subr_syscall.c revision 234172
1/*- 2 * Copyright (C) 1994, David Greenman 3 * Copyright (c) 1990, 1993 4 * The Regents of the University of California. All rights reserved. 5 * Copyright (C) 2010 Konstantin Belousov <kib@freebsd.org> 6 * 7 * This code is derived from software contributed to Berkeley by 8 * the University of Utah, and William Jolitz. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * from: @(#)trap.c 7.4 (Berkeley) 5/13/91 39 */ 40 41#include "opt_capsicum.h" 42#include "opt_ktrace.h" 43#include "opt_kdtrace.h" 44 45__FBSDID("$FreeBSD: head/sys/kern/subr_syscall.c 234172 2012-04-12 10:48:43Z kib $"); 46 47#include <sys/capability.h> 48#include <sys/ktr.h> 49#ifdef KTRACE 50#include <sys/uio.h> 51#include <sys/ktrace.h> 52#endif 53#include <security/audit/audit.h> 54 55static inline int 56syscallenter(struct thread *td, struct syscall_args *sa) 57{ 58 struct proc *p; 59 int error, traced; 60 61 PCPU_INC(cnt.v_syscall); 62 p = td->td_proc; 63 64 td->td_pticks = 0; 65 if (td->td_ucred != p->p_ucred) 66 cred_update_thread(td); 67 if (p->p_flag & P_TRACED) { 68 traced = 1; 69 PROC_LOCK(p); 70 td->td_dbgflags &= ~TDB_USERWR; 71 td->td_dbgflags |= TDB_SCE; 72 PROC_UNLOCK(p); 73 } else 74 traced = 0; 75 error = (p->p_sysent->sv_fetch_syscall_args)(td, sa); 76#ifdef KTRACE 77 if (KTRPOINT(td, KTR_SYSCALL)) 78 ktrsyscall(sa->code, sa->narg, sa->args); 79#endif 80 81 CTR6(KTR_SYSC, 82"syscall: td=%p pid %d %s (%#lx, %#lx, %#lx)", 83 td, td->td_proc->p_pid, syscallname(p, sa->code), 84 sa->args[0], sa->args[1], sa->args[2]); 85 86 if (error == 0) { 87 STOPEVENT(p, S_SCE, sa->narg); 88 if (p->p_flag & P_TRACED && p->p_stops & S_PT_SCE) { 89 PROC_LOCK(p); 90 ptracestop((td), SIGTRAP); 91 PROC_UNLOCK(p); 92 } 93 if (td->td_dbgflags & TDB_USERWR) { 94 /* 95 * Reread syscall number and arguments if 96 * debugger modified registers or memory. 97 */ 98 error = (p->p_sysent->sv_fetch_syscall_args)(td, sa); 99#ifdef KTRACE 100 if (KTRPOINT(td, KTR_SYSCALL)) 101 ktrsyscall(sa->code, sa->narg, sa->args); 102#endif 103 if (error != 0) 104 goto retval; 105 } 106 107#ifdef CAPABILITY_MODE 108 /* 109 * In capability mode, we only allow access to system calls 110 * flagged with SYF_CAPENABLED. 111 */ 112 if (IN_CAPABILITY_MODE(td) && 113 !(sa->callp->sy_flags & SYF_CAPENABLED)) { 114 error = ECAPMODE; 115 goto retval; 116 } 117#endif 118 119 error = syscall_thread_enter(td, sa->callp); 120 if (error != 0) 121 goto retval; 122 123#ifdef KDTRACE_HOOKS 124 /* 125 * If the systrace module has registered it's probe 126 * callback and if there is a probe active for the 127 * syscall 'entry', process the probe. 128 */ 129 if (systrace_probe_func != NULL && sa->callp->sy_entry != 0) 130 (*systrace_probe_func)(sa->callp->sy_entry, sa->code, 131 sa->callp, sa->args, 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 /* 144 * If the systrace module has registered it's probe 145 * callback and if there is a probe active for the 146 * syscall 'return', process the probe. 