1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * linux/arch/arm/vfp/vfpmodule.c 4 * 5 * Copyright (C) 2004 ARM Limited. 6 * Written by Deep Blue Solutions Limited. 7 */ 8 #include <linux/types.h> 9 #include <linux/cpu.h> 10 #include <linux/cpu_pm.h> 11 #include <linux/hardirq.h> 12 #include <linux/kernel.h> 13 #include <linux/notifier.h> 14 #include <linux/signal.h> 15 #include <linux/sched/signal.h> 16 #include <linux/smp.h> 17 #include <linux/init.h> 18 #include <linux/uaccess.h> 19 #include <linux/user.h> 20 #include <linux/export.h> 21 #include <linux/perf_event.h> 22 23 #include <asm/cp15.h> 24 #include <asm/cputype.h> 25 #include <asm/system_info.h> 26 #include <asm/thread_notify.h> 27 #include <asm/traps.h> 28 #include <asm/vfp.h> 29 #include <asm/neon.h> 30 31 #include "vfpinstr.h" 32 #include "vfp.h" 33 34 static bool have_vfp __ro_after_init; 35 36 /* 37 * Dual-use variable. 38 * Used in startup: set to non-zero if VFP checks fail 39 * After startup, holds VFP architecture 40 */ 41 static unsigned int VFP_arch; 42 43 #ifdef CONFIG_CPU_FEROCEON 44 extern unsigned int VFP_arch_feroceon __alias(VFP_arch); 45 #endif 46 47 /* 48 * The pointer to the vfpstate structure of the thread which currently 49 * owns the context held in the VFP hardware, or NULL if the hardware 50 * context is invalid. 51 * 52 * For UP, this is sufficient to tell which thread owns the VFP context. 53 * However, for SMP, we also need to check the CPU number stored in the 54 * saved state too to catch migrations. 55 */ 56 union vfp_state *vfp_current_hw_state[NR_CPUS]; 57 58 /* 59 * Is 'thread's most up to date state stored in this CPUs hardware? 60 * Must be called from non-preemptible context. 61 */ 62 static bool vfp_state_in_hw(unsigned int cpu, struct thread_info *thread) 63 { 64 #ifdef CONFIG_SMP 65 if (thread->vfpstate.hard.cpu != cpu) 66 return false; 67 #endif 68 return vfp_current_hw_state[cpu] == &thread->vfpstate; 69 } 70 71 /* 72 * Force a reload of the VFP context from the thread structure. We do 73 * this by ensuring that access to the VFP hardware is disabled, and 74 * clear vfp_current_hw_state. Must be called from non-preemptible context. 75 */ 76 static void vfp_force_reload(unsigned int cpu, struct thread_info *thread) 77 { 78 if (vfp_state_in_hw(cpu, thread)) { 79 fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN); 80 vfp_current_hw_state[cpu] = NULL; 81 } 82 #ifdef CONFIG_SMP 83 thread->vfpstate.hard.cpu = NR_CPUS; 84 #endif 85 } 86 87 /* 88 * Per-thread VFP initialization. 89 */ 90 static void vfp_thread_flush(struct thread_info *thread) 91 { 92 union vfp_state *vfp = &thread->vfpstate; 93 unsigned int cpu; 94 95 /* 96 * Disable VFP to ensure we initialize it first. We must ensure 97 * that the modification of vfp_current_hw_state[] and hardware 98 * disable are done for the same CPU and without preemption. 99 * 100 * Do this first to ensure that preemption won't overwrite our 101 * state saving should access to the VFP be enabled at this point. 102 */ 103 cpu = get_cpu(); 104 if (vfp_current_hw_state[cpu] == vfp) 105 vfp_current_hw_state[cpu] = NULL; 106 fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN); 107 put_cpu(); 108 109 memset(vfp, 0, sizeof(union vfp_state)); 110 111 vfp->hard.fpexc = FPEXC_EN; 112 vfp->hard.fpscr = FPSCR_ROUND_NEAREST; 113 #ifdef CONFIG_SMP 114 vfp->hard.cpu = NR_CPUS; 115 #endif 116 } 117 118 static void vfp_thread_exit(struct thread_info *thread) 119 { 120 /* release case: Per-thread VFP cleanup. */ 121 union vfp_state *vfp = &thread->vfpstate; 122 unsigned int cpu = get_cpu(); 123 124 