// SPDX-License-Identifier: GPL-2.0
/*
 * Save/restore floating point context for signal handlers.
 *
 * Copyright (C) 1999, 2000  Kaz Kojima & Niibe Yutaka
 *
 * FIXME! These routines can be optimized in big endian case.
 */
#include <linux/sched/signal.h>
#include <linux/signal.h>
#include <asm/processor.h>
#include <asm/io.h>
#include <asm/fpu.h>
#include <asm/traps.h>

/* The PR (precision) bit in the FP Status Register must be clear when
 * an frchg instruction is executed, otherwise the instruction is undefined.
 * Executing frchg with PR set causes a trap on some SH4 implementations.
 */

#define FPSCR_RCHG 0x00000000


/*
 * Save FPU registers onto task structure.
 */
void save_fpu(struct task_struct *tsk)
{
        unsigned long dummy;

        enable_fpu();
        asm volatile("sts.l     fpul, @-%0\n\t"
                     "sts.l     fpscr, @-%0\n\t"
                     "fmov.s    fr15, @-%0\n\t"
                     "fmov.s    fr14, @-%0\n\t"
                     "fmov.s    fr13, @-%0\n\t"
                     "fmov.s    fr12, @-%0\n\t"
                     "fmov.s    fr11, @-%0\n\t"
                     "fmov.s    fr10, @-%0\n\t"
                     "fmov.s    fr9, @-%0\n\t"
                     "fmov.s    fr8, @-%0\n\t"
                     "fmov.s    fr7, @-%0\n\t"
                     "fmov.s    fr6, @-%0\n\t"
                     "fmov.s    fr5, @-%0\n\t"
                     "fmov.s    fr4, @-%0\n\t"
                     "fmov.s    fr3, @-%0\n\t"
                     "fmov.s    fr2, @-%0\n\t"
                     "fmov.s    fr1, @-%0\n\t"
                     "fmov.s    fr0, @-%0\n\t"
                     "lds       %3, fpscr\n\t"
                     : "=r" (dummy)
                     : "0" ((char *)(&tsk->thread.xstate->hardfpu.status)),
                       "r" (FPSCR_RCHG),
                       "r" (FPSCR_INIT)
                     : "memory");

        disable_fpu();
}

void restore_fpu(struct task_struct *tsk)
{
        unsigned long dummy;

        enable_fpu();
        asm volatile("fmov.s    @%0+, fr0\n\t"
                     "fmov.s    @%0+, fr1\n\t"
                     "fmov.s    @%0+, fr2\n\t"
                     "fmov.s    @%0+, fr3\n\t"
                     "fmov.s    @%0+, fr4\n\t"
                     "fmov.s    @%0+, fr5\n\t"
                     "fmov.s    @%0+, fr6\n\t"
                     "fmov.s    @%0+, fr7\n\t"
                     "fmov.s    @%0+, fr8\n\t"
                     "fmov.s    @%0+, fr9\n\t"
                     "fmov.s    @%0+, fr10\n\t"
                     "fmov.s    @%0+, fr11\n\t"
                     "fmov.s    @%0+, fr12\n\t"
                     "fmov.s    @%0+, fr13\n\t"
                     "fmov.s    @%0+, fr14\n\t"
                     "fmov.s    @%0+, fr15\n\t"
                     "lds.l     @%0+, fpscr\n\t"
                     "lds.l     @%0+, fpul\n\t"
                     : "=r" (dummy)
                     : "0" (tsk->thread.xstate), "r" (FPSCR_RCHG)
                     : "memory");
        disable_fpu();
}

/*
 *      Emulate arithmetic ops on denormalized number for some FPU insns.
 */

/* denormalized float * float */
static int denormal_mulf(int hx, int hy)
{
        unsigned int ix, iy;
        unsigned long long m, n;
        int exp, w;

        ix = hx & 0x7fffffff;
        iy = hy & 0x7fffffff;
        if (iy < 0x00800000 || ix == 0)
                return ((hx ^ hy) & 0x80000000);

        exp = (iy & 0x7f800000) >> 23;
        ix &= 0x007fffff;
        iy = (iy & 0x007fffff) | 0x00800000;
        m = (unsigned long long)ix * iy;
        n = m;
        w = -1;
        while (n) { n >>= 1; w++; }

