1 /*- 2 * Copyright (c) 1990, 1993 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (C) 1994, David Greenman 5 * Copyright (c) 2008-2018 The DragonFly Project. 6 * Copyright (c) 2008 Jordan Gordeev. 7 * 8 * This code is derived from software contributed to Berkeley by 9 * the University of Utah, and William Jolitz. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the University of 22 * California, Berkeley and its contributors. 23 * 4. Neither the name of the University nor the names of its contributors 24 * may be used to endorse or promote products derived from this software 25 * without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 28 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 29 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 30 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 31 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 32 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 33 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 35 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 36 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 37 * SUCH DAMAGE. 38 * 39 * from: @(#)trap.c 7.4 (Berkeley) 5/13/91 40 * $FreeBSD: src/sys/i386/i386/trap.c,v 1.147.2.11 2003/02/27 19:09:59 luoqi Exp $ 41 */ 42 43 /* 44 * x86_64 Trap and System call handling 45 */ 46 47 #include "use_isa.h" 48 49 #include "opt_ddb.h" 50 #include "opt_ktrace.h" 51 52 #include <machine/frame.h> 53 #include <sys/param.h> 54 #include <sys/systm.h> 55 #include <sys/kernel.h> 56 #include <sys/kerneldump.h> 57 #include <sys/proc.h> 58 #include <sys/pioctl.h> 59 #include <sys/types.h> 60 #include <sys/signal2.h> 61 #include <sys/syscall.h> 62 #include <sys/sysctl.h> 63 #include <sys/sysent.h> 64 #ifdef KTRACE 65 #include <sys/ktrace.h> 66 #endif 67 #include <sys/ktr.h> 68 #include <sys/sysmsg.h> 69 #include <sys/sysproto.h> 70 #include <sys/sysunion.h> 71 72 #include <vm/pmap.h> 73 #include <vm/vm.h> 74 #include <vm/vm_extern.h> 75 #include <vm/vm_kern.h> 76 #include <vm/vm_param.h> 77 #include <machine/cpu.h> 78 #include <machine/pcb.h> 79 #include <machine/smp.h> 80 #include <machine/thread.h> 81 #include <machine/clock.h> 82 #include <machine/vmparam.h> 83 #include <machine/md_var.h> 84 #include <machine_base/isa/isa_intr.h> 85 #include <machine_base/apic/lapic.h> 86 87 #include <ddb/ddb.h> 88 89 #include <sys/thread2.h> 90 #include <sys/spinlock2.h> 91 92 /* 93 * These %rip's are used to detect a historical CPU artifact on syscall or 94 * int $3 entry, if not shortcutted in exception.S via 95 * DIRECT_DISALLOW_SS_CPUBUG. 96 */ 97 extern void Xbpt(void); 98 extern void Xfast_syscall(void); 99 #define IDTVEC(vec) X##vec 100 101 extern void trap(struct trapframe *frame); 102 103 static int trap_pfault(struct trapframe *, int); 104 static void trap_fatal(struct trapframe *, vm_offset_t); 105 void dblfault_handler(struct trapframe *frame); 106 107 #define MAX_TRAP_MSG 30 108 static char *trap_msg[] = { 109 "", /* 0 unused */ 110 "privileged instruction fault", /* 1 T_PRIVINFLT */ 111 "", /* 2 unused */ 112 "breakpoint instruction fault", /* 3 T_BPTFLT */ 113 "", /* 4 unused */ 114 "", /* 5 unused */ 115 "arithmetic trap", /* 6 T_ARITHTRAP */ 116 "system forced exception", /* 7 T_ASTFLT */ 117 "", /* 8 unused */ 118 "general protection fault", /* 9 T_PROTFLT */ 119 "trace trap", /* 10 T_TRCTRAP */ 120 "", /* 11 unused */ 121 "page fault", /* 12 T_PAGEFLT */ 122 "", /* 13 unused */ 123 "alignment fault", /* 14 T_ALIGNFLT */ 124 "", /* 15 unused */ 125 "", /* 16 unused */ 126 "", /* 17 unused */ 127 "integer divide fault", /* 18 T_DIVIDE */ 128 "non-maskable interrupt trap", /* 19 T_NMI */ 129 "overflow trap", /* 20 T_OFLOW */ 130 "FPU bounds check fault", /* 21 T_BOUND */ 131 "FPU device not available", /* 22 T_DNA */ 132 "double fault", /* 23 T_DOUBLEFLT */ 133 "FPU operand fetch fault", /* 24 T_FPOPFLT */ 134 "invalid TSS fault", /* 25 T_TSSFLT */ 135 "segment not present fault", /* 26 T_SEGNPFLT */ 136 "stack fault", /* 27 T_STKFLT */ 137 "machine check trap", /* 28 T_MCHK */ 138 "SIMD floating-point exception", /* 29 T_XMMFLT */ 139 "reserved (unknown) fault", /* 30 T_RESERVED */ 140 }; 141 142 #ifdef DDB 143 static int ddb_on_nmi = 1; 144 SYSCTL_INT(_machdep, OID_AUTO, ddb_on_nmi, CTLFLAG_RW, 145 &ddb_on_nmi, 0, "Go to DDB on NMI"); 146 static int ddb_on_seg_fault = 0; 147 SYSCTL_INT(_machdep, OID_AUTO, ddb_on_seg_fault, CTLFLAG_RW, 148 &ddb_on_seg_fault, 0, "Go to DDB on user seg-fault"); 149 static int freeze_on_seg_fault = 0; 150 SYSCTL_INT(_machdep, OID_AUTO, freeze_on_seg_fault, CTLFLAG_RW, 151 &freeze_on_seg_fault, 0, "Go to DDB on user seg-fault"); 152 #endif 153 static int panic_on_nmi = 1; 154 SYSCTL_INT(_machdep, OID_AUTO, panic_on_nmi, CTLFLAG_RW, 155 &panic_on_nmi, 0, "Panic on NMI"); 156 static int fast_release; 157 SYSCTL_INT(_machdep, OID_AUTO, fast_release, CTLFLAG_RW, 158 &fast_release, 0, "Passive Release was optimal"); 159 static int slow_release; 160 SYSCTL_INT(_machdep, OID_AUTO, slow_release, CTLFLAG_RW, 161 &slow_release, 0, "Passive Release was nonoptimal"); 162 163 /* 164 * System call debugging records the worst-case system call 165 * overhead (inclusive of blocking), but may be inaccurate. 