text: /*-
   * Copyright (C) 1994, David Greenman
   * Copyright (c) 1990, 1993
   *	The Regents of the University of California.  All rights reserved.
   *
   * This code is derived from software contributed to Berkeley by
   * the University of Utah, and William Jolitz.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *	This product includes software developed by the University of
   *	California, Berkeley and its contributors.
   * 4. Neither the name of the University nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   *	from: @(#)trap.c	7.4 (Berkeley) 5/13/91
   */
  
  #include <sys/cdefs.h>
  __FBSDID("$FreeBSD: soc2013/dpl/head/sys/i386/i386/trap.c 252530 2013-06-03 17:40:05Z kib $");
  
  /*
   * 386 Trap and System call handling
   */
  
  #include "opt_clock.h"
  #include "opt_cpu.h"
  #include "opt_hwpmc_hooks.h"
  #include "opt_isa.h"
  #include "opt_kdb.h"
  #include "opt_kdtrace.h"
  #include "opt_npx.h"
  #include "opt_trap.h"
  
  #include <sys/param.h>
  #include <sys/bus.h>
  #include <sys/systm.h>
  #include <sys/proc.h>
  #include <sys/pioctl.h>
  #include <sys/ptrace.h>
  #include <sys/kdb.h>
  #include <sys/kernel.h>
  #include <sys/ktr.h>
  #include <sys/lock.h>
  #include <sys/mutex.h>
  #include <sys/resourcevar.h>
  #include <sys/signalvar.h>
  #include <sys/syscall.h>
  #include <sys/sysctl.h>
  #include <sys/sysent.h>
  #include <sys/uio.h>
  #include <sys/vmmeter.h>
  #ifdef HWPMC_HOOKS
  #include <sys/pmckern.h>
  PMC_SOFT_DEFINE( , , page_fault, all);
  PMC_SOFT_DEFINE( , , page_fault, read);
  PMC_SOFT_DEFINE( , , page_fault, write);
  #endif
  #include <security/audit/audit.h>
  
  #include <vm/vm.h>
  #include <vm/vm_param.h>
  #include <vm/pmap.h>
  #include <vm/vm_kern.h>
  #include <vm/vm_map.h>
  #include <vm/vm_page.h>
  #include <vm/vm_extern.h>
  
  #include <machine/cpu.h>
  #include <machine/intr_machdep.h>
  #include <x86/mca.h>
  #include <machine/md_var.h>
  #include <machine/pcb.h>
  #ifdef SMP
  #include <machine/smp.h>
  #endif
  #include <machine/tss.h>
  #include <machine/vm86.h>
  
  #ifdef POWERFAIL_NMI
  #include <sys/syslog.h>
  #include <machine/clock.h>
  #endif
  
  #ifdef KDTRACE_HOOKS
  #include <sys/dtrace_bsd.h>
  
  /*
   * This is a hook which is initialised by the dtrace module
   * to handle traps which might occur during DTrace probe
   * execution.
   */
  dtrace_trap_func_t	dtrace_trap_func;
  
  dtrace_doubletrap_func_t	dtrace_doubletrap_func;
  
  /*
   * This is a hook which is initialised by the systrace module
   * when it is loaded. This keeps the DTrace syscall provider
   * implementation opaque. 
   */
  systrace_probe_func_t	systrace_probe_func;
  
  /*
   * These hooks are necessary for the pid, usdt and fasttrap providers.
   */
  dtrace_fasttrap_probe_ptr_t	dtrace_fasttrap_probe_ptr;
  dtrace_pid_probe_ptr_t		dtrace_pid_probe_ptr;
  dtrace_return_probe_ptr_t	dtrace_return_probe_ptr;
  #endif
  
  extern void trap(struct trapframe *frame);
  extern void syscall(struct trapframe *frame);
  
  static int trap_pfault(struct trapframe *, int, vm_offset_t);
  static void trap_fatal(struct trapframe *, vm_offset_t);
  void dblfault_handler(void);
  
  extern inthand_t IDTVEC(lcall_syscall);
  
  #define MAX_TRAP_MSG		33
  static char *trap_msg[] = {
  	"",					/*  0 unused */
  	"privileged instruction fault",		/*  1 T_PRIVINFLT */
  	"",					/*  2 unused */
  	"breakpoint instruction fault",		/*  3 T_BPTFLT */
  	"",					/*  4 unused */
  	"",					/*  5 unused */
  	"arithmetic trap",			/*  6 T_ARITHTRAP */
  	"",					/*  7 unused */
  	"",					/*  8 unused */
  	"general protection fault",		/*  9 T_PROTFLT */
  	"trace trap",				/* 10 T_TRCTRAP */
  	"",					/* 11 unused */
  	"page fault",				/* 12 T_PAGEFLT */
  	"",					/* 13 unused */
  	"alignment fault",			/* 14 T_ALIGNFLT */
  	"",					/* 15 unused */
  	"",					/* 16 unused */
  	"",					/* 17 unused */
  	"integer divide fault",			/* 18 T_DIVIDE */
  	"non-maskable interrupt trap",		/* 19 T_NMI */
  	"overflow trap",			/* 20 T_OFLOW */
  	"FPU bounds check fault",		/* 21 T_BOUND */
  	"FPU device not available",		/* 22 T_DNA */
  	"double fault",				/* 23 T_DOUBLEFLT */
  	"FPU operand fetch fault",		/* 24 T_FPOPFLT */
  	"invalid TSS fault",			/* 25 T_TSSFLT */
  	"segment not present fault",		/* 26 T_SEGNPFLT */
  	"stack fault",				/* 27 T_STKFLT */
  	"machine check trap",			/* 28 T_MCHK */
  	"SIMD floating-point exception",	/* 29 T_XMMFLT */
  	"reserved (unknown) fault",		/* 30 T_RESERVED */
  	"",					/* 31 unused (reserved) */
  	"DTrace pid return trap",               /* 32 T_DTRACE_RET */
  	"DTrace fasttrap probe trap",           /* 33 T_DTRACE_PROBE */
  
