The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/i386/i386/trap.c

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    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: stable/10/sys/i386/i386/trap.c 333370 2018-05-08 17:05:39Z emaste $");
   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_kdtrace.h"
   53 #include "opt_npx.h"
   54 #include "opt_trap.h"
   55 
   56 #include <sys/param.h>
   57 #include <sys/bus.h>
   58 #include <sys/systm.h>
   59 #include <sys/proc.h>
   60 #include <sys/pioctl.h>
   61 #include <sys/ptrace.h>
   62 #include <sys/kdb.h>
   63 #include <sys/kernel.h>
   64 #include <sys/ktr.h>
   65 #include <sys/lock.h>
   66 #include <sys/mutex.h>
   67 #include <sys/resourcevar.h>
   68 #include <sys/signalvar.h>
   69 #include <sys/syscall.h>
   70 #include <sys/sysctl.h>
   71 #include <sys/sysent.h>
   72 #include <sys/uio.h>
   73 #include <sys/vmmeter.h>
   74 #ifdef HWPMC_HOOKS
   75 #include <sys/pmckern.h>
   76 PMC_SOFT_DEFINE( , , page_fault, all);
   77 PMC_SOFT_DEFINE( , , page_fault, read);
   78 PMC_SOFT_DEFINE( , , page_fault, write);
   79 #endif
   80 #include <security/audit/audit.h>
   81 
   82 #include <vm/vm.h>
   83 #include <vm/vm_param.h>
   84 #include <vm/pmap.h>
   85 #include <vm/vm_kern.h>
   86 #include <vm/vm_map.h>
   87 #include <vm/vm_page.h>
   88 #include <vm/vm_extern.h>
   89 
   90 #include <machine/cpu.h>
   91 #include <machine/intr_machdep.h>
   92 #include <x86/mca.h>
   93 #include <machine/md_var.h>
   94 #include <machine/pcb.h>
   95 #ifdef SMP
   96 #include <machine/smp.h>
   97 #endif
   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 extern inthand_t IDTVEC(bpt), IDTVEC(dbg), IDTVEC(int0x80_syscall);
  120 
  121 #define MAX_TRAP_MSG            32
  122 static char *trap_msg[] = {
  123         "",                                     /*  0 unused */
  124         "privileged instruction fault",         /*  1 T_PRIVINFLT */
  125         "",                                     /*  2 unused */
  126         "breakpoint instruction fault",         /*  3 T_BPTFLT */
  127         "",                                     /*  4 unused */
  128         "",                                     /*  5 unused */
  129         "arithmetic trap",                      /*  6 T_ARITHTRAP */
  130         "",                                     /*  7 unused */
  131         "",                                     /*  8 unused */
  132         "general protection fault",             /*  9 T_PROTFLT */
  133         "trace trap",                           /* 10 T_TRCTRAP */
  134         "",                                     /* 11 unused */
  135         "page fault",                           /* 12 T_PAGEFLT */
  136         "",                                     /* 13 unused */
  137         "alignment fault",                      /* 14 T_ALIGNFLT */
  138         "",                                     /* 15 unused */
  139         "",                                     /* 16 unused */
  140         "",                                     /* 17 unused */
  141         "integer divide fault",                 /* 18 T_DIVIDE */
  142         "non-maskable interrupt trap",          /* 19 T_NMI */
  143         "overflow trap",                        /* 20 T_OFLOW */
  144         "FPU bounds check fault",               /* 21 T_BOUND */
  145         "FPU device not available",             /* 22 T_DNA */
  146         "double fault",                         /* 23 T_DOUBLEFLT */
  147         "FPU operand fetch fault",              /* 24 T_FPOPFLT */
  148         "invalid TSS fault",                    /* 25 T_TSSFLT */
  149         "segment not present fault",            /* 26 T_SEGNPFLT */
  150         "stack fault",                          /* 27 T_STKFLT */
  151         "machine check trap",                   /* 28 T_MCHK */
  152         "SIMD floating-point exception",        /* 29 T_XMMFLT */
  153         "reserved (unknown) fault",             /* 30 T_RESERVED */
  154         "",                                     /* 31 unused (reserved) */
  155         "DTrace pid return trap",               /* 32 T_DTRACE_RET */
  156 };
  157 
  158 #if defined(I586_CPU) && !defined(NO_F00F_HACK)
  159 int has_f00f_bug = 0;           /* Initialized so that it can be patched. */
  160 #endif
  161 
  162 #ifdef KDB
  163 static int kdb_on_nmi = 1;
  164 SYSCTL_INT(_machdep, OID_AUTO, kdb_on_nmi, CTLFLAG_RW,
  165         &kdb_on_nmi, 0, "Go to KDB on NMI");
  166 TUNABLE_INT("machdep.kdb_on_nmi", &kdb_on_nmi);
  167 #endif
  168 static int panic_on_nmi = 1;
  169 SYSCTL_INT(_machdep, OID_AUTO, panic_on_nmi, CTLFLAG_RW,
  170         &panic_on_nmi, 0, "Panic on NMI");
  171 TUNABLE_INT("machdep.panic_on_nmi", &panic_on_nmi);
  172 static int prot_fault_translation = 0;
  173 SYSCTL_INT(_machdep, OID_AUTO, prot_fault_translation, CTLFLAG_RW,
  174         &prot_fault_translation, 0, "Select signal to deliver on protection fault");
  175 static int uprintf_signal;
  176 SYSCTL_INT(_machdep, OID_AUTO, uprintf_signal, CTLFLAG_RW,
  177     &uprintf_signal, 0,
  178     "Print debugging information on trap signal to ctty");
  179 
  180 /*
  181  * Exception, fault, and trap interface to the FreeBSD kernel.
  182  * This common code is called from assembly language IDT gate entry
  183  * routines that prepare a suitable stack frame, and restore this
  184  * frame after the exception has been processed.
