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math_32.c
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1 /*
2  * arch/sparc/math-emu/math.c
3  *
4  * Copyright (C) 1998 Peter Maydell ([email protected])
5  * Copyright (C) 1997, 1999 Jakub Jelinek ([email protected])
6  * Copyright (C) 1999 David S. Miller ([email protected])
7  *
8  * This is a good place to start if you're trying to understand the
9  * emulation code, because it's pretty simple. What we do is
10  * essentially analyse the instruction to work out what the operation
11  * is and which registers are involved. We then execute the appropriate
12  * FXXXX function. [The floating point queue introduces a minor wrinkle;
13  * see below...]
14  * The fxxxxx.c files each emulate a single insn. They look relatively
15  * simple because the complexity is hidden away in an unholy tangle
16  * of preprocessor macros.
17  *
18  * The first layer of macros is single.h, double.h, quad.h. Generally
19  * these files define macros for working with floating point numbers
20  * of the three IEEE formats. FP_ADD_D(R,A,B) is for adding doubles,
21  * for instance. These macros are usually defined as calls to more
22  * generic macros (in this case _FP_ADD(D,2,R,X,Y) where the number
23  * of machine words required to store the given IEEE format is passed
24  * as a parameter. [double.h and co check the number of bits in a word
25  * and define FP_ADD_D & co appropriately].
26  * The generic macros are defined in op-common.h. This is where all
27  * the grotty stuff like handling NaNs is coded. To handle the possible
28  * word sizes macros in op-common.h use macros like _FP_FRAC_SLL_##wc()
29  * where wc is the 'number of machine words' parameter (here 2).
30  * These are defined in the third layer of macros: op-1.h, op-2.h
31  * and op-4.h. These handle operations on floating point numbers composed
32  * of 1,2 and 4 machine words respectively. [For example, on sparc64
33  * doubles are one machine word so macros in double.h eventually use
34  * constructs in op-1.h, but on sparc32 they use op-2.h definitions.]
35  * soft-fp.h is on the same level as op-common.h, and defines some
36  * macros which are independent of both word size and FP format.
37  * Finally, sfp-machine.h is the machine dependent part of the
38  * code: it defines the word size and what type a word is. It also
39  * defines how _FP_MUL_MEAT_t() maps to _FP_MUL_MEAT_n_* : op-n.h
40  * provide several possible flavours of multiply algorithm, most
41  * of which require that you supply some form of asm or C primitive to
42  * do the actual multiply. (such asm primitives should be defined
43  * in sfp-machine.h too). udivmodti4.c is the same sort of thing.
44  *
45  * There may be some errors here because I'm working from a
46  * SPARC architecture manual V9, and what I really want is V8...
47  * Also, the insns which can generate exceptions seem to be a
48  * greater subset of the FPops than for V9 (for example, FCMPED
49  * has to be emulated on V8). So I think I'm going to have
50  * to emulate them all just to be on the safe side...
51  *
52  * Emulation routines originate from soft-fp package, which is
53  * part of glibc and has appropriate copyrights in it (allegedly).
54  *
55  * NB: on sparc int == long == 4 bytes, long long == 8 bytes.
56  * Most bits of the kernel seem to go for long rather than int,
57  * so we follow that practice...
58  */
59 
60 /* TODO:
61  * fpsave() saves the FP queue but fpload() doesn't reload it.
62  * Therefore when we context switch or change FPU ownership
63  * we have to check to see if the queue had anything in it and
64  * emulate it if it did. This is going to be a pain.
