1/* $NetBSD: kern_syscall.c,v 1.14 2015/11/30 23:34:47 pgoyette Exp $ */
2
3/*-
4 * Copyright (c) 2008 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software developed for The NetBSD Foundation
8 * by Andrew Doran.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32#include <sys/cdefs.h>
33__KERNEL_RCSID(0, "$NetBSD: kern_syscall.c,v 1.14 2015/11/30 23:34:47 pgoyette Exp $");
34
35#ifdef _KERNEL_OPT
36#include "opt_modular.h"
37#include "opt_syscall_debug.h"
38#include "opt_ktrace.h"
39#include "opt_ptrace.h"
40#include "opt_dtrace.h"
41#endif
42
43/* XXX To get syscall prototypes. */
44#define SYSVSHM
45#define SYSVSEM
46#define SYSVMSG
47
48#include <sys/param.h>
49#include <sys/module.h>
50#include <sys/sched.h>
51#include <sys/syscall.h>
52#include <sys/syscallargs.h>
53#include <sys/syscallvar.h>
54#include <sys/systm.h>
55#include <sys/xcall.h>
56#include <sys/ktrace.h>
57#include <sys/ptrace.h>
58
59int
60sys_nomodule(struct lwp *l, const void *v, register_t *retval)
61{
62#ifdef MODULAR
63
64 const struct sysent *sy;
65 const struct emul *em;
66 const struct sc_autoload *auto_list;
67 u_int code;
68
69 /*
70 * Restart the syscall if we interrupted a module unload that
71 * failed. Acquiring kernconfig_lock delays us until any unload
72 * has been completed or rolled back.
73 */
74 kernconfig_lock();
75 sy = l->l_sysent;
76 if (sy->sy_call != sys_nomodule) {
77 kernconfig_unlock();
78 return ERESTART;
79 }
80 /*
81 * Try to autoload a module to satisfy the request. If it
82 * works, retry the request.
83 */
84 em = l->l_proc->p_emul;
85 code = sy - em->e_sysent;
86
87 if ((auto_list = em->e_sc_autoload) != NULL)
88 for (; auto_list->al_code > 0; auto_list++) {
89 if (auto_list->al_code != code) {
90 continue;
91 }
92 if (module_autoload(auto_list->al_module,
93 MODULE_CLASS_ANY) != 0 ||
94 sy->sy_call == sys_nomodule) {
95 break;
96 }
97 kernconfig_unlock();
98 return ERESTART;
99 }
100 kernconfig_unlock();
101#endif /* MODULAR */
102
103 return sys_nosys(l, v, retval);
104}
105
106int
107syscall_establish(const struct emul *em, const struct syscall_package *sp)
108{
109 struct sysent *sy;
110 int i;
111
112 KASSERT(kernconfig_is_held());
113
114 if (em == NULL) {
115 em = &emul_netbsd;
116 }
117 sy = em->e_sysent;
118
119 /*
120 * Ensure that all preconditions are valid, since this is
121 * an all or nothing deal. Once a system call is entered,
122 * it can become busy and we could be unable to remove it
123 * on error.
124 */
125 for (i = 0; sp[i].sp_call != NULL; i++) {
126 if (sy[sp[i].sp_code].sy_call != sys_nomodule) {
127#ifdef DIAGNOSTIC
128 printf("syscall %d is busy\n", sp[i].sp_code);
129#endif
130 return EBUSY;
131 }
132 }
133 /* Everything looks good, patch them in. */
134 for (i = 0; sp[i].sp_call != NULL; i++) {
135 sy[sp[i].sp_code].sy_call = sp[i].sp_call;
136 }
137
138 return 0;
139}
140
141int
142syscall_disestablish(const struct emul *em, const struct syscall_package *sp)
143{
144 struct sysent *sy;
145 uint64_t where;
146 lwp_t *l;
147 int i;
148
149 KASSERT(kernconfig_is_held());
150
151 if (em == NULL) {
152 em = &emul_netbsd;
153 }
154 sy = em->e_sysent;
155
156 /*
157 * First, patch the system calls to sys_nomodule to gate further
158 * activity.
159 */
160 for (i = 0; sp[i].sp_call != NULL; i++) {
161 KASSERT(sy[sp[i].sp_code].sy_call == sp[i].sp_call);
162 sy[sp[i].sp_code].sy_call = sys_nomodule;
163 }
164
165 /*
166 * Run a cross call to cycle through all CPUs. This does two
167 * things: lock activity provides a barrier and makes our update
168 * of sy_call visible to all CPUs, and upon return we can be sure
169 * that we see pertinent values of l_sysent posted by remote CPUs.
