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)
 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                 return (ip->mm16_r5_format.opcode == mm_swsp16_op &&
 213                         ip->mm16_r5_format.rt == 31) ||
 214                        (ip->mm16_m_format.opcode == mm_pool16c_op &&
 215                         ip->mm16_m_format.func == mm_swm16_op);
 216         }
 217         else {
 218                 return (ip->mm_m_format.opcode == mm_pool32b_op &&
 219                         ip->mm_m_format.rd > 9 &&
 220                         ip->mm_m_format.base == 29 &&
 221                         ip->mm_m_format.func == mm_swm32_func) ||
 222                        (ip->i_format.opcode == mm_sw32_op &&
 223                         ip->i_format.rs == 29 &&
 224                         ip->i_format.rt == 31);
 225         }
 226 #else
 227         /* sw / sd $ra, offset($sp) */
 228         return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 229                 ip->i_format.rs == 29 &&
 230                 ip->i_format.rt == 31;
 231 #endif
 232 }
 233
 234 static inline int is_jump_ins(union mips_instruction *ip)
 235 {
 236 #ifdef CONFIG_CPU_MICROMIPS
 237         /*
 238          * jr16,jrc,jalr16,jalr16
 239          * jal
 240          * jalr/jr,jalr.hb/jr.hb,jalrs,jalrs.hb
 241          * jraddiusp - NOT SUPPORTED
 242          *
 243          * microMIPS is kind of more fun...
 244          */
 245         if ((ip->mm16_r5_format.opcode == mm_pool16c_op &&
 246             (ip->mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op) ||
 247             ip->j_format.opcode == mm_jal32_op)
 248                 return 1;
 249         if (ip->r_format.opcode != mm_pool32a_op ||
 250                         ip->r_format.func != mm_pool32axf_op)
 251                 return 0;
 252         return ((ip->u_format.uimmediate >> 6) & mm_jalr_op) == mm_jalr_op;
 253 #else
 254         if (ip->j_format.opcode == j_op)
 255                 return 1;
 256         if (ip->j_format.opcode == jal_op)
 257                 return 1;
 258         if (ip->r_format.opcode != spec_op)
 259                 return 0;
 260         return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 261 #endif
 262 }
 263
 264 static inline int is_sp_move_ins(union mips_instruction *ip)
 265 {
 266 #ifdef CONFIG_CPU_MICROMIPS
 267         /*
 268          * addiusp -imm
 269          * addius5 sp,-imm
 270          * addiu32 sp,sp,-imm
 271          * jradiussp - NOT SUPPORTED
 272          *
 273          * microMIPS is not more fun...
 274          */
 275         if (mm_insn_16bit(ip->halfword[1])) {
 276                 return (ip->mm16_r3_format.opcode == mm_pool16d_op &&
 277                         ip->mm16_r3_format.simmediate && mm_addiusp_func) ||
 278                        (ip->mm16_r5_format.opcode == mm_pool16d_op &&
 279                         ip->mm16_r5_format.rt == 29);
 280         }
 281
 282         return ip->mm_i_format.opcode == mm_addiu32_op &&
 283                ip->mm_i_format.rt == 29 && ip->mm_i_format.rs == 29;
 284 #else
 285         /* addiu/daddiu sp,sp,-imm */
 286         if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 287                 return 0;
 288         if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 289                 return 1;
 290 #endif
 291         return 0;
 292 }
 293
 294 static int get_frame_info(struct mips_frame_info *info)
 295 {
 296         bool is_mmips = IS_ENABLED(CONFIG_CPU_MICROMIPS);
 297         union mips_instruction insn, *ip, *ip_end;
 298         const unsigned int max_insns = 128;
 299         unsigned int i;
 300
 301         info->pc_offset = -1;
 302         info->frame_size = 0;
 303
 304         ip = (void *)msk_isa16_mode((ulong)info->func);
 305         if (!ip)
 306                 goto err;
 307
 308         ip_end = (void *)ip + info->func_size;
 309
 310         for (i = 0; i < max_insns && ip < ip_end; i++, ip++) {
 311                 if (is_mmips && mm_insn_16bit(ip->halfword[0])) {
 312                         insn.halfword[0] = 0;
 313                         insn.halfword[1] = ip->halfword[0];
 314                 } else if (is_mmips) {
 315                         insn.halfword[0] = ip->halfword[1];
 316                         insn.halfword[1] = ip->halfword[0];
 317                 } else {
 318                         insn.word = ip->word;
 319                 }
 320
 321                 if (is_jump_ins(&insn))
 322                         break;
 323
 324                 if (!info->frame_size) {
 325                         if (is_sp_move_ins(&insn))
