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/user.h>
  25 #include <linux/init.h>
  26 #include <linux/completion.h>
  27 #include <linux/kallsyms.h>
  28 #include <linux/random.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/pgtable.h>
  36 #include <asm/mipsregs.h>
  37 #include <asm/processor.h>
  38 #include <asm/uaccess.h>
  39 #include <asm/io.h>
  40 #include <asm/elf.h>
  41 #include <asm/isadep.h>
  42 #include <asm/inst.h>
  43 #include <asm/stacktrace.h>
  44
  45 /*
  46  * The idle thread. There's no useful work to be done, so just try to conserve
  47  * power and have a low exit latency (ie sit in a loop waiting for somebody to
  48  * say that they'd like to reschedule)
  49  */
  50 void __noreturn cpu_idle(void)
  51 {
  52         int cpu;
  53
  54         /* CPU is going idle. */
  55         cpu = smp_processor_id();
  56
  57         /* endless idle loop with no priority at all */
  58         while (1) {
  59                 tick_nohz_idle_enter();
  60                 rcu_idle_enter();
  61                 while (!need_resched() && cpu_online(cpu)) {
  62 #ifdef CONFIG_MIPS_MT_SMTC
  63                         extern void smtc_idle_loop_hook(void);
  64
  65                         smtc_idle_loop_hook();
  66 #endif
  67
  68                         if (cpu_wait) {
  69                                 /* Don't trace irqs off for idle */
  70                                 stop_critical_timings();
  71                                 (*cpu_wait)();
  72                                 start_critical_timings();
  73                         }
  74                 }
  75 #ifdef CONFIG_HOTPLUG_CPU
  76                 if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map))
  77                         play_dead();
  78 #endif
  79                 rcu_idle_exit();
  80                 tick_nohz_idle_exit();
  81                 schedule_preempt_disabled();
  82         }
  83 }
  84
  85 asmlinkage void ret_from_fork(void);
  86 asmlinkage void ret_from_kernel_thread(void);
  87
  88 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
  89 {
  90         unsigned long status;
  91
  92         /* New thread loses kernel privileges. */
  93         status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
  94 #ifdef CONFIG_64BIT
  95         status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
  96 #endif
  97         status |= KU_USER;
  98         regs->cp0_status = status;
  99         clear_used_math();
 100         clear_fpu_owner();
 101         if (cpu_has_dsp)
 102                 __init_dsp();
 103         regs->cp0_epc = pc;
 104         regs->regs[29] = sp;
 105 }
 106
 107 void exit_thread(void)
 108 {
 109 }
 110
 111 void flush_thread(void)
 112 {
 113 }
 114
 115 int copy_thread(unsigned long clone_flags, unsigned long usp,
 116         unsigned long 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         p->set_child_tid = p->clear_child_tid = NULL;
 122
 123         childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
 124
 125         preempt_disable();
 126
 127         if (is_fpu_owner())
 128                 save_fp(p);
 129
 130         if (cpu_has_dsp)
 131                 save_dsp(p);
 132
 133         preempt_enable();
 134
 135         /* set up new TSS. */
 136         childregs = (struct pt_regs *) childksp - 1;
 137         /*  Put the stack after the struct pt_regs.  */
 138         childksp = (unsigned long) childregs;
 139         p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
 140         if (unlikely(p->flags & PF_KTHREAD)) {
 141                 unsigned long status = p->thread.cp0_status;
 142                 memset(childregs, 0, sizeof(struct pt_regs));
 143                 ti->addr_limit = KERNEL_DS;
 144                 p->thread.reg16 = usp; /* fn */
 145                 p->thread.reg17 = arg;
 146                 p->thread.reg29 = childksp;
 147                 p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
 148 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 149                 status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
 150                          ((status & (ST0_KUC | ST0_IEC)) << 2);
 151 #else
 152                 status |= ST0_EXL;
 153 #endif
 154                 childregs->cp0_status = status;
 155                 return 0;
 156         }
 157         *childregs = *regs;
 158         childregs->regs[7] = 0; /* Clear error flag */
 159         childregs->regs[2] = 0; /* Child gets zero as return value */
 160         if (usp)
 161                 childregs->regs[29] = usp;
 162         ti->addr_limit = USER_DS;
 163
 164         p->thread.reg29 = (unsigned long) childregs;
 165         p->thread.reg31 = (unsigned long) ret_from_fork;
 166
 167         /*
 168          * New tasks lose permission to use the fpu. This accelerates context
 169          * switching for most programs since they don't use the fpu.
