[apple/xnu.git] / osfmk / i386 / fpu.c

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/*
 * @OSF_COPYRIGHT@
 */
/* 
 * Mach Operating System
 * Copyright (c) 1992-1990 Carnegie Mellon University
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 * 
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 * 
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */
/*
 */

#include <platforms.h>

#include <mach/exception_types.h>
#include <mach/i386/thread_status.h>
#include <mach/i386/fp_reg.h>

#include <kern/mach_param.h>
#include <kern/processor.h>
#include <kern/thread.h>
#include <kern/zalloc.h>
#include <kern/misc_protos.h>
#include <kern/spl.h>
#include <kern/assert.h>

#include <i386/thread.h>
#include <i386/fpu.h>
#include <i386/trap.h>
#include <architecture/i386/pio.h>
#include <i386/cpuid.h>
#include <i386/misc_protos.h>
#include <i386/proc_reg.h>

int             fp_kind = FP_NO;        /* not inited */
zone_t          ifps_zone;              /* zone for FPU save area */

#define ALIGNED(addr,size)      (((unsigned)(addr)&((size)-1))==0)

/* Forward */

extern void             fpinit(void);
extern void             fp_save(
                                thread_t        thr_act);
extern void             fp_load(
                                thread_t        thr_act);

static void configure_mxcsr_capability_mask(struct x86_fpsave_state *ifps);

struct x86_fpsave_state starting_fp_state;


/* Global MXCSR capability bitmask */
static unsigned int mxcsr_capability_mask;

/*
 * Determine the MXCSR capability mask, which allows us to mask off any
 * potentially unsafe "reserved" bits before restoring the FPU context.
 * *Not* per-cpu, assumes symmetry.
 */
static void
configure_mxcsr_capability_mask(struct x86_fpsave_state *ifps)
{
        /* FXSAVE requires a 16 byte aligned store */
        assert(ALIGNED(ifps,16));
        /* Clear, to prepare for the diagnostic FXSAVE */
        bzero(ifps, sizeof(*ifps));
        /* Disable FPU/SSE Device Not Available exceptions */
        clear_ts();

        __asm__ volatile("fxsave %0" : "=m" (ifps->fx_save_state));
        mxcsr_capability_mask = ifps->fx_save_state.fx_MXCSR_MASK;

        /* Set default mask value if necessary */
        if (mxcsr_capability_mask == 0)
                mxcsr_capability_mask = 0xffbf;
        
        /* Re-enable FPU/SSE DNA exceptions */
        set_ts();
}

/*
 * Allocate and initialize FP state for current thread.
 * Don't load state.
 */
static struct x86_fpsave_state *
fp_state_alloc(void)
{
        struct x86_fpsave_state *ifps;

        ifps = (struct x86_fpsave_state *)zalloc(ifps_zone);
        assert(ALIGNED(ifps,16));
        bzero((char *)ifps, sizeof *ifps);

        return ifps;
}

static inline void
fp_state_free(struct x86_fpsave_state *ifps)
{
        zfree(ifps_zone, ifps);
}


/*
 * Look for FPU and initialize it.
 * Called on each CPU.
 */
void
init_fpu(void)
{
        unsigned short  status, control;

        /*
         * Check for FPU by initializing it,
         * then trying to read the correct bit patterns from
         * the control and status registers.
         */
        set_cr0((get_cr0() & ~(CR0_EM|CR0_TS)) | CR0_NE);       /* allow use of FPU */

        fninit();
        status = fnstsw();
        fnstcw(&control);

        if ((status & 0xff) == 0 &&
            (control & 0x103f) == 0x3f) 
        {
            /* Use FPU save/restore instructions if available */
                if (cpuid_features() & CPUID_FEATURE_FXSR) {
                        fp_kind = FP_FXSR;
                        set_cr4(get_cr4() | CR4_FXS);
                        printf("Enabling XMM register save/restore");
                        /* And allow SIMD instructions if present */
                        if (cpuid_features() & CPUID_FEATURE_SSE) {
                        printf(" and SSE/SSE2");
                        set_cr4(get_cr4() | CR4_XMM);
                        }
                        printf(" opcodes\n");
            } else
                        panic("fpu is not FP_FXSR");

            /*
             * initialze FPU to normal starting 
             * position so that we can take a snapshot
             * of that state and store it for future use
             * when we're asked for the FPU state of a 
             * thread, and it hasn't initiated any yet
             */
             fpinit();
             fxsave(&starting_fp_state.fx_save_state);

             /*
              * Trap wait instructions.  Turn off FPU for now.
              */
             set_cr0(get_cr0() | CR0_TS | CR0_MP);
        }
        else
        {
            /*
             * NO FPU.
             */
                panic("fpu is not FP_FXSR");
        }
}

