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/errno.h>
  13 #include <linux/ptrace.h>
  14 #include <linux/user.h>
  15 #include <linux/security.h>
  16 #include <linux/audit.h>
  17 #include <linux/seccomp.h>
  18 #include <linux/signal.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 /*
  35  * Determines which flags the user has access to [1 = access, 0 = no access].
  36  * Prohibits changing ID(21), VIP(20), VIF(19), VM(17), NT(14), IOPL(12-13), IF(9).
  37  * Also masks reserved bits (31-22, 15, 5, 3, 1).
  38  */
  39 #define FLAG_MASK 0x00050dd5
  40
  41 /* set's the trap flag. */
  42 #define TRAP_FLAG 0x100
  43
  44 /*
  45  * Offset of eflags on child stack..
  46  */
  47 #define EFL_OFFSET offsetof(struct pt_regs, eflags)
  48
  49 static inline struct pt_regs *get_child_regs(struct task_struct *task)
  50 {
  51         void *stack_top = (void *)task->thread.esp0;
  52         return stack_top - sizeof(struct pt_regs);
  53 }
  54
  55 /*
  56  * This routine will get a word off of the processes privileged stack.
  57  * the offset is bytes into the pt_regs structure on the stack.
  58  * This routine assumes that all the privileged stacks are in our
  59  * data space.
  60  */
  61 static inline int get_stack_long(struct task_struct *task, int offset)
  62 {
  63         unsigned char *stack;
  64
  65         stack = (unsigned char *)task->thread.esp0 - sizeof(struct pt_regs);
  66         stack += offset;
  67         return (*((int *)stack));
  68 }
  69
  70 /*
  71  * This routine will put a word on the processes privileged stack.
  72  * the offset is bytes into the pt_regs structure on the stack.
  73  * This routine assumes that all the privileged stacks are in our
  74  * data space.
  75  */
  76 static inline int put_stack_long(struct task_struct *task, int offset,
  77         unsigned long data)
  78 {
  79         unsigned char * stack;
  80
  81         stack = (unsigned char *)task->thread.esp0 - sizeof(struct pt_regs);
  82         stack += offset;
  83         *(unsigned long *) stack = data;
  84         return 0;
  85 }
  86
  87 static int putreg(struct task_struct *child,
  88         unsigned long regno, unsigned long value)
  89 {
  90         switch (regno >> 2) {
  91                 case GS:
  92                         if (value && (value & 3) != 3)
  93                                 return -EIO;
  94                         child->thread.gs = value;
  95                         return 0;
  96                 case DS:
  97                 case ES:
  98                 case FS:
  99                         if (value && (value & 3) != 3)
 100                                 return -EIO;
 101                         value &= 0xffff;
 102                         break;
 103                 case SS:
 104                 case CS:
 105                         if ((value & 3) != 3)
 106                                 return -EIO;
 107                         value &= 0xffff;
 108                         break;
 109                 case EFL:
 110                         value &= FLAG_MASK;
 111                         value |= get_stack_long(child, EFL_OFFSET) & ~FLAG_MASK;
 112                         break;
 113         }
 114         if (regno > FS*4)
 115                 regno -= 1*4;
 116         put_stack_long(child, regno, value);
 117         return 0;
 118 }
 119
 120 static unsigned long getreg(struct task_struct *child,
 121         unsigned long regno)
 122 {
 123         unsigned long retval = ~0UL;
 124
 125         switch (regno >> 2) {
 126                 case GS:
 127                         retval = child->thread.gs;
 128                         break;
 129                 case DS:
 130                 case ES:
 131                 case FS:
 132                 case SS:
 133                 case CS:
 134                         retval = 0xffff;
 135                         /* fall through */
 136                 default:
 137                         if (regno > FS*4)
 138                                 regno -= 1*4;
 139                         retval &= get_stack_long(child, regno);
 140         }
 141         return retval;
 142 }
 143
 144 #define LDT_SEGMENT 4
 145
 146 static unsigned long convert_eip_to_linear(struct task_struct *child, struct pt_regs *regs)
 147 {
 148         unsigned long addr, seg;
 149
 150         addr = regs->eip;
 151         seg = regs->xcs & 0xffff;
 152         if (regs->eflags & VM_MASK) {
 153                 addr = (addr & 0xffff) + (seg << 4);
 154                 return addr;
 155         }
 156
 157         /*
 158          * We'll assume that the code segments in the GDT
 159          * are all zero-based. That is largely true: the
 160          * TLS segments are used for data, and the PNPBIOS
 161          * and APM bios ones we just ignore here.
