Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_syscall.c
Version:
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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 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 td->td_errno = error; 90 goto retval; 91 } 92 93 STOPEVENT(p, S_SCE, sa->narg); 94 if ((p->p_flag & P_TRACED) != 0) { 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 #ifdef KTRACE 107 if (KTRPOINT(td, KTR_SYSCALL)) 108 ktrsyscall(sa->code, sa->narg, sa->args); 109 #endif 110 if (error != 0) { 111 td->td_errno = error; 112 goto retval; 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 (IN_CAPABILITY_MODE(td) && 122 !(sa->callp->sy_flags & SYF_CAPENABLED)) { 123 td->td_errno = error = ECAPMODE; 124 goto retval; 125 } 126 #endif 127 128 error = syscall_thread_enter(td, sa->callp); 129 if (error != 0) { 130 td->td_errno = error; 131 goto retval; 132 } 133 134 #ifdef KDTRACE_HOOKS 135 /* Give the syscall:::entry DTrace probe a chance to fire. */ 136 if (__predict_false(systrace_enabled && sa->callp->sy_entry != 0)) 137 (*systrace_probe_func)(sa, SYSTRACE_ENTRY, 0); 138 #endif 139 140 /* Let system calls set td_errno directly. */ 141 td->td_pflags &= ~TDP_NERRNO; 142 143 AUDIT_SYSCALL_ENTER(sa->code, td); 144 error = (sa->callp->sy_call)(td, sa->args); 145 146 /* 147 * Note that some syscall implementations (e.g., sys_execve) 148 * will commit the audit record just before their final return. 149 * These were done under the assumption that nothing of interest 150 * would happen between their return and here, where we would 151 * normally commit the audit record. These assumptions will 152 * need to be revisited should any substantial logic be added 153 * above. 154 */ 155 AUDIT_SYSCALL_EXIT(error, td); 156 157 /* Save the latest error return value. */ 158 if ((td->td_pflags & TDP_NERRNO) == 0) 159 td->td_errno = error; 160 161 #ifdef KDTRACE_HOOKS 162 /* Give the syscall:::return DTrace probe a chance to fire. */ 163 if (__predict_false(systrace_enabled && sa->callp->sy_return != 0)) 164 (*systrace_probe_func)(sa, SYSTRACE_RETURN, 165 error ? -1 : td->td_retval[0]); 166 #endif 167 syscall_thread_exit(td, sa->callp); 168 169 retval: 170 KTR_STOP4(KTR_SYSC, "syscall", syscallname(p, sa->code), 171 (uintptr_t)td, "pid:%d", td->td_proc->p_pid, "error:%d", error, 172 "retval0:%#lx", td->td_retval[0], "retval1:%#lx", 173 td->td_retval[1]); 174 if (traced) { 175 PROC_LOCK(p); 176 td->td_dbgflags &= ~TDB_SCE; 177 PROC_UNLOCK(p); 178 } 179 (p->p_sysent->sv_set_syscall_retval)(td, error); 180 } 181 182 static inline void 183 syscallret(struct thread *td) 184 { 185 struct proc *p, *p2; 186 struct syscall_args *sa; 187 ksiginfo_t ksi; 188 int traced; 189 190 KASSERT((td->td_pflags & TDP_FORKING) == 0, 191 ("fork() did not clear TDP_FORKING upon completion")); 192 193 p = td->td_proc; 194 sa = &td->td_sa; 195 if ((trap_enotcap || (p->p_flag2 & P2_TRAPCAP) != 0) && 196 IN_CAPABILITY_MODE(td)) { 197 if (td->td_errno == ENOTCAPABLE || td->td_errno == ECAPMODE) { 198 ksiginfo_init_trap(&ksi); 199 ksi.ksi_signo = SIGTRAP; 200 ksi.ksi_errno = td->td_errno; 201 ksi.ksi_code = TRAP_CAP; 202 trapsignal(td, &ksi); 203 } 204 } 205 206 /* 207 * Handle reschedule and other end-of-syscall issues 208 */ 209 userret(td, td->td_frame); 210 211 #ifdef KTRACE 212 if (KTRPOINT(td, KTR_SYSRET)) { 213 ktrsysret(sa->code, td->td_errno, td->td_retval[0]); 214 } 215 #endif 216 217 if (p->p_flag & P_TRACED) { 218 traced = 1; 219 PROC_LOCK(p); 220 td->td_dbgflags |= TDB_SCX; 221 PROC_UNLOCK(p); 222 } else 223 traced = 0; 224 /* 225 * This works because errno is findable through the 226 * register set. If we ever support an emulation where this 227 * is not the case, this code will need to be revisited. 228 */ 229 STOPEVENT(p, S_SCX, sa->code); 230 if (traced || (td->td_dbgflags & (TDB_EXEC | TDB_FORK)) != 0) { 231 PROC_LOCK(p); 232 /* 233 * If tracing the execed process, trap to the debugger 234 * so that breakpoints can be set before the program 235 * executes. If debugger requested tracing of syscall 236 * returns, do it now too. 237 */ 238 if (traced && 239 ((td->td_dbgflags & (TDB_FORK | TDB_EXEC)) != 0 || 240 (p->p_ptevents & PTRACE_SCX) != 0)) 241 ptracestop(td, SIGTRAP, NULL); 242 td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK); 243 PROC_UNLOCK(p); 244 } 245 246 if (td->td_pflags & TDP_RFPPWAIT) { 247 /* 248 * Preserve synchronization semantics of vfork. If 249 * waiting for child to exec or exit, fork set 250 * P_PPWAIT on child, and there we sleep on our proc 251 * (in case of exit). 252 * 253 * Do it after the ptracestop() above is finished, to 254 * not block our debugger until child execs or exits 255 * to finish vfork wait. 256 */ 257 td->td_pflags &= ~TDP_RFPPWAIT; 258 p2 = td->td_rfppwait_p; 259 again: 260 PROC_LOCK(p2); 261 while (p2->p_flag & P_PPWAIT) { 262 PROC_LOCK(p); 263 if (thread_suspend_check_needed()) { 264 PROC_UNLOCK(p2); 265 thread_suspend_check(0); 266 PROC_UNLOCK(p); 267 goto again; 268 } else { 269 PROC_UNLOCK(p); 270 } 271 cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz); 272 } 273 PROC_UNLOCK(p2); 274 275 if (td->td_dbgflags & TDB_VFORK) { 276 PROC_LOCK(p); 277 if (p->p_ptevents & PTRACE_VFORK) 278 ptracestop(td, SIGTRAP, NULL); 279 td->td_dbgflags &= ~TDB_VFORK; 280 PROC_UNLOCK(p); 281 } 282 } 283 }
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