1 /* $NetBSD: vfs_cwd.c,v 1.12 2024/12/07 02:11:42 riastradh 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 1.12 2024/12/07 02:11:42 riastradh Exp $"); 35 36 #include <sys/param.h> 37 38 #include <sys/atomic.h> 39 #include <sys/filedesc.h> 40 #include <sys/kmem.h> 41 #include <sys/proc.h> 42 #include <sys/vnode.h> 43 44 /* 45 * Create an initial cwdinfo structure, using the same current and root 46 * directories as curproc. 47 */ 48 struct cwdinfo * 49 cwdinit(void) 50 { 51 struct cwdinfo *cwdi; 52 struct cwdinfo *copy; 53 54 cwdi = kmem_alloc(sizeof(*cwdi), KM_SLEEP); 55 KASSERT(ALIGNED_POINTER(cwdi, COHERENCY_UNIT)); 56 rw_init(&cwdi->cwdi_lock); 57 copy = curproc->p_cwdi; 58 59 rw_enter(©->cwdi_lock, RW_READER); 60 cwdi->cwdi_cdir = copy->cwdi_cdir; 61 if (cwdi->cwdi_cdir) 62 vref(cwdi->cwdi_cdir); 63 cwdi->cwdi_rdir = copy->cwdi_rdir; 64 if (cwdi->cwdi_rdir) 65 vref(cwdi->cwdi_rdir); 66 cwdi->cwdi_edir = copy->cwdi_edir; 67 if (cwdi->cwdi_edir) 68 vref(cwdi->cwdi_edir); 69 rw_exit(©->cwdi_lock); 70 71 cwdi->cwdi_cmask = copy->cwdi_cmask; 72 cwdi->cwdi_refcnt = 1; 73 74 return cwdi; 75 } 76 77 /* 78 * Make p2 share p1's cwdinfo. 79 */ 80 void 81 cwdshare(struct proc *p2) 82 { 83 struct cwdinfo *cwdi; 84 85 cwdi = curproc->p_cwdi; 86 87 atomic_inc_uint(&cwdi->cwdi_refcnt); 88 p2->p_cwdi = cwdi; 89 } 90 91 /* 92 * Make sure proc has only one reference to its cwdi, creating 93 * a new one if necessary. 94 */ 95 void 96 cwdunshare(struct proc *p) 97 { 98 struct cwdinfo *cwdi = p->p_cwdi; 99 100 if (cwdi->cwdi_refcnt > 1) { 101 cwdi = cwdinit(); 102 cwdfree(p->p_cwdi); 103 p->p_cwdi = cwdi; 104 } 105 } 106 107 /* 108 * Release a cwdinfo structure. 109 */ 110 void 111 cwdfree(struct cwdinfo *cwdi) 112 { 113 114 membar_release(); 115 if (atomic_dec_uint_nv(&cwdi->cwdi_refcnt) > 0) 116 return; 117 membar_acquire(); 118 119 vrele(cwdi->cwdi_cdir); 120 rw_destroy(&cwdi->cwdi_lock); 121 if (cwdi->cwdi_rdir) 122 vrele(cwdi->cwdi_rdir); 123 if (cwdi->cwdi_edir) 124 vrele(cwdi->cwdi_edir); 125 kmem_free(cwdi, sizeof(*cwdi)); 126 } 127 128 void 129 cwdexec(struct proc *p) 130 { 131 132 cwdunshare(p); 133 134 if (p->p_cwdi->cwdi_edir) { 135 vrele(p->p_cwdi->cwdi_edir); 136 } 137 } 138