if (vfp_current_hw_state[cpu] == vfp) 125 vfp_current_hw_state[cpu] = NULL; 126 put_cpu(); 127 } 128 129 static void vfp_thread_copy(struct thread_info *thread) 130 { 131 struct thread_info *parent = current_thread_info(); 132 133 vfp_sync_hwstate(parent); 134 thread->vfpstate = parent->vfpstate; 135 #ifdef CONFIG_SMP 136 thread->vfpstate.hard.cpu = NR_CPUS; 137 #endif 138 } 139 140 /* 141 * When this function is called with the following 'cmd's, the following 142 * is true while this function is being run: 143 * THREAD_NOFTIFY_SWTICH: 144 * - the previously running thread will not be scheduled onto another CPU. 145 * - the next thread to be run (v) will not be running on another CPU. 146 * - thread->cpu is the local CPU number 147 * - not preemptible as we're called in the middle of a thread switch 148 * THREAD_NOTIFY_FLUSH: 149 * - the thread (v) will be running on the local CPU, so 150 * v === current_thread_info() 151 * - thread->cpu is the local CPU number at the time it is accessed, 152 * but may change at any time. 153 * - we could be preempted if tree preempt rcu is enabled, so 154 * it is unsafe to use thread->cpu. 155 * THREAD_NOTIFY_EXIT 156 * - we could be preempted if tree preempt rcu is enabled, so 157 * it is unsafe to use thread->cpu. 158 */ 159 static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v) 160 { 161 struct thread_info *thread = v; 162 u32 fpexc; 163 #ifdef CONFIG_SMP 164 unsigned int cpu; 165 #endif 166 167 switch (cmd) { 168 case THREAD_NOTIFY_SWITCH: 169 fpexc = fmrx(FPEXC); 170 171 #ifdef CONFIG_SMP 172 cpu = thread->cpu; 173 174 /* 175 * On SMP, if VFP is enabled, save the old state in 176 * case the thread migrates to a different CPU. The 177 * restoring is done lazily. 178 */ 179 if ((fpexc & FPEXC_EN) && vfp_current_hw_state[cpu]) 180 vfp_save_state(vfp_current_hw_state[cpu], fpexc); 181 #endif 182 183 /* 184 * Always disable VFP so we can lazily save/restore the 185 * old state. 186 */ 187 fmxr(FPEXC, fpexc & ~FPEXC_EN); 188 break; 189 190 case THREAD_NOTIFY_FLUSH: 191 vfp_thread_flush(thread); 192 break; 193 194 case THREAD_NOTIFY_EXIT: 195 vfp_thread_exit(thread); 196 break; 197 198 case THREAD_NOTIFY_COPY: 199 vfp_thread_copy(thread); 200 break; 201 } 202 203 return NOTIFY_DONE; 204 } 205 206 static struct notifier_block vfp_notifier_block = { 207 .notifier_call = vfp_notifier, 208 }; 209 210 /* 211 * Raise a SIGFPE for the current process. 212 * sicode describes the signal being raised. 213 */ 214 static void vfp_raise_sigfpe(unsigned int sicode, struct pt_regs *regs) 215 { 216 /* 217 * This is the same as NWFPE, because it's not clear what 218 * this is used for 219 */ 220 current->thread.error_code = 0; 221 current->thread.trap_no = 6; 222 223 send_sig_fault(SIGFPE, sicode, 224 (void __user *)(instruction_pointer(regs) - 4), 225 current); 226 } 227 228 static void vfp_panic(char *reason, u32 inst) 229 { 230 int i; 231 232 pr_err("VFP: Error: %s\n", reason); 233 pr_err("VFP: EXC 0x%08x SCR 0x%08x INST 0x%08x\n", 234 fmrx(FPEXC), fmrx(FPSCR), inst); 235 for (i = 0; i < 32; i += 2) 236 pr_err("VFP: s%2u: 0x%08x s%2u: 0x%08x\n", 237 i, vfp_get_float(i), i+1, vfp_get_float(i+1)); 238 } 239 240 /* 241 * Process bitmask of exception conditions. 242 */ 243 static void vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr, struct pt_regs *regs) 244 { 245 int si_code = 0; 246 247 pr_debug("VFP: raising exceptions %08x\n", exceptions); 248 249 if (exceptions == VFP_EXCEPTION_ERROR) { 250 vfp_panic("unhandled bounce", inst); 251 vfp_raise_sigfpe(FPE_FLTINV, regs); 252 return; 253 } 254 255 /* 256 * If any of the status flags are set, update the FPSCR. 