sys/i386/i386/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  * 386 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 #include "opt_trap.h"
  54
  55 #include <sys/param.h>
  56 #include <sys/bus.h>
  57 #include <sys/systm.h>
  58 #include <sys/proc.h>
  59 #include <sys/pioctl.h>
  60 #include <sys/ptrace.h>
  61 #include <sys/kdb.h>
  62 #include <sys/kernel.h>
  63 #include <sys/ktr.h>
  64 #include <sys/lock.h>
  65 #include <sys/mutex.h>
  66 #include <sys/resourcevar.h>
  67 #include <sys/signalvar.h>
  68 #include <sys/syscall.h>
  69 #include <sys/sysctl.h>
  70 #include <sys/sysent.h>
  71 #include <sys/uio.h>
  72 #include <sys/vmmeter.h>
  73 #ifdef HWPMC_HOOKS
  74 #include <sys/pmckern.h>
  75 PMC_SOFT_DEFINE( , , page_fault, all);
  76 PMC_SOFT_DEFINE( , , page_fault, read);
  77 PMC_SOFT_DEFINE( , , page_fault, write);
  78 #endif
  79 #include <security/audit/audit.h>
  80
  81 #include <vm/vm.h>
  82 #include <vm/vm_param.h>
  83 #include <vm/pmap.h>
  84 #include <vm/vm_kern.h>
  85 #include <vm/vm_map.h>
  86 #include <vm/vm_page.h>
  87 #include <vm/vm_extern.h>
  88
  89 #include <machine/cpu.h>
  90 #include <machine/intr_machdep.h>
  91 #include <x86/mca.h>
  92 #include <machine/md_var.h>
  93 #include <machine/pcb.h>
  94 #ifdef SMP
  95 #include <machine/smp.h>
  96 #endif
  97 #include <machine/stack.h>
  98 #include <machine/tss.h>
  99 #include <machine/vm86.h>
 100
 101 #ifdef POWERFAIL_NMI
 102 #include <sys/syslog.h>
 103 #include <machine/clock.h>
 104 #endif
 105
 106 #ifdef KDTRACE_HOOKS
 107 #include <sys/dtrace_bsd.h>
 108 #endif
 109
 110 extern void trap(struct trapframe *frame);
 111 extern void syscall(struct trapframe *frame);
 112
 113 static int trap_pfault(struct trapframe *, int, vm_offset_t);
 114 static void trap_fatal(struct trapframe *, vm_offset_t);
 115 void dblfault_handler(void);
 116
 117 extern inthand_t IDTVEC(lcall_syscall);
 118
 119 #define MAX_TRAP_MSG            32
 120 static char *trap_msg[] = {
 121         "",                                     /*  0 unused */
 122         "privileged instruction fault",         /*  1 T_PRIVINFLT */
 123         "",                                     /*  2 unused */
 124         "breakpoint instruction fault",         /*  3 T_BPTFLT */
 125         "",                                     /*  4 unused */
 126         "",                                     /*  5 unused */
 127         "arithmetic trap",                      /*  6 T_ARITHTRAP */
 128         "",                                     /*  7 unused */
 129         "",                                     /*  8 unused */
 130         "general protection fault",             /*  9 T_PROTFLT */
 131         "trace trap",                           /* 10 T_TRCTRAP */
 132         "",                                     /* 11 unused */
 133         "page fault",                           /* 12 T_PAGEFLT */
 134         "",                                     /* 13 unused */
 135         "alignment fault",                      /* 14 T_ALIGNFLT */
 136         "",                                     /* 15 unused */
 137         "",                                     /* 16 unused */
 138         "",                                     /* 17 unused */
 139         "integer divide fault",                 /* 18 T_DIVIDE */
 140         "non-maskable interrupt trap",          /* 19 T_NMI */
 141         "overflow trap",                        /* 20 T_OFLOW */
 142         "FPU bounds check fault",               /* 21 T_BOUND */
 143         "FPU device not available",             /* 22 T_DNA */
 144         "double fault",                         /* 23 T_DOUBLEFLT */
 145         "FPU operand fetch fault",              /* 24 T_FPOPFLT */
 146         "invalid TSS fault",                    /* 25 T_TSSFLT */
 147         "segment not present fault",            /* 26 T_SEGNPFLT */
 148         "stack fault",                          /* 27 T_STKFLT */
 149         "machine check trap",                   /* 28 T_MCHK */
 150         "SIMD floating-point exception",        /* 29 T_XMMFLT */
 151         "reserved (unknown) fault",             /* 30 T_RESERVED */
 152         "",                                     /* 31 unused (reserved) */
 153         "DTrace pid return trap",               /* 32 T_DTRACE_RET */
 154 };
 155
 156 #if defined(I586_CPU) && !defined(NO_F00F_HACK)
 157 int has_f00f_bug = 0;           /* Initialized so that it can be patched. */
 158 #endif
 159
 160 static int prot_fault_translation = 0;
 161 SYSCTL_INT(_machdep, OID_AUTO, prot_fault_translation, CTLFLAG_RW,
 162         &prot_fault_translation, 0, "Select signal to deliver on protection fault");
 163 static int uprintf_signal;
 164 SYSCTL_INT(_machdep, OID_AUTO, uprintf_signal, CTLFLAG_RW,
 165     &uprintf_signal, 0,
 166     "Print debugging information on trap signal to ctty");
 167
 168 /*
 169  * Exception, fault, and trap interface to the FreeBSD kernel.