 170          */
 171         childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
 172
 173 #ifdef CONFIG_MIPS_MT_SMTC
 174         /*
 175          * SMTC restores TCStatus after Status, and the CU bits
 176          * are aliased there.
 177          */
 178         childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
 179 #endif
 180         clear_tsk_thread_flag(p, TIF_USEDFPU);
 181
 182 #ifdef CONFIG_MIPS_MT_FPAFF
 183         clear_tsk_thread_flag(p, TIF_FPUBOUND);
 184 #endif /* CONFIG_MIPS_MT_FPAFF */
 185
 186         if (clone_flags & CLONE_SETTLS)
 187                 ti->tp_value = regs->regs[7];
 188
 189         return 0;
 190 }
 191
 192 /* Fill in the fpu structure for a core dump.. */
 193 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
 194 {
 195         memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
 196
 197         return 1;
 198 }
 199
 200 void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
 201 {
 202         int i;
 203
 204         for (i = 0; i < EF_R0; i++)
 205                 gp[i] = 0;
 206         gp[EF_R0] = 0;
 207         for (i = 1; i <= 31; i++)
 208                 gp[EF_R0 + i] = regs->regs[i];
 209         gp[EF_R26] = 0;
 210         gp[EF_R27] = 0;
 211         gp[EF_LO] = regs->lo;
 212         gp[EF_HI] = regs->hi;
 213         gp[EF_CP0_EPC] = regs->cp0_epc;
 214         gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
 215         gp[EF_CP0_STATUS] = regs->cp0_status;
 216         gp[EF_CP0_CAUSE] = regs->cp0_cause;
 217 #ifdef EF_UNUSED0
 218         gp[EF_UNUSED0] = 0;
 219 #endif
 220 }
 221
 222 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
 223 {
 224         elf_dump_regs(*regs, task_pt_regs(tsk));
 225         return 1;
 226 }
 227
 228 int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
 229 {
 230         memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
 231
 232         return 1;
 233 }
 234
 235 /*
 236  *
 237  */
 238 struct mips_frame_info {
 239         void            *func;
 240         unsigned long   func_size;
 241         int             frame_size;
 242         int             pc_offset;
 243 };
 244
 245 static inline int is_ra_save_ins(union mips_instruction *ip)
 246 {
 247 #ifdef CONFIG_CPU_MICROMIPS
 248         union mips_instruction mmi;
 249
 250         /*
 251          * swsp ra,offset
 252          * swm16 reglist,offset(sp)
 253          * swm32 reglist,offset(sp)
 254          * sw32 ra,offset(sp)
 255          * jradiussp - NOT SUPPORTED
 256          *
 257          * microMIPS is way more fun...
 258          */
 259         if (mm_insn_16bit(ip->halfword[0])) {
 260                 mmi.word = (ip->halfword[0] << 16);
 261                 return ((mmi.mm16_r5_format.opcode == mm_swsp16_op &&
 262                          mmi.mm16_r5_format.rt == 31) ||
 263                         (mmi.mm16_m_format.opcode == mm_pool16c_op &&
 264                          mmi.mm16_m_format.func == mm_swm16_op));
 265         }
 266         else {
 267                 mmi.halfword[0] = ip->halfword[1];
 268                 mmi.halfword[1] = ip->halfword[0];
 269                 return ((mmi.mm_m_format.opcode == mm_pool32b_op &&
 270                          mmi.mm_m_format.rd > 9 &&
 271                          mmi.mm_m_format.base == 29 &&
 272                          mmi.mm_m_format.func == mm_swm32_func) ||
 273                         (mmi.i_format.opcode == mm_sw32_op &&
 274                          mmi.i_format.rs == 29 &&
 275                          mmi.i_format.rt == 31));
 276         }
 277 #else
 278         /* sw / sd $ra, offset($sp) */
 279         return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 280                 ip->i_format.rs == 29 &&
 281                 ip->i_format.rt == 31;
 282 #endif
 283 }
 284
 285 static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
 286 {
 287 #ifdef CONFIG_CPU_MICROMIPS
 288         /*
 289          * jr16,jrc,jalr16,jalr16
 290          * jal
 291          * jalr/jr,jalr.hb/jr.hb,jalrs,jalrs.hb
 292          * jraddiusp - NOT SUPPORTED
 293          *
 294          * microMIPS is kind of more fun...
