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  */
  11 #include <linux/errno.h>
  12 #include <linux/sched.h>
  13 #include <linux/tick.h>
  14 #include <linux/kernel.h>
  15 #include <linux/mm.h>
  16 #include <linux/stddef.h>
  17 #include <linux/unistd.h>
  18 #include <linux/export.h>
  19 #include <linux/ptrace.h>
  20 #include <linux/mman.h>
  21 #include <linux/personality.h>
  22 #include <linux/sys.h>
  23 #include <linux/user.h>
  24 #include <linux/init.h>
  25 #include <linux/completion.h>
  26 #include <linux/kallsyms.h>
  27 #include <linux/random.h>
  28
  29 #include <asm/asm.h>
  30 #include <asm/bootinfo.h>
  31 #include <asm/cpu.h>
  32 #include <asm/dsp.h>
  33 #include <asm/fpu.h>
  34 #include <asm/pgtable.h>
  35 #include <asm/mipsregs.h>
  36 #include <asm/processor.h>
  37 #include <asm/uaccess.h>
  38 #include <asm/io.h>
  39 #include <asm/elf.h>
  40 #include <asm/isadep.h>
  41 #include <asm/inst.h>
  42 #include <asm/stacktrace.h>
  43
  44 /*
  45  * The idle thread. There's no useful work to be done, so just try to conserve
  46  * power and have a low exit latency (ie sit in a loop waiting for somebody to
  47  * say that they'd like to reschedule)
  48  */
  49 void __noreturn cpu_idle(void)
  50 {
  51         int cpu;
  52
  53         /* CPU is going idle. */
  54         cpu = smp_processor_id();
  55
  56         /* endless idle loop with no priority at all */
  57         while (1) {
  58                 tick_nohz_idle_enter();
  59                 rcu_idle_enter();
  60                 while (!need_resched() && cpu_online(cpu)) {
  61 #ifdef CONFIG_MIPS_MT_SMTC
  62                         extern void smtc_idle_loop_hook(void);
  63
  64                         smtc_idle_loop_hook();
  65 #endif
  66
  67                         if (cpu_wait) {
  68                                 /* Don't trace irqs off for idle */
  69                                 stop_critical_timings();
  70                                 (*cpu_wait)();
  71                                 start_critical_timings();
  72                         }
  73                 }
  74 #ifdef CONFIG_HOTPLUG_CPU
  75                 if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map))
  76                         play_dead();
  77 #endif
  78                 rcu_idle_exit();
  79                 tick_nohz_idle_exit();
  80                 schedule_preempt_disabled();
  81         }
  82 }
  83
  84 asmlinkage void ret_from_fork(void);
  85
  86 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
  87 {
  88         unsigned long status;
  89
  90         /* New thread loses kernel privileges. */
  91         status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
  92 #ifdef CONFIG_64BIT
  93         status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
  94 #endif
  95         status |= KU_USER;
  96         regs->cp0_status = status;
  97         clear_used_math();
  98         clear_fpu_owner();
  99         if (cpu_has_dsp)
 100                 __init_dsp();
 101         regs->cp0_epc = pc;
 102         regs->regs[29] = sp;
 103 }
 104
 105 void exit_thread(void)
 106 {
 107 }
 108
 109 void flush_thread(void)
 110 {
 111 }
 112
 113 int copy_thread(unsigned long clone_flags, unsigned long usp,
 114         unsigned long unused, struct task_struct *p, struct pt_regs *regs)
 115 {
 116         struct thread_info *ti = task_thread_info(p);
 117         struct pt_regs *childregs;
 118         unsigned long childksp;
 119         p->set_child_tid = p->clear_child_tid = NULL;
 120
 121         childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
 122
 123         preempt_disable();
 124
 125         if (is_fpu_owner())
 126                 save_fp(p);
 127
 128         if (cpu_has_dsp)
 129                 save_dsp(p);
 130
 131         preempt_enable();
 132
 133         /* set up new TSS. */
 134         childregs = (struct pt_regs *) childksp - 1;
 135         /*  Put the stack after the struct pt_regs.  */
 136         childksp = (unsigned long) childregs;
 137         *childregs = *regs;
 138         childregs->regs[7] = 0; /* Clear error flag */
 139
 140         childregs->regs[2] = 0; /* Child gets zero as return value */
 141
 142         if (childregs->cp0_status & ST0_CU0) {
 143                 childregs->regs[28] = (unsigned long) ti;
 144                 childregs->regs[29] = childksp;
 145                 ti->addr_limit = KERNEL_DS;
 146         } else {
 147                 childregs->regs[29] = usp;
 148                 ti->addr_limit = USER_DS;
 149         }
 150         p->thread.reg29 = (unsigned long) childregs;
 151         p->thread.reg31 = (unsigned long) ret_from_fork;
 152
 153         /*
 154          * New tasks lose permission to use the fpu. This accelerates context
 155          * switching for most programs since they don't use the fpu.
 156          */
 157         p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
 158         childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
 159
 160 #ifdef CONFIG_MIPS_MT_SMTC
 161         /*
 162          * SMTC restores TCStatus after Status, and the CU bits
 163          * are aliased there.
