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/msa.h>
  36 #include <asm/pgtable.h>
  37 #include <asm/mipsregs.h>
  38 #include <asm/processor.h>
  39 #include <asm/reg.h>
  40 #include <asm/uaccess.h>
  41 #include <asm/io.h>
  42 #include <asm/elf.h>
  43 #include <asm/isadep.h>
  44 #include <asm/inst.h>
  45 #include <asm/stacktrace.h>
  46 #include <asm/irq_regs.h>
  47
  48 #ifdef CONFIG_HOTPLUG_CPU
  49 void arch_cpu_idle_dead(void)
  50 {
  51         /* What the heck is this check doing ? */
  52         if (!cpumask_test_cpu(smp_processor_id(), &cpu_callin_map))
  53                 play_dead();
  54 }
  55 #endif
  56
  57 asmlinkage void ret_from_fork(void);
  58 asmlinkage void ret_from_kernel_thread(void);
  59
  60 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
  61 {
  62         unsigned long status;
  63
  64         /* New thread loses kernel privileges. */
  65         status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
  66         status |= KU_USER;
  67         regs->cp0_status = status;
  68         lose_fpu(0);
  69         clear_thread_flag(TIF_MSA_CTX_LIVE);
  70         clear_used_math();
  71         init_dsp();
  72         regs->cp0_epc = pc;
  73         regs->regs[29] = sp;
  74 }
  75
  76 void exit_thread(void)
  77 {
  78 }
  79
  80 void flush_thread(void)
  81 {
  82 }
  83
  84 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
  85 {
  86         /*
  87          * Save any process state which is live in hardware registers to the
  88          * parent context prior to duplication. This prevents the new child
  89          * state becoming stale if the parent is preempted before copy_thread()
  90          * gets a chance to save the parent's live hardware registers to the
  91          * child context.
  92          */
  93         preempt_disable();
  94
  95         if (is_msa_enabled())
  96                 save_msa(current);
  97         else if (is_fpu_owner())
  98                 _save_fp(current);
  99
 100         save_dsp(current);
 101
 102         preempt_enable();
 103
 104         *dst = *src;
 105         return 0;
 106 }
 107
 108 /*
 109  * Copy architecture-specific thread state
 110  */
 111 int copy_thread(unsigned long clone_flags, unsigned long usp,
 112         unsigned long kthread_arg, struct task_struct *p)
 113 {
 114         struct thread_info *ti = task_thread_info(p);
 115         struct pt_regs *childregs, *regs = current_pt_regs();
 116         unsigned long childksp;
 117         p->set_child_tid = p->clear_child_tid = NULL;
 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)
 193 {
 194 #ifdef CONFIG_CPU_MICROMIPS
 195         union mips_instruction mmi;
 196
 197         /*
 198          * swsp ra,offset
 199          * swm16 reglist,offset(sp)
 200          * swm32 reglist,offset(sp)
 201          * sw32 ra,offset(sp)
 202          * jradiussp - NOT SUPPORTED
 203          *
 204          * microMIPS is way more fun...
 205          */
 206         if (mm_insn_16bit(ip->halfword[0])) {
 207                 mmi.word = (ip->halfword[0] << 16);
 208                 return (mmi.mm16_r5_format.opcode == mm_swsp16_op &&
 209                         mmi.mm16_r5_format.rt == 31) ||
 210                        (mmi.mm16_m_format.opcode == mm_pool16c_op &&
 211                         mmi.mm16_m_format.func == mm_swm16_op);
 212         }
 213         else {
 214                 mmi.halfword[0] = ip->halfword[1];
 215                 mmi.halfword[1] = ip->halfword[0];
 216                 return (mmi.mm_m_format.opcode == mm_pool32b_op &&
 217                         mmi.mm_m_format.rd > 9 &&
 218                         mmi.mm_m_format.base == 29 &&
 219                         mmi.mm_m_format.func == mm_swm32_func) ||
 220                        (mmi.i_format.opcode == mm_sw32_op &&
 221                         mmi.i_format.rs == 29 &&
 222                         mmi.i_format.rt == 31);
 223         }
 224 #else
 225         /* sw / sd $ra, offset($sp) */
 226         return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 227                 ip->i_format.rs == 29 &&
 228                 ip->i_format.rt == 31;
 229 #endif
 230 }
 231
 232 static inline int is_jump_ins(union mips_instruction *ip)
 233 {
 234 #ifdef CONFIG_CPU_MICROMIPS
 235         /*
 236          * jr16,jrc,jalr16,jalr16
 237          * jal
 238          * jalr/jr,jalr.hb/jr.hb,jalrs,jalrs.hb
 239          * jraddiusp - NOT SUPPORTED
 240          *
 241          * microMIPS is kind of more fun...