166 */ 167 /*#define SYSCALL_DEBUG*/ 168 #ifdef SYSCALL_DEBUG 169 uint64_t SysCallsWorstCase[SYS_MAXSYSCALL]; 170 #endif 171 172 /* 173 * Passively intercepts the thread switch function to increase 174 * the thread priority from a user priority to a kernel priority, reducing 175 * syscall and trap overhead for the case where no switch occurs. 176 * 177 * Synchronizes td_ucred with p_ucred. This is used by system calls, 178 * signal handling, faults, AST traps, and anything else that enters the 179 * kernel from userland and provides the kernel with a stable read-only 180 * copy of the process ucred. 181 * 182 * To avoid races with another thread updating p_ucred we obtain p_spin. 183 * The other thread doing the update will obtain both p_token and p_spin. 184 * In the case where the cached cred pointer matches, we will already have 185 * the ref and we don't have to do one blessed thing. 186 */ 187 static __inline void 188 userenter(struct thread *curtd, struct proc *curp) 189 { 190 struct ucred *ocred; 191 struct ucred *ncred; 192 193 curtd->td_release = lwkt_passive_release; 194 195 if (curtd->td_ucred != curp->p_ucred) { 196 spin_lock(&curp->p_spin); 197 ncred = crhold(curp->p_ucred); 198 spin_unlock(&curp->p_spin); 199 ocred = curtd->td_ucred; 200 curtd->td_ucred = ncred; 201 if (ocred) 202 crfree(ocred); 203 } 204 205 #ifdef DDB 206 /* 207 * Debugging, remove top two user stack pages to catch kernel faults 208 */ 209 if (freeze_on_seg_fault > 1 && curtd->td_lwp) { 210 pmap_remove(vmspace_pmap(curtd->td_lwp->lwp_vmspace), 211 0x00007FFFFFFFD000LU, 212 0x0000800000000000LU); 213 } 214 #endif 215 } 216 217 /* 218 * Handle signals, upcalls, profiling, and other AST's and/or tasks that 219 * must be completed before we can return to or try to return to userland. 220 * 221 * Note that td_sticks is a 64 bit quantity, but there's no point doing 64 222 * arithmatic on the delta calculation so the absolute tick values are 223 * truncated to an integer. 224 */ 225 static void 226 userret(struct lwp *lp, struct trapframe *frame, int sticks) 227 { 228 struct proc *p = lp->lwp_proc; 229 int sig; 230 int ptok; 231 232 /* 233 * Charge system time if profiling. Note: times are in microseconds. 234 * This may do a copyout and block, so do it first even though it 235 * means some system time will be charged as user time. 236 */ 237 if (p->p_flags & P_PROFIL) { 238 addupc_task(p, frame->tf_rip, 239 (u_int)((int)lp->lwp_thread->td_sticks - sticks)); 240 } 241 242 recheck: 243 /* 244 * Specific on-return-to-usermode checks (LWP_MP_WEXIT, 245 * LWP_MP_VNLRU, etc). 246 */ 247 if (lp->lwp_mpflags & LWP_MP_URETMASK) 248 lwpuserret(lp); 249 250 /* 251 * Block here if we are in a stopped state. 252 */ 253 if (STOPLWP(p, lp)) { 254 lwkt_gettoken(&p->p_token); 255 tstop(); 256 lwkt_reltoken(&p->p_token); 257 goto recheck; 258 } 259 while (dump_stop_usertds) { 260 tsleep(&dump_stop_usertds, 0, "dumpstp", 0); 261 } 262 263 /* 264 * Post any pending upcalls. If running a virtual kernel be sure 265 * to restore the virtual kernel's vmspace before posting the upcall. 266 */ 267 if (p->p_flags & (P_SIGVTALRM | P_SIGPROF)) { 268 lwkt_gettoken(&p->p_token); 269 if (p->p_flags & P_SIGVTALRM) { 270 p->p_flags &= ~P_SIGVTALRM; 271 ksignal(p, SIGVTALRM); 272 } 273 if (p->p_flags & P_SIGPROF) { 274 p->p_flags &= ~P_SIGPROF; 275 ksignal(p, SIGPROF); 276 } 277 lwkt_reltoken(&p->p_token); 278 goto recheck; 279 } 280 281 /* 282 * Post any pending signals. If running a virtual kernel be sure 283 * to restore the virtual kernel's vmspace before posting the signal. 284 * 285 * WARNING! postsig() can exit and not return. 286 */ 287 if ((sig = CURSIG_LCK_TRACE(lp, &ptok)) != 0) { 288 postsig(sig, ptok); 289 goto recheck; 290 } 291 292 /* 293 * block here if we are swapped out, but still process signals 294 * (such as SIGKILL). proc0 (the swapin scheduler) is already 295 * aware of our situation, we do not have to wake it up. 296 */ 297 if (p->p_flags & P_SWAPPEDOUT) { 298 lwkt_gettoken(&p->p_token); 299 p->p_flags |= P_SWAPWAIT; 300 swapin_request(); 301 if (p->p_flags & P_SWAPWAIT) 302 tsleep(p, PCATCH, "SWOUT", 0); 303 p->p_flags &= ~P_SWAPWAIT; 304 lwkt_reltoken(&p->p_token); 305 goto recheck; 306 } 307 308 /* 309 * In a multi-threaded program it is possible for a thread to change 310 * signal state during a system call which temporarily changes the 311 * signal mask. In this case postsig() might not be run and we 312 * have to restore the mask ourselves. 313 */ 314 if (lp->lwp_flags & LWP_OLDMASK) { 315 lp->lwp_flags &= ~LWP_OLDMASK; 316 lp->lwp_sigmask = lp->lwp_oldsigmask; 317 goto recheck; 318 } 319 } 320 321 /* 322 * Cleanup from userenter and any passive release that might have occured. 323 * We must reclaim the current-process designation before we can return 324 * to usermode. We also handle both LWKT and USER reschedule requests. 