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