/*
 * Initialize FP handling.
 */
void
fpu_module_init(void)
{
        struct x86_fpsave_state *new_ifps;
        
        ifps_zone = zinit(sizeof(struct x86_fpsave_state),
                          THREAD_MAX * sizeof(struct x86_fpsave_state),
                          THREAD_CHUNK * sizeof(struct x86_fpsave_state),
                          "x86 fpsave state");
        new_ifps = fp_state_alloc();
        /* Determine MXCSR reserved bits */
        configure_mxcsr_capability_mask(new_ifps);
        fp_state_free(new_ifps);
}

/*
 * Free a FPU save area.
 * Called only when thread terminating - no locking necessary.
 */
void
fpu_free(fps)
        struct x86_fpsave_state *fps;
{
        fp_state_free(fps);
}

/*
 * Set the floating-point state for a thread based 
 * on the FXSave formatted data. This is basically  
 * the same as fpu_set_state except it uses the 
 * expanded data structure. 
 * If the thread is not the current thread, it is
 * not running (held).  Locking needed against
 * concurrent fpu_set_state or fpu_get_state.
 */
kern_return_t
fpu_set_fxstate(
        thread_t        thr_act,
        thread_state_t  tstate)
{
        struct x86_fpsave_state *ifps;
        struct x86_fpsave_state *new_ifps;
        x86_float_state64_t     *state;
        pcb_t   pcb;

        if (fp_kind == FP_NO)
                return KERN_FAILURE;

        state = (x86_float_state64_t *)tstate;

        assert(thr_act != THREAD_NULL);
        pcb = thr_act->machine.pcb;

        if (state == NULL) {
                /*
                 * new FPU state is 'invalid'.
                 * Deallocate the fp state if it exists.
                 */
                simple_lock(&pcb->lock);

                ifps = pcb->ifps;
                pcb->ifps = 0;

                simple_unlock(&pcb->lock);

                if (ifps != 0)
                        fp_state_free(ifps);
        } else {
                /*
                 * Valid state.  Allocate the fp state if there is none.
                 */
                new_ifps = 0;
        Retry:
                simple_lock(&pcb->lock);

                ifps = pcb->ifps;
                if (ifps == 0) {
                        if (new_ifps == 0) {
                                simple_unlock(&pcb->lock);
                                new_ifps = fp_state_alloc();
                                goto Retry;
                        }
                        ifps = new_ifps;
                        new_ifps = 0;
                        pcb->ifps = ifps;
                }
                /*
                 * now copy over the new data.
                 */
                bcopy((char *)&state->fpu_fcw,
                      (char *)&ifps->fx_save_state, sizeof(struct x86_fx_save));

                /* XXX The layout of the state set from user-space may need to be
                 * validated for consistency.
                 */
                ifps->fp_save_layout = thread_is_64bit(thr_act) ? FXSAVE64 : FXSAVE32;
                /*
                 * Clear any reserved bits in the MXCSR to prevent a GPF
                 * when issuing an FXRSTOR.
                 */
                ifps->fx_save_state.fx_MXCSR &= mxcsr_capability_mask;

                simple_unlock(&pcb->lock);

                if (new_ifps != 0)
                        fp_state_free(new_ifps);
        }
        return KERN_SUCCESS;
}

/*
 * Get the floating-point state for a thread.
 * If the thread is not the current thread, it is
 * not running (held).  Locking needed against
 * concurrent fpu_set_state or fpu_get_state.
 */
kern_return_t
fpu_get_fxstate(
        thread_t        thr_act,
        thread_state_t  tstate)
{
        struct x86_fpsave_state *ifps;
        x86_float_state64_t     *state;
        kern_return_t   ret = KERN_FAILURE;
        pcb_t   pcb;

        if (fp_kind == FP_NO)
            return KERN_FAILURE;

        state = (x86_float_state64_t *)tstate;

        assert(thr_act != THREAD_NULL);
        pcb = thr_act->machine.pcb;

        simple_lock(&pcb->lock);

        ifps = pcb->ifps;
        if (ifps == 0) {
                /*
                 * No valid floating-point state.
                 */
                bcopy((char *)&starting_fp_state.fx_save_state,
                      (char *)&state->fpu_fcw, sizeof(struct x86_fx_save));

                simple_unlock(&pcb->lock);

                return KERN_SUCCESS;
        }
        /*
         * Make sure we`ve got the latest fp state info
         * If the live fpu state belongs to our target
         */
        if (thr_act == current_thread())
        {
                boolean_t       intr;

                intr = ml_set_interrupts_enabled(FALSE);

                clear_ts();
                fp_save(thr_act);
                clear_fpu();