325 */ 326 static __inline void 327 userexit(struct lwp *lp) 328 { 329 struct thread *td = lp->lwp_thread; 330 /* globaldata_t gd = td->td_gd; */ 331 332 /* 333 * Handle stop requests at kernel priority. Any requests queued 334 * after this loop will generate another AST. 335 */ 336 while (STOPLWP(lp->lwp_proc, lp)) { 337 lwkt_gettoken(&lp->lwp_proc->p_token); 338 tstop(); 339 lwkt_reltoken(&lp->lwp_proc->p_token); 340 } 341 342 /* 343 * Reduce our priority in preparation for a return to userland. If 344 * our passive release function was still in place, our priority was 345 * never raised and does not need to be reduced. 346 */ 347 lwkt_passive_recover(td); 348 349 /* WARNING: we may have migrated cpu's */ 350 /* gd = td->td_gd; */ 351 352 /* 353 * Become the current user scheduled process if we aren't already, 354 * and deal with reschedule requests and other factors. 355 */ 356 lp->lwp_proc->p_usched->acquire_curproc(lp); 357 } 358 359 #if !defined(KTR_KERNENTRY) 360 #define KTR_KERNENTRY KTR_ALL 361 #endif 362 KTR_INFO_MASTER(kernentry); 363 KTR_INFO(KTR_KERNENTRY, kernentry, trap, 0, 364 "TRAP(pid %d, tid %d, trapno %ld, eva %lu)", 365 pid_t pid, lwpid_t tid, register_t trapno, vm_offset_t eva); 366 KTR_INFO(KTR_KERNENTRY, kernentry, trap_ret, 0, "TRAP_RET(pid %d, tid %d)", 367 pid_t pid, lwpid_t tid); 368 KTR_INFO(KTR_KERNENTRY, kernentry, syscall, 0, "SYSC(pid %d, tid %d, nr %ld)", 369 pid_t pid, lwpid_t tid, register_t trapno); 370 KTR_INFO(KTR_KERNENTRY, kernentry, syscall_ret, 0, "SYSRET(pid %d, tid %d, err %d)", 371 pid_t pid, lwpid_t tid, int err); 372 KTR_INFO(KTR_KERNENTRY, kernentry, fork_ret, 0, "FORKRET(pid %d, tid %d)", 373 pid_t pid, lwpid_t tid); 374 375 /* 376 * Exception, fault, and trap interface to the kernel. 377 * This common code is called from assembly language IDT gate entry 378 * routines that prepare a suitable stack frame, and restore this 379 * frame after the exception has been processed. 380 * 381 * This function is also called from doreti in an interlock to handle ASTs. 382 * For example: hardwareint->INTROUTINE->(set ast)->doreti->trap 383 * 384 * NOTE! We have to retrieve the fault address prior to potentially 385 * blocking, including blocking on any token. 386 * 387 * NOTE! NMI and kernel DBG traps remain on their respective pcpu IST 388 * stacks if taken from a kernel RPL. trap() cannot block in this 389 * situation. DDB entry or a direct report-and-return is ok. 390 * 391 * XXX gd_trap_nesting_level currently prevents lwkt_switch() from panicing 392 * if an attempt is made to switch from a fast interrupt or IPI. 393 */ 394 void 395 trap(struct trapframe *frame) 396 { 397 static struct krate sscpubugrate = { 1 }; 398 struct globaldata *gd = mycpu; 399 struct thread *td = gd->gd_curthread; 400 struct lwp *lp = td->td_lwp; 401 struct proc *p; 402 int sticks = 0; 403 int i = 0, ucode = 0, type, code; 404 #ifdef INVARIANTS 405 int crit_count = td->td_critcount; 406 lwkt_tokref_t curstop = td->td_toks_stop; 407 #endif 408 vm_offset_t eva; 409 410 p = td->td_proc; 411 clear_quickret(); 412 413 #ifdef DDB 414 /* 415 * We need to allow T_DNA faults when the debugger is active since 416 * some dumping paths do large bcopy() which use the floating 417 * point registers for faster copying. 418 */ 419 if (db_active && frame->tf_trapno != T_DNA) { 420 eva = (frame->tf_trapno == T_PAGEFLT ? frame->tf_addr : 0); 421 ++gd->gd_trap_nesting_level; 422 trap_fatal(frame, eva); 423 --gd->gd_trap_nesting_level; 424 goto out2; 425 } 426 #endif 427 428 eva = 0; 429 430 if ((frame->tf_rflags & PSL_I) == 0) { 431 /* 432 * Buggy application or kernel code has disabled interrupts 433 * and then trapped. Enabling interrupts now is wrong, but 434 * it is better than running with interrupts disabled until 435 * they are accidentally enabled later. 436 */ 437 438 type = frame->tf_trapno; 439 if (ISPL(frame->tf_cs) == SEL_UPL) { 440 /* JG curproc can be NULL */ 441 kprintf( 442 "pid %ld (%s): trap %d with interrupts disabled\n", 443 (long)curproc->p_pid, curproc->p_comm, type); 444 } else if ((type == T_STKFLT || type == T_PROTFLT || 445 type == T_SEGNPFLT) && 446 frame->tf_rip == (long)doreti_iret) { 447 /* 448 * iretq fault from kernel mode during return to 449 * userland. 450 * 451 * This situation is expected, don't complain. 452 */ 453 } else if (type != T_NMI && type != T_BPTFLT && 454 type != T_TRCTRAP) { 455 /* 456 * XXX not quite right, since this may be for a 457 * multiple fault in user mode. 458 */ 459 kprintf("kernel trap %d (%s @ 0x%016jx) with " 460 "interrupts disabled\n", 461 type, 462 td->td_comm, 463 frame->tf_rip); 464 } 465 cpu_enable_intr(); 466 } 467 468 type = frame->tf_trapno; 469 code = frame->tf_err; 470 471 if (ISPL(frame->tf_cs) == SEL_UPL) { 472 /* user trap */ 473 474 KTR_LOG(kernentry_trap, p->p_pid, lp->lwp_tid, 475 frame->tf_trapno, eva); 476 477 userenter(td, p); 478 479 sticks = (int)td->td_sticks; 480 KASSERT(lp->lwp_md.md_regs == frame, 481 ("Frame mismatch %p %p", lp->lwp_md.md_regs, frame)); 482 483 switch (type) { 484 case T_PRIVINFLT: /* privileged instruction fault */ 485 i = SIGILL; 486 ucode = ILL_PRVOPC; 487 break; 488 489 case T_BPTFLT: /* bpt instruction fault */ 490 case T_TRCTRAP: /* trace trap */ 491 frame->tf_rflags &= ~PSL_T; 492 i = SIGTRAP; 493 ucode = (type == T_TRCTRAP ? TRAP_TRACE : TRAP_BRKPT); 494 break; 495 