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 struct sysent *se;
63 int error, traced;
64 bool sy_thr_static;
65
66 VM_CNT_INC(v_syscall);
67 p = td->td_proc;
68 sa = &td->td_sa;
69
70 td->td_pticks = 0;
71 if (__predict_false(td->td_cowgen != p->p_cowgen))
72 thread_cow_update(td);
73 traced = (p->p_flag & P_TRACED) != 0;
74 if (__predict_false(traced || td->td_dbgflags & TDB_USERWR)) {
75 PROC_LOCK(p);
76 td->td_dbgflags &= ~TDB_USERWR;
77 if (traced)
78 td->td_dbgflags |= TDB_SCE;
79 PROC_UNLOCK(p);
80 }
81 error = (p->p_sysent->sv_fetch_syscall_args)(td);
82 se = sa->callp;
83 #ifdef KTRACE
84 if (KTRPOINT(td, KTR_SYSCALL))
85 ktrsyscall(sa->code, se->sy_narg, sa->args);
86 #endif
87 KTR_START4(KTR_SYSC, "syscall", syscallname(p, sa->code),
88 (uintptr_t)td, "pid:%d", td->td_proc->p_pid, "arg0:%p", sa->args[0],
89 "arg1:%p", sa->args[1], "arg2:%p", sa->args[2]);
90
91 if (__predict_false(error != 0)) {
92 td->td_errno = error;
93 goto retval;
94 }
95
96 if (__predict_false(traced)) {
97 PROC_LOCK(p);
98 if (p->p_ptevents & PTRACE_SCE)
99 ptracestop((td), SIGTRAP, NULL);
100 PROC_UNLOCK(p);
101
102 if ((td->td_dbgflags & TDB_USERWR) != 0) {
103 /*
104 * Reread syscall number and arguments if debugger
105 * modified registers or memory.
106 */
107 error = (p->p_sysent->sv_fetch_syscall_args)(td);
108 se = sa->callp;
109 #ifdef KTRACE
110 if (KTRPOINT(td, KTR_SYSCALL))
111 ktrsyscall(sa->code, se->sy_narg, sa->args);
112 #endif
113 if (error != 0) {
114 td->td_errno = error;
115 goto retval;
116 }
117 }
118 }
119
120 #ifdef CAPABILITY_MODE
121 /*
122 * In capability mode, we only allow access to system calls
123 * flagged with SYF_CAPENABLED.
124 */
125 if (__predict_false(IN_CAPABILITY_MODE(td) &&
126 (se->sy_flags & SYF_CAPENABLED) == 0)) {
127 td->td_errno = error = ECAPMODE;
128 goto retval;
129 }
130 #endif
131
132 /*
133 * Fetch fast sigblock value at the time of syscall entry to
134 * handle sleepqueue primitives which might call cursig().
135 */
136 if (__predict_false(sigfastblock_fetch_always))
137 (void)sigfastblock_fetch(td);
138
139 /* Let system calls set td_errno directly. */
140 KASSERT((td->td_pflags & TDP_NERRNO) == 0,
141 ("%s: TDP_NERRNO set", __func__));
142
143 sy_thr_static = (se->sy_thrcnt & SY_THR_STATIC) != 0;
144
145 if (__predict_false(SYSTRACE_ENABLED() ||
146 AUDIT_SYSCALL_ENTER(sa->code, td) ||
147 !sy_thr_static)) {
148 if (!sy_thr_static) {
149 error = syscall_thread_enter(td, se);
150 if (error != 0) {
151 td->td_errno = error;
152 goto retval;
153 }
154 }
155
156 #ifdef KDTRACE_HOOKS
157 /* Give the syscall:::entry DTrace probe a chance to fire. */
158 if (__predict_false(se->sy_entry != 0))
159 (*systrace_probe_func)(sa, SYSTRACE_ENTRY, 0);
160 #endif
161 error = (se->sy_call)(td, sa->args);
162 /* Save the latest error return value. */
163 if (__predict_false((td->td_pflags & TDP_NERRNO) != 0))
164 td->td_pflags &= ~TDP_NERRNO;
165 else
166 td->td_errno = error;
167
168 /*
169 * Note that some syscall implementations (e.g., sys_execve)
170 * will commit the audit record just before their final return.
