FreeBSD/Linux Kernel Cross Reference
sys/i386/i386/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.
     * 3. 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("$FreeBSD$");
    
    #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 <vm/uma.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 <x86/ifunc.h>
    
    #include <machine/intr_machdep.h>
    
    #ifdef DEV_ISA
    #include <isa/isavar.h>
    #endif
    
    /*
     * 387 and 287 Numeric Coprocessor Extension (NPX) Driver.
     */
    
    #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)))
    #define fxrstor(addr)           __asm __volatile("fxrstor %0" : : "m" (*(addr)))
    #define fxsave(addr)            __asm __volatile("fxsave %0" : "=m" (*(addr)))
    #define ldmxcsr(csr)            __asm __volatile("ldmxcsr %0" : : "m" (csr))
    #define stmxcsr(addr)           __asm __volatile("stmxcsr %0" : : "m" (*(addr)))
    
    static __inline void
    xrstor(char *addr, uint64_t mask)
    {
            uint32_t low, hi;
   
           low = mask;
           hi = mask >> 32;
           __asm __volatile("xrstor %0" : : "m" (*addr), "a" (low), "d" (hi));
   }
   
   static __inline void
   xsave(char *addr, uint64_t mask)
   {
           uint32_t low, hi;
   
           low = mask;
           hi = mask >> 32;
           __asm __volatile("xsave %0" : "=m" (*addr) : "a" (low), "d" (hi) :
               "memory");
   }
   
   static __inline void
   xsaveopt(char *addr, uint64_t mask)
   {
           uint32_t low, hi;
   
           low = mask;
           hi = mask >> 32;
           __asm __volatile("xsaveopt %0" : "=m" (*addr) : "a" (low), "d" (hi) :
               "memory");
   }
   
   #define start_emulating()       load_cr0(rcr0() | CR0_TS)
   #define stop_emulating()        clts()
   
   #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)
   
   CTASSERT(sizeof(union savefpu) == 512);
   CTASSERT(sizeof(struct xstate_hdr) == 64);
   CTASSERT(sizeof(struct savefpu_ymm) == 832);
   
   /*
    * This requirement is to make it easier for asm code to calculate
    * offset of the fpu save area from the pcb address. FPU save area
    * must be 64-byte aligned.
    */
   CTASSERT(sizeof(struct pcb) % XSAVE_AREA_ALIGN == 0);
   
   /*
    * Ensure the copy of XCR0 saved in a core is contained in the padding
    * area.
    */
   CTASSERT(X86_XSTATE_XCR0_OFFSET >= offsetof(struct savexmm, sv_pad) &&
       X86_XSTATE_XCR0_OFFSET + sizeof(uint64_t) <= sizeof(struct savexmm));
   
   static  void    fpu_clean_state(void);
   
   static  void    fpurstor(union savefpu *);
   
   int     hw_float;
   
   SYSCTL_INT(_hw, HW_FLOATINGPT, floatingpoint, CTLFLAG_RD,
       &hw_float, 0, "Floating point instructions executed in hardware");
   
   int lazy_fpu_switch = 0;
   SYSCTL_INT(_hw, OID_AUTO, lazy_fpu_switch, CTLFLAG_RWTUN | CTLFLAG_NOFETCH,
       &lazy_fpu_switch, 0,
       "Lazily load FPU context after context switch");
   
   int use_xsave;
   uint64_t xsave_mask;
   static  uma_zone_t fpu_save_area_zone;
   static  union savefpu *npx_initialstate;
   
   static struct xsave_area_elm_descr {
           u_int   offset;
           u_int   size;
   } *xsave_area_desc;
   
   static  volatile u_int          npx_traps_while_probing;
   
   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\
   ");
   
   /*
    * Determine if an FPU is present and how to use it.
    */
   static int
   npx_probe(void)
   {
           struct gate_descriptor save_idt_npxtrap;
           u_short control, status;
   
           /*
            * 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;
                   return (1);
           }
   