 170  * This common code is called from assembly language IDT gate entry
 171  * routines that prepare a suitable stack frame, and restore this
 172  * frame after the exception has been processed.
 173  */
 174
 175 void
 176 trap(struct trapframe *frame)
 177 {
 178 #ifdef KDTRACE_HOOKS
 179         struct reg regs;
 180 #endif
 181         struct thread *td = curthread;
 182         struct proc *p = td->td_proc;
 183 #ifdef KDB
 184         register_t dr6;
 185 #endif
 186         int i = 0, ucode = 0;
 187         u_int type;
 188         register_t addr = 0;
 189         vm_offset_t eva;
 190         ksiginfo_t ksi;
 191 #ifdef POWERFAIL_NMI
 192         static int lastalert = 0;
 193 #endif
 194
 195         VM_CNT_INC(v_trap);
 196         type = frame->tf_trapno;
 197
 198 #ifdef SMP
 199         /* Handler for NMI IPIs used for stopping CPUs. */
 200         if (type == T_NMI) {
 201                  if (ipi_nmi_handler() == 0)
 202                            goto out;
 203         }
 204 #endif /* SMP */
 205
 206 #ifdef KDB
 207         if (kdb_active) {
 208                 kdb_reenter();
 209                 goto out;
 210         }
 211 #endif
 212
 213         if (type == T_RESERVED) {
 214                 trap_fatal(frame, 0);
 215                 goto out;
 216         }
 217
 218         if (type == T_NMI) {
 219 #ifdef HWPMC_HOOKS
 220                 /*
 221                  * CPU PMCs interrupt using an NMI so we check for that first.
 222                  * If the HWPMC module is active, 'pmc_hook' will point to
 223                  * the function to be called.  A non-zero return value from the
 224                  * hook means that the NMI was consumed by it and that we can
 225                  * return immediately.
 226                  */
 227                 if (pmc_intr != NULL &&
 228                     (*pmc_intr)(PCPU_GET(cpuid), frame) != 0)
 229                         goto out;
 230 #endif
 231
 232 #ifdef STACK
 233                 if (stack_nmi_handler(frame) != 0)
 234                         goto out;
 235 #endif
 236         }
 237
 238         if (type == T_MCHK) {
 239                 mca_intr();
 240                 goto out;
 241         }
 242
 243 #ifdef KDTRACE_HOOKS
 244         /*
 245          * A trap can occur while DTrace executes a probe. Before
 246          * executing the probe, DTrace blocks re-scheduling and sets
 247          * a flag in its per-cpu flags to indicate that it doesn't
 248          * want to fault. On returning from the probe, the no-fault
 249          * flag is cleared and finally re-scheduling is enabled.
 250          */
 251         if ((type == T_PROTFLT || type == T_PAGEFLT) &&
 252             dtrace_trap_func != NULL && (*dtrace_trap_func)(frame, type))
 253                 goto out;
 254 #endif
 255
 256         if ((frame->tf_eflags & PSL_I) == 0) {
 257                 /*
 258                  * Buggy application or kernel code has disabled
 259                  * interrupts and then trapped.  Enabling interrupts
 260                  * now is wrong, but it is better than running with
 261                  * interrupts disabled until they are accidentally
 262                  * enabled later.
 263                  */
 264                 if (TRAPF_USERMODE(frame) &&
 265                     (curpcb->pcb_flags & PCB_VM86CALL) == 0)
 266                         uprintf(
 267                             "pid %ld (%s): trap %d with interrupts disabled\n",
 268                             (long)curproc->p_pid, curthread->td_name, type);
 269                 else if (type != T_NMI && type != T_BPTFLT &&
 270                     type != T_TRCTRAP &&
 271                     frame->tf_eip != (int)cpu_switch_load_gs) {
 272                         /*
 273                          * XXX not quite right, since this may be for a
 274                          * multiple fault in user mode.
 275                          */
 276                         printf("kernel trap %d with interrupts disabled\n",
 277                             type);
 278                         /*
 279                          * Page faults need interrupts disabled until later,
 280                          * and we shouldn't enable interrupts while holding
 281                          * a spin lock.
 282                          */
 283                         if (type != T_PAGEFLT &&
 284                             td->td_md.md_spinlock_count == 0)
 285                                 enable_intr();
 286                 }
 287         }
 288         eva = 0;
 289         if (type == T_PAGEFLT) {
 290                 /*
 291                  * For some Cyrix CPUs, %cr2 is clobbered by
 292                  * interrupts.  This problem is worked around by using
 293                  * an interrupt gate for the pagefault handler.  We
 294                  * are finally ready to read %cr2 and conditionally
 295                  * reenable interrupts.  If we hold a spin lock, then
 296                  * we must not reenable interrupts.  This might be a
 297                  * spurious page fault.