 162          */
 163         if (seg & LDT_SEGMENT) {
 164                 u32 *desc;
 165                 unsigned long base;
 166
 167                 down(&child->mm->context.sem);
 168                 desc = child->mm->context.ldt + (seg & ~7);
 169                 base = (desc[0] >> 16) | ((desc[1] & 0xff) << 16) | (desc[1] & 0xff000000);
 170
 171                 /* 16-bit code segment? */
 172                 if (!((desc[1] >> 22) & 1))
 173                         addr &= 0xffff;
 174                 addr += base;
 175                 up(&child->mm->context.sem);
 176         }
 177         return addr;
 178 }
 179
 180 static inline int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs)
 181 {
 182         int i, copied;
 183         unsigned char opcode[15];
 184         unsigned long addr = convert_eip_to_linear(child, regs);
 185
 186         copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0);
 187         for (i = 0; i < copied; i++) {
 188                 switch (opcode[i]) {
 189                 /* popf and iret */
 190                 case 0x9d: case 0xcf:
 191                         return 1;
 192                 /* opcode and address size prefixes */
 193                 case 0x66: case 0x67:
 194                         continue;
 195                 /* irrelevant prefixes (segment overrides and repeats) */
 196                 case 0x26: case 0x2e:
 197                 case 0x36: case 0x3e:
 198                 case 0x64: case 0x65:
 199                 case 0xf0: case 0xf2: case 0xf3:
 200                         continue;
 201
 202                 /*
 203                  * pushf: NOTE! We should probably not let
 204                  * the user see the TF bit being set. But
 205                  * it's more pain than it's worth to avoid
 206                  * it, and a debugger could emulate this
 207                  * all in user space if it _really_ cares.
 208                  */
 209                 case 0x9c:
 210                 default:
 211                         return 0;
 212                 }
 213         }
 214         return 0;
 215 }
 216
 217 static void set_singlestep(struct task_struct *child)
 218 {
 219         struct pt_regs *regs = get_child_regs(child);
 220
 221         /*
 222          * Always set TIF_SINGLESTEP - this guarantees that
 223          * we single-step system calls etc..  This will also
 224          * cause us to set TF when returning to user mode.
 225          */
 226         set_tsk_thread_flag(child, TIF_SINGLESTEP);
 227
 228         /*
 229          * If TF was already set, don't do anything else
 230          */
 231         if (regs->eflags & TRAP_FLAG)
 232                 return;
 233
 234         /* Set TF on the kernel stack.. */
 235         regs->eflags |= TRAP_FLAG;
 236
 237         /*
 238          * ..but if TF is changed by the instruction we will trace,
 239          * don't mark it as being "us" that set it, so that we
 240          * won't clear it by hand later.
 241          */
 242         if (is_setting_trap_flag(child, regs))
 243                 return;
 244
 245         child->ptrace |= PT_DTRACE;
 246 }
 247
 248 static void clear_singlestep(struct task_struct *child)
 249 {
 250         /* Always clear TIF_SINGLESTEP... */
 251         clear_tsk_thread_flag(child, TIF_SINGLESTEP);
 252
 253         /* But touch TF only if it was set by us.. */
 254         if (child->ptrace & PT_DTRACE) {
 255                 struct pt_regs *regs = get_child_regs(child);
 256                 regs->eflags &= ~TRAP_FLAG;
 257                 child->ptrace &= ~PT_DTRACE;
 258         }
 259 }
 260
 261 /*
 262  * Called by kernel/ptrace.c when detaching..