496 case T_ARITHTRAP: /* arithmetic trap */ 497 ucode = code; 498 i = SIGFPE; 499 break; 500 501 case T_ASTFLT: /* Allow process switch */ 502 mycpu->gd_cnt.v_soft++; 503 if (mycpu->gd_reqflags & RQF_AST_OWEUPC) { 504 atomic_clear_int(&mycpu->gd_reqflags, 505 RQF_AST_OWEUPC); 506 addupc_task(p, p->p_prof.pr_addr, 507 p->p_prof.pr_ticks); 508 } 509 goto out; 510 511 case T_PROTFLT: /* general protection fault */ 512 i = SIGBUS; 513 ucode = BUS_OBJERR; 514 break; 515 case T_STKFLT: /* stack fault */ 516 case T_SEGNPFLT: /* segment not present fault */ 517 i = SIGBUS; 518 ucode = BUS_ADRERR; 519 break; 520 case T_TSSFLT: /* invalid TSS fault */ 521 case T_DOUBLEFLT: /* double fault */ 522 default: 523 i = SIGBUS; 524 ucode = BUS_OBJERR; 525 break; 526 527 case T_PAGEFLT: /* page fault */ 528 i = trap_pfault(frame, TRUE); 529 #ifdef DDB 530 if (frame->tf_rip == 0) { 531 /* used for kernel debugging only */ 532 while (freeze_on_seg_fault) 533 tsleep(p, 0, "freeze", hz * 20); 534 } 535 #endif 536 if (i == -1 || i == 0) 537 goto out; 538 if (i == SIGSEGV) { 539 ucode = SEGV_MAPERR; 540 } else { 541 i = SIGSEGV; 542 ucode = SEGV_ACCERR; 543 } 544 break; 545 546 case T_DIVIDE: /* integer divide fault */ 547 ucode = FPE_INTDIV; 548 i = SIGFPE; 549 break; 550 551 #if NISA > 0 552 case T_NMI: 553 /* machine/parity/power fail/"kitchen sink" faults */ 554 if (isa_nmi(code) == 0) { 555 #ifdef DDB 556 /* 557 * NMI can be hooked up to a pushbutton 558 * for debugging. 559 */ 560 if (ddb_on_nmi) { 561 kprintf ("NMI ... going to debugger\n"); 562 kdb_trap(type, 0, frame); 563 } 564 #endif /* DDB */ 565 goto out2; 566 } else if (panic_on_nmi) 567 panic("NMI indicates hardware failure"); 568 break; 569 #endif /* NISA > 0 */ 570 571 case T_OFLOW: /* integer overflow fault */ 572 ucode = FPE_INTOVF; 573 i = SIGFPE; 574 break; 575 576 case T_BOUND: /* bounds check fault */ 577 ucode = FPE_FLTSUB; 578 i = SIGFPE; 579 break; 580 581 case T_DNA: 582 /* 583 * Virtual kernel intercept - pass the DNA exception 584 * to the virtual kernel if it asked to handle it. 585 * This occurs when the virtual kernel is holding 586 * onto the FP context for a different emulated 587 * process then the one currently running. 588 * 589 * We must still call npxdna() since we may have 590 * saved FP state that the virtual kernel needs 591 * to hand over to a different emulated process. 592 */ 593 if (lp->lwp_vkernel && lp->lwp_vkernel->ve && 594 (td->td_pcb->pcb_flags & FP_VIRTFP) 595 ) { 596 npxdna(); 597 break; 598 } 599 600 /* 601 * The kernel may have switched out the FP unit's 602 * state, causing the user process to take a fault 603 * when it tries to use the FP unit. Restore the 604 * state here 605 */ 606 if (npxdna()) { 607 gd->gd_cnt.v_trap++; 608 goto out; 609 } 610 i = SIGFPE; 611 ucode = FPE_FPU_NP_TRAP; 612 break; 613 614 case T_FPOPFLT: /* FPU operand fetch fault */ 615 ucode = ILL_COPROC; 616 i = SIGILL; 617 break; 618 619 case T_XMMFLT: /* SIMD floating-point exception */ 620 ucode = 0; /* XXX */ 621 i = SIGFPE; 622 break; 623 } 624 } else { 625 /* kernel trap */ 626 627 switch (type) { 628 case T_PAGEFLT: /* page fault */ 629 trap_pfault(frame, FALSE); 630 goto out2; 631 632 case T_DNA: 633 /* 634 * The kernel is apparently using fpu for copying. 635 * XXX this should be fatal unless the kernel has 636 * registered such use. 637 */ 638 if (npxdna()) { 639 gd->gd_cnt.v_trap++; 640 goto out2; 641 } 642 break; 643 644 case T_STKFLT: /* stack fault */ 645 case T_PROTFLT: /* general protection fault */ 646 case T_SEGNPFLT: /* segment not present fault */ 647 /* 648 * Invalid segment selectors and out of bounds 649 * %rip's and %rsp's can be set up in user mode. 650 * This causes a fault in kernel mode when the 651 * kernel tries to return to user mode. We want 652 * to get this fault so that we can fix the 653 * problem here and not have to check all the 654 * selectors and pointers when the user changes 655 * them. 656 */ 657 if (mycpu->gd_intr_nesting_level == 0) { 658 /* 659 * NOTE: in 64-bit mode traps push rsp/ss 660 * even if no ring change occurs. 661 */ 662 if (td->td_pcb->pcb_onfault && 663 td->td_pcb->pcb_onfault_sp == 664 frame->tf_rsp) { 665 frame->tf_rip = (register_t) 666 td->td_pcb->pcb_onfault; 667 goto out2; 668 } 669 670 /* 671 * If the iretq in doreti faults during 672 * return to user, it will be special-cased 673 * in IDTVEC(prot) to get here. We want 674 * to 'return' to doreti_iret_fault in 675 * ipl.s in approximately the same state we 676 * were in at the iretq. 677 */ 678 if (frame->tf_rip == (long)doreti_iret) { 679 frame->tf_rip = (long)doreti_iret_fault; 680 goto out2; 681 } 682 } 683 break; 684 685 case T_TSSFLT: 686 /* 687 * PSL_NT can be set in user mode and isn't cleared 688 * automatically when the kernel is entered. This 689 * causes a TSS fault when the kernel attempts to 690 * `iret' because the TSS link is uninitialized. We 691 * want to get this fault so that we can fix the 692 * problem here and not every time the kernel is 693 * entered. 