arch/mips/kernel/process.c

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 1994 - 1999, 2000 by Ralf Baechle and others.
   7  * Copyright (C) 2005, 2006 by Ralf Baechle (ralf@linux-mips.org)
   8  * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
   9  * Copyright (C) 2004 Thiemo Seufer
  10  * Copyright (C) 2013  Imagination Technologies Ltd.
  11  */
  12 #include <linux/errno.h>
  13 #include <linux/sched.h>
  14 #include <linux/tick.h>
  15 #include <linux/kernel.h>
  16 #include <linux/mm.h>
  17 #include <linux/stddef.h>
  18 #include <linux/unistd.h>
  19 #include <linux/export.h>
  20 #include <linux/ptrace.h>
  21 #include <linux/mman.h>
  22 #include <linux/personality.h>
  23 #include <linux/sys.h>
  24 #include <linux/init.h>
  25 #include <linux/completion.h>
  26 #include <linux/kallsyms.h>
  27 #include <linux/random.h>
  28 #include <linux/prctl.h>
  29
  30 #include <asm/asm.h>
  31 #include <asm/bootinfo.h>
  32 #include <asm/cpu.h>
  33 #include <asm/dsp.h>
  34 #include <asm/fpu.h>
  35 #include <asm/irq.h>
  36 #include <asm/msa.h>
  37 #include <asm/pgtable.h>
  38 #include <asm/mipsregs.h>
  39 #include <asm/processor.h>
  40 #include <asm/reg.h>
  41 #include <asm/uaccess.h>
  42 #include <asm/io.h>
  43 #include <asm/elf.h>
  44 #include <asm/isadep.h>
  45 #include <asm/inst.h>
  46 #include <asm/stacktrace.h>
  47 #include <asm/irq_regs.h>
  48
  49 #ifdef CONFIG_HOTPLUG_CPU
  50 void arch_cpu_idle_dead(void)
  51 {
  52         play_dead();
  53 }
  54 #endif
  55
  56 asmlinkage void ret_from_fork(void);
  57 asmlinkage void ret_from_kernel_thread(void);
  58
  59 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
  60 {
  61         unsigned long status;
  62
  63         /* New thread loses kernel privileges. */
  64         status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
  65         status |= KU_USER;
  66         regs->cp0_status = status;
  67         clear_used_math();
  68         clear_fpu_owner();
  69         init_dsp();
  70         clear_thread_flag(TIF_USEDMSA);
  71         clear_thread_flag(TIF_MSA_CTX_LIVE);
  72         disable_msa();
  73         regs->cp0_epc = pc;
  74         regs->regs[29] = sp;
  75 }
  76
  77 void exit_thread(void)
  78 {
  79 }
  80
  81 void flush_thread(void)
  82 {
  83 }
  84
  85 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
  86 {
  87         /*
  88          * Save any process state which is live in hardware registers to the
  89          * parent context prior to duplication. This prevents the new child
  90          * state becoming stale if the parent is preempted before copy_thread()
  91          * gets a chance to save the parent's live hardware registers to the
  92          * child context.