  185  */
  186 
  187 void
  188 trap(struct trapframe *frame)
  189 {
  190 #ifdef KDTRACE_HOOKS
  191         struct reg regs;
  192 #endif
  193         struct thread *td = curthread;
  194         struct proc *p = td->td_proc;
  195         int i = 0, ucode = 0, code;
  196         u_int type;
  197         register_t addr = 0;
  198         vm_offset_t eva;
  199         ksiginfo_t ksi;
  200 #ifdef POWERFAIL_NMI
  201         static int lastalert = 0;
  202 #endif
  203 
  204         PCPU_INC(cnt.v_trap);
  205         type = frame->tf_trapno;
  206 
  207 #ifdef SMP
  208         /* Handler for NMI IPIs used for stopping CPUs. */
  209         if (type == T_NMI) {
  210                  if (ipi_nmi_handler() == 0)
  211                            goto out;
  212         }
  213 #endif /* SMP */
  214 
  215 #ifdef KDB
  216         if (kdb_active) {
  217                 kdb_reenter();
  218                 goto out;
  219         }
  220 #endif
  221 
  222         if (type == T_RESERVED) {
  223                 trap_fatal(frame, 0);
  224                 goto out;
  225         }
  226 
  227 #ifdef  HWPMC_HOOKS
  228         /*
  229          * CPU PMCs interrupt using an NMI so we check for that first.
  230          * If the HWPMC module is active, 'pmc_hook' will point to
  231          * the function to be called.  A return value of '1' from the
  232          * hook means that the NMI was handled by it and that we can
  233          * return immediately.
  234          */
  235         if (type == T_NMI && pmc_intr &&
  236             (*pmc_intr)(PCPU_GET(cpuid), frame))
  237             goto out;
  238 #endif
  239 
  240         if (type == T_MCHK) {
  241                 mca_intr();
  242                 goto out;
  243         }
  244 
  245 #ifdef KDTRACE_HOOKS
  246         /*
  247          * A trap can occur while DTrace executes a probe. Before
  248          * executing the probe, DTrace blocks re-scheduling and sets
  249          * a flag in its per-cpu flags to indicate that it doesn't
  250          * want to fault. On returning from the probe, the no-fault
  251          * flag is cleared and finally re-scheduling is enabled.
  252          */
  253         if ((type == T_PROTFLT || type == T_PAGEFLT) &&
  254             dtrace_trap_func != NULL && (*dtrace_trap_func)(frame, type))
  255                 goto out;
  256 #endif
  257 
  258         if ((frame->tf_eflags & PSL_I) == 0) {
  259                 /*
  260                  * Buggy application or kernel code has disabled
  261                  * interrupts and then trapped.  Enabling interrupts
  262                  * now is wrong, but it is better than running with
  263                  * interrupts disabled until they are accidentally
  264                  * enabled later.
  265                  */
  266                 if (ISPL(frame->tf_cs) == SEL_UPL || (frame->tf_eflags & PSL_VM))
  267                         uprintf(
  268                             "pid %ld (%s): trap %d with interrupts disabled\n",
  269                             (long)curproc->p_pid, curthread->td_name, type);
  270                 else if (type != T_NMI && type != T_BPTFLT &&
  271                     type != T_TRCTRAP &&
  272                     frame->tf_eip != (int)cpu_switch_load_gs) {
  273                         /*
  274                          * XXX not quite right, since this may be for a
  275                          * multiple fault in user mode.
  276                          */
  277                         printf("kernel trap %d with interrupts disabled\n",
  278                             type);
  279                         /*
  280                          * Page faults need interrupts disabled until later,
  281                          * and we shouldn't enable interrupts while holding
  282                          * a spin lock.
  283                          */
  284                         if (type != T_PAGEFLT &&
  285                             td->td_md.md_spinlock_count == 0)
  286                                 enable_intr();
  287                 }
  288         }
  289         eva = 0;
  290         code = frame->tf_err;
  291         if (type == T_PAGEFLT) {
  292                 /*
  293                  * For some Cyrix CPUs, %cr2 is clobbered by
  294                  * interrupts.  This problem is worked around by using
  295                  * an interrupt gate for the pagefault handler.  We
  296                  * are finally ready to read %cr2 and conditionally
  297                  * reenable interrupts.  If we hold a spin lock, then
  298                  * we must not reenable interrupts.  This might be a
  299                  * spurious page fault.
  300                  */
  301                 eva = rcr2();
  302                 if (td->td_md.md_spinlock_count == 0)
  303                         enable_intr();
  304         }
  305 
  306         if ((ISPL(frame->tf_cs) == SEL_UPL) ||
  307             ((frame->tf_eflags & PSL_VM) && 
  308                 !(curpcb->pcb_flags & PCB_VM86CALL))) {
  309                 /* user trap */
  310 
  311                 td->td_pticks = 0;
  312                 td->td_frame = frame;
  313                 addr = frame->tf_eip;
  314                 if (td->td_ucred != p->p_ucred) 
  315                         cred_update_thread(td);
  316 
  317                 switch (type) {
  318                 case T_PRIVINFLT:       /* privileged instruction fault */
  319                         i = SIGILL;
  320                         ucode = ILL_PRVOPC;
  321                         break;
  322 
  323                 case T_BPTFLT:          /* bpt instruction fault */
  324                 case T_TRCTRAP:         /* trace trap */
  325                         enable_intr();
  326 #ifdef KDTRACE_HOOKS
  327                         if (type == T_BPTFLT) {
  328                                 fill_frame_regs(frame, &regs);
  329                                 if (dtrace_pid_probe_ptr != NULL &&
  330                                     dtrace_pid_probe_ptr(&regs) == 0)
  331                                         goto out;
  332                         }
  333 #endif
  334                         frame->tf_eflags &= ~PSL_T;
  335                         i = SIGTRAP;
  336                         ucode = (type == T_TRCTRAP ? TRAP_TRACE : TRAP_BRKPT);
  337                         break;
  338 
  339                 case T_ARITHTRAP:       /* arithmetic trap */
  340 #ifdef DEV_NPX
  341                         ucode = npxtrap_x87();
  342                         if (ucode == -1)
  343                                 goto userout;
  344 #else
  345                         ucode = 0;
  346 #endif
  347                         i = SIGFPE;
  348                         break;
  349 
  350                         /*
  351                          * The following two traps can happen in
  352                          * vm86 mode, and, if so, we want to handle
  353                          * them specially.
