// SPDX-License-Identifier: GPL-2.0
/*
* arch/sparc/math-emu/math.c
*
* Copyright (C) 1998 Peter Maydell (pmaydell@chiark.greenend.org.uk)
* Copyright (C) 1997, 1999 Jakub Jelinek (jj@ultra.linux.cz)
* Copyright (C) 1999 David S. Miller (davem@redhat.com)
*
* This is a good place to start if you're trying to understand the
* emulation code, because it's pretty simple. What we do is
* essentially analyse the instruction to work out what the operation
* is and which registers are involved. We then execute the appropriate
* FXXXX function. [The floating point queue introduces a minor wrinkle;
* see below...]
* The fxxxxx.c files each emulate a single insn. They look relatively
* simple because the complexity is hidden away in an unholy tangle
* of preprocessor macros.
*
* The first layer of macros is single.h, double.h, quad.h. Generally
* these files define macros for working with floating point numbers
* of the three IEEE formats. FP_ADD_D(R,A,B) is for adding doubles,
* for instance. These macros are usually defined as calls to more
* generic macros (in this case _FP_ADD(D,2,R,X,Y) where the number
* of machine words required to store the given IEEE format is passed
* as a parameter. [double.h and co check the number of bits in a word
* and define FP_ADD_D & co appropriately].
* The generic macros are defined in op-common.h. This is where all
* the grotty stuff like handling NaNs is coded. To handle the possible
* word sizes macros in op-common.h use macros like _FP_FRAC_SLL_##wc()
* where wc is the 'number of machine words' parameter (here 2).
* These are defined in the third layer of macros: op-1.h, op-2.h
* and op-4.h. These handle operations on floating point numbers composed
* of 1,2 and 4 machine words respectively. [For example, on sparc64
* doubles are one machine word so macros in double.h eventually use
* constructs in op-1.h, but on sparc32 they use op-2.h definitions.]
* soft-fp.h is on the same level as op-common.h, and defines some
* macros which are independent of both word size and FP format.
* Finally, sfp-machine.h is the machine dependent part of the
* code: it defines the word size and what type a word is. It also
* defines how _FP_MUL_MEAT_t() maps to _FP_MUL_MEAT_n_* : op-n.h
* provide several possible flavours of multiply algorithm, most
* of which require that you supply some form of asm or C primitive to
* do the actual multiply. (such asm primitives should be defined
* in sfp-machine.h too). udivmodti4.c is the same sort of thing.
*
* There may be some errors here because I'm working from a
* SPARC architecture manual V9, and what I really want is V8...
* Also, the insns which can generate exceptions seem to be a
* greater subset of the FPops than for V9 (for example, FCMPED
* has to be emulated on V8). So I think I'm going to have
* to emulate them all just to be on the safe side...
*
* Emulation routines originate from soft-fp package, which is
* part of glibc and has appropriate copyrights in it (allegedly).
*
* NB: on sparc int == long == 4 bytes, long long == 8 bytes.
* Most bits of the kernel seem to go for long rather than int,
* so we follow that practice...
*/
/* TODO:
* fpsave() saves the FP queue but fpload() doesn't reload it.
* Therefore when we context switch or change FPU ownership
* we have to check to see if the queue had anything in it and
* emulate it if it did. This is going to be a pain.
