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 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 #include <sys/systm.h> 65 #ifdef KTRACE 66 #include <sys/ktrace.h> 67 #endif 68 #include <sys/ktr.h> 69 #include <sys/sysmsg.h> 70 #include <sys/sysproto.h> 71 #include <sys/sysunion.h> 72 73 #include <vm/pmap.h> 74 #include <vm/vm.h> 75 #include <vm/vm_extern.h> 76 #include <vm/vm_kern.h> 77 #include <vm/vm_param.h> 78 #include <machine/cpu.h> 79 #include <machine/pcb.h> 80 #include <machine/smp.h> 81 #include <machine/thread.h> 82 #include <machine/clock.h> 83 #include <machine/vmparam.h> 84 #include <machine/md_var.h> 85 #include <machine_base/isa/isa_intr.h> 86 #include <machine_base/apic/lapic.h> 87 88 #include <ddb/ddb.h> 89 90 #include <sys/thread2.h> 91 #include <sys/mplock2.h> 92 93 #ifdef SMP 94 95 #define MAKEMPSAFE(have_mplock) \ 96 if (have_mplock == 0) { \ 97 get_mplock(); \ 98 have_mplock = 1; \ 99 } 100 101 #else 102 103 #define MAKEMPSAFE(have_mplock) 104 105 #endif 106 107 extern void trap(struct trapframe *frame); 108 109 static int trap_pfault(struct trapframe *, int); 110 static void trap_fatal(struct trapframe *, vm_offset_t); 111 void dblfault_handler(struct trapframe *frame); 112 113 #define MAX_TRAP_MSG 30 114 static char *trap_msg[] = { 115 "", /* 0 unused */ 116 "privileged instruction fault", /* 1 T_PRIVINFLT */ 117 "", /* 2 unused */ 118 "breakpoint instruction fault", /* 3 T_BPTFLT */ 119 "", /* 4 unused */ 120 "", /* 5 unused */ 121 "arithmetic trap", /* 6 T_ARITHTRAP */ 122 "system forced exception", /* 7 T_ASTFLT */ 123 "", /* 8 unused */ 124 "general protection fault", /* 9 T_PROTFLT */ 125 "trace trap", /* 10 T_TRCTRAP */ 126 "", /* 11 unused */ 127 "page fault", /* 12 T_PAGEFLT */ 128 "", /* 13 unused */ 129 "alignment fault", /* 14 T_ALIGNFLT */ 130 "", /* 15 unused */ 131 "", /* 16 unused */ 132 "", /* 17 unused */ 133 "integer divide fault", /* 18 T_DIVIDE */ 134 "non-maskable interrupt trap", /* 19 T_NMI */ 135 "overflow trap", /* 20 T_OFLOW */ 136 "FPU bounds check fault", /* 21 T_BOUND */ 137 "FPU device not available", /* 22 T_DNA */ 138 "double fault", /* 23 T_DOUBLEFLT */ 139 "FPU operand fetch fault", /* 24 T_FPOPFLT */ 140 "invalid TSS fault", /* 25 T_TSSFLT */ 141 "segment not present fault", /* 26 T_SEGNPFLT */ 142 "stack fault", /* 27 T_STKFLT */ 143 "machine check trap", /* 28 T_MCHK */ 144 "SIMD floating-point exception", /* 29 T_XMMFLT */ 145 "reserved (unknown) fault", /* 30 T_RESERVED */ 146 }; 147 148 #ifdef DDB 149 static int ddb_on_nmi = 1; 150 SYSCTL_INT(_machdep, OID_AUTO, ddb_on_nmi, CTLFLAG_RW, 151 &ddb_on_nmi, 0, "Go to DDB on NMI"); 152 static int ddb_on_seg_fault = 0; 153 SYSCTL_INT(_machdep, OID_AUTO, ddb_on_seg_fault, CTLFLAG_RW, 154 &ddb_on_seg_fault, 0, "Go to DDB on user seg-fault"); 155 static int freeze_on_seg_fault = 0; 156 SYSCTL_INT(_machdep, OID_AUTO, freeze_on_seg_fault, CTLFLAG_RW, 157 &freeze_on_seg_fault, 0, "Go to DDB on user seg-fault"); 158 #endif 159 static int panic_on_nmi = 1; 160 SYSCTL_INT(_machdep, OID_AUTO, panic_on_nmi, CTLFLAG_RW, 161 &panic_on_nmi, 0, "Panic on NMI"); 162 static int fast_release; 163 SYSCTL_INT(_machdep, OID_AUTO, fast_release, CTLFLAG_RW, 164 &fast_release, 0, "Passive Release was optimal"); 165 static int slow_release; 166 SYSCTL_INT(_machdep, OID_AUTO, slow_release, CTLFLAG_RW, 167 &slow_release, 0, "Passive Release was nonoptimal"); 168 169 /* 170 * System call debugging records the worst-case system call 171 * overhead (inclusive of blocking), but may be inaccurate. 172 */ 173 /*#define SYSCALL_DEBUG*/ 174 #ifdef SYSCALL_DEBUG 175 uint64_t SysCallsWorstCase[SYS_MAXSYSCALL]; 176 #endif 177 178 /* 179 * Passively intercepts the thread switch function to increase 180 * the thread priority from a user priority to a kernel priority, reducing 181 * syscall and trap overhead for the case where no switch occurs. 182 * 183 * Synchronizes td_ucred with p_ucred. This is used by system calls, 184 * signal handling, faults, AST traps, and anything else that enters the 185 * kernel from userland and provides the kernel with a stable read-only 186 * copy of the process ucred. 187 */ 188 static __inline void 189 userenter(struct thread *curtd, struct proc *curp) 190 { 191 struct ucred *ocred; 192 struct ucred *ncred; 193 194 curtd->td_release = lwkt_passive_release; 195 196 if (curtd->td_ucred != curp->p_ucred) { 197 ncred = crhold(curp->p_ucred); 198 ocred = curtd->td_ucred; 199 curtd->td_ucred = ncred; 200 if (ocred) 201 crfree(ocred); 202 } 203 204 #ifdef DDB 205 /* 206 * Debugging, remove top two user stack pages to catch kernel faults 207 */ 208 if (freeze_on_seg_fault > 1 && curtd->td_lwp) { 209 pmap_remove(vmspace_pmap(curtd->td_lwp->lwp_vmspace), 210 0x00007FFFFFFFD000LU, 211 0x0000800000000000LU); 212 } 213 #endif 214 } 215 216 /* 217 * Handle signals, upcalls, profiling, and other AST's and/or tasks that 218 * must be completed before we can return to or try to return to userland. 