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 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
  81 {
  82         /*
  83          * Save any process state which is live in hardware registers to the
  84          * parent context prior to duplication. This prevents the new child
  85          * state becoming stale if the parent is preempted before copy_thread()
  86          * gets a chance to save the parent's live hardware registers to the
  87          * child context.
  88          */
  89         preempt_disable();
  90
  91         if (is_msa_enabled())
  92                 save_msa(current);
  93         else if (is_fpu_owner())
  94                 _save_fp(current);
  95
  96         save_dsp(current);
  97
  98         preempt_enable();
  99
 100         *dst = *src;
 101         return 0;
 102 }
 103
 104 /*
 105  * Copy architecture-specific thread state
 106  */
 107 int copy_thread(unsigned long clone_flags, unsigned long usp,
 108         unsigned long kthread_arg, struct task_struct *p)
 109 {
 110         struct thread_info *ti = task_thread_info(p);
 111         struct pt_regs *childregs, *regs = current_pt_regs();
 112         unsigned long childksp;
 113         p->set_child_tid = p->clear_child_tid = NULL;
 114
 115         childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
 116
 117         /* set up new TSS. */
 118         childregs = (struct pt_regs *) childksp - 1;
 119         /*  Put the stack after the struct pt_regs.  */
 120         childksp = (unsigned long) childregs;
 121         p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
 122         if (unlikely(p->flags & PF_KTHREAD)) {
 123                 /* kernel thread */
 124                 unsigned long status = p->thread.cp0_status;
 125                 memset(childregs, 0, sizeof(struct pt_regs));
 126                 ti->addr_limit = KERNEL_DS;
 127                 p->thread.reg16 = usp; /* fn */
 128                 p->thread.reg17 = kthread_arg;
 129                 p->thread.reg29 = childksp;
 130                 p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
 131 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 132                 status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
 133                          ((status & (ST0_KUC | ST0_IEC)) << 2);
 134 #else
 135                 status |= ST0_EXL;
 136 #endif
 137                 childregs->cp0_status = status;
 138                 return 0;
 139         }
 140
 141         /* user thread */
 142         *childregs = *regs;
 143         childregs->regs[7] = 0; /* Clear error flag */
 144         childregs->regs[2] = 0; /* Child gets zero as return value */
 145         if (usp)
 146                 childregs->regs[29] = usp;
 147         ti->addr_limit = USER_DS;
 148
 149         p->thread.reg29 = (unsigned long) childregs;
 150         p->thread.reg31 = (unsigned long) ret_from_fork;
 151
 152         /*
 153          * New tasks lose permission to use the fpu. This accelerates context
 154          * switching for most programs since they don't use the fpu.
 155          */
 156         childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
 157
 158         clear_tsk_thread_flag(p, TIF_USEDFPU);
 159         clear_tsk_thread_flag(p, TIF_USEDMSA);
 160         clear_tsk_thread_flag(p, TIF_MSA_CTX_LIVE);
 161
 162 #ifdef CONFIG_MIPS_MT_FPAFF
 163         clear_tsk_thread_flag(p, TIF_FPUBOUND);
 164 #endif /* CONFIG_MIPS_MT_FPAFF */
 165
 166         if (clone_flags & CLONE_SETTLS)
 167                 ti->tp_value = regs->regs[7];
 168
 169         return 0;
 170 }
 171
 172 #ifdef CONFIG_CC_STACKPROTECTOR
 173 #include <linux/stackprotector.h>
 174 unsigned long __stack_chk_guard __read_mostly;
 175 EXPORT_SYMBOL(__stack_chk_guard);
 176 #endif
 177
 178 struct mips_frame_info {
 179         void            *func;
 180         unsigned long   func_size;
 181         int             frame_size;
 182         int             pc_offset;
 183 };
 184
 185 #define J_TARGET(pc,target)     \
 186                 (((unsigned long)(pc) & 0xf0000000) | ((target) << 2))
 187
 188 static inline int is_ra_save_ins(union mips_instruction *ip)
 189 {
 190 #ifdef CONFIG_CPU_MICROMIPS
 191         union mips_instruction mmi;
 192
 193         /*
 194          * swsp ra,offset
 195          * swm16 reglist,offset(sp)
 196          * swm32 reglist,offset(sp)
 197          * sw32 ra,offset(sp)
 198          * jradiussp - NOT SUPPORTED
 199          *
 200          * microMIPS is way more fun...