           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);
                           npx_traps_while_probing = 0;
                           fp_divide_by_0();
                           if (npx_traps_while_probing != 0) {
                                   /*
                                    * Good, exception 16 works.
                                    */
                                   hw_float = 1;
                                   goto cleanup;
                           }
                           printf(
           "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.
            */
           printf("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);
   }
   
   static void
   fpusave_xsaveopt(union savefpu *addr)
   {
   
           xsaveopt((char *)addr, xsave_mask);
   }
   
   static void
   fpusave_xsave(union savefpu *addr)
   {
   
           xsave((char *)addr, xsave_mask);
   }
   
   static void
   fpusave_fxsave(union savefpu *addr)
   {
   
           fxsave((char *)addr);
   }
   
   static void
   fpusave_fnsave(union savefpu *addr)
   {
   
           fnsave((char *)addr);
   }
   
   static void
   init_xsave(void)
   {
   
           if (use_xsave)
                   return;
           if (!cpu_fxsr || (cpu_feature2 & CPUID2_XSAVE) == 0)
                   return;
           use_xsave = 1;
           TUNABLE_INT_FETCH("hw.use_xsave", &use_xsave);
   }
   
   DEFINE_IFUNC(, void, fpusave, (union savefpu *))
   {
   
           init_xsave();
           if (use_xsave)
                   return ((cpu_stdext_feature & CPUID_EXTSTATE_XSAVEOPT) != 0 ?
                       fpusave_xsaveopt : fpusave_xsave);
           if (cpu_fxsr)
                   return (fpusave_fxsave);
           return (fpusave_fnsave);
   }
   
   /*
    * Enable XSAVE if supported and allowed by user.
    * Calculate the xsave_mask.
    */
   static void
   npxinit_bsp1(void)
   {
           u_int cp[4];
           uint64_t xsave_mask_user;
   
           TUNABLE_INT_FETCH("hw.lazy_fpu_switch", &lazy_fpu_switch);
           if (!use_xsave)
                   return;
           cpuid_count(0xd, 0x0, cp);
           xsave_mask = XFEATURE_ENABLED_X87 | XFEATURE_ENABLED_SSE;
           if ((cp[0] & xsave_mask) != xsave_mask)
                   panic("CPU0 does not support X87 or SSE: %x", cp[0]);
           xsave_mask = ((uint64_t)cp[3] << 32) | cp[0];
           xsave_mask_user = xsave_mask;
           TUNABLE_QUAD_FETCH("hw.xsave_mask", &xsave_mask_user);
           xsave_mask_user |= XFEATURE_ENABLED_X87 | XFEATURE_ENABLED_SSE;
           xsave_mask &= xsave_mask_user;
           if ((xsave_mask & XFEATURE_AVX512) != XFEATURE_AVX512)
                   xsave_mask &= ~XFEATURE_AVX512;
           if ((xsave_mask & XFEATURE_MPX) != XFEATURE_MPX)
                   xsave_mask &= ~XFEATURE_MPX;
   }
   
   /*
    * Calculate the fpu save area size.
    */
   static void
   npxinit_bsp2(void)
   {
           u_int cp[4];
   
           if (use_xsave) {
                   cpuid_count(0xd, 0x0, cp);
                   cpu_max_ext_state_size = cp[1];
   
                   /*
                    * Reload the cpu_feature2, since we enabled OSXSAVE.
                    */
                   do_cpuid(1, cp);
                   cpu_feature2 = cp[2];
           } else
                   cpu_max_ext_state_size = sizeof(union savefpu);
   }
   
   /*
    * Initialize floating point unit.
    */
   void
   npxinit(bool bsp)
   {
           static union savefpu dummy;
           register_t saveintr;
           u_int mxcsr;
           u_short control;
   
           if (bsp) {
                   if (!npx_probe())
                           return;
                   npxinit_bsp1();
           }
   
           if (use_xsave) {
                   load_cr4(rcr4() | CR4_XSAVE);
                   load_xcr(XCR0, xsave_mask);
           }
   
           /*
            * XCR0 shall be set up before CPU can report the save area size.
            */
           if (bsp)
                   npxinit_bsp2();
   
           /*
            * fninit has the same h/w bugs as fnsave.  Use the detoxified
            * fnsave to throw away any junk in the fpu.  fpusave() initializes
            * the fpu.
            *
            * It is too early for critical_enter() to work on AP.
            */
           saveintr = intr_disable();
           stop_emulating();
           if (cpu_fxsr)
                   fninit();
           else
                   fnsave(&dummy);
           control = __INITIAL_NPXCW__;
           fldcw(control);
           if (cpu_fxsr) {
                   mxcsr = __INITIAL_MXCSR__;
                   ldmxcsr(mxcsr);
           }
           start_emulating();
           intr_restore(saveintr);
   }
   
