arch/m32r/kernel/ptrace.c

   1 /*
   2  * linux/arch/m32r/kernel/ptrace.c
   3  *
   4  * Copyright (C) 2002  Hirokazu Takata, Takeo Takahashi
   5  * Copyright (C) 2004  Hirokazu Takata, Kei Sakamoto
   6  *
   7  * Original x86 implementation:
   8  *      By Ross Biro 1/23/92
   9  *      edited by Linus Torvalds
  10  *
  11  * Some code taken from sh version:
  12  *   Copyright (C) 1999, 2000  Kaz Kojima & Niibe Yutaka
  13  * Some code taken from arm version:
  14  *   Copyright (C) 2000 Russell King
  15  */
  16
  17 #include <linux/config.h>
  18 #include <linux/kernel.h>
  19 #include <linux/sched.h>
  20 #include <linux/mm.h>
  21 #include <linux/smp.h>
  22 #include <linux/smp_lock.h>
  23 #include <linux/errno.h>
  24 #include <linux/ptrace.h>
  25 #include <linux/user.h>
  26 #include <linux/string.h>
  27
  28 #include <asm/cacheflush.h>
  29 #include <asm/io.h>
  30 #include <asm/uaccess.h>
  31 #include <asm/pgtable.h>
  32 #include <asm/system.h>
  33 #include <asm/processor.h>
  34 #include <asm/mmu_context.h>
  35
  36 /*
  37  * Get the address of the live pt_regs for the specified task.
  38  * These are saved onto the top kernel stack when the process
  39  * is not running.
  40  *
  41  * Note: if a user thread is execve'd from kernel space, the
  42  * kernel stack will not be empty on entry to the kernel, so
  43  * ptracing these tasks will fail.
  44  */
  45 static inline struct pt_regs *
  46 get_user_regs(struct task_struct *task)
  47 {
  48         return (struct pt_regs *)
  49                 ((unsigned long)task->thread_info + THREAD_SIZE
  50                  - sizeof(struct pt_regs));
  51 }
  52
  53 /*
  54  * This routine will get a word off of the process kernel stack.
  55  */
  56 static inline unsigned long int
  57 get_stack_long(struct task_struct *task, int offset)
  58 {
  59         unsigned long *stack;
  60
  61         stack = (unsigned long *)get_user_regs(task);
  62
  63         return stack[offset];
  64 }
  65
  66 /*
  67  * This routine will put a word on the process kernel stack.
  68  */
  69 static inline int
  70 put_stack_long(struct task_struct *task, int offset, unsigned long data)
  71 {
  72         unsigned long *stack;
  73
  74         stack = (unsigned long *)get_user_regs(task);
  75         stack[offset] = data;
  76
  77         return 0;
  78 }
  79
  80 static int reg_offset[] = {
  81         PT_R0, PT_R1, PT_R2, PT_R3, PT_R4, PT_R5, PT_R6, PT_R7,
  82         PT_R8, PT_R9, PT_R10, PT_R11, PT_R12, PT_FP, PT_LR, PT_SPU,
  83 };
  84
  85 /*
  86  * Read the word at offset "off" into the "struct user".  We
  87  * actually access the pt_regs stored on the kernel stack.