 242          */
 243         union mips_instruction mmi;
 244
 245         mmi.word = (ip->halfword[0] << 16);
 246
 247         if ((mmi.mm16_r5_format.opcode == mm_pool16c_op &&
 248             (mmi.mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op) ||
 249             ip->j_format.opcode == mm_jal32_op)
 250                 return 1;
 251         if (ip->r_format.opcode != mm_pool32a_op ||
 252                         ip->r_format.func != mm_pool32axf_op)
 253                 return 0;
 254         return ((ip->u_format.uimmediate >> 6) & mm_jalr_op) == mm_jalr_op;
 255 #else
 256         if (ip->j_format.opcode == j_op)
 257                 return 1;
 258         if (ip->j_format.opcode == jal_op)
 259                 return 1;
 260         if (ip->r_format.opcode != spec_op)
 261                 return 0;
 262         return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 263 #endif
 264 }
 265
 266 static inline int is_sp_move_ins(union mips_instruction *ip)
 267 {
 268 #ifdef CONFIG_CPU_MICROMIPS
 269         /*
 270          * addiusp -imm
 271          * addius5 sp,-imm
 272          * addiu32 sp,sp,-imm
 273          * jradiussp - NOT SUPPORTED
 274          *
 275          * microMIPS is not more fun...
 276          */
 277         if (mm_insn_16bit(ip->halfword[0])) {
 278                 union mips_instruction mmi;
 279
 280                 mmi.word = (ip->halfword[0] << 16);
 281                 return (mmi.mm16_r3_format.opcode == mm_pool16d_op &&
 282                         mmi.mm16_r3_format.simmediate && mm_addiusp_func) ||
 283                        (mmi.mm16_r5_format.opcode == mm_pool16d_op &&
 284                         mmi.mm16_r5_format.rt == 29);
 285         }
 286         return ip->mm_i_format.opcode == mm_addiu32_op &&
 287                ip->mm_i_format.rt == 29 && ip->mm_i_format.rs == 29;
 288 #else
 289         /* addiu/daddiu sp,sp,-imm */
 290         if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 291                 return 0;
 292         if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 293                 return 1;
 294 #endif
 295         return 0;
 296 }
 297
 298 static int get_frame_info(struct mips_frame_info *info)
 299 {
 300 #ifdef CONFIG_CPU_MICROMIPS
 301         union mips_instruction *ip = (void *) (((char *) info->func) - 1);
 302 #else
 303         union mips_instruction *ip = info->func;
 304 #endif
 305         unsigned max_insns = info->func_size / sizeof(union mips_instruction);
 306         unsigned i;
 307
 308         info->pc_offset = -1;
 309         info->frame_size = 0;
 310
 311         if (!ip)
 312                 goto err;
 313
 314         if (max_insns == 0)
 315                 max_insns = 128U;       /* unknown function size */
 316         max_insns = min(128U, max_insns);
 317
 318         for (i = 0; i < max_insns; i++, ip++) {
 319
 320                 if (is_jump_ins(ip))
 321                         break;
 322                 if (!info->frame_size) {
 323                         if (is_sp_move_ins(ip))
 324                         {
 325 #ifdef CONFIG_CPU_MICROMIPS
 326                                 if (mm_insn_16bit(ip->halfword[0]))
 327                                 {
 328                                         unsigned short tmp;
 329
 330                                         if (ip->halfword[0] & mm_addiusp_func)
 331                                         {
 332                                                 tmp = (((ip->halfword[0] >> 1) & 0x1ff) << 2);
 333                                                 info->frame_size = -(signed short)(tmp | ((tmp & 0x100) ? 0xfe00 : 0));
 334                                         } else {
 335                                                 tmp = (ip->halfword[0] >> 1);