257 * Comparison instructions always return at least one of 258 * these flags set. 259 */ 260 if (exceptions & (FPSCR_N|FPSCR_Z|FPSCR_C|FPSCR_V)) 261 fpscr &= ~(FPSCR_N|FPSCR_Z|FPSCR_C|FPSCR_V); 262 263 fpscr |= exceptions; 264 265 fmxr(FPSCR, fpscr); 266 267 #define RAISE(stat,en,sig) \ 268 if (exceptions & stat && fpscr & en) \ 269 si_code = sig; 270 271 /* 272 * These are arranged in priority order, least to highest. 273 */ 274 RAISE(FPSCR_DZC, FPSCR_DZE, FPE_FLTDIV); 275 RAISE(FPSCR_IXC, FPSCR_IXE, FPE_FLTRES); 276 RAISE(FPSCR_UFC, FPSCR_UFE, FPE_FLTUND); 277 RAISE(FPSCR_OFC, FPSCR_OFE, FPE_FLTOVF); 278 RAISE(FPSCR_IOC, FPSCR_IOE, FPE_FLTINV); 279 280 if (si_code) 281 vfp_raise_sigfpe(si_code, regs); 282 } 283 284 /* 285 * Emulate a VFP instruction. 286 */ 287 static u32 vfp_emulate_instruction(u32 inst, u32 fpscr, struct pt_regs *regs) 288 { 289 u32 exceptions = VFP_EXCEPTION_ERROR; 290 291 pr_debug("VFP: emulate: INST=0x%08x SCR=0x%08x\n", inst, fpscr); 292 293 if (INST_CPRTDO(inst)) { 294 if (!INST_CPRT(inst)) { 295 /* 296 * CPDO 297 */ 298 if (vfp_single(inst)) { 299 exceptions = vfp_single_cpdo(inst, fpscr); 300 } else { 301 exceptions = vfp_double_cpdo(inst, fpscr); 302 } 303 } else { 304 /* 305 * A CPRT instruction can not appear in FPINST2, nor 306 * can it cause an exception. Therefore, we do not 307 * have to emulate it. 308 */ 309 } 310 } else { 311 /* 312 * A CPDT instruction can not appear in FPINST2, nor can 313 * it cause an exception. Therefore, we do not have to 314 * emulate it. 315 */ 316 } 317 perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->ARM_pc); 318 return exceptions & ~VFP_NAN_FLAG; 319 } 320 321 /* 322 * Package up a bounce condition. 323 */ 324 static void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs) 325 { 326 u32 fpscr, orig_fpscr, fpsid, exceptions; 327 328 pr_debug("VFP: bounce: trigger %08x fpexc %08x\n", trigger, fpexc); 329 330 /* 331 * At this point, FPEXC can have the following configuration: 332 * 333 * EX DEX IXE 334 * 0 1 x - synchronous exception 335 * 1 x 0 - asynchronous exception 336 * 1 x 1 - sychronous on VFP subarch 1 and asynchronous on later 337 * 0 0 1 - synchronous on VFP9 (non-standard subarch 1 338 * implementation), undefined otherwise 339 * 340 * Clear various bits and enable access to the VFP so we can 341 * handle the bounce. 342 */ 343 fmxr(FPEXC, fpexc & ~(FPEXC_EX|FPEXC_DEX|FPEXC_FP2V|FPEXC_VV|FPEXC_TRAP_MASK)); 344 345 fpsid = fmrx(FPSID); 346 orig_fpscr = fpscr = fmrx(FPSCR); 347 348 /* 349 * Check for the special VFP subarch 1 and FPSCR.IXE bit case 350 */ 351 if ((fpsid & FPSID_ARCH_MASK) == (1 << FPSID_ARCH_BIT) 352 && (fpscr & FPSCR_IXE)) { 353 /* 354 * Synchronous exception, emulate the trigger instruction 355 */ 356 goto emulate; 357 } 358 359 if (fpexc & FPEXC_EX) { 360 /* 361 * Asynchronous exception. The instruction is read from FPINST 362 * and the interrupted instruction has to be restarted. 363 */ 364 trigger = fmrx(FPINST); 365 regs->ARM_pc -= 4; 366 } else if (!(fpexc & FPEXC_DEX)) { 367 /* 368 * Illegal combination of bits. It can be caused by an 369 * unallocated VFP instruction but with FPSCR.IXE set and not 370 * on VFP subarch 1. 371 */ 372 vfp_raise_exceptions(VFP_EXCEPTION_ERROR, trigger, fpscr, regs); 373 return; 374 } 375 376 /* 377 * Modify fpscr to indicate the number of iterations remaining. 