arch/i386/kernel/ptrace.c

   1 /* ptrace.c */
   2 /* By Ross Biro 1/23/92 */
   3 /*
   4  * Pentium III FXSR, SSE support
   5  *      Gareth Hughes <gareth@valinux.com>, May 2000
   6  */
   7
   8 #include <linux/kernel.h>
   9 #include <linux/sched.h>
  10 #include <linux/mm.h>
  11 #include <linux/smp.h>
  12 #include <linux/smp_lock.h>
  13 #include <linux/errno.h>
  14 #include <linux/ptrace.h>
  15 #include <linux/user.h>
  16 #include <linux/security.h>
  17 #include <linux/audit.h>
  18 #include <linux/seccomp.h>
  19
  20 #include <asm/uaccess.h>
  21 #include <asm/pgtable.h>
  22 #include <asm/system.h>
  23 #include <asm/processor.h>
  24 #include <asm/i387.h>
  25 #include <asm/debugreg.h>
  26 #include <asm/ldt.h>
  27 #include <asm/desc.h>
  28
  29 /*
  30  * does not yet catch signals sent when the child dies.
  31  * in exit.c or in signal.c.
  32  */
  33
  34 /* determines which flags the user has access to. */
  35 /* 1 = access 0 = no access */
  36 #define FLAG_MASK 0x00044dd5
  37
  38 /* set's the trap flag. */
  39 #define TRAP_FLAG 0x100
  40
  41 /*
  42  * Offset of eflags on child stack..
  43  */
  44 #define EFL_OFFSET ((EFL-2)*4-sizeof(struct pt_regs))
  45
  46 static inline struct pt_regs *get_child_regs(struct task_struct *task)
  47 {
  48         void *stack_top = (void *)task->thread.esp0;
  49         return stack_top - sizeof(struct pt_regs);
  50 }
  51
  52 /*
  53  * this routine will get a word off of the processes privileged stack.
  54  * the offset is how far from the base addr as stored in the TSS.
  55  * this routine assumes that all the privileged stacks are in our
  56  * data space.
  57  */
  58 static inline int get_stack_long(struct task_struct *task, int offset)
  59 {
  60         unsigned char *stack;
  61
  62         stack = (unsigned char *)task->thread.esp0;
  63         stack += offset;
  64         return (*((int *)stack));
  65 }
  66
  67 /*
  68  * this routine will put a word on the processes privileged stack.
  69  * the offset is how far from the base addr as stored in the TSS.
  70  * this routine assumes that all the privileged stacks are in our
  71  * data space.
  72  */
  73 static inline int put_stack_long(struct task_struct *task, int offset,
  74         unsigned long data)
  75 {
  76         unsigned char * stack;
  77
  78         stack = (unsigned char *) task->thread.esp0;
  79         stack += offset;
  80         *(unsigned long *) stack = data;
  81         return 0;
  82 }
  83
  84 static int putreg(struct task_struct *child,
  85         unsigned long regno, unsigned long value)
  86 {
  87         switch (regno >> 2) {
  88                 case FS:
  89                         if (value && (value & 3) != 3)
  90                                 return -EIO;
  91                         child->thread.fs = value;
  92                         return 0;
  93                 case GS:
  94                         if (value && (value & 3) != 3)
  95                                 return -EIO;
  96                         child->thread.gs = value;
  97                         return 0;
  98                 case DS:
  99                 case ES:
 100                         if (value && (value & 3) != 3)
 101                                 return -EIO;
 102                         value &= 0xffff;
 103                         break;
 104                 case SS:
 105                 case CS:
 106                         if ((value & 3) != 3)
 107                                 return -EIO;
 108                         value &= 0xffff;
 109                         break;
 110                 case EFL:
 111                         value &= FLAG_MASK;
 112                         value |= get_stack_long(child, EFL_OFFSET) & ~FLAG_MASK;
 113                         break;
 114         }
 115         if (regno > GS*4)
 116                 regno -= 2*4;
 117         put_stack_long(child, regno - sizeof(struct pt_regs), value);
 118         return 0;
 119 }
 120
 121 static unsigned long getreg(struct task_struct *child,
 122         unsigned long regno)
 123 {
 124         unsigned long retval = ~0UL;
 125
 126         switch (regno >> 2) {
 127                 case FS:
 128                         retval = child->thread.fs;
 129                         break;
 130                 case GS:
 131                         retval = child->thread.gs;
 132                         break;
 133                 case DS:
 134                 case ES:
 135                 case SS:
 136                 case CS:
 137                         retval = 0xffff;
 138                         /* fall through */
 139                 default:
 140                         if (regno > GS*4)
 141                                 regno -= 2*4;
 142                         regno = regno - sizeof(struct pt_regs);
 143                         retval &= get_stack_long(child, regno);
 144         }
 145         return retval;
 146 }
 147
 148 #define LDT_SEGMENT 4
 149
 150 static unsigned long convert_eip_to_linear(struct task_struct *child, struct pt_regs *regs)
 151 {
 152         unsigned long addr, seg;
 153
 154         addr = regs->eip;
 155         seg = regs->xcs & 0xffff;
 156         if (regs->eflags & VM_MASK) {
 157                 addr = (addr & 0xffff) + (seg << 4);
 158                 return addr;
 159         }
 160
 161         /*
 162          * We'll assume that the code segments in the GDT
 163          * are all zero-based. That is largely true: the
 164          * TLS segments are used for data, and the PNPBIOS
 165          * and APM bios ones we just ignore here.