65  */
66 
67 #include <linux/types.h>
68 #include <linux/sched.h>
69 #include <linux/mm.h>
70 #include <linux/perf_event.h>
71 #include <asm/uaccess.h>
72 
73 #include "sfp-util_32.h"
74 #include <math-emu/soft-fp.h>
75 #include <math-emu/single.h>
76 #include <math-emu/double.h>
77 #include <math-emu/quad.h>
78 
79 #define FLOATFUNC(x) extern int x(void *,void *,void *)
80 
81 /* The Vn labels indicate what version of the SPARC architecture gas thinks
82  * each insn is. This is from the binutils source :->
83  */
84 /* quadword instructions */
85 #define FSQRTQ 0x02b /* v8 */
86 #define FADDQ 0x043 /* v8 */
87 #define FSUBQ 0x047 /* v8 */
88 #define FMULQ 0x04b /* v8 */
89 #define FDIVQ 0x04f /* v8 */
90 #define FDMULQ 0x06e /* v8 */
91 #define FQTOS 0x0c7 /* v8 */
92 #define FQTOD 0x0cb /* v8 */
93 #define FITOQ 0x0cc /* v8 */
94 #define FSTOQ 0x0cd /* v8 */
95 #define FDTOQ 0x0ce /* v8 */
96 #define FQTOI 0x0d3 /* v8 */
97 #define FCMPQ 0x053 /* v8 */
98 #define FCMPEQ 0x057 /* v8 */
99 /* single/double instructions (subnormal): should all work */
100 #define FSQRTS 0x029 /* v7 */
101 #define FSQRTD 0x02a /* v7 */
102 #define FADDS 0x041 /* v6 */
103 #define FADDD 0x042 /* v6 */
104 #define FSUBS 0x045 /* v6 */
105 #define FSUBD 0x046 /* v6 */
106 #define FMULS 0x049 /* v6 */
107 #define FMULD 0x04a /* v6 */
108 #define FDIVS 0x04d /* v6 */
109 #define FDIVD 0x04e /* v6 */
110 #define FSMULD 0x069 /* v6 */
111 #define FDTOS 0x0c6 /* v6 */
112 #define FSTOD 0x0c9 /* v6 */
113 #define FSTOI 0x0d1 /* v6 */
114 #define FDTOI 0x0d2 /* v6 */
115 #define FABSS 0x009 /* v6 */
116 #define FCMPS 0x051 /* v6 */
117 #define FCMPES 0x055 /* v6 */
118 #define FCMPD 0x052 /* v6 */
119 #define FCMPED 0x056 /* v6 */
120 #define FMOVS 0x001 /* v6 */
121 #define FNEGS 0x005 /* v6 */
122 #define FITOS 0x0c4 /* v6 */
123 #define FITOD 0x0c8 /* v6 */
124 
125 #define FSR_TEM_SHIFT 23UL
126 #define FSR_TEM_MASK (0x1fUL << FSR_TEM_SHIFT)
127 #define FSR_AEXC_SHIFT 5UL
128 #define FSR_AEXC_MASK (0x1fUL << FSR_AEXC_SHIFT)
129 #define FSR_CEXC_SHIFT 0UL
130 #define FSR_CEXC_MASK (0x1fUL << FSR_CEXC_SHIFT)
131 
132 static int do_one_mathemu(u32 insn, unsigned long *fsr, unsigned long *fregs);
133 
134 /* Unlike the Sparc64 version (which has a struct fpustate), we
135  * pass the taskstruct corresponding to the task which currently owns the
136  * FPU. This is partly because we don't have the fpustate struct and
137  * partly because the task owning the FPU isn't always current (as is
138  * the case for the Sparc64 port). This is probably SMP-related...
139  * This function returns 1 if all queued insns were emulated successfully.
140  * The test for unimplemented FPop in kernel mode has been moved into
141  * kernel/traps.c for simplicity.
142  */
143 int do_mathemu(struct pt_regs *regs, struct task_struct *fpt)
144 {
145  /* regs->pc isn't necessarily the PC at which the offending insn is sitting.
146  * The FPU maintains a queue of FPops which cause traps.
147  * When it hits an instruction that requires that the trapped op succeeded
148  * (usually because it reads a reg. that the trapped op wrote) then it
149  * causes this exception. We need to emulate all the insns on the queue
150  * and then allow the op to proceed.
151  * This code should also handle the case where the trap was precise,
152  * in which case the queue length is zero and regs->pc points at the
153  * single FPop to be emulated. (this case is untested, though :->)
154  * You'll need this case if you want to be able to emulate all FPops
155  * because the FPU either doesn't exist or has been software-disabled.
156  * [The UltraSPARC makes FP a precise trap; this isn't as stupid as it
157  * might sound because the Ultra does funky things with a superscalar
158  * architecture.]
