freebsd-dev/sys/kern/uipc_shm.c
Alexander Kabaev 6ee7dd87ba Shared memory objects that have size which is not necessarily equal to
exact multiple of system page size should still be allowed to be mapped
in their entirety to match the regular vnode backed file behavior.

Reported by: ed
Reviewed by: jhb
2008-12-01 22:33:50 +00:00

619 lines
15 KiB
C

/*-
* 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?
*
* (6) Add MAC support in mac_biba(4) and mac_mls(4).
*
* (7) Add a MAC check_create() hook for creating new named objects.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_mac.h"
#include <sys/param.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/fnv_hash.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mman.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/refcount.h>
#include <sys/resourcevar.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/systm.h>
#include <sys/sx.h>
#include <sys/time.h>
#include <sys/vnode.h>
#include <security/mac/mac_framework.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
#include <vm/swap_pager.h>
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"));
VM_OBJECT_LOCK(shmfd->shm_object);
vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING);
vm_object_set_flag(shmfd->shm_object, OBJ_NOSPLIT);
VM_OBJECT_UNLOCK(shmfd->shm_object);
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)
{
accmode_t accmode;
accmode = 0;
if (flags & FREAD)
accmode |= VREAD;
if (flags & FWRITE)
accmode |= VWRITE;
return (vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid,
accmode, 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 > round_page(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);
}