1 /* $NetBSD: kern_module_hook.c,v 1.4 2019/12/13 08:02:53 skrll Exp $ */ 2 3 /*- 4 * Copyright (c) 2019 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 * Kernel module support. 31 */ 32 33 #include <sys/cdefs.h> 34 __KERNEL_RCSID(0, "$NetBSD: kern_module_hook.c,v 1.4 2019/12/13 08:02:53 skrll Exp $"); 35 36 #include <sys/param.h> 37 38 #include <sys/atomic.h> 39 #include <sys/condvar.h> 40 #include <sys/module_hook.h> 41 #include <sys/mutex.h> 42 #include <sys/pserialize.h> 43 44 #include <uvm/uvm_extern.h> 45 46 /* Locking/synchronization stuff for module hooks */ 47 48 static struct { 49 kmutex_t mtx; 50 kcondvar_t cv; 51 pserialize_t psz; 52 } module_hook __cacheline_aligned; 53 54 /* 55 * We use pserialize_perform() to issue a memory barrier on the current 56 * CPU and on all other CPUs so that all prior memory operations on the 57 * current CPU globally happen before all subsequent memory operations 58 * on the current CPU, as perceived by any other CPU. 59 * 60 * pserialize_perform() might be rather heavy-weight here, but it only 61 * happens during module loading, and it allows MODULE_HOOK_CALL() to 62 * work without any other memory barriers. 63 */ 64 65 void 66 module_hook_set(bool *hooked, struct localcount *lc) 67 { 68 69 KASSERT(kernconfig_is_held()); 70 KASSERT(!*hooked); 71 72 localcount_init(lc); 73 74 /* Wait until setup has been witnessed by all CPUs. */ 75 pserialize_perform(module_hook.psz); 76 77 /* Let others use it */ 78 atomic_store_relaxed(hooked, true); 79 } 80 81 void 82 module_hook_unset(bool *hooked, struct localcount *lc) 83 { 84 85 KASSERT(kernconfig_is_held()); 86 KASSERT(*hooked); 87 88 /* Get exclusive with pserialize and localcount. */ 89 mutex_enter(&module_hook.mtx); 90 91 /* Prevent new calls to module_hook_tryenter(). */ 92 atomic_store_relaxed(hooked, false); 93 94 /* Wait for existing calls to module_hook_tryenter(). */ 95 pserialize_perform(module_hook.psz); 96 97 /* Wait for module_hook_exit. */ 98 localcount_drain(lc, &module_hook.cv, &module_hook.mtx); 99 100 /* All done! */ 101 mutex_exit(&module_hook.mtx); 102 localcount_fini(lc); 103 } 104 105 bool 106 module_hook_tryenter(bool *hooked, struct localcount *lc) 107 { 108 bool call_hook; 109 int s; 110 111 s = pserialize_read_enter(); 112 call_hook = atomic_load_relaxed(hooked); 113 if (call_hook) 114 localcount_acquire(lc); 115 pserialize_read_exit(s); 116 117 return call_hook; 118 } 119 120 void 121 module_hook_exit(struct localcount *lc) 122 { 123 124 localcount_release(lc, &module_hook.cv, &module_hook.mtx); 125 } 126 127 void 128 module_hook_init(void) 129 { 130 131 mutex_init(&module_hook.mtx, MUTEX_DEFAULT, IPL_NONE); 132 cv_init(&module_hook.cv, "mod_hook"); 133 module_hook.psz = pserialize_create(); 134 } 135