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kern_descrip.c
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kern_descrip.c
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/* $NetBSD: kern_descrip.c,v 1.262 2023/10/04 22:17:09 ad Exp $ */
/*-
* Copyright (c) 2008, 2009, 2023 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Andrew Doran.
*
* 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
*/
/*
* Copyright (c) 1982, 1986, 1989, 1991, 1993
* The Regents of the University of California. All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* 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.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
*
* @(#)kern_descrip.c 8.8 (Berkeley) 2/14/95
*/
/*
* File descriptor management.
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_descrip.c,v 1.262 2023/10/04 22:17:09 ad Exp $");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/file.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/fcntl.h>
#include <sys/pool.h>
#include <sys/unistd.h>
#include <sys/resourcevar.h>
#include <sys/conf.h>
#include <sys/event.h>
#include <sys/kauth.h>
#include <sys/atomic.h>
#include <sys/syscallargs.h>
#include <sys/cpu.h>
#include <sys/kmem.h>
#include <sys/vnode.h>
#include <sys/sysctl.h>
#include <sys/ktrace.h>
/*
* A list (head) of open files, counter, and lock protecting them.
*/
struct filelist filehead __cacheline_aligned;
static u_int nfiles __cacheline_aligned;
kmutex_t filelist_lock __cacheline_aligned;
static pool_cache_t filedesc_cache __read_mostly;
static pool_cache_t file_cache __read_mostly;
static int file_ctor(void *, void *, int);
static void file_dtor(void *, void *);
static void fdfile_ctor(fdfile_t *);
static void fdfile_dtor(fdfile_t *);
static int filedesc_ctor(void *, void *, int);
static void filedesc_dtor(void *, void *);
static int filedescopen(dev_t, int, int, lwp_t *);
static int sysctl_kern_file(SYSCTLFN_PROTO);
static int sysctl_kern_file2(SYSCTLFN_PROTO);
static void fill_file(struct file *, const struct file *);
static void fill_file2(struct kinfo_file *, const file_t *, const fdfile_t *,
int, pid_t);
const struct cdevsw filedesc_cdevsw = {
.d_open = filedescopen,
.d_close = noclose,
.d_read = noread,
.d_write = nowrite,
.d_ioctl = noioctl,
.d_stop = nostop,
.d_tty = notty,
.d_poll = nopoll,
.d_mmap = nommap,
.d_kqfilter = nokqfilter,
.d_discard = nodiscard,
.d_flag = D_OTHER | D_MPSAFE
};
/* For ease of reading. */
__strong_alias(fd_putvnode,fd_putfile)
__strong_alias(fd_putsock,fd_putfile)
/*
* Initialize the descriptor system.
*/
void
fd_sys_init(void)
{
static struct sysctllog *clog;
mutex_init(&filelist_lock, MUTEX_DEFAULT, IPL_NONE);
LIST_INIT(&filehead);
file_cache = pool_cache_init(sizeof(file_t), coherency_unit, 0,
0, "file", NULL, IPL_NONE, file_ctor, file_dtor, NULL);
KASSERT(file_cache != NULL);
filedesc_cache = pool_cache_init(sizeof(filedesc_t), coherency_unit,
0, 0, "filedesc", NULL, IPL_NONE, filedesc_ctor, filedesc_dtor,
NULL);
KASSERT(filedesc_cache != NULL);
sysctl_createv(&clog, 0, NULL, NULL,
CTLFLAG_PERMANENT,
CTLTYPE_STRUCT, "file",
SYSCTL_DESCR("System open file table"),
sysctl_kern_file, 0, NULL, 0,
CTL_KERN, KERN_FILE, CTL_EOL);
sysctl_createv(&clog, 0, NULL, NULL,
CTLFLAG_PERMANENT,
CTLTYPE_STRUCT, "file2",
SYSCTL_DESCR("System open file table"),
sysctl_kern_file2, 0, NULL, 0,
CTL_KERN, KERN_FILE2, CTL_EOL);
}
static bool
fd_isused(filedesc_t *fdp, unsigned fd)
{
u_int off = fd >> NDENTRYSHIFT;
KASSERT(fd < atomic_load_consume(&fdp->fd_dt)->dt_nfiles);
return (fdp->fd_lomap[off] & (1U << (fd & NDENTRYMASK))) != 0;
}
/*
* Verify that the bitmaps match the descriptor table.