  93          */
  94         preempt_disable();
  95
  96         if (is_msa_enabled())
  97                 save_msa(current);
  98         else if (is_fpu_owner())
  99                 _save_fp(current);
 100
 101         save_dsp(current);
 102
 103         preempt_enable();
 104
 105         *dst = *src;
 106         return 0;
 107 }
 108
 109 /*
 110  * Copy architecture-specific thread state
 111  */
 112 int copy_thread(unsigned long clone_flags, unsigned long usp,
 113         unsigned long kthread_arg, struct task_struct *p)
 114 {
 115         struct thread_info *ti = task_thread_info(p);
 116         struct pt_regs *childregs, *regs = current_pt_regs();
 117         unsigned long childksp;
 118
 119         childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
 120
 121         /* set up new TSS. */
 122         childregs = (struct pt_regs *) childksp - 1;
 123         /*  Put the stack after the struct pt_regs.  */
 124         childksp = (unsigned long) childregs;
 125         p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
 126         if (unlikely(p->flags & PF_KTHREAD)) {
 127                 /* kernel thread */
 128                 unsigned long status = p->thread.cp0_status;
 129                 memset(childregs, 0, sizeof(struct pt_regs));
 130                 ti->addr_limit = KERNEL_DS;
 131                 p->thread.reg16 = usp; /* fn */
 132                 p->thread.reg17 = kthread_arg;
 133                 p->thread.reg29 = childksp;
 134                 p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
 135 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 136                 status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
 137                          ((status & (ST0_KUC | ST0_IEC)) << 2);
 138 #else
 139                 status |= ST0_EXL;
 140 #endif
 141                 childregs->cp0_status = status;
 142                 return 0;
 143         }
 144
 145         /* user thread */
 146         *childregs = *regs;
 147         childregs->regs[7] = 0; /* Clear error flag */
 148         childregs->regs[2] = 0; /* Child gets zero as return value */
 149         if (usp)
 150                 childregs->regs[29] = usp;
 151         ti->addr_limit = USER_DS;
 152
 153         p->thread.reg29 = (unsigned long) childregs;
 154         p->thread.reg31 = (unsigned long) ret_from_fork;
 155
 156         /*
 157          * New tasks lose permission to use the fpu. This accelerates context
 158          * switching for most programs since they don't use the fpu.
 159          */
 160         childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
 161
 162         clear_tsk_thread_flag(p, TIF_USEDFPU);
 163         clear_tsk_thread_flag(p, TIF_USEDMSA);
 164         clear_tsk_thread_flag(p, TIF_MSA_CTX_LIVE);
 165
 166 #ifdef CONFIG_MIPS_MT_FPAFF
 167         clear_tsk_thread_flag(p, TIF_FPUBOUND);
 168 #endif /* CONFIG_MIPS_MT_FPAFF */
 169
 170         if (clone_flags & CLONE_SETTLS)
 171                 ti->tp_value = regs->regs[7];
 172
 173         return 0;
 174 }
 175
 176 #ifdef CONFIG_CC_STACKPROTECTOR
 177 #include <linux/stackprotector.h>
 178 unsigned long __stack_chk_guard __read_mostly;
 179 EXPORT_SYMBOL(__stack_chk_guard);
 180 #endif
 181
 182 struct mips_frame_info {
 183         void            *func;
 184         unsigned long   func_size;
 185         int             frame_size;
 186         int             pc_offset;
 187 };
 188
 189 #define J_TARGET(pc,target)     \
 190                 (((unsigned long)(pc) & 0xf0000000) | ((target) << 2))
 191
 192 static inline int is_ra_save_ins(union mips_instruction *ip, int *poff)
 193 {
 194 #ifdef CONFIG_CPU_MICROMIPS
 195         /*
 196          * swsp ra,offset
 197          * swm16 reglist,offset(sp)
 198          * swm32 reglist,offset(sp)
 199          * sw32 ra,offset(sp)
 200          * jradiussp - NOT SUPPORTED
 201          *
 202          * microMIPS is way more fun...