219 * 220 * Note that td_sticks is a 64 bit quantity, but there's no point doing 64 221 * arithmatic on the delta calculation so the absolute tick values are 222 * truncated to an integer. 223 */ 224 static void 225 userret(struct lwp *lp, struct trapframe *frame, int sticks) 226 { 227 struct proc *p = lp->lwp_proc; 228 int sig; 229 230 /* 231 * Charge system time if profiling. Note: times are in microseconds. 232 * This may do a copyout and block, so do it first even though it 233 * means some system time will be charged as user time. 234 */ 235 if (p->p_flags & P_PROFIL) { 236 addupc_task(p, frame->tf_rip, 237 (u_int)((int)lp->lwp_thread->td_sticks - sticks)); 238 } 239 240 recheck: 241 /* 242 * If the jungle wants us dead, so be it. 243 */ 244 if (lp->lwp_mpflags & LWP_MP_WEXIT) { 245 lwkt_gettoken(&p->p_token); 246 lwp_exit(0); 247 lwkt_reltoken(&p->p_token); /* NOT REACHED */ 248 } 249 250 /* 251 * Block here if we are in a stopped state. 252 */ 253 if (p->p_stat == SSTOP || dump_stop_usertds) { 254 lwkt_gettoken(&p->p_token); 255 tstop(); 256 lwkt_reltoken(&p->p_token); 257 goto recheck; 258 } 259 260 /* 261 * Post any pending upcalls. If running a virtual kernel be sure 262 * to restore the virtual kernel's vmspace before posting the upcall. 263 */ 264 if (p->p_flags & (P_SIGVTALRM | P_SIGPROF | P_UPCALLPEND)) { 265 lwkt_gettoken(&p->p_token); 266 if (p->p_flags & P_SIGVTALRM) { 267 p->p_flags &= ~P_SIGVTALRM; 268 ksignal(p, SIGVTALRM); 269 } 270 if (p->p_flags & P_SIGPROF) { 271 p->p_flags &= ~P_SIGPROF; 272 ksignal(p, SIGPROF); 273 } 274 if (p->p_flags & P_UPCALLPEND) { 275 p->p_flags &= ~P_UPCALLPEND; 276 postupcall(lp); 277 } 278 lwkt_reltoken(&p->p_token); 279 goto recheck; 280 } 281 282 /* 283 * Post any pending signals. If running a virtual kernel be sure 284 * to restore the virtual kernel's vmspace before posting the signal. 285 * 286 * WARNING! postsig() can exit and not return. 287 */ 288 if ((sig = CURSIG_TRACE(lp)) != 0) { 289 lwkt_gettoken(&p->p_token); 290 postsig(sig); 291 lwkt_reltoken(&p->p_token); 292 goto recheck; 293 } 294 295 /* 296 * block here if we are swapped out, but still process signals 297 * (such as SIGKILL). proc0 (the swapin scheduler) is already 298 * aware of our situation, we do not have to wake it up. 299 */ 300 if (p->p_flags & P_SWAPPEDOUT) { 301 lwkt_gettoken(&p->p_token); 302 get_mplock(); 303 p->p_flags |= P_SWAPWAIT; 304 swapin_request(); 305 if (p->p_flags & P_SWAPWAIT) 306 tsleep(p, PCATCH, "SWOUT", 0); 307 p->p_flags &= ~P_SWAPWAIT; 308 rel_mplock(); 309 lwkt_reltoken(&p->p_token); 310 goto recheck; 311 } 312 313 /* 314 * In a multi-threaded program it is possible for a thread to change 315 * signal state during a system call which temporarily changes the 316 * signal mask. In this case postsig() might not be run and we 317 * have to restore the mask ourselves. 318 */ 319 if (lp->lwp_flags & LWP_OLDMASK) { 320 lp->lwp_flags &= ~LWP_OLDMASK; 321 lp->lwp_sigmask = lp->lwp_oldsigmask; 322 goto recheck; 323 } 324 } 325 326 /* 327 * Cleanup from userenter and any passive release that might have occured. 328 * We must reclaim the current-process designation before we can return 329 * to usermode. We also handle both LWKT and USER reschedule requests. 330 */ 331 static __inline void 332 userexit(struct lwp *lp) 333 { 334 struct thread *td = lp->lwp_thread; 335 /* globaldata_t gd = td->td_gd; */ 336 337 /* 338 * Handle stop requests at kernel priority. Any requests queued 339 * after this loop will generate another AST. 340 */ 341 while (lp->lwp_proc->p_stat == SSTOP) { 342 lwkt_gettoken(&lp->lwp_proc->p_token); 343 tstop(); 344 lwkt_reltoken(&lp->lwp_proc->p_token); 345 } 346 347 /* 348 * Reduce our priority in preparation for a return to userland. If 349 * our passive release function was still in place, our priority was 350 * never raised and does not need to be reduced. 351 */ 352 lwkt_passive_recover(td); 353 354 /* WARNING: we may have migrated cpu's */ 355 /* gd = td->td_gd; */ 356 357 /* 358 * Become the current user scheduled process if we aren't already, 359 * and deal with reschedule requests and other factors. 