 166          */
 167         if (seg & LDT_SEGMENT) {
 168                 u32 *desc;
 169                 unsigned long base;
 170
 171                 down(&child->mm->context.sem);
 172                 desc = child->mm->context.ldt + (seg & ~7);
 173                 base = (desc[0] >> 16) | ((desc[1] & 0xff) << 16) | (desc[1] & 0xff000000);
 174
 175                 /* 16-bit code segment? */
 176                 if (!((desc[1] >> 22) & 1))
 177                         addr &= 0xffff;
 178                 addr += base;
 179                 up(&child->mm->context.sem);
 180         }
 181         return addr;
 182 }
 183
 184 static inline int is_at_popf(struct task_struct *child, struct pt_regs *regs)
 185 {
 186         int i, copied;
 187         unsigned char opcode[16];
 188         unsigned long addr = convert_eip_to_linear(child, regs);
 189
 190         copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0);
 191         for (i = 0; i < copied; i++) {
 192                 switch (opcode[i]) {
 193                 /* popf */
 194                 case 0x9d:
 195                         return 1;
 196                 /* opcode and address size prefixes */
 197                 case 0x66: case 0x67:
 198                         continue;
 199                 /* irrelevant prefixes (segment overrides and repeats) */
 200                 case 0x26: case 0x2e:
 201                 case 0x36: case 0x3e:
 202                 case 0x64: case 0x65:
 203                 case 0xf0: case 0xf2: case 0xf3:
 204                         continue;
 205
 206                 /*
 207                  * pushf: NOTE! We should probably not let
 208                  * the user see the TF bit being set. But
 209                  * it's more pain than it's worth to avoid
 210                  * it, and a debugger could emulate this
 211                  * all in user space if it _really_ cares.
 212                  */
 213                 case 0x9c:
 214                 default:
 215                         return 0;
 216                 }
 217         }
 218         return 0;
 219 }
 220
 221 static void set_singlestep(struct task_struct *child)
 222 {
 223         struct pt_regs *regs = get_child_regs(child);
 224
 225         /*
 226          * Always set TIF_SINGLESTEP - this guarantees that
 227          * we single-step system calls etc..  This will also
 228          * cause us to set TF when returning to user mode.
 229          */
 230         set_tsk_thread_flag(child, TIF_SINGLESTEP);
 231
 232         /*
 233          * If TF was already set, don't do anything else
 234          */
 235         if (regs->eflags & TRAP_FLAG)
 236                 return;
 237
 238         /* Set TF on the kernel stack.. */
 239         regs->eflags |= TRAP_FLAG;
 240
 241         /*
 242          * ..but if TF is changed by the instruction we will trace,
 243          * don't mark it as being "us" that set it, so that we
 244          * won't clear it by hand later.
 245          */
 246         if (is_at_popf(child, regs))
 247                 return;
 248
 249         child->ptrace |= PT_DTRACE;
 250 }
 251
 252 static void clear_singlestep(struct task_struct *child)
 253 {
 254         /* Always clear TIF_SINGLESTEP... */
 255         clear_tsk_thread_flag(child, TIF_SINGLESTEP);
 256
 257         /* But touch TF only if it was set by us.. */
 258         if (child->ptrace & PT_DTRACE) {
 259                 struct pt_regs *regs = get_child_regs(child);
 260                 regs->eflags &= ~TRAP_FLAG;
 261                 child->ptrace &= ~PT_DTRACE;
 262         }
 263 }
 264
 265 /*
 266  * Called by kernel/ptrace.c when detaching..