 336                                                 info->frame_size = -(signed short)(tmp & 0xf);
 337                                         }
 338                                         ip = (void *) &ip->halfword[1];
 339                                         ip--;
 340                                 } else
 341 #endif
 342                                 info->frame_size = - ip->i_format.simmediate;
 343                         }
 344                         continue;
 345                 }
 346                 if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
 347                         info->pc_offset =
 348                                 ip->i_format.simmediate / sizeof(long);
 349                         break;
 350                 }
 351         }
 352         if (info->frame_size && info->pc_offset >= 0) /* nested */
 353                 return 0;
 354         if (info->pc_offset < 0) /* leaf */
 355                 return 1;
 356         /* prologue seems boggus... */
 357 err:
 358         return -1;
 359 }
 360
 361 static struct mips_frame_info schedule_mfi __read_mostly;
 362
 363 #ifdef CONFIG_KALLSYMS
 364 static unsigned long get___schedule_addr(void)
 365 {
 366         return kallsyms_lookup_name("__schedule");
 367 }
 368 #else
 369 static unsigned long get___schedule_addr(void)
 370 {
 371         union mips_instruction *ip = (void *)schedule;
 372         int max_insns = 8;
 373         int i;
 374
 375         for (i = 0; i < max_insns; i++, ip++) {
 376                 if (ip->j_format.opcode == j_op)
 377                         return J_TARGET(ip, ip->j_format.target);
 378         }
 379         return 0;
 380 }
 381 #endif
 382
 383 static int __init frame_info_init(void)
 384 {
 385         unsigned long size = 0;
 386 #ifdef CONFIG_KALLSYMS
 387         unsigned long ofs;
 388 #endif
 389         unsigned long addr;
 390
 391         addr = get___schedule_addr();
 392         if (!addr)
 393                 addr = (unsigned long)schedule;
 394
 395 #ifdef CONFIG_KALLSYMS
 396         kallsyms_lookup_size_offset(addr, &size, &ofs);
 397 #endif
 398         schedule_mfi.func = (void *)addr;
 399         schedule_mfi.func_size = size;
 400
 401         get_frame_info(&schedule_mfi);
 402
 403         /*
 404          * Without schedule() frame info, result given by
 405          * thread_saved_pc() and get_wchan() are not reliable.
 406          */
 407         if (schedule_mfi.pc_offset < 0)
 408                 printk("Can't analyze schedule() prologue at %p\n", schedule);
 409
 410         return 0;
 411 }
 412
 413 arch_initcall(frame_info_init);
 414
 415 /*
 416  * Return saved PC of a blocked thread.
 417  */
 418 unsigned long thread_saved_pc(struct task_struct *tsk)
 419 {
 420         struct thread_struct *t = &tsk->thread;
 421
 422         /* New born processes are a special case */
 423         if (t->reg31 == (unsigned long) ret_from_fork)
 424                 return t->reg31;
 425         if (schedule_mfi.pc_offset < 0)
 426                 return 0;
 427         return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 428 }
 429
 430
 431 #ifdef CONFIG_KALLSYMS
 432 /* generic stack unwinding function */
 433 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
 434                                               unsigned long *sp,
 435                                               unsigned long pc,
 436                                               unsigned long *ra)
 437 {
 438         struct mips_frame_info info;
 439         unsigned long size, ofs;
 440         int leaf;
 441         extern void ret_from_irq(void);
 442         extern void ret_from_exception(void);
 443
 444         if (!stack_page)
 445                 return 0;
 446
 447         /*
 448          * If we reached the bottom of interrupt context,
 449          * return saved pc in pt_regs.
