xref: /freebsd-11-stable/sys/i386/isa/npx.c

/*-
 * Copyright (c) 1990 William Jolitz.
 * Copyright (c) 1991 The Regents of the University of California.
 * All rights reserved.
 *
 * 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.
 * 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: @(#)npx.c	7.2 (Berkeley) 5/12/91
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD: head/sys/i386/isa/npx.c 238311 2012-07-09 20:55:39Z jhb $");

#include "opt_cpu.h"
#include "opt_isa.h"
#include "opt_npx.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/smp.h>
#include <sys/sysctl.h>
#include <machine/bus.h>
#include <sys/rman.h>
#ifdef NPX_DEBUG
#include <sys/syslog.h>
#endif
#include <sys/signalvar.h>

#include <machine/asmacros.h>
#include <machine/cputypes.h>
#include <machine/frame.h>
#include <machine/md_var.h>
#include <machine/pcb.h>
#include <machine/psl.h>
#include <machine/resource.h>
#include <machine/specialreg.h>
#include <machine/segments.h>
#include <machine/ucontext.h>

#include <machine/intr_machdep.h>
#ifdef XEN
#include <machine/xen/xen-os.h>
#include <xen/hypervisor.h>
#endif

#ifdef DEV_ISA
#include <isa/isavar.h>
#endif

#if !defined(CPU_DISABLE_SSE) && defined(I686_CPU)
#define CPU_ENABLE_SSE
#endif

/*
 * 387 and 287 Numeric Coprocessor Extension (NPX) Driver.
 */

#if defined(__GNUCLIKE_ASM) && !defined(lint)

#define	fldcw(cw)		__asm __volatile("fldcw %0" : : "m" (cw))
#define	fnclex()		__asm __volatile("fnclex")
#define	fninit()		__asm __volatile("fninit")
#define	fnsave(addr)		__asm __volatile("fnsave %0" : "=m" (*(addr)))
#define	fnstcw(addr)		__asm __volatile("fnstcw %0" : "=m" (*(addr)))
#define	fnstsw(addr)		__asm __volatile("fnstsw %0" : "=am" (*(addr)))
#define	fp_divide_by_0()	__asm __volatile( \
				    "fldz; fld1; fdiv %st,%st(1); fnop")
#define	frstor(addr)		__asm __volatile("frstor %0" : : "m" (*(addr)))
#ifdef CPU_ENABLE_SSE
#define	fxrstor(addr)		__asm __volatile("fxrstor %0" : : "m" (*(addr)))
#define	fxsave(addr)		__asm __volatile("fxsave %0" : "=m" (*(addr)))
#endif
#else	/* !(__GNUCLIKE_ASM && !lint) */

void	fldcw(u_short cw);
void	fnclex(void);
void	fninit(void);
void	fnsave(caddr_t addr);
void	fnstcw(caddr_t addr);
void	fnstsw(caddr_t addr);
void	fp_divide_by_0(void);
void	frstor(caddr_t addr);
#ifdef CPU_ENABLE_SSE
void	fxsave(caddr_t addr);
void	fxrstor(caddr_t addr);
#endif

#endif	/* __GNUCLIKE_ASM && !lint */

#ifdef XEN
#define	start_emulating()	(HYPERVISOR_fpu_taskswitch(1))
#define	stop_emulating()	(HYPERVISOR_fpu_taskswitch(0))
#else
#define	start_emulating()	load_cr0(rcr0() | CR0_TS)
#define	stop_emulating()	clts()
#endif

#ifdef CPU_ENABLE_SSE
#define GET_FPU_CW(thread) \
	(cpu_fxsr ? \
		(thread)->td_pcb->pcb_save->sv_xmm.sv_env.en_cw : \
		(thread)->td_pcb->pcb_save->sv_87.sv_env.en_cw)
#define GET_FPU_SW(thread) \
	(cpu_fxsr ? \
		(thread)->td_pcb->pcb_save->sv_xmm.sv_env.en_sw : \
		(thread)->td_pcb->pcb_save->sv_87.sv_env.en_sw)
#define SET_FPU_CW(savefpu, value) do { \
	if (cpu_fxsr) \
		(savefpu)->sv_xmm.sv_env.en_cw = (value); \
	else \
		(savefpu)->sv_87.sv_env.en_cw = (value); \
} while (0)
#else /* CPU_ENABLE_SSE */
#define GET_FPU_CW(thread) \
	(thread->td_pcb->pcb_save->sv_87.sv_env.en_cw)
#define GET_FPU_SW(thread) \
	(thread->td_pcb->pcb_save->sv_87.sv_env.en_sw)
#define SET_FPU_CW(savefpu, value) \
	(savefpu)->sv_87.sv_env.en_cw = (value)
#endif /* CPU_ENABLE_SSE */

typedef u_char bool_t;

#ifdef CPU_ENABLE_SSE
static	void	fpu_clean_state(void);
#endif

static	void	fpusave(union savefpu *);
static	void	fpurstor(union savefpu *);
static	int	npx_attach(device_t dev);
static	void	npx_identify(driver_t *driver, device_t parent);
static	int	npx_probe(device_t dev);

int	hw_float;