*/
static inline void
fd_checkmaps(filedesc_t *fdp)
{
#ifdef DEBUG
fdtab_t *dt;
u_int fd;
KASSERT(fdp->fd_refcnt <= 1 || mutex_owned(&fdp->fd_lock));
dt = fdp->fd_dt;
if (fdp->fd_refcnt == -1) {
/*
* fd_free tears down the table without maintaining its bitmap.
*/
return;
}
for (fd = 0; fd < dt->dt_nfiles; fd++) {
if (fd < NDFDFILE) {
KASSERT(dt->dt_ff[fd] ==
(fdfile_t *)fdp->fd_dfdfile[fd]);
}
if (dt->dt_ff[fd] == NULL) {
KASSERT(!fd_isused(fdp, fd));
} else if (dt->dt_ff[fd]->ff_file != NULL) {
KASSERT(fd_isused(fdp, fd));
}
}
#endif
}
static int
fd_next_zero(filedesc_t *fdp, uint32_t *bitmap, int want, u_int bits)
{
int i, off, maxoff;
uint32_t sub;
KASSERT(mutex_owned(&fdp->fd_lock));
fd_checkmaps(fdp);
if (want > bits)
return -1;
off = want >> NDENTRYSHIFT;
i = want & NDENTRYMASK;
if (i) {
sub = bitmap[off] | ((u_int)~0 >> (NDENTRIES - i));
if (sub != ~0)
goto found;
off++;
}
maxoff = NDLOSLOTS(bits);
while (off < maxoff) {
if ((sub = bitmap[off]) != ~0)
goto found;
off++;
}
return -1;
found:
return (off << NDENTRYSHIFT) + ffs(~sub) - 1;
}
static int
fd_last_set(filedesc_t *fd, int last)
{
int off, i;
fdfile_t **ff = fd->fd_dt->dt_ff;
uint32_t *bitmap = fd->fd_lomap;
KASSERT(mutex_owned(&fd->fd_lock));
fd_checkmaps(fd);
off = (last - 1) >> NDENTRYSHIFT;
while (off >= 0 && !bitmap[off])
off--;
if (off < 0)
return -1;
i = ((off + 1) << NDENTRYSHIFT) - 1;
if (i >= last)
i = last - 1;
/* XXX should use bitmap */
while (i > 0 && (ff[i] == NULL || !ff[i]->ff_allocated))
i--;
return i;
}
static inline void
fd_used(filedesc_t *fdp, unsigned fd)
{
u_int off = fd >> NDENTRYSHIFT;
fdfile_t *ff;
ff = fdp->fd_dt->dt_ff[fd];
KASSERT(mutex_owned(&fdp->fd_lock));
KASSERT((fdp->fd_lomap[off] & (1U << (fd & NDENTRYMASK))) == 0);
KASSERT(ff != NULL);
KASSERT(ff->ff_file == NULL);
KASSERT(!ff->ff_allocated);
ff->ff_allocated = true;
fdp->fd_lomap[off] |= 1U << (fd & NDENTRYMASK);
if (__predict_false(fdp->fd_lomap[off] == ~0)) {
KASSERT((fdp->fd_himap[off >> NDENTRYSHIFT] &
(1U << (off & NDENTRYMASK))) == 0);
fdp->fd_himap[off >> NDENTRYSHIFT] |= 1U << (off & NDENTRYMASK);
}
if ((int)fd > fdp->fd_lastfile) {
fdp->fd_lastfile = fd;
}
fd_checkmaps(fdp);
}
static inline void
fd_unused(filedesc_t *fdp, unsigned fd)
{
u_int off = fd >> NDENTRYSHIFT;
fdfile_t *ff;
ff = fdp->fd_dt->dt_ff[fd];
KASSERT(mutex_owned(&fdp->fd_lock));
KASSERT(ff != NULL);
KASSERT(ff->ff_file == NULL);
KASSERT(ff->ff_allocated);
if (fd < fdp->fd_freefile) {
fdp->fd_freefile = fd;
}
if (fdp->fd_lomap[off] == ~0) {
KASSERT((fdp->fd_himap[off >> NDENTRYSHIFT] &
(1U << (off & NDENTRYMASK))) != 0);
fdp->fd_himap[off >> NDENTRYSHIFT] &=
~(1U << (off & NDENTRYMASK));
}
KASSERT((fdp->fd_lomap[off] & (1U << (fd & NDENTRYMASK))) != 0);
fdp->fd_lomap[off] &= ~(1U << (fd & NDENTRYMASK));
ff->ff_allocated = false;
KASSERT(fd <= fdp->fd_lastfile);
if (fd == fdp->fd_lastfile) {
fdp->fd_lastfile = fd_last_set(fdp, fd);
}
fd_checkmaps(fdp);
}
/*
* Look up the file structure corresponding to a file descriptor
* and return the file, holding a reference on the descriptor.