360 */ 361 lp->lwp_proc->p_usched->acquire_curproc(lp); 362 } 363 364 #if !defined(KTR_KERNENTRY) 365 #define KTR_KERNENTRY KTR_ALL 366 #endif 367 KTR_INFO_MASTER(kernentry); 368 KTR_INFO(KTR_KERNENTRY, kernentry, trap, 0, 369 "TRAP(pid %d, tid %d, trapno %ld, eva %lu)", 370 pid_t pid, lwpid_t tid, register_t trapno, vm_offset_t eva); 371 KTR_INFO(KTR_KERNENTRY, kernentry, trap_ret, 0, "TRAP_RET(pid %d, tid %d)", 372 pid_t pid, lwpid_t tid); 373 KTR_INFO(KTR_KERNENTRY, kernentry, syscall, 0, "SYSC(pid %d, tid %d, nr %ld)", 374 pid_t pid, lwpid_t tid, register_t trapno); 375 KTR_INFO(KTR_KERNENTRY, kernentry, syscall_ret, 0, "SYSRET(pid %d, tid %d, err %d)", 376 pid_t pid, lwpid_t tid, int err); 377 KTR_INFO(KTR_KERNENTRY, kernentry, fork_ret, 0, "FORKRET(pid %d, tid %d)", 378 pid_t pid, lwpid_t tid); 379 380 /* 381 * Exception, fault, and trap interface to the kernel. 382 * This common code is called from assembly language IDT gate entry 383 * routines that prepare a suitable stack frame, and restore this 384 * frame after the exception has been processed. 385 * 386 * This function is also called from doreti in an interlock to handle ASTs. 387 * For example: hardwareint->INTROUTINE->(set ast)->doreti->trap 388 * 389 * NOTE! We have to retrieve the fault address prior to obtaining the 390 * MP lock because get_mplock() may switch out. YYY cr2 really ought 391 * to be retrieved by the assembly code, not here. 392 * 393 * XXX gd_trap_nesting_level currently prevents lwkt_switch() from panicing 394 * if an attempt is made to switch from a fast interrupt or IPI. This is 395 * necessary to properly take fatal kernel traps on SMP machines if 396 * get_mplock() has to block. 397 */ 398 399 void 400 trap(struct trapframe *frame) 401 { 402 struct globaldata *gd = mycpu; 403 struct thread *td = gd->gd_curthread; 404 struct lwp *lp = td->td_lwp; 405 struct proc *p; 406 int sticks = 0; 407 int i = 0, ucode = 0, type, code; 408 #ifdef SMP 409 int have_mplock = 0; 410 #endif 411 #ifdef INVARIANTS 412 int crit_count = td->td_critcount; 413 lwkt_tokref_t curstop = td->td_toks_stop; 414 #endif 415 vm_offset_t eva; 416 417 p = td->td_proc; 418 clear_quickret(); 419 420 #ifdef DDB 421 /* 422 * We need to allow T_DNA faults when the debugger is active since 423 * some dumping paths do large bcopy() which use the floating 424 * point registers for faster copying. 425 */ 426 if (db_active && frame->tf_trapno != T_DNA) { 427 eva = (frame->tf_trapno == T_PAGEFLT ? frame->tf_addr : 0); 428 ++gd->gd_trap_nesting_level; 429 MAKEMPSAFE(have_mplock); 430 trap_fatal(frame, eva); 431 --gd->gd_trap_nesting_level; 432 goto out2; 433 } 434 #endif 435 436 eva = 0; 437 438 if ((frame->tf_rflags & PSL_I) == 0) { 439 /* 440 * Buggy application or kernel code has disabled interrupts 441 * and then trapped. Enabling interrupts now is wrong, but 442 * it is better than running with interrupts disabled until 443 * they are accidentally enabled later. 444 */ 445 type = frame->tf_trapno; 446 if (ISPL(frame->tf_cs) == SEL_UPL) { 447 MAKEMPSAFE(have_mplock); 448 /* JG curproc can be NULL */ 449 kprintf( 450 "pid %ld (%s): trap %d with interrupts disabled\n", 451 (long)curproc->p_pid, curproc->p_comm, type); 452 } else if (type != T_NMI && type != T_BPTFLT && 453 type != T_TRCTRAP) { 454 /* 455 * XXX not quite right, since this may be for a 456 * multiple fault in user mode. 457 */ 458 MAKEMPSAFE(have_mplock); 459 kprintf("kernel trap %d with interrupts disabled\n", 460 type); 461 } 462 cpu_enable_intr(); 463 } 464 465 type = frame->tf_trapno; 466 code = frame->tf_err; 467 468 if (ISPL(frame->tf_cs) == SEL_UPL) { 469 /* user trap */ 470 471 KTR_LOG(kernentry_trap, p->p_pid, lp->lwp_tid, 472 frame->tf_trapno, eva); 473 474 userenter(td, p); 475 476 sticks = (int)td->td_sticks; 477 KASSERT(lp->lwp_md.md_regs == frame, 478 ("Frame mismatch %p %p", lp->lwp_md.md_regs, frame)); 479 480 switch (type) { 481 case T_PRIVINFLT: /* privileged instruction fault */ 482 i = SIGILL; 483 ucode = ILL_PRVOPC; 484 break; 485 486 case T_BPTFLT: /* bpt instruction fault */ 487 case T_TRCTRAP: /* trace trap */ 488 frame->tf_rflags &= ~PSL_T; 489 i = SIGTRAP; 490 ucode = (type == T_TRCTRAP ? TRAP_TRACE : TRAP_BRKPT); 491 break; 492 493 case T_ARITHTRAP: /* arithmetic trap */ 494 ucode = code; 495 i = SIGFPE; 496 break; 497 498 case T_ASTFLT: /* Allow process switch */ 499 mycpu->gd_cnt.v_soft++; 500 if (mycpu->gd_reqflags & RQF_AST_OWEUPC) { 501 atomic_clear_int(&mycpu->gd_reqflags, 502 RQF_AST_OWEUPC); 503 addupc_task(p, p->p_prof.pr_addr, 504 p->p_prof.pr_ticks); 505 } 506 goto out; 507 508 case T_PROTFLT: /* general protection fault */ 509 i = SIGBUS; 510 ucode = BUS_OBJERR; 511 break; 512 case T_STKFLT: /* stack fault */ 513 case T_SEGNPFLT: /* segment not present fault */ 514 i = SIGBUS; 515 ucode = BUS_ADRERR; 516 break; 517 case T_TSSFLT: /* invalid TSS fault */ 518 case T_DOUBLEFLT: /* double fault */ 519 default: 520 i = SIGBUS; 521 ucode = BUS_OBJERR; 522 break; 523 524 case T_PAGEFLT: /* page fault */ 525 i = trap_pfault(frame, TRUE); 526 if (frame->tf_rip == 0) { 527 kprintf("T_PAGEFLT: Warning %%rip == 0!