  354                          */
  355                 case T_PROTFLT:         /* general protection fault */
  356                 case T_STKFLT:          /* stack fault */
  357                         if (frame->tf_eflags & PSL_VM) {
  358                                 i = vm86_emulate((struct vm86frame *)frame);
  359                                 if (i == 0)
  360                                         goto user;
  361                                 break;
  362                         }
  363                         i = SIGBUS;
  364                         ucode = (type == T_PROTFLT) ? BUS_OBJERR : BUS_ADRERR;
  365                         break;
  366                 case T_SEGNPFLT:        /* segment not present fault */
  367                         i = SIGBUS;
  368                         ucode = BUS_ADRERR;
  369                         break;
  370                 case T_TSSFLT:          /* invalid TSS fault */
  371                         i = SIGBUS;
  372                         ucode = BUS_OBJERR;
  373                         break;
  374                 case T_ALIGNFLT:
  375                         i = SIGBUS;
  376                         ucode = BUS_ADRALN;
  377                         break;
  378                 case T_DOUBLEFLT:       /* double fault */
  379                 default:
  380                         i = SIGBUS;
  381                         ucode = BUS_OBJERR;
  382                         break;
  383 
  384                 case T_PAGEFLT:         /* page fault */
  385 
  386                         i = trap_pfault(frame, TRUE, eva);
  387 #if defined(I586_CPU) && !defined(NO_F00F_HACK)
  388                         if (i == -2) {
  389                                 /*
  390                                  * The f00f hack workaround has triggered, so
  391                                  * treat the fault as an illegal instruction 
  392                                  * (T_PRIVINFLT) instead of a page fault.
  393                                  */
  394                                 type = frame->tf_trapno = T_PRIVINFLT;
  395 
  396                                 /* Proceed as in that case. */
  397                                 ucode = ILL_PRVOPC;
  398                                 i = SIGILL;
  399                                 break;
  400                         }
  401 #endif
  402                         if (i == -1)
  403                                 goto userout;
  404                         if (i == 0)
  405                                 goto user;
  406 
  407                         if (i == SIGSEGV)
  408                                 ucode = SEGV_MAPERR;
  409                         else {
  410                                 if (prot_fault_translation == 0) {
  411                                         /*
  412                                          * Autodetect.
  413                                          * This check also covers the images
  414                                          * without the ABI-tag ELF note.
  415                                          */
  416                                         if (SV_CURPROC_ABI() == SV_ABI_FREEBSD
  417                                             && p->p_osrel >= P_OSREL_SIGSEGV) {
  418                                                 i = SIGSEGV;
  419                                                 ucode = SEGV_ACCERR;
  420                                         } else {
  421                                                 i = SIGBUS;
  422                                                 ucode = BUS_PAGE_FAULT;
  423                                         }
  424                                 } else if (prot_fault_translation == 1) {
  425                                         /*
  426                                          * Always compat mode.
  427                                          */
  428                                         i = SIGBUS;
  429                                         ucode = BUS_PAGE_FAULT;
  430                                 } else {
  431                                         /*
  432                                          * Always SIGSEGV mode.
  433                                          */
  434                                         i = SIGSEGV;
  435                                         ucode = SEGV_ACCERR;
  436                                 }
  437                         }
  438                         addr = eva;
  439                         break;
  440 
  441                 case T_DIVIDE:          /* integer divide fault */
  442                         ucode = FPE_INTDIV;
  443                         i = SIGFPE;
  444                         break;
  445 
  446 #ifdef DEV_ISA
  447                 case T_NMI:
  448 #ifdef POWERFAIL_NMI
  449 #ifndef TIMER_FREQ
  450 #  define TIMER_FREQ 1193182
  451 #endif
  452                         if (time_second - lastalert > 10) {
  453                                 log(LOG_WARNING, "NMI: power fail\n");
  454                                 sysbeep(880, hz);
  455                                 lastalert = time_second;
  456                         }
  457                         goto userout;
  458 #else /* !POWERFAIL_NMI */
  459                         /* machine/parity/power fail/"kitchen sink" faults */
  460                         if (isa_nmi(code) == 0) {
  461 #ifdef KDB
  462                                 /*
  463                                  * NMI can be hooked up to a pushbutton
  464                                  * for debugging.