171 * These were done under the assumption that nothing of interest
172 * would happen between their return and here, where we would
173 * normally commit the audit record. These assumptions will
174 * need to be revisited should any substantial logic be added
175 * above.
176 */
177 AUDIT_SYSCALL_EXIT(error, td);
178
179 #ifdef KDTRACE_HOOKS
180 /* Give the syscall:::return DTrace probe a chance to fire. */
181 if (__predict_false(se->sy_return != 0))
182 (*systrace_probe_func)(sa, SYSTRACE_RETURN,
183 error ? -1 : td->td_retval[0]);
184 #endif
185
186 if (!sy_thr_static)
187 syscall_thread_exit(td, se);
188 } else {
189 error = (se->sy_call)(td, sa->args);
190 /* Save the latest error return value. */
191 if (__predict_false((td->td_pflags & TDP_NERRNO) != 0))
192 td->td_pflags &= ~TDP_NERRNO;
193 else
194 td->td_errno = error;
195 }
196
197 retval:
198 KTR_STOP4(KTR_SYSC, "syscall", syscallname(p, sa->code),
199 (uintptr_t)td, "pid:%d", td->td_proc->p_pid, "error:%d", error,
200 "retval0:%#lx", td->td_retval[0], "retval1:%#lx",
201 td->td_retval[1]);
202 if (__predict_false(traced)) {
203 PROC_LOCK(p);
204 td->td_dbgflags &= ~TDB_SCE;
205 PROC_UNLOCK(p);
206 }
207 (p->p_sysent->sv_set_syscall_retval)(td, error);
208 }
209
210 static inline void
211 syscallret(struct thread *td)
212 {
213 struct proc *p;
214 struct syscall_args *sa;
215 ksiginfo_t ksi;
216 int traced;
217
218 KASSERT((td->td_pflags & TDP_FORKING) == 0,
219 ("fork() did not clear TDP_FORKING upon completion"));
220 KASSERT(td->td_errno != ERELOOKUP,
221 ("ERELOOKUP not consumed syscall %d", td->td_sa.code));
222
223 p = td->td_proc;
224 sa = &td->td_sa;
225 if (__predict_false(td->td_errno == ENOTCAPABLE ||
226 td->td_errno == ECAPMODE)) {
227 if ((trap_enotcap ||
228 (p->p_flag2 & P2_TRAPCAP) != 0) && IN_CAPABILITY_MODE(td)) {
229 ksiginfo_init_trap(&ksi);
230 ksi.ksi_signo = SIGTRAP;
231 ksi.ksi_errno = td->td_errno;
232 ksi.ksi_code = TRAP_CAP;
233 trapsignal(td, &ksi);
234 }
235 }
236
237 /*
238 * Handle reschedule and other end-of-syscall issues
239 */
240 userret(td, td->td_frame);
241
242 #ifdef KTRACE
243 if (KTRPOINT(td, KTR_SYSRET)) {
244 ktrsysret(sa->code, td->td_errno, td->td_retval[0]);
245 }
246 #endif
247
248 traced = 0;
249 if (__predict_false(p->p_flag & P_TRACED)) {
250 traced = 1;
251 PROC_LOCK(p);
252 td->td_dbgflags |= TDB_SCX;
253 PROC_UNLOCK(p);
254 }
255 if (__predict_false(traced ||
256 (td->td_dbgflags & (TDB_EXEC | TDB_FORK)) != 0)) {
257 PROC_LOCK(p);
258 /*
259 * If tracing the execed process, trap to the debugger
260 * so that breakpoints can be set before the program
261 * executes. If debugger requested tracing of syscall
262 * returns, do it now too.
263 */
264 if (traced &&
265 ((td->td_dbgflags & (TDB_FORK | TDB_EXEC)) != 0 ||
266 (p->p_ptevents & PTRACE_SCX) != 0))
267 ptracestop(td, SIGTRAP, NULL);
268 td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK);
269 PROC_UNLOCK(p);
270 }
271
272 if (__predict_false(td->td_pflags & TDP_RFPPWAIT))
273 fork_rfppwait(td);
274 }
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