   /*
    * On the boot CPU we generate a clean state that is used to
    * initialize the floating point unit when it is first used by a
    * process.
    */
   static void
   npxinitstate(void *arg __unused)
   {
           uint64_t *xstate_bv;
           register_t saveintr;
           int cp[4], i, max_ext_n;
   
           if (!hw_float)
                   return;
   
           /* Do potentially blocking operations before disabling interrupts. */
           fpu_save_area_zone = uma_zcreate("FPU_save_area",
               cpu_max_ext_state_size, NULL, NULL, NULL, NULL,
               XSAVE_AREA_ALIGN - 1, 0);
           npx_initialstate = uma_zalloc(fpu_save_area_zone, M_WAITOK | M_ZERO);
           if (use_xsave) {
                   if (xsave_mask >> 32 != 0)
                           max_ext_n = fls(xsave_mask >> 32) + 32;
                   else
                           max_ext_n = fls(xsave_mask);
                   xsave_area_desc = malloc(max_ext_n * sizeof(struct
                       xsave_area_elm_descr), M_DEVBUF, M_WAITOK | M_ZERO);
           }
   
           saveintr = intr_disable();
           stop_emulating();
   
           if (cpu_fxsr)
                   fpusave_fxsave(npx_initialstate);
           else
                   fpusave_fnsave(npx_initialstate);
           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;
   
                   /*
                    * The fninit instruction does not modify XMM
                    * registers or x87 registers (MM/ST).  The fpusave
                    * call dumped the garbage contained in the registers
                    * after reset to the initial state saved.  Clear XMM
                    * and x87 registers file image to make the startup
                    * program state and signal handler XMM/x87 register
                    * content predictable.
                    */
                   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));
   
           } else
                   bzero(npx_initialstate->sv_87.sv_ac,
                       sizeof(npx_initialstate->sv_87.sv_ac));
   
           /*
            * Create a table describing the layout of the CPU Extended
            * Save Area.  See Intel SDM rev. 075 Vol. 1 13.4.1 "Legacy
            * Region of an XSAVE Area" for the source of offsets/sizes.
            * Note that 32bit XSAVE does not use %xmm8-%xmm15, see
            * 10.5.1.2 and 13.5.2 "SSE State".
            */
           if (use_xsave) {
                   xstate_bv = (uint64_t *)((char *)(npx_initialstate + 1) +
                       offsetof(struct xstate_hdr, xstate_bv));
                   *xstate_bv = XFEATURE_ENABLED_X87 | XFEATURE_ENABLED_SSE;
   
                   /* x87 state */
                   xsave_area_desc[0].offset = 0;
                   xsave_area_desc[0].size = 160;
                   /* XMM */
                   xsave_area_desc[1].offset = 160;
                   xsave_area_desc[1].size = 288 - 160;
   
                   for (i = 2; i < max_ext_n; i++) {
                           cpuid_count(0xd, i, cp);
                           xsave_area_desc[i].offset = cp[1];
                           xsave_area_desc[i].size = cp[0];
                   }
           }
   
           start_emulating();
           intr_restore(saveintr);
   }
   SYSINIT(npxinitstate, SI_SUB_CPU, SI_ORDER_ANY, npxinitstate, NULL);
   
   /*
    * Free coprocessor (if we have it).
    */
   void
   npxexit(struct thread *td)
   {
   
           critical_enter();
           if (curthread == PCPU_GET(fpcurthread)) {
                   stop_emulating();
                   fpusave(curpcb->pcb_save);
                   start_emulating();
                   PCPU_SET(fpcurthread, NULL);
           }
           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(void)
   {
   
           if (!hw_float)
                   return (_MC_FPFMT_NODEV);
           if (cpu_fxsr)
                   return (_MC_FPFMT_XMM);
           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 choice 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 */
   };
   