159  */
160 
161  /* You wouldn't believe how often I typed 'ftp' when I meant 'fpt' :-> */
162 
163  int i;
164  int retcode = 0; /* assume all succeed */
165  unsigned long insn;
166 
167  perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, 0);
168 
169 #ifdef DEBUG_MATHEMU
170  printk("In do_mathemu()... pc is %08lx\n", regs->pc);
171  printk("fpqdepth is %ld\n", fpt->thread.fpqdepth);
172  for (i = 0; i < fpt->thread.fpqdepth; i++)
173  printk("%d: %08lx at %08lx\n", i, fpt->thread.fpqueue[i].insn,
174  (unsigned long)fpt->thread.fpqueue[i].insn_addr);
175 #endif
176 
177  if (fpt->thread.fpqdepth == 0) { /* no queue, guilty insn is at regs->pc */
178 #ifdef DEBUG_MATHEMU
179  printk("precise trap at %08lx\n", regs->pc);
180 #endif
181  if (!get_user(insn, (u32 __user *) regs->pc)) {
182  retcode = do_one_mathemu(insn, &fpt->thread.fsr, fpt->thread.float_regs);
183  if (retcode) {
184  /* in this case we need to fix up PC & nPC */
185  regs->pc = regs->npc;
186  regs->npc += 4;
187  }
188  }
189  return retcode;
190  }
191 
192  /* Normal case: need to empty the queue... */
193  for (i = 0; i < fpt->thread.fpqdepth; i++) {
194  retcode = do_one_mathemu(fpt->thread.fpqueue[i].insn, &(fpt->thread.fsr), fpt->thread.float_regs);
195  if (!retcode) /* insn failed, no point doing any more */
196  break;
197  }
198  /* Now empty the queue and clear the queue_not_empty flag */
199  if (retcode)
200  fpt->thread.fsr &= ~(0x3000 | FSR_CEXC_MASK);
201  else
202  fpt->thread.fsr &= ~0x3000;
203  fpt->thread.fpqdepth = 0;
204 
205  return retcode;
206 }
207 
208 /* All routines returning an exception to raise should detect
209  * such exceptions _before_ rounding to be consistent with
210  * the behavior of the hardware in the implemented cases
211  * (and thus with the recommendations in the V9 architecture
212  * manual).
213  *
214  * We return 0 if a SIGFPE should be sent, 1 otherwise.
215  */
216 static inline int record_exception(unsigned long *pfsr, int eflag)
217 {
218  unsigned long fsr = *pfsr;
219  int would_trap;
220 
221  /* Determine if this exception would have generated a trap. */
222  would_trap = (fsr & ((long)eflag << FSR_TEM_SHIFT)) != 0UL;
223 
224  /* If trapping, we only want to signal one bit. */
225  if (would_trap != 0) {
226  eflag &= ((fsr & FSR_TEM_MASK) >> FSR_TEM_SHIFT);
227  if ((eflag & (eflag - 1)) != 0) {
228  if (eflag & FP_EX_INVALID)
229  eflag = FP_EX_INVALID;
230  else if (eflag & FP_EX_OVERFLOW)
231  eflag = FP_EX_OVERFLOW;
232  else if (eflag & FP_EX_UNDERFLOW)
233  eflag = FP_EX_UNDERFLOW;
234  else if (eflag & FP_EX_DIVZERO)
235  eflag = FP_EX_DIVZERO;
236  else if (eflag & FP_EX_INEXACT)
237  eflag = FP_EX_INEXACT;
238  }
239  }
240 
241  /* Set CEXC, here is the rule:
242  *
243  * In general all FPU ops will set one and only one
244  * bit in the CEXC field, this is always the case
245  * when the IEEE exception trap is enabled in TEM.
246  */
247  fsr &= ~(FSR_CEXC_MASK);
248  fsr |= ((long)eflag << FSR_CEXC_SHIFT);
249 
250  /* Set the AEXC field, rule is:
251  *
252  * If a trap would not be generated, the
253  * CEXC just generated is OR'd into the
254  * existing value of AEXC.
