1 /*-
2 * SPDX-License-Identifier: BSD-4-Clause
3 *
4 * Copyright (C) 1994, David Greenman
5 * Copyright (c) 1990, 1993
6 * The Regents of the University of California. All rights reserved.
7 * Copyright (C) 2010 Konstantin Belousov <kib@freebsd.org>
8 *
9 * This code is derived from software contributed to Berkeley by
10 * the University of Utah, and William Jolitz.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. All advertising materials mentioning features or use of this software
21 * must display the following acknowledgement:
22 * This product includes software developed by the University of
23 * California, Berkeley and its contributors.
24 * 4. Neither the name of the University nor the names of its contributors
25 * may be used to endorse or promote products derived from this software
26 * without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38 * SUCH DAMAGE.
39 *
40 * from: @(#)trap.c 7.4 (Berkeley) 5/13/91
41 */
42
43 #include "opt_capsicum.h"
44 #include "opt_ktrace.h"
45
46 __FBSDID("$FreeBSD$");
47
48 #include <sys/capsicum.h>
49 #include <sys/ktr.h>
50 #include <sys/vmmeter.h>
51 #ifdef KTRACE
52 #include <sys/uio.h>
53 #include <sys/ktrace.h>
54 #endif
55 #include <security/audit/audit.h>
56
57 static inline void
58 syscallenter(struct thread *td)
59 {
60 struct proc *p;
61 struct syscall_args *sa;
62 int error, traced;
63
64 VM_CNT_INC(v_syscall);
65 p = td->td_proc;
66 sa = &td->td_sa;
67
68 td->td_pticks = 0;
69 if (td->td_cowgen != p->p_cowgen)
70 thread_cow_update(td);
71 traced = (p->p_flag & P_TRACED) != 0;
72 if (traced || td->td_dbgflags & TDB_USERWR) {
73 PROC_LOCK(p);
74 td->td_dbgflags &= ~TDB_USERWR;
75 if (traced)
76 td->td_dbgflags |= TDB_SCE;
77 PROC_UNLOCK(p);
78 }
79 error = (p->p_sysent->sv_fetch_syscall_args)(td);
80 #ifdef KTRACE
81 if (KTRPOINT(td, KTR_SYSCALL))
82 ktrsyscall(sa->code, sa->narg, sa->args);
83 #endif
84 KTR_START4(KTR_SYSC, "syscall", syscallname(p, sa->code),
85 (uintptr_t)td, "pid:%d", td->td_proc->p_pid, "arg0:%p", sa->args[0],
86 "arg1:%p", sa->args[1], "arg2:%p", sa->args[2]);
87
88 if (error != 0) {
89 td->td_errno = error;
90 goto retval;
91 }
92
93 STOPEVENT(p, S_SCE, sa->narg);
94 if ((p->p_flag & P_TRACED) != 0) {
95 PROC_LOCK(p);
96 if (p->p_ptevents & PTRACE_SCE)
97 ptracestop((td), SIGTRAP, NULL);
98 PROC_UNLOCK(p);
99 }
100 if ((td->td_dbgflags & TDB_USERWR) != 0) {
101 /*
102 * Reread syscall number and arguments if debugger
103 * modified registers or memory.
104 */
105 error = (p->p_sysent->sv_fetch_syscall_args)(td);
106 #ifdef KTRACE
107 if (KTRPOINT(td, KTR_SYSCALL))
108 ktrsyscall(sa->code, sa->narg, sa->args);
109 #endif
110 if (error != 0) {
111 td->td_errno = error;
112 goto retval;
113 }
114 }
115
116 #ifdef CAPABILITY_MODE
117 /*
118 * In capability mode, we only allow access to system calls
119 * flagged with SYF_CAPENABLED.
120 */
121 if (IN_CAPABILITY_MODE(td) &&
122 !(sa->callp->sy_flags & SYF_CAPENABLED)) {
123 td->td_errno = error = ECAPMODE;
124 goto retval;
125 }
126 #endif
127
128 error = syscall_thread_enter(td, sa->callp);
129 if (error != 0) {
130 td->td_errno = error;
131 goto retval;
132 }
133
134 #ifdef KDTRACE_HOOKS
135 /* Give the syscall:::entry DTrace probe a chance to fire. */
136 if (__predict_false(systrace_enabled && sa->callp->sy_entry != 0))
137 (*systrace_probe_func)(sa, SYSTRACE_ENTRY, 0);
138 #endif
139
140 /* Let system calls set td_errno directly. */
141 td->td_pflags &= ~TDP_NERRNO;
142
143 AUDIT_SYSCALL_ENTER(sa->code, td);
144 error = (sa->callp->sy_call)(td, sa->args);
145
146 /*
147 * Note that some syscall implementations (e.g., sys_execve)
148 * will commit the audit record just before their final return.
149 * These were done under the assumption that nothing of interest
150 * would happen between their return and here, where we would
151 * normally commit the audit record. These assumptions will
152 * need to be revisited should any substantial logic be added
153 * above.