694 */ 695 if (frame->tf_rflags & PSL_NT) { 696 frame->tf_rflags &= ~PSL_NT; 697 #if 0 698 /* do we need this? */ 699 if (frame->tf_rip == (long)doreti_iret) 700 frame->tf_rip = (long)doreti_iret_fault; 701 #endif 702 goto out2; 703 } 704 break; 705 706 case T_TRCTRAP: /* trace trap */ 707 /* 708 * Detect historical CPU artifact on syscall or int $3 709 * entry (if not shortcutted in exception.s via 710 * DIRECT_DISALLOW_SS_CPUBUG). 711 */ 712 gd->gd_cnt.v_trap++; 713 if (frame->tf_rip == (register_t)IDTVEC(fast_syscall)) { 714 krateprintf(&sscpubugrate, 715 "Caught #DB at syscall cpu artifact\n"); 716 goto out2; 717 } 718 if (frame->tf_rip == (register_t)IDTVEC(bpt)) { 719 krateprintf(&sscpubugrate, 720 "Caught #DB at int $N cpu artifact\n"); 721 goto out2; 722 } 723 724 /* 725 * Ignore debug register trace traps due to 726 * accesses in the user's address space, which 727 * can happen under several conditions such as 728 * if a user sets a watchpoint on a buffer and 729 * then passes that buffer to a system call. 730 * We still want to get TRCTRAPS for addresses 731 * in kernel space because that is useful when 732 * debugging the kernel. 733 */ 734 if (user_dbreg_trap()) { 735 /* 736 * Reset breakpoint bits because the 737 * processor doesn't 738 */ 739 load_dr6(rdr6() & ~0xf); 740 goto out2; 741 } 742 /* 743 * FALLTHROUGH (TRCTRAP kernel mode, kernel address) 744 */ 745 case T_BPTFLT: 746 /* 747 * If DDB is enabled, let it handle the debugger trap. 748 * Otherwise, debugger traps "can't happen". 749 */ 750 ucode = TRAP_BRKPT; 751 #ifdef DDB 752 if (kdb_trap(type, 0, frame)) 753 goto out2; 754 #endif 755 break; 756 757 #if NISA > 0 758 case T_NMI: 759 /* machine/parity/power fail/"kitchen sink" faults */ 760 if (isa_nmi(code) == 0) { 761 #ifdef DDB 762 /* 763 * NMI can be hooked up to a pushbutton 764 * for debugging. 765 */ 766 if (ddb_on_nmi) { 767 kprintf ("NMI ... going to debugger\n"); 768 kdb_trap(type, 0, frame); 769 } 770 #endif /* DDB */ 771 goto out2; 772 } else if (panic_on_nmi == 0) 773 goto out2; 774 /* FALL THROUGH */ 775 #endif /* NISA > 0 */ 776 } 777 trap_fatal(frame, 0); 778 goto out2; 779 } 780 781 /* 782 * Fault from user mode, virtual kernel interecept. 783 * 784 * If the fault is directly related to a VM context managed by a 785 * virtual kernel then let the virtual kernel handle it. 786 */ 787 if (lp->lwp_vkernel && lp->lwp_vkernel->ve) { 788 vkernel_trap(lp, frame); 789 goto out; 790 } 791 792 /* Translate fault for emulators (e.g. Linux) */ 793 if (*p->p_sysent->sv_transtrap) 794 i = (*p->p_sysent->sv_transtrap)(i, type); 795 796 gd->gd_cnt.v_trap++; 797 trapsignal(lp, i, ucode); 798 799 #ifdef DEBUG 800 if (type <= MAX_TRAP_MSG) { 801 uprintf("fatal process exception: %s", 802 trap_msg[type]); 803 if ((type == T_PAGEFLT) || (type == T_PROTFLT)) 804 uprintf(", fault VA = 0x%lx", frame->tf_addr); 805 uprintf("\n"); 806 } 807 #endif 808 809 out: 810 userret(lp, frame, sticks); 811 userexit(lp); 812 out2: ; 813 if (p != NULL && lp != NULL) 814 KTR_LOG(kernentry_trap_ret, p->p_pid, lp->lwp_tid); 815 #ifdef INVARIANTS 816 KASSERT(crit_count == td->td_critcount, 817 ("trap: critical section count mismatch! %d/%d", 818 crit_count, td->td_pri)); 819 KASSERT(curstop == td->td_toks_stop, 820 ("trap: extra tokens held after trap! %ld/%ld", 821 curstop - &td->td_toks_base, 822 td->td_toks_stop - &td->td_toks_base)); 823 #endif 824 } 825 826 void 827 trap_handle_userenter(struct thread *td) 828 { 829 userenter(td, td->td_proc); 830 } 831 832 void 833 trap_handle_userexit(struct trapframe *frame, int sticks) 834 { 835 struct lwp *lp = curthread->td_lwp; 836 837 if (lp) { 838 userret(lp, frame, sticks); 839 userexit(lp); 840 } 841 } 842 843 static int 844 trap_pfault(struct trapframe *frame, int usermode) 845 { 846 vm_offset_t va; 847 struct vmspace *vm = NULL; 848 vm_map_t map; 849 int rv = 0; 850 int fault_flags; 851 vm_prot_t ftype; 852 thread_t td = curthread; 853 struct lwp *lp = td->td_lwp; 854 struct proc *p; 855 856 va = trunc_page(frame->tf_addr); 857 if (va >= VM_MIN_KERNEL_ADDRESS) { 858 /* 859 * Don't allow user-mode faults in kernel address space. 860 */ 861 if (usermode) { 862 fault_flags = -1; 863 ftype = -1; 864 goto nogo; 865 } 866 867 map = &kernel_map; 868 } else { 869 /* 870 * This is a fault on non-kernel virtual memory. 871 * vm is initialized above to NULL. If curproc is NULL 872 * or curproc->p_vmspace is NULL the fault is fatal. 873 */ 874 if (lp != NULL) 875 vm = lp->lwp_vmspace; 876 877 if (vm == NULL) { 878 fault_flags = -1; 879 ftype = -1; 880 goto nogo; 881 } 882 883 /* 884 * Debugging, try to catch kernel faults on the user address 885 * space when not inside on onfault (e.g. copyin/copyout) 886 * routine. 887 */ 888 if (usermode == 0 && (td->td_pcb == NULL || 889 td->td_pcb->pcb_onfault == NULL)) { 890 #ifdef DDB 891 if (freeze_on_seg_fault) { 892 kprintf("trap_pfault: user address fault from kernel mode " 893 "%016lx\n", (long)frame->tf_addr); 894 while (freeze_on_seg_fault) 895 tsleep(&freeze_on_seg_fault, 0, "frzseg", hz * 20); 896 } 897 #endif 898 } 899 map = &vm->vm_map; 900 } 901 902 /* 903 * PGEX_I is defined only if the execute disable bit capability is 904 * supported and enabled. 