/*
 *  linux/arch/i386/kernel/i387.c
 *
 *  Copyright (C) 1994 Linus Torvalds
 *
 *  Pentium III FXSR, SSE support
 *  General FPU state handling cleanups
 *      Gareth Hughes <gareth@valinux.com>, May 2000
 */

#include <linux/config.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <asm/processor.h>
#include <asm/i387.h>
#include <asm/math_emu.h>
#include <asm/sigcontext.h>
#include <asm/user.h>
#include <asm/ptrace.h>
#include <asm/uaccess.h>

#ifdef CONFIG_MATH_EMULATION
#define HAVE_HWFP (boot_cpu_data.hard_math)
#else
#define HAVE_HWFP 1
#endif

static union i387_union empty_fpu_state;

void __init boot_init_fpu(void)
{
        memset(&empty_fpu_state, 0, sizeof(union i387_union));

        if (!cpu_has_fxsr) {
                empty_fpu_state.fsave.cwd = 0xffff037f;
                empty_fpu_state.fsave.swd = 0xffff0000;
                empty_fpu_state.fsave.twd = 0xffffffff;
                empty_fpu_state.fsave.fos = 0xffff0000;
        } else {
                empty_fpu_state.fxsave.cwd = 0x37f;
                if (cpu_has_xmm)
                        empty_fpu_state.fxsave.mxcsr = 0x1f80;
        }
}

void load_empty_fpu(struct task_struct * tsk)
{
        memcpy(&tsk->thread.i387, &empty_fpu_state, sizeof(union i387_union));
}

/*
 * The _current_ task is using the FPU for the first time
 * so initialize it and set the mxcsr to its default
 * value at reset if we support XMM instructions and then
 * remeber the current task has used the FPU.
 */
void init_fpu(void)
{
        if (cpu_has_fxsr)
                asm volatile("fxrstor %0" : : "m" (empty_fpu_state.fxsave));
        else
                __asm__("fninit");
        current->used_math = 1;
}

/*
 * FPU lazy state save handling.
 */

static inline void __save_init_fpu( struct task_struct *tsk )
{
        if ( cpu_has_fxsr ) {
                asm volatile( "fxsave %0 ; fnclex"
                              : "=m" (tsk->thread.i387.fxsave) );
        } else {
                asm volatile( "fnsave %0 ; fwait"
                              : "=m" (tsk->thread.i387.fsave) );
        }
        tsk->flags &= ~PF_USEDFPU;
}

void save_init_fpu( struct task_struct *tsk )
{
        __save_init_fpu(tsk);
        stts();
}

void kernel_fpu_begin(void)
{
        struct task_struct *tsk = current;

        if (tsk->flags & PF_USEDFPU) {
                __save_init_fpu(tsk);
                return;
        }
        clts();
}

void restore_fpu( struct task_struct *tsk )
{
        if ( cpu_has_fxsr ) {
                asm volatile( "fxrstor %0"
                              : : "m" (tsk->thread.i387.fxsave) );
        } else {
                asm volatile( "frstor %0"
                              : : "m" (tsk->thread.i387.fsave) );
        }
}

/*
 * FPU tag word conversions.
 */

static inline unsigned short twd_i387_to_fxsr( unsigned short twd )
{
        unsigned int tmp; /* to avoid 16 bit prefixes in the code */
 
        /* Transform each pair of bits into 01 (valid) or 00 (empty) */
        tmp = ~twd;
        tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
        /* and move the valid bits to the lower byte. */
        tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
        tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
        tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
        return tmp;
}

static inline unsigned long twd_fxsr_to_i387( struct i387_fxsave_struct *fxsave )
{
        struct _fpxreg *st = NULL;
        unsigned long tos = (fxsave->swd >> 11) & 7;
        unsigned long twd = (unsigned long) fxsave->twd;
        unsigned long tag;
        unsigned long ret = 0xffff0000;
        int i;

#define FPREG_ADDR(f, n)        ((void *)&(f)->st_space + (n) * 16);

        for ( i = 0 ; i < 8 ; i++ ) {
                if ( twd & 0x1 ) {
                        st = FPREG_ADDR( fxsave, (i - tos) & 7 );