   /*
    * Read the FP status and control words, then generate si_code value
    * for SIGFPE.  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.
    *
    * Some time ago, we cleared the x87 exceptions with FNCLEX there.
    * Clearing exceptions was necessary mainly to avoid IRQ13 bugs.  The
    * usermode code which understands the FPU hardware enough to enable
    * the exceptions, can also handle clearing the exception state in the
    * handler.  The only consequence of not clearing the exception is the
    * rethrow of the SIGFPE on return from the signal handler and
    * reexecution of the corresponding instruction.
    *
    * For XMM traps, the exceptions were never cleared.
    */
   int
   npxtrap_x87(void)
   {
           u_short control, status;
   
           if (!hw_float) {
                   printf(
           "npxtrap_x87: 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);
           }
           critical_exit();
           return (fpetable[status & ((~control & 0x3f) | 0x40)]);
   }
   
   int
   npxtrap_sse(void)
   {
           u_int mxcsr;
   
           if (!hw_float) {
                   printf(
           "npxtrap_sse: fpcurthread = %p, curthread = %p, hw_float = %d\n",
                          PCPU_GET(fpcurthread), curthread, hw_float);
                   panic("npxtrap from nowhere");
           }
           critical_enter();
           if (PCPU_GET(fpcurthread) != curthread)
                   mxcsr = curthread->td_pcb->pcb_save->sv_xmm.sv_env.en_mxcsr;
           else
                   stmxcsr(&mxcsr);
           critical_exit();
           return (fpetable[(mxcsr & (~mxcsr >> 7)) & 0x3f]);
   }
   
   static void
   restore_npx_curthread(struct thread *td, struct pcb *pcb)
   {
   
           /*
            * Record new context early in case frstor causes a trap.
            */
           PCPU_SET(fpcurthread, td);
   
           stop_emulating();
           if (cpu_fxsr)
                   fpu_clean_state();
   
           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.
                    *
                    * We prefer to restore the state from the actual save
                    * area in PCB instead of directly loading from
                    * npx_initialstate, to ignite the XSAVEOPT
                    * tracking engine.
                    */
                   bcopy(npx_initialstate, pcb->pcb_save, cpu_max_ext_state_size);
                   fpurstor(pcb->pcb_save);
                   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 {
                   fpurstor(pcb->pcb_save);
           }
   }
   
   /*
    * 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.
    */
   int
   npxdna(void)
   {
           struct thread *td;
   
           if (!hw_float)
                   return (0);
           td = curthread;
           critical_enter();
   
           KASSERT((curpcb->pcb_flags & PCB_NPXNOSAVE) == 0,
               ("npxdna while in fpu_kern_enter(FPU_KERN_NOCTX)"));
           if (__predict_false(PCPU_GET(fpcurthread) == td)) {
                   /*
                    * Some virtual machines seems to set %cr0.TS at
                    * arbitrary moments.  Silently clear the TS bit
                    * regardless of the eager/lazy FPU context switch
                    * mode.
                    */
                   stop_emulating();
           } else {
                   if (__predict_false(PCPU_GET(fpcurthread) != NULL)) {
                           printf(
                       "npxdna: fpcurthread = %p (%d), curthread = %p (%d)\n",
                               PCPU_GET(fpcurthread),
                               PCPU_GET(fpcurthread)->td_proc->p_pid,
                               td, td->td_proc->p_pid);
                           panic("npxdna");
                   }
                   restore_npx_curthread(td, td->td_pcb);
           }
           critical_exit();
           return (1);
   }
   
   /*
    * Wrapper for fpusave() called from context switch routines.
    *
    * 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.
    */
   void
   npxsave(union savefpu *addr)
   {
   
           stop_emulating();
           fpusave(addr);
   }
   
   void npxswitch(struct thread *td, struct pcb *pcb);
   void
   npxswitch(struct thread *td, struct pcb *pcb)
   {
   
           if (lazy_fpu_switch || (td->td_pflags & TDP_KTHREAD) != 0 ||
               !PCB_USER_FPU(pcb)) {
                   start_emulating();
                   PCPU_SET(fpcurthread, NULL);
           } else if (PCPU_GET(fpcurthread) != td) {
                   restore_npx_curthread(td, pcb);
           }
   }
   