 263  *
 264  * Make sure the single step bit is not set.
 265  */
 266 void ptrace_disable(struct task_struct *child)
 267 {
 268         clear_singlestep(child);
 269         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 270         clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 271 }
 272
 273 /*
 274  * Perform get_thread_area on behalf of the traced child.
 275  */
 276 static int
 277 ptrace_get_thread_area(struct task_struct *child,
 278                        int idx, struct user_desc __user *user_desc)
 279 {
 280         struct user_desc info;
 281         struct desc_struct *desc;
 282
 283 /*
 284  * Get the current Thread-Local Storage area:
 285  */
 286
 287 #define GET_BASE(desc) ( \
 288         (((desc)->a >> 16) & 0x0000ffff) | \
 289         (((desc)->b << 16) & 0x00ff0000) | \
 290         ( (desc)->b        & 0xff000000)   )
 291
 292 #define GET_LIMIT(desc) ( \
 293         ((desc)->a & 0x0ffff) | \
 294          ((desc)->b & 0xf0000) )
 295
 296 #define GET_32BIT(desc)         (((desc)->b >> 22) & 1)
 297 #define GET_CONTENTS(desc)      (((desc)->b >> 10) & 3)
 298 #define GET_WRITABLE(desc)      (((desc)->b >>  9) & 1)
 299 #define GET_LIMIT_PAGES(desc)   (((desc)->b >> 23) & 1)
 300 #define GET_PRESENT(desc)       (((desc)->b >> 15) & 1)
 301 #define GET_USEABLE(desc)       (((desc)->b >> 20) & 1)
 302
 303         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
 304                 return -EINVAL;
 305
 306         desc = child->thread.tls_array + idx - GDT_ENTRY_TLS_MIN;
 307
 308         info.entry_number = idx;
 309         info.base_addr = GET_BASE(desc);
 310         info.limit = GET_LIMIT(desc);
 311         info.seg_32bit = GET_32BIT(desc);
 312         info.contents = GET_CONTENTS(desc);
 313         info.read_exec_only = !GET_WRITABLE(desc);
 314         info.limit_in_pages = GET_LIMIT_PAGES(desc);
 315         info.seg_not_present = !GET_PRESENT(desc);
 316         info.useable = GET_USEABLE(desc);
 317
 318         if (copy_to_user(user_desc, &info, sizeof(info)))
 319                 return -EFAULT;
 320
 321         return 0;
 322 }
 323
 324 /*
 325  * Perform set_thread_area on behalf of the traced child.
 326  */
 327 static int
 328 ptrace_set_thread_area(struct task_struct *child,
 329                        int idx, struct user_desc __user *user_desc)
 330 {
 331         struct user_desc info;
 332         struct desc_struct *desc;
 333
 334         if (copy_from_user(&info, user_desc, sizeof(info)))
 335                 return -EFAULT;
 336
 337         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
 338                 return -EINVAL;
 339
 340         desc = child->thread.tls_array + idx - GDT_ENTRY_TLS_MIN;
 341         if (LDT_empty(&info)) {
 342                 desc->a = 0;
 343                 desc->b = 0;
 344         } else {
 345                 desc->a = LDT_entry_a(&info);
 346                 desc->b = LDT_entry_b(&info);
 347         }
 348
 349         return 0;
 350 }
 351
 352 long arch_ptrace(struct task_struct *child, long request, long addr, long data)
 353 {
 354         struct user * dummy = NULL;
 355         int i, ret;
 356         unsigned long __user *datap = (unsigned long __user *)data;
 357
 358         switch (request) {
 359         /* when I and D space are separate, these will need to be fixed. */
 360         case PTRACE_PEEKTEXT: /* read word at location addr. */
 361         case PTRACE_PEEKDATA: {
 362                 unsigned long tmp;
 363                 int copied;
 364
 365                 copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
 366                 ret = -EIO;
 367                 if (copied != sizeof(tmp))
 368                         break;
 369                 ret = put_user(tmp, datap);
 370                 break;
 371         }
 372
 373         /* read the word at location addr in the USER area. */
 374         case PTRACE_PEEKUSR: {
 375                 unsigned long tmp;
 376
 377                 ret = -EIO;
 378                 if ((addr & 3) || addr < 0 ||
 379                     addr > sizeof(struct user) - 3)