 298                  */
 299                 eva = rcr2();
 300                 if (td->td_md.md_spinlock_count == 0)
 301                         enable_intr();
 302         }
 303
 304         if (TRAPF_USERMODE(frame) && (curpcb->pcb_flags & PCB_VM86CALL) == 0) {
 305                 /* user trap */
 306
 307                 td->td_pticks = 0;
 308                 td->td_frame = frame;
 309                 addr = frame->tf_eip;
 310                 if (td->td_cowgen != p->p_cowgen)
 311                         thread_cow_update(td);
 312
 313                 switch (type) {
 314                 case T_PRIVINFLT:       /* privileged instruction fault */
 315                         i = SIGILL;
 316                         ucode = ILL_PRVOPC;
 317                         break;
 318
 319                 case T_BPTFLT:          /* bpt instruction fault */
 320                 case T_TRCTRAP:         /* trace trap */
 321                         enable_intr();
 322 #ifdef KDTRACE_HOOKS
 323                         if (type == T_BPTFLT) {
 324                                 fill_frame_regs(frame, &regs);
 325                                 if (dtrace_pid_probe_ptr != NULL &&
 326                                     dtrace_pid_probe_ptr(&regs) == 0)
 327                                         goto out;
 328                         }
 329 #endif
 330 user_trctrap_out:
 331                         frame->tf_eflags &= ~PSL_T;
 332                         i = SIGTRAP;
 333                         ucode = (type == T_TRCTRAP ? TRAP_TRACE : TRAP_BRKPT);
 334                         break;
 335
 336                 case T_ARITHTRAP:       /* arithmetic trap */
 337                         ucode = npxtrap_x87();
 338                         if (ucode == -1)
 339                                 goto userout;
 340                         i = SIGFPE;
 341                         break;
 342
 343                         /*
 344                          * The following two traps can happen in
 345                          * vm86 mode, and, if so, we want to handle
 346                          * them specially.
 347                          */
 348                 case T_PROTFLT:         /* general protection fault */
 349                 case T_STKFLT:          /* stack fault */
 350                         if (frame->tf_eflags & PSL_VM) {
 351                                 i = vm86_emulate((struct vm86frame *)frame);
 352                                 if (i == SIGTRAP) {
 353                                         type = T_TRCTRAP;
 354                                         load_dr6(rdr6() | 0x4000);
 355                                         goto user_trctrap_out;
 356                                 }
 357                                 if (i == 0)
 358                                         goto user;
 359                                 break;
 360                         }
 361                         i = SIGBUS;
 362                         ucode = (type == T_PROTFLT) ? BUS_OBJERR : BUS_ADRERR;
 363                         break;
 364                 case T_SEGNPFLT:        /* segment not present fault */
 365                         i = SIGBUS;
 366                         ucode = BUS_ADRERR;
 367                         break;
 368                 case T_TSSFLT:          /* invalid TSS fault */
 369                         i = SIGBUS;
 370                         ucode = BUS_OBJERR;
 371                         break;
 372                 case T_ALIGNFLT:
 373                         i = SIGBUS;
 374                         ucode = BUS_ADRALN;
 375                         break;
 376                 case T_DOUBLEFLT:       /* double fault */
 377                 default:
 378                         i = SIGBUS;
 379                         ucode = BUS_OBJERR;
 380                         break;
 381
 382                 case T_PAGEFLT:         /* page fault */
 383
 384                         i = trap_pfault(frame, TRUE, eva);
 385 #if defined(I586_CPU) && !defined(NO_F00F_HACK)
 386                         if (i == -2) {
 387                                 /*
 388                                  * The f00f hack workaround has triggered, so
 389                                  * treat the fault as an illegal instruction
 390                                  * (T_PRIVINFLT) instead of a page fault.
 391                                  */
 392                                 type = frame->tf_trapno = T_PRIVINFLT;
 393
 394                                 /* Proceed as in that case. */
 395                                 ucode = ILL_PRVOPC;
 396                                 i = SIGILL;
 397                                 break;
 398                         }
 399 #endif
 400                         if (i == -1)
 401                                 goto userout;
 402                         if (i == 0)
 403                                 goto user;
 404
 405                         if (i == SIGSEGV)
 406                                 ucode = SEGV_MAPERR;
 407                         else {
 408                                 if (prot_fault_translation == 0) {
 409                                         /*
 410                                          * Autodetect.
 411                                          * This check also covers the images
 412                                          * without the ABI-tag ELF note.
 413                                          */
 414                                         if (SV_CURPROC_ABI() == SV_ABI_FREEBSD
 415                                             && p->p_osrel >= P_OSREL_SIGSEGV) {
 416                                                 i = SIGSEGV;
 417                                                 ucode = SEGV_ACCERR;
 418                                         } else {
 419                                                 i = SIGBUS;
 420                                                 ucode = BUS_PAGE_FAULT;
 421                                         }
 422                                 } else if (prot_fault_translation == 1) {
 423                                         /*
 424                                          * Always compat mode.
 425                                          */
 426                                         i = SIGBUS;
 427                                         ucode = BUS_PAGE_FAULT;
 428                                 } else {
 429                                         /*
 430                                          * Always SIGSEGV mode.