   /*
    * Unconditionally save the current co-processor state across suspend and
    * resume.
    */
   void
   npxsuspend(union savefpu *addr)
   {
           register_t cr0;
   
           if (!hw_float)
                   return;
           if (PCPU_GET(fpcurthread) == NULL) {
                   bcopy(npx_initialstate, addr, cpu_max_ext_state_size);
                   return;
           }
           cr0 = rcr0();
           stop_emulating();
           fpusave(addr);
           load_cr0(cr0);
   }
   
   void
   npxresume(union savefpu *addr)
   {
           register_t cr0;
   
           if (!hw_float)
                   return;
   
           cr0 = rcr0();
           npxinit(false);
           stop_emulating();
           fpurstor(addr);
           load_cr0(cr0);
   }
   
   void
   npxdrop(void)
   {
           struct thread *td;
   
           /*
            * Discard pending exceptions in the !cpu_fxsr case so that unmasked
            * ones don't cause a panic on the next frstor.
            */
           if (!cpu_fxsr)
                   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;
           uint64_t *xstate_bv, bit;
           char *sa;
           int max_ext_n, i;
           int owned;
   
           if (!hw_float)
                   return (_MC_FPOWNED_NONE);
   
          pcb = td->td_pcb;
          critical_enter();
          if ((pcb->pcb_flags & PCB_NPXINITDONE) == 0) {
                  bcopy(npx_initialstate, get_pcb_user_save_pcb(pcb),
                      cpu_max_ext_state_size);
                  SET_FPU_CW(get_pcb_user_save_pcb(pcb), pcb->pcb_initial_npxcw);
                  npxuserinited(td);
                  critical_exit();
                  return (_MC_FPOWNED_PCB);
          }
          if (td == PCPU_GET(fpcurthread)) {
                  fpusave(get_pcb_user_save_pcb(pcb));
                  if (!cpu_fxsr)
                          /*
                           * fnsave initializes the FPU and destroys whatever
                           * context it contains.  Make sure the FPU owner
                           * starts with a clean state next time.
                           */
                          npxdrop();
                  owned = _MC_FPOWNED_FPU;
          } else {
                  owned = _MC_FPOWNED_PCB;
          }
          if (use_xsave) {
                  /*
                   * Handle partially saved state.
                   */
                  sa = (char *)get_pcb_user_save_pcb(pcb);
                  xstate_bv = (uint64_t *)(sa + sizeof(union savefpu) +
                      offsetof(struct xstate_hdr, xstate_bv));
                  if (xsave_mask >> 32 != 0)
                          max_ext_n = fls(xsave_mask >> 32) + 32;
                  else
                          max_ext_n = fls(xsave_mask);
                  for (i = 0; i < max_ext_n; i++) {
                          bit = 1ULL << i;
                          if ((xsave_mask & bit) == 0 || (*xstate_bv & bit) != 0)
                                  continue;
                          bcopy((char *)npx_initialstate +
                              xsave_area_desc[i].offset,
                              sa + xsave_area_desc[i].offset,
                              xsave_area_desc[i].size);
                          *xstate_bv |= bit;
                  }
          }
          critical_exit();
          return (owned);
  }
  
  void
  npxuserinited(struct thread *td)
  {
          struct pcb *pcb;
  
          CRITICAL_ASSERT(td);
          pcb = td->td_pcb;
          if (PCB_USER_FPU(pcb))
                  pcb->pcb_flags |= PCB_NPXINITDONE;
          pcb->pcb_flags |= PCB_NPXUSERINITDONE;
  }
  
  int
  npxsetxstate(struct thread *td, char *xfpustate, size_t xfpustate_size)
  {
          struct xstate_hdr *hdr, *ehdr;
          size_t len, max_len;
          uint64_t bv;
  
          /* XXXKIB should we clear all extended state in xstate_bv instead ? */
          if (xfpustate == NULL)
                  return (0);
          if (!use_xsave)
                  return (EOPNOTSUPP);
  
          len = xfpustate_size;
          if (len < sizeof(struct xstate_hdr))
                  return (EINVAL);
          max_len = cpu_max_ext_state_size - sizeof(union savefpu);
          if (len > max_len)
                  return (EINVAL);
  
          ehdr = (struct xstate_hdr *)xfpustate;
          bv = ehdr->xstate_bv;
  