 380                         break;
 381
 382                 tmp = 0;  /* Default return condition */
 383                 if(addr < FRAME_SIZE*sizeof(long))
 384                         tmp = getreg(child, addr);
 385                 if(addr >= (long) &dummy->u_debugreg[0] &&
 386                    addr <= (long) &dummy->u_debugreg[7]){
 387                         addr -= (long) &dummy->u_debugreg[0];
 388                         addr = addr >> 2;
 389                         tmp = child->thread.debugreg[addr];
 390                 }
 391                 ret = put_user(tmp, datap);
 392                 break;
 393         }
 394
 395         /* when I and D space are separate, this will have to be fixed. */
 396         case PTRACE_POKETEXT: /* write the word at location addr. */
 397         case PTRACE_POKEDATA:
 398                 ret = 0;
 399                 if (access_process_vm(child, addr, &data, sizeof(data), 1) == sizeof(data))
 400                         break;
 401                 ret = -EIO;
 402                 break;
 403
 404         case PTRACE_POKEUSR: /* write the word at location addr in the USER area */
 405                 ret = -EIO;
 406                 if ((addr & 3) || addr < 0 ||
 407                     addr > sizeof(struct user) - 3)
 408                         break;
 409
 410                 if (addr < FRAME_SIZE*sizeof(long)) {
 411                         ret = putreg(child, addr, data);
 412                         break;
 413                 }
 414                 /* We need to be very careful here.  We implicitly
 415                    want to modify a portion of the task_struct, and we
 416                    have to be selective about what portions we allow someone
 417                    to modify. */
 418
 419                   ret = -EIO;
 420                   if(addr >= (long) &dummy->u_debugreg[0] &&
 421                      addr <= (long) &dummy->u_debugreg[7]){
 422
 423                           if(addr == (long) &dummy->u_debugreg[4]) break;
 424                           if(addr == (long) &dummy->u_debugreg[5]) break;
 425                           if(addr < (long) &dummy->u_debugreg[4] &&
 426                              ((unsigned long) data) >= TASK_SIZE-3) break;
 427
 428                           /* Sanity-check data. Take one half-byte at once with
 429                            * check = (val >> (16 + 4*i)) & 0xf. It contains the
 430                            * R/Wi and LENi bits; bits 0 and 1 are R/Wi, and bits
 431                            * 2 and 3 are LENi. Given a list of invalid values,
 432                            * we do mask |= 1 << invalid_value, so that
 433                            * (mask >> check) & 1 is a correct test for invalid
 434                            * values.
 435                            *
 436                            * R/Wi contains the type of the breakpoint /
 437                            * watchpoint, LENi contains the length of the watched
 438                            * data in the watchpoint case.
 439                            *
 440                            * The invalid values are:
 441                            * - LENi == 0x10 (undefined), so mask |= 0x0f00.
 442                            * - R/Wi == 0x10 (break on I/O reads or writes), so
 443                            *   mask |= 0x4444.
 444                            * - R/Wi == 0x00 && LENi != 0x00, so we have mask |=
 445                            *   0x1110.
 446                            *
 447                            * Finally, mask = 0x0f00 | 0x4444 | 0x1110 == 0x5f54.
 448                            *
 449                            * See the Intel Manual "System Programming Guide",
 450                            * 15.2.4
 451                            *
 452                            * Note that LENi == 0x10 is defined on x86_64 in long
 453                            * mode (i.e. even for 32-bit userspace software, but
 454                            * 64-bit kernel), so the x86_64 mask value is 0x5454.