905 */ 906 if (frame->tf_err & PGEX_W) 907 ftype = VM_PROT_WRITE; 908 else if (frame->tf_err & PGEX_I) 909 ftype = VM_PROT_EXECUTE; 910 else 911 ftype = VM_PROT_READ; 912 913 if (map != &kernel_map) { 914 /* 915 * Keep swapout from messing with us during this 916 * critical time. 917 */ 918 PHOLD(lp->lwp_proc); 919 920 /* 921 * Issue fault 922 */ 923 fault_flags = 0; 924 if (usermode) 925 fault_flags |= VM_FAULT_BURST | VM_FAULT_USERMODE; 926 if (ftype & VM_PROT_WRITE) 927 fault_flags |= VM_FAULT_DIRTY; 928 else 929 fault_flags |= VM_FAULT_NORMAL; 930 rv = vm_fault(map, va, ftype, fault_flags); 931 932 PRELE(lp->lwp_proc); 933 } else { 934 /* 935 * Don't have to worry about process locking or stacks in the 936 * kernel. 937 */ 938 fault_flags = VM_FAULT_NORMAL; 939 rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL); 940 } 941 if (rv == KERN_SUCCESS) 942 return (0); 943 nogo: 944 if (!usermode) { 945 /* 946 * NOTE: in 64-bit mode traps push rsp/ss 947 * even if no ring change occurs. 948 */ 949 if (td->td_pcb->pcb_onfault && 950 td->td_pcb->pcb_onfault_sp == frame->tf_rsp && 951 td->td_gd->gd_intr_nesting_level == 0) { 952 frame->tf_rip = (register_t)td->td_pcb->pcb_onfault; 953 return (0); 954 } 955 trap_fatal(frame, frame->tf_addr); 956 return (-1); 957 } 958 959 /* 960 * NOTE: on x86_64 we have a tf_addr field in the trapframe, no 961 * kludge is needed to pass the fault address to signal handlers. 962 */ 963 p = td->td_proc; 964 #ifdef DDB 965 if (td->td_lwp->lwp_vkernel == NULL) { 966 while (freeze_on_seg_fault) { 967 tsleep(p, 0, "freeze", hz * 20); 968 } 969 if (ddb_on_seg_fault) 970 Debugger("ddb_on_seg_fault"); 971 } 972 #endif 973 974 return((rv == KERN_PROTECTION_FAILURE) ? SIGBUS : SIGSEGV); 975 } 976 977 static void 978 trap_fatal(struct trapframe *frame, vm_offset_t eva) 979 { 980 int code, ss; 981 u_int type; 982 long rsp; 983 struct soft_segment_descriptor softseg; 984 char *msg; 985 986 code = frame->tf_err; 987 type = frame->tf_trapno; 988 sdtossd(&gdt[IDXSEL(frame->tf_cs & 0xffff)], &softseg); 989 990 if (type <= MAX_TRAP_MSG) 991 msg = trap_msg[type]; 992 else 993 msg = "UNKNOWN"; 994 kprintf("\n\nFatal trap %d: %s while in %s mode\n", type, msg, 995 ISPL(frame->tf_cs) == SEL_UPL ? "user" : "kernel"); 996 /* three separate prints in case of a trap on an unmapped page */ 997 kprintf("cpuid = %d; ", mycpu->gd_cpuid); 998 if (lapic_usable) 999 kprintf("lapic id = %u\n", LAPIC_READID); 1000 if (type == T_PAGEFLT) { 1001 kprintf("fault virtual address = 0x%lx\n", eva); 1002 kprintf("fault code = %s %s %s, %s\n", 1003 code & PGEX_U ? "user" : "supervisor", 1004 code & PGEX_W ? "write" : "read", 1005 code & PGEX_I ? "instruction" : "data", 1006 code & PGEX_P ? "protection violation" : "page not present"); 1007 } 1008 kprintf("instruction pointer = 0x%lx:0x%lx\n", 1009 frame->tf_cs & 0xffff, frame->tf_rip); 1010 if (ISPL(frame->tf_cs) == SEL_UPL) { 1011 ss = frame->tf_ss & 0xffff; 1012 rsp = frame->tf_rsp; 1013 } else { 1014 /* 1015 * NOTE: in 64-bit mode traps push rsp/ss even if no ring 1016 * change occurs. 1017 */ 1018 ss = GSEL(GDATA_SEL, SEL_KPL); 1019 rsp = frame->tf_rsp; 1020 } 1021 kprintf("stack pointer = 0x%x:0x%lx\n", ss, rsp); 1022 kprintf("frame pointer = 0x%x:0x%lx\n", ss, frame->tf_rbp); 1023 kprintf("code segment = base 0x%lx, limit 0x%lx, type 0x%x\n", 1024 softseg.ssd_base, softseg.ssd_limit, softseg.ssd_type); 1025 kprintf(" = DPL %d, pres %d, long %d, def32 %d, gran %d\n", 1026 softseg.ssd_dpl, softseg.ssd_p, softseg.ssd_long, softseg.ssd_def32, 1027 softseg.ssd_gran); 1028 kprintf("processor eflags = "); 1029 if (frame->tf_rflags & PSL_T) 1030 kprintf("trace trap, "); 1031 if (frame->tf_rflags & PSL_I) 1032 kprintf("interrupt enabled, "); 1033 if (frame->tf_rflags & PSL_NT) 1034 kprintf("nested task, "); 1035 if (frame->tf_rflags & PSL_RF) 1036 kprintf("resume, "); 1037 kprintf("IOPL = %ld\n", (frame->tf_rflags & PSL_IOPL) >> 12); 1038 kprintf("current process = "); 1039 if (curproc) { 1040 kprintf("%lu\n", 1041 (u_long)curproc->p_pid); 1042 } else { 1043 kprintf("Idle\n"); 1044 } 1045 kprintf("current thread = pri %d ", curthread->td_pri); 1046 if (curthread->td_critcount) 1047 kprintf("(CRIT)"); 1048 kprintf("\n"); 1049 1050 #ifdef DDB 1051 if ((debugger_on_panic || db_active) && kdb_trap(type, code, frame)) 1052 return; 1053 #endif 1054 kprintf("trap number = %d\n", type); 1055 if (type <= MAX_TRAP_MSG) 1056 panic("%s", trap_msg[type]); 1057 else 1058 panic("unknown/reserved trap"); 1059 } 1060 1061 /* 1062 * Double fault handler. Called when a fault occurs while writing 1063 * a frame for a trap/exception onto the stack. This usually occurs 1064 * when the stack overflows (such is the case with infinite recursion, 1065 * for example). 1066 */ 1067 static __inline 1068 int 1069 in_kstack_guard(register_t rptr) 1070 { 1071 thread_t td = curthread; 1072 1073 if ((char *)rptr >= td->td_kstack && 1074 (char *)rptr < td->td_kstack + PAGE_SIZE) { 1075 return 1; 1076 } 1077 return 0; 1078 } 1079 1080 void 1081 dblfault_handler(struct trapframe *frame) 1082 { 1083 thread_t td = curthread; 1084 1085 if (in_kstack_guard(frame->tf_rsp) || in_kstack_guard(frame->tf_rbp)) { 1086 kprintf("DOUBLE FAULT - KERNEL STACK GUARD HIT!