  88  */
  89 static int ptrace_read_user(struct task_struct *tsk, unsigned long off,
  90                             unsigned long __user *data)
  91 {
  92         unsigned long tmp;
  93 #ifndef NO_FPU
  94         struct user * dummy = NULL;
  95 #endif
  96
  97         if ((off & 3) || (off < 0) || (off > sizeof(struct user) - 3))
  98                 return -EIO;
  99
 100         off >>= 2;
 101         switch (off) {
 102         case PT_EVB:
 103                 __asm__ __volatile__ (
 104                         "mvfc   %0, cr5 \n\t"
 105                         : "=r" (tmp)
 106                 );
 107                 break;
 108         case PT_CBR: {
 109                         unsigned long psw;
 110                         psw = get_stack_long(tsk, PT_PSW);
 111                         tmp = ((psw >> 8) & 1);
 112                 }
 113                 break;
 114         case PT_PSW: {
 115                         unsigned long psw, bbpsw;
 116                         psw = get_stack_long(tsk, PT_PSW);
 117                         bbpsw = get_stack_long(tsk, PT_BBPSW);
 118                         tmp = ((psw >> 8) & 0xff) | ((bbpsw & 0xff) << 8);
 119                 }
 120                 break;
 121         case PT_PC:
 122                 tmp = get_stack_long(tsk, PT_BPC);
 123                 break;
 124         case PT_BPC:
 125                 off = PT_BBPC;
 126                 /* fall through */
 127         default:
 128                 if (off < (sizeof(struct pt_regs) >> 2))
 129                         tmp = get_stack_long(tsk, off);
 130 #ifndef NO_FPU
 131                 else if (off >= (long)(&dummy->fpu >> 2) &&
 132                          off < (long)(&dummy->u_fpvalid >> 2)) {
 133                         if (!tsk_used_math(tsk)) {
 134                                 if (off == (long)(&dummy->fpu.fpscr >> 2))
 135                                         tmp = FPSCR_INIT;
 136                                 else
 137                                         tmp = 0;
 138                         } else
 139                                 tmp = ((long *)(&tsk->thread.fpu >> 2))
 140                                         [off - (long)&dummy->fpu];
 141                 } else if (off == (long)(&dummy->u_fpvalid >> 2))
 142                         tmp = !!tsk_used_math(tsk);
 143 #endif /* not NO_FPU */
 144                 else
 145                         tmp = 0;
 146         }
 147
 148         return put_user(tmp, data);
 149 }
 150
 151 static int ptrace_write_user(struct task_struct *tsk, unsigned long off,
 152                              unsigned long data)
 153 {
 154         int ret = -EIO;
 155 #ifndef NO_FPU
 156         struct user * dummy = NULL;
 157 #endif
 158
 159         if ((off & 3) || off < 0 ||
 160             off > sizeof(struct user) - 3)
 161                 return -EIO;
 162
 163         off >>= 2;
 164         switch (off) {
 165         case PT_EVB:
 166         case PT_BPC:
 167         case PT_SPI:
 168                 /* We don't allow to modify evb. */
 169                 ret = 0;
 170                 break;
 171         case PT_PSW:
 172         case PT_CBR: {
 173                         /* We allow to modify only cbr in psw */
 174                         unsigned long psw;
 175                         psw = get_stack_long(tsk, PT_PSW);
 176                         psw = (psw & ~0x100) | ((data & 1) << 8);
 177                         ret = put_stack_long(tsk, PT_PSW, psw);
 178                 }
 179                 break;
 180         case PT_PC:
 181                 off = PT_BPC;
 182                 data &= ~1;
 183                 /* fall through */
 184         default:
 185                 if (off < (sizeof(struct pt_regs) >> 2))
 186                         ret = put_stack_long(tsk, off, data);
 187 #ifndef NO_FPU
 188                 else if (off >= (long)(&dummy->fpu >> 2) &&
 189                          off < (long)(&dummy->u_fpvalid >> 2)) {
 190                         set_stopped_child_used_math(tsk);
 191                         ((long *)&tsk->thread.fpu)
 192                                 [off - (long)&dummy->fpu] = data;
 193                         ret = 0;
 194                 } else if (off == (long)(&dummy->u_fpvalid >> 2)) {
 195                         conditional_stopped_child_used_math(data, tsk);
 196                         ret = 0;
 197                 }
 198 #endif /* not NO_FPU */
 199                 break;
 200         }
 201
 202         return ret;
 203 }
 204
 205 /*
 206  * Get all user integer registers.
 207  */
 208 static int ptrace_getregs(struct task_struct *tsk, void __user *uregs)
 209 {
 210         struct pt_regs *regs = get_user_regs(tsk);
 211
 212         return copy_to_user(uregs, regs, sizeof(struct pt_regs)) ? -EFAULT : 0;
 213 }
 214
 215 /*
 216  * Set all user integer registers.