  };
  
  #if defined(I586_CPU) && !defined(NO_F00F_HACK)
  extern int has_f00f_bug;
  #endif
  
  #ifdef KDB
  static int kdb_on_nmi = 1;
  SYSCTL_INT(_machdep, OID_AUTO, kdb_on_nmi, CTLFLAG_RW,
  	&kdb_on_nmi, 0, "Go to KDB on NMI");
  TUNABLE_INT("machdep.kdb_on_nmi", &kdb_on_nmi);
  #endif
  static int panic_on_nmi = 1;
  SYSCTL_INT(_machdep, OID_AUTO, panic_on_nmi, CTLFLAG_RW,
  	&panic_on_nmi, 0, "Panic on NMI");
  TUNABLE_INT("machdep.panic_on_nmi", &panic_on_nmi);
  static int prot_fault_translation = 0;
  SYSCTL_INT(_machdep, OID_AUTO, prot_fault_translation, CTLFLAG_RW,
  	&prot_fault_translation, 0, "Select signal to deliver on protection fault");
  static int uprintf_signal;
  SYSCTL_INT(_machdep, OID_AUTO, uprintf_signal, CTLFLAG_RW,
      &uprintf_signal, 0,
      "Print debugging information on trap signal to ctty");
  
  /*
   * Exception, fault, and trap interface to the FreeBSD kernel.
   * This common code is called from assembly language IDT gate entry
   * routines that prepare a suitable stack frame, and restore this
   * frame after the exception has been processed.
   */
  
  void
  trap(struct trapframe *frame)
  {
  	struct thread *td = curthread;
  	struct proc *p = td->td_proc;
  	int i = 0, ucode = 0, code;
  	u_int type;
  	register_t addr = 0;
  	vm_offset_t eva;
  	ksiginfo_t ksi;
  #ifdef POWERFAIL_NMI
  	static int lastalert = 0;
  #endif
  
  	PCPU_INC(cnt.v_trap);
  	type = frame->tf_trapno;
  
  #ifdef SMP
  	/* Handler for NMI IPIs used for stopping CPUs. */
  	if (type == T_NMI) {
  	         if (ipi_nmi_handler() == 0)
  	                   goto out;
  	}
  #endif /* SMP */
  
  #ifdef KDB
  	if (kdb_active) {
  		kdb_reenter();
  		goto out;
  	}
  #endif
  
  	if (type == T_RESERVED) {
  		trap_fatal(frame, 0);
  		goto out;
  	}
  
  #ifdef	HWPMC_HOOKS
  	/*
  	 * CPU PMCs interrupt using an NMI so we check for that first.
  	 * If the HWPMC module is active, 'pmc_hook' will point to
  	 * the function to be called.  A return value of '1' from the
  	 * hook means that the NMI was handled by it and that we can
  	 * return immediately.
  	 */
  	if (type == T_NMI && pmc_intr &&
  	    (*pmc_intr)(PCPU_GET(cpuid), frame))
  	    goto out;
  #endif
  
  	if (type == T_MCHK) {
  		mca_intr();
  		goto out;
  	}
  
  #ifdef KDTRACE_HOOKS
  	/*
  	 * A trap can occur while DTrace executes a probe. Before
  	 * executing the probe, DTrace blocks re-scheduling and sets
  	 * a flag in it's per-cpu flags to indicate that it doesn't
  	 * want to fault. On returning from the probe, the no-fault
  	 * flag is cleared and finally re-scheduling is enabled.
  	 *
  	 * If the DTrace kernel module has registered a trap handler,
  	 * call it and if it returns non-zero, assume that it has
  	 * handled the trap and modified the trap frame so that this
  	 * function can return normally.
  	 */
  	if (type == T_DTRACE_PROBE || type == T_DTRACE_RET ||
  	    type == T_BPTFLT) {
  		struct reg regs;
  
  		fill_frame_regs(frame, &regs);
  		if (type == T_DTRACE_PROBE &&
  		    dtrace_fasttrap_probe_ptr != NULL &&
  		    dtrace_fasttrap_probe_ptr(&regs) == 0)
  			goto out;
  		if (type == T_BPTFLT &&
  		    dtrace_pid_probe_ptr != NULL &&
  		    dtrace_pid_probe_ptr(&regs) == 0)
  			goto out;
  		if (type == T_DTRACE_RET &&
  		    dtrace_return_probe_ptr != NULL &&
  		    dtrace_return_probe_ptr(&regs) == 0)
  			goto out;
  	}
  	if ((type == T_PROTFLT || type == T_PAGEFLT) &&
  	    dtrace_trap_func != NULL && (*dtrace_trap_func)(frame, type))
  		goto out;
  #endif
  