*/
file_t *
fd_getfile(unsigned fd)
{
filedesc_t *fdp;
fdfile_t *ff;
file_t *fp;
fdtab_t *dt;
/*
* Look up the fdfile structure representing this descriptor.
* We are doing this unlocked. See fd_tryexpand().
*/
fdp = curlwp->l_fd;
dt = atomic_load_consume(&fdp->fd_dt);
if (__predict_false(fd >= dt->dt_nfiles)) {
return NULL;
}
ff = dt->dt_ff[fd];
KASSERT(fd >= NDFDFILE || ff == (fdfile_t *)fdp->fd_dfdfile[fd]);
if (__predict_false(ff == NULL)) {
return NULL;
}
/* Now get a reference to the descriptor. */
if (fdp->fd_refcnt == 1) {
/*
* Single threaded: don't need to worry about concurrent
* access (other than earlier calls to kqueue, which may
* hold a reference to the descriptor).
*/
ff->ff_refcnt++;
} else {
/*
* Multi threaded: issue a memory barrier to ensure that we
* acquire the file pointer _after_ adding a reference. If
* no memory barrier, we could fetch a stale pointer.
*
* In particular, we must coordinate the following four
* memory operations:
*
* A. fd_close store ff->ff_file = NULL
* B. fd_close refcnt = atomic_dec_uint_nv(&ff->ff_refcnt)
* C. fd_getfile atomic_inc_uint(&ff->ff_refcnt)
* D. fd_getfile load fp = ff->ff_file
*
* If the order is D;A;B;C:
*
* 1. D: fp = ff->ff_file
* 2. A: ff->ff_file = NULL
* 3. B: refcnt = atomic_dec_uint_nv(&ff->ff_refcnt)
* 4. C: atomic_inc_uint(&ff->ff_refcnt)
*
* then fd_close determines that there are no more
* references and decides to free fp immediately, at
* the same that fd_getfile ends up with an fp that's
* about to be freed. *boom*
*
* By making B a release operation in fd_close, and by
* making C an acquire operation in fd_getfile, since
* they are atomic operations on the same object, which
* has a total modification order, we guarantee either:
*
* - B happens before C. Then since A is
* sequenced before B in fd_close, and C is
* sequenced before D in fd_getfile, we
* guarantee A happens before D, so fd_getfile
* reads a null fp and safely fails.
*
* - C happens before B. Then fd_getfile may read
* null or nonnull, but either way, fd_close
* will safely wait for references to drain.
*/
atomic_inc_uint(&ff->ff_refcnt);
membar_acquire();
}
/*
* If the file is not open or is being closed then put the
* reference back.
*/
fp = atomic_load_consume(&ff->ff_file);
if (__predict_true(fp != NULL)) {
return fp;
}
fd_putfile(fd);
return NULL;
}
/*
* Release a reference to a file descriptor acquired with fd_getfile().
