sys/amd64/amd64/trap.c

   1 /*-
   2  * Copyright (C) 1994, David Greenman
   3  * Copyright (c) 1990, 1993
   4  *      The Regents of the University of California.  All rights reserved.
   5  *
   6  * This code is derived from software contributed to Berkeley by
   7  * the University of Utah, and William Jolitz.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  * 3. All advertising materials mentioning features or use of this software
  18  *    must display the following acknowledgement:
  19  *      This product includes software developed by the University of
  20  *      California, Berkeley and its contributors.
  21  * 4. Neither the name of the University nor the names of its contributors
  22  *    may be used to endorse or promote products derived from this software
  23  *    without specific prior written permission.
  24  *
  25  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  27  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  29  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  31  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  32  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  33  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  34  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  35  * SUCH DAMAGE.
  36  *
  37  *      from: @(#)trap.c        7.4 (Berkeley) 5/13/91
  38  */
  39
  40 #include <sys/cdefs.h>
  41 __FBSDID("$FreeBSD$");
  42
  43 /*
  44  * AMD64 Trap and System call handling
  45  */
  46
  47 #include "opt_clock.h"
  48 #include "opt_cpu.h"
  49 #include "opt_hwpmc_hooks.h"
  50 #include "opt_isa.h"
  51 #include "opt_kdb.h"
  52 #include "opt_stack.h"
  53
  54 #include <sys/param.h>
  55 #include <sys/bus.h>
  56 #include <sys/systm.h>
  57 #include <sys/proc.h>
  58 #include <sys/pioctl.h>
  59 #include <sys/ptrace.h>
  60 #include <sys/kdb.h>
  61 #include <sys/kernel.h>
  62 #include <sys/ktr.h>
  63 #include <sys/lock.h>
  64 #include <sys/mutex.h>
  65 #include <sys/resourcevar.h>
  66 #include <sys/signalvar.h>
  67 #include <sys/syscall.h>
  68 #include <sys/sysctl.h>
  69 #include <sys/sysent.h>
  70 #include <sys/uio.h>
  71 #include <sys/vmmeter.h>
  72 #ifdef HWPMC_HOOKS
  73 #include <sys/pmckern.h>
  74 PMC_SOFT_DEFINE( , , page_fault, all);
  75 PMC_SOFT_DEFINE( , , page_fault, read);
  76 PMC_SOFT_DEFINE( , , page_fault, write);
  77 #endif
  78
  79 #include <vm/vm.h>
  80 #include <vm/vm_param.h>
  81 #include <vm/pmap.h>
  82 #include <vm/vm_kern.h>
  83 #include <vm/vm_map.h>
  84 #include <vm/vm_page.h>
  85 #include <vm/vm_extern.h>
  86
  87 #include <machine/cpu.h>
  88 #include <machine/intr_machdep.h>
  89 #include <x86/mca.h>
  90 #include <machine/md_var.h>
  91 #include <machine/pcb.h>
  92 #ifdef SMP
  93 #include <machine/smp.h>
  94 #endif
  95 #include <machine/stack.h>
  96 #include <machine/tss.h>
  97
  98 #ifdef KDTRACE_HOOKS
  99 #include <sys/dtrace_bsd.h>
 100 #endif
 101
 102 extern void __noinline trap(struct trapframe *frame);
 103 extern void trap_check(struct trapframe *frame);
 104 extern void syscall(struct trapframe *frame);
 105 void dblfault_handler(struct trapframe *frame);
 106
 107 static int trap_pfault(struct trapframe *, int);
 108 static void trap_fatal(struct trapframe *, vm_offset_t);
 109
 110 #define MAX_TRAP_MSG            32
 111 static char *trap_msg[] = {
 112         "",                                     /*  0 unused */
 113         "privileged instruction fault",         /*  1 T_PRIVINFLT */
 114         "",                                     /*  2 unused */
 115         "breakpoint instruction fault",         /*  3 T_BPTFLT */
 116         "",                                     /*  4 unused */
 117         "",                                     /*  5 unused */
 118         "arithmetic trap",                      /*  6 T_ARITHTRAP */
 119         "",                                     /*  7 unused */
 120         "",                                     /*  8 unused */
 121         "general protection fault",             /*  9 T_PROTFLT */
 122         "trace trap",                           /* 10 T_TRCTRAP */
 123         "",                                     /* 11 unused */
 124         "page fault",                           /* 12 T_PAGEFLT */
 125         "",                                     /* 13 unused */
 126         "alignment fault",                      /* 14 T_ALIGNFLT */
 127         "",                                     /* 15 unused */
 128         "",                                     /* 16 unused */
 129         "",                                     /* 17 unused */
