1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * arch/sparc/math-emu/math.c 4 * 5 * Copyright (C) 1998 Peter Maydell (pmaydell@chiark.greenend.org.uk) 6 * Copyright (C) 1997, 1999 Jakub Jelinek (jj@ultra.linux.cz) 7 * Copyright (C) 1999 David S. Miller (davem@redhat.com) 8 * 9 * This is a good place to start if you're trying to understand the 10 * emulation code, because it's pretty simple. What we do is 11 * essentially analyse the instruction to work out what the operation 12 * is and which registers are involved. We then execute the appropriate 13 * FXXXX function. [The floating point queue introduces a minor wrinkle; 14 * see below...] 15 * The fxxxxx.c files each emulate a single insn. They look relatively 16 * simple because the complexity is hidden away in an unholy tangle 17 * of preprocessor macros. 18 * 19 * The first layer of macros is single.h, double.h, quad.h. Generally 20 * these files define macros for working with floating point numbers 21 * of the three IEEE formats. FP_ADD_D(R,A,B) is for adding doubles, 22 * for instance. These macros are usually defined as calls to more 23 * generic macros (in this case _FP_ADD(D,2,R,X,Y) where the number 24 * of machine words required to store the given IEEE format is passed 25 * as a parameter. [double.h and co check the number of bits in a word 26 * and define FP_ADD_D & co appropriately]. 27 * The generic macros are defined in op-common.h. This is where all 28 * the grotty stuff like handling NaNs is coded. To handle the possible 29 * word sizes macros in op-common.h use macros like _FP_FRAC_SLL_##wc() 30 * where wc is the 'number of machine words' parameter (here 2). 31 * These are defined in the third layer of macros: op-1.h, op-2.h 32 * and op-4.h. These handle operations on floating point numbers composed 33 * of 1,2 and 4 machine words respectively. [For example, on sparc64 34 * doubles are one machine word so macros in double.h eventually use 35 * constructs in op-1.h, but on sparc32 they use op-2.h definitions.] 36 * soft-fp.h is on the same level as op-common.h, and defines some 37 * macros which are independent of both word size and FP format. 38 * Finally, sfp-machine.h is the machine dependent part of the 39 * code: it defines the word size and what type a word is. It also 40 * defines how _FP_MUL_MEAT_t() maps to _FP_MUL_MEAT_n_* : op-n.h 41 * provide several possible flavours of multiply algorithm, most 42 * of which require that you supply some form of asm or C primitive to 43 * do the actual multiply. (such asm primitives should be defined 44 * in sfp-machine.h too). udivmodti4.c is the same sort of thing. 45 * 46 * There may be some errors here because I'm working from a 47 * SPARC architecture manual V9, and what I really want is V8... 48 * Also, the insns which can generate exceptions seem to be a 49 * greater subset of the FPops than for V9 (for example, FCMPED 50 * has to be emulated on V8). So I think I'm going to have 51 * to emulate them all just to be on the safe side... 52 * 53 * Emulation routines originate from soft-fp package, which is 54 * part of glibc and has appropriate copyrights in it (allegedly). 