*/
void
fd_putfile(unsigned fd)
{
filedesc_t *fdp;
fdfile_t *ff;
u_int u, v;
fdp = curlwp->l_fd;
KASSERT(fd < atomic_load_consume(&fdp->fd_dt)->dt_nfiles);
ff = atomic_load_consume(&fdp->fd_dt)->dt_ff[fd];
KASSERT(ff != NULL);
KASSERT((ff->ff_refcnt & FR_MASK) > 0);
KASSERT(fd >= NDFDFILE || ff == (fdfile_t *)fdp->fd_dfdfile[fd]);
if (fdp->fd_refcnt == 1) {
/*
* Single threaded: don't need to worry about concurrent
* access (other than earlier calls to kqueue, which may
* hold a reference to the descriptor).
*/
if (__predict_false((ff->ff_refcnt & FR_CLOSING) != 0)) {
fd_close(fd);
return;
}
ff->ff_refcnt--;
return;
}
/*
* Ensure that any use of the file is complete and globally
* visible before dropping the final reference. If no membar,
* the current CPU could still access memory associated with
* the file after it has been freed or recycled by another
* CPU.
*/
membar_release();
/*
* Be optimistic and start out with the assumption that no other
* threads are trying to close the descriptor. If the CAS fails,
* we lost a race and/or it's being closed.
*/
for (u = ff->ff_refcnt & FR_MASK;; u = v) {
v = atomic_cas_uint(&ff->ff_refcnt, u, u - 1);
if (__predict_true(u == v)) {
return;
}
if (__predict_false((v & FR_CLOSING) != 0)) {
break;
}
}
/* Another thread is waiting to close the file: join it. */
(void)fd_close(fd);
}
/*
* Convenience wrapper around fd_getfile() that returns reference
* to a vnode.
*/
int
fd_getvnode(unsigned fd, file_t **fpp)
{
vnode_t *vp;
file_t *fp;
fp = fd_getfile(fd);
if (__predict_false(fp == NULL)) {
return EBADF;
}
if (__predict_false(fp->f_type != DTYPE_VNODE)) {
fd_putfile(fd);
return EINVAL;
}
vp = fp->f_vnode;
if (__predict_false(vp->v_type == VBAD)) {
/* XXX Is this case really necessary? */
fd_putfile(fd);
return EBADF;
}
*fpp = fp;
return 0;
}
/*
* Convenience wrapper around fd_getfile() that returns reference
* to a socket.
*/
int
fd_getsock1(unsigned fd, struct socket **sop, file_t **fp)
{
*fp = fd_getfile(fd);
if (__predict_false(*fp == NULL)) {
return EBADF;
}
if (__predict_false((*fp)->f_type != DTYPE_SOCKET)) {
fd_putfile(fd);
return ENOTSOCK;
}
*sop = (*fp)->f_socket;
return 0;
}
int
fd_getsock(unsigned fd, struct socket **sop)
{
file_t *fp;
return fd_getsock1(fd, sop, &fp);
}
/*
* Look up the file structure corresponding to a file descriptor
* and return it with a reference held on the file, not the
* descriptor.
*
* This is heavyweight and only used when accessing descriptors
* from a foreign process. The caller must ensure that `p' does
* not exit or fork across this call.
*
* To release the file (not descriptor) reference, use closef().
*/
file_t *
fd_getfile2(proc_t *p, unsigned fd)
{
filedesc_t *fdp;
fdfile_t *ff;
file_t *fp;
fdtab_t *dt;
fdp = p->p_fd;
mutex_enter(&fdp->fd_lock);
dt = fdp->fd_dt;
if (fd >= dt->dt_nfiles) {
mutex_exit(&fdp->fd_lock);
return NULL;
}
if ((ff = dt->dt_ff[fd]) == NULL) {
mutex_exit(&fdp->fd_lock);
return NULL;
}
if ((fp = atomic_load_consume(&ff->ff_file)) == NULL) {
mutex_exit(&fdp->fd_lock);
return NULL;
}
mutex_enter(&fp->f_lock);
fp->f_count++;
mutex_exit(&fp->f_lock);
mutex_exit(&fdp->fd_lock);
return fp;
}
/*
* Internal form of close. Must be called with a reference to the
* descriptor, and will drop the reference. When all descriptor
* references are dropped, releases the descriptor slot and a single
* reference to the file structure.