 130         "integer divide fault",                 /* 18 T_DIVIDE */
 131         "non-maskable interrupt trap",          /* 19 T_NMI */
 132         "overflow trap",                        /* 20 T_OFLOW */
 133         "FPU bounds check fault",               /* 21 T_BOUND */
 134         "FPU device not available",             /* 22 T_DNA */
 135         "double fault",                         /* 23 T_DOUBLEFLT */
 136         "FPU operand fetch fault",              /* 24 T_FPOPFLT */
 137         "invalid TSS fault",                    /* 25 T_TSSFLT */
 138         "segment not present fault",            /* 26 T_SEGNPFLT */
 139         "stack fault",                          /* 27 T_STKFLT */
 140         "machine check trap",                   /* 28 T_MCHK */
 141         "SIMD floating-point exception",        /* 29 T_XMMFLT */
 142         "reserved (unknown) fault",             /* 30 T_RESERVED */
 143         "",                                     /* 31 unused (reserved) */
 144         "DTrace pid return trap",               /* 32 T_DTRACE_RET */
 145 };
 146
 147 static int prot_fault_translation;
 148 SYSCTL_INT(_machdep, OID_AUTO, prot_fault_translation, CTLFLAG_RWTUN,
 149     &prot_fault_translation, 0,
 150     "Select signal to deliver on protection fault");
 151 static int uprintf_signal;
 152 SYSCTL_INT(_machdep, OID_AUTO, uprintf_signal, CTLFLAG_RWTUN,
 153     &uprintf_signal, 0,
 154     "Print debugging information on trap signal to ctty");
 155
 156 /*
 157  * Exception, fault, and trap interface to the FreeBSD kernel.
 158  * This common code is called from assembly language IDT gate entry
 159  * routines that prepare a suitable stack frame, and restore this
 160  * frame after the exception has been processed.
 161  */
 162
 163 void
 164 trap(struct trapframe *frame)
 165 {
 166 #ifdef KDTRACE_HOOKS
 167         struct reg regs;
 168 #endif
 169         struct thread *td = curthread;
 170         struct proc *p = td->td_proc;
 171 #ifdef KDB
 172         register_t dr6;
 173 #endif
 174         int i = 0, ucode = 0;
 175         u_int type;
 176         register_t addr = 0;
 177         ksiginfo_t ksi;
 178
 179         PCPU_INC(cnt.v_trap);
 180         type = frame->tf_trapno;
 181
 182 #ifdef SMP
 183         /* Handler for NMI IPIs used for stopping CPUs. */
 184         if (type == T_NMI) {
 185                  if (ipi_nmi_handler() == 0)
 186                            goto out;
 187         }
 188 #endif /* SMP */
 189
 190 #ifdef KDB
 191         if (kdb_active) {
 192                 kdb_reenter();
 193                 goto out;
 194         }
 195 #endif
 196
 197         if (type == T_RESERVED) {
 198                 trap_fatal(frame, 0);
 199                 goto out;
 200         }
 201
 202         if (type == T_NMI) {
 203 #ifdef HWPMC_HOOKS
 204                 /*
 205                  * CPU PMCs interrupt using an NMI.  If the PMC module is
 206                  * active, pass the 'rip' value to the PMC module's interrupt
 207                  * handler.  A non-zero return value from the handler means that
 208                  * the NMI was consumed by it and we can return immediately.
 209                  */
 210                 if (pmc_intr != NULL &&
 211                     (*pmc_intr)(PCPU_GET(cpuid), frame) != 0)
 212                         goto out;
 213 #endif
 214
 215 #ifdef STACK
 216                 if (stack_nmi_handler(frame) != 0)
 217                         goto out;
 218 #endif
 219         }
 220
 221         if (type == T_MCHK) {
 222                 mca_intr();
 223                 goto out;
 224         }
 225
 226         if ((frame->tf_rflags & PSL_I) == 0) {
 227                 /*
 228                  * Buggy application or kernel code has disabled
 229                  * interrupts and then trapped.  Enabling interrupts
 230                  * now is wrong, but it is better than running with
 231                  * interrupts disabled until they are accidentally
 232                  * enabled later.
 233                  */
 234                 if (TRAPF_USERMODE(frame))
 235                         uprintf(
 236                             "pid %ld (%s): trap %d with interrupts disabled\n",
 237                             (long)curproc->p_pid, curthread->td_name, type);
 238                 else if (type != T_NMI && type != T_BPTFLT &&
 239                     type != T_TRCTRAP) {
 240                         /*
 241                          * XXX not quite right, since this may be for a
 242                          * multiple fault in user mode.