 326                         {
 327 #ifdef CONFIG_CPU_MICROMIPS
 328                                 if (mm_insn_16bit(ip->halfword[0]))
 329                                 {
 330                                         unsigned short tmp;
 331
 332                                         if (ip->halfword[0] & mm_addiusp_func)
 333                                         {
 334                                                 tmp = (((ip->halfword[0] >> 1) & 0x1ff) << 2);
 335                                                 info->frame_size = -(signed short)(tmp | ((tmp & 0x100) ? 0xfe00 : 0));
 336                                         } else {
 337                                                 tmp = (ip->halfword[0] >> 1);
 338                                                 info->frame_size = -(signed short)(tmp & 0xf);
 339                                         }
 340                                         ip = (void *) &ip->halfword[1];
 341                                         ip--;
 342                                 } else
 343 #endif
 344                                 info->frame_size = - ip->i_format.simmediate;
 345                         }
 346                         continue;
 347                 }
 348                 if (info->pc_offset == -1 && is_ra_save_ins(&insn)) {
 349                         info->pc_offset =
 350                                 ip->i_format.simmediate / sizeof(long);
 351                         break;
 352                 }
 353         }
 354         if (info->frame_size && info->pc_offset >= 0) /* nested */
 355                 return 0;
 356         if (info->pc_offset < 0) /* leaf */
 357                 return 1;
 358         /* prologue seems bogus... */
 359 err:
 360         return -1;
 361 }
 362
 363 static struct mips_frame_info schedule_mfi __read_mostly;
 364
 365 #ifdef CONFIG_KALLSYMS
 366 static unsigned long get___schedule_addr(void)
 367 {
 368         return kallsyms_lookup_name("__schedule");
 369 }
 370 #else
 371 static unsigned long get___schedule_addr(void)
 372 {
 373         union mips_instruction *ip = (void *)schedule;
 374         int max_insns = 8;
 375         int i;
 376
 377         for (i = 0; i < max_insns; i++, ip++) {
 378                 if (ip->j_format.opcode == j_op)
 379                         return J_TARGET(ip, ip->j_format.target);
 380         }
 381         return 0;
 382 }
 383 #endif
 384
 385 static int __init frame_info_init(void)
 386 {
 387         unsigned long size = 0;
 388 #ifdef CONFIG_KALLSYMS
 389         unsigned long ofs;
 390 #endif
 391         unsigned long addr;
 392
 393         addr = get___schedule_addr();
 394         if (!addr)
 395                 addr = (unsigned long)schedule;
 396
 397 #ifdef CONFIG_KALLSYMS
 398         kallsyms_lookup_size_offset(addr, &size, &ofs);
 399 #endif
 400         schedule_mfi.func = (void *)addr;
 401         schedule_mfi.func_size = size;
 402
 403         get_frame_info(&schedule_mfi);
 404
 405         /*
 406          * Without schedule() frame info, result given by
 407          * thread_saved_pc() and get_wchan() are not reliable.
 408          */
 409         if (schedule_mfi.pc_offset < 0)
 410                 printk("Can't analyze schedule() prologue at %p\n", schedule);
 411
 412         return 0;
 413 }
 414
 415 arch_initcall(frame_info_init);
 416
 417 /*
 418  * Return saved PC of a blocked thread.
 419  */
 420 unsigned long thread_saved_pc(struct task_struct *tsk)
 421 {
 422         struct thread_struct *t = &tsk->thread;
 423
 424         /* New born processes are a special case */
 425         if (t->reg31 == (unsigned long) ret_from_fork)
 426                 return t->reg31;
 427         if (schedule_mfi.pc_offset < 0)
 428                 return 0;
 429         return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 430 }
 431
 432
 433 #ifdef CONFIG_KALLSYMS
 434 /* generic stack unwinding function */
 435 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
 436                                               unsigned long *sp,
 437                                               unsigned long pc,
 438                                               unsigned long *ra)
 439 {
 440         struct mips_frame_info info;
 441         unsigned long size, ofs;
 442         int leaf;
 443         extern void ret_from_irq(void);
 444         extern void ret_from_exception(void);
 445
 446         if (!stack_page)
 447                 return 0;
 448
 449         /*
 450          * If we reached the bottom of interrupt context,
 451          * return saved pc in pt_regs.