  	if ((frame->tf_eflags & PSL_I) == 0) {
  		/*
  		 * Buggy application or kernel code has disabled
  		 * interrupts and then trapped.  Enabling interrupts
  		 * now is wrong, but it is better than running with
  		 * interrupts disabled until they are accidentally
  		 * enabled later.
  		 */
  		if (ISPL(frame->tf_cs) == SEL_UPL || (frame->tf_eflags & PSL_VM))
  			uprintf(
  			    "pid %ld (%s): trap %d with interrupts disabled\n",
  			    (long)curproc->p_pid, curthread->td_name, type);
  		else if (type != T_NMI && type != T_BPTFLT &&
  		    type != T_TRCTRAP &&
  		    frame->tf_eip != (int)cpu_switch_load_gs) {
  			/*
  			 * XXX not quite right, since this may be for a
  			 * multiple fault in user mode.
  			 */
  			printf("kernel trap %d with interrupts disabled\n",
  			    type);
  			/*
  			 * Page faults need interrupts disabled until later,
  			 * and we shouldn't enable interrupts while holding
  			 * a spin lock.
  			 */
  			if (type != T_PAGEFLT &&
  			    td->td_md.md_spinlock_count == 0)
  				enable_intr();
  		}
  	}
  	eva = 0;
  	code = frame->tf_err;
  	if (type == T_PAGEFLT) {
  		/*
  		 * For some Cyrix CPUs, %cr2 is clobbered by
  		 * interrupts.  This problem is worked around by using
  		 * an interrupt gate for the pagefault handler.  We
  		 * are finally ready to read %cr2 and conditionally
  		 * reenable interrupts.  If we hold a spin lock, then
  		 * we must not reenable interrupts.  This might be a
  		 * spurious page fault.
  		 */
  		eva = rcr2();
  		if (td->td_md.md_spinlock_count == 0)
  			enable_intr();
  	}
  
          if ((ISPL(frame->tf_cs) == SEL_UPL) ||
  	    ((frame->tf_eflags & PSL_VM) && 
  		!(curpcb->pcb_flags & PCB_VM86CALL))) {
  		/* user trap */
  
  		td->td_pticks = 0;
  		td->td_frame = frame;
  		addr = frame->tf_eip;
  		if (td->td_ucred != p->p_ucred) 
  			cred_update_thread(td);
  
  		switch (type) {
  		case T_PRIVINFLT:	/* privileged instruction fault */
  			i = SIGILL;
  			ucode = ILL_PRVOPC;
  			break;
  
  		case T_BPTFLT:		/* bpt instruction fault */
  		case T_TRCTRAP:		/* trace trap */
  			enable_intr();
  			frame->tf_eflags &= ~PSL_T;
  			i = SIGTRAP;
  			ucode = (type == T_TRCTRAP ? TRAP_TRACE : TRAP_BRKPT);
  			break;
  
  		case T_ARITHTRAP:	/* arithmetic trap */
  #ifdef DEV_NPX
  			ucode = npxtrap_x87();
  			if (ucode == -1)
  				goto userout;
  #else
  			ucode = 0;
  #endif
  			i = SIGFPE;
  			break;
  
  			/*
  			 * The following two traps can happen in
  			 * vm86 mode, and, if so, we want to handle
  			 * them specially.
  			 */
  		case T_PROTFLT:		/* general protection fault */
  		case T_STKFLT:		/* stack fault */
  			if (frame->tf_eflags & PSL_VM) {
  				i = vm86_emulate((struct vm86frame *)frame);
  				if (i == 0)
  					goto user;
  				break;
  			}
  			i = SIGBUS;
  			ucode = (type == T_PROTFLT) ? BUS_OBJERR : BUS_ADRERR;
  			break;
  		case T_SEGNPFLT:	/* segment not present fault */
  			i = SIGBUS;
  			ucode = BUS_ADRERR;
  			break;
  		case T_TSSFLT:		/* invalid TSS fault */
  			i = SIGBUS;
  			ucode = BUS_OBJERR;
  			break;
  		case T_DOUBLEFLT:	/* double fault */
  		default:
  			i = SIGBUS;
  			ucode = BUS_OBJERR;
  			break;
  
  		case T_PAGEFLT:		/* page fault */
  
  			i = trap_pfault(frame, TRUE, eva);
  #if defined(I586_CPU) && !defined(NO_F00F_HACK)
  			if (i == -2) {
  				/*
  				 * The f00f hack workaround has triggered, so
  				 * treat the fault as an illegal instruction 
  				 * (T_PRIVINFLT) instead of a page fault.
  				 */
  				type = frame->tf_trapno = T_PRIVINFLT;
  