 243                          */
 244                         printf("kernel trap %d with interrupts disabled\n",
 245                             type);
 246
 247                         /*
 248                          * We shouldn't enable interrupts while holding a
 249                          * spin lock.
 250                          */
 251                         if (td->td_md.md_spinlock_count == 0)
 252                                 enable_intr();
 253                 }
 254         }
 255
 256         if (TRAPF_USERMODE(frame)) {
 257                 /* user trap */
 258
 259                 td->td_pticks = 0;
 260                 td->td_frame = frame;
 261                 addr = frame->tf_rip;
 262                 if (td->td_cowgen != p->p_cowgen)
 263                         thread_cow_update(td);
 264
 265                 switch (type) {
 266                 case T_PRIVINFLT:       /* privileged instruction fault */
 267                         i = SIGILL;
 268                         ucode = ILL_PRVOPC;
 269                         break;
 270
 271                 case T_BPTFLT:          /* bpt instruction fault */
 272                 case T_TRCTRAP:         /* trace trap */
 273                         enable_intr();
 274 #ifdef KDTRACE_HOOKS
 275                         if (type == T_BPTFLT) {
 276                                 fill_frame_regs(frame, &regs);
 277                                 if (dtrace_pid_probe_ptr != NULL &&
 278                                     dtrace_pid_probe_ptr(&regs) == 0)
 279                                         goto out;
 280                         }
 281 #endif
 282                         frame->tf_rflags &= ~PSL_T;
 283                         i = SIGTRAP;
 284                         ucode = (type == T_TRCTRAP ? TRAP_TRACE : TRAP_BRKPT);
 285                         break;
 286
 287                 case T_ARITHTRAP:       /* arithmetic trap */
 288                         ucode = fputrap_x87();
 289                         if (ucode == -1)
 290                                 goto userout;
 291                         i = SIGFPE;
 292                         break;
 293
 294                 case T_PROTFLT:         /* general protection fault */
 295                         i = SIGBUS;
 296                         ucode = BUS_OBJERR;
 297                         break;
 298                 case T_STKFLT:          /* stack fault */
 299                 case T_SEGNPFLT:        /* segment not present fault */
 300                         i = SIGBUS;
 301                         ucode = BUS_ADRERR;
 302                         break;
 303                 case T_TSSFLT:          /* invalid TSS fault */
 304                         i = SIGBUS;
 305                         ucode = BUS_OBJERR;
 306                         break;
 307                 case T_ALIGNFLT:
 308                         i = SIGBUS;
 309                         ucode = BUS_ADRALN;
 310                         break;
 311                 case T_DOUBLEFLT:       /* double fault */
 312                 default:
 313                         i = SIGBUS;
 314                         ucode = BUS_OBJERR;
 315                         break;
 316
 317                 case T_PAGEFLT:         /* page fault */
 318                         /*
 319                          * Emulator can take care about this trap?
 320                          */
 321                         if (*p->p_sysent->sv_trap != NULL &&
 322                             (*p->p_sysent->sv_trap)(td) == 0)
 323                                 goto userout;
 324
 325                         addr = frame->tf_addr;
 326                         i = trap_pfault(frame, TRUE);
 327                         if (i == -1)
 328                                 goto userout;
 329                         if (i == 0)
 330                                 goto user;
 331
 332                         if (i == SIGSEGV)
 333                                 ucode = SEGV_MAPERR;
 334                         else {
 335                                 if (prot_fault_translation == 0) {
 336                                         /*
 337                                          * Autodetect.
 338                                          * This check also covers the images
 339                                          * without the ABI-tag ELF note.
 340                                          */
 341                                         if (SV_CURPROC_ABI() == SV_ABI_FREEBSD
 342                                             && p->p_osrel >= P_OSREL_SIGSEGV) {
 343                                                 i = SIGSEGV;
 344                                                 ucode = SEGV_ACCERR;
 345                                         } else {
 346                                                 i = SIGBUS;
 347                                                 ucode = BUS_PAGE_FAULT;
 348                                         }
 349                                 } else if (prot_fault_translation == 1) {
 350                                         /*
 351                                          * Always compat mode.
 352                                          */
 353                                         i = SIGBUS;
 354                                         ucode = BUS_PAGE_FAULT;
 355                                 } else {
 356                                         /*
 357                                          * Always SIGSEGV mode.