                        switch ( st->exponent & 0x7fff ) {
                        case 0x7fff:
                                tag = 2;                /* Special */
                                break;
                        case 0x0000:
                                if ( !st->significand[0] &&
                                     !st->significand[1] &&
                                     !st->significand[2] &&
                                     !st->significand[3] ) {
                                        tag = 1;        /* Zero */
                                } else {
                                        tag = 2;        /* Special */
                                }
                                break;
                        default:
                                if ( st->significand[3] & 0x8000 ) {
                                        tag = 0;        /* Valid */
                                } else {
                                        tag = 2;        /* Special */
                                }
                                break;
                        }
                } else {
                        tag = 3;                        /* Empty */
                }
                ret |= (tag << (2 * i));
                twd = twd >> 1;
        }
        return ret;
}

/*
 * FPU state interaction.
 */

unsigned short get_fpu_cwd( struct task_struct *tsk )
{
        if ( cpu_has_fxsr ) {
                return tsk->thread.i387.fxsave.cwd;
        } else {
                return (unsigned short)tsk->thread.i387.fsave.cwd;
        }
}

unsigned short get_fpu_swd( struct task_struct *tsk )
{
        if ( cpu_has_fxsr ) {
                return tsk->thread.i387.fxsave.swd;
        } else {
                return (unsigned short)tsk->thread.i387.fsave.swd;
        }
}

unsigned short get_fpu_twd( struct task_struct *tsk )
{
        if ( cpu_has_fxsr ) {
                return tsk->thread.i387.fxsave.twd;
        } else {
                return (unsigned short)tsk->thread.i387.fsave.twd;
        }
}

unsigned short get_fpu_mxcsr( struct task_struct *tsk )
{
        if ( cpu_has_xmm ) {
                return tsk->thread.i387.fxsave.mxcsr;
        } else {
                return 0x1f80;
        }
}

void set_fpu_cwd( struct task_struct *tsk, unsigned short cwd )
{
        if ( cpu_has_fxsr ) {
                tsk->thread.i387.fxsave.cwd = cwd;
        } else {
                tsk->thread.i387.fsave.cwd = ((long)cwd | 0xffff0000);
        }
}

void set_fpu_swd( struct task_struct *tsk, unsigned short swd )
{
        if ( cpu_has_fxsr ) {
                tsk->thread.i387.fxsave.swd = swd;
        } else {
                tsk->thread.i387.fsave.swd = ((long)swd | 0xffff0000);
        }
}

void set_fpu_twd( struct task_struct *tsk, unsigned short twd )
{
        if ( cpu_has_fxsr ) {
                tsk->thread.i387.fxsave.twd = twd_i387_to_fxsr(twd);
        } else {
                tsk->thread.i387.fsave.twd = ((long)twd | 0xffff0000);
        }
}

void set_fpu_mxcsr( struct task_struct *tsk, unsigned short mxcsr )
{
        if ( cpu_has_xmm ) {
                tsk->thread.i387.fxsave.mxcsr = (mxcsr & 0xffbf);
        }
}

/*
 * FXSR floating point environment conversions.
 */

static inline int convert_fxsr_to_user( struct _fpstate *buf,
                                        struct i387_fxsave_struct *fxsave )
{
        unsigned long env[7];
        struct _fpreg *to;
        struct _fpxreg *from;
        int i;

        env[0] = (unsigned long)fxsave->cwd | 0xffff0000;
        env[1] = (unsigned long)fxsave->swd | 0xffff0000;
        env[2] = twd_fxsr_to_i387(fxsave);
        env[3] = fxsave->fip;
        env[4] = fxsave->fcs | ((unsigned long)fxsave->fop << 16);
        env[5] = fxsave->foo;
        env[6] = fxsave->fos;

        if ( __copy_to_user( buf, env, 7 * sizeof(unsigned long) ) )
                return 1;

        to = &buf->_st[0];
        from = (struct _fpxreg *) &fxsave->st_space[0];
        for ( i = 0 ; i < 8 ; i++, to++, from++ ) {
                if ( __copy_to_user( to, from, sizeof(*to) ) )
                        return 1;
        }
        return 0;
}

static inline int convert_fxsr_from_user( struct i387_fxsave_struct *fxsave,
                                          struct _fpstate *buf )
{
        unsigned long env[7];
        struct _fpxreg *to;
        struct _fpreg *from;
        int i;