378 * If FPEXC.EX is 0, FPEXC.DEX is 1 and the FPEXC.VV bit indicates 379 * whether FPEXC.VECITR or FPSCR.LEN is used. 380 */ 381 if (fpexc & (FPEXC_EX | FPEXC_VV)) { 382 u32 len; 383 384 len = fpexc + (1 << FPEXC_LENGTH_BIT); 385 386 fpscr &= ~FPSCR_LENGTH_MASK; 387 fpscr |= (len & FPEXC_LENGTH_MASK) << (FPSCR_LENGTH_BIT - FPEXC_LENGTH_BIT); 388 } 389 390 /* 391 * Handle the first FP instruction. We used to take note of the 392 * FPEXC bounce reason, but this appears to be unreliable. 393 * Emulate the bounced instruction instead. 394 */ 395 exceptions = vfp_emulate_instruction(trigger, fpscr, regs); 396 if (exceptions) 397 vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs); 398 399 /* 400 * If there isn't a second FP instruction, exit now. Note that 401 * the FPEXC.FP2V bit is valid only if FPEXC.EX is 1. 402 */ 403 if ((fpexc & (FPEXC_EX | FPEXC_FP2V)) != (FPEXC_EX | FPEXC_FP2V)) 404 return; 405 406 /* 407 * The barrier() here prevents fpinst2 being read 408 * before the condition above. 409 */ 410 barrier(); 411 trigger = fmrx(FPINST2); 412 413 emulate: 414 exceptions = vfp_emulate_instruction(trigger, orig_fpscr, regs); 415 if (exceptions) 416 vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs); 417 } 418 419 static void vfp_enable(void *unused) 420 { 421 u32 access; 422 423 BUG_ON(preemptible()); 424 access = get_copro_access(); 425 426 /* 427 * Enable full access to VFP (cp10 and cp11) 428 */ 429 set_copro_access(access | CPACC_FULL(10) | CPACC_FULL(11)); 430 } 431 432 /* Called by platforms on which we want to disable VFP because it may not be 433 * present on all CPUs within a SMP complex. Needs to be called prior to 434 * vfp_init(). 435 */ 436 void __init vfp_disable(void) 437 { 438 if (VFP_arch) { 439 pr_debug("%s: should be called prior to vfp_init\n", __func__); 440 return; 441 } 442 VFP_arch = 1; 443 } 444 445 #ifdef CONFIG_CPU_PM 446 static int vfp_pm_suspend(void) 447 { 448 struct thread_info *ti = current_thread_info(); 449 u32 fpexc = fmrx(FPEXC); 450 451 /* if vfp is on, then save state for resumption */ 452 if (fpexc & FPEXC_EN) { 453 pr_debug("%s: saving vfp state\n", __func__); 454 vfp_save_state(&ti->vfpstate, fpexc); 455 456 /* disable, just in case */ 457 fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN); 458 } else if (vfp_current_hw_state[ti->cpu]) { 459 #ifndef CONFIG_SMP 460 fmxr(FPEXC, fpexc | FPEXC_EN); 461 vfp_save_state(vfp_current_hw_state[ti->cpu], fpexc); 462 fmxr(FPEXC, fpexc); 463 #endif 464 } 465 466 /* clear any information we had about last context state */ 467 vfp_current_hw_state[ti->cpu] = NULL; 468 469 return 0; 470 } 471 472 static void vfp_pm_resume(void) 473 { 474 /* ensure we have access to the vfp */ 475 vfp_enable(NULL); 476 477 /* and disable it to ensure the next usage restores the state */ 478 fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN); 479 } 480 481 static int vfp_cpu_pm_notifier(struct notifier_block *self, unsigned long cmd, 482 void *v) 483 { 484 switch (cmd) { 485 case CPU_PM_ENTER: 486 vfp_pm_suspend(); 487 break; 488 case CPU_PM_ENTER_FAILED: 489 case CPU_PM_EXIT: 490 vfp_pm_resume(); 491 break; 492 } 493 return NOTIFY_OK; 494 } 495 496 static struct notifier_block vfp_cpu_pm_notifier_block = { 497 .notifier_call = vfp_cpu_pm_notifier, 498 }; 499 500 static void vfp_pm_init(void) 501 { 502 cpu_pm_register_notifier(&vfp_cpu_pm_notifier_block); 503 } 504 505 #else 506 static inline void vfp_pm_init(void) { } 507 #endif /* CONFIG_CPU_PM */ 508 509 /* 510 * Ensure that the VFP state stored in 'thread->vfpstate' is up to date 511 * with the hardware state. 