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
41 #include "opt_capsicum.h"
42 #include "opt_ktrace.h"
43 #include <sys/capsicum.h>
44 #include <sys/ktr.h>
45 #include <sys/vmmeter.h>
46 #ifdef KTRACE
47 #include <sys/uio.h>
48 #include <sys/ktrace.h>
49 #endif
50 #include <security/audit/audit.h>
51
52 static inline void
syscallenter(struct thread * td)53 syscallenter(struct thread *td)
54 {
55 struct proc *p;
56 struct syscall_args *sa;
57 struct sysent *se;
58 int error, traced;
59 bool sy_thr_static;
60
61 VM_CNT_INC(v_syscall);
62 p = td->td_proc;
63 sa = &td->td_sa;
64
65 td->td_pticks = 0;
66 if (__predict_false(td->td_cowgen != atomic_load_int(&p->p_cowgen)))
67 thread_cow_update(td);
68 traced = (p->p_flag & P_TRACED) != 0;
69 if (__predict_false(traced || td->td_dbgflags & TDB_USERWR)) {
70 PROC_LOCK(p);
71 MPASS((td->td_dbgflags & TDB_BOUNDARY) == 0);
72 td->td_dbgflags &= ~TDB_USERWR;
73 if (traced)
74 td->td_dbgflags |= TDB_SCE;
75 PROC_UNLOCK(p);
76 }
77 if ((td->td_pflags2 & TDP2_UEXTERR) != 0)
78 td->td_pflags2 &= ~TDP2_EXTERR;
79 error = (p->p_sysent->sv_fetch_syscall_args)(td);
80 se = sa->callp;
81 #ifdef KTRACE
82 if (KTRPOINT(td, KTR_SYSCALL))
83 ktrsyscall(sa->code, se->sy_narg, sa->args);
84 #endif
85 KTR_START4(KTR_SYSC, "syscall", syscallname(p, sa->code),
86 (uintptr_t)td, "pid:%d", td->td_proc->p_pid, "arg0:%p", sa->args[0],
87 "arg1:%p", sa->args[1], "arg2:%p", sa->args[2]);
88
89 if (__predict_false(error != 0)) {
90 td->td_errno = error;
91 goto retval;
92 }
93
94 if (__predict_false(traced)) {
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 se = sa->callp;
107 #ifdef KTRACE
108 if (KTRPOINT(td, KTR_SYSCALL))
109 ktrsyscall(sa->code, se->sy_narg, sa->args);
110 #endif
111 if (error != 0) {
112 td->td_errno = error;
113 goto retval;
114 }
115 }
116 }
117
118 #ifdef CAPABILITY_MODE
119 /*
120 * In capability mode, we only allow access to system calls
121 * flagged with SYF_CAPENABLED.
122 */
123 if ((se->sy_flags & SYF_CAPENABLED) == 0) {
124 if (CAP_TRACING(td))
125 ktrcapfail(CAPFAIL_SYSCALL, NULL);
126 if (IN_CAPABILITY_MODE(td)) {
127 td->td_errno = error = ECAPMODE;
128 goto retval;
129 }
130 }
131 #endif
132
133 /*
134 * Fetch fast sigblock value at the time of syscall entry to
135 * handle sleepqueue primitives which might call cursig().
136 */
137 if (__predict_false(sigfastblock_fetch_always))
138 (void)sigfastblock_fetch(td);
139
140 /* Let system calls set td_errno directly. */
141 KASSERT((td->td_pflags & TDP_NERRNO) == 0,
142 ("%s: TDP_NERRNO set", __func__));
143
144 sy_thr_static = (se->sy_thrcnt & SY_THR_STATIC) != 0;
145
146 if (__predict_false(AUDIT_SYSCALL_ENABLED() ||
147 SYSTRACE_ENABLED() || !sy_thr_static)) {
148 if (!sy_thr_static) {
149 error = syscall_thread_enter(td, &se);
150 sy_thr_static = (se->sy_thrcnt & SY_THR_STATIC) != 0;
151 if (error != 0) {
152 td->td_errno = error;
153 goto retval;
154 }
155 }
156
157 #ifdef KDTRACE_HOOKS
158 /* Give the syscall:::entry DTrace probe a chance to fire. */
159 if (__predict_false(se->sy_entry != 0))
160 (*systrace_probe_func)(sa, SYSTRACE_ENTRY, 0);
161 #endif
162
163 AUDIT_SYSCALL_ENTER(sa->code, td);
164
165 error = (se->sy_call)(td, sa->args);
166 /* Save the latest error return value. */
167 if (__predict_false((td->td_pflags & TDP_NERRNO) != 0))
168 td->td_pflags &= ~TDP_NERRNO;
169 else
170 td->td_errno = error;
171
172 /*
173 * Note that some syscall implementations (e.g., sys_execve)
174 * will commit the audit record just before their final return.
175 * These were done under the assumption that nothing of interest
176 * would happen between their return and here, where we would
177 * normally commit the audit record. These assumptions will
178 * need to be revisited should any substantial logic be added
179 * above.