 203          */
 204         if (mm_insn_16bit(ip->halfword[1])) {
 205                 switch (ip->mm16_r5_format.opcode) {
 206                 case mm_swsp16_op:
 207                         if (ip->mm16_r5_format.rt != 31)
 208                                 return 0;
 209
 210                         *poff = ip->mm16_r5_format.imm;
 211                         *poff = (*poff << 2) / sizeof(ulong);
 212                         return 1;
 213
 214                 case mm_pool16c_op:
 215                         switch (ip->mm16_m_format.func) {
 216                         case mm_swm16_op:
 217                                 *poff = ip->mm16_m_format.imm;
 218                                 *poff += 1 + ip->mm16_m_format.rlist;
 219                                 *poff = (*poff << 2) / sizeof(ulong);
 220                                 return 1;
 221
 222                         default:
 223                                 return 0;
 224                         }
 225
 226                 default:
 227                         return 0;
 228                 }
 229         }
 230
 231         switch (ip->i_format.opcode) {
 232         case mm_sw32_op:
 233                 if (ip->i_format.rs != 29)
 234                         return 0;
 235                 if (ip->i_format.rt != 31)
 236                         return 0;
 237
 238                 *poff = ip->i_format.simmediate / sizeof(ulong);
 239                 return 1;
 240
 241         case mm_pool32b_op:
 242                 switch (ip->mm_m_format.func) {
 243                 case mm_swm32_func:
 244                         if (ip->mm_m_format.rd < 0x10)
 245                                 return 0;
 246                         if (ip->mm_m_format.base != 29)
 247                                 return 0;
 248
 249                         *poff = ip->mm_m_format.simmediate;
 250                         *poff += (ip->mm_m_format.rd & 0xf) * sizeof(u32);
 251                         *poff /= sizeof(ulong);
 252                         return 1;
 253                 default:
 254                         return 0;
 255                 }
 256
 257         default:
 258                 return 0;
 259         }
 260 #else
 261         /* sw / sd $ra, offset($sp) */
 262         if ((ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 263                 ip->i_format.rs == 29 && ip->i_format.rt == 31) {
 264                 *poff = ip->i_format.simmediate / sizeof(ulong);
 265                 return 1;
 266         }
 267
 268         return 0;
 269 #endif
 270 }
 271
 272 static inline int is_jump_ins(union mips_instruction *ip)
 273 {
 274 #ifdef CONFIG_CPU_MICROMIPS
 275         /*
 276          * jr16,jrc,jalr16,jalr16
 277          * jal
 278          * jalr/jr,jalr.hb/jr.hb,jalrs,jalrs.hb
 279          * jraddiusp - NOT SUPPORTED
 280          *
 281          * microMIPS is kind of more fun...
 282          */
 283         if (mm_insn_16bit(ip->halfword[1])) {
 284                 if ((ip->mm16_r5_format.opcode == mm_pool16c_op &&
 285                     (ip->mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op))
 286                         return 1;
 287                 return 0;
 288         }
 289
 290         if (ip->j_format.opcode == mm_j32_op)
 291                 return 1;
 292         if (ip->j_format.opcode == mm_jal32_op)
 293                 return 1;
 294         if (ip->r_format.opcode != mm_pool32a_op ||
 295                         ip->r_format.func != mm_pool32axf_op)
 296                 return 0;
 297         return ((ip->u_format.uimmediate >> 6) & mm_jalr_op) == mm_jalr_op;
 298 #else
 299         if (ip->j_format.opcode == j_op)
 300                 return 1;
 301         if (ip->j_format.opcode == jal_op)
 302                 return 1;
 303         if (ip->r_format.opcode != spec_op)
 304                 return 0;
 305         return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 306 #endif
 307 }
 308
 309 static inline int is_sp_move_ins(union mips_instruction *ip)
 310 {
 311 #ifdef CONFIG_CPU_MICROMIPS
 312         /*
 313          * addiusp -imm
 314          * addius5 sp,-imm
 315          * addiu32 sp,sp,-imm
 316          * jradiussp - NOT SUPPORTED
 317          *
 318          * microMIPS is not more fun...