512 */ 513 void vfp_sync_hwstate(struct thread_info *thread) 514 { 515 unsigned int cpu = get_cpu(); 516 517 local_bh_disable(); 518 519 if (vfp_state_in_hw(cpu, thread)) { 520 u32 fpexc = fmrx(FPEXC); 521 522 /* 523 * Save the last VFP state on this CPU. 524 */ 525 fmxr(FPEXC, fpexc | FPEXC_EN); 526 vfp_save_state(&thread->vfpstate, fpexc | FPEXC_EN); 527 fmxr(FPEXC, fpexc); 528 } 529 530 local_bh_enable(); 531 put_cpu(); 532 } 533 534 /* Ensure that the thread reloads the hardware VFP state on the next use. */ 535 void vfp_flush_hwstate(struct thread_info *thread) 536 { 537 unsigned int cpu = get_cpu(); 538 539 vfp_force_reload(cpu, thread); 540 541 put_cpu(); 542 } 543 544 /* 545 * Save the current VFP state into the provided structures and prepare 546 * for entry into a new function (signal handler). 547 */ 548 int vfp_preserve_user_clear_hwstate(struct user_vfp *ufp, 549 struct user_vfp_exc *ufp_exc) 550 { 551 struct thread_info *thread = current_thread_info(); 552 struct vfp_hard_struct *hwstate = &thread->vfpstate.hard; 553 554 /* Ensure that the saved hwstate is up-to-date. */ 555 vfp_sync_hwstate(thread); 556 557 /* 558 * Copy the floating point registers. There can be unused 559 * registers see asm/hwcap.h for details. 560 */ 561 memcpy(&ufp->fpregs, &hwstate->fpregs, sizeof(hwstate->fpregs)); 562 563 /* 564 * Copy the status and control register. 565 */ 566 ufp->fpscr = hwstate->fpscr; 567 568 /* 569 * Copy the exception registers. 570 */ 571 ufp_exc->fpexc = hwstate->fpexc; 572 ufp_exc->fpinst = hwstate->fpinst; 573 ufp_exc->fpinst2 = hwstate->fpinst2; 574 575 /* Ensure that VFP is disabled. */ 576 vfp_flush_hwstate(thread); 577 578 /* 579 * As per the PCS, clear the length and stride bits for function 580 * entry. 581 */ 582 hwstate->fpscr &= ~(FPSCR_LENGTH_MASK | FPSCR_STRIDE_MASK); 583 return 0; 584 } 585 586 /* Sanitise and restore the current VFP state from the provided structures. */ 587 int vfp_restore_user_hwstate(struct user_vfp *ufp, struct user_vfp_exc *ufp_exc) 588 { 589 struct thread_info *thread = current_thread_info(); 590 struct vfp_hard_struct *hwstate = &thread->vfpstate.hard; 591 unsigned long fpexc; 592 593 /* Disable VFP to avoid corrupting the new thread state. */ 594 vfp_flush_hwstate(thread); 595 596 /* 597 * Copy the floating point registers. There can be unused 598 * registers see asm/hwcap.h for details. 599 */ 600 memcpy(&hwstate->fpregs, &ufp->fpregs, sizeof(hwstate->fpregs)); 601 /* 602 * Copy the status and control register. 603 */ 604 hwstate->fpscr = ufp->fpscr; 605 606 /* 607 * Sanitise and restore the exception registers. 608 */ 609 fpexc = ufp_exc->fpexc; 610 611 /* Ensure the VFP is enabled. */ 612 fpexc |= FPEXC_EN; 613 614 /* Ensure FPINST2 is invalid and the exception flag is cleared. */ 615 fpexc &= ~(FPEXC_EX | FPEXC_FP2V); 616 hwstate->fpexc = fpexc; 617 618 hwstate->fpinst = ufp_exc->fpinst; 619 hwstate->fpinst2 = ufp_exc->fpinst2; 620 621 return 0; 622 } 623 624 /* 625 * VFP hardware can lose all context when a CPU goes offline. 626 * As we will be running in SMP mode with CPU hotplug, we will save the 627 * hardware state at every thread switch. We clear our held state when 628 * a CPU has been killed, indicating that the VFP hardware doesn't contain 629 * a threads VFP state. When a CPU starts up, we re-enable access to the 630 * VFP hardware. The callbacks below are called on the CPU which 631 * is being offlined/onlined. 