          /*
           * Avoid #gp.
           */
          if (bv & ~xsave_mask)
                  return (EINVAL);
  
          hdr = (struct xstate_hdr *)(get_pcb_user_save_td(td) + 1);
  
          hdr->xstate_bv = bv;
          bcopy(xfpustate + sizeof(struct xstate_hdr),
              (char *)(hdr + 1), len - sizeof(struct xstate_hdr));
  
          return (0);
  }
  
  int
  npxsetregs(struct thread *td, union savefpu *addr, char *xfpustate,
          size_t xfpustate_size)
  {
          struct pcb *pcb;
          int error;
  
          if (!hw_float)
                  return (ENXIO);
  
          if (cpu_fxsr)
                  addr->sv_xmm.sv_env.en_mxcsr &= cpu_mxcsr_mask;
          pcb = td->td_pcb;
          error = 0;
          critical_enter();
          if (td == PCPU_GET(fpcurthread) && PCB_USER_FPU(pcb)) {
                  error = npxsetxstate(td, xfpustate, xfpustate_size);
                  if (error == 0) {
                          if (!cpu_fxsr)
                                  fnclex();       /* As in npxdrop(). */
                          bcopy(addr, get_pcb_user_save_td(td), sizeof(*addr));
                          fpurstor(get_pcb_user_save_td(td));
                          pcb->pcb_flags |= PCB_NPXUSERINITDONE | PCB_NPXINITDONE;
                  }
          } else {
                  error = npxsetxstate(td, xfpustate, xfpustate_size);
                  if (error == 0) {
                          bcopy(addr, get_pcb_user_save_td(td), sizeof(*addr));
                          npxuserinited(td);
                  }
          }
          critical_exit();
          return (error);
  }
  
  static void
  npx_fill_fpregs_xmm1(struct savexmm *sv_xmm, struct save87 *sv_87)
  {
          struct env87 *penv_87;
          struct envxmm *penv_xmm;
          struct fpacc87 *fx_reg;
          int i, st;
          uint64_t mantissa;
          uint16_t tw, exp;
          uint8_t ab_tw;
  
          penv_87 = &sv_87->sv_env;
          penv_xmm = &sv_xmm->sv_env;
  
          /* FPU control/status */
          penv_87->en_cw = penv_xmm->en_cw;
          penv_87->en_sw = penv_xmm->en_sw;
          penv_87->en_fip = penv_xmm->en_fip;
          penv_87->en_fcs = penv_xmm->en_fcs;
          penv_87->en_opcode = penv_xmm->en_opcode;
          penv_87->en_foo = penv_xmm->en_foo;
          penv_87->en_fos = penv_xmm->en_fos;
  
          /*
           * FPU registers and tags.
           * For ST(i), i = fpu_reg - top; we start with fpu_reg=7.
           */
          st = 7 - ((penv_xmm->en_sw >> 11) & 7);
          ab_tw = penv_xmm->en_tw;
          tw = 0;
          for (i = 0x80; i != 0; i >>= 1) {
                  sv_87->sv_ac[st] = sv_xmm->sv_fp[st].fp_acc;
                  tw <<= 2;
                  if (ab_tw & i) {
                          /* Non-empty - we need to check ST(i) */
                          fx_reg = &sv_xmm->sv_fp[st].fp_acc;
                          /* The first 64 bits contain the mantissa. */
                          mantissa = *((uint64_t *)fx_reg->fp_bytes);
                          /*
                           * The final 16 bits contain the sign bit and the exponent.
                           * Mask the sign bit since it is of no consequence to these
                           * tests.
                           */
                          exp = *((uint16_t *)&fx_reg->fp_bytes[8]) & 0x7fff;
                          if (exp == 0) {
                                  if (mantissa == 0)
                                          tw |= 1; /* Zero */
                                  else
                                          tw |= 2; /* Denormal */
                          } else if (exp == 0x7fff)
                                  tw |= 2; /* Infinity or NaN */
                  } else
                          tw |= 3; /* Empty */
                  st = (st - 1) & 7;
          }
          penv_87->en_tw = tw;
  }
  
  void
  npx_fill_fpregs_xmm(struct savexmm *sv_xmm, struct save87 *sv_87)
  {
  
          bzero(sv_87, sizeof(*sv_87));
          npx_fill_fpregs_xmm1(sv_xmm, sv_87);
  }
  
  void
  npx_set_fpregs_xmm(struct save87 *sv_87, struct savexmm *sv_xmm)
  {
          struct env87 *penv_87;
          struct envxmm *penv_xmm;
          int i;
  
          penv_87 = &sv_87->sv_env;
          penv_xmm = &sv_xmm->sv_env;
  