255  */
256  if (would_trap == 0)
257  fsr |= ((long)eflag << FSR_AEXC_SHIFT);
258 
259  /* If trapping, indicate fault trap type IEEE. */
260  if (would_trap != 0)
261  fsr |= (1UL << 14);
262 
263  *pfsr = fsr;
264 
265  return (would_trap ? 0 : 1);
266 }
267 
268 typedef union {
271  u64 q[2];
272 } *argp;
273 
274 static int do_one_mathemu(u32 insn, unsigned long *pfsr, unsigned long *fregs)
275 {
276  /* Emulate the given insn, updating fsr and fregs appropriately. */
277  int type = 0;
278  /* r is rd, b is rs2 and a is rs1. The *u arg tells
279  whether the argument should be packed/unpacked (0 - do not unpack/pack, 1 - unpack/pack)
280  non-u args tells the size of the argument (0 - no argument, 1 - single, 2 - double, 3 - quad */
281 #define TYPE(dummy, r, ru, b, bu, a, au) type = (au << 2) | (a << 0) | (bu << 5) | (b << 3) | (ru << 8) | (r << 6)
282  int freg;
283  argp rs1 = NULL, rs2 = NULL, rd = NULL;
284  FP_DECL_EX;
287  FP_DECL_Q(QA); FP_DECL_Q(QB); FP_DECL_Q(QR);
288  int IR;
289  long fsr;
290 
291 #ifdef DEBUG_MATHEMU
292  printk("In do_mathemu(), emulating %08lx\n", insn);
293 #endif
294 
295  if ((insn & 0xc1f80000) == 0x81a00000) /* FPOP1 */ {
296  switch ((insn >> 5) & 0x1ff) {
297  case FSQRTQ: TYPE(3,3,1,3,1,0,0); break;
298  case FADDQ:
299  case FSUBQ:
300  case FMULQ:
301  case FDIVQ: TYPE(3,3,1,3,1,3,1); break;
302  case FDMULQ: TYPE(3,3,1,2,1,2,1); break;
303  case FQTOS: TYPE(3,1,1,3,1,0,0); break;
304  case FQTOD: TYPE(3,2,1,3,1,0,0); break;
305  case FITOQ: TYPE(3,3,1,1,0,0,0); break;
306  case FSTOQ: TYPE(3,3,1,1,1,0,0); break;
307  case FDTOQ: TYPE(3,3,1,2,1,0,0); break;
308  case FQTOI: TYPE(3,1,0,3,1,0,0); break;
309  case FSQRTS: TYPE(2,1,1,1,1,0,0); break;
310  case FSQRTD: TYPE(2,2,1,2,1,0,0); break;
311  case FADDD:
312  case FSUBD:
313  case FMULD:
314  case FDIVD: TYPE(2,2,1,2,1,2,1); break;
315  case FADDS:
316  case FSUBS:
317  case FMULS:
318  case FDIVS: TYPE(2,1,1,1,1,1,1); break;
319  case FSMULD: TYPE(2,2,1,1,1,1,1); break;
320  case FDTOS: TYPE(2,1,1,2,1,0,0); break;
321  case FSTOD: TYPE(2,2,1,1,1,0,0); break;
322  case FSTOI: TYPE(2,1,0,1,1,0,0); break;
323  case FDTOI: TYPE(2,1,0,2,1,0,0); break;
324  case FITOS: TYPE(2,1,1,1,0,0,0); break;
325  case FITOD: TYPE(2,2,1,1,0,0,0); break;
326  case FMOVS:
327  case FABSS:
328  case FNEGS: TYPE(2,1,0,1,0,0,0); break;
329  }
330  } else if ((insn & 0xc1f80000) == 0x81a80000) /* FPOP2 */ {
331  switch ((insn >> 5) & 0x1ff) {
332  case FCMPS: TYPE(3,0,0,1,1,1,1); break;
333  case FCMPES: TYPE(3,0,0,1,1,1,1); break;
334  case FCMPD: TYPE(3,0,0,2,1,2,1); break;
335  case FCMPED: TYPE(3,0,0,2,1,2,1); break;
336  case FCMPQ: TYPE(3,0,0,3,1,3,1); break;
337  case FCMPEQ: TYPE(3,0,0,3,1,3,1); break;
338  }
339  }
340 
341  if (!type) { /* oops, didn't recognise that FPop */