 319          */
 320         if (mm_insn_16bit(ip->halfword[1])) {
 321                 return (ip->mm16_r3_format.opcode == mm_pool16d_op &&
 322                         ip->mm16_r3_format.simmediate && mm_addiusp_func) ||
 323                        (ip->mm16_r5_format.opcode == mm_pool16d_op &&
 324                         ip->mm16_r5_format.rt == 29);
 325         }
 326
 327         return ip->mm_i_format.opcode == mm_addiu32_op &&
 328                ip->mm_i_format.rt == 29 && ip->mm_i_format.rs == 29;
 329 #else
 330         /* addiu/daddiu sp,sp,-imm */
 331         if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 332                 return 0;
 333         if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 334                 return 1;
 335 #endif
 336         return 0;
 337 }
 338
 339 static int get_frame_info(struct mips_frame_info *info)
 340 {
 341         bool is_mmips = IS_ENABLED(CONFIG_CPU_MICROMIPS);
 342         union mips_instruction insn, *ip;
 343         const unsigned int max_insns = 128;
 344         unsigned int last_insn_size = 0;
 345         unsigned int i;
 346
 347         info->pc_offset = -1;
 348         info->frame_size = 0;
 349
 350         ip = (void *)msk_isa16_mode((ulong)info->func);
 351         if (!ip)
 352                 goto err;
 353
 354         for (i = 0; i < max_insns; i++) {
 355                 ip = (void *)ip + last_insn_size;
 356
 357                 if (is_mmips && mm_insn_16bit(ip->halfword[0])) {
 358                         insn.halfword[0] = 0;
 359                         insn.halfword[1] = ip->halfword[0];
 360                         last_insn_size = 2;
 361                 } else if (is_mmips) {
 362                         insn.halfword[0] = ip->halfword[1];
 363                         insn.halfword[1] = ip->halfword[0];
 364                         last_insn_size = 4;
 365                 } else {
 366                         insn.word = ip->word;
 367                         last_insn_size = 4;
 368                 }
 369
 370                 if (is_jump_ins(&insn))
 371                         break;
 372
 373                 if (!info->frame_size) {
 374                         if (is_sp_move_ins(&insn))
 375                         {
 376 #ifdef CONFIG_CPU_MICROMIPS
 377                                 if (mm_insn_16bit(ip->halfword[0]))
 378                                 {
 379                                         unsigned short tmp;
 380
 381                                         if (ip->halfword[0] & mm_addiusp_func)
 382                                         {
 383                                                 tmp = (((ip->halfword[0] >> 1) & 0x1ff) << 2);
 384                                                 info->frame_size = -(signed short)(tmp | ((tmp & 0x100) ? 0xfe00 : 0));
 385                                         } else {
 386                                                 tmp = (ip->halfword[0] >> 1);
 387                                                 info->frame_size = -(signed short)(tmp & 0xf);
 388                                         }
 389                                 } else
 390 #endif
 391                                 info->frame_size = - ip->i_format.simmediate;
 392                         }
 393                         continue;
 394                 }
 395                 if (info->pc_offset == -1 &&
 396                     is_ra_save_ins(&insn, &info->pc_offset))
 397                         break;
 398         }
 399         if (info->frame_size && info->pc_offset >= 0) /* nested */
 400                 return 0;
 401         if (info->pc_offset < 0) /* leaf */
 402                 return 1;
 403         /* prologue seems boggus... */
 404 err:
 405         return -1;
 406 }
 407
 408 static struct mips_frame_info schedule_mfi __read_mostly;
 409
 410 #ifdef CONFIG_KALLSYMS
 411 static unsigned long get___schedule_addr(void)
 412 {
 413         return kallsyms_lookup_name("__schedule");
 414 }
 415 #else
 416 static unsigned long get___schedule_addr(void)
 417 {
 418         union mips_instruction *ip = (void *)schedule;
 419         int max_insns = 8;
 420         int i;
 421
 422         for (i = 0; i < max_insns; i++, ip++) {
 423                 if (ip->j_format.opcode == j_op)
 424                         return J_TARGET(ip, ip->j_format.target);
 425         }
 426         return 0;
 427 }
 428 #endif
 429
 430 static int __init frame_info_init(void)
 431 {
 432         unsigned long size = 0;
 433 #ifdef CONFIG_KALLSYMS
 434         unsigned long ofs;
 435 #endif
 436         unsigned long addr;
 437
 438         addr = get___schedule_addr();
 439         if (!addr)
 440                 addr = (unsigned long)schedule;
 441
 442 #ifdef CONFIG_KALLSYMS
 443         kallsyms_lookup_size_offset(addr, &size, &ofs);
 444 #endif
 445         schedule_mfi.func = (void *)addr;
 446         schedule_mfi.func_size = size;
 447
 448         get_frame_info(&schedule_mfi);
 449
 450         /*
 451          * Without schedule() frame info, result given by
 452          * thread_saved_pc() and get_wchan() are not reliable.