 217  */
 218 static int ptrace_setregs(struct task_struct *tsk, void __user *uregs)
 219 {
 220         struct pt_regs newregs;
 221         int ret;
 222
 223         ret = -EFAULT;
 224         if (copy_from_user(&newregs, uregs, sizeof(struct pt_regs)) == 0) {
 225                 struct pt_regs *regs = get_user_regs(tsk);
 226                 *regs = newregs;
 227                 ret = 0;
 228         }
 229
 230         return ret;
 231 }
 232
 233
 234 static inline int
 235 check_condition_bit(struct task_struct *child)
 236 {
 237         return (int)((get_stack_long(child, PT_PSW) >> 8) & 1);
 238 }
 239
 240 static int
 241 check_condition_src(unsigned long op, unsigned long regno1,
 242                     unsigned long regno2, struct task_struct *child)
 243 {
 244         unsigned long reg1, reg2;
 245
 246         reg2 = get_stack_long(child, reg_offset[regno2]);
 247
 248         switch (op) {
 249         case 0x0: /* BEQ */
 250                 reg1 = get_stack_long(child, reg_offset[regno1]);
 251                 return reg1 == reg2;
 252         case 0x1: /* BNE */
 253                 reg1 = get_stack_long(child, reg_offset[regno1]);
 254                 return reg1 != reg2;
 255         case 0x8: /* BEQZ */
 256                 return reg2 == 0;
 257         case 0x9: /* BNEZ */
 258                 return reg2 != 0;
 259         case 0xa: /* BLTZ */
 260                 return (int)reg2 < 0;
 261         case 0xb: /* BGEZ */
 262                 return (int)reg2 >= 0;
 263         case 0xc: /* BLEZ */
 264                 return (int)reg2 <= 0;
 265         case 0xd: /* BGTZ */
 266                 return (int)reg2 > 0;
 267         default:
 268                 /* never reached */
 269                 return 0;
 270         }
 271 }
 272
 273 static void
 274 compute_next_pc_for_16bit_insn(unsigned long insn, unsigned long pc,
 275                                unsigned long *next_pc,
 276                                struct task_struct *child)
 277 {
 278         unsigned long op, op2, op3;
 279         unsigned long disp;
 280         unsigned long regno;
 281         int parallel = 0;
 282
 283         if (insn & 0x00008000)
 284                 parallel = 1;
 285         if (pc & 3)
 286                 insn &= 0x7fff; /* right slot */
 287         else
 288                 insn >>= 16;    /* left slot */
 289
 290         op = (insn >> 12) & 0xf;
 291         op2 = (insn >> 8) & 0xf;
 292         op3 = (insn >> 4) & 0xf;
 293
 294         if (op == 0x7) {
 295                 switch (op2) {
 296                 case 0xd: /* BNC */
 297                 case 0x9: /* BNCL */
 298                         if (!check_condition_bit(child)) {
 299                                 disp = (long)(insn << 24) >> 22;
 300                                 *next_pc = (pc & ~0x3) + disp;
 301                                 return;
 302                         }
 303                         break;
 304                 case 0x8: /* BCL */
 305                 case 0xc: /* BC */
 306                         if (check_condition_bit(child)) {
 307                                 disp = (long)(insn << 24) >> 22;
 308                                 *next_pc = (pc & ~0x3) + disp;
 309                                 return;
 310                         }
 311                         break;
 312                 case 0xe: /* BL */
 313                 case 0xf: /* BRA */
 314                         disp = (long)(insn << 24) >> 22;
 315                         *next_pc = (pc & ~0x3) + disp;
 316                         return;
 317                         break;
 318                 }
 319         } else if (op == 0x1) {
 320                 switch (op2) {
 321                 case 0x0:
 322                         if (op3 == 0xf) { /* TRAP */
 323 #if 1
 324                                 /* pass through */
 325 #else
 326                                 /* kernel space is not allowed as next_pc */
 327                                 unsigned long evb;
 328                                 unsigned long trapno;
 329                                 trapno = insn & 0xf;
 330                                 __asm__ __volatile__ (
 331                                         "mvfc %0, cr5\n"
 332                                         :"=r"(evb)
 333                                         :
 334                                 );
 335                                 *next_pc = evb + (trapno << 2);