632 */ 633 static int vfp_dying_cpu(unsigned int cpu) 634 { 635 vfp_current_hw_state[cpu] = NULL; 636 return 0; 637 } 638 639 static int vfp_starting_cpu(unsigned int unused) 640 { 641 vfp_enable(NULL); 642 return 0; 643 } 644 645 static int vfp_kmode_exception(struct pt_regs *regs, unsigned int instr) 646 { 647 /* 648 * If we reach this point, a floating point exception has been raised 649 * while running in kernel mode. If the NEON/VFP unit was enabled at the 650 * time, it means a VFP instruction has been issued that requires 651 * software assistance to complete, something which is not currently 652 * supported in kernel mode. 653 * If the NEON/VFP unit was disabled, and the location pointed to below 654 * is properly preceded by a call to kernel_neon_begin(), something has 655 * caused the task to be scheduled out and back in again. In this case, 656 * rebuilding and running with CONFIG_DEBUG_ATOMIC_SLEEP enabled should 657 * be helpful in localizing the problem. 658 */ 659 if (fmrx(FPEXC) & FPEXC_EN) 660 pr_crit("BUG: unsupported FP instruction in kernel mode\n"); 661 else 662 pr_crit("BUG: FP instruction issued in kernel mode with FP unit disabled\n"); 663 pr_crit("FPEXC == 0x%08x\n", fmrx(FPEXC)); 664 return 1; 665 } 666 667 /* 668 * vfp_support_entry - Handle VFP exception 669 * 670 * @regs: pt_regs structure holding the register state at exception entry 671 * @trigger: The opcode of the instruction that triggered the exception 672 * 673 * Returns 0 if the exception was handled, or an error code otherwise. 674 */ 675 static int vfp_support_entry(struct pt_regs *regs, u32 trigger) 676 { 677 struct thread_info *ti = current_thread_info(); 678 u32 fpexc; 679 680 if (unlikely(!have_vfp)) 681 return -ENODEV; 682 683 if (!user_mode(regs)) 684 return vfp_kmode_exception(regs, trigger); 685 686 local_bh_disable(); 687 fpexc = fmrx(FPEXC); 688 689 /* 690 * If the VFP unit was not enabled yet, we have to check whether the 691 * VFP state in the CPU's registers is the most recent VFP state 692 * associated with the process. On UP systems, we don't save the VFP 693 * state eagerly on a context switch, so we may need to save the 694 * VFP state to memory first, as it may belong to another process. 695 */ 696 if (!(fpexc & FPEXC_EN)) { 697 /* 698 * Enable the VFP unit but mask the FP exception flag for the 699 * time being, so we can access all the registers. 700 */ 701 fpexc |= FPEXC_EN; 702 fmxr(FPEXC, fpexc & ~FPEXC_EX); 703 704 /* 705 * Check whether or not the VFP state in the CPU's registers is 706 * the most recent VFP state associated with this task. On SMP, 707 * migration may result in multiple CPUs holding VFP states 708 * that belong to the same task, but only the most recent one 709 * is valid. 710 */ 711 if (!vfp_state_in_hw(ti->cpu, ti)) { 712 if (!IS_ENABLED(CONFIG_SMP) && 713 vfp_current_hw_state[ti->cpu] != NULL) { 714 /* 715 * This CPU is currently holding the most 716 * recent VFP state associated with another 717 * task, and we must save that to memory first. 718 */ 719 vfp_save_state(vfp_current_hw_state[ti->cpu], 720 fpexc); 721 } 722 723 /* 724 * We can now proceed with loading the task's VFP state 725 * from memory into the CPU registers. 726 */ 727 fpexc = vfp_load_state(&ti->vfpstate); 728 vfp_current_hw_state[ti->cpu] = &ti->vfpstate; 729 #ifdef CONFIG_SMP 730 /* 731 * Record that this CPU is now the one holding the most 732 * recent VFP state of the task. 733 */ 734 ti->vfpstate.hard.cpu = ti->cpu; 735 #endif 736 } 737 738 if (fpexc & FPEXC_EX) 739 /* 740 * Might as well handle the pending exception before 741 * retrying branch out before setting an FPEXC that 742 * stops us reading stuff. 743 */ 744 goto bounce; 745 746 /* 747 * No FP exception is pending: just enable the VFP and 748 * replay the instruction that trapped. 749 */ 750 fmxr(FPEXC, fpexc); 751 } else { 752 /* Check for synchronous or asynchronous exceptions */ 753 if (!