55 * 56 * NB: on sparc int == long == 4 bytes, long long == 8 bytes. 57 * Most bits of the kernel seem to go for long rather than int, 58 * so we follow that practice... 59 */ 60 61 /* TODO: 62 * fpsave() saves the FP queue but fpload() doesn't reload it. 63 * Therefore when we context switch or change FPU ownership 64 * we have to check to see if the queue had anything in it and 65 * emulate it if it did. This is going to be a pain. 66 */ 67 68 #include <linux/types.h> 69 #include <linux/sched.h> 70 #include <linux/mm.h> 71 #include <linux/perf_event.h> 72 #include <linux/uaccess.h> 73 74 #include "sfp-util_32.h" 75 #include <math-emu/soft-fp.h> 76 #include <math-emu/single.h> 77 #include <math-emu/double.h> 78 #include <math-emu/quad.h> 79 80 #define FLOATFUNC(x) extern int x(void *,void *,void *) 81 82 /* The Vn labels indicate what version of the SPARC architecture gas thinks 83 * each insn is. This is from the binutils source :-> 84 */ 85 /* quadword instructions */ 86 #define FSQRTQ 0x02b /* v8 */ 87 #define FADDQ 0x043 /* v8 */ 88 #define FSUBQ 0x047 /* v8 */ 89 #define FMULQ 0x04b /* v8 */ 90 #define FDIVQ 0x04f /* v8 */ 91 #define FDMULQ 0x06e /* v8 */ 92 #define FQTOS 0x0c7 /* v8 */ 93 #define FQTOD 0x0cb /* v8 */ 94 #define FITOQ 0x0cc /* v8 */ 95 #define FSTOQ 0x0cd /* v8 */ 96 #define FDTOQ 0x0ce /* v8 */ 97 #define FQTOI 0x0d3 /* v8 */ 98 #define FCMPQ 0x053 /* v8 */ 99 #define FCMPEQ 0x057 /* v8 */ 100 /* single/double instructions (subnormal): should all work */ 101 #define FSQRTS 0x029 /* v7 */ 102 #define FSQRTD 0x02a /* v7 */ 103 #define FADDS 0x041 /* v6 */ 104 #define FADDD 0x042 /* v6 */ 105 #define FSUBS 0x045 /* v6 */ 106 #define FSUBD 0x046 /* v6 */ 107 #define FMULS 0x049 /* v6 */ 108 #define FMULD 0x04a /* v6 */ 109 #define FDIVS 0x04d /* v6 */ 110 #define FDIVD 0x04e /* v6 */ 111 #define FSMULD 0x069 /* v6 */ 112 #define FDTOS 0x0c6 /* v6 */ 113 #define FSTOD 0x0c9 /* v6 */ 114 #define FSTOI 0x0d1 /* v6 */ 115 #define FDTOI 0x0d2 /* v6 */ 116 #define FABSS 0x009 /* v6 */ 117 #define FCMPS 0x051 /* v6 */ 118 #define FCMPES 0x055 /* v6 */ 119 #define FCMPD 0x052 /* v6 */ 120 #define FCMPED 0x056 /* v6 */ 121 #define FMOVS 0x001 /* v6 */ 122 #define FNEGS 0x005 /* v6 */ 123 #define FITOS 0x0c4 /* v6 */ 124 #define FITOD 0x0c8 /* v6 */ 125 126 #define FSR_TEM_SHIFT 23UL 127 #define FSR_TEM_MASK (0x1fUL << FSR_TEM_SHIFT) 128 #define FSR_AEXC_SHIFT 5UL 129 #define FSR_AEXC_MASK (0x1fUL << FSR_AEXC_SHIFT) 130 #define FSR_CEXC_SHIFT 0UL 131 #define FSR_CEXC_MASK (0x1fUL << FSR_CEXC_SHIFT) 132 133 static int do_one_mathemu(u32 insn, unsigned long *fsr, unsigned long *fregs); 134 135 /* Unlike the Sparc64 version (which has a struct fpustate), we 136 * pass the taskstruct corresponding to the task which currently owns the 137 * FPU. This is partly because we don't have the fpustate struct and 138 * partly because the task owning the FPU isn't always current (as is 139 * the case for the Sparc64 port). This is probably SMP-related... 140 * This function returns 1 if all queued insns were emulated successfully. 