 450          */
 451         if (pc == (unsigned long)ret_from_irq ||
 452             pc == (unsigned long)ret_from_exception) {
 453                 struct pt_regs *regs;
 454                 if (*sp >= stack_page &&
 455                     *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
 456                         regs = (struct pt_regs *)*sp;
 457                         pc = regs->cp0_epc;
 458                         if (__kernel_text_address(pc)) {
 459                                 *sp = regs->regs[29];
 460                                 *ra = regs->regs[31];
 461                                 return pc;
 462                         }
 463                 }
 464                 return 0;
 465         }
 466         if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 467                 return 0;
 468         /*
 469          * Return ra if an exception occurred at the first instruction
 470          */
 471         if (unlikely(ofs == 0)) {
 472                 pc = *ra;
 473                 *ra = 0;
 474                 return pc;
 475         }
 476
 477         info.func = (void *)(pc - ofs);
 478         info.func_size = ofs;   /* analyze from start to ofs */
 479         leaf = get_frame_info(&info);
 480         if (leaf < 0)
 481                 return 0;
 482
 483         if (*sp < stack_page ||
 484             *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
 485                 return 0;
 486
 487         if (leaf)
 488                 /*
 489                  * For some extreme cases, get_frame_info() can
 490                  * consider wrongly a nested function as a leaf
 491                  * one. In that cases avoid to return always the
 492                  * same value.
 493                  */
 494                 pc = pc != *ra ? *ra : 0;
 495         else
 496                 pc = ((unsigned long *)(*sp))[info.pc_offset];
 497
 498         *sp += info.frame_size;
 499         *ra = 0;
 500         return __kernel_text_address(pc) ? pc : 0;
 501 }
 502 EXPORT_SYMBOL(unwind_stack_by_address);
 503
 504 /* used by show_backtrace() */
 505 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 506                            unsigned long pc, unsigned long *ra)
 507 {
 508         unsigned long stack_page = (unsigned long)task_stack_page(task);
 509         return unwind_stack_by_address(stack_page, sp, pc, ra);
 510 }
 511 #endif
 512
 513 /*
 514  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 515  */
 516 unsigned long get_wchan(struct task_struct *task)
 517 {
 518         unsigned long pc = 0;
 519 #ifdef CONFIG_KALLSYMS
 520         unsigned long sp;
 521         unsigned long ra = 0;
 522 #endif
 523
 524         if (!task || task == current || task->state == TASK_RUNNING)
 525                 goto out;
 526         if (!task_stack_page(task))
 527                 goto out;
 528
 529         pc = thread_saved_pc(task);
 530
 531 #ifdef CONFIG_KALLSYMS
 532         sp = task->thread.reg29 + schedule_mfi.frame_size;
 533
 534         while (in_sched_functions(pc))
 535                 pc = unwind_stack(task, &sp, pc, &ra);
 536 #endif
 537
 538 out:
 539         return pc;
 540 }
 541
 542 /*
 543  * Don't forget that the stack pointer must be aligned on a 8 bytes
 544  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 545  */
 546 unsigned long arch_align_stack(unsigned long sp)
 547 {
 548         if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 549                 sp -= get_random_int() & ~PAGE_MASK;
 550
 551         return sp & ALMASK;
 552 }
 553
 554 static void arch_dump_stack(void *info)
 555 {
 556         struct pt_regs *regs;
 557
 558         regs = get_irq_regs();
 559
 560         if (regs)
 561                 show_regs(regs);
 562
 563         dump_stack();
 564 }
 565
 566 void arch_trigger_all_cpu_backtrace(bool include_self)
 567 {
 568         smp_call_function(arch_dump_stack, NULL, 1);
 569 }
 570