\n"); 1087 if (in_kstack_guard(frame->tf_rsp)) 1088 frame->tf_rsp = (register_t)(td->td_kstack + PAGE_SIZE); 1089 if (in_kstack_guard(frame->tf_rbp)) 1090 frame->tf_rbp = (register_t)(td->td_kstack + PAGE_SIZE); 1091 } else { 1092 kprintf("DOUBLE FAULT\n"); 1093 } 1094 kprintf("\nFatal double fault\n"); 1095 kprintf("rip = 0x%lx\n", frame->tf_rip); 1096 kprintf("rsp = 0x%lx\n", frame->tf_rsp); 1097 kprintf("rbp = 0x%lx\n", frame->tf_rbp); 1098 /* three separate prints in case of a trap on an unmapped page */ 1099 kprintf("cpuid = %d; ", mycpu->gd_cpuid); 1100 if (lapic_usable) 1101 kprintf("lapic id = %u\n", LAPIC_READID); 1102 panic("double fault"); 1103 } 1104 1105 /* 1106 * syscall2 - MP aware system call request C handler 1107 * 1108 * A system call is essentially treated as a trap except that the 1109 * MP lock is not held on entry or return. We are responsible for 1110 * obtaining the MP lock if necessary and for handling ASTs 1111 * (e.g. a task switch) prior to return. 1112 * 1113 * MPSAFE 1114 */ 1115 void 1116 syscall2(struct trapframe *frame) 1117 { 1118 struct thread *td = curthread; 1119 struct proc *p = td->td_proc; 1120 struct lwp *lp = td->td_lwp; 1121 struct sysent *callp; 1122 register_t orig_tf_rflags; 1123 int sticks; 1124 int error; 1125 int narg; 1126 #ifdef INVARIANTS 1127 int crit_count = td->td_critcount; 1128 #endif 1129 register_t *argp; 1130 u_int code; 1131 int regcnt, optimized_regcnt; 1132 union sysunion args; 1133 register_t *argsdst; 1134 1135 mycpu->gd_cnt.v_syscall++; 1136 1137 #ifdef DIAGNOSTIC 1138 if (ISPL(frame->tf_cs) != SEL_UPL) { 1139 panic("syscall"); 1140 /* NOT REACHED */ 1141 } 1142 #endif 1143 1144 KTR_LOG(kernentry_syscall, p->p_pid, lp->lwp_tid, 1145 frame->tf_rax); 1146 1147 userenter(td, p); /* lazy raise our priority */ 1148 1149 regcnt = 6; 1150 optimized_regcnt = 6; 1151 1152 /* 1153 * Misc 1154 */ 1155 sticks = (int)td->td_sticks; 1156 orig_tf_rflags = frame->tf_rflags; 1157 1158 /* 1159 * Virtual kernel intercept - if a VM context managed by a virtual 1160 * kernel issues a system call the virtual kernel handles it, not us. 1161 * Restore the virtual kernel context and return from its system 1162 * call. The current frame is copied out to the virtual kernel. 1163 */ 1164 if (lp->lwp_vkernel && lp->lwp_vkernel->ve) { 1165 vkernel_trap(lp, frame); 1166 error = EJUSTRETURN; 1167 callp = NULL; 1168 code = 0; 1169 goto out; 1170 } 1171 1172 /* 1173 * Get the system call parameters and account for time 1174 */ 1175 KASSERT(lp->lwp_md.md_regs == frame, 1176 ("Frame mismatch %p %p", lp->lwp_md.md_regs, frame)); 1177 code = (u_int)frame->tf_rax; 1178 1179 if (code == SYS_syscall || code == SYS___syscall) { 1180 code = frame->tf_rdi; 1181 regcnt--; 1182 argp = &frame->tf_rdi + 1; 1183 } else { 1184 argp = &frame->tf_rdi; 1185 } 1186 1187 if (code >= p->p_sysent->sv_size) 1188 callp = &p->p_sysent->sv_table[0]; 1189 else 1190 callp = &p->p_sysent->sv_table[code]; 1191 1192 narg = callp->sy_narg & SYF_ARGMASK; 1193 1194 /* 1195 * On x86_64 we get up to six arguments in registers. The rest are 1196 * on the stack. The first six members of 'struct trapframe' happen 1197 * to be the registers used to pass arguments, in exactly the right 1198 * order. 1199 */ 1200 argsdst = (register_t *)(&args.nosys.sysmsg + 1); 1201 1202 /* 1203 * Its easier to copy up to the highest number of syscall arguments 1204 * passed in registers, which is 6, than to conditionalize it. 1205 */ 1206 bcopy(argp, argsdst, sizeof(register_t) * optimized_regcnt); 1207 1208 /* 1209 * Any arguments beyond available argument-passing registers must 1210 * be copyin()'d from the user stack. 1211 */ 1212 if (narg > regcnt) { 1213 caddr_t params; 1214 1215 params = (caddr_t)frame->tf_rsp + sizeof(register_t); 1216 error = copyin(params, &argsdst[regcnt], 1217 (narg - regcnt) * sizeof(register_t)); 1218 if (error) { 1219 #ifdef KTRACE 1220 if (KTRPOINT(td, KTR_SYSCALL)) { 1221 ktrsyscall(lp, code, narg, 1222 (void *)(&args.nosys.sysmsg + 1)); 1223 } 1224 #endif 1225 goto bad; 1226 } 1227 } 1228 1229 #ifdef KTRACE 1230 if (KTRPOINT(td, KTR_SYSCALL)) { 1231 ktrsyscall(lp, code, narg, (void *)(&args.nosys.sysmsg + 1)); 1232 } 1233 #endif 1234 1235 /* 1236 * Default return value is 0 (will be copied to %rax). Double-value 1237 * returns use %rax and %rdx. %rdx is left unchanged for system 1238 * calls which return only one result. 1239 */ 1240 args.sysmsg_fds[0] = 0; 1241 args.sysmsg_fds[1] = frame->tf_rdx; 1242 1243 /* 1244 * The syscall might manipulate the trap frame. If it does it 1245 * will probably return EJUSTRETURN. 1246 */ 1247 args.sysmsg_frame = frame; 1248 1249 STOPEVENT(p, S_SCE, narg); /* MP aware */ 1250 1251 /* 1252 * NOTE: All system calls run MPSAFE now. The system call itself 1253 * is responsible for getting the MP lock. 1254 */ 1255 #ifdef SYSCALL_DEBUG 1256 tsc_uclock_t tscval = rdtsc(); 1257 #endif 1258 error = (*callp->sy_call)(&args); 1259 #ifdef SYSCALL_DEBUG 1260 tscval = rdtsc() - tscval; 1261 tscval = tscval * 1000000 / tsc_frequency; 1262 if (SysCallsWorstCase[code] < tscval) 1263 SysCallsWorstCase[code] = tscval; 1264 #endif 1265 1266 out: 1267 /* 1268 * MP SAFE (we may or may not have the MP lock at this point) 1269 */ 1270 //kprintf("SYSMSG %d ", error); 1271 switch (error) { 1272 case 0: 1273 /* 1274 * Reinitialize proc pointer `p' as it may be different 1275 * if this is a child returning from fork syscall. 