1 /* $NetBSD: vfs_cwd.c,v 1.11 2023/09/23 18:21:11 ad Exp $ */ 2 3 /*- 4 * Copyright (c) 2008, 2020, 2023 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 17 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 18 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 19 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 20 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 26 * POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 /* 30 * Current working directory. 31 */ 32 33 #include <sys/cdefs.h> 34 __KERNEL_RCSID(0, "$NetBSD: vfs_cwd.c,v 1.11 2023/09/23 18:21:11 ad Exp $"); 35 36 #include <sys/param.h> 37 #include <sys/atomic.h> 38 #include <sys/filedesc.h> 39 #include <sys/proc.h> 40 #include <sys/vnode.h> 41 #include <sys/kmem.h> 42 43 /* 44 * Create an initial cwdinfo structure, using the same current and root 45 * directories as curproc. 46 */ 47 struct cwdinfo * 48 cwdinit(void) 49 { 50 struct cwdinfo *cwdi; 51 struct cwdinfo *copy; 52 53 cwdi = kmem_alloc(sizeof(*cwdi), KM_SLEEP); 54 KASSERT(ALIGNED_POINTER(cwdi, COHERENCY_UNIT)); 55 rw_init(&cwdi->cwdi_lock); 56 copy = curproc->p_cwdi; 57 58 rw_enter(©->cwdi_lock, RW_READER); 59 cwdi->cwdi_cdir = copy->cwdi_cdir; 60 if (cwdi->cwdi_cdir) 61 vref(cwdi->cwdi_cdir); 62 cwdi->cwdi_rdir = copy->cwdi_rdir; 63 if (cwdi->cwdi_rdir) 64 vref(cwdi->cwdi_rdir); 65 cwdi->cwdi_edir = copy->cwdi_edir; 66 if (cwdi->cwdi_edir) 67 vref(cwdi->cwdi_edir); 68 rw_exit(©->cwdi_lock); 69 70 cwdi->cwdi_cmask = copy->cwdi_cmask; 71 cwdi->cwdi_refcnt = 1; 72 73 return (cwdi); 74 } 75 76 /* 77 * Make p2 share p1's cwdinfo. 78 */ 79 void 80 cwdshare(struct proc *p2) 81 { 82 struct cwdinfo *cwdi; 83 84 cwdi = curproc->p_cwdi; 85 86 atomic_inc_uint(&cwdi->cwdi_refcnt); 87 p2->p_cwdi = cwdi; 88 } 89 90 /* 91 * Make sure proc has only one reference to its cwdi, creating 92 * a new one if necessary. 93 */ 94 void 95 cwdunshare(struct proc *p) 96 { 97 struct cwdinfo *cwdi = p->p_cwdi; 98 99 if (cwdi->cwdi_refcnt > 1) { 100 cwdi = cwdinit(); 101 cwdfree(p->p_cwdi); 102 p->p_cwdi = cwdi; 103 } 104 } 105 106 /* 107 * Release a cwdinfo structure. 108 */ 109 void 110 cwdfree(struct cwdinfo *cwdi) 111 { 112 113 membar_release(); 114 if (atomic_dec_uint_nv(&cwdi->cwdi_refcnt) > 0) 115 return; 116 membar_acquire(); 117 118 vrele(cwdi->cwdi_cdir); 119 rw_destroy(&cwdi->cwdi_lock); 120 if (cwdi->cwdi_rdir) 121 vrele(cwdi->cwdi_rdir); 122 if (cwdi->cwdi_edir) 123 vrele(cwdi->cwdi_edir); 124 kmem_free(cwdi, sizeof(*cwdi)); 125 } 126 127 void 128 cwdexec(struct proc *p) 129 { 130 131 cwdunshare(p); 132 133 if (p->p_cwdi->cwdi_edir) { 134 vrele(p->p_cwdi->cwdi_edir); 135 } 136 } 137