 571 int mips_get_process_fp_mode(struct task_struct *task)
 572 {
 573         int value = 0;
 574
 575         if (!test_tsk_thread_flag(task, TIF_32BIT_FPREGS))
 576                 value |= PR_FP_MODE_FR;
 577         if (test_tsk_thread_flag(task, TIF_HYBRID_FPREGS))
 578                 value |= PR_FP_MODE_FRE;
 579
 580         return value;
 581 }
 582
 583 int mips_set_process_fp_mode(struct task_struct *task, unsigned int value)
 584 {
 585         const unsigned int known_bits = PR_FP_MODE_FR | PR_FP_MODE_FRE;
 586         unsigned long switch_count;
 587         struct task_struct *t;
 588
 589         /* Check the value is valid */
 590         if (value & ~known_bits)
 591                 return -EOPNOTSUPP;
 592
 593         /* Avoid inadvertently triggering emulation */
 594         if ((value & PR_FP_MODE_FR) && cpu_has_fpu &&
 595             !(current_cpu_data.fpu_id & MIPS_FPIR_F64))
 596                 return -EOPNOTSUPP;
 597         if ((value & PR_FP_MODE_FRE) && cpu_has_fpu && !cpu_has_fre)
 598                 return -EOPNOTSUPP;
 599
 600         /* FR = 0 not supported in MIPS R6 */
 601         if (!(value & PR_FP_MODE_FR) && cpu_has_fpu && cpu_has_mips_r6)
 602                 return -EOPNOTSUPP;
 603
 604         /* Save FP & vector context, then disable FPU & MSA */
 605         if (task->signal == current->signal)
 606                 lose_fpu(1);
 607
 608         /* Prevent any threads from obtaining live FP context */
 609         atomic_set(&task->mm->context.fp_mode_switching, 1);
 610         smp_mb__after_atomic();
 611
 612         /*
 613          * If there are multiple online CPUs then wait until all threads whose
 614          * FP mode is about to change have been context switched. This approach
 615          * allows us to only worry about whether an FP mode switch is in
 616          * progress when FP is first used in a tasks time slice. Pretty much all
 617          * of the mode switch overhead can thus be confined to cases where mode
 618          * switches are actually occuring. That is, to here. However for the
 619          * thread performing the mode switch it may take a while...
 620          */
 621         if (num_online_cpus() > 1) {
 622                 spin_lock_irq(&task->sighand->siglock);
 623
 624                 for_each_thread(task, t) {
 625                         if (t == current)
 626                                 continue;
 627
 628                         switch_count = t->nvcsw + t->nivcsw;
 629
 630                         do {
 631                                 spin_unlock_irq(&task->sighand->siglock);
 632                                 cond_resched();
 633                                 spin_lock_irq(&task->sighand->siglock);
 634                         } while ((t->nvcsw + t->nivcsw) == switch_count);
 635                 }
 636
 637                 spin_unlock_irq(&task->sighand->siglock);
 638         }
 639
 640         /*
 641          * There are now no threads of the process with live FP context, so it
 642          * is safe to proceed with the FP mode switch.
 643          */
 644         for_each_thread(task, t) {
 645                 /* Update desired FP register width */
 646                 if (value & PR_FP_MODE_FR) {
 647                         clear_tsk_thread_flag(t, TIF_32BIT_FPREGS);
 648                 } else {
 649                         set_tsk_thread_flag(t, TIF_32BIT_FPREGS);
 650                         clear_tsk_thread_flag(t, TIF_MSA_CTX_LIVE);
 651                 }
 652
 653                 /* Update desired FP single layout */
 654                 if (value & PR_FP_MODE_FRE)
 655                         set_tsk_thread_flag(t, TIF_HYBRID_FPREGS);
 656                 else
 657                         clear_tsk_thread_flag(t, TIF_HYBRID_FPREGS);
 658         }
 659
 660         /* Allow threads to use FP again */
 661         atomic_set(&task->mm->context.fp_mode_switching, 0);
 662
 663         return 0;
 664 }