*/
int
fd_close(unsigned fd)
{
struct flock lf;
filedesc_t *fdp;
fdfile_t *ff;
file_t *fp;
proc_t *p;
lwp_t *l;
u_int refcnt;
l = curlwp;
p = l->l_proc;
fdp = l->l_fd;
ff = atomic_load_consume(&fdp->fd_dt)->dt_ff[fd];
KASSERT(fd >= NDFDFILE || ff == (fdfile_t *)fdp->fd_dfdfile[fd]);
mutex_enter(&fdp->fd_lock);
KASSERT((ff->ff_refcnt & FR_MASK) > 0);
fp = atomic_load_consume(&ff->ff_file);
if (__predict_false(fp == NULL)) {
/*
* Another user of the file is already closing, and is
* waiting for other users of the file to drain. Release
* our reference, and wake up the closer.
*/
membar_release();
atomic_dec_uint(&ff->ff_refcnt);
cv_broadcast(&ff->ff_closing);
mutex_exit(&fdp->fd_lock);
/*
* An application error, so pretend that the descriptor
* was already closed. We can't safely wait for it to
* be closed without potentially deadlocking.
*/
return (EBADF);
}
KASSERT((ff->ff_refcnt & FR_CLOSING) == 0);
/*
* There may be multiple users of this file within the process.
* Notify existing and new users that the file is closing. This
* will prevent them from adding additional uses to this file
* while we are closing it.
*/
atomic_store_relaxed(&ff->ff_file, NULL);
ff->ff_exclose = false;
/*
* We expect the caller to hold a descriptor reference - drop it.
* The reference count may increase beyond zero at this point due
* to an erroneous descriptor reference by an application, but
* fd_getfile() will notice that the file is being closed and drop
* the reference again.
*/
if (fdp->fd_refcnt == 1) {
/* Single threaded. */
refcnt = --(ff->ff_refcnt);
} else {
/* Multi threaded. */
membar_release();
refcnt = atomic_dec_uint_nv(&ff->ff_refcnt);
membar_acquire();
}
if (__predict_false(refcnt != 0)) {
/*
* Wait for other references to drain. This is typically
* an application error - the descriptor is being closed
* while still in use.
* (Or just a threaded application trying to unblock its
* thread that sleeps in (say) accept()).
*/
atomic_or_uint(&ff->ff_refcnt, FR_CLOSING);
/*
* Remove any knotes attached to the file. A knote
* attached to the descriptor can hold references on it.
*/
mutex_exit(&fdp->fd_lock);
if (!SLIST_EMPTY(&ff->ff_knlist)) {
knote_fdclose(fd);
}
/*
* Since the file system code doesn't know which fd
* each request came from (think dup()), we have to
* ask it to return ERESTART for any long-term blocks.
* The re-entry through read/write/etc will detect the
* closed fd and return EBAFD.
* Blocked partial writes may return a short length.
*/
(*fp->f_ops->fo_restart)(fp);
mutex_enter(&fdp->fd_lock);
/*
* We need to see the count drop to zero at least once,
* in order to ensure that all pre-existing references
* have been drained. New references past this point are
* of no interest.
* XXX (dsl) this may need to call fo_restart() after a
* timeout to guarantee that all the system calls exit.
*/
while ((ff->ff_refcnt & FR_MASK) != 0) {
cv_wait(&ff->ff_closing, &fdp->fd_lock);
}
atomic_and_uint(&ff->ff_refcnt, ~FR_CLOSING);
} else {
/* If no references, there must be no knotes. */
KASSERT(SLIST_EMPTY(&ff->ff_knlist));
}
/*
* POSIX record locking dictates that any close releases ALL
* locks owned by this process. This is handled by setting
* a flag in the unlock to free ONLY locks obeying POSIX
* semantics, and not to free BSD-style file locks.
* If the descriptor was in a message, POSIX-style locks
* aren't passed with the descriptor.