 336                                 return;
 337 #endif
 338                         } else if (op3 == 0xd) { /* RTE */
 339                                 *next_pc = get_stack_long(child, PT_BPC);
 340                                 return;
 341                         }
 342                         break;
 343                 case 0xc: /* JC */
 344                         if (op3 == 0xc && check_condition_bit(child)) {
 345                                 regno = insn & 0xf;
 346                                 *next_pc = get_stack_long(child,
 347                                                           reg_offset[regno]);
 348                                 return;
 349                         }
 350                         break;
 351                 case 0xd: /* JNC */
 352                         if (op3 == 0xc && !check_condition_bit(child)) {
 353                                 regno = insn & 0xf;
 354                                 *next_pc = get_stack_long(child,
 355                                                           reg_offset[regno]);
 356                                 return;
 357                         }
 358                         break;
 359                 case 0xe: /* JL */
 360                 case 0xf: /* JMP */
 361                         if (op3 == 0xc) { /* JMP */
 362                                 regno = insn & 0xf;
 363                                 *next_pc = get_stack_long(child,
 364                                                           reg_offset[regno]);
 365                                 return;
 366                         }
 367                         break;
 368                 }
 369         }
 370         if (parallel)
 371                 *next_pc = pc + 4;
 372         else
 373                 *next_pc = pc + 2;
 374 }
 375
 376 static void
 377 compute_next_pc_for_32bit_insn(unsigned long insn, unsigned long pc,
 378                                unsigned long *next_pc,
 379                                struct task_struct *child)
 380 {
 381         unsigned long op;
 382         unsigned long op2;
 383         unsigned long disp;
 384         unsigned long regno1, regno2;
 385
 386         op = (insn >> 28) & 0xf;
 387         if (op == 0xf) {        /* branch 24-bit relative */
 388                 op2 = (insn >> 24) & 0xf;
 389                 switch (op2) {
 390                 case 0xd:       /* BNC */
 391                 case 0x9:       /* BNCL */
 392                         if (!check_condition_bit(child)) {
 393                                 disp = (long)(insn << 8) >> 6;
 394                                 *next_pc = (pc & ~0x3) + disp;
 395                                 return;
 396                         }
 397                         break;
 398                 case 0x8:       /* BCL */
 399                 case 0xc:       /* BC */
 400                         if (check_condition_bit(child)) {
 401                                 disp = (long)(insn << 8) >> 6;
 402                                 *next_pc = (pc & ~0x3) + disp;
 403                                 return;
 404                         }
 405                         break;
 406                 case 0xe:       /* BL */
 407                 case 0xf:       /* BRA */
 408                         disp = (long)(insn << 8) >> 6;
 409                         *next_pc = (pc & ~0x3) + disp;
 410                         return;
 411                 }
 412         } else if (op == 0xb) { /* branch 16-bit relative */
 413                 op2 = (insn >> 20) & 0xf;
 414                 switch (op2) {
 415                 case 0x0: /* BEQ */
 416                 case 0x1: /* BNE */
 417                 case 0x8: /* BEQZ */
 418                 case 0x9: /* BNEZ */
 419                 case 0xa: /* BLTZ */
 420                 case 0xb: /* BGEZ */
 421                 case 0xc: /* BLEZ */
 422                 case 0xd: /* BGTZ */
 423                         regno1 = ((insn >> 24) & 0xf);
 424                         regno2 = ((insn >> 16) & 0xf);
 425                         if (check_condition_src(op2, regno1, regno2, child)) {
 426                                 disp = (long)(insn << 16) >> 14;
 427                                 *next_pc = (pc & ~0x3) + disp;
 428                                 return;
 429                         }
 430                         break;
 431                 }
 432         }
 433         *next_pc = pc + 4;
 434 }
 435
 436 static inline void