 452          */
 453         if (pc == (unsigned long)ret_from_irq ||
 454             pc == (unsigned long)ret_from_exception) {
 455                 struct pt_regs *regs;
 456                 if (*sp >= stack_page &&
 457                     *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
 458                         regs = (struct pt_regs *)*sp;
 459                         pc = regs->cp0_epc;
 460                         if (!user_mode(regs) && __kernel_text_address(pc)) {
 461                                 *sp = regs->regs[29];
 462                                 *ra = regs->regs[31];
 463                                 return pc;
 464                         }
 465                 }
 466                 return 0;
 467         }
 468         if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 469                 return 0;
 470         /*
 471          * Return ra if an exception occurred at the first instruction
 472          */
 473         if (unlikely(ofs == 0)) {
 474                 pc = *ra;
 475                 *ra = 0;
 476                 return pc;
 477         }
 478
 479         info.func = (void *)(pc - ofs);
 480         info.func_size = ofs;   /* analyze from start to ofs */
 481         leaf = get_frame_info(&info);
 482         if (leaf < 0)
 483                 return 0;
 484
 485         if (*sp < stack_page ||
 486             *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
 487                 return 0;
 488
 489         if (leaf)
 490                 /*
 491                  * For some extreme cases, get_frame_info() can
 492                  * consider wrongly a nested function as a leaf
 493                  * one. In that cases avoid to return always the
 494                  * same value.
 495                  */
 496                 pc = pc != *ra ? *ra : 0;
 497         else
 498                 pc = ((unsigned long *)(*sp))[info.pc_offset];
 499
 500         *sp += info.frame_size;
 501         *ra = 0;
 502         return __kernel_text_address(pc) ? pc : 0;
 503 }
 504 EXPORT_SYMBOL(unwind_stack_by_address);
 505
 506 /* used by show_backtrace() */
 507 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 508                            unsigned long pc, unsigned long *ra)
 509 {
 510         unsigned long stack_page = 0;
 511         int cpu;
 512
 513         for_each_possible_cpu(cpu) {
 514                 if (on_irq_stack(cpu, *sp)) {
 515                         stack_page = (unsigned long)irq_stack[cpu];
 516                         break;
 517                 }
 518         }
 519
 520         if (!stack_page)
 521                 stack_page = (unsigned long)task_stack_page(task);
 522
 523         return unwind_stack_by_address(stack_page, sp, pc, ra);
 524 }
 525 #endif
 526
 527 /*
 528  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 529  */
 530 unsigned long get_wchan(struct task_struct *task)
 531 {
 532         unsigned long pc = 0;
 533 #ifdef CONFIG_KALLSYMS
 534         unsigned long sp;
 535         unsigned long ra = 0;
 536 #endif
 537
 538         if (!task || task == current || task->state == TASK_RUNNING)
 539                 goto out;
 540         if (!task_stack_page(task))
 541                 goto out;
 542
 543         pc = thread_saved_pc(task);
 544
 545 #ifdef CONFIG_KALLSYMS
 546         sp = task->thread.reg29 + schedule_mfi.frame_size;
 547
 548         while (in_sched_functions(pc))
 549                 pc = unwind_stack(task, &sp, pc, &ra);
 550 #endif
 551
 552 out:
 553         return pc;
 554 }
 555
 556 /*
 557  * Don't forget that the stack pointer must be aligned on a 8 bytes
 558  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 559  */
 560 unsigned long arch_align_stack(unsigned long sp)
 561 {
 562         if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 563                 sp -= get_random_int() & ~PAGE_MASK;
 564
 565         return sp & ALMASK;
 566 }
 567
 568 static void arch_dump_stack(void *info)
 569 {
 570         struct pt_regs *regs;
 571
 572         regs = get_irq_regs();