 201          */
 202         if (mm_insn_16bit(ip->halfword[0])) {
 203                 mmi.word = (ip->halfword[0] << 16);
 204                 return (mmi.mm16_r5_format.opcode == mm_swsp16_op &&
 205                         mmi.mm16_r5_format.rt == 31) ||
 206                        (mmi.mm16_m_format.opcode == mm_pool16c_op &&
 207                         mmi.mm16_m_format.func == mm_swm16_op);
 208         }
 209         else {
 210                 mmi.halfword[0] = ip->halfword[1];
 211                 mmi.halfword[1] = ip->halfword[0];
 212                 return (mmi.mm_m_format.opcode == mm_pool32b_op &&
 213                         mmi.mm_m_format.rd > 9 &&
 214                         mmi.mm_m_format.base == 29 &&
 215                         mmi.mm_m_format.func == mm_swm32_func) ||
 216                        (mmi.i_format.opcode == mm_sw32_op &&
 217                         mmi.i_format.rs == 29 &&
 218                         mmi.i_format.rt == 31);
 219         }
 220 #else
 221         /* sw / sd $ra, offset($sp) */
 222         return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 223                 ip->i_format.rs == 29 &&
 224                 ip->i_format.rt == 31;
 225 #endif
 226 }
 227
 228 static inline int is_jump_ins(union mips_instruction *ip)
 229 {
 230 #ifdef CONFIG_CPU_MICROMIPS
 231         /*
 232          * jr16,jrc,jalr16,jalr16
 233          * jal
 234          * jalr/jr,jalr.hb/jr.hb,jalrs,jalrs.hb
 235          * jraddiusp - NOT SUPPORTED
 236          *
 237          * microMIPS is kind of more fun...
 238          */
 239         union mips_instruction mmi;
 240
 241         mmi.word = (ip->halfword[0] << 16);
 242
 243         if ((mmi.mm16_r5_format.opcode == mm_pool16c_op &&
 244             (mmi.mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op) ||
 245             ip->j_format.opcode == mm_jal32_op)
 246                 return 1;
 247         if (ip->r_format.opcode != mm_pool32a_op ||
 248                         ip->r_format.func != mm_pool32axf_op)
 249                 return 0;
 250         return ((ip->u_format.uimmediate >> 6) & mm_jalr_op) == mm_jalr_op;
 251 #else
 252         if (ip->j_format.opcode == j_op)
 253                 return 1;
 254         if (ip->j_format.opcode == jal_op)
 255                 return 1;
 256         if (ip->r_format.opcode != spec_op)
 257                 return 0;
 258         return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 259 #endif
 260 }
 261
 262 static inline int is_sp_move_ins(union mips_instruction *ip)
 263 {
 264 #ifdef CONFIG_CPU_MICROMIPS
 265         /*
 266          * addiusp -imm
 267          * addius5 sp,-imm
 268          * addiu32 sp,sp,-imm
 269          * jradiussp - NOT SUPPORTED
 270          *
 271          * microMIPS is not more fun...