154 */
155 AUDIT_SYSCALL_EXIT(error, td);
156
157 /* Save the latest error return value. */
158 if ((td->td_pflags & TDP_NERRNO) == 0)
159 td->td_errno = error;
160
161 #ifdef KDTRACE_HOOKS
162 /* Give the syscall:::return DTrace probe a chance to fire. */
163 if (__predict_false(systrace_enabled && sa->callp->sy_return != 0))
164 (*systrace_probe_func)(sa, SYSTRACE_RETURN,
165 error ? -1 : td->td_retval[0]);
166 #endif
167 syscall_thread_exit(td, sa->callp);
168
169 retval:
170 KTR_STOP4(KTR_SYSC, "syscall", syscallname(p, sa->code),
171 (uintptr_t)td, "pid:%d", td->td_proc->p_pid, "error:%d", error,
172 "retval0:%#lx", td->td_retval[0], "retval1:%#lx",
173 td->td_retval[1]);
174 if (traced) {
175 PROC_LOCK(p);
176 td->td_dbgflags &= ~TDB_SCE;
177 PROC_UNLOCK(p);
178 }
179 (p->p_sysent->sv_set_syscall_retval)(td, error);
180 }
181
182 static inline void
183 syscallret(struct thread *td)
184 {
185 struct proc *p, *p2;
186 struct syscall_args *sa;
187 ksiginfo_t ksi;
188 int traced;
189
190 KASSERT((td->td_pflags & TDP_FORKING) == 0,
191 ("fork() did not clear TDP_FORKING upon completion"));
192
193 p = td->td_proc;
194 sa = &td->td_sa;
195 if ((trap_enotcap || (p->p_flag2 & P2_TRAPCAP) != 0) &&
196 IN_CAPABILITY_MODE(td)) {
197 if (td->td_errno == ENOTCAPABLE || td->td_errno == ECAPMODE) {
198 ksiginfo_init_trap(&ksi);
199 ksi.ksi_signo = SIGTRAP;
200 ksi.ksi_errno = td->td_errno;
201 ksi.ksi_code = TRAP_CAP;
202 trapsignal(td, &ksi);
203 }
204 }
205
206 /*
207 * Handle reschedule and other end-of-syscall issues
208 */
209 userret(td, td->td_frame);
210
211 #ifdef KTRACE
212 if (KTRPOINT(td, KTR_SYSRET)) {
213 ktrsysret(sa->code, td->td_errno, td->td_retval[0]);
214 }
215 #endif
216
217 if (p->p_flag & P_TRACED) {
218 traced = 1;
219 PROC_LOCK(p);
220 td->td_dbgflags |= TDB_SCX;
221 PROC_UNLOCK(p);
222 } else
223 traced = 0;
224 /*
225 * This works because errno is findable through the
226 * register set. If we ever support an emulation where this
227 * is not the case, this code will need to be revisited.
228 */
229 STOPEVENT(p, S_SCX, sa->code);
230 if (traced || (td->td_dbgflags & (TDB_EXEC | TDB_FORK)) != 0) {
231 PROC_LOCK(p);
232 /*
233 * If tracing the execed process, trap to the debugger
234 * so that breakpoints can be set before the program
235 * executes. If debugger requested tracing of syscall
236 * returns, do it now too.
237 */
238 if (traced &&
239 ((td->td_dbgflags & (TDB_FORK | TDB_EXEC)) != 0 ||
240 (p->p_ptevents & PTRACE_SCX) != 0))
241 ptracestop(td, SIGTRAP, NULL);
242 td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK);
243 PROC_UNLOCK(p);
244 }
245
246 if (td->td_pflags & TDP_RFPPWAIT) {
247 /*
248 * Preserve synchronization semantics of vfork. If
249 * waiting for child to exec or exit, fork set
250 * P_PPWAIT on child, and there we sleep on our proc
251 * (in case of exit).
252 *
253 * Do it after the ptracestop() above is finished, to
254 * not block our debugger until child execs or exits
255 * to finish vfork wait.
256 */
257 td->td_pflags &= ~TDP_RFPPWAIT;
258 p2 = td->td_rfppwait_p;
259 again:
260 PROC_LOCK(p2);
261 while (p2->p_flag & P_PPWAIT) {
262 PROC_LOCK(p);
263 if (thread_suspend_check_needed()) {
264 PROC_UNLOCK(p2);
265 thread_suspend_check(0);
266 PROC_UNLOCK(p);
267 goto again;
268 } else {
269 PROC_UNLOCK(p);
270 }
271 cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz);
272 }
273 PROC_UNLOCK(p2);
274
275 if (td->td_dbgflags & TDB_VFORK) {
276 PROC_LOCK(p);
277 if (p->p_ptevents & PTRACE_VFORK)
278 ptracestop(td, SIGTRAP, NULL);
279 td->td_dbgflags &= ~TDB_VFORK;
280 PROC_UNLOCK(p);
281 }
282 }
283 }
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