  465                                  */
  466                                 if (kdb_on_nmi) {
  467                                         printf ("NMI ... going to debugger\n");
  468                                         kdb_trap(type, 0, frame);
  469                                 }
  470 #endif /* KDB */
  471                                 goto userout;
  472                         } else if (panic_on_nmi)
  473                                 panic("NMI indicates hardware failure");
  474                         goto out;
  475 #endif /* POWERFAIL_NMI */
  476 #endif /* DEV_ISA */
  477 
  478                 case T_OFLOW:           /* integer overflow fault */
  479                         ucode = FPE_INTOVF;
  480                         i = SIGFPE;
  481                         break;
  482 
  483                 case T_BOUND:           /* bounds check fault */
  484                         ucode = FPE_FLTSUB;
  485                         i = SIGFPE;
  486                         break;
  487 
  488                 case T_DNA:
  489 #ifdef DEV_NPX
  490                         KASSERT(PCB_USER_FPU(td->td_pcb),
  491                             ("kernel FPU ctx has leaked"));
  492                         /* transparent fault (due to context switch "late") */
  493                         if (npxdna())
  494                                 goto userout;
  495 #endif
  496                         uprintf("pid %d killed due to lack of floating point\n",
  497                                 p->p_pid);
  498                         i = SIGKILL;
  499                         ucode = 0;
  500                         break;
  501 
  502                 case T_FPOPFLT:         /* FPU operand fetch fault */
  503                         ucode = ILL_COPROC;
  504                         i = SIGILL;
  505                         break;
  506 
  507                 case T_XMMFLT:          /* SIMD floating-point exception */
  508 #if defined(DEV_NPX) && !defined(CPU_DISABLE_SSE) && defined(I686_CPU)
  509                         ucode = npxtrap_sse();
  510                         if (ucode == -1)
  511                                 goto userout;
  512 #else
  513                         ucode = 0;
  514 #endif
  515                         i = SIGFPE;
  516                         break;
  517 #ifdef KDTRACE_HOOKS
  518                 case T_DTRACE_RET:
  519                         enable_intr();
  520                         fill_frame_regs(frame, &regs);
  521                         if (dtrace_return_probe_ptr != NULL &&
  522                             dtrace_return_probe_ptr(&regs) == 0)
  523                                 goto out;
  524                         goto userout;
  525 #endif
  526                 }
  527         } else {
  528                 /* kernel trap */
  529 
  530                 KASSERT(cold || td->td_ucred != NULL,
  531                     ("kernel trap doesn't have ucred"));
  532                 switch (type) {
  533                 case T_PAGEFLT:                 /* page fault */
  534                         (void) trap_pfault(frame, FALSE, eva);
  535                         goto out;
  536 
  537                 case T_DNA:
  538 #ifdef DEV_NPX
  539                         if (PCB_USER_FPU(td->td_pcb))
  540                                 panic("Unregistered use of FPU in kernel");
  541                         if (npxdna())
  542                                 goto out;
  543 #endif
  544                         break;
  545 
  546                 case T_ARITHTRAP:       /* arithmetic trap */
  547                 case T_XMMFLT:          /* SIMD floating-point exception */
  548                 case T_FPOPFLT:         /* FPU operand fetch fault */
  549                         /*
  550                          * XXXKIB for now disable any FPU traps in kernel
  551                          * handler registration seems to be overkill
  552                          */
  553                         trap_fatal(frame, 0);
  554                         goto out;
  555 
  556                         /*
  557                          * The following two traps can happen in
  558                          * vm86 mode, and, if so, we want to handle
  559                          * them specially.
  560                          */
  561                 case T_PROTFLT:         /* general protection fault */
  562                 case T_STKFLT:          /* stack fault */
  563                         if (frame->tf_eflags & PSL_VM) {
  564                                 i = vm86_emulate((struct vm86frame *)frame);
  565                                 if (i != 0)
  566                                         /*
  567                                          * returns to original process
  568                                          */
  569                                         vm86_trap((struct vm86frame *)frame);
  570                                 goto out;
  571                         }
  572                         /* FALL THROUGH */
  573                 case T_SEGNPFLT:        /* segment not present fault */
  574                         if (curpcb->pcb_flags & PCB_VM86CALL)
  575                                 break;
  576 
  577                         /*
  578                          * Invalid %fs's and %gs's can be created using
  579                          * procfs or PT_SETREGS or by invalidating the
  580                          * underlying LDT entry.  This causes a fault
  581                          * in kernel mode when the kernel attempts to
  582                          * switch contexts.  Lose the bad context
  583                          * (XXX) so that we can continue, and generate
  584                          * a signal.
  585                          */
  586                         if (frame->tf_eip == (int)cpu_switch_load_gs) {
  587                                 curpcb->pcb_gs = 0;
  588 #if 0                           
  589                                 PROC_LOCK(p);
  590                                 kern_psignal(p, SIGBUS);
  591                                 PROC_UNLOCK(p);
  592 #endif                          
  593                                 goto out;
  594                         }
  595 
  596                         if (td->td_intr_nesting_level != 0)
  597                                 break;
  598 
  599                         /*
  600                          * Invalid segment selectors and out of bounds
  601                          * %eip's and %esp's can be set up in user mode.
  602                          * This causes a fault in kernel mode when the
  603                          * kernel tries to return to user mode.  We want
  604                          * to get this fault so that we can fix the
  605                          * problem here and not have to check all the
  606                          * selectors and pointers when the user changes
  607                          * them.
  608                          */
  609                         if (frame->tf_eip == (int)doreti_iret) {
  610                                 frame->tf_eip = (int)doreti_iret_fault;
  611                                 goto out;
  612                         }
  613                         if (type == T_STKFLT)
  614                                 break;
  615 
  616                         if (frame->tf_eip == (int)doreti_popl_ds) {
  617                                 frame->tf_eip = (int)doreti_popl_ds_fault;
  618                                 goto out;
  619                         }
  620                         if (frame->tf_eip == (int)doreti_popl_es) {
  621                                 frame->tf_eip = (int)doreti_popl_es_fault;
  622                                 goto out;
  623                         }
  624                         if (frame->tf_eip == (int)doreti_popl_fs) {
  625                                 frame->tf_eip = (int)doreti_popl_fs_fault;
  626                                 goto out;
  627                         }
  628                         if (curpcb->pcb_onfault != NULL) {
  629                                 frame->tf_eip =
  630                                     (int)curpcb->pcb_onfault;
  631                                 goto out;
  632                         }
  633                         break;
  634 
  635                 case T_TSSFLT:
  636                         /*
  637                          * PSL_NT can be set in user mode and isn't cleared
  638                          * automatically when the kernel is entered.  This
  639                          * causes a TSS fault when the kernel attempts to
  640                          * `iret' because the TSS link is uninitialized.  We
  641                          * want to get this fault so that we can fix the
  642                          * problem here and not every time the kernel is
  643                          * entered.