 267  *
 268  * Make sure the single step bit is not set.
 269  */
 270 void ptrace_disable(struct task_struct *child)
 271 {
 272         clear_singlestep(child);
 273 }
 274
 275 /*
 276  * Perform get_thread_area on behalf of the traced child.
 277  */
 278 static int
 279 ptrace_get_thread_area(struct task_struct *child,
 280                        int idx, struct user_desc __user *user_desc)
 281 {
 282         struct user_desc info;
 283         struct desc_struct *desc;
 284
 285 /*
 286  * Get the current Thread-Local Storage area:
 287  */
 288
 289 #define GET_BASE(desc) ( \
 290         (((desc)->a >> 16) & 0x0000ffff) | \
 291         (((desc)->b << 16) & 0x00ff0000) | \
 292         ( (desc)->b        & 0xff000000)   )
 293
 294 #define GET_LIMIT(desc) ( \
 295         ((desc)->a & 0x0ffff) | \
 296          ((desc)->b & 0xf0000) )
 297
 298 #define GET_32BIT(desc)         (((desc)->b >> 22) & 1)
 299 #define GET_CONTENTS(desc)      (((desc)->b >> 10) & 3)
 300 #define GET_WRITABLE(desc)      (((desc)->b >>  9) & 1)
 301 #define GET_LIMIT_PAGES(desc)   (((desc)->b >> 23) & 1)
 302 #define GET_PRESENT(desc)       (((desc)->b >> 15) & 1)
 303 #define GET_USEABLE(desc)       (((desc)->b >> 20) & 1)
 304
 305         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
 306                 return -EINVAL;
 307
 308         desc = child->thread.tls_array + idx - GDT_ENTRY_TLS_MIN;
 309
 310         info.entry_number = idx;
 311         info.base_addr = GET_BASE(desc);
 312         info.limit = GET_LIMIT(desc);
 313         info.seg_32bit = GET_32BIT(desc);
 314         info.contents = GET_CONTENTS(desc);
 315         info.read_exec_only = !GET_WRITABLE(desc);
 316         info.limit_in_pages = GET_LIMIT_PAGES(desc);
 317         info.seg_not_present = !GET_PRESENT(desc);
 318         info.useable = GET_USEABLE(desc);
 319
 320         if (copy_to_user(user_desc, &info, sizeof(info)))
 321                 return -EFAULT;
 322
 323         return 0;
 324 }
 325
 326 /*
 327  * Perform set_thread_area on behalf of the traced child.
 328  */
 329 static int
 330 ptrace_set_thread_area(struct task_struct *child,
 331                        int idx, struct user_desc __user *user_desc)
 332 {
 333         struct user_desc info;
 334         struct desc_struct *desc;
 335
 336         if (copy_from_user(&info, user_desc, sizeof(info)))
 337                 return -EFAULT;
 338
 339         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
 340                 return -EINVAL;
 341
 342         desc = child->thread.tls_array + idx - GDT_ENTRY_TLS_MIN;
 343         if (LDT_empty(&info)) {
 344                 desc->a = 0;
 345                 desc->b = 0;
 346         } else {
 347                 desc->a = LDT_entry_a(&info);
 348                 desc->b = LDT_entry_b(&info);
 349         }
 350
 351         return 0;
 352 }
 353
 354 asmlinkage int sys_ptrace(long request, long pid, long addr, long data)
 355 {
 356         struct task_struct *child;
 357         struct user * dummy = NULL;
 358         int i, ret;
 359         unsigned long __user *datap = (unsigned long __user *)data;
 360
 361         lock_kernel();
 362         ret = -EPERM;
 363         if (request == PTRACE_TRACEME) {
 364                 /* are we already being traced? */
 365                 if (current->ptrace & PT_PTRACED)
 366                         goto out;
 367                 ret = security_ptrace(current->parent, current);
 368                 if (ret)
 369                         goto out;
 370                 /* set the ptrace bit in the process flags. */
 371                 current->ptrace |= PT_PTRACED;
 372                 ret = 0;
 373                 goto out;
 374         }
 375         ret = -ESRCH;
 376         read_lock(&tasklist_lock);
 377         child = find_task_by_pid(pid);
 378         if (child)
 379                 get_task_struct(child);
 380         read_unlock(&tasklist_lock);
 381         if (!child)
 382                 goto out;
 383
 384         ret = -EPERM;
 385         if (pid == 1)           /* you may not mess with init */
 386                 goto out_tsk;
 387
 388         if (request == PTRACE_ATTACH) {
 389                 ret = ptrace_attach(child);
 390                 goto out_tsk;
 391         }
 392