*/
if (__predict_false((p->p_flag & PK_ADVLOCK) != 0) &&
fp->f_ops->fo_advlock != NULL) {
lf.l_whence = SEEK_SET;
lf.l_start = 0;
lf.l_len = 0;
lf.l_type = F_UNLCK;
mutex_exit(&fdp->fd_lock);
(void)(*fp->f_ops->fo_advlock)(fp, p, F_UNLCK, &lf, F_POSIX);
mutex_enter(&fdp->fd_lock);
}
/* Free descriptor slot. */
fd_unused(fdp, fd);
mutex_exit(&fdp->fd_lock);
/* Now drop reference to the file itself. */
return closef(fp);
}
/*
* Duplicate a file descriptor.
*/
int
fd_dup(file_t *fp, int minfd, int *newp, bool exclose)
{
proc_t *p = curproc;
fdtab_t *dt;
int error;
while ((error = fd_alloc(p, minfd, newp)) != 0) {
if (error != ENOSPC) {
return error;
}
fd_tryexpand(p);
}
dt = atomic_load_consume(&curlwp->l_fd->fd_dt);
dt->dt_ff[*newp]->ff_exclose = exclose;
fd_affix(p, fp, *newp);
return 0;
}
/*
* dup2 operation.
*/
int
fd_dup2(file_t *fp, unsigned newfd, int flags)
{
filedesc_t *fdp = curlwp->l_fd;
fdfile_t *ff;
fdtab_t *dt;
if (flags & ~(O_CLOEXEC|O_NONBLOCK|O_NOSIGPIPE))
return EINVAL;
/*
* Ensure there are enough slots in the descriptor table,
* and allocate an fdfile_t up front in case we need it.
*/
while (newfd >= atomic_load_consume(&fdp->fd_dt)->dt_nfiles) {
fd_tryexpand(curproc);
}
ff = kmem_alloc(sizeof(*ff), KM_SLEEP);
fdfile_ctor(ff);
/*
* If there is already a file open, close it. If the file is
* half open, wait for it to be constructed before closing it.
* XXX Potential for deadlock here?
*/
mutex_enter(&fdp->fd_lock);
while (fd_isused(fdp, newfd)) {
mutex_exit(&fdp->fd_lock);
if (fd_getfile(newfd) != NULL) {
(void)fd_close(newfd);
} else {
/*
* Crummy, but unlikely to happen.
* Can occur if we interrupt another
* thread while it is opening a file.
*/
kpause("dup2", false, 1, NULL);
}
mutex_enter(&fdp->fd_lock);
}
dt = fdp->fd_dt;
if (dt->dt_ff[newfd] == NULL) {
KASSERT(newfd >= NDFDFILE);
dt->dt_ff[newfd] = ff;
ff = NULL;
}
fd_used(fdp, newfd);
mutex_exit(&fdp->fd_lock);
dt->dt_ff[newfd]->ff_exclose = (flags & O_CLOEXEC) != 0;
fp->f_flag |= flags & (FNONBLOCK|FNOSIGPIPE);
/* Slot is now allocated. Insert copy of the file. */
fd_affix(curproc, fp, newfd);
if (ff != NULL) {
cv_destroy(&ff->ff_closing);
kmem_free(ff, sizeof(*ff));
}
return 0;
}
/*
* Drop reference to a file structure.
*/
int
closef(file_t *fp)
{
struct flock lf;
int error;
/*
* Drop reference. If referenced elsewhere it's still open
* and we have nothing more to do.
*/
mutex_enter(&fp->f_lock);
KASSERT(fp->f_count > 0);
if (--fp->f_count > 0) {
mutex_exit(&fp->f_lock);
return 0;
}
KASSERT(fp->f_count == 0);
mutex_exit(&fp->f_lock);
/* We held the last reference - release locks, close and free. */
if (fp->f_ops->fo_advlock == NULL) {
KASSERT((fp->f_flag & FHASLOCK) == 0);
} else if (fp->f_flag & FHASLOCK) {
lf.l_whence = SEEK_SET;
lf.l_start = 0;
lf.l_len = 0;
lf.l_type = F_UNLCK;
(void)(*fp->f_ops->fo_advlock)(fp, fp, F_UNLCK, &lf, F_FLOCK);
}
if (fp->f_ops != NULL) {
error = (*fp->f_ops->fo_close)(fp);
} else {
error = 0;
}
KASSERT(fp->f_count == 0);
KASSERT(fp->f_cred != NULL);
pool_cache_put(file_cache, fp);
return error;
}
/*
* Allocate a file descriptor for the process.
