <linux/pipe_fs_i.h> #include <linux/uio.h> #include <linux/highmem.h> #include <linux/pagemap.h> #include <linux/audit.h> #include <linux/syscalls.h> #include <linux/fcntl.h> #include <asm/uaccess.h> #include <asm/ioctls.h> #include "internal.h" /* * The max size that a non-root user is allowed to grow the pipe. Can * be set by root in /proc/sys/fs/pipe-max-size */ unsigned int pipe_max_size = 1048576; /* * Minimum pipe size, as required by POSIX */ unsigned int pipe_min_size = PAGE_SIZE; /* * 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. * * FIFOs and Pipes now generate SIGIO for both readers and writers. * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16 * * pipe_read & write cleanup * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09 */ static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass) { if (pipe->inode) mutex_lock_nested(&pipe->inode->i_mutex, subclass); } void pipe_lock(struct pipe_inode_info *pipe) { /* * pipe_lock() nests non-pipe inode locks (for writing to a file) */ pipe_lock_nested(pipe, I_MUTEX_PARENT); } EXPORT_SYMBOL(pipe_lock); void pipe_unlock(struct pipe_inode_info *pipe) { if (pipe->inode) mutex_unlock(&pipe->inode->i_mutex); } EXPORT_SYMBOL(pipe_unlock); void pipe_double_lock(struct pipe_inode_info *pipe1, struct pipe_inode_info *pipe2) { BUG_ON(pipe1 == pipe2); if (pipe1 < pipe2) { pipe_lock_nested(pipe1, I_MUTEX_PARENT); pipe_lock_nested(pipe2, I_MUTEX_CHILD); } else { pipe_lock_nested(pipe2, I_MUTEX_PARENT); pipe_lock_nested(pipe1, I_MUTEX_CHILD); } } /* Drop the inode semaphore and wait for a pipe event, atomically */ void pipe_wait(struct pipe_inode_info *pipe) { DEFINE_WAIT(wait); /* * Pipes are system-local resources, so sleeping on them * is considered a noninteractive wait: */ prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE); pipe_unlock(pipe); schedule(); finish_wait(&pipe->wait, &wait); pipe_lock(pipe); } static int pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len, int atomic) { unsigned long copy; while (len > 0) { while (!iov->iov_len) iov++; copy = min_t(unsigned long, len, iov->iov_len); if (atomic) { if (__copy_from_user_inatomic(to, iov->iov_base, copy)) return -EFAULT; } else { if (copy_from_user(to, iov->iov_base, copy)) return -EFAULT; } to += copy; len -= copy; iov->iov_base += copy; iov->iov_len -= copy; } return 0; } static int pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len, int atomic) { unsigned long copy; while (len > 0) { while (!iov->iov_len) iov++; copy = min_t(unsigned long, len, iov->iov_len); if (atomic) { if (__copy_to_user_inatomic(iov->iov_base, from, copy)) return -EFAULT; } else { if (copy_to_user(iov->iov_base, from, copy)) return -EFAULT; } from += copy; len -= copy; iov->iov_base += copy; iov->iov_len -= copy; } return 0; } /* * Attempt to pre-fault in the user memory, so we can use atomic copies. * Returns the number of bytes not faulted in. */ static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len) { while (!iov->iov_len) iov++; while (len > 0) { unsigned long this_len; this_len = min_t(unsigned long, len, iov->iov_len); if (fault_in_pages_writeable(iov->iov_base, this_len)) break; len -= this_len; iov++; } return len; } /* * Pre-fault in the user memory, so we can use atomic copies. */ static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len) { while (!iov->iov_len) iov++; while (len > 0) { unsigned long this_len; this_len = min_t(unsigned long, len, iov->iov_len); fault_in_pages_readable(iov->iov_base, this_len); len -= this_len; iov++; } } static void anon_pipe_buf_release(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { struct page *page = buf->page; /* * If nobody else uses this