SYSCTL_INT(_hw, HW_FLOATINGPT, floatingpoint, CTLFLAG_RD,
    &hw_float, 0, "Floating point instructions executed in hardware");

static	volatile u_int		npx_traps_while_probing;
static	union savefpu		npx_initialstate;

alias_for_inthand_t probetrap;
__asm("								\n\
	.text							\n\
	.p2align 2,0x90						\n\
	.type	" __XSTRING(CNAME(probetrap)) ",@function	\n\
" __XSTRING(CNAME(probetrap)) ":				\n\
	ss							\n\
	incl	" __XSTRING(CNAME(npx_traps_while_probing)) "	\n\
	fnclex							\n\
	iret							\n\
");

/*
 * Identify routine.  Create a connection point on our parent for probing.
 */
static void
npx_identify(driver, parent)
	driver_t *driver;
	device_t parent;
{
	device_t child;

	child = BUS_ADD_CHILD(parent, 0, "npx", 0);
	if (child == NULL)
		panic("npx_identify");
}

/*
 * Probe routine.  Set flags to tell npxattach() what to do.  Set up an
 * interrupt handler if npx needs to use interrupts.
 */
static int
npx_probe(device_t dev)
{
	struct gate_descriptor save_idt_npxtrap;
	u_short control, status;

	device_set_desc(dev, "math processor");

	/*
	 * Modern CPUs all have an FPU that uses the INT16 interface
	 * and provide a simple way to verify that, so handle the
	 * common case right away.
	 */
	if (cpu_feature & CPUID_FPU) {
		hw_float = 1;
		device_quiet(dev);
		return (0);
	}

	save_idt_npxtrap = idt[IDT_MF];
	setidt(IDT_MF, probetrap, SDT_SYS386TGT, SEL_KPL,
	    GSEL(GCODE_SEL, SEL_KPL));

	/*
	 * Don't trap while we're probing.
	 */
	stop_emulating();

	/*
	 * Finish resetting the coprocessor, if any.  If there is an error
	 * pending, then we may get a bogus IRQ13, but npx_intr() will handle
	 * it OK.  Bogus halts have never been observed, but we enabled
	 * IRQ13 and cleared the BUSY# latch early to handle them anyway.
	 */
	fninit();

	/*
	 * Don't use fwait here because it might hang.
	 * Don't use fnop here because it usually hangs if there is no FPU.
	 */
	DELAY(1000);		/* wait for any IRQ13 */
#ifdef DIAGNOSTIC
	if (npx_traps_while_probing != 0)
		printf("fninit caused %u bogus npx trap(s)\n",
		       npx_traps_while_probing);
#endif
	/*
	 * Check for a status of mostly zero.
	 */
	status = 0x5a5a;
	fnstsw(&status);
	if ((status & 0xb8ff) == 0) {
		/*
		 * Good, now check for a proper control word.
		 */
		control = 0x5a5a;
		fnstcw(&control);
		if ((control & 0x1f3f) == 0x033f) {
			/*
			 * We have an npx, now divide by 0 to see if exception
			 * 16 works.
			 */
			control &= ~(1 << 2);	/* enable divide by 0 trap */
			fldcw(control);
#ifdef FPU_ERROR_BROKEN
			/*
			 * FPU error signal doesn't work on some CPU
			 * accelerator board.
			 */
			hw_float = 1;
			return (0);
#endif
			npx_traps_while_probing = 0;
			fp_divide_by_0();
			if (npx_traps_while_probing != 0) {
				/*
				 * Good, exception 16 works.
				 */
				hw_float = 1;
				goto cleanup;
			}
			device_printf(dev,
	"FPU does not use exception 16 for error reporting\n");
			goto cleanup;
		}
	}

	/*
	 * Probe failed.  Floating point simply won't work.
	 * Notify user and disable FPU/MMX/SSE instruction execution.
	 */
	device_printf(dev, "WARNING: no FPU!\n");
	__asm __volatile("smsw %%ax; orb %0,%%al; lmsw %%ax" : :
	    "n" (CR0_EM | CR0_MP) : "ax");

cleanup:
	idt[IDT_MF] = save_idt_npxtrap;
	return (hw_float ? 0 : ENXIO);
}

/*
 * Attach routine - announce which it is, and wire into system
 */
static int
npx_attach(device_t dev)
{

	npxinit();
	critical_enter();
	stop_emulating();
	fpusave(&npx_initialstate);
	start_emulating();
#ifdef CPU_ENABLE_SSE
	if (cpu_fxsr) {
		if (npx_initialstate.sv_xmm.sv_env.en_mxcsr_mask)
			cpu_mxcsr_mask =
			    npx_initialstate.sv_xmm.sv_env.en_mxcsr_mask;
		else
			cpu_mxcsr_mask = 0xFFBF;
		bzero(npx_initialstate.sv_xmm.sv_fp,
		    sizeof(npx_initialstate.sv_xmm.sv_fp));
		bzero(npx_initialstate.sv_xmm.sv_xmm,
		    sizeof(npx_initialstate.sv_xmm.sv_xmm));
		/* XXX might need even more zeroing. */
	} else
#endif
		bzero(npx_initialstate.sv_87.sv_ac,
		    sizeof(npx_initialstate.sv_87.sv_ac));
	critical_exit();