        /* FIXME: use guard bits */
        exp += w - 126 - 46;
        if (exp > 0)
                ix = ((int) (m >> (w - 23)) & 0x007fffff) | (exp << 23);
        else if (exp + 22 >= 0)
                ix = (int) (m >> (w - 22 - exp)) & 0x007fffff;
        else
                ix = 0;

        ix |= (hx ^ hy) & 0x80000000;
        return ix;
}

/* denormalized double * double */
static void mult64(unsigned long long x, unsigned long long y,
                unsigned long long *highp, unsigned long long *lowp)
{
        unsigned long long sub0, sub1, sub2, sub3;
        unsigned long long high, low;

        sub0 = (x >> 32) * (unsigned long) (y >> 32);
        sub1 = (x & 0xffffffffLL) * (unsigned long) (y >> 32);
        sub2 = (x >> 32) * (unsigned long) (y & 0xffffffffLL);
        sub3 = (x & 0xffffffffLL) * (unsigned long) (y & 0xffffffffLL);
        low = sub3;
        high = 0LL;
        sub3 += (sub1 << 32);
        if (low > sub3)
                high++;
        low = sub3;
        sub3 += (sub2 << 32);
        if (low > sub3)
                high++;
        low = sub3;
        high += (sub1 >> 32) + (sub2 >> 32);
        high += sub0;
        *lowp = low;
        *highp = high;
}

static inline long long rshift64(unsigned long long mh,
                unsigned long long ml, int n)
{
        if (n >= 64)
                return mh >> (n - 64);
        return (mh << (64 - n)) | (ml >> n);
}

static long long denormal_muld(long long hx, long long hy)
{
        unsigned long long ix, iy;
        unsigned long long mh, ml, nh, nl;
        int exp, w;

        ix = hx & 0x7fffffffffffffffLL;
        iy = hy & 0x7fffffffffffffffLL;
        if (iy < 0x0010000000000000LL || ix == 0)
                return ((hx ^ hy) & 0x8000000000000000LL);

        exp = (iy & 0x7ff0000000000000LL) >> 52;
        ix &= 0x000fffffffffffffLL;
        iy = (iy & 0x000fffffffffffffLL) | 0x0010000000000000LL;
        mult64(ix, iy, &mh, &ml);
        nh = mh;
        nl = ml;
        w = -1;
        if (nh) {
                while (nh) { nh >>= 1; w++;}
                w += 64;
        } else
                while (nl) { nl >>= 1; w++;}

        /* FIXME: use guard bits */
        exp += w - 1022 - 52 * 2;
        if (exp > 0)
                ix = (rshift64(mh, ml, w - 52) & 0x000fffffffffffffLL)
                        | ((long long)exp << 52);
        else if (exp + 51 >= 0)
                ix = rshift64(mh, ml, w - 51 - exp) & 0x000fffffffffffffLL;
        else
                ix = 0;

        ix |= (hx ^ hy) & 0x8000000000000000LL;
        return ix;
}

/* ix - iy where iy: denormal and ix, iy >= 0 */
static int denormal_subf1(unsigned int ix, unsigned int iy)
{
        int frac;
        int exp;

        if (ix < 0x00800000)
                return ix - iy;

        exp = (ix & 0x7f800000) >> 23;
        if (exp - 1 > 31)
                return ix;
        iy >>= exp - 1;
        if (iy == 0)
                return ix;

        frac = (ix & 0x007fffff) | 0x00800000;
        frac -= iy;
        while (frac < 0x00800000) {
                if (--exp == 0)
                        return frac;
                frac <<= 1;
        }

        return (exp << 23) | (frac & 0x007fffff);
}

/* ix + iy where iy: denormal and ix, iy >= 0 */
static int denormal_addf1(unsigned int ix, unsigned int iy)
{
        int frac;
        int exp;

        if (ix < 0x00800000)
                return ix + iy;