\n"); 528 #ifdef DDB 529 while (freeze_on_seg_fault) 530 tsleep(p, 0, "freeze", hz * 20); 531 #endif 532 } 533 if (i == -1 || i == 0) 534 goto out; 535 536 537 if (i == SIGSEGV) 538 ucode = SEGV_MAPERR; 539 else { 540 i = SIGSEGV; 541 ucode = SEGV_ACCERR; 542 } 543 break; 544 545 case T_DIVIDE: /* integer divide fault */ 546 ucode = FPE_INTDIV; 547 i = SIGFPE; 548 break; 549 550 #if NISA > 0 551 case T_NMI: 552 MAKEMPSAFE(have_mplock); 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 goto out; 608 i = SIGFPE; 609 ucode = FPE_FPU_NP_TRAP; 610 break; 611 612 case T_FPOPFLT: /* FPU operand fetch fault */ 613 ucode = ILL_COPROC; 614 i = SIGILL; 615 break; 616 617 case T_XMMFLT: /* SIMD floating-point exception */ 618 ucode = 0; /* XXX */ 619 i = SIGFPE; 620 break; 621 } 622 } else { 623 /* kernel trap */ 624 625 switch (type) { 626 case T_PAGEFLT: /* page fault */ 627 trap_pfault(frame, FALSE); 628 goto out2; 629 630 case T_DNA: 631 /* 632 * The kernel is apparently using fpu for copying. 633 * XXX this should be fatal unless the kernel has 634 * registered such use. 635 */ 636 if (npxdna()) 637 goto out2; 638 break; 639 640 case T_STKFLT: /* stack fault */ 641 break; 642 643 case T_PROTFLT: /* general protection fault */ 644 case T_SEGNPFLT: /* segment not present fault */ 645 /* 646 * Invalid segment selectors and out of bounds 647 * %rip's and %rsp's can be set up in user mode. 648 * This causes a fault in kernel mode when the 649 * kernel tries to return to user mode. We want 650 * to get this fault so that we can fix the 651 * problem here and not have to check all the 652 * selectors and pointers when the user changes 653 * them. 654 */ 655 if (mycpu->gd_intr_nesting_level == 0) { 656 /* 657 * NOTE: in 64-bit mode traps push rsp/ss 658 * even if no ring change occurs. 659 */ 660 if (td->td_pcb->pcb_onfault && 661 td->td_pcb->pcb_onfault_sp == 662 frame->tf_rsp) { 663 frame->tf_rip = (register_t) 664 td->td_pcb->pcb_onfault; 665 goto out2; 666 } 667 if (frame->tf_rip == (long)doreti_iret) { 668 frame->tf_rip = (long)doreti_iret_fault; 669 goto out2; 670 } 671 } 672 break; 673 674 case T_TSSFLT: 675 /* 676 * PSL_NT can be set in user mode and isn't cleared 677 * automatically when the kernel is entered. This 678 * causes a TSS fault when the kernel attempts to 679 * `iret' because the TSS link is uninitialized. We 680 * want to get this fault so that we can fix the 681 * problem here and not every time the kernel is 682 * entered. 683 */ 684 if (frame->tf_rflags & PSL_NT) { 685 frame->tf_rflags &= ~PSL_NT; 686 goto out2; 687 } 688 break; 689 690 case T_TRCTRAP: /* trace trap */ 691 #if 0 692 if (frame->tf_rip == (int)IDTVEC(syscall)) { 693 /* 694 * We've just entered system mode via the 695 * syscall lcall. Continue single stepping 696 * silently until the syscall handler has 697 * saved the flags. 698 */ 699 goto out2; 700 } 701 if (frame->tf_rip == (int)IDTVEC(syscall) + 1) { 702 /* 703 * The syscall handler has now saved the 704 * flags. Stop single stepping it. 705 */ 706 frame->tf_rflags &= ~PSL_T; 707 goto out2; 708 } 709 #endif 710 711 /* 712 * Ignore debug register trace traps due to 713 * accesses in the user's address space, which 714 * can happen under several conditions such as 715 * if a user sets a watchpoint on a buffer and 716 * then passes that buffer to a system call. 717 * We still want to get TRCTRAPS for addresses 718 * in kernel space because that is useful when 719 * debugging the kernel. 720 */ 721 #if JG 722 if (user_dbreg_trap()) { 723 /* 724 * Reset breakpoint bits because the 725 * processor doesn't 726 */ 727 /* XXX check upper bits here */ 728 load_dr6(rdr6() & 0xfffffff0); 729 goto out2; 730 } 731 #endif 732 /* 733 * FALLTHROUGH (TRCTRAP kernel mode, kernel address) 734 */ 735 case T_BPTFLT: 736 /* 737 * If DDB is enabled, let it handle the debugger trap. 738 * Otherwise, debugger traps "can't happen". 739 */ 740 ucode = TRAP_BRKPT; 741 #ifdef DDB 742 MAKEMPSAFE(have_mplock); 743 if (kdb_trap(type, 0, frame)) 744 goto out2; 745 #endif 746 break; 747 748 #if NISA > 0 749 case T_NMI: 750 MAKEMPSAFE(have_mplock); 751 /* machine/parity/power fail/"kitchen sink" faults */ 752 if (isa_nmi(code) == 0) { 753 #ifdef DDB 754 /* 755 * NMI can be hooked up to a pushbutton 756 * for debugging. 