*/
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/perf_event.h>
#include <linux/uaccess.h>
#include "sfp-util_32.h"
#include <math-emu/soft-fp.h>
#include <math-emu/single.h>
#include <math-emu/double.h>
#include <math-emu/quad.h>
#define FLOATFUNC(x) extern int x(void *,void *,void *)
/* The Vn labels indicate what version of the SPARC architecture gas thinks
* each insn is. This is from the binutils source :->
*/
/* quadword instructions */
#define FSQRTQ 0x02b /* v8 */
#define FADDQ 0x043 /* v8 */
#define FSUBQ 0x047 /* v8 */
#define FMULQ 0x04b /* v8 */
#define FDIVQ 0x04f /* v8 */
#define FDMULQ 0x06e /* v8 */
#define FQTOS 0x0c7 /* v8 */
#define FQTOD 0x0cb /* v8 */
#define FITOQ 0x0cc /* v8 */
#define FSTOQ 0x0cd /* v8 */
#define FDTOQ 0x0ce /* v8 */
#define FQTOI 0x0d3 /* v8 */
#define FCMPQ 0x053 /* v8 */
#define FCMPEQ 0x057 /* v8 */
/* single/double instructions (subnormal): should all work */
#define FSQRTS 0x029 /* v7 */
#define FSQRTD 0x02a /* v7 */
#define FADDS 0x041 /* v6 */
#define FADDD 0x042 /* v6 */
#define FSUBS 0x045 /* v6 */
#define FSUBD 0x046 /* v6 */
#define FMULS 0x049 /* v6 */
#define FMULD 0x04a /* v6 */
#define FDIVS 0x04d /* v6 */
#define FDIVD 0x04e /* v6 */
#define FSMULD 0x069 /* v6 */
#define FDTOS 0x0c6 /* v6 */
#define FSTOD 0x0c9 /* v6 */
#define FSTOI 0x0d1 /* v6 */
#define FDTOI 0x0d2 /* v6 */
#define FABSS 0x009 /* v6 */
#define FCMPS 0x051 /* v6 */
#define FCMPES 0x055 /* v6 */
#define FCMPD 0x052 /* v6 */
#define FCMPED 0x056 /* v6 */
#define FMOVS 0x001 /* v6 */
#define FNEGS 0x005 /* v6 */
#define FITOS 0x0c4 /* v6 */
#define FITOD 0x0c8 /* v6 */
#define FSR_TEM_SHIFT 23UL
#define FSR_TEM_MASK (0x1fUL << FSR_TEM_SHIFT)
#define FSR_AEXC_SHIFT 5UL
#define FSR_AEXC_MASK (0x1fUL << FSR_AEXC_SHIFT)
#define FSR_CEXC_SHIFT 0UL
#define FSR_CEXC_MASK (0x1fUL << FSR_CEXC_SHIFT)
static int do_one_mathemu(u32 insn, unsigned long *fsr, unsigned long *fregs);
/* Unlike the Sparc64 version (which has a struct fpustate), we
* pass the taskstruct corresponding to the task which currently owns the
* FPU. This is partly because we don't have the fpustate struct and
* partly because the task owning the FPU isn't always current (as is
* the case for the Sparc64 port). This is probably SMP-related...
* This function returns 1 if all queued insns were emulated successfully.
* The test for unimplemented FPop in kernel mode has been moved into
* kernel/traps.c for simplicity.
*/
int do_mathemu(struct pt_regs *regs, struct task_struct *fpt)
{
/* regs->pc isn't necessarily the PC at which the offending insn is sitting.
* The FPU maintains a queue of FPops which cause traps.
* When it hits an instruction that requires that the trapped op succeeded
* (usually because it reads a reg. that the trapped op wrote) then it
* causes this exception. We need to emulate all the insns on the queue
* and then allow the op to proceed.
* This code should also handle the case where the trap was precise,
* in which case the queue length is zero and regs->pc points at the
* single FPop to be emulated. (this case is untested, though :->)
* You'll need this case if you want to be able to emulate all FPops
* because the FPU either doesn't exist or has been software-disabled.
* [The UltraSPARC makes FP a precise trap; this isn't as stupid as it
* might sound because the Ultra does funky things with a superscalar
* architecture.]
*/
/* You wouldn't believe how often I typed 'ftp' when I meant 'fpt' :-> */
int i;
int retcode = 0; /* assume all succeed */
unsigned long insn;
perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, 0);
#ifdef DEBUG_MATHEMU
printk("In do_mathemu()... pc is %08lx\n", regs->pc);
printk("fpqdepth is %ld\n", fpt->thread.fpqdepth);
for (i = 0; i < fpt->thread.fpqdepth; i++)
printk("%d: %08lx at %08lx\n", i, fpt->thread.fpqueue[i].insn,
(unsigned long)fpt->thread.fpqueue[i].insn_addr);
#endif
if (fpt->thread.fpqdepth == 0) { /* no queue, guilty insn is at regs->pc */
#ifdef DEBUG_MATHEMU
printk("precise trap at %08lx\n", regs->pc);
#endif
if (!get_user(insn, (u32 __user *) regs->pc)) {
retcode = do_one_mathemu(insn, &fpt->thread.fsr, fpt->thread.float_regs);
if (retcode) {
/* in this case we need to fix up PC & nPC */
regs->pc = regs->npc;
regs->npc += 4;
}
}
return retcode;
}
/* Normal case: need to empty the queue... */
for (i = 0; i < fpt->thread.fpqdepth; i++) {
retcode = do_one_mathemu(fpt->thread.fpqueue[i].insn, &(fpt->thread.fsr), fpt->thread.float_regs);
if (!retcode) /* insn failed, no point doing any more */
break;
}
/* Now empty the queue and clear the queue_not_empty flag */
if (retcode)
fpt->thread.fsr &= ~(0x3000 | FSR_CEXC_MASK);
else
fpt->thread.fsr &= ~0x3000;
fpt->thread.fpqdepth = 0;
return retcode;
}
/* All routines returning an exception to raise should detect
* such exceptions _before_ rounding to be consistent with
* the behavior of the hardware in the implemented cases
* (and thus with the recommendations in the V9 architecture
* manual).