 455                            * See the AMD manual no. 24593 (AMD64 System
 456                            * Programming)*/
 457
 458                           if(addr == (long) &dummy->u_debugreg[7]) {
 459                                   data &= ~DR_CONTROL_RESERVED;
 460                                   for(i=0; i<4; i++)
 461                                           if ((0x5f54 >> ((data >> (16 + 4*i)) & 0xf)) & 1)
 462                                                   goto out_tsk;
 463                                   if (data)
 464                                           set_tsk_thread_flag(child, TIF_DEBUG);
 465                                   else
 466                                           clear_tsk_thread_flag(child, TIF_DEBUG);
 467                           }
 468                           addr -= (long) &dummy->u_debugreg;
 469                           addr = addr >> 2;
 470                           child->thread.debugreg[addr] = data;
 471                           ret = 0;
 472                   }
 473                   break;
 474
 475         case PTRACE_SYSEMU: /* continue and stop at next syscall, which will not be executed */
 476         case PTRACE_SYSCALL:    /* continue and stop at next (return from) syscall */
 477         case PTRACE_CONT:       /* restart after signal. */
 478                 ret = -EIO;
 479                 if (!valid_signal(data))
 480                         break;
 481                 if (request == PTRACE_SYSEMU) {
 482                         set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 483                         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 484                 } else if (request == PTRACE_SYSCALL) {
 485                         set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 486                         clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 487                 } else {
 488                         clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 489                         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 490                 }
 491                 child->exit_code = data;
 492                 /* make sure the single step bit is not set. */
 493                 clear_singlestep(child);
 494                 wake_up_process(child);
 495                 ret = 0;
 496                 break;
 497
 498 /*
 499  * make the child exit.  Best I can do is send it a sigkill.
 500  * perhaps it should be put in the status that it wants to
 501  * exit.
 502  */
 503         case PTRACE_KILL:
 504                 ret = 0;
 505                 if (child->exit_state == EXIT_ZOMBIE)   /* already dead */
 506                         break;
 507                 child->exit_code = SIGKILL;
 508                 /* make sure the single step bit is not set. */
 509                 clear_singlestep(child);
 510                 wake_up_process(child);
 511                 break;
 512
 513         case PTRACE_SYSEMU_SINGLESTEP: /* Same as SYSEMU, but singlestep if not syscall */
 514         case PTRACE_SINGLESTEP: /* set the trap flag. */
 515                 ret = -EIO;
 516                 if (!valid_signal(data))
 517                         break;
 518
 519                 if (request == PTRACE_SYSEMU_SINGLESTEP)
 520                         set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 521                 else
 522                         clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 523
 524                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 525                 set_singlestep(child);
 526                 child->exit_code = data;
 527                 /* give it a chance to run. */
 528                 wake_up_process(child);
 529                 ret = 0;
 530                 break;
 531
 532         case PTRACE_DETACH:
 533                 /* detach a process that was attached. */
 534                 ret = ptrace_detach(child, data);
 535                 break;
 536
 537         case PTRACE_GETREGS: { /* Get all gp regs from the child. */
 538                 if (!access_ok(VERIFY_WRITE, datap, FRAME_SIZE*sizeof(long))) {
 539                         ret = -EIO;
 540                         break;
 541                 }
 542                 for ( i = 0; i < FRAME_SIZE*sizeof(long); i += sizeof(long) ) {
 543                         __put_user(getreg(child, i), datap);
 544                         datap++;
 545                 }