757 */ 758 if (ddb_on_nmi) { 759 kprintf ("NMI ... going to debugger\n"); 760 kdb_trap(type, 0, frame); 761 } 762 #endif /* DDB */ 763 goto out2; 764 } else if (panic_on_nmi == 0) 765 goto out2; 766 /* FALL THROUGH */ 767 #endif /* NISA > 0 */ 768 } 769 MAKEMPSAFE(have_mplock); 770 trap_fatal(frame, 0); 771 goto out2; 772 } 773 774 /* 775 * Virtual kernel intercept - if the fault is directly related to a 776 * VM context managed by a virtual kernel then let the virtual kernel 777 * handle it. 778 */ 779 if (lp->lwp_vkernel && lp->lwp_vkernel->ve) { 780 vkernel_trap(lp, frame); 781 goto out; 782 } 783 784 /* Translate fault for emulators (e.g. Linux) */ 785 if (*p->p_sysent->sv_transtrap) 786 i = (*p->p_sysent->sv_transtrap)(i, type); 787 788 MAKEMPSAFE(have_mplock); 789 trapsignal(lp, i, ucode); 790 791 #ifdef DEBUG 792 if (type <= MAX_TRAP_MSG) { 793 uprintf("fatal process exception: %s", 794 trap_msg[type]); 795 if ((type == T_PAGEFLT) || (type == T_PROTFLT)) 796 uprintf(", fault VA = 0x%lx", frame->tf_addr); 797 uprintf("\n"); 798 } 799 #endif 800 801 out: 802 userret(lp, frame, sticks); 803 userexit(lp); 804 out2: ; 805 #ifdef SMP 806 if (have_mplock) 807 rel_mplock(); 808 #endif 809 if (p != NULL && lp != NULL) 810 KTR_LOG(kernentry_trap_ret, p->p_pid, lp->lwp_tid); 811 #ifdef INVARIANTS 812 KASSERT(crit_count == td->td_critcount, 813 ("trap: critical section count mismatch! %d/%d", 814 crit_count, td->td_pri)); 815 KASSERT(curstop == td->td_toks_stop, 816 ("trap: extra tokens held after trap! %ld/%ld", 817 curstop - &td->td_toks_base, 818 td->td_toks_stop - &td->td_toks_base)); 819 #endif 820 } 821 822 static int 823 trap_pfault(struct trapframe *frame, int usermode) 824 { 825 vm_offset_t va; 826 struct vmspace *vm = NULL; 827 vm_map_t map; 828 int rv = 0; 829 int fault_flags; 830 vm_prot_t ftype; 831 thread_t td = curthread; 832 struct lwp *lp = td->td_lwp; 833 struct proc *p; 834 835 va = trunc_page(frame->tf_addr); 836 if (va >= VM_MIN_KERNEL_ADDRESS) { 837 /* 838 * Don't allow user-mode faults in kernel address space. 839 */ 840 if (usermode) { 841 fault_flags = -1; 842 ftype = -1; 843 goto nogo; 844 } 845 846 map = &kernel_map; 847 } else { 848 /* 849 * This is a fault on non-kernel virtual memory. 850 * vm is initialized above to NULL. If curproc is NULL 851 * or curproc->p_vmspace is NULL the fault is fatal. 852 */ 853 if (lp != NULL) 854 vm = lp->lwp_vmspace; 855 856 if (vm == NULL) { 857 fault_flags = -1; 858 ftype = -1; 859 goto nogo; 860 } 861 862 /* 863 * Debugging, try to catch kernel faults on the user address space when not inside 864 * on onfault (e.g. copyin/copyout) routine. 865 */ 866 if (usermode == 0 && (td->td_pcb == NULL || 867 td->td_pcb->pcb_onfault == NULL)) { 868 #ifdef DDB 869 if (freeze_on_seg_fault) { 870 kprintf("trap_pfault: user address fault from kernel mode " 871 "%016lx\n", (long)frame->tf_addr); 872 while (freeze_on_seg_fault) 873 tsleep(&freeze_on_seg_fault, 0, "frzseg", hz * 20); 874 } 875 #endif 876 } 877 map = &vm->vm_map; 878 } 879 880 /* 881 * PGEX_I is defined only if the execute disable bit capability is 882 * supported and enabled. 883 */ 884 if (frame->tf_err & PGEX_W) 885 ftype = VM_PROT_WRITE; 886 #if JG 887 else if ((frame->tf_err & PGEX_I) && pg_nx != 0) 888 ftype = VM_PROT_EXECUTE; 889 #endif 890 else 891 ftype = VM_PROT_READ; 892 893 if (map != &kernel_map) { 894 /* 895 * Keep swapout from messing with us during this 896 * critical time. 897 */ 898 PHOLD(lp->lwp_proc); 899 900 /* 901 * Issue fault 902 */ 903 fault_flags = 0; 904 if (usermode) 905 fault_flags |= VM_FAULT_BURST; 906 if (ftype & VM_PROT_WRITE) 907 fault_flags |= VM_FAULT_DIRTY; 908 else 909 fault_flags |= VM_FAULT_NORMAL; 910 rv = vm_fault(map, va, ftype, fault_flags); 911 912 PRELE(lp->lwp_proc); 913 } else { 914 /* 915 * Don't have to worry about process locking or stacks in the 916 * kernel. 917 */ 918 fault_flags = VM_FAULT_NORMAL; 919 rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL); 920 } 921 if (rv == KERN_SUCCESS) 922 return (0); 923 nogo: 924 if (!usermode) { 925 /* 926 * NOTE: in 64-bit mode traps push rsp/ss 927 * even if no ring change occurs. 928 */ 929 if (td->td_pcb->pcb_onfault && 930 td->td_pcb->pcb_onfault_sp == frame->tf_rsp && 931 td->td_gd->gd_intr_nesting_level == 0) { 932 frame->tf_rip = (register_t)td->td_pcb->pcb_onfault; 933 return (0); 934 } 935 trap_fatal(frame, frame->tf_addr); 936 return (-1); 937 } 938 939 /* 940 * NOTE: on x86_64 we have a tf_addr field in the trapframe, no 941 * kludge is needed to pass the fault address to signal handlers. 