 295          */
 296         union mips_instruction mmi;
 297
 298         mmi.word = (ip->halfword[0] << 16);
 299
 300         if ((mmi.mm16_r5_format.opcode == mm_pool16c_op &&
 301             (mmi.mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op) ||
 302             ip->j_format.opcode == mm_jal32_op)
 303                 return 1;
 304         if (ip->r_format.opcode != mm_pool32a_op ||
 305                         ip->r_format.func != mm_pool32axf_op)
 306                 return 0;
 307         return (((ip->u_format.uimmediate >> 6) & mm_jalr_op) == mm_jalr_op);
 308 #else
 309         if (ip->j_format.opcode == jal_op)
 310                 return 1;
 311         if (ip->r_format.opcode != spec_op)
 312                 return 0;
 313         return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 314 #endif
 315 }
 316
 317 static inline int is_sp_move_ins(union mips_instruction *ip)
 318 {
 319 #ifdef CONFIG_CPU_MICROMIPS
 320         /*
 321          * addiusp -imm
 322          * addius5 sp,-imm
 323          * addiu32 sp,sp,-imm
 324          * jradiussp - NOT SUPPORTED
 325          *
 326          * microMIPS is not more fun...
 327          */
 328         if (mm_insn_16bit(ip->halfword[0])) {
 329                 union mips_instruction mmi;
 330
 331                 mmi.word = (ip->halfword[0] << 16);
 332                 return ((mmi.mm16_r3_format.opcode == mm_pool16d_op &&
 333                          mmi.mm16_r3_format.simmediate && mm_addiusp_func) ||
 334                         (mmi.mm16_r5_format.opcode == mm_pool16d_op &&
 335                          mmi.mm16_r5_format.rt == 29));
 336         }
 337         return (ip->mm_i_format.opcode == mm_addiu32_op &&
 338                  ip->mm_i_format.rt == 29 && ip->mm_i_format.rs == 29);
 339 #else
 340         /* addiu/daddiu sp,sp,-imm */
 341         if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 342                 return 0;
 343         if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 344                 return 1;
 345 #endif
 346         return 0;
 347 }
 348
 349 static int get_frame_info(struct mips_frame_info *info)
 350 {
 351 #ifdef CONFIG_CPU_MICROMIPS
 352         union mips_instruction *ip = (void *) (((char *) info->func) - 1);
 353 #else
 354         union mips_instruction *ip = info->func;
 355 #endif
 356         unsigned max_insns = info->func_size / sizeof(union mips_instruction);
 357         unsigned i;
 358
 359         info->pc_offset = -1;
 360         info->frame_size = 0;
 361
 362         if (!ip)
 363                 goto err;
 364
 365         if (max_insns == 0)
 366                 max_insns = 128U;       /* unknown function size */
 367         max_insns = min(128U, max_insns);
 368
 369         for (i = 0; i < max_insns; i++, ip++) {
 370
 371                 if (is_jal_jalr_jr_ins(ip))
 372                         break;
 373                 if (!info->frame_size) {
 374                         if (is_sp_move_ins(ip))
 375                         {
 376 #ifdef CONFIG_CPU_MICROMIPS
 377                                 if (mm_insn_16bit(ip->halfword[0]))
 378                                 {
 379                                         unsigned short tmp;
 380
 381                                         if (ip->halfword[0] & mm_addiusp_func)
 382                                         {
 383                                                 tmp = (((ip->halfword[0] >> 1) & 0x1ff) << 2);
 384                                                 info->frame_size = -(signed short)(tmp | ((tmp & 0x100) ? 0xfe00 : 0));
 385                                         } else {
 386                                                 tmp = (ip->halfword[0] >> 1);
 387                                                 info->frame_size = -(signed short)(tmp & 0xf);
 388                                         }
 389                                         ip = (void *) &ip->halfword[1];
 390                                         ip--;
 391                                 } else
 392 #endif
 393                                 info->frame_size = - ip->i_format.simmediate;
 394                         }
 395                         continue;
 396                 }
 397                 if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
 398                         info->pc_offset =
 399                                 ip->i_format.simmediate / sizeof(long);
 400                         break;
 401                 }
 402         }
 403         if (info->frame_size && info->pc_offset >= 0) /* nested */
 404                 return 0;
 405         if (info->pc_offset < 0) /* leaf */
 406                 return 1;
 407         /* prologue seems boggus... */
 408 err:
 409         return -1;
 410 }
 411
 412 static struct mips_frame_info schedule_mfi __read_mostly;
 413
 414 static int __init frame_info_init(void)
 415 {
 416         unsigned long size = 0;
 417 #ifdef CONFIG_KALLSYMS
 418         unsigned long ofs;
 419
 420         kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
 421 #endif
 422         schedule_mfi.func = schedule;
 423         schedule_mfi.func_size = size;
 424
 425         get_frame_info(&schedule_mfi);
 426
 427         /*
 428          * Without schedule() frame info, result given by
 429          * thread_saved_pc() and get_wchan() are not reliable.