                (void)ml_set_interrupts_enabled(intr);
        }
        if (ifps->fp_valid) {
                bcopy((char *)&ifps->fx_save_state,
                      (char *)&state->fpu_fcw, sizeof(struct x86_fx_save));
                ret = KERN_SUCCESS;
        }
        simple_unlock(&pcb->lock);

        return ret;
}


/*
 * the child thread is 'stopped' with the thread
 * mutex held and is currently not known by anyone
 * so no way for fpu state to get manipulated by an
 * outside agency -> no need for pcb lock
 */

void
fpu_dup_fxstate(
        thread_t        parent,
        thread_t        child)
{
        struct x86_fpsave_state *new_ifps = NULL;
        boolean_t       intr;
        pcb_t           ppcb;

        ppcb = parent->machine.pcb;

        if (ppcb->ifps == NULL)
                return;

        if (child->machine.pcb->ifps)
                panic("fpu_dup_fxstate: child's ifps non-null");

        new_ifps = fp_state_alloc();

        simple_lock(&ppcb->lock);

        if (ppcb->ifps != NULL) {
                /*
                 * Make sure we`ve got the latest fp state info
                 */
                intr = ml_set_interrupts_enabled(FALSE);

                clear_ts();
                fp_save(parent);
                clear_fpu();

                (void)ml_set_interrupts_enabled(intr);

                if (ppcb->ifps->fp_valid) {
                        child->machine.pcb->ifps = new_ifps;

                        bcopy((char *)&(ppcb->ifps->fx_save_state),
                              (char *)&(child->machine.pcb->ifps->fx_save_state), sizeof(struct x86_fx_save));

                        new_ifps->fp_save_layout = ppcb->ifps->fp_save_layout;
                        /*
                         * Clear any reserved bits in the MXCSR to prevent a GPF
                         * when issuing an FXRSTOR.
                         */
                        new_ifps->fx_save_state.fx_MXCSR &= mxcsr_capability_mask;
                        new_ifps = NULL;
                }
        }
        simple_unlock(&ppcb->lock);

        if (new_ifps != NULL)
                fp_state_free(new_ifps);
}


/*
 * Initialize FPU.
 *
 */
void
fpinit(void)
{
        unsigned short  control;

        clear_ts();
        fninit();
        fnstcw(&control);
        control &= ~(FPC_PC|FPC_RC); /* Clear precision & rounding control */
        control |= (FPC_PC_64 |         /* Set precision */ 
                        FPC_RC_RN |     /* round-to-nearest */
                        FPC_ZE |        /* Suppress zero-divide */
                        FPC_OE |        /*  and overflow */
                        FPC_UE |        /*  underflow */
                        FPC_IE |        /* Allow NaNQs and +-INF */
                        FPC_DE |        /* Allow denorms as operands  */
                        FPC_PE);        /* No trap for precision loss */
        fldcw(control);

        /* Initialize SSE/SSE2 */
        __builtin_ia32_ldmxcsr(0x1f80);
}

/*
 * Coprocessor not present.
 */

void
fpnoextflt(void)
{
        boolean_t       intr;

        intr = ml_set_interrupts_enabled(FALSE);

        clear_ts();                     /*  Enable FPU use */

        if (get_interrupt_level()) {
                /*
                 * Save current coprocessor context if valid
                 * Initialize coprocessor live context
                 */
                fp_save(current_thread());
                fpinit();
        } else {
                /*
                 * Load this thread`s state into coprocessor live context.
                 */
                fp_load(current_thread());
        }

        (void)ml_set_interrupts_enabled(intr);
}

/*
 * FPU overran end of segment.
 * Re-initialize FPU.  Floating point state is not valid.
 */

void
fpextovrflt(void)
{
        thread_t        thr_act = current_thread();
        pcb_t           pcb;
        struct x86_fpsave_state *ifps;
        boolean_t       intr;

        intr = ml_set_interrupts_enabled(FALSE);

        if (get_interrupt_level())
                panic("FPU segment overrun exception at interrupt context\n");
        if (current_task() == kernel_task)
                panic("FPU segment overrun exception in kernel thread context\n");

        /*
         * This is a non-recoverable error.
         * Invalidate the thread`s FPU state.
         */
        pcb = thr_act->machine.pcb;
        simple_lock(&pcb->lock);
        ifps = pcb->ifps;
        pcb->ifps = 0;
        simple_unlock(&pcb->lock);

        /*
         * Re-initialize the FPU.
         */
        clear_ts();
        fninit();

        /*
         * And disable access.
         */
        clear_fpu();

        (void)ml_set_interrupts_enabled(intr);

        if (ifps)
            zfree(ifps_zone, ifps);

        /*
         * Raise exception.
         */
        i386_exception(EXC_BAD_ACCESS, VM_PROT_READ|VM_PROT_EXECUTE, 0);
        /*NOTREACHED*/
}