 164          */
 165         childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
 166 #endif
 167         clear_tsk_thread_flag(p, TIF_USEDFPU);
 168
 169 #ifdef CONFIG_MIPS_MT_FPAFF
 170         clear_tsk_thread_flag(p, TIF_FPUBOUND);
 171 #endif /* CONFIG_MIPS_MT_FPAFF */
 172
 173         if (clone_flags & CLONE_SETTLS)
 174                 ti->tp_value = regs->regs[7];
 175
 176         return 0;
 177 }
 178
 179 /* Fill in the fpu structure for a core dump.. */
 180 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
 181 {
 182         memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
 183
 184         return 1;
 185 }
 186
 187 void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
 188 {
 189         int i;
 190
 191         for (i = 0; i < EF_R0; i++)
 192                 gp[i] = 0;
 193         gp[EF_R0] = 0;
 194         for (i = 1; i <= 31; i++)
 195                 gp[EF_R0 + i] = regs->regs[i];
 196         gp[EF_R26] = 0;
 197         gp[EF_R27] = 0;
 198         gp[EF_LO] = regs->lo;
 199         gp[EF_HI] = regs->hi;
 200         gp[EF_CP0_EPC] = regs->cp0_epc;
 201         gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
 202         gp[EF_CP0_STATUS] = regs->cp0_status;
 203         gp[EF_CP0_CAUSE] = regs->cp0_cause;
 204 #ifdef EF_UNUSED0
 205         gp[EF_UNUSED0] = 0;
 206 #endif
 207 }
 208
 209 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
 210 {
 211         elf_dump_regs(*regs, task_pt_regs(tsk));
 212         return 1;
 213 }
 214
 215 int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
 216 {
 217         memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
 218
 219         return 1;
 220 }
 221
 222 /*
 223  * Create a kernel thread
 224  */
 225 static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *))
 226 {
 227         do_exit(fn(arg));
 228 }
 229
 230 long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
 231 {
 232         struct pt_regs regs;
 233
 234         memset(&regs, 0, sizeof(regs));
 235
 236         regs.regs[4] = (unsigned long) arg;
 237         regs.regs[5] = (unsigned long) fn;
 238         regs.cp0_epc = (unsigned long) kernel_thread_helper;
 239         regs.cp0_status = read_c0_status();
 240 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 241         regs.cp0_status = (regs.cp0_status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
 242                           ((regs.cp0_status & (ST0_KUC | ST0_IEC)) << 2);
 243 #else
 244         regs.cp0_status |= ST0_EXL;
 245 #endif
 246
 247         /* Ok, create the new process.. */
 248         return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
 249 }
 250
 251 /*
 252  *
 253  */
 254 struct mips_frame_info {
 255         void            *func;
 256         unsigned long   func_size;
 257         int             frame_size;
 258         int             pc_offset;
 259 };
 260
 261 static inline int is_ra_save_ins(union mips_instruction *ip)
 262 {
 263         /* sw / sd $ra, offset($sp) */
 264         return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 265                 ip->i_format.rs == 29 &&
 266                 ip->i_format.rt == 31;
 267 }
 268
 269 static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
 270 {
 271         if (ip->j_format.opcode == jal_op)
 272                 return 1;
 273         if (ip->r_format.opcode != spec_op)
 274                 return 0;
 275         return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 276 }
 277
 278 static inline int is_sp_move_ins(union mips_instruction *ip)
 279 {
 280         /* addiu/daddiu sp,sp,-imm */
 281         if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 282                 return 0;
 283         if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 284                 return 1;
 285         return 0;
 286 }
 287
 288 static int get_frame_info(struct mips_frame_info *info)
 289 {
 290         union mips_instruction *ip = info->func;
 291         unsigned max_insns = info->func_size / sizeof(union mips_instruction);
 292         unsigned i;
 293
 294         info->pc_offset = -1;
 295         info->frame_size = 0;
 296
 297         if (!ip)
 298                 goto err;
 299
 300         if (max_insns == 0)
 301                 max_insns = 128U;       /* unknown function size */
 302         max_insns = min(128U, max_insns);
 303
 304         for (i = 0; i < max_insns; i++, ip++) {
 305
 306                 if (is_jal_jalr_jr_ins(ip))
 307                         break;
 308                 if (!info->frame_size) {
 309                         if (is_sp_move_ins(ip))
 310                                 info->frame_size = - ip->i_format.simmediate;
 311                         continue;
 312                 }
 313                 if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
 314                         info->pc_offset =
 315                                 ip->i_format.simmediate / sizeof(long);
 316                         break;
 317                 }
 318         }
 319         if (info->frame_size && info->pc_offset >= 0) /* nested */
 320                 return 0;
 321         if (info->pc_offset < 0) /* leaf */
 322                 return 1;
 323         /* prologue seems boggus... */
 324 err:
 325         return -1;
 326 }
 327
 328 static struct mips_frame_info schedule_mfi __read_mostly;
 329
 330 static int __init frame_info_init(void)
 331 {
 332         unsigned long size = 0;
 333 #ifdef CONFIG_KALLSYMS
 334         unsigned long ofs;
 335
 336         kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
 337 #endif
 338         schedule_mfi.func = schedule;
 339         schedule_mfi.func_size = size;
 340
 341         get_frame_info(&schedule_mfi);
 342
 343         /*
 344          * Without schedule() frame info, result given by
 345          * thread_saved_pc() and get_wchan() are not reliable.