 437 compute_next_pc(unsigned long insn, unsigned long pc,
 438                 unsigned long *next_pc, struct task_struct *child)
 439 {
 440         if (insn & 0x80000000)
 441                 compute_next_pc_for_32bit_insn(insn, pc, next_pc, child);
 442         else
 443                 compute_next_pc_for_16bit_insn(insn, pc, next_pc, child);
 444 }
 445
 446 static int
 447 register_debug_trap(struct task_struct *child, unsigned long next_pc,
 448         unsigned long next_insn, unsigned long *code)
 449 {
 450         struct debug_trap *p = &child->thread.debug_trap;
 451         unsigned long addr = next_pc & ~3;
 452
 453         if (p->nr_trap == MAX_TRAPS) {
 454                 printk("kernel BUG at %s %d: p->nr_trap = %d\n",
 455                                         __FILE__, __LINE__, p->nr_trap);
 456                 return -1;
 457         }
 458         p->addr[p->nr_trap] = addr;
 459         p->insn[p->nr_trap] = next_insn;
 460         p->nr_trap++;
 461         if (next_pc & 3) {
 462                 *code = (next_insn & 0xffff0000) | 0x10f1;
 463                 /* xxx --> TRAP1 */
 464         } else {
 465                 if ((next_insn & 0x80000000) || (next_insn & 0x8000)) {
 466                         *code = 0x10f17000;
 467                         /* TRAP1 --> NOP */
 468                 } else {
 469                         *code = (next_insn & 0xffff) | 0x10f10000;
 470                         /* TRAP1 --> xxx */
 471                 }
 472         }
 473         return 0;
 474 }
 475
 476 static int
 477 unregister_debug_trap(struct task_struct *child, unsigned long addr,
 478                       unsigned long *code)
 479 {
 480         struct debug_trap *p = &child->thread.debug_trap;
 481         int i;
 482
 483         /* Search debug trap entry. */
 484         for (i = 0; i < p->nr_trap; i++) {
 485                 if (p->addr[i] == addr)
 486                         break;
 487         }
 488         if (i >= p->nr_trap) {
 489                 /* The trap may be requested from debugger.
 490                  * ptrace should do nothing in this case.
 491                  */
 492                 return 0;
 493         }
 494
 495         /* Recover orignal instruction code. */
 496         *code = p->insn[i];
 497
 498         /* Shift debug trap entries. */
 499         while (i < p->nr_trap - 1) {
 500                 p->insn[i] = p->insn[i + 1];
 501                 p->addr[i] = p->addr[i + 1];
 502                 i++;
 503         }
 504         p->nr_trap--;
 505         return 1;
 506 }
 507
 508 static void
 509 unregister_all_debug_traps(struct task_struct *child)
 510 {
 511         struct debug_trap *p = &child->thread.debug_trap;
 512         int i;
 513
 514         for (i = 0; i < p->nr_trap; i++)
 515                 access_process_vm(child, p->addr[i], &p->insn[i], sizeof(p->insn[i]), 1);
 516         p->nr_trap = 0;
 517 }
 518
 519 static inline void
 520 invalidate_cache(void)
 521 {
 522 #if defined(CONFIG_CHIP_M32700) || defined(CONFIG_CHIP_OPSP)
 523
 524         _flush_cache_copyback_all();
 525
 526 #else   /* ! CONFIG_CHIP_M32700 */
 527
 528         /* Invalidate cache */
 529         __asm__ __volatile__ (
 530                 "ldi    r0, #-1                                 \n\t"
 531                 "ldi    r1, #0                                  \n\t"
 532                 "stb    r1, @r0         ; cache off             \n\t"
 533                 ";                                              \n\t"
 534                 "ldi    r0, #-2                                 \n\t"
 535                 "ldi    r1, #1                                  \n\t"
 536                 "stb    r1, @r0         ; cache invalidate      \n\t"
 537                 ".fillinsn                                      \n"
 538                 "0:                                             \n\t"
 539                 "ldb    r1, @r0         ; invalidate check      \n\t"
 540                 "bnez   r1, 0b                                  \n\t"
 541                 ";                                              \n\t"
 542                 "ldi    r0, #-1                                 \n\t"
 543                 "ldi    r1, #1                                  \n\t"
 544                 "stb    r1, @r0         ; cache on              \n\t"
 545                 : : : "r0", "r1", "memory"
 546         );
 547         /* FIXME: copying-back d-cache and invalidating i-cache are needed.