 393         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 394         if (ret < 0)
 395                 goto out_tsk;
 396
 397         switch (request) {
 398         /* when I and D space are separate, these will need to be fixed. */
 399         case PTRACE_PEEKTEXT: /* read word at location addr. */
 400         case PTRACE_PEEKDATA: {
 401                 unsigned long tmp;
 402                 int copied;
 403
 404                 copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
 405                 ret = -EIO;
 406                 if (copied != sizeof(tmp))
 407                         break;
 408                 ret = put_user(tmp, datap);
 409                 break;
 410         }
 411
 412         /* read the word at location addr in the USER area. */
 413         case PTRACE_PEEKUSR: {
 414                 unsigned long tmp;
 415
 416                 ret = -EIO;
 417                 if ((addr & 3) || addr < 0 ||
 418                     addr > sizeof(struct user) - 3)
 419                         break;
 420
 421                 tmp = 0;  /* Default return condition */
 422                 if(addr < FRAME_SIZE*sizeof(long))
 423                         tmp = getreg(child, addr);
 424                 if(addr >= (long) &dummy->u_debugreg[0] &&
 425                    addr <= (long) &dummy->u_debugreg[7]){
 426                         addr -= (long) &dummy->u_debugreg[0];
 427                         addr = addr >> 2;
 428                         tmp = child->thread.debugreg[addr];
 429                 }
 430                 ret = put_user(tmp, datap);
 431                 break;
 432         }
 433
 434         /* when I and D space are separate, this will have to be fixed. */
 435         case PTRACE_POKETEXT: /* write the word at location addr. */
 436         case PTRACE_POKEDATA:
 437                 ret = 0;
 438                 if (access_process_vm(child, addr, &data, sizeof(data), 1) == sizeof(data))
 439                         break;
 440                 ret = -EIO;
 441                 break;
 442
 443         case PTRACE_POKEUSR: /* write the word at location addr in the USER area */
 444                 ret = -EIO;
 445                 if ((addr & 3) || addr < 0 ||
 446                     addr > sizeof(struct user) - 3)
 447                         break;
 448
 449                 if (addr < FRAME_SIZE*sizeof(long)) {
 450                         ret = putreg(child, addr, data);
 451                         break;
 452                 }
 453                 /* We need to be very careful here.  We implicitly
 454                    want to modify a portion of the task_struct, and we
 455                    have to be selective about what portions we allow someone
 456                    to modify. */
 457
 458                   ret = -EIO;
 459                   if(addr >= (long) &dummy->u_debugreg[0] &&
 460                      addr <= (long) &dummy->u_debugreg[7]){
 461
 462                           if(addr == (long) &dummy->u_debugreg[4]) break;
 463                           if(addr == (long) &dummy->u_debugreg[5]) break;
 464                           if(addr < (long) &dummy->u_debugreg[4] &&
 465                              ((unsigned long) data) >= TASK_SIZE-3) break;
 466
 467                           /* Sanity-check data. Take one half-byte at once with
 468                            * check = (val >> (16 + 4*i)) & 0xf. It contains the
 469                            * R/Wi and LENi bits; bits 0 and 1 are R/Wi, and bits
 470                            * 2 and 3 are LENi. Given a list of invalid values,
 471                            * we do mask |= 1 << invalid_value, so that
 472                            * (mask >> check) & 1 is a correct test for invalid
 473                            * values.
 474                            *
 475                            * R/Wi contains the type of the breakpoint /
 476                            * watchpoint, LENi contains the length of the watched
 477                            * data in the watchpoint case.
 478                            *
 479                            * The invalid values are:
 480                            * - LENi == 0x10 (undefined), so mask |= 0x0f00.
 481                            * - R/Wi == 0x10 (break on I/O reads or writes), so
 482                            *   mask |= 0x4444.