	return (0);
}

/*
 * Initialize floating point unit.
 */
void
npxinit(void)
{
	static union savefpu dummy;
	register_t saveintr;
	u_short control;

	if (!hw_float)
		return;
	/*
	 * fninit has the same h/w bugs as fnsave.  Use the detoxified
	 * fnsave to throw away any junk in the fpu.  npxsave() initializes
	 * the fpu and sets fpcurthread = NULL as important side effects.
	 *
	 * It is too early for critical_enter() to work on AP.
	 */
	saveintr = intr_disable();
	npxsave(&dummy);
	stop_emulating();
#ifdef CPU_ENABLE_SSE
	/* XXX npxsave() doesn't actually initialize the fpu in the SSE case. */
	if (cpu_fxsr)
		fninit();
#endif
	control = __INITIAL_NPXCW__;
	fldcw(control);
	start_emulating();
	intr_restore(saveintr);
}

/*
 * Free coprocessor (if we have it).
 */
void
npxexit(td)
	struct thread *td;
{

	critical_enter();
	if (curthread == PCPU_GET(fpcurthread))
		npxsave(PCPU_GET(curpcb)->pcb_save);
	critical_exit();
#ifdef NPX_DEBUG
	if (hw_float) {
		u_int	masked_exceptions;

		masked_exceptions = GET_FPU_CW(td) & GET_FPU_SW(td) & 0x7f;
		/*
		 * Log exceptions that would have trapped with the old
		 * control word (overflow, divide by 0, and invalid operand).
		 */
		if (masked_exceptions & 0x0d)
			log(LOG_ERR,
	"pid %d (%s) exited with masked floating point exceptions 0x%02x\n",
			    td->td_proc->p_pid, td->td_proc->p_comm,
			    masked_exceptions);
	}
#endif
}

int
npxformat()
{

	if (!hw_float)
		return (_MC_FPFMT_NODEV);
#ifdef	CPU_ENABLE_SSE
	if (cpu_fxsr)
		return (_MC_FPFMT_XMM);
#endif
	return (_MC_FPFMT_387);
}