*
* Future idea for experimentation: replace all of this with radixtree.
*/
int
fd_alloc(proc_t *p, int want, int *result)
{
filedesc_t *fdp = p->p_fd;
int i, lim, last, error, hi;
u_int off;
fdtab_t *dt;
KASSERT(p == curproc || p == &proc0);
/*
* Search for a free descriptor starting at the higher
* of want or fd_freefile.
*/
mutex_enter(&fdp->fd_lock);
fd_checkmaps(fdp);
dt = fdp->fd_dt;
KASSERT(dt->dt_ff[0] == (fdfile_t *)fdp->fd_dfdfile[0]);
lim = uimin((int)p->p_rlimit[RLIMIT_NOFILE].rlim_cur, maxfiles);
last = uimin(dt->dt_nfiles, lim);
for (;;) {
if ((i = want) < fdp->fd_freefile)
i = fdp->fd_freefile;
off = i >> NDENTRYSHIFT;
hi = fd_next_zero(fdp, fdp->fd_himap, off,
(last + NDENTRIES - 1) >> NDENTRYSHIFT);
if (hi == -1)
break;
i = fd_next_zero(fdp, &fdp->fd_lomap[hi],
hi > off ? 0 : i & NDENTRYMASK, NDENTRIES);
if (i == -1) {
/*
* Free file descriptor in this block was
* below want, try again with higher want.
*/
want = (hi + 1) << NDENTRYSHIFT;
continue;
}
i += (hi << NDENTRYSHIFT);
if (i >= last) {
break;
}
if (dt->dt_ff[i] == NULL) {
KASSERT(i >= NDFDFILE);
dt->dt_ff[i] = kmem_alloc(sizeof(fdfile_t), KM_SLEEP);
fdfile_ctor(dt->dt_ff[i]);
}
KASSERT(dt->dt_ff[i]->ff_file == NULL);
fd_used(fdp, i);
if (want <= fdp->fd_freefile) {
fdp->fd_freefile = i;
}
*result = i;
KASSERT(i >= NDFDFILE ||
dt->dt_ff[i] == (fdfile_t *)fdp->fd_dfdfile[i]);
fd_checkmaps(fdp);
mutex_exit(&fdp->fd_lock);
return 0;
}
/* No space in current array. Let the caller expand and retry. */
error = (dt->dt_nfiles >= lim) ? EMFILE : ENOSPC;
mutex_exit(&fdp->fd_lock);
return error;
}
/*
* Allocate memory for a descriptor table.
*/
static fdtab_t *
fd_dtab_alloc(int n)
{
fdtab_t *dt;
size_t sz;
KASSERT(n > NDFILE);
sz = sizeof(*dt) + (n - NDFILE) * sizeof(dt->dt_ff[0]);
dt = kmem_alloc(sz, KM_SLEEP);
#ifdef DIAGNOSTIC
memset(dt, 0xff, sz);
#endif
dt->dt_nfiles = n;
dt->dt_link = NULL;
return dt;
}
/*
* Free a descriptor table, and all tables linked for deferred free.
*/
static void
fd_dtab_free(fdtab_t *dt)
{
fdtab_t *next;
size_t sz;
do {
next = dt->dt_link;
KASSERT(dt->dt_nfiles > NDFILE);
sz = sizeof(*dt) +
(dt->dt_nfiles - NDFILE) * sizeof(dt->dt_ff[0]);
#ifdef DIAGNOSTIC
memset(dt, 0xff, sz);
#endif
kmem_free(dt, sz);
dt = next;
} while (dt != NULL);
}
/*
* Allocate descriptor bitmap.
*/
static void
fd_map_alloc(int n, uint32_t **lo, uint32_t **hi)
{
uint8_t *ptr;
size_t szlo, szhi;
KASSERT(n > NDENTRIES);
szlo = NDLOSLOTS(n) * sizeof(uint32_t);
szhi = NDHISLOTS(n) * sizeof(uint32_t);
ptr = kmem_alloc(szlo + szhi, KM_SLEEP);