180 */
181 AUDIT_SYSCALL_EXIT(error, td);
182
183 #ifdef KDTRACE_HOOKS
184 /* Give the syscall:::return DTrace probe a chance to fire. */
185 if (__predict_false(se->sy_return != 0))
186 (*systrace_probe_func)(sa, SYSTRACE_RETURN,
187 error ? -1 : td->td_retval[0]);
188 #endif
189
190 if (!sy_thr_static)
191 syscall_thread_exit(td, se);
192 } else {
193 error = (se->sy_call)(td, sa->args);
194 /* Save the latest error return value. */
195 if (__predict_false((td->td_pflags & TDP_NERRNO) != 0))
196 td->td_pflags &= ~TDP_NERRNO;
197 else
198 td->td_errno = error;
199 }
200
201 retval:
202 KTR_STOP4(KTR_SYSC, "syscall", syscallname(p, sa->code),
203 (uintptr_t)td, "pid:%d", td->td_proc->p_pid, "error:%d", error,
204 "retval0:%#lx", td->td_retval[0], "retval1:%#lx",
205 td->td_retval[1]);
206 if (__predict_false(traced)) {
207 PROC_LOCK(p);
208 td->td_dbgflags &= ~(TDB_SCE | TDB_BOUNDARY);
209 PROC_UNLOCK(p);
210 }
211 (p->p_sysent->sv_set_syscall_retval)(td, error);
212 if (error != 0 && (td->td_pflags2 & TDP2_UEXTERR) != 0)
213 exterr_copyout(td);
214 }
215
216 static inline void
syscallret(struct thread * td)217 syscallret(struct thread *td)
218 {
219 struct proc *p;
220 struct syscall_args *sa;
221 ksiginfo_t ksi;
222 int traced;
223
224 KASSERT(td->td_errno != ERELOOKUP,
225 ("ERELOOKUP not consumed syscall %d", td->td_sa.code));
226
227 p = td->td_proc;
228 sa = &td->td_sa;
229 if (__predict_false(td->td_errno == ENOTCAPABLE ||
230 td->td_errno == ECAPMODE)) {
231 if ((trap_enotcap ||
232 (p->p_flag2 & P2_TRAPCAP) != 0) && IN_CAPABILITY_MODE(td)) {
233 ksiginfo_init_trap(&ksi);
234 ksi.ksi_signo = SIGTRAP;
235 ksi.ksi_errno = td->td_errno;
236 ksi.ksi_code = TRAP_CAP;
237 ksi.ksi_info.si_syscall = sa->original_code;
238 trapsignal(td, &ksi);
239 }
240 }
241
242 /*
243 * Handle reschedule and other end-of-syscall issues
244 */
245 userret(td, td->td_frame);
246
247 #ifdef KTRACE
248 if (KTRPOINT(td, KTR_SYSRET)) {
249 ktrsysret(sa->code, td->td_errno, td->td_retval[0]);
250 }
251 #endif
252
253 traced = 0;
254 if (__predict_false(p->p_flag & P_TRACED)) {
255 traced = 1;
256 PROC_LOCK(p);
257 td->td_dbgflags |= TDB_SCX;
258 PROC_UNLOCK(p);
259 }
260 if (__predict_false(traced ||
261 (td->td_dbgflags & (TDB_EXEC | TDB_FORK)) != 0)) {
262 PROC_LOCK(p);
263 /*
264 * Linux debuggers expect an additional stop for exec,
265 * between the usual syscall entry and exit. Raise
266 * the exec event now and then clear TDB_EXEC so that
267 * the next stop is reported as a syscall exit by
268 * linux_ptrace_status().
269 *
270 * We are accessing p->p_pptr without any additional
271 * locks here: it cannot change while p is kept locked;
272 * while the debugger could in theory change its ABI
273 * while tracing another process, the outcome of such
274 * a race wouln't be deterministic anyway.
275 */
276 if (traced && (td->td_dbgflags & TDB_EXEC) != 0 &&
277 SV_PROC_ABI(p->p_pptr) == SV_ABI_LINUX) {
278 ptracestop(td, SIGTRAP, NULL);
279 td->td_dbgflags &= ~TDB_EXEC;
280 }
281 /*
282 * If tracing the execed process, trap to the debugger
283 * so that breakpoints can be set before the program
284 * executes. If debugger requested tracing of syscall
285 * returns, do it now too.
286 */
287 if (traced &&
288 ((td->td_dbgflags & (TDB_FORK | TDB_EXEC)) != 0 ||
289 (p->p_ptevents & PTRACE_SCX) != 0)) {
290 MPASS((td->td_dbgflags & TDB_BOUNDARY) == 0);
291 td->td_dbgflags |= TDB_BOUNDARY;
292 ptracestop(td, SIGTRAP, NULL);
293 }
294 td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK |
295 TDB_BOUNDARY);
296 PROC_UNLOCK(p);
297 }
298 }
299