        if ( __copy_from_user( env, buf, 7 * sizeof(long) ) )
                return 1;

        fxsave->cwd = (unsigned short)(env[0] & 0xffff);
        fxsave->swd = (unsigned short)(env[1] & 0xffff);
        fxsave->twd = twd_i387_to_fxsr((unsigned short)(env[2] & 0xffff));
        fxsave->fip = env[3];
        fxsave->fop = (unsigned short)((env[4] & 0xffff0000) >> 16);
        fxsave->fcs = (env[4] & 0xffff);
        fxsave->foo = env[5];
        fxsave->fos = env[6];

        to = (struct _fpxreg *) &fxsave->st_space[0];
        from = &buf->_st[0];
        for ( i = 0 ; i < 8 ; i++, to++, from++ ) {
                if ( __copy_from_user( to, from, sizeof(*from) ) )
                        return 1;
        }
        return 0;
}

/*
 * Signal frame handlers.
 */

static inline int save_i387_fsave( struct _fpstate *buf )
{
        struct task_struct *tsk = current;

        unlazy_fpu( tsk );
        tsk->thread.i387.fsave.status = tsk->thread.i387.fsave.swd;
        if ( __copy_to_user( buf, &tsk->thread.i387.fsave,
                             sizeof(struct i387_fsave_struct) ) )
                return -1;
        return 1;
}

static inline int save_i387_fxsave( struct _fpstate *buf )
{
        struct task_struct *tsk = current;
        int err = 0;

        unlazy_fpu( tsk );

        if ( convert_fxsr_to_user( buf, &tsk->thread.i387.fxsave ) )
                return -1;

        err |= __put_user( tsk->thread.i387.fxsave.swd, &buf->status );
        err |= __put_user( X86_FXSR_MAGIC, &buf->magic );
        if ( err )
                return -1;

        if ( __copy_to_user( &buf->_fxsr_env[0], &tsk->thread.i387.fxsave,
                             sizeof(struct i387_fxsave_struct) ) )
                return -1;
        return 1;
}

int save_i387( struct _fpstate *buf )
{
        if ( !current->used_math )
                return 0;

        /* This will cause a "finit" to be triggered by the next
         * attempted FPU operation by the 'current' process.
         */
        current->used_math = 0;

        if ( HAVE_HWFP ) {
                if ( cpu_has_fxsr ) {
                        return save_i387_fxsave( buf );
                } else {
                        return save_i387_fsave( buf );
                }
        } else {
                return save_i387_soft( &current->thread.i387.soft, buf );
        }
}

static inline int restore_i387_fsave( struct _fpstate *buf )
{
        struct task_struct *tsk = current;
        clear_fpu( tsk );
        return __copy_from_user( &tsk->thread.i387.fsave, buf,
                                 sizeof(struct i387_fsave_struct) );
}

static inline int restore_i387_fxsave( struct _fpstate *buf )
{
        int err;
        struct task_struct *tsk = current;
        clear_fpu( tsk );
        err = __copy_from_user( &tsk->thread.i387.fxsave, &buf->_fxsr_env[0],
                                sizeof(struct i387_fxsave_struct) );
        /* mxcsr bit 6 and 31-16 must be zero for security reasons */
        tsk->thread.i387.fxsave.mxcsr &= 0xffbf;
        return err ? 1 : convert_fxsr_from_user( &tsk->thread.i387.fxsave, buf );
}

int restore_i387( struct _fpstate *buf )
{
        int err;

        if ( HAVE_HWFP ) {
                if ( cpu_has_fxsr ) {
                        err =  restore_i387_fxsave( buf );
                } else {
                        err = restore_i387_fsave( buf );
                }
        } else {
                err = restore_i387_soft( &current->thread.i387.soft, buf );
        }
        current->used_math = 1;
        return err;
}