 346          */
 347         if (schedule_mfi.pc_offset < 0)
 348                 printk("Can't analyze schedule() prologue at %p\n", schedule);
 349
 350         return 0;
 351 }
 352
 353 arch_initcall(frame_info_init);
 354
 355 /*
 356  * Return saved PC of a blocked thread.
 357  */
 358 unsigned long thread_saved_pc(struct task_struct *tsk)
 359 {
 360         struct thread_struct *t = &tsk->thread;
 361
 362         /* New born processes are a special case */
 363         if (t->reg31 == (unsigned long) ret_from_fork)
 364                 return t->reg31;
 365         if (schedule_mfi.pc_offset < 0)
 366                 return 0;
 367         return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 368 }
 369
 370
 371 #ifdef CONFIG_KALLSYMS
 372 /* generic stack unwinding function */
 373 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
 374                                               unsigned long *sp,
 375                                               unsigned long pc,
 376                                               unsigned long *ra)
 377 {
 378         struct mips_frame_info info;
 379         unsigned long size, ofs;
 380         int leaf;
 381         extern void ret_from_irq(void);
 382         extern void ret_from_exception(void);
 383
 384         if (!stack_page)
 385                 return 0;
 386
 387         /*
 388          * If we reached the bottom of interrupt context,
 389          * return saved pc in pt_regs.
 390          */
 391         if (pc == (unsigned long)ret_from_irq ||
 392             pc == (unsigned long)ret_from_exception) {
 393                 struct pt_regs *regs;
 394                 if (*sp >= stack_page &&
 395                     *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
 396                         regs = (struct pt_regs *)*sp;
 397                         pc = regs->cp0_epc;
 398                         if (__kernel_text_address(pc)) {
 399                                 *sp = regs->regs[29];
 400                                 *ra = regs->regs[31];
 401                                 return pc;
 402                         }
 403                 }
 404                 return 0;
 405         }
 406         if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 407                 return 0;
 408         /*
 409          * Return ra if an exception occurred at the first instruction
 410          */
 411         if (unlikely(ofs == 0)) {
 412                 pc = *ra;
 413                 *ra = 0;
 414                 return pc;
 415         }
 416
 417         info.func = (void *)(pc - ofs);
 418         info.func_size = ofs;   /* analyze from start to ofs */
 419         leaf = get_frame_info(&info);
 420         if (leaf < 0)
 421                 return 0;
 422
 423         if (*sp < stack_page ||
 424             *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
 425                 return 0;
 426
 427         if (leaf)
 428                 /*
 429                  * For some extreme cases, get_frame_info() can
 430                  * consider wrongly a nested function as a leaf
 431                  * one. In that cases avoid to return always the
 432                  * same value.
 433                  */
 434                 pc = pc != *ra ? *ra : 0;
 435         else
 436                 pc = ((unsigned long *)(*sp))[info.pc_offset];
 437
 438         *sp += info.frame_size;
 439         *ra = 0;
 440         return __kernel_text_address(pc) ? pc : 0;
 441 }
 442 EXPORT_SYMBOL(unwind_stack_by_address);
 443
 444 /* used by show_backtrace() */
 445 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 446                            unsigned long pc, unsigned long *ra)
 447 {
 448         unsigned long stack_page = (unsigned long)task_stack_page(task);
 449         return unwind_stack_by_address(stack_page, sp, pc, ra);
 450 }
 451 #endif
 452
 453 /*
 454  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 455  */
 456 unsigned long get_wchan(struct task_struct *task)
 457 {
 458         unsigned long pc = 0;
 459 #ifdef CONFIG_KALLSYMS
 460         unsigned long sp;
 461         unsigned long ra = 0;
 462 #endif
 463
 464         if (!task || task == current || task->state == TASK_RUNNING)
 465                 goto out;
 466         if (!task_stack_page(task))
 467                 goto out;
 468
 469         pc = thread_saved_pc(task);
 470
 471 #ifdef CONFIG_KALLSYMS
 472         sp = task->thread.reg29 + schedule_mfi.frame_size;
 473
 474         while (in_sched_functions(pc))
 475                 pc = unwind_stack(task, &sp, pc, &ra);
 476 #endif
 477
 478 out:
 479         return pc;
 480 }
 481
 482 /*
 483  * Don't forget that the stack pointer must be aligned on a 8 bytes
 484  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 485  */
 486 unsigned long arch_align_stack(unsigned long sp)
 487 {
 488         if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 489                 sp -= get_random_int() & ~PAGE_MASK;
 490
 491         return sp & ALMASK;
 492 }