 358                                          */
 359                                         i = SIGSEGV;
 360                                         ucode = SEGV_ACCERR;
 361                                 }
 362                         }
 363                         break;
 364
 365                 case T_DIVIDE:          /* integer divide fault */
 366                         ucode = FPE_INTDIV;
 367                         i = SIGFPE;
 368                         break;
 369
 370 #ifdef DEV_ISA
 371                 case T_NMI:
 372                         nmi_handle_intr(type, frame);
 373                         break;
 374 #endif /* DEV_ISA */
 375
 376                 case T_OFLOW:           /* integer overflow fault */
 377                         ucode = FPE_INTOVF;
 378                         i = SIGFPE;
 379                         break;
 380
 381                 case T_BOUND:           /* bounds check fault */
 382                         ucode = FPE_FLTSUB;
 383                         i = SIGFPE;
 384                         break;
 385
 386                 case T_DNA:
 387                         /* transparent fault (due to context switch "late") */
 388                         KASSERT(PCB_USER_FPU(td->td_pcb),
 389                             ("kernel FPU ctx has leaked"));
 390                         fpudna();
 391                         goto userout;
 392
 393                 case T_FPOPFLT:         /* FPU operand fetch fault */
 394                         ucode = ILL_COPROC;
 395                         i = SIGILL;
 396                         break;
 397
 398                 case T_XMMFLT:          /* SIMD floating-point exception */
 399                         ucode = fputrap_sse();
 400                         if (ucode == -1)
 401                                 goto userout;
 402                         i = SIGFPE;
 403                         break;
 404 #ifdef KDTRACE_HOOKS
 405                 case T_DTRACE_RET:
 406                         enable_intr();
 407                         fill_frame_regs(frame, &regs);
 408                         if (dtrace_return_probe_ptr != NULL &&
 409                             dtrace_return_probe_ptr(&regs) == 0)
 410                                 goto out;
 411                         break;
 412 #endif
 413                 }
 414         } else {
 415                 /* kernel trap */
 416
 417                 KASSERT(cold || td->td_ucred != NULL,
 418                     ("kernel trap doesn't have ucred"));
 419                 switch (type) {
 420                 case T_PAGEFLT:                 /* page fault */
 421                         (void) trap_pfault(frame, FALSE);
 422                         goto out;
 423
 424                 case T_DNA:
 425                         if (PCB_USER_FPU(td->td_pcb))
 426                                 panic("Unregistered use of FPU in kernel");
 427                         fpudna();
 428                         goto out;
 429
 430                 case T_ARITHTRAP:       /* arithmetic trap */
 431                 case T_XMMFLT:          /* SIMD floating-point exception */
 432                 case T_FPOPFLT:         /* FPU operand fetch fault */
 433                         /*
 434                          * For now, supporting kernel handler
 435                          * registration for FPU traps is overkill.
 436                          */
 437                         trap_fatal(frame, 0);
 438                         goto out;
 439
 440                 case T_STKFLT:          /* stack fault */
 441                 case T_PROTFLT:         /* general protection fault */
 442                 case T_SEGNPFLT:        /* segment not present fault */
 443                         if (td->td_intr_nesting_level != 0)
 444                                 break;
 445
 446                         /*
 447                          * Invalid segment selectors and out of bounds
 448                          * %rip's and %rsp's can be set up in user mode.
 449                          * This causes a fault in kernel mode when the
 450                          * kernel tries to return to user mode.  We want
 451                          * to get this fault so that we can fix the
 452                          * problem here and not have to check all the
 453                          * selectors and pointers when the user changes
 454                          * them.
 455                          */
 456                         if (frame->tf_rip == (long)doreti_iret) {
 457                                 frame->tf_rip = (long)doreti_iret_fault;
 458                                 goto out;
 459                         }
 460                         if (frame->tf_rip == (long)ld_ds) {
 461                                 frame->tf_rip = (long)ds_load_fault;
 462                                 goto out;
 463                         }
 464                         if (frame->tf_rip == (long)ld_es) {
 465                                 frame->tf_rip = (long)es_load_fault;
 466                                 goto out;
 467                         }
 468                         if (frame->tf_rip == (long)ld_fs) {
 469                                 frame->tf_rip = (long)fs_load_fault;
 470                                 goto out;
 471                         }
 472                         if (frame->tf_rip == (long)ld_gs) {
 473                                 frame->tf_rip = (long)gs_load_fault;
 474                                 goto out;
 475                         }
 476                         if (frame->tf_rip == (long)ld_gsbase) {
 477                                 frame->tf_rip = (long)gsbase_load_fault;
 478                                 goto out;
 479                         }
 480                         if (frame->tf_rip == (long)ld_fsbase) {
 481                                 frame->tf_rip = (long)fsbase_load_fault;
 482                                 goto out;
 483                         }
 484                         if (curpcb->pcb_onfault != NULL) {
 485                                 frame->tf_rip = (long)curpcb->pcb_onfault;
 486                                 goto out;
 487                         }
 488                         break;
 489
 490                 case T_TSSFLT:
 491                         /*
 492                          * PSL_NT can be set in user mode and isn't cleared
 493                          * automatically when the kernel is entered.  This
 494                          * causes a TSS fault when the kernel attempts to
 495                          * `iret' because the TSS link is uninitialized.  We
 496                          * want to get this fault so that we can fix the
 497                          * problem here and not every time the kernel is
 498                          * entered.