942 */ 943 p = td->td_proc; 944 if (td->td_lwp->lwp_vkernel == NULL) { 945 #ifdef DDB 946 if (bootverbose || freeze_on_seg_fault || ddb_on_seg_fault) { 947 #else 948 if (bootverbose) { 949 #endif 950 kprintf("seg-fault ft=%04x ff=%04x addr=%p rip=%p " 951 "pid=%d cpu=%d p_comm=%s\n", 952 ftype, fault_flags, 953 (void *)frame->tf_addr, 954 (void *)frame->tf_rip, 955 p->p_pid, mycpu->gd_cpuid, p->p_comm); 956 } 957 #ifdef DDB 958 while (freeze_on_seg_fault) { 959 tsleep(p, 0, "freeze", hz * 20); 960 } 961 if (ddb_on_seg_fault) 962 Debugger("ddb_on_seg_fault"); 963 #endif 964 } 965 966 return((rv == KERN_PROTECTION_FAILURE) ? SIGBUS : SIGSEGV); 967 } 968 969 static void 970 trap_fatal(struct trapframe *frame, vm_offset_t eva) 971 { 972 int code, ss; 973 u_int type; 974 long rsp; 975 struct soft_segment_descriptor softseg; 976 char *msg; 977 978 code = frame->tf_err; 979 type = frame->tf_trapno; 980 sdtossd(&gdt[IDXSEL(frame->tf_cs & 0xffff)], &softseg); 981 982 if (type <= MAX_TRAP_MSG) 983 msg = trap_msg[type]; 984 else 985 msg = "UNKNOWN"; 986 kprintf("\n\nFatal trap %d: %s while in %s mode\n", type, msg, 987 ISPL(frame->tf_cs) == SEL_UPL ? "user" : "kernel"); 988 #ifdef SMP 989 /* three separate prints in case of a trap on an unmapped page */ 990 kprintf("cpuid = %d; ", mycpu->gd_cpuid); 991 kprintf("lapic->id = %08x\n", lapic->id); 992 #endif 993 if (type == T_PAGEFLT) { 994 kprintf("fault virtual address = 0x%lx\n", eva); 995 kprintf("fault code = %s %s %s, %s\n", 996 code & PGEX_U ? "user" : "supervisor", 997 code & PGEX_W ? "write" : "read", 998 code & PGEX_I ? "instruction" : "data", 999 code & PGEX_P ? "protection violation" : "page not present"); 1000 } 1001 kprintf("instruction pointer = 0x%lx:0x%lx\n", 1002 frame->tf_cs & 0xffff, frame->tf_rip); 1003 if (ISPL(frame->tf_cs) == SEL_UPL) { 1004 ss = frame->tf_ss & 0xffff; 1005 rsp = frame->tf_rsp; 1006 } else { 1007 /* 1008 * NOTE: in 64-bit mode traps push rsp/ss even if no ring 1009 * change occurs. 1010 */ 1011 ss = GSEL(GDATA_SEL, SEL_KPL); 1012 rsp = frame->tf_rsp; 1013 } 1014 kprintf("stack pointer = 0x%x:0x%lx\n", ss, rsp); 1015 kprintf("frame pointer = 0x%x:0x%lx\n", ss, frame->tf_rbp); 1016 kprintf("code segment = base 0x%lx, limit 0x%lx, type 0x%x\n", 1017 softseg.ssd_base, softseg.ssd_limit, softseg.ssd_type); 1018 kprintf(" = DPL %d, pres %d, long %d, def32 %d, gran %d\n", 1019 softseg.ssd_dpl, softseg.ssd_p, softseg.ssd_long, softseg.ssd_def32, 1020 softseg.ssd_gran); 1021 kprintf("processor eflags = "); 1022 if (frame->tf_rflags & PSL_T) 1023 kprintf("trace trap, "); 1024 if (frame->tf_rflags & PSL_I) 1025 kprintf("interrupt enabled, "); 1026 if (frame->tf_rflags & PSL_NT) 1027 kprintf("nested task, "); 1028 if (frame->tf_rflags & PSL_RF) 1029 kprintf("resume, "); 1030 kprintf("IOPL = %ld\n", (frame->tf_rflags & PSL_IOPL) >> 12); 1031 kprintf("current process = "); 1032 if (curproc) { 1033 kprintf("%lu\n", 1034 (u_long)curproc->p_pid); 1035 } else { 1036 kprintf("Idle\n"); 1037 } 1038 kprintf("current thread = pri %d ", curthread->td_pri); 1039 if (curthread->td_critcount) 1040 kprintf("(CRIT)"); 1041 kprintf("\n"); 1042 1043 #ifdef DDB 1044 if ((debugger_on_panic || db_active) && kdb_trap(type, code, frame)) 1045 return; 1046 #endif 1047 kprintf("trap number = %d\n", type); 1048 if (type <= MAX_TRAP_MSG) 1049 panic("%s", trap_msg[type]); 1050 else 1051 panic("unknown/reserved trap"); 1052 } 1053 1054 /* 1055 * Double fault handler. Called when a fault occurs while writing 1056 * a frame for a trap/exception onto the stack. This usually occurs 1057 * when the stack overflows (such is the case with infinite recursion, 1058 * for example). 1059 */ 1060 static __inline 1061 int 1062 in_kstack_guard(register_t rptr) 1063 { 1064 thread_t td = curthread; 1065 1066 if ((char *)rptr >= td->td_kstack && 1067 (char *)rptr < td->td_kstack + PAGE_SIZE) { 1068 return 1; 1069 } 1070 return 0; 1071 } 1072 1073 void 1074 dblfault_handler(struct trapframe *frame) 1075 { 1076 thread_t td = curthread; 1077 1078 if (in_kstack_guard(frame->tf_rsp) || in_kstack_guard(frame->tf_rbp)) { 1079 kprintf("DOUBLE FAULT - KERNEL STACK GUARD HIT!\n"); 1080 if (in_kstack_guard(frame->tf_rsp)) 1081 frame->tf_rsp = (register_t)(td->td_kstack + PAGE_SIZE); 1082 if (in_kstack_guard(frame->tf_rbp)) 1083 frame->tf_rbp = (register_t)(td->td_kstack + PAGE_SIZE); 1084 } else { 1085 kprintf("DOUBLE FAULT\n"); 1086 } 1087 kprintf("\nFatal double fault\n"); 1088 kprintf("rip = 0x%lx\n", frame->tf_rip); 1089 kprintf("rsp = 0x%lx\n", frame->tf_rsp); 1090 kprintf("rbp = 0x%lx\n", frame->tf_rbp); 1091 #ifdef SMP 1092 /* three separate prints in case of a trap on an unmapped page */ 1093 kprintf("cpuid = %d; ", mycpu->gd_cpuid); 1094 kprintf("lapic->id = %08x\n", lapic->id); 1095 #endif 1096 panic("double fault"); 1097 } 1098 1099 /* 1100 * syscall2 - MP aware system call request C handler 1101 * 1102 * A system call is essentially treated as a trap except that the 1103 * MP lock is not held on entry or return. We are responsible for 1104 * obtaining the MP lock if necessary and for handling ASTs 1105 * (e.g. a task switch) prior to return. 