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 != atomic_load_int(&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 MPASS((td->td_dbgflags & TDB_BOUNDARY) == 0); 77 td->td_dbgflags &= ~TDB_USERWR; 78 if (traced) 79 td->td_dbgflags |= TDB_SCE; 80 PROC_UNLOCK(p); 81 } 82 error = (p->p_sysent->sv_fetch_syscall_args)(td); 83 se = sa->callp; 84 #ifdef KTRACE 85 if (KTRPOINT(td, KTR_SYSCALL)) 86 ktrsyscall(sa->code, se->sy_narg, sa->args); 87 #endif 88 KTR_START4(KTR_SYSC, "syscall", syscallname(p, sa->code), 89 (uintptr_t)td, "pid:%d", td->td_proc->p_pid, "arg0:%p", sa->args[0], 90 "arg1:%p", sa->args[1], "arg2:%p", sa->args[2]); 91 92 if (__predict_false(error != 0)) { 93 td->td_errno = error; 94 goto retval; 95 } 96 97 if (__predict_false(traced)) { 98 PROC_LOCK(p); 99 if (p->p_ptevents & PTRACE_SCE) 100 ptracestop((td), SIGTRAP, NULL); 101 PROC_UNLOCK(p); 102 103 if ((td->td_dbgflags & TDB_USERWR) != 0) { 104 /* 105 * Reread syscall number and arguments if debugger 106 * modified registers or memory. 107 */ 108 error = (p->p_sysent->sv_fetch_syscall_args)(td); 109 se = sa->callp; 110 #ifdef KTRACE 111 if (KTRPOINT(td, KTR_SYSCALL)) 112 ktrsyscall(sa->code, se->sy_narg, sa->args); 113 #endif 114 if (error != 0) { 115 td->td_errno = error; 116 goto retval; 117 } 118 } 119 } 120 121 #ifdef CAPABILITY_MODE 122 /* 123 * In capability mode, we only allow access to system calls 124 * flagged with SYF_CAPENABLED. 125 */ 126 if (__predict_false(IN_CAPABILITY_MODE(td) && 127 (se->sy_flags & SYF_CAPENABLED) == 0)) { 128 td->td_errno = error = ECAPMODE; 129 goto retval; 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(SYSTRACE_ENABLED() || 147 AUDIT_SYSCALL_ENTER(sa->code, td) || 148 !sy_thr_static)) { 149 if (!sy_thr_static) { 150 error = syscall_thread_enter(td, se); 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 error = (se->sy_call)(td, sa->args); 163 /* Save the latest error return value. */ 164 if (__predict_false((td->td_pflags & TDP_NERRNO) != 0)) 165 td->td_pflags &= ~TDP_NERRNO; 166 else 167 td->td_errno = error; 168 169 /* 170 * Note that some syscall implementations (e.g., sys_execve) 171 * will commit the audit record just before their final return. 172 * These were done under the assumption that nothing of interest 173 * would happen between their return and here, where we would 174 * normally commit the audit record. These assumptions will 175 * need to be revisited should any substantial logic be added 176 * above. 177 */ 178 AUDIT_SYSCALL_EXIT(error, td); 179 180 #ifdef KDTRACE_HOOKS 181 /* Give the syscall:::return DTrace probe a chance to fire. */ 182 if (__predict_false(se->sy_return != 0)) 183 (*systrace_probe_func)(sa, SYSTRACE_RETURN, 184 error ? -1 : td->td_retval[0]); 185 #endif 186 187 if (!sy_thr_static) 188 syscall_thread_exit(td, se); 189 } else { 190 error = (se->sy_call)(td, sa->args); 191 /* Save the latest error return value. */ 192 if (__predict_false((td->td_pflags & TDP_NERRNO) != 0)) 193 td->td_pflags &= ~TDP_NERRNO; 194 else 195 td->td_errno = error; 196 } 197 198 retval: 199 KTR_STOP4(KTR_SYSC, "syscall", syscallname(p, sa->code), 200 (uintptr_t)td, "pid:%d", td->td_proc->p_pid, "error:%d", error, 201 "retval0:%#lx", td->td_retval[0], "retval1:%#lx", 202 td->td_retval[1]); 203 if (__predict_false(traced)) { 204 PROC_LOCK(p); 205 td->td_dbgflags &= ~(TDB_SCE | TDB_BOUNDARY); 206 PROC_UNLOCK(p); 207 } 208 (p->p_sysent->sv_set_syscall_retval)(td, error); 209 } 210 211 static inline void 212 syscallret(struct thread *td) 213 { 214 struct proc *p; 215 struct syscall_args *sa; 216 ksiginfo_t ksi; 217 int traced; 218 219 KASSERT(td->td_errno != ERELOOKUP, 220 ("ERELOOKUP not consumed syscall %d", td->td_sa.code)); 221 222 p = td->td_proc; 223 sa = &td->td_sa; 224 if (__predict_false(td->td_errno == ENOTCAPABLE || 225 td->td_errno == ECAPMODE)) { 226 if ((trap_enotcap || 227 (p->p_flag2 & P2_TRAPCAP) != 0) && IN_CAPABILITY_MODE(td)) { 228 ksiginfo_init_trap(&ksi); 229 ksi.ksi_signo = SIGTRAP; 230 ksi.ksi_errno = td->td_errno; 231 ksi.ksi_code = TRAP_CAP; 232 ksi.ksi_info.si_syscall = sa->original_code; 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 * Linux debuggers expect an additional stop for exec, 260 * between the usual syscall entry and exit. Raise 261 * the exec event now and then clear TDB_EXEC so that 262 * the next stop is reported as a syscall exit by 263 * linux_ptrace_status(). 264 * 265 * We are accessing p->p_pptr without any additional 266 * locks here: it cannot change while p is kept locked; 267 * while the debugger could in theory change its ABI 268 * while tracing another process, the outcome of such 269 * a race wouln't be deterministic anyway. 270 */ 271 if (traced && (td->td_dbgflags & TDB_EXEC) != 0 && 272 SV_PROC_ABI(p->p_pptr) == SV_ABI_LINUX) { 273 ptracestop(td, SIGTRAP, NULL); 274 td->td_dbgflags &= ~TDB_EXEC; 275 } 276 /* 277 * If tracing the execed process, trap to the debugger 278 * so that breakpoints can be set before the program 279 * executes. If debugger requested tracing of syscall 280 * returns, do it now too. 281 */ 282 if (traced && 283 ((td->td_dbgflags & (TDB_FORK | TDB_EXEC)) != 0 || 284 (p->p_ptevents & PTRACE_SCX) != 0)) { 285 MPASS((td->td_dbgflags & TDB_BOUNDARY) == 0); 286 td->td_dbgflags |= TDB_BOUNDARY; 287 ptracestop(td, SIGTRAP, NULL); 288 } 289 td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK | 290 TDB_BOUNDARY); 291 PROC_UNLOCK(p); 292 } 293 } 294