 272          */
 273         if (mm_insn_16bit(ip->halfword[0])) {
 274                 union mips_instruction mmi;
 275
 276                 mmi.word = (ip->halfword[0] << 16);
 277                 return (mmi.mm16_r3_format.opcode == mm_pool16d_op &&
 278                         mmi.mm16_r3_format.simmediate && mm_addiusp_func) ||
 279                        (mmi.mm16_r5_format.opcode == mm_pool16d_op &&
 280                         mmi.mm16_r5_format.rt == 29);
 281         }
 282         return ip->mm_i_format.opcode == mm_addiu32_op &&
 283                ip->mm_i_format.rt == 29 && ip->mm_i_format.rs == 29;
 284 #else
 285         /* addiu/daddiu sp,sp,-imm */
 286         if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 287                 return 0;
 288         if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 289                 return 1;
 290 #endif
 291         return 0;
 292 }
 293
 294 static int get_frame_info(struct mips_frame_info *info)
 295 {
 296 #ifdef CONFIG_CPU_MICROMIPS
 297         union mips_instruction *ip = (void *) (((char *) info->func) - 1);
 298 #else
 299         union mips_instruction *ip = info->func;
 300 #endif
 301         unsigned max_insns = info->func_size / sizeof(union mips_instruction);
 302         unsigned i;
 303
 304         info->pc_offset = -1;
 305         info->frame_size = 0;
 306
 307         if (!ip)
 308                 goto err;
 309
 310         if (max_insns == 0)
 311                 max_insns = 128U;       /* unknown function size */
 312         max_insns = min(128U, max_insns);
 313
 314         for (i = 0; i < max_insns; i++, ip++) {
 315
 316                 if (is_jump_ins(ip))
 317                         break;
 318                 if (!info->frame_size) {
 319                         if (is_sp_move_ins(ip))
 320                         {
 321 #ifdef CONFIG_CPU_MICROMIPS
 322                                 if (mm_insn_16bit(ip->halfword[0]))
 323                                 {
 324                                         unsigned short tmp;
 325
 326                                         if (ip->halfword[0] & mm_addiusp_func)
 327                                         {
 328                                                 tmp = (((ip->halfword[0] >> 1) & 0x1ff) << 2);
 329                                                 info->frame_size = -(signed short)(tmp | ((tmp & 0x100) ? 0xfe00 : 0));
 330                                         } else {
 331                                                 tmp = (ip->halfword[0] >> 1);
 332                                                 info->frame_size = -(signed short)(tmp & 0xf);
 333                                         }
 334                                         ip = (void *) &ip->halfword[1];
 335                                         ip--;
 336                                 } else
 337 #endif
 338                                 info->frame_size = - ip->i_format.simmediate;
 339                         }
 340                         continue;
 341                 }
 342                 if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
 343                         info->pc_offset =
 344                                 ip->i_format.simmediate / sizeof(long);
 345                         break;
 346                 }
 347         }
 348         if (info->frame_size && info->pc_offset >= 0) /* nested */
 349                 return 0;
 350         if (info->pc_offset < 0) /* leaf */
 351                 return 1;
 352         /* prologue seems boggus... */
 353 err:
 354         return -1;
 355 }
 356
 357 static struct mips_frame_info schedule_mfi __read_mostly;
 358
 359 #ifdef CONFIG_KALLSYMS
 360 static unsigned long get___schedule_addr(void)
 361 {
 362         return kallsyms_lookup_name("__schedule");
 363 }
 364 #else
 365 static unsigned long get___schedule_addr(void)
 366 {
 367         union mips_instruction *ip = (void *)schedule;
 368         int max_insns = 8;
 369         int i;
 370
 371         for (i = 0; i < max_insns; i++, ip++) {
 372                 if (ip->j_format.opcode == j_op)
 373                         return J_TARGET(ip, ip->j_format.target);
 374         }
 375         return 0;
 376 }
 377 #endif
 378
 379 static int __init frame_info_init(void)
 380 {
 381         unsigned long size = 0;
 382 #ifdef CONFIG_KALLSYMS
 383         unsigned long ofs;
 384 #endif
 385         unsigned long addr;
 386
 387         addr = get___schedule_addr();
 388         if (!addr)
 389                 addr = (unsigned long)schedule;
 390
 391 #ifdef CONFIG_KALLSYMS
 392         kallsyms_lookup_size_offset(addr, &size, &ofs);
 393 #endif
 394         schedule_mfi.func = (void *)addr;
 395         schedule_mfi.func_size = size;
 396
 397         get_frame_info(&schedule_mfi);
 398
 399         /*
 400          * Without schedule() frame info, result given by
 401          * thread_saved_pc() and get_wchan() are not reliable.
 402          */
 403         if (schedule_mfi.pc_offset < 0)
 404                 printk("Can't analyze schedule() prologue at %p\n", schedule);
 405
 406         return 0;
 407 }
 408
 409 arch_initcall(frame_info_init);
 410
 411 /*
 412  * Return saved PC of a blocked thread.