page, and we don't already have a * temporary page, let's keep track of it as a one-deep * allocation cache. (Otherwise just release our reference to it) */ if (page_count(page) == 1 && !pipe->tmp_page) pipe->tmp_page = page; else page_cache_release(page); } /** * generic_pipe_buf_map - virtually map a pipe buffer * @pipe: the pipe that the buffer belongs to * @buf: the buffer that should be mapped * @atomic: whether to use an atomic map * * Description: * This function returns a kernel virtual address mapping for the * pipe_buffer passed in @buf. If @atomic is set, an atomic map is provided * and the caller has to be careful not to fault before calling * the unmap function. * * Note that this function calls kmap_atomic() if @atomic != 0. */ void *generic_pipe_buf_map(struct pipe_inode_info *pipe, struct pipe_buffer *buf, int atomic) { if (atomic) { buf->flags |= PIPE_BUF_FLAG_ATOMIC; return kmap_atomic(buf->page); } return kmap(buf->page); } EXPORT_SYMBOL(generic_pipe_buf_map); /** * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer * @pipe: the pipe that the buffer belongs to * @buf: the buffer that should be unmapped * @map_data: the data that the mapping function returned * * Description: * This function undoes the mapping that ->map() provided. */ void generic_pipe_buf_unmap(struct pipe_inode_info *pipe, struct pipe_buffer *buf, void *map_data) { if (buf->flags & PIPE_BUF_FLAG_ATOMIC) { buf->flags &= ~PIPE_BUF_FLAG_ATOMIC; kunmap_atomic(map_data); } else kunmap(buf->page); } EXPORT_SYMBOL(generic_pipe_buf_unmap); /** * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer * @pipe: the pipe that the buffer belongs to * @buf: the buffer to attempt to steal * * Description: * This function attempts to steal the &struct page attached to * @buf. If successful, this function returns 0 and returns with * the page locked. The caller may then reuse the page for whatever * he wishes; the typical use is insertion into a different file * page cache. */ int generic_pipe_buf_steal(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { struct page *page = buf->page; /* * A reference of one is golden, that means that the owner of this * page is the only one holding a reference to it. lock the page * and return OK. */ if (page_count(page) == 1) { lock_page(page); return 0; } return 1; } EXPORT_SYMBOL(generic_pipe_buf_steal); /** * generic_pipe_buf_get - get a reference to a &struct pipe_buffer * @pipe: the pipe that the buffer belongs to * @buf: the buffer to get a reference to * * Description: * This function grabs an extra reference to @buf. It's used in * in the tee() system call, when we duplicate the buffers in one * pipe into another. */ void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { page_cache_get(buf->page); } EXPORT_SYMBOL(generic_pipe_buf_get); /** * generic_pipe_buf_confirm - verify contents of the pipe buffer * @info: the pipe that the buffer belongs to * @buf: the buffer to confirm * * Description: * This function does nothing, because the generic pipe code uses * pages that are always good when inserted into the pipe. */ int generic_pipe_buf_confirm(struct pipe_inode_info *info, struct pipe_buffer *buf) { return 0; } EXPORT_SYMBOL(generic_pipe_buf_confirm); /** * generic_pipe_buf_release - put a reference to a &struct pipe_buffer * @pipe: the pipe that the buffer belongs to * @buf: the buffer to put a reference to * * Description: * This function releases a reference to @buf. */ void generic_pipe_buf_release(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { page_cache_release(buf->page); } EXPORT_SYMBOL(generic_pipe_buf_release); static const struct pipe_buf_operations anon_pipe_buf_ops = { .can_merge = 1, .map = generic_pipe_buf_map, .unmap = generic_pipe_buf_unmap, .confirm = generic_pipe_buf_confirm, .release = anon_pipe_buf_release, .steal = generic_pipe_buf_steal, .get = generic_pipe_buf_get, }; static const struct pipe_buf_operations packet_pipe_buf_ops = { .can_merge = 0, .map = generic_pipe_buf_map, .unmap = generic_pipe_buf_unmap, .confirm = generic_pipe_buf_confirm, .release = anon_pipe_buf_release, .steal = generic_pipe_buf_steal, .get = generic_pipe_buf_get, }; static ssize_t pipe_read(struct kiocb *iocb, const struct iovec *_iov, unsigned long nr_segs, loff_t pos) { struct file *filp = iocb->ki_filp; struct pipe_inode_info *pipe = file_inode(filp)->i_pipe; int do_wakeup; ssize_t ret; struct iovec *iov = (struct iovec *)_iov; size_t total_len; total_len = iov_length(iov, nr_segs); /* Null read succeeds. */ if (unlikely(total_len == 0)) return 0; do_wakeup = 0; ret = 0; pipe_lock(pipe); for (;;) { int bufs = pipe->nrbufs; if (bufs) { int curbuf = pipe->curbuf; struct pipe_buffer *buf = pipe->bufs + curbuf; const struct pipe_buf_operations *ops = buf->ops; void *addr; size_t chars = buf->len; int error, atomic; if (chars > total_len) chars = total_len; error = ops->confirm(pipe, buf); if (error) { if (!ret) ret = error; break; } atomic = !iov_fault_in_pages_write(iov, chars); redo: addr = ops->map(pipe, buf, atomic); error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic); ops->unmap(pipe, buf, addr); if (unlikely(error)) { /* * Just retry with the slow path if we failed. */ if (atomic) { atomic = 0; goto redo; } if (!ret) ret = error; break; } ret += chars; buf->offset += chars; buf->len -= chars; /* Was it a packet buffer? Clean up and exit */ if (buf->flags & PIPE_BUF_FLAG_PACKET) { total_len = chars; buf->len = 0; } if (!buf->len) { buf->ops = NULL; ops->release(pipe, buf); curbuf = (curbuf + 1) & (pipe->buffers - 1); pipe->curbuf = curbuf; pipe->nrbufs = --bufs; do_wakeup = 1; } total_len -= chars; if (!total_len) break; /* common path: read succeeded */ } if (bufs) /* More to do? */ continue; if (!pipe->writers) break; if (!pipe->waiting_writers) { /* syscall merging: Usually we must not sleep * if O_NONBLOCK is set, or if we got some data. * But if a writer sleeps in kernel space, then * we can wait for that data without violating POSIX. */ if (ret) break; if (filp->f_flags & O_NONBLOCK) { ret = -EAGAIN; break; } } if (signal_pending(current)) { if (!ret) ret = -ERESTARTSYS; break; } if (do_wakeup) { wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM); kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); } pipe_wait(pipe); } pipe_unlock(pipe); /* Signal writers asynchronously that there is more room. */ if (do_wakeup) { wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM); kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); } if (ret > 0) file_accessed(filp); return ret; } static inline int is_packetized(struct file *file) { return (file->f_flags & O_DIRECT) != 0; } static ssize_t pipe_write(struct kiocb *iocb, const struct iovec *_iov, unsigned long nr_segs, loff_t ppos) { struct file *filp = iocb->ki_filp; struct pipe_inode_info *pipe = file_inode(filp)->i_pipe; ssize_t ret; int do_wakeup; struct iovec *iov = (struct iovec *)_iov; size_t total_len; ssize_t chars; total_len = iov_length(iov, nr_segs); /* Null write succeeds. */ if (unlikely(total_len == 0)) return 0; do_wakeup = 0; ret = 0; pipe_lock(pipe); if (!pipe->readers) { send_sig(SIGPIPE, current, 0); ret = -EPIPE; goto out; } /* We try to merge small writes */ chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */ if (pipe->nrbufs && chars != 0) { int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) & (pipe->buffers - 1); struct pipe_buffer *buf = pipe->bufs + lastbuf; const struct pipe_buf_operations *ops = buf->ops; int offset = buf->offset + buf->len; if (ops->can_merge && offset + chars <= PAGE_SIZE) { int error, atomic = 1; void *addr; error = ops->confirm(pipe, buf); if (error) goto out; iov_fault_in_pages_read(iov, chars); redo1: addr = ops->map(pipe, buf, atomic); error = pipe_iov_copy_from_user(offset + addr, iov, chars, atomic); ops->unmap(pipe, buf, addr); ret = error; do_wakeup = 1; if (error) { if (atomic) { atomic = 0; goto redo1; } goto out; } buf->len += chars; total_len -= chars; ret = chars; if (!total_len) goto out; } } for (;;) { int bufs; if (!pipe->readers) { send_sig(SIGPIPE, current, 0); if (!ret) ret = -EPIPE; break; } bufs = pipe->nrbufs; if (bufs < pipe->buffers) { int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1); struct pipe_buffer *buf = pipe->bufs + newbuf; struct page *page = pipe->tmp_page; char *src; int error, atomic = 1; if (!page) { page = alloc_page(GFP_HIGHUSER); if (unlikely(!page)) { ret = ret ? : -ENOMEM; break; } pipe->tmp_page = page; } /* Always wake up, even if the copy fails. Otherwise * we lock up (O_NONBLOCK-)readers that sleep due to * syscall merging. * FIXME! Is this really true? */ do_wakeup = 1; chars = PAGE_SIZE; if (chars > total_len) chars = total_len; iov_fault_in_pages_read(iov, chars); redo2: if (atomic) src = kmap_atomic(page); else src = kmap(page); error = pipe_iov_copy_from_user(src, iov, chars, atomic); if (atomic) kunmap_atomic(src); else kunmap(page); if (unlikely(error)) { if (atomic) { atomic = 0; goto redo2; } if (!ret) ret = error; break; } ret += chars; /* Insert it into the buffer array */ buf->page = page; buf->ops = &anon_pipe_buf_ops; buf->offset = 0; buf->len = chars; buf->flags = 0; if (is_packetized(filp)) { buf->ops = &packet_pipe_buf_ops; buf->flags = PIPE_BUF_FLAG_PACKET; } pipe->nrbufs = ++bufs; pipe->tmp_page = NULL; total_len -= chars; if (!total_len) break; } if (bufs < pipe->buffers) continue; if (filp->f_flags & O_NONBLOCK) { if (!ret) ret = -EAGAIN; break; } if (signal_pending(current)) { if (!ret) ret = -ERESTARTSYS; break; } if (do_wakeup) { wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM); kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); do_wakeup = 0; } pipe->waiting_writers++; pipe_wait(pipe); pipe->waiting_writers--; } out: pipe_unlock(pipe); if (do_wakeup) { wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM); kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); } if (ret > 0) { int err = file_update_time(filp); if (err) ret = err; } return ret; } static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) { struct pipe_inode_info *pipe = file_inode(filp)->i_pipe; int count, buf, nrbufs; switch (cmd) { case FIONREAD: pipe_lock(pipe); count = 0; buf = pipe->curbuf; nrbufs = pipe->nrbufs; while (--nrbufs >= 0) { count += pipe->bufs[buf].len; buf = (buf+1) & (pipe->buffers - 1); } pipe_unlock(pipe); return put_user(count, (int __user *)arg); default: return -ENOIOCTLCMD; } } /* No kernel lock held - fine */ static unsigned int pipe_poll(struct file *filp, poll_table *wait) { unsigned int mask; struct pipe_inode_info *pipe = file_inode(filp)->i_pipe; int nrbufs; poll_wait(filp, &pipe->wait, wait); /* Reading only -- no need for acquiring the semaphore. */ nrbufs = pipe->nrbufs; mask = 0; if (filp->f_mode & FMODE_READ) { mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0; if (!pipe->writers && filp->f_version != pipe->w_counter) mask |= POLLHUP; } if (filp->f_mode & FMODE_WRITE) { mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0; /* * Most Unices do not set POLLERR for FIFOs but on Linux