fpu.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Save/restore floating point context for signal handlers.
 *
 * Copyright (C) 1999, 2000  Kaz Kojima & Niibe Yutaka
 * Copyright (C) 2006  ST Microelectronics Ltd. (denorm support)
 *
 * FIXME! These routines have not been tested for big endian case.
 */
#include <linux/sched/signal.h>
#include <linux/io.h>
#include <cpu/fpu.h>
#include <asm/processor.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
extern unsigned long long float64_div(unsigned long long a,
				      unsigned long long b);
extern unsigned long int float32_div(unsigned long int a, unsigned long int b);
extern unsigned long long float64_mul(unsigned long long a,
				      unsigned long long b);
extern unsigned long int float32_mul(unsigned long int a, unsigned long int b);
extern unsigned long long float64_add(unsigned long long a,
				      unsigned long long b);
extern unsigned long int float32_add(unsigned long int a, unsigned long int b);
extern unsigned long long float64_sub(unsigned long long a,
				      unsigned long long b);
extern unsigned long int float32_sub(unsigned long int a, unsigned long int b);
extern unsigned long int float64_to_float32(unsigned long long a);
static unsigned int fpu_exception_flags;

/*
 * 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"
		      "lds	%2, fpscr\n\t"
		      "frchg\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"
		      "frchg\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 ("lds	%2, fpscr\n\t"
		      "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"
		      "frchg\n\t"
		      "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"
		      "frchg\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();
}

/**
 *      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))
		regs->pr = regs->pc + 4;  /* bsr & jsr */

	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 + instruction_size(insn);
		finsn = insn;
	}

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

		if ((tsk->thread.xstate->hardfpu.fpscr & FPSCR_CAUSE_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 & FPSCR_DBL_PRECISION;

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

			/* FPU error because of denormal (doubles) */
			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];
			llx = float64_mul(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_CAUSE_ERROR)
			   && (!prec && ((hx & 0x7fffffff) < 0x00800000
					 || (hy & 0x7fffffff) < 0x00800000))) {
			/* FPU error because of denormal (floats) */
			hx = float32_mul(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 & FPSCR_DBL_PRECISION;

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

			/* FPU error because of denormal (doubles) */
			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 = float64_add(llx, lly);
			else
				llx = float64_sub(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_CAUSE_ERROR)
			   && (!prec && ((hx & 0x7fffffff) < 0x00800000
					 || (hy & 0x7fffffff) < 0x00800000))) {
			/* FPU error because of denormal (floats) */
			if ((finsn & 0xf00f) == 0xf000)
				hx = float32_add(hx, hy);
			else
				hx = float32_sub(hx, hy);
			tsk->thread.xstate->hardfpu.fp_regs[n] = hx;
		} else
			return 0;

		regs->pc = nextpc;
		return 1;
	} else if ((finsn & 0xf003) == 0xf003) {
		/* fdiv */
		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 & FPSCR_DBL_PRECISION;

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

			/* FPU error because of denormal (doubles) */
			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];

			llx = float64_div(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_CAUSE_ERROR)
			   && (!prec && ((hx & 0x7fffffff) < 0x00800000
					 || (hy & 0x7fffffff) < 0x00800000))) {
			/* FPU error because of denormal (floats) */
			hx = float32_div(hx, hy);
			tsk->thread.xstate->hardfpu.fp_regs[n] = hx;
		} else
			return 0;

		regs->pc = nextpc;
		return 1;
	} else if ((finsn & 0xf0bd) == 0xf0bd) {
		/* fcnvds - double to single precision convert */
		struct task_struct *tsk = current;
		int m;
		unsigned int hx;

		m = (finsn >> 8) & 0x7;
		hx = tsk->thread.xstate->hardfpu.fp_regs[m];

		if ((tsk->thread.xstate->hardfpu.fpscr & FPSCR_CAUSE_ERROR)
			&& ((hx & 0x7fffffff) < 0x00100000)) {
			/* subnormal double to float conversion */
			long long llx;

			llx = ((long long)tsk->thread.xstate->hardfpu.fp_regs[m] << 32)
			    | tsk->thread.xstate->hardfpu.fp_regs[m + 1];

			tsk->thread.xstate->hardfpu.fpul = float64_to_float32(llx);
		} else
			return 0;

		regs->pc = nextpc;
		return 1;
	}

	return 0;
}

void float_raise(unsigned int flags)
{
	fpu_exception_flags |= flags;
}

int float_rounding_mode(void)
{
	struct task_struct *tsk = current;
	int roundingMode = FPSCR_ROUNDING_MODE(tsk->thread.xstate->hardfpu.fpscr);
	return roundingMode;
}

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

	__unlazy_fpu(tsk, regs);
	fpu_exception_flags = 0;
	if (ieee_fpe_handler(regs)) {
		tsk->thread.xstate->hardfpu.fpscr &=
		    ~(FPSCR_CAUSE_MASK | FPSCR_FLAG_MASK);
		tsk->thread.xstate->hardfpu.fpscr |= fpu_exception_flags;
		/* Set the FPSCR flag as well as cause bits - simply
		 * replicate the cause */
		tsk->thread.xstate->hardfpu.fpscr |= (fpu_exception_flags >> 10);
		grab_fpu(regs);
		restore_fpu(tsk);
		task_thread_info(tsk)->status |= TS_USEDFPU;
		if ((((tsk->thread.xstate->hardfpu.fpscr & FPSCR_ENABLE_MASK) >> 7) &
		     (fpu_exception_flags >> 2)) == 0) {
			return;
		}
	}

	force_sig(SIGFPE);
}