 499                          */
 500                         if (frame->tf_rflags & PSL_NT) {
 501                                 frame->tf_rflags &= ~PSL_NT;
 502                                 goto out;
 503                         }
 504                         break;
 505
 506                 case T_TRCTRAP:  /* trace trap */
 507                         /*
 508                          * Ignore debug register trace traps due to
 509                          * accesses in the user's address space, which
 510                          * can happen under several conditions such as
 511                          * if a user sets a watchpoint on a buffer and
 512                          * then passes that buffer to a system call.
 513                          * We still want to get TRCTRAPS for addresses
 514                          * in kernel space because that is useful when
 515                          * debugging the kernel.
 516                          */
 517                         if (user_dbreg_trap()) {
 518                                 /*
 519                                  * Reset breakpoint bits because the
 520                                  * processor doesn't
 521                                  */
 522                                 load_dr6(rdr6() & ~0xf);
 523                                 goto out;
 524                         }
 525                         /*
 526                          * FALLTHROUGH (TRCTRAP kernel mode, kernel address)
 527                          */
 528                 case T_BPTFLT:
 529                         /*
 530                          * If KDB is enabled, let it handle the debugger trap.
 531                          * Otherwise, debugger traps "can't happen".
 532                          */
 533 #ifdef KDB
 534                         /* XXX %dr6 is not quite reentrant. */
 535                         dr6 = rdr6();
 536                         load_dr6(dr6 & ~0x4000);
 537                         if (kdb_trap(type, dr6, frame))
 538                                 goto out;
 539 #endif
 540                         break;
 541
 542 #ifdef DEV_ISA
 543                 case T_NMI:
 544                         nmi_handle_intr(type, frame);
 545                         goto out;
 546 #endif /* DEV_ISA */
 547                 }
 548
 549                 trap_fatal(frame, 0);
 550                 goto out;
 551         }
 552
 553         /* Translate fault for emulators (e.g. Linux) */
 554         if (*p->p_sysent->sv_transtrap)
 555                 i = (*p->p_sysent->sv_transtrap)(i, type);
 556
 557         ksiginfo_init_trap(&ksi);
 558         ksi.ksi_signo = i;
 559         ksi.ksi_code = ucode;
 560         ksi.ksi_trapno = type;
 561         ksi.ksi_addr = (void *)addr;
 562         if (uprintf_signal) {
 563                 uprintf("pid %d comm %s: signal %d err %lx code %d type %d "
 564                     "addr 0x%lx rsp 0x%lx rip 0x%lx "
 565                     "<%02x %02x %02x %02x %02x %02x %02x %02x>\n",
 566                     p->p_pid, p->p_comm, i, frame->tf_err, ucode, type, addr,
 567                     frame->tf_rsp, frame->tf_rip,
 568                     fubyte((void *)(frame->tf_rip + 0)),
 569                     fubyte((void *)(frame->tf_rip + 1)),
 570                     fubyte((void *)(frame->tf_rip + 2)),
 571                     fubyte((void *)(frame->tf_rip + 3)),
 572                     fubyte((void *)(frame->tf_rip + 4)),
 573                     fubyte((void *)(frame->tf_rip + 5)),
 574                     fubyte((void *)(frame->tf_rip + 6)),
 575                     fubyte((void *)(frame->tf_rip + 7)));
 576         }
 577         KASSERT((read_rflags() & PSL_I) != 0, ("interrupts disabled"));
 578         trapsignal(td, &ksi);
 579
 580 user:
 581         userret(td, frame);
 582         KASSERT(PCB_USER_FPU(td->td_pcb),
 583             ("Return from trap with kernel FPU ctx leaked"));
 584 userout:
 585 out:
 586         return;
 587 }
 588
 589 /*
 590  * Ensure that we ignore any DTrace-induced faults. This function cannot
 591  * be instrumented, so it cannot generate such faults itself.