*
* We return 0 if a SIGFPE should be sent, 1 otherwise.
*/
static inline int record_exception(unsigned long *pfsr, int eflag)
{
unsigned long fsr = *pfsr;
int would_trap;
/* Determine if this exception would have generated a trap. */
would_trap = (fsr & ((long)eflag << FSR_TEM_SHIFT)) != 0UL;
/* If trapping, we only want to signal one bit. */
if (would_trap != 0) {
eflag &= ((fsr & FSR_TEM_MASK) >> FSR_TEM_SHIFT);
if ((eflag & (eflag - 1)) != 0) {
if (eflag & FP_EX_INVALID)
eflag = FP_EX_INVALID;
else if (eflag & FP_EX_OVERFLOW)
eflag = FP_EX_OVERFLOW;
else if (eflag & FP_EX_UNDERFLOW)
eflag = FP_EX_UNDERFLOW;
else if (eflag & FP_EX_DIVZERO)
eflag = FP_EX_DIVZERO;
else if (eflag & FP_EX_INEXACT)
eflag = FP_EX_INEXACT;
}
}
/* Set CEXC, here is the rule:
*
* In general all FPU ops will set one and only one
* bit in the CEXC field, this is always the case
* when the IEEE exception trap is enabled in TEM.
*/
fsr &= ~(FSR_CEXC_MASK);
fsr |= ((long)eflag << FSR_CEXC_SHIFT);
/* Set the AEXC field, rule is:
*
* If a trap would not be generated, the
* CEXC just generated is OR'd into the
* existing value of AEXC.
*/
if (would_trap == 0)
fsr |= ((long)eflag << FSR_AEXC_SHIFT);
/* If trapping, indicate fault trap type IEEE. */
if (would_trap != 0)
fsr |= (1UL << 14);
*pfsr = fsr;
return (would_trap ? 0 : 1);
}
typedef union {
u32 s;
u64 d;
u64 q[2];
} *argp;
static int do_one_mathemu(u32 insn, unsigned long *pfsr, unsigned long *fregs)
{
/* Emulate the given insn, updating fsr and fregs appropriately. */
int type = 0;
/* r is rd, b is rs2 and a is rs1. The *u arg tells
whether the argument should be packed/unpacked (0 - do not unpack/pack, 1 - unpack/pack)
non-u args tells the size of the argument (0 - no argument, 1 - single, 2 - double, 3 - quad */
#define TYPE(dummy, r, ru, b, bu, a, au) type = (au << 2) | (a << 0) | (bu << 5) | (b << 3) | (ru << 8) | (r << 6)
int freg;
argp rs1 = NULL, rs2 = NULL, rd = NULL;
FP_DECL_EX;
FP_DECL_S(SA); FP_DECL_S(SB); FP_DECL_S(SR);
FP_DECL_D(DA); FP_DECL_D(DB); FP_DECL_D(DR);
FP_DECL_Q(QA); FP_DECL_Q(QB); FP_DECL_Q(QR);
int IR;
long fsr;
#ifdef DEBUG_MATHEMU
printk("In do_mathemu(), emulating %08lx\n", insn);
#endif
if ((insn & 0xc1f80000) == 0x81a00000) /* FPOP1 */ {
switch ((insn >> 5) & 0x1ff) {
case FSQRTQ: TYPE(3,3,1,3,1,0,0); break;
case FADDQ:
case FSUBQ:
case FMULQ:
case FDIVQ: TYPE(3,3,1,3,1,3,1); break;
case FDMULQ: TYPE(3,3,1,2,1,2,1); break;
case FQTOS: TYPE(3,1,1,3,1,0,0); break;
case FQTOD: TYPE(3,2,1,3,1,0,0); break;
case FITOQ: TYPE(3,3,1,1,0,0,0); break;
case FSTOQ: TYPE(3,3,1,1,1,0,0); break;
case FDTOQ: TYPE(3,3,1,2,1,0,0); break;
case FQTOI: TYPE(3,1,0,3,1,0,0); break;
case FSQRTS: TYPE(2,1,1,1,1,0,0); break;
case FSQRTD: TYPE(2,2,1,2,1,0,0); break;
case FADDD:
case FSUBD:
case FMULD:
case FDIVD: TYPE(2,2,1,2,1,2,1); break;
case FADDS:
case FSUBS:
case FMULS:
case FDIVS: TYPE(2,1,1,1,1,1,1); break;
case FSMULD: TYPE(2,2,1,1,1,1,1); break;
case FDTOS: TYPE(2,1,1,2,1,0,0); break;
case FSTOD: TYPE(2,2,1,1,1,0,0); break;
case FSTOI: TYPE(2,1,0,1,1,0,0); break;
case FDTOI: TYPE(2,1,0,2,1,0,0); break;
case FITOS: TYPE(2,1,1,1,0,0,0); break;
case FITOD: TYPE(2,2,1,1,0,0,0); break;
case FMOVS:
case FABSS:
case FNEGS: TYPE(2,1,0,1,0,0,0); break;
}
} else if ((insn & 0xc1f80000) == 0x81a80000) /* FPOP2 */ {
switch ((insn >> 5) & 0x1ff) {
case FCMPS: TYPE(3,0,0,1,1,1,1); break;
case FCMPES: TYPE(3,0,0,1,1,1,1); break;
case FCMPD: TYPE(3,0,0,2,1,2,1); break;
case FCMPED: TYPE(3,0,0,2,1,2,1); break;
case FCMPQ: TYPE(3,0,0,3,1,3,1); break;
case FCMPEQ: TYPE(3,0,0,3,1,3,1); break;
}
}
if (!type) { /* oops, didn't recognise that FPop */
#ifdef DEBUG_MATHEMU
printk("attempt to emulate unrecognised FPop!\n");
#endif
return 0;
}
/* Decode the registers to be used */
freg = (*pfsr >> 14) & 0xf;
*pfsr &= ~0x1c000; /* clear the traptype bits */
freg = ((insn >> 14) & 0x1f);
switch (type & 0x3) { /* is rs1 single, double or quad? */
case 3:
if (freg & 3) { /* quadwords must have bits 4&5 of the */
/* encoded reg. number set to zero. */
*pfsr |= (6 << 14);
return 0; /* simulate invalid_fp_register exception */
}
fallthrough;
case 2:
if (freg & 1) { /* doublewords must have bit 5 zeroed */
*pfsr |= (6 << 14);
return 0;
}
}
rs1 = (argp)&fregs[freg];
switch (type & 0x7) {
case 7: FP_UNPACK_QP (QA, rs1); break;
case 6: FP_UNPACK_DP (DA, rs1); break;
case 5: FP_UNPACK_SP (SA, rs1); break;
}
freg = (insn & 0x1f);
switch ((type >> 3) & 0x3) { /* same again for rs2 */
case 3:
if (freg & 3) { /* quadwords must have bits 4&5 of the */
/* encoded reg. number set to zero. */
*pfsr |= (6 << 14);
return 0; /* simulate invalid_fp_register exception */
}
fallthrough;
case 2:
if (freg & 1) { /* doublewords must have bit 5 zeroed */
*pfsr |= (6 << 14);
return 0;
}
}
rs2 = (argp)&fregs[freg];
switch ((type >> 3) & 0x7) {
case 7: FP_UNPACK_QP (QB, rs2); break;
case 6: FP_UNPACK_DP (DB, rs2); break;
case 5: FP_UNPACK_SP (SB, rs2); break;
}
freg = ((insn >> 25) & 0x1f);
switch ((type >> 6) & 0x3) { /* and finally rd. This one's a bit different */
case 0: /* dest is fcc. (this must be FCMPQ or FCMPEQ) */
if (freg) { /* V8 has only one set of condition codes, so */
/* anything but 0 in the rd field is an error */
*pfsr |= (6 << 14); /* (should probably flag as invalid opcode */
return 0; /* but SIGFPE will do :-> ) */
}
break;
case 3:
if (freg & 3) { /* quadwords must have bits 4&5 of the */
/* encoded reg. number set to zero. */
*pfsr |= (6 << 14);
return 0; /* simulate invalid_fp_register exception */
}
fallthrough;
case 2:
if (freg & 1) { /* doublewords must have bit 5 zeroed */