they * behave exactly like pipes for poll(). */ if (!pipe->readers) mask |= POLLERR; } return mask; } static int pipe_release(struct inode *inode, struct file *file) { struct pipe_inode_info *pipe; mutex_lock(&inode->i_mutex); pipe = inode->i_pipe; if (file->f_mode & FMODE_READ) pipe->readers--; if (file->f_mode & FMODE_WRITE) pipe->writers--; if (!pipe->readers && !pipe->writers) { free_pipe_info(inode); } else { wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP); kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); } mutex_unlock(&inode->i_mutex); return 0; } static int pipe_fasync(int fd, struct file *filp, int on) { struct pipe_inode_info *pipe = file_inode(filp)->i_pipe; int retval = 0; pipe_lock(pipe); if (filp->f_mode & FMODE_READ) retval = fasync_helper(fd, filp, on, &pipe->fasync_readers); if ((filp->f_mode & FMODE_WRITE) && retval >= 0) { retval = fasync_helper(fd, filp, on, &pipe->fasync_writers); if (retval < 0 && (filp->f_mode & FMODE_READ)) /* this can happen only if on == T */ fasync_helper(-1, filp, 0, &pipe->fasync_readers); } pipe_unlock(pipe); return retval; } struct pipe_inode_info * alloc_pipe_info(struct inode *inode) { struct pipe_inode_info *pipe; pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL); if (pipe) { pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL); if (pipe->bufs) { init_waitqueue_head(&pipe->wait); pipe->r_counter = pipe->w_counter = 1; pipe->inode = inode; pipe->buffers = PIPE_DEF_BUFFERS; return pipe; } kfree(pipe); } return NULL; } void __free_pipe_info(struct pipe_inode_info *pipe) { int i; for (i = 0; i < pipe->buffers; i++) { struct pipe_buffer *buf = pipe->bufs + i; if (buf->ops) buf->ops->release(pipe, buf); } if (pipe->tmp_page) __free_page(pipe->tmp_page); kfree(pipe->bufs); kfree(pipe); } void free_pipe_info(struct inode *inode) { __free_pipe_info(inode->i_pipe); inode->i_pipe = NULL; } static struct vfsmount *pipe_mnt __read_mostly; /* * pipefs_dname() is called from d_path(). */ static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen) { return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]", dentry->d_inode->i_ino); } static const struct dentry_operations pipefs_dentry_operations = { .d_dname = pipefs_dname, }; static struct inode * get_pipe_inode(void) { struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb); struct pipe_inode_info *pipe; if (!inode) goto fail_inode; inode->i_ino = get_next_ino(); pipe = alloc_pipe_info(inode); if (!pipe) goto fail_iput; inode->i_pipe = pipe; pipe->readers = pipe->writers = 1; inode->i_fop = &pipefifo_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; return inode; fail_iput: iput(inode); fail_inode: return NULL; } int create_pipe_files(struct file **res, int flags) { int err; struct inode *inode = get_pipe_inode(); struct file *f; struct path path; static struct qstr name = { .name = "" }; if (!inode) return -ENFILE; err = -ENOMEM; path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name); if (!path.dentry) goto err_inode; path.mnt = mntget(pipe_mnt); d_instantiate(path.dentry, inode); err = -ENFILE; f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops); if (IS_ERR(f)) goto err_dentry; f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)); res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops); if (IS_ERR(res[0])) goto err_file; path_get(&path); res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK); res[1] = f; return 0; err_file: put_filp(f); err_dentry: free_pipe_info(inode); path_put(&path); return err; err_inode: free_pipe_info(inode); iput(inode); return err; } static int __do_pipe_flags(int *fd, struct file **files, int flags) { int error; int