/*
 * The following mechanism is used to ensure that the FPE_... value
 * that is passed as a trapcode to the signal handler of the user
 * process does not have more than one bit set.
 *
 * Multiple bits may be set if the user process modifies the control
 * word while a status word bit is already set.  While this is a sign
 * of bad coding, we have no choise than to narrow them down to one
 * bit, since we must not send a trapcode that is not exactly one of
 * the FPE_ macros.
 *
 * The mechanism has a static table with 127 entries.  Each combination
 * of the 7 FPU status word exception bits directly translates to a
 * position in this table, where a single FPE_... value is stored.
 * This FPE_... value stored there is considered the "most important"
 * of the exception bits and will be sent as the signal code.  The
 * precedence of the bits is based upon Intel Document "Numerical
 * Applications", Chapter "Special Computational Situations".
 *
 * The macro to choose one of these values does these steps: 1) Throw
 * away status word bits that cannot be masked.  2) Throw away the bits
 * currently masked in the control word, assuming the user isn't
 * interested in them anymore.  3) Reinsert status word bit 7 (stack
 * fault) if it is set, which cannot be masked but must be presered.
 * 4) Use the remaining bits to point into the trapcode table.
 *
 * The 6 maskable bits in order of their preference, as stated in the
 * above referenced Intel manual:
 * 1  Invalid operation (FP_X_INV)
 * 1a   Stack underflow
 * 1b   Stack overflow
 * 1c   Operand of unsupported format
 * 1d   SNaN operand.
 * 2  QNaN operand (not an exception, irrelavant here)
 * 3  Any other invalid-operation not mentioned above or zero divide
 *      (FP_X_INV, FP_X_DZ)
 * 4  Denormal operand (FP_X_DNML)
 * 5  Numeric over/underflow (FP_X_OFL, FP_X_UFL)
 * 6  Inexact result (FP_X_IMP)
 */
static char fpetable[128] = {
	0,
	FPE_FLTINV,	/*  1 - INV */
	FPE_FLTUND,	/*  2 - DNML */
	FPE_FLTINV,	/*  3 - INV | DNML */
	FPE_FLTDIV,	/*  4 - DZ */
	FPE_FLTINV,	/*  5 - INV | DZ */
	FPE_FLTDIV,	/*  6 - DNML | DZ */
	FPE_FLTINV,	/*  7 - INV | DNML | DZ */
	FPE_FLTOVF,	/*  8 - OFL */
	FPE_FLTINV,	/*  9 - INV | OFL */
	FPE_FLTUND,	/*  A - DNML | OFL */
	FPE_FLTINV,	/*  B - INV | DNML | OFL */
	FPE_FLTDIV,	/*  C - DZ | OFL */
	FPE_FLTINV,	/*  D - INV | DZ | OFL */
	FPE_FLTDIV,	/*  E - DNML | DZ | OFL */
	FPE_FLTINV,	/*  F - INV | DNML | DZ | OFL */
	FPE_FLTUND,	/* 10 - UFL */
	FPE_FLTINV,	/* 11 - INV | UFL */
	FPE_FLTUND,	/* 12 - DNML | UFL */
	FPE_FLTINV,	/* 13 - INV | DNML | UFL */
	FPE_FLTDIV,	/* 14 - DZ | UFL */
	FPE_FLTINV,	/* 15 - INV | DZ | UFL */
	FPE_FLTDIV,	/* 16 - DNML | DZ | UFL */
	FPE_FLTINV,	/* 17 - INV | DNML | DZ | UFL */
	FPE_FLTOVF,	/* 18 - OFL | UFL */
	FPE_FLTINV,	/* 19 - INV | OFL | UFL */
	FPE_FLTUND,	/* 1A - DNML | OFL | UFL */
	FPE_FLTINV,	/* 1B - INV | DNML | OFL | UFL */
	FPE_FLTDIV,	/* 1C - DZ | OFL | UFL */
	FPE_FLTINV,	/* 1D - INV | DZ | OFL | UFL */
	FPE_FLTDIV,	/* 1E - DNML | DZ | OFL | UFL */
	FPE_FLTINV,	/* 1F - INV | DNML | DZ | OFL | UFL */
	FPE_FLTRES,	/* 20 - IMP */
	FPE_FLTINV,	/* 21 - INV | IMP */
	FPE_FLTUND,	/* 22 - DNML | IMP */
	FPE_FLTINV,	/* 23 - INV | DNML | IMP */
	FPE_FLTDIV,	/* 24 - DZ | IMP */
	FPE_FLTINV,	/* 25 - INV | DZ | IMP */
	FPE_FLTDIV,	/* 26 - DNML | DZ | IMP */
	FPE_FLTINV,	/* 27 - INV | DNML | DZ | IMP */
	FPE_FLTOVF,	/* 28 - OFL | IMP */
	FPE_FLTINV,	/* 29 - INV | OFL | IMP */
	FPE_FLTUND,	/* 2A - DNML | OFL | IMP */
	FPE_FLTINV,	/* 2B - INV | DNML | OFL | IMP */
	FPE_FLTDIV,	/* 2C - DZ | OFL | IMP */
	FPE_FLTINV,	/* 2D - INV | DZ | OFL | IMP */
	FPE_FLTDIV,	/* 2E - DNML | DZ | OFL | IMP */
	FPE_FLTINV,	/* 2F - INV | DNML | DZ | OFL | IMP */