342 #ifdef DEBUG_MATHEMU
343  printk("attempt to emulate unrecognised FPop!\n");
344 #endif
345  return 0;
346  }
347 
348  /* Decode the registers to be used */
349  freg = (*pfsr >> 14) & 0xf;
350 
351  *pfsr &= ~0x1c000; /* clear the traptype bits */
352 
353  freg = ((insn >> 14) & 0x1f);
354  switch (type & 0x3) { /* is rs1 single, double or quad? */
355  case 3:
356  if (freg & 3) { /* quadwords must have bits 4&5 of the */
357  /* encoded reg. number set to zero. */
358  *pfsr |= (6 << 14);
359  return 0; /* simulate invalid_fp_register exception */
360  }
361  /* fall through */
362  case 2:
363  if (freg & 1) { /* doublewords must have bit 5 zeroed */
364  *pfsr |= (6 << 14);
365  return 0;
366  }
367  }
368  rs1 = (argp)&fregs[freg];
369  switch (type & 0x7) {
370  case 7: FP_UNPACK_QP (QA, rs1); break;
371  case 6: FP_UNPACK_DP (DA, rs1); break;
372  case 5: FP_UNPACK_SP (SA, rs1); break;
373  }
374  freg = (insn & 0x1f);
375  switch ((type >> 3) & 0x3) { /* same again for rs2 */
376  case 3:
377  if (freg & 3) { /* quadwords must have bits 4&5 of the */
378  /* encoded reg. number set to zero. */
379  *pfsr |= (6 << 14);
380  return 0; /* simulate invalid_fp_register exception */
381  }
382  /* fall through */
383  case 2:
384  if (freg & 1) { /* doublewords must have bit 5 zeroed */
385  *pfsr |= (6 << 14);
386  return 0;
387  }
388  }
389  rs2 = (argp)&fregs[freg];
390  switch ((type >> 3) & 0x7) {
391  case 7: FP_UNPACK_QP (QB, rs2); break;
392  case 6: FP_UNPACK_DP (DB, rs2); break;
393  case 5: FP_UNPACK_SP (SB, rs2); break;
394  }
395  freg = ((insn >> 25) & 0x1f);
396  switch ((type >> 6) & 0x3) { /* and finally rd. This one's a bit different */
397  case 0: /* dest is fcc. (this must be FCMPQ or FCMPEQ) */
398  if (freg) { /* V8 has only one set of condition codes, so */
399  /* anything but 0 in the rd field is an error */
400  *pfsr |= (6 << 14); /* (should probably flag as invalid opcode */
401  return 0; /* but SIGFPE will do :-> ) */
402  }
403  break;
404  case 3:
405  if (freg & 3) { /* quadwords must have bits 4&5 of the */
406  /* encoded reg. number set to zero. */
407  *pfsr |= (6 << 14);
408  return 0; /* simulate invalid_fp_register exception */
409  }
410  /* fall through */
411  case 2:
412  if (freg & 1) { /* doublewords must have bit 5 zeroed */
413  *pfsr |= (6 << 14);
414  return 0;
415  }
416  /* fall through */
417  case 1:
418  rd = (void *)&fregs[freg];
419  break;
420  }
421 #ifdef DEBUG_MATHEMU
422  printk("executing insn...\n");
423 #endif
424  /* do the Right Thing */
425  switch ((insn >> 5) & 0x1ff) {
426  /* + */
427  case FADDS: FP_ADD_S (SR, SA, SB); break;
428  case FADDD: FP_ADD_D (DR, DA, DB); break;
429  case FADDQ: FP_ADD_Q (QR, QA, QB); break;
430  /* - */
431  case FSUBS: FP_SUB_S (SR, SA, SB); break;