141 * The test for unimplemented FPop in kernel mode has been moved into 142 * kernel/traps.c for simplicity. 143 */ 144 int do_mathemu(struct pt_regs *regs, struct task_struct *fpt) 145 { 146 /* regs->pc isn't necessarily the PC at which the offending insn is sitting. 147 * The FPU maintains a queue of FPops which cause traps. 148 * When it hits an instruction that requires that the trapped op succeeded 149 * (usually because it reads a reg. that the trapped op wrote) then it 150 * causes this exception. We need to emulate all the insns on the queue 151 * and then allow the op to proceed. 152 * This code should also handle the case where the trap was precise, 153 * in which case the queue length is zero and regs->pc points at the 154 * single FPop to be emulated. (this case is untested, though :->) 155 * You'll need this case if you want to be able to emulate all FPops 156 * because the FPU either doesn't exist or has been software-disabled. 157 * [The UltraSPARC makes FP a precise trap; this isn't as stupid as it 158 * might sound because the Ultra does funky things with a superscalar 159 * architecture.] 160 */ 161 162 /* You wouldn't believe how often I typed 'ftp' when I meant 'fpt' :-> */ 163 164 int i; 165 int retcode = 0; /* assume all succeed */ 166 unsigned long insn; 167 168 perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, 0); 169 170 #ifdef DEBUG_MATHEMU 171 printk("In do_mathemu()... pc is %08lx\n", regs->pc); 172 printk("fpqdepth is %ld\n", fpt->thread.fpqdepth); 173 for (i = 0; i < fpt->thread.fpqdepth; i++) 174 printk("%d: %08lx at %08lx\n", i, fpt->thread.fpqueue[i].insn, 175 (unsigned long)fpt->thread.fpqueue[i].insn_addr); 176 #endif 177 178 if (fpt->thread.fpqdepth == 0) { /* no queue, guilty insn is at regs->pc */ 179 #ifdef DEBUG_MATHEMU 180 printk("precise trap at %08lx\n", regs->pc); 181 #endif 182 if (!get_user(insn, (u32 __user *) regs->pc)) { 183 retcode = do_one_mathemu(insn, &fpt->thread.fsr, fpt->thread.float_regs); 184 if (retcode) { 185 /* in this case we need to fix up PC & nPC */ 186 regs->pc = regs->npc; 187 regs->npc += 4; 188 } 189 } 190 return retcode; 191 } 192 193 /* Normal case: need to empty the queue... */ 194 for (i = 0; i < fpt->thread.fpqdepth; i++) { 195 retcode = do_one_mathemu(fpt->thread.fpqueue[i].insn, &(fpt->thread.fsr), fpt->thread.float_regs); 196 if (!retcode) /* insn failed, no point doing any more */ 197 break; 198 } 199 /* Now empty the queue and clear the queue_not_empty flag */ 200 if (retcode) 201 fpt->thread.fsr &= ~(0x3000 | FSR_CEXC_MASK); 202 else 203 fpt->thread.fsr &= ~0x3000; 204 fpt->thread.fpqdepth = 0; 205 206 return retcode; 207 } 208 209 /* All routines returning an exception to raise should detect 210 * such exceptions _before_ rounding to be consistent with 211 * the behavior of the hardware in the implemented cases 212 * (and thus with the recommendations in the V9 architecture 213 * manual). 214 * 215 * We return 0 if a SIGFPE should be sent, 1 otherwise. 