	FPE_FLTUND,	/* 30 - UFL | IMP */
	FPE_FLTINV,	/* 31 - INV | UFL | IMP */
	FPE_FLTUND,	/* 32 - DNML | UFL | IMP */
	FPE_FLTINV,	/* 33 - INV | DNML | UFL | IMP */
	FPE_FLTDIV,	/* 34 - DZ | UFL | IMP */
	FPE_FLTINV,	/* 35 - INV | DZ | UFL | IMP */
	FPE_FLTDIV,	/* 36 - DNML | DZ | UFL | IMP */
	FPE_FLTINV,	/* 37 - INV | DNML | DZ | UFL | IMP */
	FPE_FLTOVF,	/* 38 - OFL | UFL | IMP */
	FPE_FLTINV,	/* 39 - INV | OFL | UFL | IMP */
	FPE_FLTUND,	/* 3A - DNML | OFL | UFL | IMP */
	FPE_FLTINV,	/* 3B - INV | DNML | OFL | UFL | IMP */
	FPE_FLTDIV,	/* 3C - DZ | OFL | UFL | IMP */
	FPE_FLTINV,	/* 3D - INV | DZ | OFL | UFL | IMP */
	FPE_FLTDIV,	/* 3E - DNML | DZ | OFL | UFL | IMP */
	FPE_FLTINV,	/* 3F - INV | DNML | DZ | OFL | UFL | IMP */
	FPE_FLTSUB,	/* 40 - STK */
	FPE_FLTSUB,	/* 41 - INV | STK */
	FPE_FLTUND,	/* 42 - DNML | STK */
	FPE_FLTSUB,	/* 43 - INV | DNML | STK */
	FPE_FLTDIV,	/* 44 - DZ | STK */
	FPE_FLTSUB,	/* 45 - INV | DZ | STK */
	FPE_FLTDIV,	/* 46 - DNML | DZ | STK */
	FPE_FLTSUB,	/* 47 - INV | DNML | DZ | STK */
	FPE_FLTOVF,	/* 48 - OFL | STK */
	FPE_FLTSUB,	/* 49 - INV | OFL | STK */
	FPE_FLTUND,	/* 4A - DNML | OFL | STK */
	FPE_FLTSUB,	/* 4B - INV | DNML | OFL | STK */
	FPE_FLTDIV,	/* 4C - DZ | OFL | STK */
	FPE_FLTSUB,	/* 4D - INV | DZ | OFL | STK */
	FPE_FLTDIV,	/* 4E - DNML | DZ | OFL | STK */
	FPE_FLTSUB,	/* 4F - INV | DNML | DZ | OFL | STK */
	FPE_FLTUND,	/* 50 - UFL | STK */
	FPE_FLTSUB,	/* 51 - INV | UFL | STK */
	FPE_FLTUND,	/* 52 - DNML | UFL | STK */
	FPE_FLTSUB,	/* 53 - INV | DNML | UFL | STK */
	FPE_FLTDIV,	/* 54 - DZ | UFL | STK */
	FPE_FLTSUB,	/* 55 - INV | DZ | UFL | STK */
	FPE_FLTDIV,	/* 56 - DNML | DZ | UFL | STK */
	FPE_FLTSUB,	/* 57 - INV | DNML | DZ | UFL | STK */
	FPE_FLTOVF,	/* 58 - OFL | UFL | STK */
	FPE_FLTSUB,	/* 59 - INV | OFL | UFL | STK */
	FPE_FLTUND,	/* 5A - DNML | OFL | UFL | STK */
	FPE_FLTSUB,	/* 5B - INV | DNML | OFL | UFL | STK */
	FPE_FLTDIV,	/* 5C - DZ | OFL | UFL | STK */
	FPE_FLTSUB,	/* 5D - INV | DZ | OFL | UFL | STK */
	FPE_FLTDIV,	/* 5E - DNML | DZ | OFL | UFL | STK */
	FPE_FLTSUB,	/* 5F - INV | DNML | DZ | OFL | UFL | STK */
	FPE_FLTRES,	/* 60 - IMP | STK */
	FPE_FLTSUB,	/* 61 - INV | IMP | STK */
	FPE_FLTUND,	/* 62 - DNML | IMP | STK */
	FPE_FLTSUB,	/* 63 - INV | DNML | IMP | STK */
	FPE_FLTDIV,	/* 64 - DZ | IMP | STK */
	FPE_FLTSUB,	/* 65 - INV | DZ | IMP | STK */
	FPE_FLTDIV,	/* 66 - DNML | DZ | IMP | STK */
	FPE_FLTSUB,	/* 67 - INV | DNML | DZ | IMP | STK */
	FPE_FLTOVF,	/* 68 - OFL | IMP | STK */
	FPE_FLTSUB,	/* 69 - INV | OFL | IMP | STK */
	FPE_FLTUND,	/* 6A - DNML | OFL | IMP | STK */
	FPE_FLTSUB,	/* 6B - INV | DNML | OFL | IMP | STK */
	FPE_FLTDIV,	/* 6C - DZ | OFL | IMP | STK */
	FPE_FLTSUB,	/* 6D - INV | DZ | OFL | IMP | STK */
	FPE_FLTDIV,	/* 6E - DNML | DZ | OFL | IMP | STK */
	FPE_FLTSUB,	/* 6F - INV | DNML | DZ | OFL | IMP | STK */
	FPE_FLTUND,	/* 70 - UFL | IMP | STK */
	FPE_FLTSUB,	/* 71 - INV | UFL | IMP | STK */
	FPE_FLTUND,	/* 72 - DNML | UFL | IMP | STK */
	FPE_FLTSUB,	/* 73 - INV | DNML | UFL | IMP | STK */
	FPE_FLTDIV,	/* 74 - DZ | UFL | IMP | STK */
	FPE_FLTSUB,	/* 75 - INV | DZ | UFL | IMP | STK */
	FPE_FLTDIV,	/* 76 - DNML | DZ | UFL | IMP | STK */
	FPE_FLTSUB,	/* 77 - INV | DNML | DZ | UFL | IMP | STK */
	FPE_FLTOVF,	/* 78 - OFL | UFL | IMP | STK */
	FPE_FLTSUB,	/* 79 - INV | OFL | UFL | IMP | STK */
	FPE_FLTUND,	/* 7A - DNML | OFL | UFL | IMP | STK */
	FPE_FLTSUB,	/* 7B - INV | DNML | OFL | UFL | IMP | STK */
	FPE_FLTDIV,	/* 7C - DZ | OFL | UFL | IMP | STK */
	FPE_FLTSUB,	/* 7D - INV | DZ | OFL | UFL | IMP | STK */
	FPE_FLTDIV,	/* 7E - DNML | DZ | OFL | UFL | IMP | STK */
	FPE_FLTSUB,	/* 7F - INV | DNML | DZ | OFL | UFL | IMP | STK */
};