*pfsr |= (6 << 14);
return 0;
}
fallthrough;
case 1:
rd = (void *)&fregs[freg];
break;
}
#ifdef DEBUG_MATHEMU
printk("executing insn...\n");
#endif
/* do the Right Thing */
switch ((insn >> 5) & 0x1ff) {
/* + */
case FADDS: FP_ADD_S (SR, SA, SB); break;
case FADDD: FP_ADD_D (DR, DA, DB); break;
case FADDQ: FP_ADD_Q (QR, QA, QB); break;
/* - */
case FSUBS: FP_SUB_S (SR, SA, SB); break;
case FSUBD: FP_SUB_D (DR, DA, DB); break;
case FSUBQ: FP_SUB_Q (QR, QA, QB); break;
/* * */
case FMULS: FP_MUL_S (SR, SA, SB); break;
case FSMULD: FP_CONV (D, S, 2, 1, DA, SA);
FP_CONV (D, S, 2, 1, DB, SB);
case FMULD: FP_MUL_D (DR, DA, DB); break;
case FDMULQ: FP_CONV (Q, D, 4, 2, QA, DA);
FP_CONV (Q, D, 4, 2, QB, DB);
case FMULQ: FP_MUL_Q (QR, QA, QB); break;
/* / */
case FDIVS: FP_DIV_S (SR, SA, SB); break;
case FDIVD: FP_DIV_D (DR, DA, DB); break;
case FDIVQ: FP_DIV_Q (QR, QA, QB); break;
/* sqrt */
case FSQRTS: FP_SQRT_S (SR, SB); break;
case FSQRTD: FP_SQRT_D (DR, DB); break;
case FSQRTQ: FP_SQRT_Q (QR, QB); break;
/* mov */
case FMOVS: rd->s = rs2->s; break;
case FABSS: rd->s = rs2->s & 0x7fffffff; break;
case FNEGS: rd->s = rs2->s ^ 0x80000000; break;
/* float to int */
case FSTOI: FP_TO_INT_S (IR, SB, 32, 1); break;
case FDTOI: FP_TO_INT_D (IR, DB, 32, 1); break;
case FQTOI: FP_TO_INT_Q (IR, QB, 32, 1); break;
/* int to float */
case FITOS: IR = rs2->s; FP_FROM_INT_S (SR, IR, 32, int); break;
case FITOD: IR = rs2->s; FP_FROM_INT_D (DR, IR, 32, int); break;
case FITOQ: IR = rs2->s; FP_FROM_INT_Q (QR, IR, 32, int); break;
/* float to float */
case FSTOD: FP_CONV (D, S, 2, 1, DR, SB); break;
case FSTOQ: FP_CONV (Q, S, 4, 1, QR, SB); break;
case FDTOQ: FP_CONV (Q, D, 4, 2, QR, DB); break;
case FDTOS: FP_CONV (S, D, 1, 2, SR, DB); break;
case FQTOS: FP_CONV (S, Q, 1, 4, SR, QB); break;
case FQTOD: FP_CONV (D, Q, 2, 4, DR, QB); break;
/* comparison */
case FCMPS:
case FCMPES:
FP_CMP_S(IR, SB, SA, 3);
if (IR == 3 &&
(((insn >> 5) & 0x1ff) == FCMPES ||
FP_ISSIGNAN_S(SA) ||
FP_ISSIGNAN_S(SB)))
FP_SET_EXCEPTION (FP_EX_INVALID);
break;
case FCMPD:
case FCMPED:
FP_CMP_D(IR, DB, DA, 3);
if (IR == 3 &&
(((insn >> 5) & 0x1ff) == FCMPED ||
FP_ISSIGNAN_D(DA) ||
FP_ISSIGNAN_D(DB)))
FP_SET_EXCEPTION (FP_EX_INVALID);
break;
case FCMPQ:
case FCMPEQ:
FP_CMP_Q(IR, QB, QA, 3);
if (IR == 3 &&
(((insn >> 5) & 0x1ff) == FCMPEQ ||
FP_ISSIGNAN_Q(QA) ||
FP_ISSIGNAN_Q(QB)))
FP_SET_EXCEPTION (FP_EX_INVALID);
}
if (!FP_INHIBIT_RESULTS) {
switch ((type >> 6) & 0x7) {
case 0: fsr = *pfsr;
if (IR == -1) IR = 2;
/* fcc is always fcc0 */
fsr &= ~0xc00; fsr |= (IR << 10);
*pfsr = fsr;
break;
case 1: rd->s = IR; break;
case 5: FP_PACK_SP (rd, SR); break;
case 6: FP_PACK_DP (rd, DR); break;
case 7: FP_PACK_QP (rd, QR); break;
}
}
if (_fex == 0)
return 1; /* success! */
return record_exception(pfsr, _fex);
}