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                     (system_state == SYSTEM_RUNNING ||
  77                      system_state == SYSTEM_BOOTING))
  78                         play_dead();
  79 #endif
  80                 rcu_idle_exit();
  81                 tick_nohz_idle_exit();
  82                 schedule_preempt_disabled();
  83         }
  84 }
  85
  86 asmlinkage void ret_from_fork(void);
  87 asmlinkage void ret_from_kernel_thread(void);
  88
  89 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
  90 {
  91         unsigned long status;
  92
  93         /* New thread loses kernel privileges. */
  94         status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
  95 #ifdef CONFIG_64BIT
  96         status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
  97 #endif
  98         status |= KU_USER;
  99         regs->cp0_status = status;
 100         clear_used_math();
 101         clear_fpu_owner();
 102         if (cpu_has_dsp)
 103                 __init_dsp();
 104         regs->cp0_epc = pc;
 105         regs->regs[29] = sp;
 106 }
 107
 108 void exit_thread(void)
 109 {
 110 }
 111
 112 void flush_thread(void)
 113 {
 114 }
 115
 116 int copy_thread(unsigned long clone_flags, unsigned long usp,
 117         unsigned long 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         preempt_disable();
 127
 128         if (is_fpu_owner())
 129                 save_fp(p);
 130
 131         if (cpu_has_dsp)
 132                 save_dsp(p);
 133
 134         preempt_enable();
 135
 136         /* set up new TSS. */
 137         childregs = (struct pt_regs *) childksp - 1;
 138         /*  Put the stack after the struct pt_regs.  */
 139         childksp = (unsigned long) childregs;
 140         p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
 141         if (unlikely(p->flags & PF_KTHREAD)) {
 142                 unsigned long status = p->thread.cp0_status;
 143                 memset(childregs, 0, sizeof(struct pt_regs));
 144                 ti->addr_limit = KERNEL_DS;
 145                 p->thread.reg16 = usp; /* fn */
 146                 p->thread.reg17 = arg;
 147                 p->thread.reg29 = childksp;
 148                 p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
 149 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 150                 status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
 151                          ((status & (ST0_KUC | ST0_IEC)) << 2);
 152 #else
 153                 status |= ST0_EXL;
 154 #endif
 155                 childregs->cp0_status = status;
 156                 return 0;
 157         }
 158         *childregs = *regs;
 159         childregs->regs[7] = 0; /* Clear error flag */
 160         childregs->regs[2] = 0; /* Child gets zero as return value */
 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         /* sw / sd $ra, offset($sp) */
 248         return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 249                 ip->i_format.rs == 29 &&
 250                 ip->i_format.rt == 31;
 251 }
 252
 253 static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
 254 {
 255         if (ip->j_format.opcode == jal_op)
 256                 return 1;
 257         if (ip->r_format.opcode != spec_op)
 258                 return 0;
 259         return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 260 }
 261
 262 static inline int is_sp_move_ins(union mips_instruction *ip)
 263 {
 264         /* addiu/daddiu sp,sp,-imm */
 265         if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 266                 return 0;
 267         if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 268                 return 1;
 269         return 0;
 270 }
 271
 272 static int get_frame_info(struct mips_frame_info *info)
 273 {
 274         union mips_instruction *ip = info->func;
 275         unsigned max_insns = info->func_size / sizeof(union mips_instruction);
 276         unsigned i;
 277
 278         info->pc_offset = -1;
 279         info->frame_size = 0;
 280
 281         if (!ip)
 282                 goto err;
 283
 284         if (max_insns == 0)
 285                 max_insns = 128U;       /* unknown function size */
 286         max_insns = min(128U, max_insns);
 287
 288         for (i = 0; i < max_insns; i++, ip++) {
 289
 290                 if (is_jal_jalr_jr_ins(ip))
 291                         break;
 292                 if (!info->frame_size) {
 293                         if (is_sp_move_ins(ip))
 294                                 info->frame_size = - ip->i_format.simmediate;
 295                         continue;
 296                 }
 297                 if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
 298                         info->pc_offset =
 299                                 ip->i_format.simmediate / sizeof(long);
 300                         break;
 301                 }
 302         }
 303         if (info->frame_size && info->pc_offset >= 0) /* nested */
 304                 return 0;
 305         if (info->pc_offset < 0) /* leaf */
 306                 return 1;
 307         /* prologue seems boggus... */
 308 err:
 309         return -1;
 310 }
 311
 312 static struct mips_frame_info schedule_mfi __read_mostly;
 313
 314 static int __init frame_info_init(void)
 315 {
 316         unsigned long size = 0;
 317 #ifdef CONFIG_KALLSYMS
 318         unsigned long ofs;
 319
 320         kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
 321 #endif
 322         schedule_mfi.func = schedule;
 323         schedule_mfi.func_size = size;
 324
 325         get_frame_info(&schedule_mfi);
 326
 327         /*
 328          * Without schedule() frame info, result given by
 329          * thread_saved_pc() and get_wchan() are not reliable.