  				/* Proceed as in that case. */
  				ucode = ILL_PRVOPC;
  				i = SIGILL;
  				break;
  			}
  #endif
  			if (i == -1)
  				goto userout;
  			if (i == 0)
  				goto user;
  
  			if (i == SIGSEGV)
  				ucode = SEGV_MAPERR;
  			else {
  				if (prot_fault_translation == 0) {
  					/*
  					 * Autodetect.
  					 * This check also covers the images
  					 * without the ABI-tag ELF note.
  					 */
  					if (SV_CURPROC_ABI() == SV_ABI_FREEBSD
  					    && p->p_osrel >= P_OSREL_SIGSEGV) {
  						i = SIGSEGV;
  						ucode = SEGV_ACCERR;
  					} else {
  						i = SIGBUS;
  						ucode = BUS_PAGE_FAULT;
  					}
  				} else if (prot_fault_translation == 1) {
  					/*
  					 * Always compat mode.
  					 */
  					i = SIGBUS;
  					ucode = BUS_PAGE_FAULT;
  				} else {
  					/*
  					 * Always SIGSEGV mode.
  					 */
  					i = SIGSEGV;
  					ucode = SEGV_ACCERR;
  				}
  			}
  			addr = eva;
  			break;
  
  		case T_DIVIDE:		/* integer divide fault */
  			ucode = FPE_INTDIV;
  			i = SIGFPE;
  			break;
  
  #ifdef DEV_ISA
  		case T_NMI:
  #ifdef POWERFAIL_NMI
  #ifndef TIMER_FREQ
  #  define TIMER_FREQ 1193182
  #endif
  			if (time_second - lastalert > 10) {
  				log(LOG_WARNING, "NMI: power fail\n");
  				sysbeep(880, hz);
  				lastalert = time_second;
  			}
  			goto userout;
  #else /* !POWERFAIL_NMI */
  			/* machine/parity/power fail/"kitchen sink" faults */
  			if (isa_nmi(code) == 0) {
  #ifdef KDB
  				/*
  				 * NMI can be hooked up to a pushbutton
  				 * for debugging.
  				 */
  				if (kdb_on_nmi) {
  					printf ("NMI ... going to debugger\n");
  					kdb_trap(type, 0, frame);
  				}
  #endif /* KDB */
  				goto userout;
  			} else if (panic_on_nmi)
  				panic("NMI indicates hardware failure");
  			break;
  #endif /* POWERFAIL_NMI */
  #endif /* DEV_ISA */
  
  		case T_OFLOW:		/* integer overflow fault */
  			ucode = FPE_INTOVF;
  			i = SIGFPE;
  			break;
  
  		case T_BOUND:		/* bounds check fault */
  			ucode = FPE_FLTSUB;
  			i = SIGFPE;
  			break;
  
  		case T_DNA:
  #ifdef DEV_NPX
  			KASSERT(PCB_USER_FPU(td->td_pcb),
  			    ("kernel FPU ctx has leaked"));
  			/* transparent fault (due to context switch "late") */
  			if (npxdna())
  				goto userout;
  #endif
  			uprintf("pid %d killed due to lack of floating point\n",
  				p->p_pid);
  			i = SIGKILL;
  			ucode = 0;
  			break;
  
  		case T_FPOPFLT:		/* FPU operand fetch fault */
  			ucode = ILL_COPROC;
  			i = SIGILL;
  			break;
  
  		case T_XMMFLT:		/* SIMD floating-point exception */
  #if defined(DEV_NPX) && !defined(CPU_DISABLE_SSE) && defined(I686_CPU)
  			ucode = npxtrap_sse();
  			if (ucode == -1)
  				goto userout;
  #else
  			ucode = 0;
  #endif
  			i = SIGFPE;
  			break;
  		}
  	} else {
  		/* kernel trap */
  
  		KASSERT(cold || td->td_ucred != NULL,
  		    ("kernel trap doesn't have ucred"));
  		switch (type) {
  		case T_PAGEFLT:			/* page fault */
  			(void) trap_pfault(frame, FALSE, eva);
  			goto out;
  
  		case T_DNA:
  #ifdef DEV_NPX
  			KASSERT(!PCB_USER_FPU(td->td_pcb),
  			    ("Unregistered use of FPU in kernel"));
  			if (npxdna())
  				goto out;
  #endif
  			break;
  
  		case T_ARITHTRAP:	/* arithmetic trap */
  		case T_XMMFLT:		/* SIMD floating-point exception */
  		case T_FPOPFLT:		/* FPU operand fetch fault */
  			/*
  			 * XXXKIB for now disable any FPU traps in kernel
  			 * handler registration seems to be overkill
  			 */
  			trap_fatal(frame, 0);
  			goto out;
  
  			/*
  			 * The following two traps can happen in
  			 * vm86 mode, and, if so, we want to handle
  			 * them specially.
  			 */
  		case T_PROTFLT:		/* general protection fault */
  		case T_STKFLT:		/* stack fault */
  			if (frame->tf_eflags & PSL_VM) {
  				i = vm86_emulate((struct vm86frame *)frame);
  				if (i != 0)
  					/*
  					 * returns to original process
  					 */
  					vm86_trap((struct vm86frame *)frame);
  				goto out;
  			}
  			if (type == T_STKFLT)
  				break;
  
  			/* FALL THROUGH */
  
  		case T_SEGNPFLT:	/* segment not present fault */
  			if (curpcb->pcb_flags & PCB_VM86CALL)
  				break;
  
  			/*
  			 * Invalid %fs's and %gs's can be created using
  			 * procfs or PT_SETREGS or by invalidating the
  			 * underlying LDT entry.  This causes a fault
  			 * in kernel mode when the kernel attempts to
  			 * switch contexts.  Lose the bad context
  			 * (XXX) so that we can continue, and generate
  			 * a signal.
  			 */
  			if (frame->tf_eip == (int)cpu_switch_load_gs) {
  				curpcb->pcb_gs = 0;
  #if 0				
  				PROC_LOCK(p);
  				kern_psignal(p, SIGBUS);
  				PROC_UNLOCK(p);
  #endif				
  				goto out;
  			}
  
  			if (td->td_intr_nesting_level != 0)
  				break;
  
