78022527bb
kern_execve() locks text vnode exclusive to be able to set and clear VV_TEXT flag. VV_TEXT is mutually exclusive with the v_writecount > 0 condition. The change removes VV_TEXT, replacing it with the condition v_writecount <= -1, and puts v_writecount under the vnode interlock. Each text reference decrements v_writecount. To clear the text reference when the segment is unmapped, it is recorded in the vm_map_entry backed by the text file as MAP_ENTRY_VN_TEXT flag, and v_writecount is incremented on the map entry removal The operations like VOP_ADD_WRITECOUNT() and VOP_SET_TEXT() check that v_writecount does not contradict the desired change. vn_writecheck() is now racy and its use was eliminated everywhere except access. Atomic check for writeability and increment of v_writecount is performed by the VOP. vn_truncate() now increments v_writecount around VOP_SETATTR() call, lack of which is arguably a bug on its own. nullfs bypasses v_writecount to the lower vnode always, so nullfs vnode has its own v_writecount correct, and lower vnode gets all references, since object->handle is always lower vnode. On the text vnode' vm object dealloc, the v_writecount value is reset to zero, and deadfs vop_unset_text short-circuit the operation. Reclamation of lowervp always reclaims all nullfs vnodes referencing lowervp first, so no stray references are left. Reviewed by: markj, trasz Tested by: mjg, pho Sponsored by: The FreeBSD Foundation MFC after: 1 month Differential revision: https://reviews.freebsd.org/D19923
160 lines
3.9 KiB
C
160 lines
3.9 KiB
C
/*-
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 1989, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)dead_vnops.c 8.1 (Berkeley) 6/10/93
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* $FreeBSD$
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/poll.h>
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#include <sys/vnode.h>
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/*
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* Prototypes for dead operations on vnodes.
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*/
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static vop_lookup_t dead_lookup;
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static vop_open_t dead_open;
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static vop_getwritemount_t dead_getwritemount;
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static vop_rename_t dead_rename;
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static vop_unset_text_t dead_unset_text;
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struct vop_vector dead_vnodeops = {
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.vop_default = &default_vnodeops,
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.vop_access = VOP_EBADF,
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.vop_advlock = VOP_EBADF,
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.vop_bmap = VOP_EBADF,
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.vop_create = VOP_PANIC,
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.vop_getattr = VOP_EBADF,
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.vop_getwritemount = dead_getwritemount,
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.vop_inactive = VOP_NULL,
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.vop_ioctl = VOP_EBADF,
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.vop_link = VOP_PANIC,
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.vop_lookup = dead_lookup,
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.vop_mkdir = VOP_PANIC,
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.vop_mknod = VOP_PANIC,
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.vop_open = dead_open,
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.vop_pathconf = VOP_EBADF, /* per pathconf(2) */
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.vop_poll = dead_poll,
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.vop_read = dead_read,
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.vop_readdir = VOP_EBADF,
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.vop_readlink = VOP_EBADF,
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.vop_reclaim = VOP_NULL,
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.vop_remove = VOP_PANIC,
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.vop_rename = dead_rename,
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.vop_rmdir = VOP_PANIC,
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.vop_setattr = VOP_EBADF,
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.vop_symlink = VOP_PANIC,
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.vop_vptocnp = VOP_EBADF,
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.vop_unset_text = dead_unset_text,
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.vop_write = dead_write,
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};
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static int
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dead_getwritemount(struct vop_getwritemount_args *ap)
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{
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*(ap->a_mpp) = NULL;
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return (0);
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}
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/*
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* Trivial lookup routine that always fails.
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*/
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static int
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dead_lookup(struct vop_lookup_args *ap)
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{
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*ap->a_vpp = NULL;
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return (ENOTDIR);
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}
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/*
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* Open always fails as if device did not exist.
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*/
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static int
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dead_open(struct vop_open_args *ap)
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{
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return (ENXIO);
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}
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int
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dead_read(struct vop_read_args *ap)
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{
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/*
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* Return EOF for tty devices, EIO for others
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*/
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if ((ap->a_vp->v_vflag & VV_ISTTY) == 0)
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return (EIO);
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return (0);
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}
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int
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dead_write(struct vop_write_args *ap)
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{
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return (EIO);
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}
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int
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dead_poll(struct vop_poll_args *ap)
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{
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if (ap->a_events & ~POLLSTANDARD)
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return (POLLNVAL);
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/*
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* Let the user find out that the descriptor is gone.
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*/
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return (POLLHUP | ((POLLIN | POLLRDNORM) & ap->a_events));
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}
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static int
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dead_rename(struct vop_rename_args *ap)
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{
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vop_rename_fail(ap);
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return (EXDEV);
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}
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static int
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dead_unset_text(struct vop_unset_text_args *ap)
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{
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return (0);
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}
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