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