432  case FSUBD: FP_SUB_D (DR, DA, DB); break;
433  case FSUBQ: FP_SUB_Q (QR, QA, QB); break;
434  /* * */
435  case FMULS: FP_MUL_S (SR, SA, SB); break;
436  case FSMULD: FP_CONV (D, S, 2, 1, DA, SA);
437  FP_CONV (D, S, 2, 1, DB, SB);
438  case FMULD: FP_MUL_D (DR, DA, DB); break;
439  case FDMULQ: FP_CONV (Q, D, 4, 2, QA, DA);
440  FP_CONV (Q, D, 4, 2, QB, DB);
441  case FMULQ: FP_MUL_Q (QR, QA, QB); break;
442  /* / */
443  case FDIVS: FP_DIV_S (SR, SA, SB); break;
444  case FDIVD: FP_DIV_D (DR, DA, DB); break;
445  case FDIVQ: FP_DIV_Q (QR, QA, QB); break;
446  /* sqrt */
447  case FSQRTS: FP_SQRT_S (SR, SB); break;
448  case FSQRTD: FP_SQRT_D (DR, DB); break;
449  case FSQRTQ: FP_SQRT_Q (QR, QB); break;
450  /* mov */
451  case FMOVS: rd->s = rs2->s; break;
452  case FABSS: rd->s = rs2->s & 0x7fffffff; break;
453  case FNEGS: rd->s = rs2->s ^ 0x80000000; break;
454  /* float to int */
455  case FSTOI: FP_TO_INT_S (IR, SB, 32, 1); break;
456  case FDTOI: FP_TO_INT_D (IR, DB, 32, 1); break;
457  case FQTOI: FP_TO_INT_Q (IR, QB, 32, 1); break;
458  /* int to float */
459  case FITOS: IR = rs2->s; FP_FROM_INT_S (SR, IR, 32, int); break;
460  case FITOD: IR = rs2->s; FP_FROM_INT_D (DR, IR, 32, int); break;
461  case FITOQ: IR = rs2->s; FP_FROM_INT_Q (QR, IR, 32, int); break;
462  /* float to float */
463  case FSTOD: FP_CONV (D, S, 2, 1, DR, SB); break;
464  case FSTOQ: FP_CONV (Q, S, 4, 1, QR, SB); break;
465  case FDTOQ: FP_CONV (Q, D, 4, 2, QR, DB); break;
466  case FDTOS: FP_CONV (S, D, 1, 2, SR, DB); break;
467  case FQTOS: FP_CONV (S, Q, 1, 4, SR, QB); break;
468  case FQTOD: FP_CONV (D, Q, 2, 4, DR, QB); break;
469  /* comparison */
470  case FCMPS:
471  case FCMPES:
472  FP_CMP_S(IR, SB, SA, 3);
473  if (IR == 3 &&
474  (((insn >> 5) & 0x1ff) == FCMPES ||
475  FP_ISSIGNAN_S(SA) ||
476  FP_ISSIGNAN_S(SB)))
477  FP_SET_EXCEPTION (FP_EX_INVALID);
478  break;
479  case FCMPD:
480  case FCMPED:
481  FP_CMP_D(IR, DB, DA, 3);
482  if (IR == 3 &&
483  (((insn >> 5) & 0x1ff) == FCMPED ||
484  FP_ISSIGNAN_D(DA) ||
485  FP_ISSIGNAN_D(DB)))
486  FP_SET_EXCEPTION (FP_EX_INVALID);
487  break;
488  case FCMPQ:
489  case FCMPEQ:
490  FP_CMP_Q(IR, QB, QA, 3);
491  if (IR == 3 &&
492  (((insn >> 5) & 0x1ff) == FCMPEQ ||
493  FP_ISSIGNAN_Q(QA) ||
494  FP_ISSIGNAN_Q(QB)))
495  FP_SET_EXCEPTION (FP_EX_INVALID);
496  }
497  if (!FP_INHIBIT_RESULTS) {
498  switch ((type >> 6) & 0x7) {
499  case 0: fsr = *pfsr;
500  if (IR == -1) IR = 2;
501  /* fcc is always fcc0 */
502  fsr &= ~0xc00; fsr |= (IR << 10); break;
503  *pfsr = fsr;
504  break;
505  case 1: rd->s = IR; break;
506  case 5: FP_PACK_SP (rd, SR); break;
507  case 6: FP_PACK_DP (rd, DR); break;
508  case 7: FP_PACK_QP (rd, QR); break;
509  }
510  }
511  if (_fex == 0)
512  return 1; /* success! */
513  return record_exception(pfsr, _fex);
514 }