  			/*
  			 * Invalid segment selectors and out of bounds
  			 * %eip's and %esp's can be set up in user mode.
  			 * This causes a fault in kernel mode when the
  			 * kernel tries to return to user mode.  We want
  			 * to get this fault so that we can fix the
  			 * problem here and not have to check all the
  			 * selectors and pointers when the user changes
  			 * them.
  			 */
  			if (frame->tf_eip == (int)doreti_iret) {
  				frame->tf_eip = (int)doreti_iret_fault;
  				goto out;
  			}
  			if (frame->tf_eip == (int)doreti_popl_ds) {
  				frame->tf_eip = (int)doreti_popl_ds_fault;
  				goto out;
  			}
  			if (frame->tf_eip == (int)doreti_popl_es) {
  				frame->tf_eip = (int)doreti_popl_es_fault;
  				goto out;
  			}
  			if (frame->tf_eip == (int)doreti_popl_fs) {
  				frame->tf_eip = (int)doreti_popl_fs_fault;
  				goto out;
  			}
  			if (curpcb->pcb_onfault != NULL) {
  				frame->tf_eip =
  				    (int)curpcb->pcb_onfault;
  				goto out;
  			}
  			break;
  
  		case T_TSSFLT:
  			/*
  			 * PSL_NT can be set in user mode and isn't cleared
  			 * automatically when the kernel is entered.  This
  			 * causes a TSS fault when the kernel attempts to
  			 * `iret' because the TSS link is uninitialized.  We
  			 * want to get this fault so that we can fix the
  			 * problem here and not every time the kernel is
  			 * entered.
  			 */
  			if (frame->tf_eflags & PSL_NT) {
  				frame->tf_eflags &= ~PSL_NT;
  				goto out;
  			}
  			break;
  
  		case T_TRCTRAP:	 /* trace trap */
  			if (frame->tf_eip == (int)IDTVEC(lcall_syscall)) {
  				/*
  				 * We've just entered system mode via the
  				 * syscall lcall.  Continue single stepping
  				 * silently until the syscall handler has
  				 * saved the flags.
  				 */
  				goto out;
  			}
  			if (frame->tf_eip == (int)IDTVEC(lcall_syscall) + 1) {
  				/*
  				 * The syscall handler has now saved the
  				 * flags.  Stop single stepping it.
  				 */
  				frame->tf_eflags &= ~PSL_T;
  				goto out;
  			}
  			/*
  			 * Ignore debug register trace traps due to
  			 * accesses in the user's address space, which
  			 * can happen under several conditions such as
  			 * if a user sets a watchpoint on a buffer and
  			 * then passes that buffer to a system call.
  			 * We still want to get TRCTRAPS for addresses
  			 * in kernel space because that is useful when
  			 * debugging the kernel.
  			 */
  			if (user_dbreg_trap() && 
  			   !(curpcb->pcb_flags & PCB_VM86CALL)) {
  				/*
  				 * Reset breakpoint bits because the
  				 * processor doesn't
  				 */
  				load_dr6(rdr6() & 0xfffffff0);
  				goto out;
  			}
  			/*
  			 * FALLTHROUGH (TRCTRAP kernel mode, kernel address)
  			 */
  		case T_BPTFLT:
  			/*
  			 * If KDB is enabled, let it handle the debugger trap.
  			 * Otherwise, debugger traps "can't happen".
  			 */
  #ifdef KDB
  			if (kdb_trap(type, 0, frame))
  				goto out;
  #endif
  			break;
  
  #ifdef DEV_ISA
  		case T_NMI:
  #ifdef POWERFAIL_NMI
  			if (time_second - lastalert > 10) {
  				log(LOG_WARNING, "NMI: power fail\n");
  				sysbeep(880, hz);
  				lastalert = time_second;
  			}
  			goto out;
  #else /* !POWERFAIL_NMI */
  			/* machine/parity/power fail/"kitchen sink" faults */
  			if (isa_nmi(code) == 0) {
  #ifdef KDB
  				/*
  				 * NMI can be hooked up to a pushbutton
  				 * for debugging.
  				 */
  				if (kdb_on_nmi) {
  					printf ("NMI ... going to debugger\n");
  					kdb_trap(type, 0, frame);
  				}
  #endif /* KDB */
  				goto out;
  			} else if (panic_on_nmi == 0)
  				goto out;
  			/* FALLTHROUGH */
  #endif /* POWERFAIL_NMI */
  #endif /* DEV_ISA */
  		}
  
  		trap_fatal(frame, eva);
  		goto out;
  	}
  
  	/* Translate fault for emulators (e.g. Linux) */
  	if (*p->p_sysent->sv_transtrap)
  		i = (*p->p_sysent->sv_transtrap)(i, type);
  