 431                                          */
 432                                         i = SIGSEGV;
 433                                         ucode = SEGV_ACCERR;
 434                                 }
 435                         }
 436                         addr = eva;
 437                         break;
 438
 439                 case T_DIVIDE:          /* integer divide fault */
 440                         ucode = FPE_INTDIV;
 441                         i = SIGFPE;
 442                         break;
 443
 444 #ifdef DEV_ISA
 445                 case T_NMI:
 446 #ifdef POWERFAIL_NMI
 447 #ifndef TIMER_FREQ
 448 #  define TIMER_FREQ 1193182
 449 #endif
 450                         if (time_second - lastalert > 10) {
 451                                 log(LOG_WARNING, "NMI: power fail\n");
 452                                 sysbeep(880, hz);
 453                                 lastalert = time_second;
 454                         }
 455                         goto userout;
 456 #else /* !POWERFAIL_NMI */
 457                         nmi_handle_intr(type, frame);
 458                         goto out;
 459 #endif /* POWERFAIL_NMI */
 460 #endif /* DEV_ISA */
 461
 462                 case T_OFLOW:           /* integer overflow fault */
 463                         ucode = FPE_INTOVF;
 464                         i = SIGFPE;
 465                         break;
 466
 467                 case T_BOUND:           /* bounds check fault */
 468                         ucode = FPE_FLTSUB;
 469                         i = SIGFPE;
 470                         break;
 471
 472                 case T_DNA:
 473                         KASSERT(PCB_USER_FPU(td->td_pcb),
 474                             ("kernel FPU ctx has leaked"));
 475                         /* transparent fault (due to context switch "late") */
 476                         if (npxdna())
 477                                 goto userout;
 478                         uprintf("pid %d killed due to lack of floating point\n",
 479                                 p->p_pid);
 480                         i = SIGKILL;
 481                         ucode = 0;
 482                         break;
 483
 484                 case T_FPOPFLT:         /* FPU operand fetch fault */
 485                         ucode = ILL_COPROC;
 486                         i = SIGILL;
 487                         break;
 488
 489                 case T_XMMFLT:          /* SIMD floating-point exception */
 490                         ucode = npxtrap_sse();
 491                         if (ucode == -1)
 492                                 goto userout;
 493                         i = SIGFPE;
 494                         break;
 495 #ifdef KDTRACE_HOOKS
 496                 case T_DTRACE_RET:
 497                         enable_intr();
 498                         fill_frame_regs(frame, &regs);
 499                         if (dtrace_return_probe_ptr != NULL &&
 500                             dtrace_return_probe_ptr(&regs) == 0)
 501                                 goto out;
 502                         goto userout;
 503 #endif
 504                 }
 505         } else {
 506                 /* kernel trap */
 507
 508                 KASSERT(cold || td->td_ucred != NULL,
 509                     ("kernel trap doesn't have ucred"));
 510                 switch (type) {
 511                 case T_PAGEFLT:                 /* page fault */
 512                         (void) trap_pfault(frame, FALSE, eva);
 513                         goto out;
 514
 515                 case T_DNA:
 516                         if (PCB_USER_FPU(td->td_pcb))
 517                                 panic("Unregistered use of FPU in kernel");
 518                         if (npxdna())
 519                                 goto out;
 520                         break;
 521
 522                 case T_ARITHTRAP:       /* arithmetic trap */
 523                 case T_XMMFLT:          /* SIMD floating-point exception */
 524                 case T_FPOPFLT:         /* FPU operand fetch fault */
 525                         /*
 526                          * XXXKIB for now disable any FPU traps in kernel
 527                          * handler registration seems to be overkill
 528                          */
 529                         trap_fatal(frame, 0);
 530                         goto out;
 531
 532                         /*
 533                          * The following two traps can happen in
 534                          * vm86 mode, and, if so, we want to handle
 535                          * them specially.
 536                          */
 537                 case T_PROTFLT:         /* general protection fault */
 538                 case T_STKFLT:          /* stack fault */
 539                         if (frame->tf_eflags & PSL_VM) {
 540                                 i = vm86_emulate((struct vm86frame *)frame);
 541                                 if (i == SIGTRAP) {
 542                                         type = T_TRCTRAP;
 543                                         load_dr6(rdr6() | 0x4000);
 544                                         goto kernel_trctrap;
 545                                 }
 546                                 if (i != 0)
 547                                         /*
 548                                          * returns to original process
 549                                          */
 550                                         vm86_trap((struct vm86frame *)frame);
 551                                 goto out;
 552                         }
 553                         /* FALL THROUGH */
 554                 case T_SEGNPFLT:        /* segment not present fault */
 555                         if (curpcb->pcb_flags & PCB_VM86CALL)
 556                                 break;
 557
 558                         /*
 559                          * Invalid %fs's and %gs's can be created using
 560                          * procfs or PT_SETREGS or by invalidating the
 561                          * underlying LDT entry.  This causes a fault
 562                          * in kernel mode when the kernel attempts to
 563                          * switch contexts.  Lose the bad context
 564                          * (XXX) so that we can continue, and generate
 565                          * a signal.
 566                          */
 567                         if (frame->tf_eip == (int)cpu_switch_load_gs) {
 568                                 curpcb->pcb_gs = 0;
 569 #if 0
 570                                 PROC_LOCK(p);
 571                                 kern_psignal(p, SIGBUS);
 572                                 PROC_UNLOCK(p);
 573 #endif
 574                                 goto out;
 575                         }
 576
 577                         if (td->td_intr_nesting_level != 0)
 578                                 break;
 579
 580                         /*
 581                          * Invalid segment selectors and out of bounds
 582                          * %eip's and %esp's can be set up in user mode.
 583                          * This causes a fault in kernel mode when the
 584                          * kernel tries to return to user mode.  We want
 585                          * to get this fault so that we can fix the
 586                          * problem here and not have to check all the
 587                          * selectors and pointers when the user changes
 588                          * them.