170 */
171 where = xc_broadcast(0, (xcfunc_t)nullop, NULL, NULL);
172 xc_wait(where);
173
174 /*
175 * Now it's safe to check l_sysent. Run through all LWPs and see
176 * if anyone is still using the system call.
177 */
178 for (i = 0; sp[i].sp_call != NULL; i++) {
179 mutex_enter(proc_lock);
180 LIST_FOREACH(l, &alllwp, l_list) {
181 if (l->l_sysent == &sy[sp[i].sp_code]) {
182 break;
183 }
184 }
185 mutex_exit(proc_lock);
186 if (l == NULL) {
187 continue;
188 }
189 /*
190 * We lose: one or more calls are still in use. Put back
191 * the old entrypoints and act like nothing happened.
192 * When we drop kernconfig_lock, any system calls held in
193 * sys_nomodule() will be restarted.
194 */
195 for (i = 0; sp[i].sp_call != NULL; i++) {
196 sy[sp[i].sp_code].sy_call = sp[i].sp_call;
197 }
198 return EBUSY;
199 }
200
201 return 0;
202}
203
204/*
205 * Return true if system call tracing is enabled for the specified process.
206 */
207bool
208trace_is_enabled(struct proc *p)
209{
210#ifdef SYSCALL_DEBUG
211 return (true);
212#endif
213#ifdef KTRACE
214 if (ISSET(p->p_traceflag, (KTRFAC_SYSCALL | KTRFAC_SYSRET)))
215 return (true);
216#endif
217#ifdef PTRACE
218 if (ISSET(p->p_slflag, PSL_SYSCALL))
219 return (true);
220#endif
221
222 return (false);
223}
224
225/*
226 * Start trace of particular system call. If process is being traced,
227 * this routine is called by MD syscall dispatch code just before
228 * a system call is actually executed.
229 */
230int
231trace_enter(register_t code, const struct sysent *sy, const void *args)
232{
233 int error = 0;
234
235#ifdef KDTRACE_HOOKS
236 if (sy->sy_entry) {
237 struct emul *e = curlwp->l_proc->p_emul;
238 (*e->e_dtrace_syscall)(sy->sy_entry, code, sy, args, NULL, 0);
239 }
240#endif
241
242#ifdef SYSCALL_DEBUG
243 scdebug_call(code, args);
244#endif /* SYSCALL_DEBUG */
245
246 ktrsyscall(code, args, sy->sy_narg);
247
248#ifdef PTRACE
249 if ((curlwp->l_proc->p_slflag & (PSL_SYSCALL|PSL_TRACED)) ==
250 (PSL_SYSCALL|PSL_TRACED)) {
251 process_stoptrace();
252 if (curlwp->l_proc->p_slflag & PSL_SYSCALLEMU) {
253 /* tracer will emulate syscall for us */
254 error = EJUSTRETURN;
255 }
256 }
257#endif
258 return error;
259}
260
261/*
262 * End trace of particular system call. If process is being traced,
263 * this routine is called by MD syscall dispatch code just after
264 * a system call finishes.
265 * MD caller guarantees the passed 'code' is within the supported
266 * system call number range for emulation the process runs under.
267 */
268void
269trace_exit(register_t code, const struct sysent *sy, const void *args,
270 register_t rval[], int error)
271{
272#if defined(PTRACE) || defined(KDTRACE_HOOKS)
273 struct proc *p = curlwp->l_proc;
274#endif
275
276#ifdef KDTRACE_HOOKS
277 if (sy->sy_return) {
278 (*p->p_emul->e_dtrace_syscall)(sy->sy_return, code, sy, args,
279 rval, error);
280 }
281#endif
282
283#ifdef SYSCALL_DEBUG
284 scdebug_ret(code, error, rval);
285#endif /* SYSCALL_DEBUG */
286
287 ktrsysret(code, error, rval);
288
289#ifdef PTRACE
290 if ((p->p_slflag & (PSL_SYSCALL|PSL_TRACED|PSL_SYSCALLEMU)) ==
291 (PSL_SYSCALL|PSL_TRACED))
292 process_stoptrace();
293 CLR(p->p_slflag, PSL_SYSCALLEMU);
294#endif
295}
296