(fpexc & (FPEXC_EX | FPEXC_DEX))) { 754 u32 fpscr = fmrx(FPSCR); 755 756 /* 757 * On some implementations of the VFP subarch 1, 758 * setting FPSCR.IXE causes all the CDP instructions to 759 * be bounced synchronously without setting the 760 * FPEXC.EX bit 761 */ 762 if (!(fpscr & FPSCR_IXE)) { 763 if (!(fpscr & FPSCR_LENGTH_MASK)) { 764 pr_debug("not VFP\n"); 765 local_bh_enable(); 766 return -ENOEXEC; 767 } 768 fpexc |= FPEXC_DEX; 769 } 770 } 771 bounce: regs->ARM_pc += 4; 772 VFP_bounce(trigger, fpexc, regs); 773 } 774 775 local_bh_enable(); 776 return 0; 777 } 778 779 static struct undef_hook neon_support_hook[] = {{ 780 .instr_mask = 0xfe000000, 781 .instr_val = 0xf2000000, 782 .cpsr_mask = PSR_T_BIT, 783 .cpsr_val = 0, 784 .fn = vfp_support_entry, 785 }, { 786 .instr_mask = 0xff100000, 787 .instr_val = 0xf4000000, 788 .cpsr_mask = PSR_T_BIT, 789 .cpsr_val = 0, 790 .fn = vfp_support_entry, 791 }, { 792 .instr_mask = 0xef000000, 793 .instr_val = 0xef000000, 794 .cpsr_mask = PSR_T_BIT, 795 .cpsr_val = PSR_T_BIT, 796 .fn = vfp_support_entry, 797 }, { 798 .instr_mask = 0xff100000, 799 .instr_val = 0xf9000000, 800 .cpsr_mask = PSR_T_BIT, 801 .cpsr_val = PSR_T_BIT, 802 .fn = vfp_support_entry, 803 }}; 804 805 static struct undef_hook vfp_support_hook = { 806 .instr_mask = 0x0c000e00, 807 .instr_val = 0x0c000a00, 808 .fn = vfp_support_entry, 809 }; 810 811 #ifdef CONFIG_KERNEL_MODE_NEON 812 813 /* 814 * Kernel-side NEON support functions 815 */ 816 void kernel_neon_begin(void) 817 { 818 struct thread_info *thread = current_thread_info(); 819 unsigned int cpu; 820 u32 fpexc; 821 822 local_bh_disable(); 823 824 /* 825 * Kernel mode NEON is only allowed outside of hardirq context with 826 * preemption and softirq processing disabled. This will make sure that 827 * the kernel mode NEON register contents never need to be preserved. 828 */ 829 BUG_ON(in_hardirq()); 830 cpu = __smp_processor_id(); 831 832 fpexc = fmrx(FPEXC) | FPEXC_EN; 833 fmxr(FPEXC, fpexc); 834 835 /* 836 * Save the userland NEON/VFP state. Under UP, 837 * the owner could be a task other than 'current' 838 */ 839 if (vfp_state_in_hw(cpu, thread)) 840 vfp_save_state(&thread->vfpstate, fpexc); 841 #ifndef CONFIG_SMP 842 else if (vfp_current_hw_state[cpu] != NULL) 843 vfp_save_state(vfp_current_hw_state[cpu], fpexc); 844 #endif 845 vfp_current_hw_state[cpu] = NULL; 846 } 847 EXPORT_SYMBOL(kernel_neon_begin); 848 849 void kernel_neon_end(void) 850 { 851 /* Disable the NEON/VFP unit. */ 852 fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN); 853 local_bh_enable(); 854 } 855 EXPORT_SYMBOL(kernel_neon_end); 856 857 #endif /* CONFIG_KERNEL_MODE_NEON */ 858 859 static int __init vfp_detect(struct pt_regs *regs, unsigned int instr) 860 { 861 VFP_arch = UINT_MAX; /* mark as not present */ 862 regs->ARM_pc += 4; 863 return 0; 864 } 865 866 static struct undef_hook vfp_detect_hook __initdata = { 867 .instr_mask = 0x0c000e00, 868 .instr_val = 0x0c000a00, 869 .cpsr_mask = MODE_MASK, 870 .cpsr_val = SVC_MODE, 871 .fn = vfp_detect, 872 }; 873 874 /* 875 * VFP support code initialisation. 876 */ 877 static int __init vfp_init(void) 878 { 879 unsigned int vfpsid; 880 unsigned int cpu_arch = cpu_architecture(); 881 unsigned int isar6; 882 883 /* 884 * Enable the access to the VFP on all online CPUs so the 885 * following test on FPSID will succeed. 886 */ 887 if (cpu_arch >= CPU_ARCH_ARMv6) 888 on_each_cpu(vfp_enable, NULL, 1); 889 890 /* 891 * First check that there is a VFP that we can use. 892 * The handler is already setup to just log calls, so 893 * we just need to read the VFPSID register. 