 589                          */
 590                         if (frame->tf_eip == (int)doreti_iret) {
 591                                 frame->tf_eip = (int)doreti_iret_fault;
 592                                 goto out;
 593                         }
 594                         if (type == T_STKFLT)
 595                                 break;
 596
 597                         if (frame->tf_eip == (int)doreti_popl_ds) {
 598                                 frame->tf_eip = (int)doreti_popl_ds_fault;
 599                                 goto out;
 600                         }
 601                         if (frame->tf_eip == (int)doreti_popl_es) {
 602                                 frame->tf_eip = (int)doreti_popl_es_fault;
 603                                 goto out;
 604                         }
 605                         if (frame->tf_eip == (int)doreti_popl_fs) {
 606                                 frame->tf_eip = (int)doreti_popl_fs_fault;
 607                                 goto out;
 608                         }
 609                         if (curpcb->pcb_onfault != NULL) {
 610                                 frame->tf_eip =
 611                                     (int)curpcb->pcb_onfault;
 612                                 goto out;
 613                         }
 614                         break;
 615
 616                 case T_TSSFLT:
 617                         /*
 618                          * PSL_NT can be set in user mode and isn't cleared
 619                          * automatically when the kernel is entered.  This
 620                          * causes a TSS fault when the kernel attempts to
 621                          * `iret' because the TSS link is uninitialized.  We
 622                          * want to get this fault so that we can fix the
 623                          * problem here and not every time the kernel is
 624                          * entered.
 625                          */
 626                         if (frame->tf_eflags & PSL_NT) {
 627                                 frame->tf_eflags &= ~PSL_NT;
 628                                 goto out;
 629                         }
 630                         break;
 631
 632                 case T_TRCTRAP:  /* trace trap */
 633 kernel_trctrap:
 634                         if (frame->tf_eip == (int)IDTVEC(lcall_syscall)) {
 635                                 /*
 636                                  * We've just entered system mode via the
 637                                  * syscall lcall.  Continue single stepping
 638                                  * silently until the syscall handler has
 639                                  * saved the flags.
 640                                  */
 641                                 goto out;
 642                         }
 643                         if (frame->tf_eip == (int)IDTVEC(lcall_syscall) + 1) {
 644                                 /*
 645                                  * The syscall handler has now saved the
 646                                  * flags.  Stop single stepping it.
 647                                  */
 648                                 frame->tf_eflags &= ~PSL_T;
 649                                 goto out;
 650                         }
 651                         /*
 652                          * Ignore debug register trace traps due to
 653                          * accesses in the user's address space, which
 654                          * can happen under several conditions such as
 655                          * if a user sets a watchpoint on a buffer and
 656                          * then passes that buffer to a system call.
 657                          * We still want to get TRCTRAPS for addresses
 658                          * in kernel space because that is useful when
 659                          * debugging the kernel.
 660                          */
 661                         if (user_dbreg_trap() &&
 662                            !(curpcb->pcb_flags & PCB_VM86CALL)) {
 663                                 /*
 664                                  * Reset breakpoint bits because the
 665                                  * processor doesn't
 666                                  */
 667                                 load_dr6(rdr6() & ~0xf);
 668                                 goto out;
 669                         }
 670                         /*
 671                          * FALLTHROUGH (TRCTRAP kernel mode, kernel address)
 672                          */
 673                 case T_BPTFLT:
 674                         /*
 675                          * If KDB is enabled, let it handle the debugger trap.
 676                          * Otherwise, debugger traps "can't happen".
 677                          */
 678 #ifdef KDB
 679                         /* XXX %dr6 is not quite reentrant. */
 680                         dr6 = rdr6();
 681                         load_dr6(dr6 & ~0x4000);
 682                         if (kdb_trap(type, dr6, frame))
 683                                 goto out;
 684 #endif
 685                         break;
 686
 687 #ifdef DEV_ISA
 688                 case T_NMI:
 689 #ifdef POWERFAIL_NMI
 690                         if (time_second - lastalert > 10) {
 691                                 log(LOG_WARNING, "NMI: power fail\n");
 692                                 sysbeep(880, hz);
 693                                 lastalert = time_second;
 694                         }
 695                         goto out;
 696 #else /* !POWERFAIL_NMI */
 697                         nmi_handle_intr(type, frame);
 698                         goto out;
 699 #endif /* POWERFAIL_NMI */
 700 #endif /* DEV_ISA */
 701                 }
 702
 703                 trap_fatal(frame, eva);
 704                 goto out;
 705         }
 706
 707         /* Translate fault for emulators (e.g. Linux) */
 708         if (*p->p_sysent->sv_transtrap)
 709                 i = (*p->p_sysent->sv_transtrap)(i, type);
 710
 711         ksiginfo_init_trap(&ksi);
 712         ksi.ksi_signo = i;
 713         ksi.ksi_code = ucode;
 714         ksi.ksi_addr = (void *)addr;
 715         ksi.ksi_trapno = type;
 716         if (uprintf_signal) {
 717                 uprintf("pid %d comm %s: signal %d err %x code %d type %d "
 718                     "addr 0x%x esp 0x%08x eip 0x%08x "