 453          */
 454         if (schedule_mfi.pc_offset < 0)
 455                 printk("Can't analyze schedule() prologue at %p\n", schedule);
 456
 457         return 0;
 458 }
 459
 460 arch_initcall(frame_info_init);
 461
 462 /*
 463  * Return saved PC of a blocked thread.
 464  */
 465 unsigned long thread_saved_pc(struct task_struct *tsk)
 466 {
 467         struct thread_struct *t = &tsk->thread;
 468
 469         /* New born processes are a special case */
 470         if (t->reg31 == (unsigned long) ret_from_fork)
 471                 return t->reg31;
 472         if (schedule_mfi.pc_offset < 0)
 473                 return 0;
 474         return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 475 }
 476
 477
 478 #ifdef CONFIG_KALLSYMS
 479 /* generic stack unwinding function */
 480 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
 481                                               unsigned long *sp,
 482                                               unsigned long pc,
 483                                               unsigned long *ra)
 484 {
 485         unsigned long low, high, irq_stack_high;
 486         struct mips_frame_info info;
 487         unsigned long size, ofs;
 488         struct pt_regs *regs;
 489         int leaf;
 490
 491         if (!stack_page)
 492                 return 0;
 493
 494         /*
 495          * IRQ stacks start at IRQ_STACK_START
 496          * task stacks at THREAD_SIZE - 32
 497          */
 498         low = stack_page;
 499         if (!preemptible() && on_irq_stack(raw_smp_processor_id(), *sp)) {
 500                 high = stack_page + IRQ_STACK_START;
 501                 irq_stack_high = high;
 502         } else {
 503                 high = stack_page + THREAD_SIZE - 32;
 504                 irq_stack_high = 0;
 505         }
 506
 507         /*
 508          * If we reached the top of the interrupt stack, start unwinding
 509          * the interrupted task stack.
 510          */
 511         if (unlikely(*sp == irq_stack_high)) {
 512                 unsigned long task_sp = *(unsigned long *)*sp;
 513
 514                 /*
 515                  * Check that the pointer saved in the IRQ stack head points to
 516                  * something within the stack of the current task
 517                  */
 518                 if (!object_is_on_stack((void *)task_sp))
 519                         return 0;
 520
 521                 /*
 522                  * Follow pointer to tasks kernel stack frame where interrupted
 523                  * state was saved.
 524                  */
 525                 regs = (struct pt_regs *)task_sp;
 526                 pc = regs->cp0_epc;
 527                 if (!user_mode(regs) && __kernel_text_address(pc)) {
 528                         *sp = regs->regs[29];
 529                         *ra = regs->regs[31];
 530                         return pc;
 531                 }
 532                 return 0;
 533         }
 534         if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 535                 return 0;
 536         /*
 537          * Return ra if an exception occurred at the first instruction
 538          */
 539         if (unlikely(ofs == 0)) {
 540                 pc = *ra;
 541                 *ra = 0;
 542                 return pc;
 543         }
 544
 545         info.func = (void *)(pc - ofs);
 546         info.func_size = ofs;   /* analyze from start to ofs */
 547         leaf = get_frame_info(&info);
 548         if (leaf < 0)
 549                 return 0;
 550
 551         if (*sp < low || *sp + info.frame_size > high)
 552                 return 0;
 553
 554         if (leaf)
 555                 /*
 556                  * For some extreme cases, get_frame_info() can
 557                  * consider wrongly a nested function as a leaf
 558                  * one. In that cases avoid to return always the
 559                  * same value.