  	ksiginfo_init_trap(&ksi);
  	ksi.ksi_signo = i;
  	ksi.ksi_code = ucode;
  	ksi.ksi_addr = (void *)addr;
  	ksi.ksi_trapno = type;
  	if (uprintf_signal) {
  		uprintf("pid %d comm %s: signal %d err %x code %d type %d "
  		    "addr 0x%x esp 0x%08x eip 0x%08x "
  		    "<%02x %02x %02x %02x %02x %02x %02x %02x>\n",
  		    p->p_pid, p->p_comm, i, frame->tf_err, ucode, type, addr,
  		    frame->tf_esp, frame->tf_eip,
  		    fubyte((void *)(frame->tf_eip + 0)),
  		    fubyte((void *)(frame->tf_eip + 1)),
  		    fubyte((void *)(frame->tf_eip + 2)),
  		    fubyte((void *)(frame->tf_eip + 3)),
  		    fubyte((void *)(frame->tf_eip + 4)),
  		    fubyte((void *)(frame->tf_eip + 5)),
  		    fubyte((void *)(frame->tf_eip + 6)),
  		    fubyte((void *)(frame->tf_eip + 7)));
  	}
  	KASSERT((read_eflags() & PSL_I) != 0, ("interrupts disabled"));
  	trapsignal(td, &ksi);
  
  #ifdef DEBUG
  	if (type <= MAX_TRAP_MSG) {
  		uprintf("fatal process exception: %s",
  			trap_msg[type]);
  		if ((type == T_PAGEFLT) || (type == T_PROTFLT))
  			uprintf(", fault VA = 0x%lx", (u_long)eva);
  		uprintf("\n");
  	}
  #endif
  
  user:
  	userret(td, frame);
  	KASSERT(PCB_USER_FPU(td->td_pcb),
  	    ("Return from trap with kernel FPU ctx leaked"));
  userout:
  out:
  	return;
  }
  
  static int
  trap_pfault(frame, usermode, eva)
  	struct trapframe *frame;
  	int usermode;
  	vm_offset_t eva;
  {
  	vm_offset_t va;
  	struct vmspace *vm;
  	vm_map_t map;
  	int rv = 0;
  	vm_prot_t ftype;
  	struct thread *td = curthread;
  	struct proc *p = td->td_proc;
  
  	if (__predict_false((td->td_pflags & TDP_NOFAULTING) != 0)) {
  		/*
  		 * Due to both processor errata and lazy TLB invalidation when
  		 * access restrictions are removed from virtual pages, memory
  		 * accesses that are allowed by the physical mapping layer may
  		 * nonetheless cause one spurious page fault per virtual page. 
  		 * When the thread is executing a "no faulting" section that
  		 * is bracketed by vm_fault_{disable,enable}_pagefaults(),
  		 * every page fault is treated as a spurious page fault,
  		 * unless it accesses the same virtual address as the most
  		 * recent page fault within the same "no faulting" section.
  		 */
  		if (td->td_md.md_spurflt_addr != eva ||
  		    (td->td_pflags & TDP_RESETSPUR) != 0) {
  			/*
  			 * Do nothing to the TLB.  A stale TLB entry is
  			 * flushed automatically by a page fault.
  			 */
  			td->td_md.md_spurflt_addr = eva;
  			td->td_pflags &= ~TDP_RESETSPUR;
  			return (0);
  		}
  	} else {
  		/*
  		 * If we get a page fault while in a critical section, then
  		 * it is most likely a fatal kernel page fault.  The kernel
  		 * is already going to panic trying to get a sleep lock to
  		 * do the VM lookup, so just consider it a fatal trap so the
  		 * kernel can print out a useful trap message and even get
  		 * to the debugger.
  		 *
  		 * If we get a page fault while holding a non-sleepable
  		 * lock, then it is most likely a fatal kernel page fault.
  		 * If WITNESS is enabled, then it's going to whine about
  		 * bogus LORs with various VM locks, so just skip to the
  		 * fatal trap handling directly.
  		 */
  		if (td->td_critnest != 0 ||
  		    WITNESS_CHECK(WARN_SLEEPOK | WARN_GIANTOK, NULL,
  		    "Kernel page fault") != 0) {
  			trap_fatal(frame, eva);
  			return (-1);
  		}
  	}
  	va = trunc_page(eva);
  	if (va >= KERNBASE) {
  		/*
  		 * Don't allow user-mode faults in kernel address space.
  		 * An exception:  if the faulting address is the invalid
  		 * instruction entry in the IDT, then the Intel Pentium
  		 * F00F bug workaround was triggered, and we need to
  		 * treat it is as an illegal instruction, and not a page
  		 * fault.
  		 */
  #if defined(I586_CPU) && !defined(NO_F00F_HACK)
  		if ((eva == (unsigned int)&idt[6]) && has_f00f_bug)
  			return (-2);
  #endif
  		if (usermode)
  			goto nogo;
  
  		map = kernel_map;
  	} else {
  		/*
  		 * This is a fault on non-kernel virtual memory.  If either
  		 * p or p->p_vmspace is NULL, then the fault is fatal.
  		 */
  		if (p == NULL || (vm = p->p_vmspace) == NULL)
  			goto nogo;
  
  		map = &vm->vm_map;
  
  		/*
  		 * When accessing a user-space address, kernel must be
  		 * ready to accept the page fault, and provide a
  		 * handling routine.  Since accessing the address
  		 * without the handler is a bug, do not try to handle
  		 * it normally, and panic immediately.
  		 */
  		if (!usermode && (td->td_intr_nesting_level != 0 ||
  		    curpcb->pcb_onfault == NULL)) {
  			trap_fatal(frame, eva);
  			return (-1);
  		}
  	}
  