          /* FPU control/status */
          penv_xmm->en_cw = penv_87->en_cw;
          penv_xmm->en_sw = penv_87->en_sw;
          penv_xmm->en_fip = penv_87->en_fip;
          penv_xmm->en_fcs = penv_87->en_fcs;
          penv_xmm->en_opcode = penv_87->en_opcode;
          penv_xmm->en_foo = penv_87->en_foo;
          penv_xmm->en_fos = penv_87->en_fos;
  
          /*
           * FPU registers and tags.
           * Abridged  /  Full translation (values in binary), see FXSAVE spec.
           * 0            11
           * 1            00, 01, 10
           */
          penv_xmm->en_tw = 0;
          for (i = 0; i < 8; ++i) {
                  sv_xmm->sv_fp[i].fp_acc = sv_87->sv_ac[i];
                  if ((penv_87->en_tw & (3 << i * 2)) != (3 << i * 2))
                          penv_xmm->en_tw |= 1 << i;
          }
  }
  
  void
  npx_get_fsave(void *addr)
  {
          struct thread *td;
          union savefpu *sv;
  
          td = curthread;
          npxgetregs(td);
          sv = get_pcb_user_save_td(td);
          if (cpu_fxsr)
                  npx_fill_fpregs_xmm1(&sv->sv_xmm, addr);
          else
                  bcopy(sv, addr, sizeof(struct env87) +
                      sizeof(struct fpacc87[8]));
  }
  
  int
  npx_set_fsave(void *addr)
  {
          union savefpu sv;
          int error;
  
          bzero(&sv, sizeof(sv));
          if (cpu_fxsr)
                  npx_set_fpregs_xmm(addr, &sv.sv_xmm);
          else
                  bcopy(addr, &sv, sizeof(struct env87) +
                      sizeof(struct fpacc87[8]));
          error = npxsetregs(curthread, &sv, NULL, 0);
          return (error);
  }
  
  /*
   * 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));
  }
  
  static void
  fpurstor(union savefpu *addr)
  {
  
          if (use_xsave)
                  xrstor((char *)addr, xsave_mask);
          else if (cpu_fxsr)
                  fxrstor(addr);
          else
                  frstor(addr);
  }
  
  #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 */
  };
  
  DRIVER_MODULE(npxisa, isa, npxisa_driver, 0, 0);
  DRIVER_MODULE(npxisa, acpi, npxisa_driver, 0, 0);
  ISA_PNP_INFO(npxisa_ids);
  #endif /* DEV_ISA */
  
  static MALLOC_DEFINE(M_FPUKERN_CTX, "fpukern_ctx",
      "Kernel contexts for FPU state");
  
  #define FPU_KERN_CTX_NPXINITDONE 0x01
  #define FPU_KERN_CTX_DUMMY       0x02
  #define FPU_KERN_CTX_INUSE       0x04
  
  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 +
              cpu_max_ext_state_size;
          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)
  {
  
          KASSERT((ctx->flags & FPU_KERN_CTX_INUSE) == 0, ("free'ing inuse 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);
  }
  
  void
  fpu_kern_enter(struct thread *td, struct fpu_kern_ctx *ctx, u_int flags)
  {
          struct pcb *pcb;
  
          pcb = td->td_pcb;
          KASSERT((flags & FPU_KERN_NOCTX) != 0 || ctx != NULL,
              ("ctx is required when !FPU_KERN_NOCTX"));
          KASSERT(ctx == NULL || (ctx->flags & FPU_KERN_CTX_INUSE) == 0,
              ("using inuse ctx"));
          KASSERT((pcb->pcb_flags & PCB_NPXNOSAVE) == 0,
              ("recursive fpu_kern_enter while in PCB_NPXNOSAVE state"));
  
          if ((flags & FPU_KERN_NOCTX) != 0) {
                  critical_enter();
                  stop_emulating();
                  if (curthread == PCPU_GET(fpcurthread)) {
                          fpusave(curpcb->pcb_save);
                          PCPU_SET(fpcurthread, NULL);
                  } else {
                          KASSERT(PCPU_GET(fpcurthread) == NULL,
                              ("invalid fpcurthread"));
                  }
  
