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 error = (p->p_sysent->sv_fetch_syscall_args)(td);
78 se = sa->callp;
79 #ifdef KTRACE
80 if (KTRPOINT(td, KTR_SYSCALL))
81 ktrsyscall(sa->code, se->sy_narg, sa->args);
82 #endif
83 KTR_START4(KTR_SYSC, "syscall", syscallname(p, sa->code),
84 (uintptr_t)td, "pid:%d", td->td_proc->p_pid, "arg0:%p", sa->args[0],
85 "arg1:%p", sa->args[1], "arg2:%p", sa->args[2]);
86
87 if (__predict_false(error != 0)) {
88 td->td_errno = error;
89 goto retval;
90 }
91
92 if (__predict_false(traced)) {
93 PROC_LOCK(p);
94 if (p->p_ptevents & PTRACE_SCE)
95 ptracestop((td), SIGTRAP, NULL);
96 PROC_UNLOCK(p);
97
98 if ((td->td_dbgflags & TDB_USERWR) != 0) {
99 /*
100 * Reread syscall number and arguments if debugger
101 * modified registers or memory.
102 */
103 error = (p->p_sysent->sv_fetch_syscall_args)(td);
104 se = sa->callp;
105 #ifdef KTRACE
106 if (KTRPOINT(td, KTR_SYSCALL))
107 ktrsyscall(sa->code, se->sy_narg, sa->args);
108 #endif
109 if (error != 0) {
110 td->td_errno = error;
111 goto retval;
112 }
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 ((se->sy_flags & SYF_CAPENABLED) == 0) {
122 if (CAP_TRACING(td))
123 ktrcapfail(CAPFAIL_SYSCALL, NULL);
124 if (IN_CAPABILITY_MODE(td)) {
125 td->td_errno = error = ECAPMODE;
126 goto retval;
127 }
128 }
129 #endif
130
131 /*
132 * Fetch fast sigblock value at the time of syscall entry to
133 * handle sleepqueue primitives which might call cursig().
134 */
135 if (__predict_false(sigfastblock_fetch_always))
136 (void)sigfastblock_fetch(td);
137
138 /* Let system calls set td_errno directly. */
139 KASSERT((td->td_pflags & TDP_NERRNO) == 0,
140 ("%s: TDP_NERRNO set", __func__));
141
142 sy_thr_static = (se->sy_thrcnt & SY_THR_STATIC) != 0;
143
144 if (__predict_false(AUDIT_SYSCALL_ENABLED() ||
145 SYSTRACE_ENABLED() || !sy_thr_static)) {
146 if (!sy_thr_static) {
147 error = syscall_thread_enter(td, &se);
148 sy_thr_static = (se->sy_thrcnt & SY_THR_STATIC) != 0;
149 if (error != 0) {
150 td->td_errno = error;
151 goto retval;
152 }
153 }
154
155 #ifdef KDTRACE_HOOKS
156 /* Give the syscall:::entry DTrace probe a chance to fire. */
157 if (__predict_false(se->sy_entry != 0))
158 (*systrace_probe_func)(sa, SYSTRACE_ENTRY, 0);
159 #endif
160
161 AUDIT_SYSCALL_ENTER(sa->code, td);
162
163 error = (se->sy_call)(td, sa->args);
164 /* Save the latest error return value. */
165 if (__predict_false((td->td_pflags & TDP_NERRNO) != 0))
166 td->td_pflags &= ~TDP_NERRNO;
167 else
168 td->td_errno = error;
169
170 /*
171 * Note that some syscall implementations (e.g., sys_execve)
172 * will commit the audit record just before their final return.
173 * These were done under the assumption that nothing of interest
174 * would happen between their return and here, where we would
175 * normally commit the audit record. These assumptions will
176 * need to be revisited should any substantial logic be added
177 * above.