 413  */
 414 unsigned long thread_saved_pc(struct task_struct *tsk)
 415 {
 416         struct thread_struct *t = &tsk->thread;
 417
 418         /* New born processes are a special case */
 419         if (t->reg31 == (unsigned long) ret_from_fork)
 420                 return t->reg31;
 421         if (schedule_mfi.pc_offset < 0)
 422                 return 0;
 423         return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 424 }
 425
 426
 427 #ifdef CONFIG_KALLSYMS
 428 /* generic stack unwinding function */
 429 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
 430                                               unsigned long *sp,
 431                                               unsigned long pc,
 432                                               unsigned long *ra)
 433 {
 434         struct mips_frame_info info;
 435         unsigned long size, ofs;
 436         int leaf;
 437         extern void ret_from_irq(void);
 438         extern void ret_from_exception(void);
 439
 440         if (!stack_page)
 441                 return 0;
 442
 443         /*
 444          * If we reached the bottom of interrupt context,
 445          * return saved pc in pt_regs.
 446          */
 447         if (pc == (unsigned long)ret_from_irq ||
 448             pc == (unsigned long)ret_from_exception) {
 449                 struct pt_regs *regs;
 450                 if (*sp >= stack_page &&
 451                     *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
 452                         regs = (struct pt_regs *)*sp;
 453                         pc = regs->cp0_epc;
 454                         if (!user_mode(regs) && __kernel_text_address(pc)) {
 455                                 *sp = regs->regs[29];
 456                                 *ra = regs->regs[31];
 457                                 return pc;
 458                         }
 459                 }
 460                 return 0;
 461         }
 462         if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 463                 return 0;
 464         /*
 465          * Return ra if an exception occurred at the first instruction
 466          */
 467         if (unlikely(ofs == 0)) {
 468                 pc = *ra;
 469                 *ra = 0;
 470                 return pc;
 471         }
 472
 473         info.func = (void *)(pc - ofs);
 474         info.func_size = ofs;   /* analyze from start to ofs */
 475         leaf = get_frame_info(&info);
 476         if (leaf < 0)
 477                 return 0;
 478
 479         if (*sp < stack_page ||
 480             *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
 481                 return 0;
 482
 483         if (leaf)
 484                 /*
 485                  * For some extreme cases, get_frame_info() can
 486                  * consider wrongly a nested function as a leaf
 487                  * one. In that cases avoid to return always the
 488                  * same value.
 489                  */
 490                 pc = pc != *ra ? *ra : 0;
 491         else
 492                 pc = ((unsigned long *)(*sp))[info.pc_offset];
 493
 494         *sp += info.frame_size;
 495         *ra = 0;
 496         return __kernel_text_address(pc) ? pc : 0;
 497 }
 498 EXPORT_SYMBOL(unwind_stack_by_address);
 499
 500 /* used by show_backtrace() */
 501 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 502                            unsigned long pc, unsigned long *ra)
 503 {
 504         unsigned long stack_page = (unsigned long)task_stack_page(task);
 505         return unwind_stack_by_address(stack_page, sp, pc, ra);
 506 }
 507 #endif
 508
 509 /*
 510  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 511  */
 512 unsigned long get_wchan(struct task_struct *task)
 513 {
 514         unsigned long pc = 0;
 515 #ifdef CONFIG_KALLSYMS
 516         unsigned long sp;
 517         unsigned long ra = 0;
 518 #endif
 519
 520         if (!task || task == current || task->state == TASK_RUNNING)
 521                 goto out;
 522         if (!task_stack_page(task))
 523                 goto out;
 524
 525         pc = thread_saved_pc(task);
 526
 527 #ifdef CONFIG_KALLSYMS
 528         sp = task->thread.reg29 + schedule_mfi.frame_size;
 529
 530         while (in_sched_functions(pc))
 531                 pc = unwind_stack(task, &sp, pc, &ra);
 532 #endif
 533
 534 out:
 535         return pc;