 483                            * - R/Wi == 0x00 && LENi != 0x00, so we have mask |=
 484                            *   0x1110.
 485                            *
 486                            * Finally, mask = 0x0f00 | 0x4444 | 0x1110 == 0x5f54.
 487                            *
 488                            * See the Intel Manual "System Programming Guide",
 489                            * 15.2.4
 490                            *
 491                            * Note that LENi == 0x10 is defined on x86_64 in long
 492                            * mode (i.e. even for 32-bit userspace software, but
 493                            * 64-bit kernel), so the x86_64 mask value is 0x5454.
 494                            * See the AMD manual no. 24593 (AMD64 System
 495                            * Programming)*/
 496
 497                           if(addr == (long) &dummy->u_debugreg[7]) {
 498                                   data &= ~DR_CONTROL_RESERVED;
 499                                   for(i=0; i<4; i++)
 500                                           if ((0x5f54 >> ((data >> (16 + 4*i)) & 0xf)) & 1)
 501                                                   goto out_tsk;
 502                           }
 503
 504                           addr -= (long) &dummy->u_debugreg;
 505                           addr = addr >> 2;
 506                           child->thread.debugreg[addr] = data;
 507                           ret = 0;
 508                   }
 509                   break;
 510
 511         case PTRACE_SYSCALL:    /* continue and stop at next (return from) syscall */
 512         case PTRACE_CONT:       /* restart after signal. */
 513                 ret = -EIO;
 514                 if ((unsigned long) data > _NSIG)
 515                         break;
 516                 if (request == PTRACE_SYSCALL) {
 517                         set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 518                 }
 519                 else {
 520                         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 521                 }
 522                 child->exit_code = data;
 523                 /* make sure the single step bit is not set. */
 524                 clear_singlestep(child);
 525                 wake_up_process(child);
 526                 ret = 0;
 527                 break;
 528
 529 /*
 530  * make the child exit.  Best I can do is send it a sigkill.
 531  * perhaps it should be put in the status that it wants to
 532  * exit.
 533  */
 534         case PTRACE_KILL:
 535                 ret = 0;
 536                 if (child->exit_state == EXIT_ZOMBIE)   /* already dead */
 537                         break;
 538                 child->exit_code = SIGKILL;
 539                 /* make sure the single step bit is not set. */
 540                 clear_singlestep(child);
 541                 wake_up_process(child);
 542                 break;
 543
 544         case PTRACE_SINGLESTEP: /* set the trap flag. */
 545                 ret = -EIO;
 546                 if ((unsigned long) data > _NSIG)
 547                         break;
 548                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 549                 set_singlestep(child);
 550                 child->exit_code = data;
 551                 /* give it a chance to run. */
 552                 wake_up_process(child);
 553                 ret = 0;
 554                 break;
 555
 556         case PTRACE_DETACH:
 557                 /* detach a process that was attached. */
 558                 ret = ptrace_detach(child, data);
 559                 break;
 560
 561         case PTRACE_GETREGS: { /* Get all gp regs from the child. */
 562                 if (!access_ok(VERIFY_WRITE, datap, FRAME_SIZE*sizeof(long))) {
 563                         ret = -EIO;
 564                         break;
 565                 }
 566                 for ( i = 0; i < FRAME_SIZE*sizeof(long); i += sizeof(long) ) {
 567                         __put_user(getreg(child, i), datap);
 568                         datap++;
 569                 }
 570                 ret = 0;
 571                 break;
 572         }
 573
 574         case PTRACE_SETREGS: { /* Set all gp regs in the child. */
 575                 unsigned long tmp;
 576                 if (!access_ok(VERIFY_READ, datap, FRAME_SIZE*sizeof(long))) {
 577                         ret = -EIO;
 578                         break;
 579                 }
 580                 for ( i = 0; i < FRAME_SIZE*sizeof(long); i += sizeof(long) ) {
 581                         __get_user(tmp, datap);
 582                         putreg(child, i, tmp);
 583                         datap++;
 584                 }
 585                 ret = 0;
 586                 break;
 587         }
 588
 589         case PTRACE_GETFPREGS: { /* Get the child FPU state. */
 590                 if (!access_ok(VERIFY_WRITE, datap,