        exp = (ix & 0x7f800000) >> 23;
        if (exp - 1 > 31)
                return ix;
        iy >>= exp - 1;
        if (iy == 0)
          return ix;

        frac = (ix & 0x007fffff) | 0x00800000;
        frac += iy;
        if (frac >= 0x01000000) {
                frac >>= 1;
                ++exp;
        }

        return (exp << 23) | (frac & 0x007fffff);
}

static int denormal_addf(int hx, int hy)
{
        unsigned int ix, iy;
        int sign;

        if ((hx ^ hy) & 0x80000000) {
                sign = hx & 0x80000000;
                ix = hx & 0x7fffffff;
                iy = hy & 0x7fffffff;
                if (iy < 0x00800000) {
                        ix = denormal_subf1(ix, iy);
                        if ((int) ix < 0) {
                                ix = -ix;
                                sign ^= 0x80000000;
                        }
                } else {
                        ix = denormal_subf1(iy, ix);
                        sign ^= 0x80000000;
                }
        } else {
                sign = hx & 0x80000000;
                ix = hx & 0x7fffffff;
                iy = hy & 0x7fffffff;
                if (iy < 0x00800000)
                        ix = denormal_addf1(ix, iy);
                else
                        ix = denormal_addf1(iy, ix);
        }

        return sign | ix;
}

/* ix - iy where iy: denormal and ix, iy >= 0 */
static long long denormal_subd1(unsigned long long ix, unsigned long long iy)
{
        long long frac;
        int exp;

        if (ix < 0x0010000000000000LL)
                return ix - iy;

        exp = (ix & 0x7ff0000000000000LL) >> 52;
        if (exp - 1 > 63)
                return ix;
        iy >>= exp - 1;
        if (iy == 0)
                return ix;

        frac = (ix & 0x000fffffffffffffLL) | 0x0010000000000000LL;
        frac -= iy;
        while (frac < 0x0010000000000000LL) {
                if (--exp == 0)
                        return frac;
                frac <<= 1;
        }

        return ((long long)exp << 52) | (frac & 0x000fffffffffffffLL);
}

/* ix + iy where iy: denormal and ix, iy >= 0 */
static long long denormal_addd1(unsigned long long ix, unsigned long long iy)
{
        long long frac;
        long long exp;

        if (ix < 0x0010000000000000LL)
                return ix + iy;

        exp = (ix & 0x7ff0000000000000LL) >> 52;
        if (exp - 1 > 63)
                return ix;
        iy >>= exp - 1;
        if (iy == 0)
          return ix;

        frac = (ix & 0x000fffffffffffffLL) | 0x0010000000000000LL;
        frac += iy;
        if (frac >= 0x0020000000000000LL) {
                frac >>= 1;
                ++exp;
        }

        return (exp << 52) | (frac & 0x000fffffffffffffLL);
}

static long long denormal_addd(long long hx, long long hy)
{
        unsigned long long ix, iy;
        long long sign;

        if ((hx ^ hy) & 0x8000000000000000LL) {
                sign = hx & 0x8000000000000000LL;
                ix = hx & 0x7fffffffffffffffLL;
                iy = hy & 0x7fffffffffffffffLL;
                if (iy < 0x0010000000000000LL) {
                        ix = denormal_subd1(ix, iy);
                        if ((int) ix < 0) {
                                ix = -ix;
                                sign ^= 0x8000000000000000LL;
                        }
                } else {
                        ix = denormal_subd1(iy, ix);
                        sign ^= 0x8000000000000000LL;
                }
        } else {
                sign = hx & 0x8000000000000000LL;
                ix = hx & 0x7fffffffffffffffLL;
                iy = hy & 0x7fffffffffffffffLL;
                if (iy < 0x0010000000000000LL)
                        ix = denormal_addd1(ix, iy);
                else
                        ix = denormal_addd1(iy, ix);
        }

        return sign | ix;
}

/**
 *      denormal_to_double - Given denormalized float number,
 *                           store double float
 *
 *      @fpu: Pointer to sh_fpu_hard structure
 *      @n: Index to FP register
 */
static void
denormal_to_double (struct sh_fpu_hard_struct *fpu, int n)
{
        unsigned long du, dl;
        unsigned long x = fpu->fpul;
        int exp = 1023 - 126;