894 */ 895 register_undef_hook(&vfp_detect_hook); 896 barrier(); 897 vfpsid = fmrx(FPSID); 898 barrier(); 899 unregister_undef_hook(&vfp_detect_hook); 900 901 pr_info("VFP support v0.3: "); 902 if (VFP_arch) { 903 pr_cont("not present\n"); 904 return 0; 905 /* Extract the architecture on CPUID scheme */ 906 } else if ((read_cpuid_id() & 0x000f0000) == 0x000f0000) { 907 VFP_arch = vfpsid & FPSID_CPUID_ARCH_MASK; 908 VFP_arch >>= FPSID_ARCH_BIT; 909 /* 910 * Check for the presence of the Advanced SIMD 911 * load/store instructions, integer and single 912 * precision floating point operations. Only check 913 * for NEON if the hardware has the MVFR registers. 914 */ 915 if (IS_ENABLED(CONFIG_NEON) && 916 (fmrx(MVFR1) & 0x000fff00) == 0x00011100) { 917 elf_hwcap |= HWCAP_NEON; 918 for (int i = 0; i < ARRAY_SIZE(neon_support_hook); i++) 919 register_undef_hook(&neon_support_hook[i]); 920 } 921 922 if (IS_ENABLED(CONFIG_VFPv3)) { 923 u32 mvfr0 = fmrx(MVFR0); 924 if (((mvfr0 & MVFR0_DP_MASK) >> MVFR0_DP_BIT) == 0x2 || 925 ((mvfr0 & MVFR0_SP_MASK) >> MVFR0_SP_BIT) == 0x2) { 926 elf_hwcap |= HWCAP_VFPv3; 927 /* 928 * Check for VFPv3 D16 and VFPv4 D16. CPUs in 929 * this configuration only have 16 x 64bit 930 * registers. 931 */ 932 if ((mvfr0 & MVFR0_A_SIMD_MASK) == 1) 933 /* also v4-D16 */ 934 elf_hwcap |= HWCAP_VFPv3D16; 935 else 936 elf_hwcap |= HWCAP_VFPD32; 937 } 938 939 if ((fmrx(MVFR1) & 0xf0000000) == 0x10000000) 940 elf_hwcap |= HWCAP_VFPv4; 941 if (((fmrx(MVFR1) & MVFR1_ASIMDHP_MASK) >> MVFR1_ASIMDHP_BIT) == 0x2) 942 elf_hwcap |= HWCAP_ASIMDHP; 943 if (((fmrx(MVFR1) & MVFR1_FPHP_MASK) >> MVFR1_FPHP_BIT) == 0x3) 944 elf_hwcap |= HWCAP_FPHP; 945 } 946 947 /* 948 * Check for the presence of Advanced SIMD Dot Product 949 * instructions. 950 */ 951 isar6 = read_cpuid_ext(CPUID_EXT_ISAR6); 952 if (cpuid_feature_extract_field(isar6, 4) == 0x1) 953 elf_hwcap |= HWCAP_ASIMDDP; 954 /* 955 * Check for the presence of Advanced SIMD Floating point 956 * half-precision multiplication instructions. 957 */ 958 if (cpuid_feature_extract_field(isar6, 8) == 0x1) 959 elf_hwcap |= HWCAP_ASIMDFHM; 960 /* 961 * Check for the presence of Advanced SIMD Bfloat16 962 * floating point instructions. 963 */ 964 if (cpuid_feature_extract_field(isar6, 20) == 0x1) 965 elf_hwcap |= HWCAP_ASIMDBF16; 966 /* 967 * Check for the presence of Advanced SIMD and floating point 968 * Int8 matrix multiplication instructions instructions. 969 */ 970 if (cpuid_feature_extract_field(isar6, 24) == 0x1) 971 elf_hwcap |= HWCAP_I8MM; 972 973 /* Extract the architecture version on pre-cpuid scheme */ 974 } else { 975 if (vfpsid & FPSID_NODOUBLE) { 976 pr_cont("no double precision support\n"); 977 return 0; 978 } 979 980 VFP_arch = (vfpsid & FPSID_ARCH_MASK) >> FPSID_ARCH_BIT; 981 } 982 983 cpuhp_setup_state_nocalls(CPUHP_AP_ARM_VFP_STARTING, 984 "arm/vfp:starting", vfp_starting_cpu, 985 vfp_dying_cpu); 986 987 have_vfp = true; 988 989 register_undef_hook(&vfp_support_hook); 990 thread_register_notifier(&vfp_notifier_block); 991 vfp_pm_init(); 992 993 /* 994 * We detected VFP, and the support code is 995 * in place; report VFP support to userspace. 996 */ 997 elf_hwcap |= HWCAP_VFP; 998 999 pr_cont("implementor %02x architecture %d part %02x variant %x rev %x\n", 1000 (vfpsid & FPSID_IMPLEMENTER_MASK) >> FPSID_IMPLEMENTER_BIT, 1001 VFP_arch, 1002 (vfpsid & FPSID_PART_MASK) >> FPSID_PART_BIT, 1003 (vfpsid & FPSID_VARIANT_MASK) >> FPSID_VARIANT_BIT, 1004 (vfpsid & FPSID_REV_MASK) >> FPSID_REV_BIT); 1005 1006 return 0; 1007 } 1008 1009 core_initcall(vfp_init); 1010