 560                  */
 561                 pc = pc != *ra ? *ra : 0;
 562         else
 563                 pc = ((unsigned long *)(*sp))[info.pc_offset];
 564
 565         *sp += info.frame_size;
 566         *ra = 0;
 567         return __kernel_text_address(pc) ? pc : 0;
 568 }
 569 EXPORT_SYMBOL(unwind_stack_by_address);
 570
 571 /* used by show_backtrace() */
 572 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 573                            unsigned long pc, unsigned long *ra)
 574 {
 575         unsigned long stack_page = 0;
 576         int cpu;
 577
 578         for_each_possible_cpu(cpu) {
 579                 if (on_irq_stack(cpu, *sp)) {
 580                         stack_page = (unsigned long)irq_stack[cpu];
 581                         break;
 582                 }
 583         }
 584
 585         if (!stack_page)
 586                 stack_page = (unsigned long)task_stack_page(task);
 587
 588         return unwind_stack_by_address(stack_page, sp, pc, ra);
 589 }
 590 #endif
 591
 592 /*
 593  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 594  */
 595 unsigned long get_wchan(struct task_struct *task)
 596 {
 597         unsigned long pc = 0;
 598 #ifdef CONFIG_KALLSYMS
 599         unsigned long sp;
 600         unsigned long ra = 0;
 601 #endif
 602
 603         if (!task || task == current || task->state == TASK_RUNNING)
 604                 goto out;
 605         if (!task_stack_page(task))
 606                 goto out;
 607
 608         pc = thread_saved_pc(task);
 609
 610 #ifdef CONFIG_KALLSYMS
 611         sp = task->thread.reg29 + schedule_mfi.frame_size;
 612
 613         while (in_sched_functions(pc))
 614                 pc = unwind_stack(task, &sp, pc, &ra);
 615 #endif
 616
 617 out:
 618         return pc;
 619 }
 620
 621 /*
 622  * Don't forget that the stack pointer must be aligned on a 8 bytes
 623  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 624  */
 625 unsigned long arch_align_stack(unsigned long sp)
 626 {
 627         if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 628                 sp -= get_random_int() & ~PAGE_MASK;
 629
 630         return sp & ALMASK;
 631 }
 632
 633 static DEFINE_PER_CPU(struct call_single_data, backtrace_csd);
 634 static struct cpumask backtrace_csd_busy;
 635
 636 static void arch_dump_stack(void *info)
 637 {
 638         struct pt_regs *regs;
 639         static arch_spinlock_t lock = __ARCH_SPIN_LOCK_UNLOCKED;
 640
 641         arch_spin_lock(&lock);
 642         regs = get_irq_regs();
 643
 644         if (regs)
 645                 show_regs(regs);
 646         else
 647                 dump_stack();
 648         arch_spin_unlock(&lock);
 649
 650         cpumask_clear_cpu(smp_processor_id(), &backtrace_csd_busy);
 651 }
 652
 653 void arch_trigger_all_cpu_backtrace(bool include_self)
 654 {
 655         struct call_single_data *csd;
 656         int cpu;
 657
 658         for_each_cpu(cpu, cpu_online_mask) {
 659                 /*
 660                  * If we previously sent an IPI to the target CPU & it hasn't
 661                  * cleared its bit in the busy cpumask then it didn't handle
 662                  * our previous IPI & it's not safe for us to reuse the
 663                  * call_single_data_t.
 664                  */
 665                 if (cpumask_test_and_set_cpu(cpu, &backtrace_csd_busy)) {
 666                         pr_warn("Unable to send backtrace IPI to CPU%u - perhaps it hung?\n",
 667                                 cpu);
 668                         continue;
 669                 }
 670
 671                 csd = &per_cpu(backtrace_csd, cpu);
 672                 csd->func = arch_dump_stack;
 673                 smp_call_function_single_async(cpu, csd);
 674         }
 675 }
 676
 677 int mips_get_process_fp_mode(struct task_struct *task)
 678 {
 679         int value = 0;
 680
 681         if (!test_tsk_thread_flag(task, TIF_32BIT_FPREGS))
 682                 value |= PR_FP_MODE_FR;
 683         if (test_tsk_thread_flag(task, TIF_HYBRID_FPREGS))
 684                 value |= PR_FP_MODE_FRE;
 685
 686         return value;
 687 }
 688
 689 int mips_set_process_fp_mode(struct task_struct *task, unsigned int value)
 690 {
 691         const unsigned int known_bits = PR_FP_MODE_FR | PR_FP_MODE_FRE;