        if (x != 0 && (x & 0x7f800000) == 0) {
                du = (x & 0x80000000);
                while ((x & 0x00800000) == 0) {
                        x <<= 1;
                        exp--;
                }
                x &= 0x007fffff;
                du |= (exp << 20) | (x >> 3);
                dl = x << 29;

                fpu->fp_regs[n] = du;
                fpu->fp_regs[n+1] = dl;
        }
}

/**
 *      ieee_fpe_handler - Handle denormalized number exception
 *
 *      @regs: Pointer to register structure
 *
 *      Returns 1 when it's handled (should not cause exception).
 */
static int
ieee_fpe_handler (struct pt_regs *regs)
{
        unsigned short insn = *(unsigned short *) regs->pc;
        unsigned short finsn;
        unsigned long nextpc;
        int nib[4] = {
                (insn >> 12) & 0xf,
                (insn >> 8) & 0xf,
                (insn >> 4) & 0xf,
                insn & 0xf};

        if (nib[0] == 0xb ||
            (nib[0] == 0x4 && nib[2] == 0x0 && nib[3] == 0xb)) /* bsr & jsr */
                regs->pr = regs->pc + 4;
        if (nib[0] == 0xa || nib[0] == 0xb) { /* bra & bsr */
                nextpc = regs->pc + 4 + ((short) ((insn & 0xfff) << 4) >> 3);
                finsn = *(unsigned short *) (regs->pc + 2);
        } else if (nib[0] == 0x8 && nib[1] == 0xd) { /* bt/s */
                if (regs->sr & 1)
                        nextpc = regs->pc + 4 + ((char) (insn & 0xff) << 1);
                else
                        nextpc = regs->pc + 4;
                finsn = *(unsigned short *) (regs->pc + 2);
        } else if (nib[0] == 0x8 && nib[1] == 0xf) { /* bf/s */
                if (regs->sr & 1)
                        nextpc = regs->pc + 4;
                else
                        nextpc = regs->pc + 4 + ((char) (insn & 0xff) << 1);
                finsn = *(unsigned short *) (regs->pc + 2);
        } else if (nib[0] == 0x4 && nib[3] == 0xb &&
                 (nib[2] == 0x0 || nib[2] == 0x2)) { /* jmp & jsr */
                nextpc = regs->regs[nib[1]];
                finsn = *(unsigned short *) (regs->pc + 2);
        } else if (nib[0] == 0x0 && nib[3] == 0x3 &&
                 (nib[2] == 0x0 || nib[2] == 0x2)) { /* braf & bsrf */
                nextpc = regs->pc + 4 + regs->regs[nib[1]];
                finsn = *(unsigned short *) (regs->pc + 2);
        } else if (insn == 0x000b) { /* rts */
                nextpc = regs->pr;
                finsn = *(unsigned short *) (regs->pc + 2);
        } else {
                nextpc = regs->pc + 2;
                finsn = insn;
        }

#define FPSCR_FPU_ERROR (1 << 17)

        if ((finsn & 0xf1ff) == 0xf0ad) { /* fcnvsd */
                struct task_struct *tsk = current;

                if ((tsk->thread.xstate->hardfpu.fpscr & FPSCR_FPU_ERROR)) {
                        /* FPU error */
                        denormal_to_double (&tsk->thread.xstate->hardfpu,
                                            (finsn >> 8) & 0xf);
                } else
                        return 0;

                regs->pc = nextpc;
                return 1;
        } else if ((finsn & 0xf00f) == 0xf002) { /* fmul */
                struct task_struct *tsk = current;
                int fpscr;
                int n, m, prec;
                unsigned int hx, hy;

                n = (finsn >> 8) & 0xf;
                m = (finsn >> 4) & 0xf;
                hx = tsk->thread.xstate->hardfpu.fp_regs[n];
                hy = tsk->thread.xstate->hardfpu.fp_regs[m];
                fpscr = tsk->thread.xstate->hardfpu.fpscr;
                prec = fpscr & (1 << 19);

                if ((fpscr & FPSCR_FPU_ERROR)
                     && (prec && ((hx & 0x7fffffff) < 0x00100000
                                   || (hy & 0x7fffffff) < 0x00100000))) {
                        long long llx, lly;