 592  */
 593 void
 594 trap_check(struct trapframe *frame)
 595 {
 596
 597 #ifdef KDTRACE_HOOKS
 598         if (dtrace_trap_func != NULL &&
 599             (*dtrace_trap_func)(frame, frame->tf_trapno) != 0)
 600                 return;
 601 #endif
 602         trap(frame);
 603 }
 604
 605 static int
 606 trap_pfault(frame, usermode)
 607         struct trapframe *frame;
 608         int usermode;
 609 {
 610         vm_offset_t va;
 611         vm_map_t map;
 612         int rv = 0;
 613         vm_prot_t ftype;
 614         struct thread *td = curthread;
 615         struct proc *p = td->td_proc;
 616         vm_offset_t eva = frame->tf_addr;
 617
 618         if (__predict_false((td->td_pflags & TDP_NOFAULTING) != 0)) {
 619                 /*
 620                  * Due to both processor errata and lazy TLB invalidation when
 621                  * access restrictions are removed from virtual pages, memory
 622                  * accesses that are allowed by the physical mapping layer may
 623                  * nonetheless cause one spurious page fault per virtual page.
 624                  * When the thread is executing a "no faulting" section that
 625                  * is bracketed by vm_fault_{disable,enable}_pagefaults(),
 626                  * every page fault is treated as a spurious page fault,
 627                  * unless it accesses the same virtual address as the most
 628                  * recent page fault within the same "no faulting" section.
 629                  */
 630                 if (td->td_md.md_spurflt_addr != eva ||
 631                     (td->td_pflags & TDP_RESETSPUR) != 0) {
 632                         /*
 633                          * Do nothing to the TLB.  A stale TLB entry is
 634                          * flushed automatically by a page fault.
 635                          */
 636                         td->td_md.md_spurflt_addr = eva;
 637                         td->td_pflags &= ~TDP_RESETSPUR;
 638                         return (0);
 639                 }
 640         } else {
 641                 /*
 642                  * If we get a page fault while in a critical section, then
 643                  * it is most likely a fatal kernel page fault.  The kernel
 644                  * is already going to panic trying to get a sleep lock to
 645                  * do the VM lookup, so just consider it a fatal trap so the
 646                  * kernel can print out a useful trap message and even get
 647                  * to the debugger.
 648                  *
 649                  * If we get a page fault while holding a non-sleepable
 650                  * lock, then it is most likely a fatal kernel page fault.
 651                  * If WITNESS is enabled, then it's going to whine about
 652                  * bogus LORs with various VM locks, so just skip to the
 653                  * fatal trap handling directly.
 654                  */
 655                 if (td->td_critnest != 0 ||
 656                     WITNESS_CHECK(WARN_SLEEPOK | WARN_GIANTOK, NULL,
 657                     "Kernel page fault") != 0) {
 658                         trap_fatal(frame, eva);
 659                         return (-1);
 660                 }
 661         }
 662         va = trunc_page(eva);
 663         if (va >= VM_MIN_KERNEL_ADDRESS) {
 664                 /*
 665                  * Don't allow user-mode faults in kernel address space.
 666                  */
 667                 if (usermode)
 668                         goto nogo;
 669
 670                 map = kernel_map;
 671         } else {
 672                 map = &p->p_vmspace->vm_map;
 673
 674                 /*
 675                  * When accessing a usermode address, kernel must be
 676                  * ready to accept the page fault, and provide a
 677                  * handling routine.  Since accessing the address
 678                  * without the handler is a bug, do not try to handle
 679                  * it normally, and panic immediately.
 680                  */
 681                 if (!usermode && (td->td_intr_nesting_level != 0 ||
 682                     curpcb->pcb_onfault == NULL)) {
 683                         trap_fatal(frame, eva);
 684                         return (-1);
 685                 }
 686         }
 687
 688         /*
 689          * If the trap was caused by errant bits in the PTE then panic.
 690          */
 691         if (frame->tf_err & PGEX_RSV) {
 692                 trap_fatal(frame, eva);
 693                 return (-1);
 694         }
 695
 696         /*
 697          * PGEX_I is defined only if the execute disable bit capability is
 698          * supported and enabled.