/*
 * Preserve the FP status word, clear FP exceptions, then generate a SIGFPE.
 *
 * Clearing exceptions is necessary mainly to avoid IRQ13 bugs.  We now
 * depend on longjmp() restoring a usable state.  Restoring the state
 * or examining it might fail if we didn't clear exceptions.
 *
 * The error code chosen will be one of the FPE_... macros. It will be
 * sent as the second argument to old BSD-style signal handlers and as
 * "siginfo_t->si_code" (second argument) to SA_SIGINFO signal handlers.
 *
 * XXX the FP state is not preserved across signal handlers.  So signal
 * handlers cannot afford to do FP unless they preserve the state or
 * longjmp() out.  Both preserving the state and longjmp()ing may be
 * destroyed by IRQ13 bugs.  Clearing FP exceptions is not an acceptable
 * solution for signals other than SIGFPE.
 */
int
npxtrap()
{
	u_short control, status;

	if (!hw_float) {
		printf("npxtrap: fpcurthread = %p, curthread = %p, hw_float = %d\n",
		       PCPU_GET(fpcurthread), curthread, hw_float);
		panic("npxtrap from nowhere");
	}
	critical_enter();

	/*
	 * Interrupt handling (for another interrupt) may have pushed the
	 * state to memory.  Fetch the relevant parts of the state from
	 * wherever they are.
	 */
	if (PCPU_GET(fpcurthread) != curthread) {
		control = GET_FPU_CW(curthread);
		status = GET_FPU_SW(curthread);
	} else {
		fnstcw(&control);
		fnstsw(&status);
	}

	if (PCPU_GET(fpcurthread) == curthread)
		fnclex();
	critical_exit();
	return (fpetable[status & ((~control & 0x3f) | 0x40)]);
}

/*
 * Implement device not available (DNA) exception
 *
 * It would be better to switch FP context here (if curthread != fpcurthread)
 * and not necessarily for every context switch, but it is too hard to
 * access foreign pcb's.
 */

static int err_count = 0;

int
npxdna(void)
{
	struct pcb *pcb;

	if (!hw_float)
		return (0);
	critical_enter();
	if (PCPU_GET(fpcurthread) == curthread) {
		printf("npxdna: fpcurthread == curthread %d times\n",
		    ++err_count);
		stop_emulating();
		critical_exit();
		return (1);
	}
	if (PCPU_GET(fpcurthread) != NULL) {
		printf("npxdna: fpcurthread = %p (%d), curthread = %p (%d)\n",
		       PCPU_GET(fpcurthread),
		       PCPU_GET(fpcurthread)->td_proc->p_pid,
		       curthread, curthread->td_proc->p_pid);
		panic("npxdna");
	}
	stop_emulating();
	/*
	 * Record new context early in case frstor causes an IRQ13.
	 */
	PCPU_SET(fpcurthread, curthread);
	pcb = PCPU_GET(curpcb);

#ifdef CPU_ENABLE_SSE
	if (cpu_fxsr)
		fpu_clean_state();
#endif

	if ((pcb->pcb_flags & PCB_NPXINITDONE) == 0) {
		/*
		 * This is the first time this thread has used the FPU or
		 * the PCB doesn't contain a clean FPU state.  Explicitly
		 * load an initial state.
		 */
		fpurstor(&npx_initialstate);
		if (pcb->pcb_initial_npxcw != __INITIAL_NPXCW__)
			fldcw(pcb->pcb_initial_npxcw);
		pcb->pcb_flags |= PCB_NPXINITDONE;
		if (PCB_USER_FPU(pcb))
			pcb->pcb_flags |= PCB_NPXUSERINITDONE;
	} else {
		/*
		 * The following fpurstor() may cause an IRQ13 when the
		 * state being restored has a pending error.  The error will
		 * appear to have been triggered by the current (npx) user
		 * instruction even when that instruction is a no-wait
		 * instruction that should not trigger an error (e.g.,
		 * fnclex).  On at least one 486 system all of the no-wait
		 * instructions are broken the same as frstor, so our
		 * treatment does not amplify the breakage.  On at least
		 * one 386/Cyrix 387 system, fnclex works correctly while
		 * frstor and fnsave are broken, so our treatment breaks
		 * fnclex if it is the first FPU instruction after a context
		 * switch.
		 */
		fpurstor(pcb->pcb_save);
	}
	critical_exit();

	return (1);
}

/*
 * Wrapper for fnsave instruction, partly to handle hardware bugs.  When npx
 * exceptions are reported via IRQ13, spurious IRQ13's may be triggered by
 * no-wait npx instructions.  See the Intel application note AP-578 for
 * details.  This doesn't cause any additional complications here.  IRQ13's
 * are inherently asynchronous unless the CPU is frozen to deliver them --
 * one that started in userland may be delivered many instructions later,
 * after the process has entered the kernel.  It may even be delivered after
 * the fnsave here completes.  A spurious IRQ13 for the fnsave is handled in
 * the same way as a very-late-arriving non-spurious IRQ13 from user mode:
 * it is normally ignored at first because we set fpcurthread to NULL; it is
 * normally retriggered in npxdna() after return to user mode.
 *
 * npxsave() must be called with interrupts disabled, so that it clears
 * fpcurthread atomically with saving the state.  We require callers to do the
 * disabling, since most callers need to disable interrupts anyway to call
 * npxsave() atomically with checking fpcurthread.
 *
 * A previous version of npxsave() went to great lengths to excecute fnsave
 * with interrupts enabled in case executing it froze the CPU.  This case
 * can't happen, at least for Intel CPU/NPX's.  Spurious IRQ13's don't imply
 * spurious freezes.
 */
void
npxsave(addr)
	union savefpu *addr;
{

	stop_emulating();
	fpusave(addr);

	start_emulating();
	PCPU_SET(fpcurthread, NULL);
}

void
npxdrop()
{
	struct thread *td;

	/*
	 * Discard pending exceptions in the !cpu_fxsr case so that unmasked
	 * ones don't cause a panic on the next frstor.
	 */
#ifdef CPU_ENABLE_SSE
	if (!cpu_fxsr)
#endif
		fnclex();

	td = PCPU_GET(fpcurthread);
	KASSERT(td == curthread, ("fpudrop: fpcurthread != curthread"));
	CRITICAL_ASSERT(td);
	PCPU_SET(fpcurthread, NULL);
	td->td_pcb->pcb_flags &= ~PCB_NPXINITDONE;
	start_emulating();
}