 430          */
 431         if (schedule_mfi.pc_offset < 0)
 432                 printk("Can't analyze schedule() prologue at %p\n", schedule);
 433
 434         return 0;
 435 }
 436
 437 arch_initcall(frame_info_init);
 438
 439 /*
 440  * Return saved PC of a blocked thread.
 441  */
 442 unsigned long thread_saved_pc(struct task_struct *tsk)
 443 {
 444         struct thread_struct *t = &tsk->thread;
 445
 446         /* New born processes are a special case */
 447         if (t->reg31 == (unsigned long) ret_from_fork)
 448                 return t->reg31;
 449         if (schedule_mfi.pc_offset < 0)
 450                 return 0;
 451         return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 452 }
 453
 454
 455 #ifdef CONFIG_KALLSYMS
 456 /* generic stack unwinding function */
 457 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
 458                                               unsigned long *sp,
 459                                               unsigned long pc,
 460                                               unsigned long *ra)
 461 {
 462         struct mips_frame_info info;
 463         unsigned long size, ofs;
 464         int leaf;
 465         extern void ret_from_irq(void);
 466         extern void ret_from_exception(void);
 467
 468         if (!stack_page)
 469                 return 0;
 470
 471         /*
 472          * If we reached the bottom of interrupt context,
 473          * return saved pc in pt_regs.
 474          */
 475         if (pc == (unsigned long)ret_from_irq ||
 476             pc == (unsigned long)ret_from_exception) {
 477                 struct pt_regs *regs;
 478                 if (*sp >= stack_page &&
 479                     *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
 480                         regs = (struct pt_regs *)*sp;
 481                         pc = regs->cp0_epc;
 482                         if (__kernel_text_address(pc)) {
 483                                 *sp = regs->regs[29];
 484                                 *ra = regs->regs[31];
 485                                 return pc;
 486                         }
 487                 }
 488                 return 0;
 489         }
 490         if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 491                 return 0;
 492         /*
 493          * Return ra if an exception occurred at the first instruction
 494          */
 495         if (unlikely(ofs == 0)) {
 496                 pc = *ra;
 497                 *ra = 0;
 498                 return pc;
 499         }
 500
 501         info.func = (void *)(pc - ofs);
 502         info.func_size = ofs;   /* analyze from start to ofs */
 503         leaf = get_frame_info(&info);
 504         if (leaf < 0)
 505                 return 0;
 506
 507         if (*sp < stack_page ||
 508             *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
 509                 return 0;
 510
 511         if (leaf)
 512                 /*
 513                  * For some extreme cases, get_frame_info() can
 514                  * consider wrongly a nested function as a leaf
 515                  * one. In that cases avoid to return always the
 516                  * same value.
 517                  */
 518                 pc = pc != *ra ? *ra : 0;
 519         else
 520                 pc = ((unsigned long *)(*sp))[info.pc_offset];
 521
 522         *sp += info.frame_size;
 523         *ra = 0;
 524         return __kernel_text_address(pc) ? pc : 0;
 525 }
 526 EXPORT_SYMBOL(unwind_stack_by_address);
 527
 528 /* used by show_backtrace() */
 529 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 530                            unsigned long pc, unsigned long *ra)
 531 {
 532         unsigned long stack_page = (unsigned long)task_stack_page(task);
 533         return unwind_stack_by_address(stack_page, sp, pc, ra);
 534 }
 535 #endif
 536
 537 /*
 538  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 539  */
 540 unsigned long get_wchan(struct task_struct *task)
 541 {
 542         unsigned long pc = 0;
 543 #ifdef CONFIG_KALLSYMS
 544         unsigned long sp;
 545         unsigned long ra = 0;
 546 #endif
 547
 548         if (!task || task == current || task->state == TASK_RUNNING)
 549                 goto out;
 550         if (!task_stack_page(task))
 551                 goto out;
 552
 553         pc = thread_saved_pc(task);
 554
 555 #ifdef CONFIG_KALLSYMS
 556         sp = task->thread.reg29 + schedule_mfi.frame_size;
 557
 558         while (in_sched_functions(pc))
 559                 pc = unwind_stack(task, &sp, pc, &ra);
 560 #endif
 561
 562 out:
 563         return pc;
 564 }
 565
 566 /*
 567  * Don't forget that the stack pointer must be aligned on a 8 bytes
 568  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 569  */
 570 unsigned long arch_align_stack(unsigned long sp)
 571 {
 572         if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 573                 sp -= get_random_int() & ~PAGE_MASK;
 574
 575         return sp & ALMASK;
 576 }