 699          */
 700         if (frame->tf_err & PGEX_W)
 701                 ftype = VM_PROT_WRITE;
 702         else if ((frame->tf_err & PGEX_I) && pg_nx != 0)
 703                 ftype = VM_PROT_EXECUTE;
 704         else
 705                 ftype = VM_PROT_READ;
 706
 707         /* Fault in the page. */
 708         rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
 709         if (rv == KERN_SUCCESS) {
 710 #ifdef HWPMC_HOOKS
 711                 if (ftype == VM_PROT_READ || ftype == VM_PROT_WRITE) {
 712                         PMC_SOFT_CALL_TF( , , page_fault, all, frame);
 713                         if (ftype == VM_PROT_READ)
 714                                 PMC_SOFT_CALL_TF( , , page_fault, read,
 715                                     frame);
 716                         else
 717                                 PMC_SOFT_CALL_TF( , , page_fault, write,
 718                                     frame);
 719                 }
 720 #endif
 721                 return (0);
 722         }
 723 nogo:
 724         if (!usermode) {
 725                 if (td->td_intr_nesting_level == 0 &&
 726                     curpcb->pcb_onfault != NULL) {
 727                         frame->tf_rip = (long)curpcb->pcb_onfault;
 728                         return (0);
 729                 }
 730                 trap_fatal(frame, eva);
 731                 return (-1);
 732         }
 733         return ((rv == KERN_PROTECTION_FAILURE) ? SIGBUS : SIGSEGV);
 734 }
 735
 736 static void
 737 trap_fatal(frame, eva)
 738         struct trapframe *frame;
 739         vm_offset_t eva;
 740 {
 741         int code, ss;
 742         u_int type;
 743         struct soft_segment_descriptor softseg;
 744         char *msg;
 745
 746         code = frame->tf_err;
 747         type = frame->tf_trapno;
 748         sdtossd(&gdt[NGDT * PCPU_GET(cpuid) + IDXSEL(frame->tf_cs & 0xffff)],
 749             &softseg);
 750
 751         if (type <= MAX_TRAP_MSG)
 752                 msg = trap_msg[type];
 753         else
 754                 msg = "UNKNOWN";
 755         printf("\n\nFatal trap %d: %s while in %s mode\n", type, msg,
 756             TRAPF_USERMODE(frame) ? "user" : "kernel");
 757 #ifdef SMP
 758         /* two separate prints in case of a trap on an unmapped page */
 759         printf("cpuid = %d; ", PCPU_GET(cpuid));
 760         printf("apic id = %02x\n", PCPU_GET(apic_id));
 761 #endif
 762         if (type == T_PAGEFLT) {
 763                 printf("fault virtual address   = 0x%lx\n", eva);
 764                 printf("fault code              = %s %s %s%s, %s\n",
 765                         code & PGEX_U ? "user" : "supervisor",
 766                         code & PGEX_W ? "write" : "read",
 767                         code & PGEX_I ? "instruction" : "data",
 768                         code & PGEX_RSV ? " rsv" : "",
 769                         code & PGEX_P ? "protection violation" : "page not present");
 770         }
 771         printf("instruction pointer     = 0x%lx:0x%lx\n",
 772                frame->tf_cs & 0xffff, frame->tf_rip);
 773         ss = frame->tf_ss & 0xffff;
 774         printf("stack pointer           = 0x%x:0x%lx\n", ss, frame->tf_rsp);
 775         printf("frame pointer           = 0x%x:0x%lx\n", ss, frame->tf_rbp);
 776         printf("code segment            = base 0x%lx, limit 0x%lx, type 0x%x\n",
 777                softseg.ssd_base, softseg.ssd_limit, softseg.ssd_type);
 778         printf("                        = DPL %d, pres %d, long %d, def32 %d, gran %d\n",
 779                softseg.ssd_dpl, softseg.ssd_p, softseg.ssd_long, softseg.ssd_def32,
 780                softseg.ssd_gran);
 781         printf("processor eflags        = ");
 782         if (frame->tf_rflags & PSL_T)
 783                 printf("trace trap, ");
 784         if (frame->tf_rflags & PSL_I)
 785                 printf("interrupt enabled, ");
 786         if (frame->tf_rflags & PSL_NT)
 787                 printf("nested task, ");
 788         if (frame->tf_rflags & PSL_RF)
 789                 printf("resume, ");
 790         printf("IOPL = %ld\n", (frame->tf_rflags & PSL_IOPL) >> 12);
 791         printf("current process         = %d (%s)\n",
 792             curproc->p_pid, curthread->td_name);
 793
 794 #ifdef KDB
 795         if (debugger_on_panic || kdb_active)
 796                 if (kdb_trap(type, 0, frame))
 797                         return;
 798 #endif
 799         printf("trap number             = %d\n", type);
 800         if (type <= MAX_TRAP_MSG)
 801                 panic("%s", trap_msg[type]);
 802         else
 803                 panic("unknown/reserved trap");
 804 }
 805
 806 /*
 807  * Double fault handler. Called when a fault occurs while writing
 808  * a frame for a trap/exception onto the stack. This usually occurs
 809  * when the stack overflows (such is the case with infinite recursion,
 810  * for example).