  644                          */
  645                         if (frame->tf_eflags & PSL_NT) {
  646                                 frame->tf_eflags &= ~PSL_NT;
  647                                 goto out;
  648                         }
  649                         break;
  650 
  651                 case T_TRCTRAP:  /* trace trap */
  652                         if (frame->tf_eip == (int)IDTVEC(lcall_syscall)) {
  653                                 /*
  654                                  * We've just entered system mode via the
  655                                  * syscall lcall.  Continue single stepping
  656                                  * silently until the syscall handler has
  657                                  * saved the flags.
  658                                  */
  659                                 goto out;
  660                         }
  661                         if (frame->tf_eip == (int)IDTVEC(lcall_syscall) + 1) {
  662                                 /*
  663                                  * The syscall handler has now saved the
  664                                  * flags.  Stop single stepping it.
  665                                  */
  666                                 frame->tf_eflags &= ~PSL_T;
  667                                 goto out;
  668                         }
  669                         /*
  670                          * Ignore debug register trace traps due to
  671                          * accesses in the user's address space, which
  672                          * can happen under several conditions such as
  673                          * if a user sets a watchpoint on a buffer and
  674                          * then passes that buffer to a system call.
  675                          * We still want to get TRCTRAPS for addresses
  676                          * in kernel space because that is useful when
  677                          * debugging the kernel.
  678                          */
  679                         if (user_dbreg_trap() && 
  680                            !(curpcb->pcb_flags & PCB_VM86CALL)) {
  681                                 /*
  682                                  * Reset breakpoint bits because the
  683                                  * processor doesn't
  684                                  */
  685                                 load_dr6(rdr6() & 0xfffffff0);
  686                                 goto out;
  687                         }
  688 
  689                         /*
  690                          * Malicious user code can configure a debug
  691                          * register watchpoint to trap on data access
  692                          * to the top of stack and then execute 'pop
  693                          * %ss; int 3'.  Due to exception deferral for
  694                          * 'pop %ss', the CPU will not interrupt 'int
  695                          * 3' to raise the DB# exception for the debug
  696                          * register but will postpone the DB# until
  697                          * execution of the first instruction of the
  698                          * BP# handler (in kernel mode).  Normally the
  699                          * previous check would ignore DB# exceptions
  700                          * for watchpoints on user addresses raised in
  701                          * kernel mode.  However, some CPU errata
  702                          * include cases where DB# exceptions do not
  703                          * properly set bits in %dr6, e.g. Haswell
  704                          * HSD23 and Skylake-X SKZ24.
  705                          *
  706                          * A deferred DB# can also be raised on the
  707                          * first instructions of system call entry
  708                          * points or single-step traps via similar use
  709                          * of 'pop %ss' or 'mov xxx, %ss'.
  710                          */
  711                         if (frame->tf_eip ==
  712                             (uintptr_t)IDTVEC(int0x80_syscall) ||
  713                             frame->tf_eip == (uintptr_t)IDTVEC(bpt) ||
  714                             frame->tf_eip == (uintptr_t)IDTVEC(dbg))
  715                                 return;
  716                         /*
  717                          * FALLTHROUGH (TRCTRAP kernel mode, kernel address)
  718                          */
  719                 case T_BPTFLT:
  720                         /*
  721                          * If KDB is enabled, let it handle the debugger trap.
  722                          * Otherwise, debugger traps "can't happen".
  723                          */
  724 #ifdef KDB
  725                         if (kdb_trap(type, 0, frame))
  726                                 goto out;
  727 #endif
  728                         break;
  729 
  730 #ifdef DEV_ISA
  731                 case T_NMI:
  732 #ifdef POWERFAIL_NMI
  733                         if (time_second - lastalert > 10) {
  734                                 log(LOG_WARNING, "NMI: power fail\n");
  735                                 sysbeep(880, hz);
  736                                 lastalert = time_second;
  737                         }
  738                         goto out;
  739 #else /* !POWERFAIL_NMI */
  740                         /* machine/parity/power fail/"kitchen sink" faults */
  741                         if (isa_nmi(code) == 0) {
  742 #ifdef KDB
  743                                 /*
  744                                  * NMI can be hooked up to a pushbutton
  745                                  * for debugging.
  746                                  */
  747                                 if (kdb_on_nmi) {
  748                                         printf ("NMI ... going to debugger\n");
  749                                         kdb_trap(type, 0, frame);
  750                                 }
  751 #endif /* KDB */
  752                                 goto out;
  753                         } else if (panic_on_nmi == 0)
  754                                 goto out;
  755                         /* FALLTHROUGH */
  756 #endif /* POWERFAIL_NMI */
  757 #endif /* DEV_ISA */
  758                 }
  759 
  760                 trap_fatal(frame, eva);
  761                 goto out;
  762         }
  763 
  764         /* Translate fault for emulators (e.g. Linux) */
  765         if (*p->p_sysent->sv_transtrap)
  766                 i = (*p->p_sysent->sv_transtrap)(i, type);
  767 
  768         ksiginfo_init_trap(&ksi);
  769         ksi.ksi_signo = i;
  770         ksi.ksi_code = ucode;
  771         ksi.ksi_addr = (void *)addr;
  772         ksi.ksi_trapno = type;
  773         if (uprintf_signal) {
  774                 uprintf("pid %d comm %s: signal %d err %x code %d type %d "
  775                     "addr 0x%x esp 0x%08x eip 0x%08x "
  776                     "<%02x %02x %02x %02x %02x %02x %02x %02x>\n",
  777                     p->p_pid, p->p_comm, i, frame->tf_err, ucode, type, addr,
  778                     frame->tf_esp, frame->tf_eip,
  779                     fubyte((void *)(frame->tf_eip + 0)),
  780                     fubyte((void *)(frame->tf_eip + 1)),
  781                     fubyte((void *)(frame->tf_eip + 2)),
  782                     fubyte((void *)(frame->tf_eip + 3)),
  783                     fubyte((void *)(frame->tf_eip + 4)),
  784                     fubyte((void *)(frame->tf_eip + 5)),
  785                     fubyte((void *)(frame->tf_eip + 6)),
  786                     fubyte((void *)(frame->tf_eip + 7)));
  787         }
  788         KASSERT((read_eflags() & PSL_I) != 0, ("interrupts disabled"));
  789         trapsignal(td, &ksi);
  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", (u_long)eva);
  797                 uprintf("\n");
  798         }
  799 #endif
  800 
  801 user:
  802         userret(td, frame);
  803         KASSERT(PCB_USER_FPU(td->td_pcb),
  804             ("Return from trap with kernel FPU ctx leaked"));
  805 userout:
  806 out:
  807         return;
  808 }
  809 
  810 static int
  811 trap_pfault(frame, usermode, eva)
  812         struct trapframe *frame;
  813         int usermode;
  814         vm_offset_t eva;
  815 {
  816         vm_offset_t va;
  817         struct vmspace *vm;
  818         vm_map_t map;
  819         int rv = 0;
  820         vm_prot_t ftype;
  821         struct thread *td = curthread;
  822         struct proc *p = td->td_proc;
  823 
  824         if (__predict_false((td->td_pflags & TDP_NOFAULTING) != 0)) {
  825                 /*
  826                  * Due to both processor errata and lazy TLB invalidation when
  827                  * access restrictions are removed from virtual pages, memory
  828                  * accesses that are allowed by the physical mapping layer may
  829                  * nonetheless cause one spurious page fault per virtual page. 