147 */ 148 if (systrace_probe_func != NULL && sa->callp->sy_return != 0) 149 (*systrace_probe_func)(sa->callp->sy_return, sa->code, 150 sa->callp, NULL, (error) ? -1 : td->td_retval[0]); 151#endif 152 syscall_thread_exit(td, sa->callp); 153 CTR4(KTR_SYSC, "syscall: p=%p error=%d return %#lx %#lx", 154 p, error, td->td_retval[0], td->td_retval[1]); 155 } 156 retval: 157 if (traced) { 158 PROC_LOCK(p); 159 td->td_dbgflags &= ~TDB_SCE; 160 PROC_UNLOCK(p); 161 } 162 (p->p_sysent->sv_set_syscall_retval)(td, error); 163 return (error); 164} 165 166static inline void 167syscallret(struct thread *td, int error, struct syscall_args *sa __unused) 168{ 169 struct proc *p, *p2; 170 int traced; 171 172 p = td->td_proc; 173 174 /* 175 * Check for misbehavior. 176 */ 177 WITNESS_WARN(WARN_PANIC, NULL, "System call %s returning", 178 syscallname(p, sa->code)); 179 KASSERT(td->td_critnest == 0, 180 ("System call %s returning in a critical section", 181 syscallname(p, sa->code))); 182 KASSERT(td->td_locks == 0, 183 ("System call %s returning with %d locks held", 184 syscallname(p, sa->code), td->td_locks)); 185 186 /* 187 * Handle reschedule and other end-of-syscall issues 188 */ 189 userret(td, td->td_frame); 190 191 CTR4(KTR_SYSC, "syscall %s exit thread %p pid %d proc %s", 192 syscallname(p, sa->code), td, td->td_proc->p_pid, td->td_name); 193 194#ifdef KTRACE 195 if (KTRPOINT(td, KTR_SYSRET)) { 196 ktrsysret(sa->code, (td->td_pflags & TDP_NERRNO) == 0 ? 197 error : td->td_errno, td->td_retval[0]); 198 } 199#endif 200 td->td_pflags &= ~TDP_NERRNO; 201 202 if (p->p_flag & P_TRACED) { 203 traced = 1; 204 PROC_LOCK(p); 205 td->td_dbgflags |= TDB_SCX; 206 PROC_UNLOCK(p); 207 } else 208 traced = 0; 209 /* 210 * This works because errno is findable through the 211 * register set. If we ever support an emulation where this 212 * is not the case, this code will need to be revisited. 213 */ 214 STOPEVENT(p, S_SCX, sa->code); 215 if (traced || (td->td_dbgflags & (TDB_EXEC | TDB_FORK)) != 0) { 216 PROC_LOCK(p); 217 /* 218 * If tracing the execed process, trap to the debugger 219 * so that breakpoints can be set before the program 220 * executes. If debugger requested tracing of syscall 221 * returns, do it now too. 222 */ 223 if (traced && 224 ((td->td_dbgflags & (TDB_FORK | TDB_EXEC)) != 0 || 225 (p->p_stops & S_PT_SCX) != 0)) 226 ptracestop(td, SIGTRAP); 227 td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK); 228 PROC_UNLOCK(p); 229 } 230 231 if (td->td_pflags & TDP_RFPPWAIT) { 232 /* 233 * Preserve synchronization semantics of vfork. If 234 * waiting for child to exec or exit, fork set 235 * P_PPWAIT on child, and there we sleep on our proc 236 * (in case of exit). 237 * 238 * Do it after the ptracestop() above is finished, to 239 * not block our debugger until child execs or exits 240 * to finish vfork wait. 241 */ 242 td->td_pflags &= ~TDP_RFPPWAIT; 243 p2 = td->td_rfppwait_p; 244 PROC_LOCK(p2); 245 while (p2->p_flag & P_PPWAIT) 246 cv_wait(&p2->p_pwait, &p2->p_mtx); 247 PROC_UNLOCK(p2); 248 } 249} 250