 330          */
 331         if (schedule_mfi.pc_offset < 0)
 332                 printk("Can't analyze schedule() prologue at %p\n", schedule);
 333
 334         return 0;
 335 }
 336
 337 arch_initcall(frame_info_init);
 338
 339 /*
 340  * Return saved PC of a blocked thread.
 341  */
 342 unsigned long thread_saved_pc(struct task_struct *tsk)
 343 {
 344         struct thread_struct *t = &tsk->thread;
 345
 346         /* New born processes are a special case */
 347         if (t->reg31 == (unsigned long) ret_from_fork)
 348                 return t->reg31;
 349         if (schedule_mfi.pc_offset < 0)
 350                 return 0;
 351         return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 352 }
 353
 354
 355 #ifdef CONFIG_KALLSYMS
 356 /* generic stack unwinding function */
 357 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
 358                                               unsigned long *sp,
 359                                               unsigned long pc,
 360                                               unsigned long *ra)
 361 {
 362         struct mips_frame_info info;
 363         unsigned long size, ofs;
 364         int leaf;
 365         extern void ret_from_irq(void);
 366         extern void ret_from_exception(void);
 367
 368         if (!stack_page)
 369                 return 0;
 370
 371         /*
 372          * If we reached the bottom of interrupt context,
 373          * return saved pc in pt_regs.
 374          */
 375         if (pc == (unsigned long)ret_from_irq ||
 376             pc == (unsigned long)ret_from_exception) {
 377                 struct pt_regs *regs;
 378                 if (*sp >= stack_page &&
 379                     *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
 380                         regs = (struct pt_regs *)*sp;
 381                         pc = regs->cp0_epc;
 382                         if (__kernel_text_address(pc)) {
 383                                 *sp = regs->regs[29];
 384                                 *ra = regs->regs[31];
 385                                 return pc;
 386                         }
 387                 }
 388                 return 0;
 389         }
 390         if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 391                 return 0;
 392         /*
 393          * Return ra if an exception occurred at the first instruction
 394          */
 395         if (unlikely(ofs == 0)) {
 396                 pc = *ra;
 397                 *ra = 0;
 398                 return pc;
 399         }
 400
 401         info.func = (void *)(pc - ofs);
 402         info.func_size = ofs;   /* analyze from start to ofs */
 403         leaf = get_frame_info(&info);
 404         if (leaf < 0)
 405                 return 0;
 406
 407         if (*sp < stack_page ||
 408             *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
 409                 return 0;
 410
 411         if (leaf)
 412                 /*
 413                  * For some extreme cases, get_frame_info() can
 414                  * consider wrongly a nested function as a leaf
 415                  * one. In that cases avoid to return always the
 416                  * same value.
 417                  */
 418                 pc = pc != *ra ? *ra : 0;
 419         else
 420                 pc = ((unsigned long *)(*sp))[info.pc_offset];
 421
 422         *sp += info.frame_size;
 423         *ra = 0;
 424         return __kernel_text_address(pc) ? pc : 0;
 425 }
 426 EXPORT_SYMBOL(unwind_stack_by_address);
 427
 428 /* used by show_backtrace() */
 429 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 430                            unsigned long pc, unsigned long *ra)
 431 {
 432         unsigned long stack_page = (unsigned long)task_stack_page(task);
 433         return unwind_stack_by_address(stack_page, sp, pc, ra);
 434 }
 435 #endif
 436
 437 /*
 438  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 439  */
 440 unsigned long get_wchan(struct task_struct *task)
 441 {
 442         unsigned long pc = 0;
 443 #ifdef CONFIG_KALLSYMS
 444         unsigned long sp;
 445         unsigned long ra = 0;
 446 #endif
 447
 448         if (!task || task == current || task->state == TASK_RUNNING)
 449                 goto out;
 450         if (!task_stack_page(task))
 451                 goto out;
 452
 453         pc = thread_saved_pc(task);
 454
 455 #ifdef CONFIG_KALLSYMS
 456         sp = task->thread.reg29 + schedule_mfi.frame_size;
 457
 458         while (in_sched_functions(pc))
 459                 pc = unwind_stack(task, &sp, pc, &ra);
 460 #endif
 461
 462 out:
 463         return pc;
 464 }
 465
 466 /*
 467  * Don't forget that the stack pointer must be aligned on a 8 bytes
 468  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 469  */
 470 unsigned long arch_align_stack(unsigned long sp)
 471 {
 472         if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 473                 sp -= get_random_int() & ~PAGE_MASK;
 474
 475         return sp & ALMASK;
 476 }