/*
 * Get the user state of the FPU into pcb->pcb_user_save without
 * dropping ownership (if possible).  It returns the FPU ownership
 * status.
 */
int
npxgetregs(struct thread *td)
{
	struct pcb *pcb;

	if (!hw_float)
		return (_MC_FPOWNED_NONE);

	pcb = td->td_pcb;
	if ((pcb->pcb_flags & PCB_NPXINITDONE) == 0) {
		bcopy(&npx_initialstate, &pcb->pcb_user_save,
		    sizeof(npx_initialstate));
		SET_FPU_CW(&pcb->pcb_user_save, pcb->pcb_initial_npxcw);
		npxuserinited(td);
		return (_MC_FPOWNED_PCB);
	}
	critical_enter();
	if (td == PCPU_GET(fpcurthread)) {
		fpusave(&pcb->pcb_user_save);
#ifdef CPU_ENABLE_SSE
		if (!cpu_fxsr)
#endif
			/*
			 * fnsave initializes the FPU and destroys whatever
			 * context it contains.  Make sure the FPU owner
			 * starts with a clean state next time.
			 */
			npxdrop();
		critical_exit();
		return (_MC_FPOWNED_FPU);
	} else {
		critical_exit();
		return (_MC_FPOWNED_PCB);
	}
}

void
npxuserinited(struct thread *td)
{
	struct pcb *pcb;

	pcb = td->td_pcb;
	if (PCB_USER_FPU(pcb))
		pcb->pcb_flags |= PCB_NPXINITDONE;
	pcb->pcb_flags |= PCB_NPXUSERINITDONE;
}


void
npxsetregs(struct thread *td, union savefpu *addr)
{
	struct pcb *pcb;

	if (!hw_float)
		return;

	pcb = td->td_pcb;
	critical_enter();
	if (td == PCPU_GET(fpcurthread) && PCB_USER_FPU(pcb)) {
#ifdef CPU_ENABLE_SSE
		if (!cpu_fxsr)
#endif
			fnclex();	/* As in npxdrop(). */
		if (((uintptr_t)addr & 0xf) != 0) {
			bcopy(addr, &pcb->pcb_user_save, sizeof(*addr));
			fpurstor(&pcb->pcb_user_save);
		} else
			fpurstor(addr);
		critical_exit();
		pcb->pcb_flags |= PCB_NPXUSERINITDONE | PCB_NPXINITDONE;
	} else {
		critical_exit();
		bcopy(addr, &pcb->pcb_user_save, sizeof(*addr));
		npxuserinited(td);
	}
}

static void
fpusave(addr)
	union savefpu *addr;
{

#ifdef CPU_ENABLE_SSE
	if (cpu_fxsr)
		fxsave(addr);
	else
#endif
		fnsave(addr);
}

#ifdef CPU_ENABLE_SSE
/*
 * On AuthenticAMD processors, the fxrstor instruction does not restore
 * the x87's stored last instruction pointer, last data pointer, and last
 * opcode values, except in the rare case in which the exception summary
 * (ES) bit in the x87 status word is set to 1.
 *
 * In order to avoid leaking this information across processes, we clean
 * these values by performing a dummy load before executing fxrstor().
 */
static void
fpu_clean_state(void)
{
	static float dummy_variable = 0.0;
	u_short status;

	/*
	 * Clear the ES bit in the x87 status word if it is currently
	 * set, in order to avoid causing a fault in the upcoming load.
	 */
	fnstsw(&status);
	if (status & 0x80)
		fnclex();

	/*
	 * Load the dummy variable into the x87 stack.  This mangles
	 * the x87 stack, but we don't care since we're about to call
	 * fxrstor() anyway.
	 */
	__asm __volatile("ffree %%st(7); flds %0" : : "m" (dummy_variable));
}
#endif /* CPU_ENABLE_SSE */

static void
fpurstor(addr)
	union savefpu *addr;
{

#ifdef CPU_ENABLE_SSE
	if (cpu_fxsr)
		fxrstor(addr);
	else
#endif
		frstor(addr);
}

static device_method_t npx_methods[] = {
	/* Device interface */
	DEVMETHOD(device_identify,	npx_identify),
	DEVMETHOD(device_probe,		npx_probe),
	DEVMETHOD(device_attach,	npx_attach),
	DEVMETHOD(device_detach,	bus_generic_detach),
	DEVMETHOD(device_shutdown,	bus_generic_shutdown),
	DEVMETHOD(device_suspend,	bus_generic_suspend),
	DEVMETHOD(device_resume,	bus_generic_resume),

	{ 0, 0 }
};

static driver_t npx_driver = {
	"npx",
	npx_methods,
	1,			/* no softc */
};

static devclass_t npx_devclass;

/*
 * We prefer to attach to the root nexus so that the usual case (exception 16)
 * doesn't describe the processor as being `on isa'.
 */
DRIVER_MODULE(npx, nexus, npx_driver, npx_devclass, 0, 0);