1276 */ 1277 p = curproc; 1278 lp = curthread->td_lwp; 1279 frame->tf_rax = args.sysmsg_fds[0]; 1280 frame->tf_rdx = args.sysmsg_fds[1]; 1281 frame->tf_rflags &= ~PSL_C; 1282 break; 1283 case ERESTART: 1284 /* 1285 * Reconstruct pc, we know that 'syscall' is 2 bytes. 1286 * We have to do a full context restore so that %r10 1287 * (which was holding the value of %rcx) is restored for 1288 * the next iteration. 1289 */ 1290 if (frame->tf_err != 0 && frame->tf_err != 2) 1291 kprintf("lp %s:%d frame->tf_err is weird %ld\n", 1292 td->td_comm, lp->lwp_proc->p_pid, frame->tf_err); 1293 frame->tf_rip -= frame->tf_err; 1294 frame->tf_r10 = frame->tf_rcx; 1295 break; 1296 case EJUSTRETURN: 1297 break; 1298 case EASYNC: 1299 panic("Unexpected EASYNC return value (for now)"); 1300 default: 1301 bad: 1302 if (p->p_sysent->sv_errsize) { 1303 if (error >= p->p_sysent->sv_errsize) 1304 error = -1; /* XXX */ 1305 else 1306 error = p->p_sysent->sv_errtbl[error]; 1307 } 1308 frame->tf_rax = error; 1309 frame->tf_rflags |= PSL_C; 1310 break; 1311 } 1312 1313 /* 1314 * Traced syscall. trapsignal() should now be MP aware 1315 */ 1316 if (orig_tf_rflags & PSL_T) { 1317 frame->tf_rflags &= ~PSL_T; 1318 trapsignal(lp, SIGTRAP, TRAP_TRACE); 1319 } 1320 1321 /* 1322 * Handle reschedule and other end-of-syscall issues 1323 */ 1324 userret(lp, frame, sticks); 1325 1326 #ifdef KTRACE 1327 if (KTRPOINT(td, KTR_SYSRET)) { 1328 ktrsysret(lp, code, error, args.sysmsg_result); 1329 } 1330 #endif 1331 1332 /* 1333 * This works because errno is findable through the 1334 * register set. If we ever support an emulation where this 1335 * is not the case, this code will need to be revisited. 1336 */ 1337 STOPEVENT(p, S_SCX, code); 1338 1339 userexit(lp); 1340 KTR_LOG(kernentry_syscall_ret, p->p_pid, lp->lwp_tid, error); 1341 #ifdef INVARIANTS 1342 KASSERT(crit_count == td->td_critcount, 1343 ("syscall: critical section count mismatch! %d/%d", 1344 crit_count, td->td_pri)); 1345 KASSERT(&td->td_toks_base == td->td_toks_stop, 1346 ("syscall: %ld extra tokens held after trap! syscall %p", 1347 td->td_toks_stop - &td->td_toks_base, 1348 callp->sy_call)); 1349 #endif 1350 } 1351 1352 void 1353 fork_return(struct lwp *lp, struct trapframe *frame) 1354 { 1355 frame->tf_rax = 0; /* Child returns zero */ 1356 frame->tf_rflags &= ~PSL_C; /* success */ 1357 frame->tf_rdx = 1; 1358 1359 generic_lwp_return(lp, frame); 1360 KTR_LOG(kernentry_fork_ret, lp->lwp_proc->p_pid, lp->lwp_tid); 1361 } 1362 1363 /* 1364 * Simplified back end of syscall(), used when returning from fork() 1365 * directly into user mode. 1366 * 1367 * This code will return back into the fork trampoline code which then 1368 * runs doreti. 1369 */ 1370 void 1371 generic_lwp_return(struct lwp *lp, struct trapframe *frame) 1372 { 1373 struct proc *p = lp->lwp_proc; 1374 1375 /* 1376 * Check for exit-race. If one lwp exits the process concurrent with 1377 * another lwp creating a new thread, the two operations may cross 1378 * each other resulting in the newly-created lwp not receiving a 1379 * KILL signal. 1380 */ 1381 if (p->p_flags & P_WEXIT) { 1382 lwpsignal(p, lp, SIGKILL); 1383 } 1384 1385 /* 1386 * Newly forked processes are given a kernel priority. We have to 1387 * adjust the priority to a normal user priority and fake entry 1388 * into the kernel (call userenter()) to install a passive release 1389 * function just in case userret() decides to stop the process. This 1390 * can occur when ^Z races a fork. If we do not install the passive 1391 * release function the current process designation will not be 1392 * released when the thread goes to sleep. 1393 */ 1394 lwkt_setpri_self(TDPRI_USER_NORM); 1395 userenter(lp->lwp_thread, p); 1396 userret(lp, frame, 0); 1397 #ifdef KTRACE 1398 if (KTRPOINT(lp->lwp_thread, KTR_SYSRET)) 1399 ktrsysret(lp, SYS_fork, 0, 0); 1400 #endif 1401 lp->lwp_flags |= LWP_PASSIVE_ACQ; 1402 userexit(lp); 1403 lp->lwp_flags &= ~LWP_PASSIVE_ACQ; 1404 } 1405 1406 /* 1407 * If PGEX_FPFAULT is set then set FP_VIRTFP in the PCB to force a T_DNA 1408 * fault (which is then passed back to the virtual kernel) if an attempt is 1409 * made to use the FP unit. 1410 * 1411 * XXX this is a fairly big hack. 1412 */ 1413 void 1414 set_vkernel_fp(struct trapframe *frame) 1415 { 1416 struct thread *td = curthread; 1417 1418 if (frame->tf_xflags & PGEX_FPFAULT) { 1419 td->td_pcb->pcb_flags |= FP_VIRTFP; 1420 if (mdcpu->gd_npxthread == td) 1421 npxexit(); 1422 } else { 1423 td->td_pcb->pcb_flags &= ~FP_VIRTFP; 1424 } 1425 } 1426 1427 /* 1428 * Called from vkernel_trap() to fixup the vkernel's syscall 1429 * frame for vmspace_ctl() return. 1430 */ 1431 void 1432 cpu_vkernel_trap(struct trapframe *frame, int error) 1433 { 1434 frame->tf_rax = error; 1435 if (error) 1436 frame->tf_rflags |= PSL_C; 1437 else 1438 frame->tf_rflags &= ~PSL_C; 1439 } 1440