                        /* FPU error because of denormal */
                        llx = ((long long) hx << 32)
                               | tsk->thread.xstate->hardfpu.fp_regs[n+1];
                        lly = ((long long) hy << 32)
                               | tsk->thread.xstate->hardfpu.fp_regs[m+1];
                        if ((hx & 0x7fffffff) >= 0x00100000)
                                llx = denormal_muld(lly, llx);
                        else
                                llx = denormal_muld(llx, lly);
                        tsk->thread.xstate->hardfpu.fp_regs[n] = llx >> 32;
                        tsk->thread.xstate->hardfpu.fp_regs[n+1] = llx & 0xffffffff;
                } else if ((fpscr & FPSCR_FPU_ERROR)
                     && (!prec && ((hx & 0x7fffffff) < 0x00800000
                                   || (hy & 0x7fffffff) < 0x00800000))) {
                        /* FPU error because of denormal */
                        if ((hx & 0x7fffffff) >= 0x00800000)
                                hx = denormal_mulf(hy, hx);
                        else
                                hx = denormal_mulf(hx, hy);
                        tsk->thread.xstate->hardfpu.fp_regs[n] = hx;
                } else
                        return 0;

                regs->pc = nextpc;
                return 1;
        } else if ((finsn & 0xf00e) == 0xf000) { /* fadd, fsub */
                struct task_struct *tsk = current;
                int fpscr;
                int n, m, prec;
                unsigned int hx, hy;

                n = (finsn >> 8) & 0xf;
                m = (finsn >> 4) & 0xf;
                hx = tsk->thread.xstate->hardfpu.fp_regs[n];
                hy = tsk->thread.xstate->hardfpu.fp_regs[m];
                fpscr = tsk->thread.xstate->hardfpu.fpscr;
                prec = fpscr & (1 << 19);

                if ((fpscr & FPSCR_FPU_ERROR)
                     && (prec && ((hx & 0x7fffffff) < 0x00100000
                                   || (hy & 0x7fffffff) < 0x00100000))) {
                        long long llx, lly;

                        /* FPU error because of denormal */
                        llx = ((long long) hx << 32)
                               | tsk->thread.xstate->hardfpu.fp_regs[n+1];
                        lly = ((long long) hy << 32)
                               | tsk->thread.xstate->hardfpu.fp_regs[m+1];
                        if ((finsn & 0xf00f) == 0xf000)
                                llx = denormal_addd(llx, lly);
                        else
                                llx = denormal_addd(llx, lly ^ (1LL << 63));
                        tsk->thread.xstate->hardfpu.fp_regs[n] = llx >> 32;
                        tsk->thread.xstate->hardfpu.fp_regs[n+1] = llx & 0xffffffff;
                } else if ((fpscr & FPSCR_FPU_ERROR)
                     && (!prec && ((hx & 0x7fffffff) < 0x00800000
                                   || (hy & 0x7fffffff) < 0x00800000))) {
                        /* FPU error because of denormal */
                        if ((finsn & 0xf00f) == 0xf000)
                                hx = denormal_addf(hx, hy);
                        else
                                hx = denormal_addf(hx, hy ^ 0x80000000);
                        tsk->thread.xstate->hardfpu.fp_regs[n] = hx;
                } else
                        return 0;

                regs->pc = nextpc;
                return 1;
        }

        return 0;
}

BUILD_TRAP_HANDLER(fpu_error)
{
        struct task_struct *tsk = current;
        TRAP_HANDLER_DECL;

        __unlazy_fpu(tsk, regs);
        if (ieee_fpe_handler(regs)) {
                tsk->thread.xstate->hardfpu.fpscr &=
                        ~(FPSCR_CAUSE_MASK | FPSCR_FLAG_MASK);
                grab_fpu(regs);
                restore_fpu(tsk);
                task_thread_info(tsk)->status |= TS_USEDFPU;
                return;
        }

        force_sig(SIGFPE);
}