#ifdef DEV_ISA
/*
 * This sucks up the legacy ISA support assignments from PNPBIOS/ACPI.
 */
static struct isa_pnp_id npxisa_ids[] = {
	{ 0x040cd041, "Legacy ISA coprocessor support" }, /* PNP0C04 */
	{ 0 }
};

static int
npxisa_probe(device_t dev)
{
	int result;
	if ((result = ISA_PNP_PROBE(device_get_parent(dev), dev, npxisa_ids)) <= 0) {
		device_quiet(dev);
	}
	return(result);
}

static int
npxisa_attach(device_t dev)
{
	return (0);
}

static device_method_t npxisa_methods[] = {
	/* Device interface */
	DEVMETHOD(device_probe,		npxisa_probe),
	DEVMETHOD(device_attach,	npxisa_attach),
	DEVMETHOD(device_detach,	bus_generic_detach),
	DEVMETHOD(device_shutdown,	bus_generic_shutdown),
	DEVMETHOD(device_suspend,	bus_generic_suspend),
	DEVMETHOD(device_resume,	bus_generic_resume),

	{ 0, 0 }
};

static driver_t npxisa_driver = {
	"npxisa",
	npxisa_methods,
	1,			/* no softc */
};

static devclass_t npxisa_devclass;

DRIVER_MODULE(npxisa, isa, npxisa_driver, npxisa_devclass, 0, 0);
#ifndef PC98
DRIVER_MODULE(npxisa, acpi, npxisa_driver, npxisa_devclass, 0, 0);
#endif
#endif /* DEV_ISA */

static MALLOC_DEFINE(M_FPUKERN_CTX, "fpukern_ctx",
    "Kernel contexts for FPU state");

#define	XSAVE_AREA_ALIGN	64

#define	FPU_KERN_CTX_NPXINITDONE 0x01

struct fpu_kern_ctx {
	union savefpu *prev;
	uint32_t flags;
	char hwstate1[];
};

struct fpu_kern_ctx *
fpu_kern_alloc_ctx(u_int flags)
{
	struct fpu_kern_ctx *res;
	size_t sz;

	sz = sizeof(struct fpu_kern_ctx) + XSAVE_AREA_ALIGN +
	    sizeof(union savefpu);
	res = malloc(sz, M_FPUKERN_CTX, ((flags & FPU_KERN_NOWAIT) ?
	    M_NOWAIT : M_WAITOK) | M_ZERO);
	return (res);
}

void
fpu_kern_free_ctx(struct fpu_kern_ctx *ctx)
{

	/* XXXKIB clear the memory ? */
	free(ctx, M_FPUKERN_CTX);
}

static union savefpu *
fpu_kern_ctx_savefpu(struct fpu_kern_ctx *ctx)
{
	vm_offset_t p;

	p = (vm_offset_t)&ctx->hwstate1;
	p = roundup2(p, XSAVE_AREA_ALIGN);
	return ((union savefpu *)p);
}

int
fpu_kern_enter(struct thread *td, struct fpu_kern_ctx *ctx, u_int flags)
{
	struct pcb *pcb;

	pcb = td->td_pcb;
	KASSERT(!PCB_USER_FPU(pcb) || pcb->pcb_save == &pcb->pcb_user_save,
	    ("mangled pcb_save"));
	ctx->flags = 0;
	if ((pcb->pcb_flags & PCB_NPXINITDONE) != 0)
		ctx->flags |= FPU_KERN_CTX_NPXINITDONE;
	npxexit(td);
	ctx->prev = pcb->pcb_save;
	pcb->pcb_save = fpu_kern_ctx_savefpu(ctx);
	pcb->pcb_flags |= PCB_KERNNPX;
	pcb->pcb_flags &= ~PCB_NPXINITDONE;
	return (0);
}

int
fpu_kern_leave(struct thread *td, struct fpu_kern_ctx *ctx)
{
	struct pcb *pcb;

	pcb = td->td_pcb;
	critical_enter();
	if (curthread == PCPU_GET(fpcurthread))
		npxdrop();
	critical_exit();
	pcb->pcb_save = ctx->prev;
	if (pcb->pcb_save == &pcb->pcb_user_save) {
		if ((pcb->pcb_flags & PCB_NPXUSERINITDONE) != 0)
			pcb->pcb_flags |= PCB_NPXINITDONE;
		else
			pcb->pcb_flags &= ~PCB_NPXINITDONE;
		pcb->pcb_flags &= ~PCB_KERNNPX;
	} else {
		if ((ctx->flags & FPU_KERN_CTX_NPXINITDONE) != 0)
			pcb->pcb_flags |= PCB_NPXINITDONE;
		else
			pcb->pcb_flags &= ~PCB_NPXINITDONE;
		KASSERT(!PCB_USER_FPU(pcb), ("unpaired fpu_kern_leave"));
	}
	return (0);
}

int
fpu_kern_thread(u_int flags)
{
	struct pcb *pcb;

	pcb = PCPU_GET(curpcb);
	KASSERT((curthread->td_pflags & TDP_KTHREAD) != 0,
	    ("Only kthread may use fpu_kern_thread"));
	KASSERT(pcb->pcb_save == &pcb->pcb_user_save, ("mangled pcb_save"));
	KASSERT(PCB_USER_FPU(pcb), ("recursive call"));

	pcb->pcb_flags |= PCB_KERNNPX;
	return (0);
}

int
is_fpu_kern_thread(u_int flags)
{

	if ((curthread->td_pflags & TDP_KTHREAD) == 0)
		return (0);
	return ((PCPU_GET(curpcb)->pcb_flags & PCB_KERNNPX) != 0);
}