 719                     "<%02x %02x %02x %02x %02x %02x %02x %02x>\n",
 720                     p->p_pid, p->p_comm, i, frame->tf_err, ucode, type, addr,
 721                     frame->tf_esp, frame->tf_eip,
 722                     fubyte((void *)(frame->tf_eip + 0)),
 723                     fubyte((void *)(frame->tf_eip + 1)),
 724                     fubyte((void *)(frame->tf_eip + 2)),
 725                     fubyte((void *)(frame->tf_eip + 3)),
 726                     fubyte((void *)(frame->tf_eip + 4)),
 727                     fubyte((void *)(frame->tf_eip + 5)),
 728                     fubyte((void *)(frame->tf_eip + 6)),
 729                     fubyte((void *)(frame->tf_eip + 7)));
 730         }
 731         KASSERT((read_eflags() & PSL_I) != 0, ("interrupts disabled"));
 732         trapsignal(td, &ksi);
 733
 734 #ifdef DEBUG
 735         if (type <= MAX_TRAP_MSG) {
 736                 uprintf("fatal process exception: %s",
 737                         trap_msg[type]);
 738                 if ((type == T_PAGEFLT) || (type == T_PROTFLT))
 739                         uprintf(", fault VA = 0x%lx", (u_long)eva);
 740                 uprintf("\n");
 741         }
 742 #endif
 743
 744 user:
 745         userret(td, frame);
 746         KASSERT(PCB_USER_FPU(td->td_pcb),
 747             ("Return from trap with kernel FPU ctx leaked"));
 748 userout:
 749 out:
 750         return;
 751 }
 752
 753 static int
 754 trap_pfault(frame, usermode, eva)
 755         struct trapframe *frame;
 756         int usermode;
 757         vm_offset_t eva;
 758 {
 759         vm_offset_t va;
 760         vm_map_t map;
 761         int rv = 0;
 762         vm_prot_t ftype;
 763         struct thread *td = curthread;
 764         struct proc *p = td->td_proc;
 765
 766         if (__predict_false((td->td_pflags & TDP_NOFAULTING) != 0)) {
 767                 /*
 768                  * Due to both processor errata and lazy TLB invalidation when
 769                  * access restrictions are removed from virtual pages, memory
 770                  * accesses that are allowed by the physical mapping layer may
 771                  * nonetheless cause one spurious page fault per virtual page.
 772                  * When the thread is executing a "no faulting" section that
 773                  * is bracketed by vm_fault_{disable,enable}_pagefaults(),
 774                  * every page fault is treated as a spurious page fault,
 775                  * unless it accesses the same virtual address as the most
 776                  * recent page fault within the same "no faulting" section.
 777                  */
 778                 if (td->td_md.md_spurflt_addr != eva ||
 779                     (td->td_pflags & TDP_RESETSPUR) != 0) {
 780                         /*
 781                          * Do nothing to the TLB.  A stale TLB entry is
 782                          * flushed automatically by a page fault.
 783                          */
 784                         td->td_md.md_spurflt_addr = eva;
 785                         td->td_pflags &= ~TDP_RESETSPUR;
 786                         return (0);
 787                 }
 788         } else {
 789                 /*
 790                  * If we get a page fault while in a critical section, then
 791                  * it is most likely a fatal kernel page fault.  The kernel
 792                  * is already going to panic trying to get a sleep lock to
 793                  * do the VM lookup, so just consider it a fatal trap so the
 794                  * kernel can print out a useful trap message and even get
 795                  * to the debugger.
 796                  *
 797                  * If we get a page fault while holding a non-sleepable
 798                  * lock, then it is most likely a fatal kernel page fault.
 799                  * If WITNESS is enabled, then it's going to whine about
 800                  * bogus LORs with various VM locks, so just skip to the
 801                  * fatal trap handling directly.
 802                  */
 803                 if (td->td_critnest != 0 ||
 804                     WITNESS_CHECK(WARN_SLEEPOK | WARN_GIANTOK, NULL,
 805                     "Kernel page fault") != 0) {
 806                         trap_fatal(frame, eva);
 807                         return (-1);
 808                 }
 809         }
 810         va = trunc_page(eva);
 811         if (va >= KERNBASE) {
 812                 /*
 813                  * Don't allow user-mode faults in kernel address space.
 814                  * An exception:  if the faulting address is the invalid
 815                  * instruction entry in the IDT, then the Intel Pentium
 816                  * F00F bug workaround was triggered, and we need to
 817                  * treat it is as an illegal instruction, and not a page
 818                  * fault.
 819                  */
 820 #if defined(I586_CPU) && !defined(NO_F00F_HACK)
 821                 if ((eva == (unsigned int)&idt[6]) && has_f00f_bug)
 822                         return (-2);
 823 #endif
 824                 if (usermode)
 825                         goto nogo;
 826
 827                 map = kernel_map;
 828         } else {
 829                 map = &p->p_vmspace->vm_map;
 830
 831                 /*
 832                  * When accessing a user-space address, kernel must be
 833                  * ready to accept the page fault, and provide a
 834                  * handling routine.  Since accessing the address
 835                  * without the handler is a bug, do not try to handle
 836                  * it normally, and panic immediately.
 837                  */
 838                 if (!usermode && (td->td_intr_nesting_level != 0 ||
 839                     curpcb->pcb_onfault == NULL)) {
 840                         trap_fatal(frame, eva);
 841                         return (-1);
 842                 }
 843         }
 844
 845         /*
 846          * If the trap was caused by errant bits in the PTE then panic.
 847          */
 848         if (frame->tf_err & PGEX_RSV) {
 849                 trap_fatal(frame, eva);
 850                 return (-1);
 851         }
 852
 853         /*
 854          * PGEX_I is defined only if the execute disable bit capability is
 855          * supported and enabled.