/*
 * ptrace request handlers.
 */

static inline int get_fpregs_fsave( struct user_i387_struct *buf,
                                    struct task_struct *tsk )
{
        return __copy_to_user( buf, &tsk->thread.i387.fsave,
                               sizeof(struct user_i387_struct) );
}

static inline int get_fpregs_fxsave( struct user_i387_struct *buf,
                                     struct task_struct *tsk )
{
        return convert_fxsr_to_user( (struct _fpstate *)buf,
                                     &tsk->thread.i387.fxsave );
}

int get_fpregs( struct user_i387_struct *buf, struct task_struct *tsk )
{
        if ( HAVE_HWFP ) {
                if ( cpu_has_fxsr ) {
                        return get_fpregs_fxsave( buf, tsk );
                } else {
                        return get_fpregs_fsave( buf, tsk );
                }
        } else {
                return save_i387_soft( &tsk->thread.i387.soft,
                                       (struct _fpstate *)buf );
        }
}

static inline int set_fpregs_fsave( struct task_struct *tsk,
                                    struct user_i387_struct *buf )
{
        return __copy_from_user( &tsk->thread.i387.fsave, buf,
                                 sizeof(struct user_i387_struct) );
}

static inline int set_fpregs_fxsave( struct task_struct *tsk,
                                     struct user_i387_struct *buf )
{
        return convert_fxsr_from_user( &tsk->thread.i387.fxsave,
                                       (struct _fpstate *)buf );
}

int set_fpregs( struct task_struct *tsk, struct user_i387_struct *buf )
{
        if ( HAVE_HWFP ) {
                if ( cpu_has_fxsr ) {
                        return set_fpregs_fxsave( tsk, buf );
                } else {
                        return set_fpregs_fsave( tsk, buf );
                }
        } else {
                return restore_i387_soft( &tsk->thread.i387.soft,
                                          (struct _fpstate *)buf );
        }
}

int get_fpxregs( struct user_fxsr_struct *buf, struct task_struct *tsk )
{
        if ( cpu_has_fxsr ) {
                if (__copy_to_user( (void *)buf, &tsk->thread.i387.fxsave,
                                    sizeof(struct user_fxsr_struct) ))
                        return -EFAULT;
                return 0;
        } else {
                return -EIO;
        }
}

int set_fpxregs( struct task_struct *tsk, struct user_fxsr_struct *buf )
{
        if ( cpu_has_fxsr ) {
                __copy_from_user( &tsk->thread.i387.fxsave, (void *)buf,
                                  sizeof(struct user_fxsr_struct) );
                /* mxcsr bit 6 and 31-16 must be zero for security reasons */
                tsk->thread.i387.fxsave.mxcsr &= 0xffbf;
                return 0;
        } else {
                return -EIO;
        }
}

/*
 * FPU state for core dumps.
 */

static inline void copy_fpu_fsave( struct task_struct *tsk,
                                   struct user_i387_struct *fpu )
{
        memcpy( fpu, &tsk->thread.i387.fsave,
                sizeof(struct user_i387_struct) );
}

static inline void copy_fpu_fxsave( struct task_struct *tsk,
                                   struct user_i387_struct *fpu )
{
        unsigned short *to;
        unsigned short *from;
        int i;

        memcpy( fpu, &tsk->thread.i387.fxsave, 7 * sizeof(long) );

        to = (unsigned short *)&fpu->st_space[0];
        from = (unsigned short *)&tsk->thread.i387.fxsave.st_space[0];
        for ( i = 0 ; i < 8 ; i++, to += 5, from += 8 ) {
                memcpy( to, from, 5 * sizeof(unsigned short) );
        }
}

int dump_fpu( struct pt_regs *regs, struct user_i387_struct *fpu )
{
        int fpvalid;
        struct task_struct *tsk = current;

        fpvalid = tsk->used_math;
        if ( fpvalid ) {
                unlazy_fpu( tsk );
                if ( cpu_has_fxsr ) {
                        copy_fpu_fxsave( tsk, fpu );
                } else {
                        copy_fpu_fsave( tsk, fpu );
                }
        }

        return fpvalid;
}

int dump_extended_fpu( struct pt_regs *regs, struct user_fxsr_struct *fpu )
{
        int fpvalid;
        struct task_struct *tsk = current;

        fpvalid = tsk->used_math && cpu_has_fxsr;
        if ( fpvalid ) {
                unlazy_fpu( tsk );
                memcpy( fpu, &tsk->thread.i387.fxsave,
                        sizeof(struct user_fxsr_struct) );
        }

        return fpvalid;
}