fdw, fdr; if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT)) return -EINVAL; error = create_pipe_files(files, flags); if (error) return error; error = get_unused_fd_flags(flags); if (error < 0) goto err_read_pipe; fdr = error; error = get_unused_fd_flags(flags); if (error < 0) goto err_fdr; fdw = error; audit_fd_pair(fdr, fdw); fd[0] = fdr; fd[1] = fdw; return 0; err_fdr: put_unused_fd(fdr); err_read_pipe: fput(files[0]); fput(files[1]); return error; } int do_pipe_flags(int *fd, int flags) { struct file *files[2]; int error = __do_pipe_flags(fd, files, flags); if (!error) { fd_install(fd[0], files[0]); fd_install(fd[1], files[1]); } return error; } /* * sys_pipe() is the normal C calling standard for creating * a pipe. It's not the way Unix traditionally does this, though. */ SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags) { struct file *files[2]; int fd[2]; int error; error = __do_pipe_flags(fd, files, flags); if (!error) { if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) { fput(files[0]); fput(files[1]); put_unused_fd(fd[0]); put_unused_fd(fd[1]); error = -EFAULT; } else { fd_install(fd[0], files[0]); fd_install(fd[1], files[1]); } } return error; } SYSCALL_DEFINE1(pipe, int __user *, fildes) { return sys_pipe2(fildes, 0); } static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt) { int cur = *cnt; while (cur == *cnt) { pipe_wait(pipe); if (signal_pending(current)) break; } return cur == *cnt ? -ERESTARTSYS : 0; } static void wake_up_partner(struct pipe_inode_info *pipe) { wake_up_interruptible(&pipe->wait); } static int fifo_open(struct inode *inode, struct file *filp) { struct pipe_inode_info *pipe; bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC; int ret; mutex_lock(&inode->i_mutex); pipe = inode->i_pipe; if (!pipe) { ret = -ENOMEM; pipe = alloc_pipe_info(inode); if (!pipe) goto err_nocleanup; inode->i_pipe = pipe; } filp->f_version = 0; /* We can only do regular read/write on fifos */ filp->f_mode &= (FMODE_READ | FMODE_WRITE); switch (filp->f_mode) { case FMODE_READ: /* * O_RDONLY * POSIX.1 says that O_NONBLOCK means return with the FIFO * opened, even when there is no process writing the FIFO. */ pipe->r_counter++; if (pipe->readers++ == 0) wake_up_partner(pipe); if (!is_pipe && !pipe->writers) { if ((filp->f_flags & O_NONBLOCK)) { /* suppress POLLHUP until we have * seen a writer */ filp->f_version = pipe->w_counter; } else { if (wait_for_partner(pipe, &pipe->w_counter)) goto err_rd; } } break; case FMODE_WRITE: /* * O_WRONLY * POSIX.1 says that O_NONBLOCK means return -1 with * errno=ENXIO when there is no process reading the FIFO. */ ret = -ENXIO; if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers) goto err; pipe->w_counter++; if (!pipe->writers++) wake_up_partner(pipe); if (!is_pipe && !pipe->readers) { if (wait_for_partner(pipe, &pipe->r_counter)) goto err_wr; } break; case FMODE_READ | FMODE_WRITE: /* * O_RDWR * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set. * This implementation will NEVER block on a O_RDWR open, since * the process can at least talk to itself. */ pipe->readers++; pipe->writers++; pipe->r_counter++; pipe->w_counter++; if (pipe->readers == 1 || pipe->writers == 1) wake_up_partner(pipe); break; default: ret = -EINVAL; goto err; } /* Ok! */ mutex_unlock(&inode->i_mutex); return 0; err_rd: if (!--pipe->readers) wake_up_interruptible(&pipe->wait); ret = -ERESTARTSYS; goto err; err_wr: if (!