/*
 * FPU error. Called by AST.
 */

void
fpexterrflt(void)
{
        thread_t        thr_act = current_thread();
        struct x86_fpsave_state *ifps = thr_act->machine.pcb->ifps;
        boolean_t       intr;

        intr = ml_set_interrupts_enabled(FALSE);

        if (get_interrupt_level())
                panic("FPU error exception at interrupt context\n");
        if (current_task() == kernel_task)
                panic("FPU error exception in kernel thread context\n");

        /*
         * Save the FPU state and turn off the FPU.
         */
        fp_save(thr_act);

        (void)ml_set_interrupts_enabled(intr);

        /*
         * Raise FPU exception.
         * Locking not needed on pcb->ifps,
         * since thread is running.
         */
        i386_exception(EXC_ARITHMETIC,
                       EXC_I386_EXTERR,
                       ifps->fx_save_state.fx_status);

        /*NOTREACHED*/
}

/*
 * Save FPU state.
 *
 * Locking not needed:
 * .    if called from fpu_get_state, pcb already locked.
 * .    if called from fpnoextflt or fp_intr, we are single-cpu
 * .    otherwise, thread is running.
 * N.B.: Must be called with interrupts disabled
 */

void
fp_save(
        thread_t        thr_act)
{
        pcb_t pcb = thr_act->machine.pcb;
        struct x86_fpsave_state *ifps = pcb->ifps;

        if (ifps != 0 && !ifps->fp_valid) {
                assert((get_cr0() & CR0_TS) == 0);
                /* registers are in FPU */
                ifps->fp_valid = TRUE;

                if (!thread_is_64bit(thr_act)) {
                        /* save the compatibility/legacy mode XMM+x87 state */
                        fxsave(&ifps->fx_save_state);
                        ifps->fp_save_layout = FXSAVE32;
                }
                else {
                        fxsave64(&ifps->fx_save_state);
                        ifps->fp_save_layout = FXSAVE64;
                }
        }
}

/*
 * Restore FPU state from PCB.
 *
 * Locking not needed; always called on the current thread.
 */

void
fp_load(
        thread_t        thr_act)
{
        pcb_t pcb = thr_act->machine.pcb;
        struct x86_fpsave_state *ifps;

        ifps = pcb->ifps;
        if (ifps == 0 || ifps->fp_valid == FALSE) {
                if (ifps == 0) {
                        /* FIXME: This allocation mechanism should be revised
                         * for scenarios where interrupts are disabled.
                         */
                        ifps = fp_state_alloc();
                        pcb->ifps = ifps;
                }
                fpinit();
        } else {
                assert(ifps->fp_save_layout == FXSAVE32 || ifps->fp_save_layout == FXSAVE64);
                if (ifps->fp_save_layout == FXSAVE32) {
                        /* Restore the compatibility/legacy mode XMM+x87 state */
                        fxrstor(&ifps->fx_save_state);
                }
                else if (ifps->fp_save_layout == FXSAVE64) {
                        fxrstor64(&ifps->fx_save_state);
                }
        }
        ifps->fp_valid = FALSE;         /* in FPU */
}



/*
 * fpflush(thread_t)
 *      Flush the current act's state, if needed
 *      (used by thread_terminate_self to ensure fp faults
 *      aren't satisfied by overly general trap code in the
 *      context of the reaper thread)
 */
void
fpflush(__unused thread_t thr_act)
{
        /* not needed on MP x86s; fp not lazily evaluated */
}

/*
 * SSE arithmetic exception handling code.
 * Basically the same as the x87 exception handler with a different subtype
 */

void
fpSSEexterrflt(void)
{
        thread_t        thr_act = current_thread();
        struct x86_fpsave_state *ifps = thr_act->machine.pcb->ifps;
        boolean_t       intr;

        intr = ml_set_interrupts_enabled(FALSE);

        if (get_interrupt_level())
                panic("SSE exception at interrupt context\n");
        if (current_task() == kernel_task)
                panic("SSE exception in kernel thread context\n");

        /*
         * Save the FPU state and turn off the FPU.
         */
        fp_save(thr_act);

        (void)ml_set_interrupts_enabled(intr);
        /*
         * Raise FPU exception.
         * Locking not needed on pcb->ifps,
         * since thread is running.
         */
        assert(ifps->fp_save_layout == FXSAVE32 || ifps->fp_save_layout == FXSAVE64);
        i386_exception(EXC_ARITHMETIC,
                       EXC_I386_SSEEXTERR,
                       ifps->fx_save_state.fx_status);
        /*NOTREACHED*/
}


void
fp_setvalid(boolean_t value) {
        thread_t        thr_act = current_thread();
        struct x86_fpsave_state *ifps = thr_act->machine.pcb->ifps;

        if (ifps) {
                ifps->fp_valid = value;

                if (value == TRUE)
                        clear_fpu();
        }
}