 548          */
 549 #endif  /* CONFIG_CHIP_M32700 */
 550 }
 551
 552 /* Embed a debug trap (TRAP1) code */
 553 static int
 554 embed_debug_trap(struct task_struct *child, unsigned long next_pc)
 555 {
 556         unsigned long next_insn, code;
 557         unsigned long addr = next_pc & ~3;
 558
 559         if (access_process_vm(child, addr, &next_insn, sizeof(next_insn), 0)
 560             != sizeof(next_insn)) {
 561                 return -1; /* error */
 562         }
 563
 564         /* Set a trap code. */
 565         if (register_debug_trap(child, next_pc, next_insn, &code)) {
 566                 return -1; /* error */
 567         }
 568         if (access_process_vm(child, addr, &code, sizeof(code), 1)
 569             != sizeof(code)) {
 570                 return -1; /* error */
 571         }
 572         return 0; /* success */
 573 }
 574
 575 void
 576 withdraw_debug_trap(struct pt_regs *regs)
 577 {
 578         unsigned long addr;
 579         unsigned long code;
 580
 581         addr = (regs->bpc - 2) & ~3;
 582         regs->bpc -= 2;
 583         if (unregister_debug_trap(current, addr, &code)) {
 584             access_process_vm(current, addr, &code, sizeof(code), 1);
 585             invalidate_cache();
 586         }
 587 }
 588
 589 static void
 590 init_debug_traps(struct task_struct *child)
 591 {
 592         struct debug_trap *p = &child->thread.debug_trap;
 593         int i;
 594         p->nr_trap = 0;
 595         for (i = 0; i < MAX_TRAPS; i++) {
 596                 p->addr[i] = 0;
 597                 p->insn[i] = 0;
 598         }
 599 }
 600
 601
 602 /*
 603  * Called by kernel/ptrace.c when detaching..
 604  *
 605  * Make sure single step bits etc are not set.
 606  */
 607 void ptrace_disable(struct task_struct *child)
 608 {
 609         /* nothing to do.. */
 610 }
 611
 612 static int
 613 do_ptrace(long request, struct task_struct *child, long addr, long data)
 614 {
 615         unsigned long tmp;
 616         int ret;
 617
 618         switch (request) {
 619         /*
 620          * read word at location "addr" in the child process.
 621          */
 622         case PTRACE_PEEKTEXT:
 623         case PTRACE_PEEKDATA:
 624                 ret = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
 625                 if (ret == sizeof(tmp))
 626                         ret = put_user(tmp,(unsigned long __user *) data);
 627                 else
 628                         ret = -EIO;
 629                 break;
 630
 631         /*
 632          * read the word at location addr in the USER area.
 633          */
 634         case PTRACE_PEEKUSR:
 635                 ret = ptrace_read_user(child, addr,
 636                                        (unsigned long __user *)data);
 637                 break;
 638
 639         /*
 640          * write the word at location addr.
 641          */
 642         case PTRACE_POKETEXT:
 643         case PTRACE_POKEDATA:
 644                 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
 645                 if (ret == sizeof(data)) {
 646                         ret = 0;
 647                         if (request == PTRACE_POKETEXT) {
 648                                 invalidate_cache();
 649                         }
 650                 } else {
 651                         ret = -EIO;
 652                 }
 653                 break;
 654
 655         /*
 656          * write the word at location addr in the USER area.
 657          */
 658         case PTRACE_POKEUSR:
 659                 ret = ptrace_write_user(child, addr, data);
 660                 break;
 661
 662         /*
 663          * continue/restart and stop at next (return from) syscall
 664          */
 665         case PTRACE_SYSCALL:
 666         case PTRACE_CONT:
 667                 ret = -EIO;
 668                 if ((unsigned long) data > _NSIG)
 669                         break;
 670                 if (request == PTRACE_SYSCALL)
 671                         set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 672                 else
 673                         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 674                 child->exit_code = data;
 675                 wake_up_process(child);
 676                 ret = 0;
 677                 break;
 678
 679         /*
 680          * make the child exit.  Best I can do is send it a sigkill.
 681          * perhaps it should be put in the status that it wants to
 682          * exit.
 683          */
 684         case PTRACE_KILL: {
 685                 ret = 0;
 686                 unregister_all_debug_traps(child);
 687                 invalidate_cache();
 688                 if (child->exit_state == EXIT_ZOMBIE)   /* already dead */
 689                         break;
 690                 child->exit_code = SIGKILL;
 691                 wake_up_process(child);
 692                 break;
 693         }
 694
 695         /*
 696          * execute single instruction.
