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: releng/12.0/sys/kern/subr_syscall.c 333064 2018-04-27 15:16:34Z mjg $");
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 int
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
90 STOPEVENT(p, S_SCE, sa->narg);
91 if (p->p_flag & P_TRACED) {
92 PROC_LOCK(p);
93 if (p->p_ptevents & PTRACE_SCE)
94 ptracestop((td), SIGTRAP, NULL);
95 PROC_UNLOCK(p);
96 }
97 if (td->td_dbgflags & TDB_USERWR) {
98 /*
99 * Reread syscall number and arguments if
100 * debugger modified registers or memory.
101 */
102 error = (p->p_sysent->sv_fetch_syscall_args)(td);
103 #ifdef KTRACE
104 if (KTRPOINT(td, KTR_SYSCALL))
105 ktrsyscall(sa->code, sa->narg, sa->args);
106 #endif
107 if (error != 0)
108 goto retval;
109 }
110
111 #ifdef CAPABILITY_MODE
112 /*
113 * In capability mode, we only allow access to system calls
114 * flagged with SYF_CAPENABLED.
115 */
116 if (IN_CAPABILITY_MODE(td) &&
117 !(sa->callp->sy_flags & SYF_CAPENABLED)) {
118 error = ECAPMODE;
119 goto retval;
120 }
121 #endif
122
123 error = syscall_thread_enter(td, sa->callp);
124 if (error != 0)
125 goto retval;
126
127 #ifdef KDTRACE_HOOKS
128 /* Give the syscall:::entry DTrace probe a chance to fire. */
129 if (__predict_false(systrace_enabled &&
130 sa->callp->sy_entry != 0))
131 (*systrace_probe_func)(sa, SYSTRACE_ENTRY, 0);
132 #endif
133
134 AUDIT_SYSCALL_ENTER(sa->code, td);
135 error = (sa->callp->sy_call)(td, sa->args);
136 AUDIT_SYSCALL_EXIT(error, td);
137
138 /* Save the latest error return value. */
139 if ((td->td_pflags & TDP_NERRNO) == 0)
140 td->td_errno = error;
141
142 #ifdef KDTRACE_HOOKS
143 /* Give the syscall:::return DTrace probe a chance to fire. */
144 if (__predict_false(systrace_enabled &&
145 sa->callp->sy_return != 0))
146 (*systrace_probe_func)(sa, SYSTRACE_RETURN,
147 error ? -1 : td->td_retval[0]);
148 #endif
149 syscall_thread_exit(td, sa->callp);
150 }
151 retval:
152 KTR_STOP4(KTR_SYSC, "syscall", syscallname(p, sa->code),
153 (uintptr_t)td, "pid:%d", td->td_proc->p_pid, "error:%d", error,
154 "retval0:%#lx", td->td_retval[0], "retval1:%#lx",
155 td->td_retval[1]);
156 if (traced) {
157 PROC_LOCK(p);
158 td->td_dbgflags &= ~TDB_SCE;
159 PROC_UNLOCK(p);
160 }
161 (p->p_sysent->sv_set_syscall_retval)(td, error);
162 return (error);
163 }
164
165 static inline void
166 syscallret(struct thread *td, int error)
167 {
168 struct proc *p, *p2;
169 struct syscall_args *sa;
170 ksiginfo_t ksi;
171 int traced, error1;
172
173 KASSERT((td->td_pflags & TDP_FORKING) == 0,
174 ("fork() did not clear TDP_FORKING upon completion"));
175
176 p = td->td_proc;
177 sa = &td->td_sa;
178 if ((trap_enotcap || (p->p_flag2 & P2_TRAPCAP) != 0) &&
179 IN_CAPABILITY_MODE(td)) {
180 error1 = (td->td_pflags & TDP_NERRNO) == 0 ? error :
181 td->td_errno;
182 if (error1 == ENOTCAPABLE || error1 == ECAPMODE) {
183 ksiginfo_init_trap(&ksi);
184 ksi.ksi_signo = SIGTRAP;
185 ksi.ksi_errno = error1;
186 ksi.ksi_code = TRAP_CAP;
187 trapsignal(td, &ksi);
188 }
189 }
190
191 /*
192 * Handle reschedule and other end-of-syscall issues
193 */
194 userret(td, td->td_frame);
195
196 #ifdef KTRACE
197 if (KTRPOINT(td, KTR_SYSRET)) {
198 ktrsysret(sa->code, (td->td_pflags & TDP_NERRNO) == 0 ?
199 error : td->td_errno, td->td_retval[0]);
200 }
201 #endif
202 td->td_pflags &= ~TDP_NERRNO;
203
204 if (p->p_flag & P_TRACED) {
205 traced = 1;
206 PROC_LOCK(p);
207 td->td_dbgflags |= TDB_SCX;
208 PROC_UNLOCK(p);
209 } else
210 traced = 0;
211 /*
212 * This works because errno is findable through the
213 * register set. If we ever support an emulation where this
214 * is not the case, this code will need to be revisited.
215 */
216 STOPEVENT(p, S_SCX, sa->code);
217 if (traced || (td->td_dbgflags & (TDB_EXEC | TDB_FORK)) != 0) {
218 PROC_LOCK(p);
219 /*
220 * If tracing the execed process, trap to the debugger
221 * so that breakpoints can be set before the program
222 * executes. If debugger requested tracing of syscall
223 * returns, do it now too.
224 */
225 if (traced &&
226 ((td->td_dbgflags & (TDB_FORK | TDB_EXEC)) != 0 ||
227 (p->p_ptevents & PTRACE_SCX) != 0))
228 ptracestop(td, SIGTRAP, NULL);
229 td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK);
230 PROC_UNLOCK(p);
231 }
232
233 if (td->td_pflags & TDP_RFPPWAIT) {
234 /*
235 * Preserve synchronization semantics of vfork. If
236 * waiting for child to exec or exit, fork set
237 * P_PPWAIT on child, and there we sleep on our proc
238 * (in case of exit).
239 *
240 * Do it after the ptracestop() above is finished, to
241 * not block our debugger until child execs or exits
242 * to finish vfork wait.
243 */
244 td->td_pflags &= ~TDP_RFPPWAIT;
245 p2 = td->td_rfppwait_p;
246 again:
247 PROC_LOCK(p2);
248 while (p2->p_flag & P_PPWAIT) {
249 PROC_LOCK(p);
250 if (thread_suspend_check_needed()) {
251 PROC_UNLOCK(p2);
252 thread_suspend_check(0);
253 PROC_UNLOCK(p);
254 goto again;
255 } else {
256 PROC_UNLOCK(p);
257 }
258 cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz);
259 }
260 PROC_UNLOCK(p2);
261
262 if (td->td_dbgflags & TDB_VFORK) {
263 PROC_LOCK(p);
264 if (p->p_ptevents & PTRACE_VFORK)
265 ptracestop(td, SIGTRAP, NULL);
266 td->td_dbgflags &= ~TDB_VFORK;
267 PROC_UNLOCK(p);
268 }
269 }
270 }
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