--pipe->writers) wake_up_interruptible(&pipe->wait); ret = -ERESTARTSYS; goto err; err: if (!pipe->readers && !pipe->writers) free_pipe_info(inode); err_nocleanup: mutex_unlock(&inode->i_mutex); return ret; } const struct file_operations pipefifo_fops = { .open = fifo_open, .llseek = no_llseek, .read = do_sync_read, .aio_read = pipe_read, .write = do_sync_write, .aio_write = pipe_write, .poll = pipe_poll, .unlocked_ioctl = pipe_ioctl, .release = pipe_release, .fasync = pipe_fasync, }; /* * Allocate a new array of pipe buffers and copy the info over. Returns the * pipe size if successful, or return -ERROR on error. */ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages) { struct pipe_buffer *bufs; /* * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't * expect a lot of shrink+grow operations, just free and allocate * again like we would do for growing. If the pipe currently * contains more buffers than arg, then return busy. */ if (nr_pages < pipe->nrbufs) return -EBUSY; bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN); if (unlikely(!bufs)) return -ENOMEM; /* * The pipe array wraps around, so just start the new one at zero * and adjust the indexes. */ if (pipe->nrbufs) { unsigned int tail; unsigned int head; tail = pipe->curbuf + pipe->nrbufs; if (tail < pipe->buffers) tail = 0; else tail &= (pipe->buffers - 1); head = pipe->nrbufs - tail; if (head) memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer)); if (tail) memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer)); } pipe->curbuf = 0; kfree(pipe->bufs); pipe->bufs = bufs; pipe->buffers = nr_pages; return nr_pages * PAGE_SIZE; } /* * Currently we rely on the pipe array holding a power-of-2 number * of pages. */ static inline unsigned int round_pipe_size(unsigned int size) { unsigned long nr_pages; nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; return roundup_pow_of_two(nr_pages) << PAGE_SHIFT; } /* * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax * will return an error. */ int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf, size_t *lenp, loff_t *ppos) { int ret; ret = proc_dointvec_minmax(table, write, buf, lenp, ppos); if (ret < 0 || !write) return ret; pipe_max_size = round_pipe_size(pipe_max_size); return ret; } /* * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same * location, so checking ->i_pipe is not enough to verify that this is a * pipe. */ struct pipe_inode_info *get_pipe_info(struct file *file) { struct inode *i = file_inode(file); return S_ISFIFO(i->i_mode) ? i->i_pipe : NULL; } long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg) { struct pipe_inode_info *pipe; long ret; pipe = get_pipe_info(file); if (!pipe) return -EBADF; pipe_lock(pipe); switch (cmd) { case F_SETPIPE_SZ: { unsigned int size, nr_pages; size = round_pipe_size(arg); nr_pages = size >> PAGE_SHIFT; ret = -EINVAL; if (!nr_pages) goto out; if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) { ret = -EPERM; goto out; } ret = pipe_set_size(pipe, nr_pages); break; } case F_GETPIPE_SZ: ret = pipe->buffers * PAGE_SIZE; break; default: ret = -EINVAL; break; } out: pipe_unlock(pipe); return ret; } static const struct super_operations pipefs_ops = { .destroy_inode = free_inode_nonrcu, .statfs = simple_statfs, }; /* * 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 struct dentry *pipefs_mount(struct file_system_type *fs_type, int flags, const char *dev_name, void *data) { return mount_pseudo(fs_type, "pipe:", &pipefs_ops, &pipefs_dentry_operations, PIPEFS_MAGIC); } static struct file_system_type pipe_fs_type = { .name = "pipefs", .mount = pipefs_mount, .kill_sb = kill_anon_super, }; static int __init init_pipe_fs(void) { int err = register_filesystem(&pipe_fs_type); if (!err) { pipe_mnt = kern_mount(&pipe_fs_type); if (IS_ERR(pipe_mnt)) { err = PTR_ERR(pipe_mnt); unregister_filesystem(&pipe_fs_type); } } return err; } fs_initcall(init_pipe_fs);
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