  	/*
  	 * PGEX_I is defined only if the execute disable bit capability is
  	 * supported and enabled.
  	 */
  	if (frame->tf_err & PGEX_W)
  		ftype = VM_PROT_WRITE;
  #ifdef PAE
  	else if ((frame->tf_err & PGEX_I) && pg_nx != 0)
  		ftype = VM_PROT_EXECUTE;
  #endif
  	else
  		ftype = VM_PROT_READ;
  
  	if (map != kernel_map) {
  		/*
  		 * Keep swapout from messing with us during this
  		 *	critical time.
  		 */
  		PROC_LOCK(p);
  		++p->p_lock;
  		PROC_UNLOCK(p);
  
  		/* Fault in the user page: */
  		rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
  
  		PROC_LOCK(p);
  		--p->p_lock;
  		PROC_UNLOCK(p);
  	} else {
  		/*
  		 * Don't have to worry about process locking or stacks in the
  		 * kernel.
  		 */
  		rv = vm_fault(map, va, ftype, VM_FAULT_NORMAL);
  	}
  	if (rv == KERN_SUCCESS) {
  #ifdef HWPMC_HOOKS
  		if (ftype == VM_PROT_READ || ftype == VM_PROT_WRITE) {
  			PMC_SOFT_CALL_TF( , , page_fault, all, frame);
  			if (ftype == VM_PROT_READ)
  				PMC_SOFT_CALL_TF( , , page_fault, read,
  				    frame);
  			else
  				PMC_SOFT_CALL_TF( , , page_fault, write,
  				    frame);
  		}
  #endif
  		return (0);
  	}
  nogo:
  	if (!usermode) {
  		if (td->td_intr_nesting_level == 0 &&
  		    curpcb->pcb_onfault != NULL) {
  			frame->tf_eip = (int)curpcb->pcb_onfault;
  			return (0);
  		}
  		trap_fatal(frame, eva);
  		return (-1);
  	}
  	return ((rv == KERN_PROTECTION_FAILURE) ? SIGBUS : SIGSEGV);
  }
  
  static void
  trap_fatal(frame, eva)
  	struct trapframe *frame;
  	vm_offset_t eva;
  {
  	int code, ss, esp;
  	u_int type;
  	struct soft_segment_descriptor softseg;
  	char *msg;
  
  	code = frame->tf_err;
  	type = frame->tf_trapno;
  	sdtossd(&gdt[IDXSEL(frame->tf_cs & 0xffff)].sd, &softseg);
  
  	if (type <= MAX_TRAP_MSG)
  		msg = trap_msg[type];
  	else
  		msg = "UNKNOWN";
  	printf("\n\nFatal trap %d: %s while in %s mode\n", type, msg,
  	    frame->tf_eflags & PSL_VM ? "vm86" :
  	    ISPL(frame->tf_cs) == SEL_UPL ? "user" : "kernel");
  #ifdef SMP
  	/* two separate prints in case of a trap on an unmapped page */
  	printf("cpuid = %d; ", PCPU_GET(cpuid));
  	printf("apic id = %02x\n", PCPU_GET(apic_id));
  #endif
  	if (type == T_PAGEFLT) {
  		printf("fault virtual address	= 0x%x\n", eva);
  		printf("fault code		= %s %s, %s\n",
  			code & PGEX_U ? "user" : "supervisor",
  			code & PGEX_W ? "write" : "read",
  			code & PGEX_P ? "protection violation" : "page not present");
  	}
  	printf("instruction pointer	= 0x%x:0x%x\n",
  	       frame->tf_cs & 0xffff, frame->tf_eip);
          if ((ISPL(frame->tf_cs) == SEL_UPL) || (frame->tf_eflags & PSL_VM)) {
  		ss = frame->tf_ss & 0xffff;
  		esp = frame->tf_esp;
  	} else {
  		ss = GSEL(GDATA_SEL, SEL_KPL);
  		esp = (int)&frame->tf_esp;
  	}
  	printf("stack pointer	        = 0x%x:0x%x\n", ss, esp);
  	printf("frame pointer	        = 0x%x:0x%x\n", ss, frame->tf_ebp);
  	printf("code segment		= base 0x%x, limit 0x%x, type 0x%x\n",
  	       softseg.ssd_base, softseg.ssd_limit, softseg.ssd_type);
  	printf("			= DPL %d, pres %d, def32 %d, gran %d\n",
  	       softseg.ssd_dpl, softseg.ssd_p, softseg.ssd_def32,
  	       softseg.ssd_gran);
  	printf("processor eflags	= ");
  	if (frame->tf_eflags & PSL_T)
  		printf("trace trap, ");
  	if (frame->tf_eflags & PSL_I)
  		printf("interrupt enabled, ");
  	if (frame->tf_eflags & PSL_NT)
  		printf("nested task, ");
  	if (frame->tf_eflags & PSL_RF)
  		printf("resume, ");
  	if (frame->tf_eflags & PSL_VM)
  		printf("vm86, ");
  	printf("IOPL = %d\n", (frame->tf_eflags & PSL_IOPL) >> 12);
  	printf("current process		= ");
  	if (curproc) {
  		printf("%lu (%s)\n", (u_long)curproc->p_pid, curthread->td_name);
  	} else {
  		printf("Idle\n");
  	}
  