  830                  * When the thread is executing a "no faulting" section that
  831                  * is bracketed by vm_fault_{disable,enable}_pagefaults(),
  832                  * every page fault is treated as a spurious page fault,
  833                  * unless it accesses the same virtual address as the most
  834                  * recent page fault within the same "no faulting" section.
  835                  */
  836                 if (td->td_md.md_spurflt_addr != eva ||
  837                     (td->td_pflags & TDP_RESETSPUR) != 0) {
  838                         /*
  839                          * Do nothing to the TLB.  A stale TLB entry is
  840                          * flushed automatically by a page fault.
  841                          */
  842                         td->td_md.md_spurflt_addr = eva;
  843                         td->td_pflags &= ~TDP_RESETSPUR;
  844                         return (0);
  845                 }
  846         } else {
  847                 /*
  848                  * If we get a page fault while in a critical section, then
  849                  * it is most likely a fatal kernel page fault.  The kernel
  850                  * is already going to panic trying to get a sleep lock to
  851                  * do the VM lookup, so just consider it a fatal trap so the
  852                  * kernel can print out a useful trap message and even get
  853                  * to the debugger.
  854                  *
  855                  * If we get a page fault while holding a non-sleepable
  856                  * lock, then it is most likely a fatal kernel page fault.
  857                  * If WITNESS is enabled, then it's going to whine about
  858                  * bogus LORs with various VM locks, so just skip to the
  859                  * fatal trap handling directly.
  860                  */
  861                 if (td->td_critnest != 0 ||
  862                     WITNESS_CHECK(WARN_SLEEPOK | WARN_GIANTOK, NULL,
  863                     "Kernel page fault") != 0) {
  864                         trap_fatal(frame, eva);
  865                         return (-1);
  866                 }
  867         }
  868         va = trunc_page(eva);
  869         if (va >= KERNBASE) {
  870                 /*
  871                  * Don't allow user-mode faults in kernel address space.
  872                  * An exception:  if the faulting address is the invalid
  873                  * instruction entry in the IDT, then the Intel Pentium
  874                  * F00F bug workaround was triggered, and we need to
  875                  * treat it is as an illegal instruction, and not a page
  876                  * fault.
  877                  */
  878 #if defined(I586_CPU) && !defined(NO_F00F_HACK)
  879                 if ((eva == (unsigned int)&idt[6]) && has_f00f_bug)
  880                         return (-2);
  881 #endif
  882                 if (usermode)
  883                         goto nogo;
  884 
  885                 map = kernel_map;
  886         } else {
  887                 /*
  888                  * This is a fault on non-kernel virtual memory.  If either
  889                  * p or p->p_vmspace is NULL, then the fault is fatal.
  890                  */
  891                 if (p == NULL || (vm = p->p_vmspace) == NULL)
  892                         goto nogo;
  893 
  894                 map = &vm->vm_map;
  895 
  896                 /*
  897                  * When accessing a user-space address, kernel must be
  898                  * ready to accept the page fault, and provide a
  899                  * handling routine.  Since accessing the address
  900                  * without the handler is a bug, do not try to handle
  901                  * it normally, and panic immediately.
  902                  */
  903                 if (!usermode && (td->td_intr_nesting_level != 0 ||
  904                     curpcb->pcb_onfault == NULL)) {
  905                         trap_fatal(frame, eva);
  906                         return (-1);
  907                 }
  908         }
  909 
  910         /*
  911          * If the trap was caused by errant bits in the PTE then panic.
  912          */
  913         if (frame->tf_err & PGEX_RSV) {
  914                 trap_fatal(frame, eva);
  915                 return (-1);
  916         }
  917 
  918         /*
  919          * PGEX_I is defined only if the execute disable bit capability is
  920          * supported and enabled.
  921          */
  922         if (frame->tf_err & PGEX_W)
  923                 ftype = VM_PROT_WRITE;
  924 #if defined(PAE) || defined(PAE_TABLES)
  925         else if ((frame->tf_err & PGEX_I) && pg_nx != 0)
  926                 ftype = VM_PROT_EXECUTE;
  927 #endif
  928         else
  929                 ftype = VM_PROT_READ;
  930 
  931         if (map != kernel_map) {
  932                 /*
  933                  * Keep swapout from messing with us during this
  934                  *      critical time.