 697          */
 698         case PTRACE_SINGLESTEP: {
 699                 unsigned long next_pc;
 700                 unsigned long pc, insn;
 701
 702                 ret = -EIO;
 703                 if ((unsigned long) data > _NSIG)
 704                         break;
 705                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 706                 if ((child->ptrace & PT_DTRACE) == 0) {
 707                         /* Spurious delayed TF traps may occur */
 708                         child->ptrace |= PT_DTRACE;
 709                 }
 710
 711                 /* Compute next pc.  */
 712                 pc = get_stack_long(child, PT_BPC);
 713
 714                 if (access_process_vm(child, pc&~3, &insn, sizeof(insn), 0)
 715                     != sizeof(insn))
 716                         break;
 717
 718                 compute_next_pc(insn, pc, &next_pc, child);
 719                 if (next_pc & 0x80000000)
 720                         break;
 721
 722                 if (embed_debug_trap(child, next_pc))
 723                         break;
 724
 725                 invalidate_cache();
 726                 child->exit_code = data;
 727
 728                 /* give it a chance to run. */
 729                 wake_up_process(child);
 730                 ret = 0;
 731                 break;
 732         }
 733
 734         /*
 735          * detach a process that was attached.
 736          */
 737         case PTRACE_DETACH:
 738                 ret = 0;
 739                 ret = ptrace_detach(child, data);
 740                 break;
 741
 742         case PTRACE_GETREGS:
 743                 ret = ptrace_getregs(child, (void __user *)data);
 744                 break;
 745
 746         case PTRACE_SETREGS:
 747                 ret = ptrace_setregs(child, (void __user *)data);
 748                 break;
 749
 750         default:
 751                 ret = ptrace_request(child, request, addr, data);
 752                 break;
 753         }
 754
 755         return ret;
 756 }
 757
 758 asmlinkage int sys_ptrace(long request, long pid, long addr, long data)
 759 {
 760         struct task_struct *child;
 761         int ret;
 762
 763         lock_kernel();
 764         ret = -EPERM;
 765         if (request == PTRACE_TRACEME) {
 766                 /* are we already being traced? */
 767                 if (current->ptrace & PT_PTRACED)
 768                         goto out;
 769                 /* set the ptrace bit in the process flags. */
 770                 current->ptrace |= PT_PTRACED;
 771                 ret = 0;
 772                 goto out;
 773         }
 774         ret = -ESRCH;
 775         read_lock(&tasklist_lock);
 776         child = find_task_by_pid(pid);
 777         if (child)
 778                 get_task_struct(child);
 779         read_unlock(&tasklist_lock);
 780         if (!child)
 781                 goto out;
 782
 783         ret = -EPERM;
 784         if (pid == 1)           /* you may not mess with init */
 785                 goto out;
 786
 787         if (request == PTRACE_ATTACH) {
 788                 ret = ptrace_attach(child);
 789                 if (ret == 0)
 790                         init_debug_traps(child);
 791                 goto out_tsk;
 792         }
 793
 794         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 795         if (ret == 0)
 796                 ret = do_ptrace(request, child, addr, data);
 797
 798 out_tsk:
 799         put_task_struct(child);
 800 out:
 801         unlock_kernel();
 802
 803         return ret;
 804 }
 805
 806 /* notification of system call entry/exit
 807  * - triggered by current->work.syscall_trace
 808  */
 809 void do_syscall_trace(void)
 810 {
 811         if (!test_thread_flag(TIF_SYSCALL_TRACE))
 812                 return;
 813         if (!(current->ptrace & PT_PTRACED))
 814                 return;
 815         /* the 0x80 provides a way for the tracing parent to distinguish
 816            between a syscall stop and SIGTRAP delivery */
 817         ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
 818                                  ? 0x80 : 0));
 819
 820         /*
 821          * this isn't the same as continuing with a signal, but it will do
 822          * for normal use.  strace only continues with a signal if the
 823          * stopping signal is not SIGTRAP.  -brl
 824          */
 825         if (current->exit_code) {
 826                 send_sig(current->exit_code, current, 1);
 827                 current->exit_code = 0;
 828         }
 829 }