                  /*
                   * This breaks XSAVEOPT tracker, but
                   * PCB_NPXNOSAVE state is supposed to never need to
                   * save FPU context at all.
                   */
                  fpurstor(npx_initialstate);
                  pcb->pcb_flags |= PCB_KERNNPX | PCB_NPXNOSAVE | PCB_NPXINITDONE;
                  return;
          }
          if ((flags & FPU_KERN_KTHR) != 0 && is_fpu_kern_thread(0)) {
                  ctx->flags = FPU_KERN_CTX_DUMMY | FPU_KERN_CTX_INUSE;
                  return;
          }
          pcb = td->td_pcb;
          critical_enter();
          KASSERT(!PCB_USER_FPU(pcb) || pcb->pcb_save ==
              get_pcb_user_save_pcb(pcb), ("mangled pcb_save"));
          ctx->flags = FPU_KERN_CTX_INUSE;
          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;
          critical_exit();
  }
  
  int
  fpu_kern_leave(struct thread *td, struct fpu_kern_ctx *ctx)
  {
          struct pcb *pcb;
  
          pcb = td->td_pcb;
  
          if ((pcb->pcb_flags & PCB_NPXNOSAVE) != 0) {
                  KASSERT(ctx == NULL, ("non-null ctx after FPU_KERN_NOCTX"));
                  KASSERT(PCPU_GET(fpcurthread) == NULL,
                      ("non-NULL fpcurthread for PCB_NPXNOSAVE"));
                  CRITICAL_ASSERT(td);
  
                  pcb->pcb_flags &= ~(PCB_NPXNOSAVE | PCB_NPXINITDONE);
                  start_emulating();
          } else {
                  KASSERT((ctx->flags & FPU_KERN_CTX_INUSE) != 0,
                      ("leaving not inuse ctx"));
                  ctx->flags &= ~FPU_KERN_CTX_INUSE;
  
                  if (is_fpu_kern_thread(0) &&
                      (ctx->flags & FPU_KERN_CTX_DUMMY) != 0)
                          return (0);
                  KASSERT((ctx->flags & FPU_KERN_CTX_DUMMY) == 0,
                      ("dummy ctx"));
                  critical_enter();
                  if (curthread == PCPU_GET(fpcurthread))
                          npxdrop();
                  pcb->pcb_save = ctx->prev;
          }
  
          if (pcb->pcb_save == get_pcb_user_save_pcb(pcb)) {
                  if ((pcb->pcb_flags & PCB_NPXUSERINITDONE) != 0) {
                          pcb->pcb_flags |= PCB_NPXINITDONE;
                          if ((pcb->pcb_flags & PCB_KERNNPX_THR) == 0)
                                  pcb->pcb_flags &= ~PCB_KERNNPX;
                  } else if ((pcb->pcb_flags & PCB_KERNNPX_THR) == 0)
                          pcb->pcb_flags &= ~(PCB_NPXINITDONE | 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"));
          }
          critical_exit();
          return (0);
  }
  
  int
  fpu_kern_thread(u_int flags)
  {
  
          KASSERT((curthread->td_pflags & TDP_KTHREAD) != 0,
              ("Only kthread may use fpu_kern_thread"));
          KASSERT(curpcb->pcb_save == get_pcb_user_save_pcb(curpcb),
              ("mangled pcb_save"));
          KASSERT(PCB_USER_FPU(curpcb), ("recursive call"));
  
          curpcb->pcb_flags |= PCB_KERNNPX | PCB_KERNNPX_THR;
          return (0);
  }
  
  int
  is_fpu_kern_thread(u_int flags)
  {
  
          if ((curthread->td_pflags & TDP_KTHREAD) == 0)
                  return (0);
          return ((curpcb->pcb_flags & PCB_KERNNPX_THR) != 0);
  }
  
  /*
   * FPU save area alloc/free/init utility routines
   */
  union savefpu *
  fpu_save_area_alloc(void)
  {
  
          return (uma_zalloc(fpu_save_area_zone, M_WAITOK));
  }
  
  void
  fpu_save_area_free(union savefpu *fsa)
  {
  
          uma_zfree(fpu_save_area_zone, fsa);
  }
  
  void
  fpu_save_area_reset(union savefpu *fsa)
  {
  
          bcopy(npx_initialstate, fsa, cpu_max_ext_state_size);
  }

Cache object: a4ffae0c42405371b715a41f1998908d