  935                  */
  936                 PROC_LOCK(p);
  937                 ++p->p_lock;
  938                 PROC_UNLOCK(p);
  939 
  940                 /* Fault in the user page: */
  941                 rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
  942 
  943                 PROC_LOCK(p);
  944                 --p->p_lock;
  945                 PROC_UNLOCK(p);
  946         } else {
  947                 /*
  948                  * Don't have to worry about process locking or stacks in the
  949                  * kernel.
  950                  */
  951                 rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
  952         }
  953         if (rv == KERN_SUCCESS) {
  954 #ifdef HWPMC_HOOKS
  955                 if (ftype == VM_PROT_READ || ftype == VM_PROT_WRITE) {
  956                         PMC_SOFT_CALL_TF( , , page_fault, all, frame);
  957                         if (ftype == VM_PROT_READ)
  958                                 PMC_SOFT_CALL_TF( , , page_fault, read,
  959                                     frame);
  960                         else
  961                                 PMC_SOFT_CALL_TF( , , page_fault, write,
  962                                     frame);
  963                 }
  964 #endif
  965                 return (0);
  966         }
  967 nogo:
  968         if (!usermode) {
  969                 if (td->td_intr_nesting_level == 0 &&
  970                     curpcb->pcb_onfault != NULL) {
  971                         frame->tf_eip = (int)curpcb->pcb_onfault;
  972                         return (0);
  973                 }
  974                 trap_fatal(frame, eva);
  975                 return (-1);
  976         }
  977         return ((rv == KERN_PROTECTION_FAILURE) ? SIGBUS : SIGSEGV);
  978 }
  979 
  980 static void
  981 trap_fatal(frame, eva)
  982         struct trapframe *frame;
  983         vm_offset_t eva;
  984 {
  985         int code, ss, esp;
  986         u_int type;
  987         struct soft_segment_descriptor softseg;
  988         char *msg;
  989 #ifdef KDB
  990         bool handled;
  991 #endif
  992 
  993         code = frame->tf_err;
  994         type = frame->tf_trapno;
  995         sdtossd(&gdt[IDXSEL(frame->tf_cs & 0xffff)].sd, &softseg);
  996 
  997         if (type <= MAX_TRAP_MSG)
  998                 msg = trap_msg[type];
  999         else
 1000                 msg = "UNKNOWN";
 1001         printf("\n\nFatal trap %d: %s while in %s mode\n", type, msg,
 1002             frame->tf_eflags & PSL_VM ? "vm86" :
 1003             ISPL(frame->tf_cs) == SEL_UPL ? "user" : "kernel");
 1004 #ifdef SMP
 1005         /* two separate prints in case of a trap on an unmapped page */
 1006         printf("cpuid = %d; ", PCPU_GET(cpuid));
 1007         printf("apic id = %02x\n", PCPU_GET(apic_id));
 1008 #endif
 1009         if (type == T_PAGEFLT) {
 1010                 printf("fault virtual address   = 0x%x\n", eva);
 1011                 printf("fault code              = %s %s%s, %s\n",
 1012                         code & PGEX_U ? "user" : "supervisor",
 1013                         code & PGEX_W ? "write" : "read",
 1014 #if defined(PAE) || defined(PAE_TABLES)
 1015                         pg_nx != 0 ?
 1016                         (code & PGEX_I ? " instruction" : " data") :
 1017 #endif
 1018                         "",
 1019                         code & PGEX_RSV ? "reserved bits in PTE" :
 1020                         code & PGEX_P ? "protection violation" : "page not present");
 1021         }
 1022         printf("instruction pointer     = 0x%x:0x%x\n",
 1023                frame->tf_cs & 0xffff, frame->tf_eip);
 1024         if ((ISPL(frame->tf_cs) == SEL_UPL) || (frame->tf_eflags & PSL_VM)) {
 1025                 ss = frame->tf_ss & 0xffff;
 1026                 esp = frame->tf_esp;
 1027         } else {
 1028                 ss = GSEL(GDATA_SEL, SEL_KPL);
 1029                 esp = (int)&frame->tf_esp;
 1030         }
 1031         printf("stack pointer           = 0x%x:0x%x\n", ss, esp);
 1032         printf("frame pointer           = 0x%x:0x%x\n", ss, frame->tf_ebp);
 1033         printf("code segment            = base 0x%x, limit 0x%x, type 0x%x\n",
 1034                softseg.ssd_base, softseg.ssd_limit, softseg.ssd_type);
 1035         printf("                        = DPL %d, pres %d, def32 %d, gran %d\n",
 1036                softseg.ssd_dpl, softseg.ssd_p, softseg.ssd_def32,
 1037                softseg.ssd_gran);
 1038         printf("processor eflags        = ");
 1039         if (frame->tf_eflags & PSL_T)
 1040                 printf("trace trap, ");
 1041         if (frame->tf_eflags & PSL_I)
 1042                 printf("interrupt enabled, ");
 1043         if (frame->tf_eflags & PSL_NT)
 1044                 printf("nested task, ");
 1045         if (frame->tf_eflags & PSL_RF)
 1046                 printf("resume, ");
 1047         if (frame->tf_eflags & PSL_VM)
 1048                 printf("vm86, ");
 1049         printf("IOPL = %d\n", (frame->tf_eflags & PSL_IOPL) >> 12);
 1050         printf("current process         = %d (%s)\n",
 1051             curproc->p_pid, curthread->td_name);
 1052 
 1053 #ifdef KDB
 1054         if (debugger_on_panic) {
 1055                 kdb_why = KDB_WHY_TRAP;
 1056                 frame->tf_err = eva;    /* smuggle fault address to ddb */
 1057                 handled = kdb_trap(type, 0, frame);
 1058                 frame->tf_err = code;   /* restore error code */
 1059                 kdb_why = KDB_WHY_UNSET;
 1060                 if (handled)
 1061                         return;
 1062         }
 1063 #endif
 1064         printf("trap number             = %d\n", type);
 1065         if (type <= MAX_TRAP_MSG)
 1066                 panic("%s", trap_msg[type]);
 1067         else
 1068                 panic("unknown/reserved trap");
 1069 }
 1070 
 1071 /*
 1072  * Double fault handler. Called when a fault occurs while writing
 1073  * a frame for a trap/exception onto the stack. This usually occurs
 1074  * when the stack overflows (such is the case with infinite recursion,
 1075  * for example).
