/*- * Copyright (c) 2006 Robert N. M. Watson * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ /* * Support for shared swap-backed anonymous memory objects via * shm_open(2) and shm_unlink(2). While most of the implementation is * here, vm_mmap.c contains mapping logic changes. * * TODO: * * (2) Need to export data to a userland tool via a sysctl. Should ipcs(1) * and ipcrm(1) be expanded or should new tools to manage both POSIX * kernel semaphores and POSIX shared memory be written? * * (3) Add support for this file type to fstat(1). * * (4) Resource limits? Does this need its own resource limits or are the * existing limits in mmap(2) sufficient? * * (5) Partial page truncation. vnode_pager_setsize() will zero any parts * of a partially mapped page as a result of ftruncate(2)/truncate(2). * We can do the same (with the same pmap evil), but do we need to * worry about the bits on disk if the page is swapped out or will the * swapper zero the parts of a page that are invalid if the page is * swapped back in for us? */ #include __FBSDID("$FreeBSD$"); #include "opt_mac.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include struct shm_mapping { char *sm_path; Fnv32_t sm_fnv; struct shmfd *sm_shmfd; LIST_ENTRY(shm_mapping) sm_link; }; static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor"); static LIST_HEAD(, shm_mapping) *shm_dictionary; static struct sx shm_dict_lock; static struct mtx shm_timestamp_lock; static u_long shm_hash; #define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash]) static int shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags); static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode); static void shm_dict_init(void *arg); static void shm_drop(struct shmfd *shmfd); static struct shmfd *shm_hold(struct shmfd *shmfd); static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd); static struct shmfd *shm_lookup(char *path, Fnv32_t fnv); static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred); static void shm_dotruncate(struct shmfd *shmfd, off_t length); static fo_rdwr_t shm_read; static fo_rdwr_t shm_write; static fo_truncate_t shm_truncate; static fo_ioctl_t shm_ioctl; static fo_poll_t shm_poll; static fo_kqfilter_t shm_kqfilter; static fo_stat_t shm_stat; static fo_close_t shm_close; /* File descriptor operations. */ static struct fileops shm_ops = { .fo_read = shm_read, .fo_write = shm_write, .fo_truncate = shm_truncate, .fo_ioctl = shm_ioctl, .fo_poll = shm_poll, .fo_kqfilter = shm_kqfilter, .fo_stat = shm_stat, .fo_close = shm_close, .fo_flags = DFLAG_PASSABLE }; FEATURE(posix_shm, "POSIX shared memory"); static int shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred, int flags, struct thread *td) { return (EOPNOTSUPP); } static int shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred, int flags, struct thread *td) { return (EOPNOTSUPP); } static int shm_truncate(struct file *fp, off_t length, struct ucred *active_cred, struct thread *td) { struct shmfd *shmfd; #ifdef MAC int error; #endif shmfd = fp->f_data; #ifdef MAC error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd); if (error) return (error); #endif shm_dotruncate(shmfd, length); return (0); } static int shm_ioctl(struct file *fp, u_long com, void *data, struct ucred *active_cred, struct thread *td) { return (EOPNOTSUPP); } static int shm_poll(struct file *fp, int events, struct ucred *active_cred, struct thread *td) { return (EOPNOTSUPP); } static int shm_kqfilter(struct file *fp, struct knote *kn) { return (EOPNOTSUPP); } static int shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, struct thread *td) { struct shmfd *shmfd; #ifdef MAC int error; #endif shmfd = fp->f_data; #ifdef MAC error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd); if (error) return (error); #endif /* * Attempt to return sanish values for fstat() on a memory file * descriptor. */ bzero(sb, sizeof(*sb)); sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */ sb->st_blksize = PAGE_SIZE; sb->st_size = shmfd->shm_size; sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize; sb->st_atimespec = shmfd->shm_atime; sb->st_ctimespec = shmfd->shm_ctime; sb->st_mtimespec = shmfd->shm_mtime; sb->st_birthtimespec = shmfd->shm_birthtime; sb->st_uid = shmfd->shm_uid; sb->st_gid = shmfd->shm_gid; return (0); } static int shm_close(struct file *fp, struct thread *td) { struct shmfd *shmfd; shmfd = fp->f_data; fp->f_data = NULL; shm_drop(shmfd); return (0); } static void shm_dotruncate(struct shmfd *shmfd, off_t length) { vm_object_t object; vm_page_t m; vm_pindex_t nobjsize; object = shmfd->shm_object; VM_OBJECT_LOCK(object); if (length == shmfd->shm_size) { VM_OBJECT_UNLOCK(object); return; } nobjsize = OFF_TO_IDX(length + PAGE_MASK); /* Are we shrinking? If so, trim the end. */ if (length < shmfd->shm_size) { /* Toss in memory pages. */ if (nobjsize < object->size) vm_object_page_remove(object, nobjsize, object->size, FALSE); /* Toss pages from swap. */ if (object->type == OBJT_SWAP) swap_pager_freespace(object, nobjsize, object->size - nobjsize); /* * If the last page is partially mapped, then zero out * the garbage at the end of the page. See comments * in vnode_page_setsize() for more details. * * XXXJHB: This handles in memory pages, but what about * a page swapped out to disk? */ if ((length & PAGE_MASK) && (m = vm_page_lookup(object, OFF_TO_IDX(length))) != NULL && m->valid != 0) { int base = (int)length & PAGE_MASK; int size = PAGE_SIZE - base; pmap_zero_page_area(m, base, size); vm_page_lock_queues(); vm_page_set_validclean(m, base, size); if (m->dirty != 0) m->dirty = VM_PAGE_BITS_ALL; vm_page_unlock_queues(); } else if ((length & PAGE_MASK) && __predict_false(object->cache != NULL)) { vm_page_cache_free(object, OFF_TO_IDX(length), nobjsize); } } shmfd->shm_size = length; mtx_lock(&shm_timestamp_lock); vfs_timestamp(&shmfd->shm_ctime); shmfd->shm_mtime = shmfd->shm_ctime; mtx_unlock(&shm_timestamp_lock); object->size = nobjsize; VM_OBJECT_UNLOCK(object); } /* * shmfd object management including creation and reference counting * routines. */ static struct shmfd * shm_alloc(struct ucred *ucred, mode_t mode) { struct shmfd *shmfd; shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO); shmfd->shm_size = 0; shmfd->shm_uid = ucred->cr_uid; shmfd->shm_gid = ucred->cr_gid; shmfd->shm_mode = mode; shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL, shmfd->shm_size, VM_PROT_DEFAULT, 0); KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate")); vfs_timestamp(&shmfd->shm_birthtime); shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime = shmfd->shm_birthtime; refcount_init(&shmfd->shm_refs, 1); #ifdef MAC mac_posixshm_init(shmfd); mac_posixshm_create(ucred, shmfd); #endif return (shmfd); } static struct shmfd * shm_hold(struct shmfd *shmfd) { refcount_acquire(&shmfd->shm_refs); return (shmfd); } static void shm_drop(struct shmfd *shmfd) { if (refcount_release(&shmfd->shm_refs)) { #ifdef MAC mac_posixshm_destroy(shmfd); #endif vm_object_deallocate(shmfd->shm_object); free(shmfd, M_SHMFD); } } /* * Determine if the credentials have sufficient permissions for a * specified combination of FREAD and FWRITE. */ static int shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags) { int acc_mode; acc_mode = 0; if (flags & FREAD) acc_mode |= VREAD; if (flags & FWRITE) acc_mode |= VWRITE; return (vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid, acc_mode, ucred, NULL)); } /* * Dictionary management. We maintain an in-kernel dictionary to map * paths to shmfd objects. We use the FNV hash on the path to store * the mappings in a hash table. */ static void shm_dict_init(void *arg) { mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF); sx_init(&shm_dict_lock, "shm dictionary"); shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash); } SYSINIT(shm_dict_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_dict_init, NULL); static struct shmfd * shm_lookup(char *path, Fnv32_t fnv) { struct shm_mapping *map; LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { if (map->sm_fnv != fnv) continue; if (strcmp(map->sm_path, path) == 0) return (map->sm_shmfd); } return (NULL); } static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd) { struct shm_mapping *map; map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK); map->sm_path = path; map->sm_fnv = fnv; map->sm_shmfd = shm_hold(shmfd); LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link); } static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred) { struct shm_mapping *map; int error; LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { if (map->sm_fnv != fnv) continue; if (strcmp(map->sm_path, path) == 0) { #ifdef MAC error = mac_posixshm_check_unlink(ucred, map->sm_shmfd); if (error) return (error); #endif error = shm_access(map->sm_shmfd, ucred, FREAD | FWRITE); if (error) return (error); LIST_REMOVE(map, sm_link); shm_drop(map->sm_shmfd); free(map->sm_path, M_SHMFD); free(map, M_SHMFD); return (0); } } return (ENOENT); } /* System calls. */ int shm_open(struct thread *td, struct shm_open_args *uap) { struct filedesc *fdp; struct shmfd *shmfd; struct file *fp; char *path; Fnv32_t fnv; mode_t cmode; int fd, error; if ((uap->flags & O_ACCMODE) != O_RDONLY && (uap->flags & O_ACCMODE) != O_RDWR) return (EINVAL); if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC)) != 0) return (EINVAL); fdp = td->td_proc->p_fd; cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS; error = falloc(td, &fp, &fd); if (error) return (error); /* A SHM_ANON path pointer creates an anonymous object. */ if (uap->path == SHM_ANON) { /* A read-only anonymous object is pointless. */ if ((uap->flags & O_ACCMODE) == O_RDONLY) { fdclose(fdp, fp, fd, td); fdrop(fp, td); return (EINVAL); } shmfd = shm_alloc(td->td_ucred, cmode); } else { path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK); error = copyinstr(uap->path, path, MAXPATHLEN, NULL); /* Require paths to start with a '/' character. */ if (error == 0 && path[0] != '/') error = EINVAL; if (error) { fdclose(fdp, fp, fd, td); fdrop(fp, td); free(path, M_SHMFD); return (error); } fnv = fnv_32_str(path, FNV1_32_INIT); sx_xlock(&shm_dict_lock); shmfd = shm_lookup(path, fnv); if (shmfd == NULL) { /* Object does not yet exist, create it if requested. */ if (uap->flags & O_CREAT) { shmfd = shm_alloc(td->td_ucred, cmode); shm_insert(path, fnv, shmfd); } else { free(path, M_SHMFD); error = ENOENT; } } else { /* * Object already exists, obtain a new * reference if requested and permitted. */ free(path, M_SHMFD); if ((uap->flags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL)) error = EEXIST; else { #ifdef MAC error = mac_posixshm_check_open(td->td_ucred, shmfd); if (error == 0) #endif error = shm_access(shmfd, td->td_ucred, FFLAGS(uap->flags & O_ACCMODE)); } /* * Truncate the file back to zero length if * O_TRUNC was specified and the object was * opened with read/write. */ if (error == 0 && (uap->flags & (O_ACCMODE | O_TRUNC)) == (O_RDWR | O_TRUNC)) { #ifdef MAC error = mac_posixshm_check_truncate( td->td_ucred, fp->f_cred, shmfd); if (error == 0) #endif shm_dotruncate(shmfd, 0); } if (error == 0) shm_hold(shmfd); } sx_xunlock(&shm_dict_lock); if (error) { fdclose(fdp, fp, fd, td); fdrop(fp, td); return (error); } } finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops); FILEDESC_XLOCK(fdp); if (fdp->fd_ofiles[fd] == fp) fdp->fd_ofileflags[fd] |= UF_EXCLOSE; FILEDESC_XUNLOCK(fdp); td->td_retval[0] = fd; fdrop(fp, td); return (0); } int shm_unlink(struct thread *td, struct shm_unlink_args *uap) { char *path; Fnv32_t fnv; int error; path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK); error = copyinstr(uap->path, path, MAXPATHLEN, NULL); if (error) { free(path, M_TEMP); return (error); } fnv = fnv_32_str(path, FNV1_32_INIT); sx_xlock(&shm_dict_lock); error = shm_remove(path, fnv, td->td_ucred); sx_xunlock(&shm_dict_lock); free(path, M_TEMP); return (error); } /* * mmap() helper to validate mmap() requests against shm object state * and give mmap() the vm_object to use for the mapping. */ int shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff, vm_object_t *obj) { /* * XXXRW: This validation is probably insufficient, and subject to * sign errors. It should be fixed. */ if (foff >= shmfd->shm_size || foff + objsize > shmfd->shm_size) return (EINVAL); mtx_lock(&shm_timestamp_lock); vfs_timestamp(&shmfd->shm_atime); mtx_unlock(&shm_timestamp_lock); vm_object_reference(shmfd->shm_object); *obj = shmfd->shm_object; return (0); }