 573
 574         if (regs)
 575                 show_regs(regs);
 576
 577         dump_stack();
 578 }
 579
 580 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 581 {
 582         long this_cpu = get_cpu();
 583
 584         if (cpumask_test_cpu(this_cpu, mask) && !exclude_self)
 585                 dump_stack();
 586
 587         smp_call_function_many(mask, arch_dump_stack, NULL, 1);
 588
 589         put_cpu();
 590 }
 591
 592 int mips_get_process_fp_mode(struct task_struct *task)
 593 {
 594         int value = 0;
 595
 596         if (!test_tsk_thread_flag(task, TIF_32BIT_FPREGS))
 597                 value |= PR_FP_MODE_FR;
 598         if (test_tsk_thread_flag(task, TIF_HYBRID_FPREGS))
 599                 value |= PR_FP_MODE_FRE;
 600
 601         return value;
 602 }
 603
 604 static void prepare_for_fp_mode_switch(void *info)
 605 {
 606         struct mm_struct *mm = info;
 607
 608         if (current->mm == mm)
 609                 lose_fpu(1);
 610 }
 611
 612 int mips_set_process_fp_mode(struct task_struct *task, unsigned int value)
 613 {
 614         const unsigned int known_bits = PR_FP_MODE_FR | PR_FP_MODE_FRE;
 615         struct task_struct *t;
 616         int max_users;
 617
 618         /* Check the value is valid */
 619         if (value & ~known_bits)
 620                 return -EOPNOTSUPP;
 621
 622         /* Avoid inadvertently triggering emulation */
 623         if ((value & PR_FP_MODE_FR) && raw_cpu_has_fpu &&
 624             !(raw_current_cpu_data.fpu_id & MIPS_FPIR_F64))
 625                 return -EOPNOTSUPP;
 626         if ((value & PR_FP_MODE_FRE) && raw_cpu_has_fpu && !cpu_has_fre)
 627                 return -EOPNOTSUPP;
 628
 629         /* FR = 0 not supported in MIPS R6 */
 630         if (!(value & PR_FP_MODE_FR) && raw_cpu_has_fpu && cpu_has_mips_r6)
 631                 return -EOPNOTSUPP;
 632
 633         /* Proceed with the mode switch */
 634         preempt_disable();
 635
 636         /* Save FP & vector context, then disable FPU & MSA */
 637         if (task->signal == current->signal)
 638                 lose_fpu(1);
 639
 640         /* Prevent any threads from obtaining live FP context */
 641         atomic_set(&task->mm->context.fp_mode_switching, 1);
 642         smp_mb__after_atomic();
 643
 644         /*
 645          * If there are multiple online CPUs then force any which are running
 646          * threads in this process to lose their FPU context, which they can't
 647          * regain until fp_mode_switching is cleared later.
 648          */
 649         if (num_online_cpus() > 1) {
 650                 /* No need to send an IPI for the local CPU */
 651                 max_users = (task->mm == current->mm) ? 1 : 0;
 652
 653                 if (atomic_read(&current->mm->mm_users) > max_users)
 654                         smp_call_function(prepare_for_fp_mode_switch,
 655                                           (void *)current->mm, 1);
 656         }
 657
 658         /*
 659          * There are now no threads of the process with live FP context, so it
 660          * is safe to proceed with the FP mode switch.
 661          */
 662         for_each_thread(task, t) {
 663                 /* Update desired FP register width */
 664                 if (value & PR_FP_MODE_FR) {
 665                         clear_tsk_thread_flag(t, TIF_32BIT_FPREGS);
 666                 } else {
 667                         set_tsk_thread_flag(t, TIF_32BIT_FPREGS);
 668                         clear_tsk_thread_flag(t, TIF_MSA_CTX_LIVE);
 669                 }
 670
 671                 /* Update desired FP single layout */
 672                 if (value & PR_FP_MODE_FRE)
 673                         set_tsk_thread_flag(t, TIF_HYBRID_FPREGS);
 674                 else
 675                         clear_tsk_thread_flag(t, TIF_HYBRID_FPREGS);
 676         }
 677
 678         /* Allow threads to use FP again */
 679         atomic_set(&task->mm->context.fp_mode_switching, 0);
 680         preempt_enable();
 681
 682         return 0;
 683 }