1106 * 1107 * MPSAFE 1108 */ 1109 void 1110 syscall2(struct trapframe *frame) 1111 { 1112 struct thread *td = curthread; 1113 struct proc *p = td->td_proc; 1114 struct lwp *lp = td->td_lwp; 1115 caddr_t params; 1116 struct sysent *callp; 1117 register_t orig_tf_rflags; 1118 int sticks; 1119 int error; 1120 int narg; 1121 #ifdef INVARIANTS 1122 int crit_count = td->td_critcount; 1123 #endif 1124 #ifdef SMP 1125 int have_mplock = 0; 1126 #endif 1127 register_t *argp; 1128 u_int code; 1129 int reg, regcnt; 1130 union sysunion args; 1131 register_t *argsdst; 1132 1133 mycpu->gd_cnt.v_syscall++; 1134 1135 #ifdef DIAGNOSTIC 1136 if (ISPL(frame->tf_cs) != SEL_UPL) { 1137 get_mplock(); 1138 panic("syscall"); 1139 /* NOT REACHED */ 1140 } 1141 #endif 1142 1143 KTR_LOG(kernentry_syscall, p->p_pid, lp->lwp_tid, 1144 frame->tf_rax); 1145 1146 userenter(td, p); /* lazy raise our priority */ 1147 1148 reg = 0; 1149 regcnt = 6; 1150 /* 1151 * Misc 1152 */ 1153 sticks = (int)td->td_sticks; 1154 orig_tf_rflags = frame->tf_rflags; 1155 1156 /* 1157 * Virtual kernel intercept - if a VM context managed by a virtual 1158 * kernel issues a system call the virtual kernel handles it, not us. 1159 * Restore the virtual kernel context and return from its system 1160 * call. The current frame is copied out to the virtual kernel. 1161 */ 1162 if (lp->lwp_vkernel && lp->lwp_vkernel->ve) { 1163 vkernel_trap(lp, frame); 1164 error = EJUSTRETURN; 1165 goto out; 1166 } 1167 1168 /* 1169 * Get the system call parameters and account for time 1170 */ 1171 KASSERT(lp->lwp_md.md_regs == frame, 1172 ("Frame mismatch %p %p", lp->lwp_md.md_regs, frame)); 1173 params = (caddr_t)frame->tf_rsp + sizeof(register_t); 1174 code = frame->tf_rax; 1175 1176 if (p->p_sysent->sv_prepsyscall) { 1177 (*p->p_sysent->sv_prepsyscall)( 1178 frame, (int *)(&args.nosys.sysmsg + 1), 1179 &code, ¶ms); 1180 } else { 1181 if (code == SYS_syscall || code == SYS___syscall) { 1182 code = frame->tf_rdi; 1183 reg++; 1184 regcnt--; 1185 } 1186 } 1187 1188 if (p->p_sysent->sv_mask) 1189 code &= p->p_sysent->sv_mask; 1190 1191 if (code >= p->p_sysent->sv_size) 1192 callp = &p->p_sysent->sv_table[0]; 1193 else 1194 callp = &p->p_sysent->sv_table[code]; 1195 1196 narg = callp->sy_narg & SYF_ARGMASK; 1197 1198 /* 1199 * On x86_64 we get up to six arguments in registers. The rest are 1200 * on the stack. The first six members of 'struct trapframe' happen 1201 * to be the registers used to pass arguments, in exactly the right 1202 * order. 1203 */ 1204 argp = &frame->tf_rdi; 1205 argp += reg; 1206 argsdst = (register_t *)(&args.nosys.sysmsg + 1); 1207 /* 1208 * JG can we overflow the space pointed to by 'argsdst' 1209 * either with 'bcopy' or with 'copyin'? 1210 */ 1211 bcopy(argp, argsdst, sizeof(register_t) * regcnt); 1212 /* 1213 * copyin is MP aware, but the tracing code is not 1214 */ 1215 if (narg > regcnt) { 1216 KASSERT(params != NULL, ("copyin args with no params!")); 1217 error = copyin(params, &argsdst[regcnt], 1218 (narg - regcnt) * sizeof(register_t)); 1219 if (error) { 1220 #ifdef KTRACE 1221 if (KTRPOINT(td, KTR_SYSCALL)) { 1222 MAKEMPSAFE(have_mplock); 1223 1224 ktrsyscall(lp, code, narg, 1225 (void *)(&args.nosys.sysmsg + 1)); 1226 } 1227 #endif 1228 goto bad; 1229 } 1230 } 1231 1232 #ifdef KTRACE 1233 if (KTRPOINT(td, KTR_SYSCALL)) { 1234 MAKEMPSAFE(have_mplock); 1235 ktrsyscall(lp, code, narg, (void *)(&args.nosys.sysmsg + 1)); 1236 } 1237 #endif 1238 1239 /* 1240 * Default return value is 0 (will be copied to %rax). Double-value 1241 * returns use %rax and %rdx. %rdx is left unchanged for system 1242 * calls which return only one result. 1243 */ 1244 args.sysmsg_fds[0] = 0; 1245 args.sysmsg_fds[1] = frame->tf_rdx; 1246 1247 /* 1248 * The syscall might manipulate the trap frame. If it does it 1249 * will probably return EJUSTRETURN. 1250 */ 1251 args.sysmsg_frame = frame; 1252 1253 STOPEVENT(p, S_SCE, narg); /* MP aware */ 1254 1255 /* 1256 * NOTE: All system calls run MPSAFE now. The system call itself 1257 * is responsible for getting the MP lock. 1258 */ 1259 #ifdef SYSCALL_DEBUG 1260 uint64_t tscval = rdtsc(); 1261 #endif 1262 error = (*callp->sy_call)(&args); 1263 #ifdef SYSCALL_DEBUG 1264 tscval = rdtsc() - tscval; 1265 tscval = tscval * 1000000 / tsc_frequency; 1266 if (SysCallsWorstCase[code] < tscval) 1267 SysCallsWorstCase[code] = tscval; 1268 #endif 1269 1270 out: 1271 /* 1272 * MP SAFE (we may or may not have the MP lock at this point) 1273 */ 1274 //kprintf("SYSMSG %d ", error); 1275 switch (error) { 1276 case 0: 1277 /* 1278 * Reinitialize proc pointer `p' as it may be different 1279 * if this is a child returning from fork syscall. 