178 */
179 AUDIT_SYSCALL_EXIT(error, td);
180
181 #ifdef KDTRACE_HOOKS
182 /* Give the syscall:::return DTrace probe a chance to fire. */
183 if (__predict_false(se->sy_return != 0))
184 (*systrace_probe_func)(sa, SYSTRACE_RETURN,
185 error ? -1 : td->td_retval[0]);
186 #endif
187
188 if (!sy_thr_static)
189 syscall_thread_exit(td, se);
190 } else {
191 error = (se->sy_call)(td, sa->args);
192 /* Save the latest error return value. */
193 if (__predict_false((td->td_pflags & TDP_NERRNO) != 0))
194 td->td_pflags &= ~TDP_NERRNO;
195 else
196 td->td_errno = error;
197 }
198
199 retval:
200 KTR_STOP4(KTR_SYSC, "syscall", syscallname(p, sa->code),
201 (uintptr_t)td, "pid:%d", td->td_proc->p_pid, "error:%d", error,
202 "retval0:%#lx", td->td_retval[0], "retval1:%#lx",
203 td->td_retval[1]);
204 if (__predict_false(traced)) {
205 PROC_LOCK(p);
206 td->td_dbgflags &= ~(TDB_SCE | TDB_BOUNDARY);
207 PROC_UNLOCK(p);
208 }
209 (p->p_sysent->sv_set_syscall_retval)(td, error);
210 }
211
212 static inline void
syscallret(struct thread * td)213 syscallret(struct thread *td)
214 {
215 struct proc *p;
216 struct syscall_args *sa;
217 ksiginfo_t ksi;
218 int traced;
219
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 ksi.ksi_info.si_syscall = sa->original_code;
234 trapsignal(td, &ksi);
235 }
236 }
237
238 /*
239 * Handle reschedule and other end-of-syscall issues
240 */
241 userret(td, td->td_frame);
242
243 #ifdef KTRACE
244 if (KTRPOINT(td, KTR_SYSRET)) {
245 ktrsysret(sa->code, td->td_errno, td->td_retval[0]);
246 }
247 #endif
248
249 traced = 0;
250 if (__predict_false(p->p_flag & P_TRACED)) {
251 traced = 1;
252 PROC_LOCK(p);
253 td->td_dbgflags |= TDB_SCX;
254 PROC_UNLOCK(p);
255 }
256 if (__predict_false(traced ||
257 (td->td_dbgflags & (TDB_EXEC | TDB_FORK)) != 0)) {
258 PROC_LOCK(p);
259 /*
260 * Linux debuggers expect an additional stop for exec,
261 * between the usual syscall entry and exit. Raise
262 * the exec event now and then clear TDB_EXEC so that
263 * the next stop is reported as a syscall exit by
264 * linux_ptrace_status().
265 *
266 * We are accessing p->p_pptr without any additional
267 * locks here: it cannot change while p is kept locked;
268 * while the debugger could in theory change its ABI
269 * while tracing another process, the outcome of such
270 * a race wouln't be deterministic anyway.
271 */
272 if (traced && (td->td_dbgflags & TDB_EXEC) != 0 &&
273 SV_PROC_ABI(p->p_pptr) == SV_ABI_LINUX) {
274 ptracestop(td, SIGTRAP, NULL);
275 td->td_dbgflags &= ~TDB_EXEC;
276 }
277 /*
278 * If tracing the execed process, trap to the debugger
279 * so that breakpoints can be set before the program
280 * executes. If debugger requested tracing of syscall
281 * returns, do it now too.
282 */
283 if (traced &&
284 ((td->td_dbgflags & (TDB_FORK | TDB_EXEC)) != 0 ||
285 (p->p_ptevents & PTRACE_SCX) != 0)) {
286 MPASS((td->td_dbgflags & TDB_BOUNDARY) == 0);
287 td->td_dbgflags |= TDB_BOUNDARY;
288 ptracestop(td, SIGTRAP, NULL);
289 }
290 td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK |
291 TDB_BOUNDARY);
292 PROC_UNLOCK(p);
293 }
294 }
295