 856          */
 857         if (frame->tf_err & PGEX_W)
 858                 ftype = VM_PROT_WRITE;
 859 #if defined(PAE) || defined(PAE_TABLES)
 860         else if ((frame->tf_err & PGEX_I) && pg_nx != 0)
 861                 ftype = VM_PROT_EXECUTE;
 862 #endif
 863         else
 864                 ftype = VM_PROT_READ;
 865
 866         /* Fault in the page. */
 867         rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
 868         if (rv == KERN_SUCCESS) {
 869 #ifdef HWPMC_HOOKS
 870                 if (ftype == VM_PROT_READ || ftype == VM_PROT_WRITE) {
 871                         PMC_SOFT_CALL_TF( , , page_fault, all, frame);
 872                         if (ftype == VM_PROT_READ)
 873                                 PMC_SOFT_CALL_TF( , , page_fault, read,
 874                                     frame);
 875                         else
 876                                 PMC_SOFT_CALL_TF( , , page_fault, write,
 877                                     frame);
 878                 }
 879 #endif
 880                 return (0);
 881         }
 882 nogo:
 883         if (!usermode) {
 884                 if (td->td_intr_nesting_level == 0 &&
 885                     curpcb->pcb_onfault != NULL) {
 886                         frame->tf_eip = (int)curpcb->pcb_onfault;
 887                         return (0);
 888                 }
 889                 trap_fatal(frame, eva);
 890                 return (-1);
 891         }
 892         return ((rv == KERN_PROTECTION_FAILURE) ? SIGBUS : SIGSEGV);
 893 }
 894
 895 static void
 896 trap_fatal(frame, eva)
 897         struct trapframe *frame;
 898         vm_offset_t eva;
 899 {
 900         int code, ss, esp;
 901         u_int type;
 902         struct soft_segment_descriptor softseg;
 903         char *msg;
 904
 905         code = frame->tf_err;
 906         type = frame->tf_trapno;
 907         sdtossd(&gdt[IDXSEL(frame->tf_cs & 0xffff)].sd, &softseg);
 908
 909         if (type <= MAX_TRAP_MSG)
 910                 msg = trap_msg[type];
 911         else
 912                 msg = "UNKNOWN";
 913         printf("\n\nFatal trap %d: %s while in %s mode\n", type, msg,
 914             frame->tf_eflags & PSL_VM ? "vm86" :
 915             ISPL(frame->tf_cs) == SEL_UPL ? "user" : "kernel");
 916 #ifdef SMP
 917         /* two separate prints in case of a trap on an unmapped page */
 918         printf("cpuid = %d; ", PCPU_GET(cpuid));
 919         printf("apic id = %02x\n", PCPU_GET(apic_id));
 920 #endif
 921         if (type == T_PAGEFLT) {
 922                 printf("fault virtual address   = 0x%x\n", eva);
 923                 printf("fault code              = %s %s%s, %s\n",
 924                         code & PGEX_U ? "user" : "supervisor",
 925                         code & PGEX_W ? "write" : "read",
 926 #if defined(PAE) || defined(PAE_TABLES)
 927                         pg_nx != 0 ?
 928                         (code & PGEX_I ? " instruction" : " data") :
 929 #endif
 930                         "",
 931                         code & PGEX_RSV ? "reserved bits in PTE" :
 932                         code & PGEX_P ? "protection violation" : "page not present");
 933         }
 934         printf("instruction pointer     = 0x%x:0x%x\n",
 935                frame->tf_cs & 0xffff, frame->tf_eip);
 936         if (TF_HAS_STACKREGS(frame)) {
 937                 ss = frame->tf_ss & 0xffff;
 938                 esp = frame->tf_esp;
 939         } else {
 940                 ss = GSEL(GDATA_SEL, SEL_KPL);
 941                 esp = (int)&frame->tf_esp;
 942         }
 943         printf("stack pointer           = 0x%x:0x%x\n", ss, esp);
 944         printf("frame pointer           = 0x%x:0x%x\n", ss, frame->tf_ebp);
 945         printf("code segment            = base 0x%x, limit 0x%x, type 0x%x\n",
 946                softseg.ssd_base, softseg.ssd_limit, softseg.ssd_type);
 947         printf("                        = DPL %d, pres %d, def32 %d, gran %d\n",
 948                softseg.ssd_dpl, softseg.ssd_p, softseg.ssd_def32,
 949                softseg.ssd_gran);
 950         printf("processor eflags        = ");
 951         if (frame->tf_eflags & PSL_T)
 952                 printf("trace trap, ");
 953         if (frame->tf_eflags & PSL_I)
 954                 printf("interrupt enabled, ");
 955         if (frame->tf_eflags & PSL_NT)
 956                 printf("nested task, ");
 957         if (frame->tf_eflags & PSL_RF)
 958                 printf("resume, ");
 959         if (frame->tf_eflags & PSL_VM)
 960                 printf("vm86, ");
 961         printf("IOPL = %d\n", (frame->tf_eflags & PSL_IOPL) >> 12);
 962         printf("current process         = %d (%s)\n",
 963             curproc->p_pid, curthread->td_name);
 964
 965 #ifdef KDB
 966         if (debugger_on_panic || kdb_active) {
 967                 frame->tf_err = eva;    /* smuggle fault address to ddb */
 968                 if (kdb_trap(type, 0, frame)) {
 969                         frame->tf_err = code;   /* restore error code */
 970                         return;
 971                 }
 972                 frame->tf_err = code;           /* restore error code */
 973         }
 974 #endif
 975         printf("trap number             = %d\n", type);
 976         if (type <= MAX_TRAP_MSG)
 977                 panic("%s", trap_msg[type]);
 978         else
 979                 panic("unknown/reserved trap");
 980 }
 981
 982 /*
 983  * Double fault handler. Called when a fault occurs while writing
 984  * a frame for a trap/exception onto the stack. This usually occurs
 985  * when the stack overflows (such is the case with infinite recursion,
 986  * for example).