1280 */ 1281 p = curproc; 1282 lp = curthread->td_lwp; 1283 frame->tf_rax = args.sysmsg_fds[0]; 1284 frame->tf_rdx = args.sysmsg_fds[1]; 1285 frame->tf_rflags &= ~PSL_C; 1286 break; 1287 case ERESTART: 1288 /* 1289 * Reconstruct pc, we know that 'syscall' is 2 bytes. 1290 * We have to do a full context restore so that %r10 1291 * (which was holding the value of %rcx) is restored for 1292 * the next iteration. 1293 */ 1294 if (frame->tf_err != 0 && frame->tf_err != 2) 1295 kprintf("lp %s:%d frame->tf_err is weird %ld\n", 1296 td->td_comm, lp->lwp_proc->p_pid, frame->tf_err); 1297 frame->tf_rip -= frame->tf_err; 1298 frame->tf_r10 = frame->tf_rcx; 1299 break; 1300 case EJUSTRETURN: 1301 break; 1302 case EASYNC: 1303 panic("Unexpected EASYNC return value (for now)"); 1304 default: 1305 bad: 1306 if (p->p_sysent->sv_errsize) { 1307 if (error >= p->p_sysent->sv_errsize) 1308 error = -1; /* XXX */ 1309 else 1310 error = p->p_sysent->sv_errtbl[error]; 1311 } 1312 frame->tf_rax = error; 1313 frame->tf_rflags |= PSL_C; 1314 break; 1315 } 1316 1317 /* 1318 * Traced syscall. trapsignal() is not MP aware. 1319 */ 1320 if (orig_tf_rflags & PSL_T) { 1321 MAKEMPSAFE(have_mplock); 1322 frame->tf_rflags &= ~PSL_T; 1323 trapsignal(lp, SIGTRAP, TRAP_TRACE); 1324 } 1325 1326 /* 1327 * Handle reschedule and other end-of-syscall issues 1328 */ 1329 userret(lp, frame, sticks); 1330 1331 #ifdef KTRACE 1332 if (KTRPOINT(td, KTR_SYSRET)) { 1333 MAKEMPSAFE(have_mplock); 1334 ktrsysret(lp, code, error, args.sysmsg_result); 1335 } 1336 #endif 1337 1338 /* 1339 * This works because errno is findable through the 1340 * register set. If we ever support an emulation where this 1341 * is not the case, this code will need to be revisited. 1342 */ 1343 STOPEVENT(p, S_SCX, code); 1344 1345 userexit(lp); 1346 #ifdef SMP 1347 /* 1348 * Release the MP lock if we had to get it 1349 */ 1350 if (have_mplock) 1351 rel_mplock(); 1352 #endif 1353 KTR_LOG(kernentry_syscall_ret, p->p_pid, lp->lwp_tid, error); 1354 #ifdef INVARIANTS 1355 KASSERT(crit_count == td->td_critcount, 1356 ("syscall: critical section count mismatch! %d/%d", 1357 crit_count, td->td_pri)); 1358 KASSERT(&td->td_toks_base == td->td_toks_stop, 1359 ("syscall: extra tokens held after trap! %ld", 1360 td->td_toks_stop - &td->td_toks_base)); 1361 #endif 1362 } 1363 1364 /* 1365 * NOTE: mplock not held at any point 1366 */ 1367 void 1368 fork_return(struct lwp *lp, struct trapframe *frame) 1369 { 1370 frame->tf_rax = 0; /* Child returns zero */ 1371 frame->tf_rflags &= ~PSL_C; /* success */ 1372 frame->tf_rdx = 1; 1373 1374 generic_lwp_return(lp, frame); 1375 KTR_LOG(kernentry_fork_ret, lp->lwp_proc->p_pid, lp->lwp_tid); 1376 } 1377 1378 /* 1379 * Simplified back end of syscall(), used when returning from fork() 1380 * directly into user mode. 1381 * 1382 * This code will return back into the fork trampoline code which then 1383 * runs doreti. 1384 * 1385 * NOTE: The mplock is not held at any point. 1386 */ 1387 void 1388 generic_lwp_return(struct lwp *lp, struct trapframe *frame) 1389 { 1390 struct proc *p = lp->lwp_proc; 1391 1392 /* 1393 * Newly forked processes are given a kernel priority. We have to 1394 * adjust the priority to a normal user priority and fake entry 1395 * into the kernel (call userenter()) to install a passive release 1396 * function just in case userret() decides to stop the process. This 1397 * can occur when ^Z races a fork. If we do not install the passive 1398 * release function the current process designation will not be 1399 * released when the thread goes to sleep. 1400 */ 1401 lwkt_setpri_self(TDPRI_USER_NORM); 1402 userenter(lp->lwp_thread, p); 1403 userret(lp, frame, 0); 1404 #ifdef KTRACE 1405 if (KTRPOINT(lp->lwp_thread, KTR_SYSRET)) 1406 ktrsysret(lp, SYS_fork, 0, 0); 1407 #endif 1408 lp->lwp_flags |= LWP_PASSIVE_ACQ; 1409 userexit(lp); 1410 lp->lwp_flags &= ~LWP_PASSIVE_ACQ; 1411 } 1412 1413 /* 1414 * If PGEX_FPFAULT is set then set FP_VIRTFP in the PCB to force a T_DNA 1415 * fault (which is then passed back to the virtual kernel) if an attempt is 1416 * made to use the FP unit. 1417 * 1418 * XXX this is a fairly big hack. 1419 */ 1420 void 1421 set_vkernel_fp(struct trapframe *frame) 1422 { 1423 struct thread *td = curthread; 1424 1425 if (frame->tf_xflags & PGEX_FPFAULT) { 1426 td->td_pcb->pcb_flags |= FP_VIRTFP; 1427 if (mdcpu->gd_npxthread == td) 1428 npxexit(); 1429 } else { 1430 td->td_pcb->pcb_flags &= ~FP_VIRTFP; 1431 } 1432 } 1433 1434 /* 1435 * Called from vkernel_trap() to fixup the vkernel's syscall 1436 * frame for vmspace_ctl() return. 1437 */ 1438 void 1439 cpu_vkernel_trap(struct trapframe *frame, int error) 1440 { 1441 frame->tf_rax = error; 1442 if (error) 1443 frame->tf_rflags |= PSL_C; 1444 else 1445 frame->tf_rflags &= ~PSL_C; 1446 } 1447