 1076  *
 1077  * XXX Note that the current PTD gets replaced by IdlePTD when the
 1078  * task switch occurs. This means that the stack that was active at
 1079  * the time of the double fault is not available at <kstack> unless
 1080  * the machine was idle when the double fault occurred. The downside
 1081  * of this is that "trace <ebp>" in ddb won't work.
 1082  */
 1083 void
 1084 dblfault_handler()
 1085 {
 1086 #ifdef KDTRACE_HOOKS
 1087         if (dtrace_doubletrap_func != NULL)
 1088                 (*dtrace_doubletrap_func)();
 1089 #endif
 1090         printf("\nFatal double fault:\n");
 1091         printf("eip = 0x%x\n", PCPU_GET(common_tss.tss_eip));
 1092         printf("esp = 0x%x\n", PCPU_GET(common_tss.tss_esp));
 1093         printf("ebp = 0x%x\n", PCPU_GET(common_tss.tss_ebp));
 1094 #ifdef SMP
 1095         /* two separate prints in case of a trap on an unmapped page */
 1096         printf("cpuid = %d; ", PCPU_GET(cpuid));
 1097         printf("apic id = %02x\n", PCPU_GET(apic_id));
 1098 #endif
 1099         panic("double fault");
 1100 }
 1101 
 1102 int
 1103 cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
 1104 {
 1105         struct proc *p;
 1106         struct trapframe *frame;
 1107         caddr_t params;
 1108         long tmp;
 1109         int error;
 1110 
 1111         p = td->td_proc;
 1112         frame = td->td_frame;
 1113 
 1114         params = (caddr_t)frame->tf_esp + sizeof(int);
 1115         sa->code = frame->tf_eax;
 1116 
 1117         /*
 1118          * Need to check if this is a 32 bit or 64 bit syscall.
 1119          */
 1120         if (sa->code == SYS_syscall) {
 1121                 /*
 1122                  * Code is first argument, followed by actual args.
 1123                  */
 1124                 error = fueword(params, &tmp);
 1125                 if (error == -1)
 1126                         return (EFAULT);
 1127                 sa->code = tmp;
 1128                 params += sizeof(int);
 1129         } else if (sa->code == SYS___syscall) {
 1130                 /*
 1131                  * Like syscall, but code is a quad, so as to maintain
 1132                  * quad alignment for the rest of the arguments.
 1133                  */
 1134                 error = fueword(params, &tmp);
 1135                 if (error == -1)
 1136                         return (EFAULT);
 1137                 sa->code = tmp;
 1138                 params += sizeof(quad_t);
 1139         }
 1140 
 1141         if (p->p_sysent->sv_mask)
 1142                 sa->code &= p->p_sysent->sv_mask;
 1143         if (sa->code >= p->p_sysent->sv_size)
 1144                 sa->callp = &p->p_sysent->sv_table[0];
 1145         else
 1146                 sa->callp = &p->p_sysent->sv_table[sa->code];
 1147         sa->narg = sa->callp->sy_narg;
 1148 
 1149         if (params != NULL && sa->narg != 0)
 1150                 error = copyin(params, (caddr_t)sa->args,
 1151                     (u_int)(sa->narg * sizeof(int)));
 1152         else
 1153                 error = 0;
 1154 
 1155         if (error == 0) {
 1156                 td->td_retval[0] = 0;
 1157                 td->td_retval[1] = frame->tf_edx;
 1158         }
 1159                 
 1160         return (error);
 1161 }
 1162 
 1163 #include "../../kern/subr_syscall.c"
 1164 
 1165 /*
 1166  * syscall - system call request C handler.  A system call is
 1167  * essentially treated as a trap by reusing the frame layout.
 1168  */
 1169 void
 1170 syscall(struct trapframe *frame)
 1171 {
 1172         struct thread *td;
 1173         struct syscall_args sa;
 1174         register_t orig_tf_eflags;
 1175         int error;
 1176         ksiginfo_t ksi;
 1177 
 1178 #ifdef DIAGNOSTIC
 1179         if (ISPL(frame->tf_cs) != SEL_UPL) {
 1180                 panic("syscall");
 1181                 /* NOT REACHED */
 1182         }
 1183 #endif
 1184         orig_tf_eflags = frame->tf_eflags;
 1185 
 1186         td = curthread;
 1187         td->td_frame = frame;
 1188 
 1189         error = syscallenter(td, &sa);
 1190 
 1191         /*
 1192          * Traced syscall.
 1193          */
 1194         if ((orig_tf_eflags & PSL_T) && !(orig_tf_eflags & PSL_VM)) {
 1195                 frame->tf_eflags &= ~PSL_T;
 1196                 ksiginfo_init_trap(&ksi);
 1197                 ksi.ksi_signo = SIGTRAP;
 1198                 ksi.ksi_code = TRAP_TRACE;
 1199                 ksi.ksi_addr = (void *)frame->tf_eip;
 1200                 trapsignal(td, &ksi);
 1201         }
 1202 
 1203         KASSERT(PCB_USER_FPU(td->td_pcb),
 1204             ("System call %s returning with kernel FPU ctx leaked",
 1205              syscallname(td->td_proc, sa.code)));
 1206         KASSERT(td->td_pcb->pcb_save == get_pcb_user_save_td(td),
 1207             ("System call %s returning with mangled pcb_save",
 1208              syscallname(td->td_proc, sa.code)));
 1209 
 1210         syscallret(td, error, &sa);
 1211 }

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