 536 }
 537
 538 /*
 539  * Don't forget that the stack pointer must be aligned on a 8 bytes
 540  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 541  */
 542 unsigned long arch_align_stack(unsigned long sp)
 543 {
 544         if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 545                 sp -= get_random_int() & ~PAGE_MASK;
 546
 547         return sp & ALMASK;
 548 }
 549
 550 static void arch_dump_stack(void *info)
 551 {
 552         struct pt_regs *regs;
 553
 554         regs = get_irq_regs();
 555
 556         if (regs)
 557                 show_regs(regs);
 558
 559         dump_stack();
 560 }
 561
 562 void arch_trigger_all_cpu_backtrace(bool include_self)
 563 {
 564         smp_call_function(arch_dump_stack, NULL, 1);
 565 }
 566
 567 int mips_get_process_fp_mode(struct task_struct *task)
 568 {
 569         int value = 0;
 570
 571         if (!test_tsk_thread_flag(task, TIF_32BIT_FPREGS))
 572                 value |= PR_FP_MODE_FR;
 573         if (test_tsk_thread_flag(task, TIF_HYBRID_FPREGS))
 574                 value |= PR_FP_MODE_FRE;
 575
 576         return value;
 577 }
 578
 579 static void prepare_for_fp_mode_switch(void *info)
 580 {
 581         struct mm_struct *mm = info;
 582
 583         if (current->mm == mm)
 584                 lose_fpu(1);
 585 }
 586
 587 int mips_set_process_fp_mode(struct task_struct *task, unsigned int value)
 588 {
 589         const unsigned int known_bits = PR_FP_MODE_FR | PR_FP_MODE_FRE;
 590         struct task_struct *t;
 591         int max_users;
 592
 593         /* Check the value is valid */
 594         if (value & ~known_bits)
 595                 return -EOPNOTSUPP;
 596
 597         /* Avoid inadvertently triggering emulation */
 598         if ((value & PR_FP_MODE_FR) && cpu_has_fpu &&
 599             !(current_cpu_data.fpu_id & MIPS_FPIR_F64))
 600                 return -EOPNOTSUPP;
 601         if ((value & PR_FP_MODE_FRE) && cpu_has_fpu && !cpu_has_fre)
 602                 return -EOPNOTSUPP;
 603
 604         /* FR = 0 not supported in MIPS R6 */
 605         if (!(value & PR_FP_MODE_FR) && cpu_has_fpu && cpu_has_mips_r6)
 606                 return -EOPNOTSUPP;
 607
 608         /* Proceed with the mode switch */
 609         preempt_disable();
 610
 611         /* Save FP & vector context, then disable FPU & MSA */
 612         if (task->signal == current->signal)
 613                 lose_fpu(1);
 614
 615         /* Prevent any threads from obtaining live FP context */
 616         atomic_set(&task->mm->context.fp_mode_switching, 1);
 617         smp_mb__after_atomic();
 618
 619         /*
 620          * If there are multiple online CPUs then force any which are running
 621          * threads in this process to lose their FPU context, which they can't
 622          * regain until fp_mode_switching is cleared later.
 623          */
 624         if (num_online_cpus() > 1) {
 625                 /* No need to send an IPI for the local CPU */
 626                 max_users = (task->mm == current->mm) ? 1 : 0;
 627
 628                 if (atomic_read(&current->mm->mm_users) > max_users)
 629                         smp_call_function(prepare_for_fp_mode_switch,
 630                                           (void *)current->mm, 1);
 631         }
 632
 633         /*
 634          * There are now no threads of the process with live FP context, so it
 635          * is safe to proceed with the FP mode switch.
 636          */
 637         for_each_thread(task, t) {
 638                 /* Update desired FP register width */
 639                 if (value & PR_FP_MODE_FR) {
 640                         clear_tsk_thread_flag(t, TIF_32BIT_FPREGS);
 641                 } else {
 642                         set_tsk_thread_flag(t, TIF_32BIT_FPREGS);
 643                         clear_tsk_thread_flag(t, TIF_MSA_CTX_LIVE);
 644                 }
 645
 646                 /* Update desired FP single layout */
 647                 if (value & PR_FP_MODE_FRE)
 648                         set_tsk_thread_flag(t, TIF_HYBRID_FPREGS);
 649                 else
 650                         clear_tsk_thread_flag(t, TIF_HYBRID_FPREGS);
 651         }
 652
 653         /* Allow threads to use FP again */
 654         atomic_set(&task->mm->context.fp_mode_switching, 0);
 655         preempt_enable();
 656
 657         return 0;
 658 }