 987  *
 988  * XXX Note that the current PTD gets replaced by IdlePTD when the
 989  * task switch occurs. This means that the stack that was active at
 990  * the time of the double fault is not available at <kstack> unless
 991  * the machine was idle when the double fault occurred. The downside
 992  * of this is that "trace <ebp>" in ddb won't work.
 993  */
 994 void
 995 dblfault_handler()
 996 {
 997 #ifdef KDTRACE_HOOKS
 998         if (dtrace_doubletrap_func != NULL)
 999                 (*dtrace_doubletrap_func)();
1000 #endif
1001         printf("\nFatal double fault:\n");
1002         printf("eip = 0x%x\n", PCPU_GET(common_tss.tss_eip));
1003         printf("esp = 0x%x\n", PCPU_GET(common_tss.tss_esp));
1004         printf("ebp = 0x%x\n", PCPU_GET(common_tss.tss_ebp));
1005 #ifdef SMP
1006         /* two separate prints in case of a trap on an unmapped page */
1007         printf("cpuid = %d; ", PCPU_GET(cpuid));
1008         printf("apic id = %02x\n", PCPU_GET(apic_id));
1009 #endif
1010         panic("double fault");
1011 }
1012
1013 int
1014 cpu_fetch_syscall_args(struct thread *td)
1015 {
1016         struct proc *p;
1017         struct trapframe *frame;
1018         struct syscall_args *sa;
1019         caddr_t params;
1020         long tmp;
1021         int error;
1022
1023         p = td->td_proc;
1024         frame = td->td_frame;
1025         sa = &td->td_sa;
1026
1027         params = (caddr_t)frame->tf_esp + sizeof(int);
1028         sa->code = frame->tf_eax;
1029
1030         /*
1031          * Need to check if this is a 32 bit or 64 bit syscall.
1032          */
1033         if (sa->code == SYS_syscall) {
1034                 /*
1035                  * Code is first argument, followed by actual args.
1036                  */
1037                 error = fueword(params, &tmp);
1038                 if (error == -1)
1039                         return (EFAULT);
1040                 sa->code = tmp;
1041                 params += sizeof(int);
1042         } else if (sa->code == SYS___syscall) {
1043                 /*
1044                  * Like syscall, but code is a quad, so as to maintain
1045                  * quad alignment for the rest of the arguments.
1046                  */
1047                 error = fueword(params, &tmp);
1048                 if (error == -1)
1049                         return (EFAULT);
1050                 sa->code = tmp;
1051                 params += sizeof(quad_t);
1052         }
1053
1054         if (p->p_sysent->sv_mask)
1055                 sa->code &= p->p_sysent->sv_mask;
1056         if (sa->code >= p->p_sysent->sv_size)
1057                 sa->callp = &p->p_sysent->sv_table[0];
1058         else
1059                 sa->callp = &p->p_sysent->sv_table[sa->code];
1060         sa->narg = sa->callp->sy_narg;
1061
1062         if (params != NULL && sa->narg != 0)
1063                 error = copyin(params, (caddr_t)sa->args,
1064                     (u_int)(sa->narg * sizeof(int)));
1065         else
1066                 error = 0;
1067
1068         if (error == 0) {
1069                 td->td_retval[0] = 0;
1070                 td->td_retval[1] = frame->tf_edx;
1071         }
1072
1073         return (error);
1074 }
1075
1076 #include "../../kern/subr_syscall.c"
1077
1078 /*
1079  * syscall - system call request C handler.  A system call is
1080  * essentially treated as a trap by reusing the frame layout.
1081  */
1082 void
1083 syscall(struct trapframe *frame)
1084 {
1085         struct thread *td;
1086         register_t orig_tf_eflags;
1087         int error;
1088         ksiginfo_t ksi;
1089
1090 #ifdef DIAGNOSTIC
1091         if (!(TRAPF_USERMODE(frame) &&
1092             (curpcb->pcb_flags & PCB_VM86CALL) == 0)) {
1093                 panic("syscall");
1094                 /* NOT REACHED */
1095         }
1096 #endif
1097         orig_tf_eflags = frame->tf_eflags;
1098
1099         td = curthread;
1100         td->td_frame = frame;
1101
1102         error = syscallenter(td);
1103
1104         /*
1105          * Traced syscall.
1106          */
1107         if ((orig_tf_eflags & PSL_T) && !(orig_tf_eflags & PSL_VM)) {
1108                 frame->tf_eflags &= ~PSL_T;
1109                 ksiginfo_init_trap(&ksi);
1110                 ksi.ksi_signo = SIGTRAP;
1111                 ksi.ksi_code = TRAP_TRACE;
1112                 ksi.ksi_addr = (void *)frame->tf_eip;
1113                 trapsignal(td, &ksi);
1114         }
1115
1116         KASSERT(PCB_USER_FPU(td->td_pcb),
1117             ("System call %s returning with kernel FPU ctx leaked",
1118              syscallname(td->td_proc, td->td_sa.code)));
1119         KASSERT(td->td_pcb->pcb_save == get_pcb_user_save_td(td),
1120             ("System call %s returning with mangled pcb_save",
1121              syscallname(td->td_proc, td->td_sa.code)));
1122
1123         syscallret(td, error);
1124 }