 591                                sizeof(struct user_i387_struct))) {
 592                         ret = -EIO;
 593                         break;
 594                 }
 595                 ret = 0;
 596                 if (!tsk_used_math(child))
 597                         init_fpu(child);
 598                 get_fpregs((struct user_i387_struct __user *)data, child);
 599                 break;
 600         }
 601
 602         case PTRACE_SETFPREGS: { /* Set the child FPU state. */
 603                 if (!access_ok(VERIFY_READ, datap,
 604                                sizeof(struct user_i387_struct))) {
 605                         ret = -EIO;
 606                         break;
 607                 }
 608                 set_stopped_child_used_math(child);
 609                 set_fpregs(child, (struct user_i387_struct __user *)data);
 610                 ret = 0;
 611                 break;
 612         }
 613
 614         case PTRACE_GETFPXREGS: { /* Get the child extended FPU state. */
 615                 if (!access_ok(VERIFY_WRITE, datap,
 616                                sizeof(struct user_fxsr_struct))) {
 617                         ret = -EIO;
 618                         break;
 619                 }
 620                 if (!tsk_used_math(child))
 621                         init_fpu(child);
 622                 ret = get_fpxregs((struct user_fxsr_struct __user *)data, child);
 623                 break;
 624         }
 625
 626         case PTRACE_SETFPXREGS: { /* Set the child extended FPU state. */
 627                 if (!access_ok(VERIFY_READ, datap,
 628                                sizeof(struct user_fxsr_struct))) {
 629                         ret = -EIO;
 630                         break;
 631                 }
 632                 set_stopped_child_used_math(child);
 633                 ret = set_fpxregs(child, (struct user_fxsr_struct __user *)data);
 634                 break;
 635         }
 636
 637         case PTRACE_GET_THREAD_AREA:
 638                 ret = ptrace_get_thread_area(child, addr,
 639                                         (struct user_desc __user *) data);
 640                 break;
 641
 642         case PTRACE_SET_THREAD_AREA:
 643                 ret = ptrace_set_thread_area(child, addr,
 644                                         (struct user_desc __user *) data);
 645                 break;
 646
 647         default:
 648                 ret = ptrace_request(child, request, addr, data);
 649                 break;
 650         }
 651 out_tsk:
 652         put_task_struct(child);
 653 out:
 654         unlock_kernel();
 655         return ret;
 656 }
 657
 658 void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, int error_code)
 659 {
 660         struct siginfo info;
 661
 662         tsk->thread.trap_no = 1;
 663         tsk->thread.error_code = error_code;
 664
 665         memset(&info, 0, sizeof(info));
 666         info.si_signo = SIGTRAP;
 667         info.si_code = TRAP_BRKPT;
 668
 669         /* User-mode eip? */
 670         info.si_addr = user_mode(regs) ? (void __user *) regs->eip : NULL;
 671
 672         /* Send us the fakey SIGTRAP */
 673         force_sig_info(SIGTRAP, &info, tsk);
 674 }
 675
 676 /* notification of system call entry/exit
 677  * - triggered by current->work.syscall_trace
 678  */
 679 __attribute__((regparm(3)))
 680 void do_syscall_trace(struct pt_regs *regs, int entryexit)
 681 {
 682         /* do the secure computing check first */
 683         secure_computing(regs->orig_eax);
 684
 685         if (unlikely(current->audit_context)) {
 686                 if (!entryexit)
 687                         audit_syscall_entry(current, regs->orig_eax,
 688                                             regs->ebx, regs->ecx,
 689                                             regs->edx, regs->esi);
 690                 else
 691                         audit_syscall_exit(current, regs->eax);
 692         }
 693
 694         if (!(current->ptrace & PT_PTRACED))
 695                 return;
 696
 697         /* Fake a debug trap */
 698         if (test_thread_flag(TIF_SINGLESTEP))
 699                 send_sigtrap(current, regs, 0);
 700
 701         if (!test_thread_flag(TIF_SYSCALL_TRACE))
 702                 return;
 703
 704         /* the 0x80 provides a way for the tracing parent to distinguish
 705            between a syscall stop and SIGTRAP delivery */
 706         ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD) ? 0x80 : 0));
 707
 708         /*
 709          * this isn't the same as continuing with a signal, but it will do
 710          * for normal use.  strace only continues with a signal if the
 711          * stopping signal is not SIGTRAP.  -brl
 712          */
 713         if (current->exit_code) {
 714                 send_sig(current->exit_code, current, 1);
 715                 current->exit_code = 0;
 716         }
 717 }