216 */ 217 static inline int record_exception(unsigned long *pfsr, int eflag) 218 { 219 unsigned long fsr = *pfsr; 220 int would_trap; 221 222 /* Determine if this exception would have generated a trap. */ 223 would_trap = (fsr & ((long)eflag << FSR_TEM_SHIFT)) != 0UL; 224 225 /* If trapping, we only want to signal one bit. */ 226 if (would_trap != 0) { 227 eflag &= ((fsr & FSR_TEM_MASK) >> FSR_TEM_SHIFT); 228 if ((eflag & (eflag - 1)) != 0) { 229 if (eflag & FP_EX_INVALID) 230 eflag = FP_EX_INVALID; 231 else if (eflag & FP_EX_OVERFLOW) 232 eflag = FP_EX_OVERFLOW; 233 else if (eflag & FP_EX_UNDERFLOW) 234 eflag = FP_EX_UNDERFLOW; 235 else if (eflag & FP_EX_DIVZERO) 236 eflag = FP_EX_DIVZERO; 237 else if (eflag & FP_EX_INEXACT) 238 eflag = FP_EX_INEXACT; 239 } 240 } 241 242 /* Set CEXC, here is the rule: 243 * 244 * In general all FPU ops will set one and only one 245 * bit in the CEXC field, this is always the case 246 * when the IEEE exception trap is enabled in TEM. 247 */ 248 fsr &= ~(FSR_CEXC_MASK); 249 fsr |= ((long)eflag << FSR_CEXC_SHIFT); 250 251 /* Set the AEXC field, rule is: 252 * 253 * If a trap would not be generated, the 254 * CEXC just generated is OR'd into the 255 * existing value of AEXC. 256 */ 257 if (would_trap == 0) 258 fsr |= ((long)eflag << FSR_AEXC_SHIFT); 259 260 /* If trapping, indicate fault trap type IEEE. */ 261 if (would_trap != 0) 262 fsr |= (1UL << 14); 263 264 *pfsr = fsr; 265 266 return (would_trap ? 0 : 1); 267 } 268 269 typedef union { 270 u32 s; 271 u64 d; 272 u64 q[2]; 273 } *argp; 274 275 static int do_one_mathemu(u32 insn, unsigned long *pfsr, unsigned long *fregs) 276 { 277 /* Emulate the given insn, updating fsr and fregs appropriately. */ 278 int type = 0; 279 /* r is rd, b is rs2 and a is rs1. The *u arg tells 280 whether the argument should be packed/unpacked (0 - do not unpack/pack, 1 - unpack/pack) 281 non-u args tells the size of the argument (0 - no argument, 1 - single, 2 - double, 3 - quad */ 282 #define TYPE(dummy, r, ru, b, bu, a, au) type = (au << 2) | (a << 0) | (bu << 5) | (b << 3) | (ru << 8) | (r << 6) 283 int freg; 284 argp rs1 = NULL, rs2 = NULL, rd = NULL; 285 FP_DECL_EX; 286 FP_DECL_S(SA); FP_DECL_S(SB); FP_DECL_S(SR); 287 FP_DECL_D(DA); FP_DECL_D(DB); FP_DECL_D(DR); 288 FP_DECL_Q(QA); FP_DECL_Q(QB); FP_DECL_Q(QR); 289 int IR; 290 long fsr; 291 292 #ifdef DEBUG_MATHEMU 293 printk("In do_mathemu(), emulating %08lx\n", insn); 294 #endif 295 296 if ((insn & 0xc1f80000) == 0x81a00000) /* FPOP1 */ { 297 switch ((insn >> 5) & 0x1ff) { 298 case FSQRTQ: TYPE(3,3,1,3,1,0,0); break; 299 case FADDQ: 300 case FSUBQ: 301 case FMULQ: 302 case FDIVQ: TYPE(3,3,1,3,1,3,1); break; 303 case FDMULQ: TYPE(3,3,1,2,1,2,1); break; 304 case FQTOS: TYPE(3,1,1,3,1,0,0); break; 305 case FQTOD: TYPE(3,2,1,3,1,0,0); break; 306 case FITOQ: TYPE(3,3,1,1,0,0,0); break; 307 case FSTOQ: TYPE(3,3,1,1,1,0,0); break; 308 case FDTOQ: TYPE(3,3,1,2,1,0,0); break; 309 case FQTOI: TYPE(3,1,0,3,1,0,0); break; 310 case FSQRTS: TYPE(2,1,1,1,1,0,0); break; 311 case FSQRTD: TYPE(2,2,1,2,1,0,0); break; 312 case FADDD: 313 case FSUBD: 314 case FMULD: 315 case FDIVD: TYPE(2,2,1,2,1,2,1); break; 316 case FADDS: 317 case FSUBS: 318 case FMULS: 319 case FDIVS: TYPE(2,1,1,1,1,1,1); break; 320 case FSMULD: TYPE(2,2,1,1,1,1,1); break; 321 case FDTOS: TYPE(2,1,1,2,1,0,0); break; 322 case FSTOD: TYPE(2,2,1,1,1,0,0); break; 323 case FSTOI: TYPE(2,1,0,1,1,0,0); break; 324 case FDTOI: TYPE(2,1,0,2,1,0,0); break; 325 case FITOS: TYPE(2,1,1,1,0,0,0); break; 326 case FITOD: TYPE(2,2,1,1,0,0,0); break; 327 case FMOVS: 328 case FABSS: 329 case FNEGS: TYPE(2,1,0,1,0,0,0); break; 330 } 331 } else if ((insn & 0xc1f80000) == 0x81a80000) /* FPOP2 */ { 332 switch ((insn >> 5) & 0x1ff) { 333 case FCMPS: TYPE(3,0,0,1,1,1,1); break; 334 case FCMPES: TYPE(3,0,0,1,1,1,1); break; 335 case FCMPD: TYPE(3,0,0,2,1,2,1); break; 336 case FCMPED: TYPE(3,0,0,2,1,2,1); break; 337 case FCMPQ: TYPE(3,0,0,3,1,3,1); break; 338 case FCMPEQ: TYPE(3,0,0,3,1,3,1); break; 339 } 340 } 341 342 if (!type) { /* oops, didn't recognise that FPop */ 343 #ifdef DEBUG_MATHEMU 344 printk("attempt to emulate unrecognised FPop!\n"); 345 #endif 346 return 0; 347 } 348 349 /* Decode the registers to be used */ 350 freg = (*pfsr >> 14) & 0xf; 351 352 *pfsr &= ~0x1c000; /* clear the traptype bits */ 353 354 freg = ((insn >> 14) & 0x1f); 355 switch (type & 0x3) { /* is rs1 single, double or quad? */ 356 case 3: 357 if (freg & 3) { /* quadwords must have bits 4&5 of the */ 358 /* encoded reg. number set to zero. */ 359 *pfsr |= (6 << 14); 360 return 0; /* simulate invalid_fp_register exception */ 361 } 362 fallthrough; 363 case 2: 364 if (freg & 1) { /* doublewords must have bit 5 zeroed */ 365 *pfsr |= (6 << 14); 366 return 0; 367 } 368 } 369 rs1 = (argp)&fregs[freg]; 370 switch (type & 0x7) { 371 case 7: FP_UNPACK_QP (QA, rs1); break; 372 case 6: FP_UNPACK_DP (DA, rs1); break; 373 case 5: FP_UNPACK_SP (SA, rs1); break; 374 } 375 freg = (insn & 0x1f); 376 switch ((type >> 3) & 0x3) { /* same again for rs2 */ 377 case 3: 378 if (freg & 3) { /* quadwords must have bits 4&5 of the */ 379 /* encoded reg. number set to zero. */ 380 *pfsr |= (6 << 14); 381 return 0; /* simulate invalid_fp_register exception */ 382 } 383 fallthrough; 384 case 2: 385 if (freg & 1) { /* doublewords must have bit 5 zeroed */ 386 *pfsr |= (6 << 14); 387 return 0; 388 } 389 } 390 rs2 = (argp)&fregs[freg]; 391 switch ((type >> 3) & 0x7) { 392 case 7: FP_UNPACK_QP (QB, rs2); break; 393 case 6: FP_UNPACK_DP (DB, rs2); break; 394 case 5: FP_UNPACK_SP (SB, rs2); break; 395 } 396 freg = ((insn >> 25) & 0x1f); 397 switch ((type >> 6) & 0x3) { /* and finally rd. This one's a bit different */ 398 case 0: /* dest is fcc. (this must be FCMPQ or FCMPEQ) */ 399 if (freg) { /* V8 has only one set of condition codes, so */ 400 /* anything but 0 in the rd field is an error */ 401 *pfsr |= (6 << 14); /* (should probably flag as invalid opcode */ 402 return 0; /* but SIGFPE will do :-> ) */ 403 } 404 break; 405 case 3: 406 if (freg & 3) { /* quadwords must have bits 4&5 of the */ 407 /* encoded reg. number set to zero. */ 408 *pfsr |= (6 << 14); 409 return 0; /* simulate invalid_fp_register exception */ 410 } 411 fallthrough; 412 case 2: 413 if (freg & 1) { /* doublewords must have bit 5 zeroed */ 414 *pfsr |= (6 << 14); 415 return 0; 416 } 417 fallthrough; 418 case 1: 419 rd = (void *)&fregs[freg]; 420 break; 421 } 422 #ifdef DEBUG_MATHEMU 423 printk("executing insn...