  #ifdef KDB
  	if (debugger_on_panic || kdb_active) {
  		frame->tf_err = eva;	/* smuggle fault address to ddb */
  		if (kdb_trap(type, 0, frame)) {
  			frame->tf_err = code;	/* restore error code */
  			return;
  		}
  		frame->tf_err = code;		/* restore error code */
  	}
  #endif
  	printf("trap number		= %d\n", type);
  	if (type <= MAX_TRAP_MSG)
  		panic("%s", trap_msg[type]);
  	else
  		panic("unknown/reserved trap");
  }
  
  /*
   * Double fault handler. Called when a fault occurs while writing
   * a frame for a trap/exception onto the stack. This usually occurs
   * when the stack overflows (such is the case with infinite recursion,
   * for example).
   *
   * XXX Note that the current PTD gets replaced by IdlePTD when the
   * task switch occurs. This means that the stack that was active at
   * the time of the double fault is not available at <kstack> unless
   * the machine was idle when the double fault occurred. The downside
   * of this is that "trace <ebp>" in ddb won't work.
   */
  void
  dblfault_handler()
  {
  #ifdef KDTRACE_HOOKS
  	if (dtrace_doubletrap_func != NULL)
  		(*dtrace_doubletrap_func)();
  #endif
  	printf("\nFatal double fault:\n");
  	printf("eip = 0x%x\n", PCPU_GET(common_tss.tss_eip));
  	printf("esp = 0x%x\n", PCPU_GET(common_tss.tss_esp));
  	printf("ebp = 0x%x\n", PCPU_GET(common_tss.tss_ebp));
  #ifdef SMP
  	/* two separate prints in case of a trap on an unmapped page */
  	printf("cpuid = %d; ", PCPU_GET(cpuid));
  	printf("apic id = %02x\n", PCPU_GET(apic_id));
  #endif
  	panic("double fault");
  }
  
  int
  cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
  {
  	struct proc *p;
  	struct trapframe *frame;
  	caddr_t params;
  	int error;
  
  	p = td->td_proc;
  	frame = td->td_frame;
  
  	params = (caddr_t)frame->tf_esp + sizeof(int);
  	sa->code = frame->tf_eax;
  
  	/*
  	 * Need to check if this is a 32 bit or 64 bit syscall.
  	 */
  	if (sa->code == SYS_syscall) {
  		/*
  		 * Code is first argument, followed by actual args.
  		 */
  		sa->code = fuword(params);
  		params += sizeof(int);
  	} else if (sa->code == SYS___syscall) {
  		/*
  		 * Like syscall, but code is a quad, so as to maintain
  		 * quad alignment for the rest of the arguments.
  		 */
  		sa->code = fuword(params);
  		params += sizeof(quad_t);
  	}
  
   	if (p->p_sysent->sv_mask)
   		sa->code &= p->p_sysent->sv_mask;
   	if (sa->code >= p->p_sysent->sv_size)
   		sa->callp = &p->p_sysent->sv_table[0];
    	else
   		sa->callp = &p->p_sysent->sv_table[sa->code];
  	sa->narg = sa->callp->sy_narg;
  
  	if (params != NULL && sa->narg != 0)
  		error = copyin(params, (caddr_t)sa->args,
  		    (u_int)(sa->narg * sizeof(int)));
  	else
  		error = 0;
  
  	if (error == 0) {
  		td->td_retval[0] = 0;
  		td->td_retval[1] = frame->tf_edx;
  	}
  		
  	return (error);
  }
  
  #include "../../kern/subr_syscall.c"
  
  /*
   * syscall - system call request C handler.  A system call is
   * essentially treated as a trap by reusing the frame layout.
   */
  void
  syscall(struct trapframe *frame)
  {
  	struct thread *td;
  	struct syscall_args sa;
  	register_t orig_tf_eflags;
  	int error;
  	ksiginfo_t ksi;
  
  #ifdef DIAGNOSTIC
  	if (ISPL(frame->tf_cs) != SEL_UPL) {
  		panic("syscall");
  		/* NOT REACHED */
  	}
  #endif
  	orig_tf_eflags = frame->tf_eflags;
  
  	td = curthread;
  	td->td_frame = frame;
  
  	error = syscallenter(td, &sa);
  
  	/*
  	 * Traced syscall.
  	 */
  	if ((orig_tf_eflags & PSL_T) && !(orig_tf_eflags & PSL_VM)) {
  		frame->tf_eflags &= ~PSL_T;
  		ksiginfo_init_trap(&ksi);
  		ksi.ksi_signo = SIGTRAP;
  		ksi.ksi_code = TRAP_TRACE;
  		ksi.ksi_addr = (void *)frame->tf_eip;
  		trapsignal(td, &ksi);
  	}
  
  	KASSERT(PCB_USER_FPU(td->td_pcb),
  	    ("System call %s returning with kernel FPU ctx leaked",
  	     syscallname(td->td_proc, sa.code)));
  	KASSERT(td->td_pcb->pcb_save == &td->td_pcb->pcb_user_save,
  	    ("System call %s returning with mangled pcb_save",
  	     syscallname(td->td_proc, sa.code)));
  
  	syscallret(td, error, &sa);
  }
  