 811  */
 812 void
 813 dblfault_handler(struct trapframe *frame)
 814 {
 815 #ifdef KDTRACE_HOOKS
 816         if (dtrace_doubletrap_func != NULL)
 817                 (*dtrace_doubletrap_func)();
 818 #endif
 819         printf("\nFatal double fault\n");
 820         printf("rip = 0x%lx\n", frame->tf_rip);
 821         printf("rsp = 0x%lx\n", frame->tf_rsp);
 822         printf("rbp = 0x%lx\n", frame->tf_rbp);
 823 #ifdef SMP
 824         /* two separate prints in case of a trap on an unmapped page */
 825         printf("cpuid = %d; ", PCPU_GET(cpuid));
 826         printf("apic id = %02x\n", PCPU_GET(apic_id));
 827 #endif
 828         panic("double fault");
 829 }
 830
 831 int
 832 cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
 833 {
 834         struct proc *p;
 835         struct trapframe *frame;
 836         register_t *argp;
 837         caddr_t params;
 838         int reg, regcnt, error;
 839
 840         p = td->td_proc;
 841         frame = td->td_frame;
 842         reg = 0;
 843         regcnt = 6;
 844
 845         params = (caddr_t)frame->tf_rsp + sizeof(register_t);
 846         sa->code = frame->tf_rax;
 847
 848         if (sa->code == SYS_syscall || sa->code == SYS___syscall) {
 849                 sa->code = frame->tf_rdi;
 850                 reg++;
 851                 regcnt--;
 852         }
 853         if (p->p_sysent->sv_mask)
 854                 sa->code &= p->p_sysent->sv_mask;
 855
 856         if (sa->code >= p->p_sysent->sv_size)
 857                 sa->callp = &p->p_sysent->sv_table[0];
 858         else
 859                 sa->callp = &p->p_sysent->sv_table[sa->code];
 860
 861         sa->narg = sa->callp->sy_narg;
 862         KASSERT(sa->narg <= sizeof(sa->args) / sizeof(sa->args[0]),
 863             ("Too many syscall arguments!"));
 864         error = 0;
 865         argp = &frame->tf_rdi;
 866         argp += reg;
 867         bcopy(argp, sa->args, sizeof(sa->args[0]) * regcnt);
 868         if (sa->narg > regcnt) {
 869                 KASSERT(params != NULL, ("copyin args with no params!"));
 870                 error = copyin(params, &sa->args[regcnt],
 871                     (sa->narg - regcnt) * sizeof(sa->args[0]));
 872         }
 873
 874         if (error == 0) {
 875                 td->td_retval[0] = 0;
 876                 td->td_retval[1] = frame->tf_rdx;
 877         }
 878
 879         return (error);
 880 }
 881
 882 #include "../../kern/subr_syscall.c"
 883
 884 /*
 885  * System call handler for native binaries.  The trap frame is already
 886  * set up by the assembler trampoline and a pointer to it is saved in
 887  * td_frame.
 888  */
 889 void
 890 amd64_syscall(struct thread *td, int traced)
 891 {
 892         struct syscall_args sa;
 893         int error;
 894         ksiginfo_t ksi;
 895
 896 #ifdef DIAGNOSTIC
 897         if (!TRAPF_USERMODE(td->td_frame)) {
 898                 panic("syscall");
 899                 /* NOT REACHED */
 900         }
 901 #endif
 902         error = syscallenter(td, &sa);
 903
 904         /*
 905          * Traced syscall.
 906          */
 907         if (__predict_false(traced)) {
 908                 td->td_frame->tf_rflags &= ~PSL_T;
 909                 ksiginfo_init_trap(&ksi);
 910                 ksi.ksi_signo = SIGTRAP;
 911                 ksi.ksi_code = TRAP_TRACE;
 912                 ksi.ksi_addr = (void *)td->td_frame->tf_rip;
 913                 trapsignal(td, &ksi);
 914         }
 915
 916         KASSERT(PCB_USER_FPU(td->td_pcb),
 917             ("System call %s returning with kernel FPU ctx leaked",
 918              syscallname(td->td_proc, sa.code)));
 919         KASSERT(td->td_pcb->pcb_save == get_pcb_user_save_td(td),
 920             ("System call %s returning with mangled pcb_save",
 921              syscallname(td->td_proc, sa.code)));
 922         KASSERT(td->td_md.md_invl_gen.gen == 0,
 923             ("System call %s returning with leaked invl_gen %lu",
 924             syscallname(td->td_proc, sa.code), td->td_md.md_invl_gen.gen));
 925
 926         syscallret(td, error, &sa);
 927
 928         /*
 929          * If the user-supplied value of %rip is not a canonical
 930          * address, then some CPUs will trigger a ring 0 #GP during
 931          * the sysret instruction.  However, the fault handler would
 932          * execute in ring 0 with the user's %gs and %rsp which would
 933          * not be safe.  Instead, use the full return path which
 934          * catches the problem safely.
 935          */
 936         if (td->td_frame->tf_rip >= VM_MAXUSER_ADDRESS)
 937                 set_pcb_flags(td->td_pcb, PCB_FULL_IRET);
 938 }