\n"); 424 #endif 425 /* do the Right Thing */ 426 switch ((insn >> 5) & 0x1ff) { 427 /* + */ 428 case FADDS: FP_ADD_S (SR, SA, SB); break; 429 case FADDD: FP_ADD_D (DR, DA, DB); break; 430 case FADDQ: FP_ADD_Q (QR, QA, QB); break; 431 /* - */ 432 case FSUBS: FP_SUB_S (SR, SA, SB); break; 433 case FSUBD: FP_SUB_D (DR, DA, DB); break; 434 case FSUBQ: FP_SUB_Q (QR, QA, QB); break; 435 /* * */ 436 case FMULS: FP_MUL_S (SR, SA, SB); break; 437 case FSMULD: FP_CONV (D, S, 2, 1, DA, SA); 438 FP_CONV (D, S, 2, 1, DB, SB); 439 case FMULD: FP_MUL_D (DR, DA, DB); break; 440 case FDMULQ: FP_CONV (Q, D, 4, 2, QA, DA); 441 FP_CONV (Q, D, 4, 2, QB, DB); 442 case FMULQ: FP_MUL_Q (QR, QA, QB); break; 443 /* / */ 444 case FDIVS: FP_DIV_S (SR, SA, SB); break; 445 case FDIVD: FP_DIV_D (DR, DA, DB); break; 446 case FDIVQ: FP_DIV_Q (QR, QA, QB); break; 447 /* sqrt */ 448 case FSQRTS: FP_SQRT_S (SR, SB); break; 449 case FSQRTD: FP_SQRT_D (DR, DB); break; 450 case FSQRTQ: FP_SQRT_Q (QR, QB); break; 451 /* mov */ 452 case FMOVS: rd->s = rs2->s; break; 453 case FABSS: rd->s = rs2->s & 0x7fffffff; break; 454 case FNEGS: rd->s = rs2->s ^ 0x80000000; break; 455 /* float to int */ 456 case FSTOI: FP_TO_INT_S (IR, SB, 32, 1); break; 457 case FDTOI: FP_TO_INT_D (IR, DB, 32, 1); break; 458 case FQTOI: FP_TO_INT_Q (IR, QB, 32, 1); break; 459 /* int to float */ 460 case FITOS: IR = rs2->s; FP_FROM_INT_S (SR, IR, 32, int); break; 461 case FITOD: IR = rs2->s; FP_FROM_INT_D (DR, IR, 32, int); break; 462 case FITOQ: IR = rs2->s; FP_FROM_INT_Q (QR, IR, 32, int); break; 463 /* float to float */ 464 case FSTOD: FP_CONV (D, S, 2, 1, DR, SB); break; 465 case FSTOQ: FP_CONV (Q, S, 4, 1, QR, SB); break; 466 case FDTOQ: FP_CONV (Q, D, 4, 2, QR, DB); break; 467 case FDTOS: FP_CONV (S, D, 1, 2, SR, DB); break; 468 case FQTOS: FP_CONV (S, Q, 1, 4, SR, QB); break; 469 case FQTOD: FP_CONV (D, Q, 2, 4, DR, QB); break; 470 /* comparison */ 471 case FCMPS: 472 case FCMPES: 473 FP_CMP_S(IR, SB, SA, 3); 474 if (IR == 3 && 475 (((insn >> 5) & 0x1ff) == FCMPES || 476 FP_ISSIGNAN_S(SA) || 477 FP_ISSIGNAN_S(SB))) 478 FP_SET_EXCEPTION (FP_EX_INVALID); 479 break; 480 case FCMPD: 481 case FCMPED: 482 FP_CMP_D(IR, DB, DA, 3); 483 if (IR == 3 && 484 (((insn >> 5) & 0x1ff) == FCMPED || 485 FP_ISSIGNAN_D(DA) || 486 FP_ISSIGNAN_D(DB))) 487 FP_SET_EXCEPTION (FP_EX_INVALID); 488 break; 489 case FCMPQ: 490 case FCMPEQ: 491 FP_CMP_Q(IR, QB, QA, 3); 492 if (IR == 3 && 493 (((insn >> 5) & 0x1ff) == FCMPEQ || 494 FP_ISSIGNAN_Q(QA) || 495 FP_ISSIGNAN_Q(QB))) 496 FP_SET_EXCEPTION (FP_EX_INVALID); 497 } 498 if (!FP_INHIBIT_RESULTS) { 499 switch ((type >> 6) & 0x7) { 500 case 0: fsr = *pfsr; 501 if (IR == -1) IR = 2; 502 /* fcc is always fcc0 */ 503 fsr &= ~0xc00; fsr |= (IR << 10); 504 *pfsr = fsr; 505 break; 506 case 1: rd->s = IR; break; 507 case 5: FP_PACK_SP (rd, SR); break; 508 case 6: FP_PACK_DP (rd, DR); break; 509 case 7: FP_PACK_QP (rd, QR); break; 510 } 511 } 512 if (_fex == 0) 513 return 1; /* success! */ 514 return record_exception(pfsr, _fex); 515 } 516