 692         unsigned long switch_count;
 693         struct task_struct *t;
 694
 695         /* If nothing to change, return right away, successfully.  */
 696         if (value == mips_get_process_fp_mode(task))
 697                 return 0;
 698
 699         /* Only accept a mode change if 64-bit FP enabled for o32.  */
 700         if (!IS_ENABLED(CONFIG_MIPS_O32_FP64_SUPPORT))
 701                 return -EOPNOTSUPP;
 702
 703         /* And only for o32 tasks.  */
 704         if (IS_ENABLED(CONFIG_64BIT) && !test_thread_flag(TIF_32BIT_REGS))
 705                 return -EOPNOTSUPP;
 706
 707         /* Check the value is valid */
 708         if (value & ~known_bits)
 709                 return -EOPNOTSUPP;
 710
 711         /* Setting FRE without FR is not supported.  */
 712         if ((value & (PR_FP_MODE_FR | PR_FP_MODE_FRE)) == PR_FP_MODE_FRE)
 713                 return -EOPNOTSUPP;
 714
 715         /* Avoid inadvertently triggering emulation */
 716         if ((value & PR_FP_MODE_FR) && raw_cpu_has_fpu &&
 717             !(raw_current_cpu_data.fpu_id & MIPS_FPIR_F64))
 718                 return -EOPNOTSUPP;
 719         if ((value & PR_FP_MODE_FRE) && raw_cpu_has_fpu && !cpu_has_fre)
 720                 return -EOPNOTSUPP;
 721
 722         /* FR = 0 not supported in MIPS R6 */
 723         if (!(value & PR_FP_MODE_FR) && raw_cpu_has_fpu && cpu_has_mips_r6)
 724                 return -EOPNOTSUPP;
 725
 726         /* Proceed with the mode switch */
 727         preempt_disable();
 728
 729         /* Save FP & vector context, then disable FPU & MSA */
 730         if (task->signal == current->signal)
 731                 lose_fpu(1);
 732
 733         /* Prevent any threads from obtaining live FP context */
 734         atomic_set(&task->mm->context.fp_mode_switching, 1);
 735         smp_mb__after_atomic();
 736
 737         /*
 738          * If there are multiple online CPUs then wait until all threads whose
 739          * FP mode is about to change have been context switched. This approach
 740          * allows us to only worry about whether an FP mode switch is in
 741          * progress when FP is first used in a tasks time slice. Pretty much all
 742          * of the mode switch overhead can thus be confined to cases where mode
 743          * switches are actually occuring. That is, to here. However for the
 744          * thread performing the mode switch it may take a while...
 745          */
 746         if (num_online_cpus() > 1) {
 747                 spin_lock_irq(&task->sighand->siglock);
 748
 749                 for_each_thread(task, t) {
 750                         if (t == current)
 751                                 continue;
 752
 753                         switch_count = t->nvcsw + t->nivcsw;
 754
 755                         do {
 756                                 spin_unlock_irq(&task->sighand->siglock);
 757                                 cond_resched();
 758                                 spin_lock_irq(&task->sighand->siglock);
 759                         } while ((t->nvcsw + t->nivcsw) == switch_count);
 760                 }
 761
 762                 spin_unlock_irq(&task->sighand->siglock);
 763         }
 764
 765         /*
 766          * There are now no threads of the process with live FP context, so it
 767          * is safe to proceed with the FP mode switch.
 768          */
 769         for_each_thread(task, t) {
 770                 /* Update desired FP register width */
 771                 if (value & PR_FP_MODE_FR) {
 772                         clear_tsk_thread_flag(t, TIF_32BIT_FPREGS);
 773                 } else {
 774                         set_tsk_thread_flag(t, TIF_32BIT_FPREGS);
 775                         clear_tsk_thread_flag(t, TIF_MSA_CTX_LIVE);
 776                 }
 777
 778                 /* Update desired FP single layout */
 779                 if (value & PR_FP_MODE_FRE)
 780                         set_tsk_thread_flag(t, TIF_HYBRID_FPREGS);
 781                 else
 782                         clear_tsk_thread_flag(t, TIF_HYBRID_FPREGS);
 783         }
 784
 785         /* Allow threads to use FP again */
 786         atomic_set(&task->mm->context.fp_mode_switching, 0);
 787         preempt_enable();
 788
 789         return 0;
 790 }