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