 546                 ret = 0;
 547                 break;
 548         }
 549
 550         case PTRACE_SETREGS: { /* Set all gp regs in the child. */
 551                 unsigned long tmp;
 552                 if (!access_ok(VERIFY_READ, datap, FRAME_SIZE*sizeof(long))) {
 553                         ret = -EIO;
 554                         break;
 555                 }
 556                 for ( i = 0; i < FRAME_SIZE*sizeof(long); i += sizeof(long) ) {
 557                         __get_user(tmp, datap);
 558                         putreg(child, i, tmp);
 559                         datap++;
 560                 }
 561                 ret = 0;
 562                 break;
 563         }
 564
 565         case PTRACE_GETFPREGS: { /* Get the child FPU state. */
 566                 if (!access_ok(VERIFY_WRITE, datap,
 567                                sizeof(struct user_i387_struct))) {
 568                         ret = -EIO;
 569                         break;
 570                 }
 571                 ret = 0;
 572                 if (!tsk_used_math(child))
 573                         init_fpu(child);
 574                 get_fpregs((struct user_i387_struct __user *)data, child);
 575                 break;
 576         }
 577
 578         case PTRACE_SETFPREGS: { /* Set the child FPU state. */
 579                 if (!access_ok(VERIFY_READ, datap,
 580                                sizeof(struct user_i387_struct))) {
 581                         ret = -EIO;
 582                         break;
 583                 }
 584                 set_stopped_child_used_math(child);
 585                 set_fpregs(child, (struct user_i387_struct __user *)data);
 586                 ret = 0;
 587                 break;
 588         }
 589
 590         case PTRACE_GETFPXREGS: { /* Get the child extended FPU state. */
 591                 if (!access_ok(VERIFY_WRITE, datap,
 592                                sizeof(struct user_fxsr_struct))) {
 593                         ret = -EIO;
 594                         break;
 595                 }
 596                 if (!tsk_used_math(child))
 597                         init_fpu(child);
 598                 ret = get_fpxregs((struct user_fxsr_struct __user *)data, child);
 599                 break;
 600         }
 601
 602         case PTRACE_SETFPXREGS: { /* Set the child extended FPU state. */
 603                 if (!access_ok(VERIFY_READ, datap,
 604                                sizeof(struct user_fxsr_struct))) {
 605                         ret = -EIO;
 606                         break;
 607                 }
 608                 set_stopped_child_used_math(child);
 609                 ret = set_fpxregs(child, (struct user_fxsr_struct __user *)data);
 610                 break;
 611         }
 612
 613         case PTRACE_GET_THREAD_AREA:
 614                 ret = ptrace_get_thread_area(child, addr,
 615                                         (struct user_desc __user *) data);
 616                 break;
 617
 618         case PTRACE_SET_THREAD_AREA:
 619                 ret = ptrace_set_thread_area(child, addr,
 620                                         (struct user_desc __user *) data);
 621                 break;
 622
 623         default:
 624                 ret = ptrace_request(child, request, addr, data);
 625                 break;
 626         }
 627  out_tsk:
 628         return ret;
 629 }
 630
 631 void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, int error_code)
 632 {
 633         struct siginfo info;
 634
 635         tsk->thread.trap_no = 1;
 636         tsk->thread.error_code = error_code;
 637
 638         memset(&info, 0, sizeof(info));
 639         info.si_signo = SIGTRAP;
 640         info.si_code = TRAP_BRKPT;
 641
 642         /* User-mode eip? */
 643         info.si_addr = user_mode_vm(regs) ? (void __user *) regs->eip : NULL;
 644
 645         /* Send us the fakey SIGTRAP */
 646         force_sig_info(SIGTRAP, &info, tsk);
 647 }
 648
 649 /* notification of system call entry/exit
 650  * - triggered by current->work.syscall_trace
 651  */
 652 __attribute__((regparm(3)))
 653 int do_syscall_trace(struct pt_regs *regs, int entryexit)
 654 {
 655         int is_sysemu = test_thread_flag(TIF_SYSCALL_EMU);
 656         /*
 657          * With TIF_SYSCALL_EMU set we want to ignore TIF_SINGLESTEP for syscall
 658          * interception
 659          */
 660         int is_singlestep = !is_sysemu && test_thread_flag(TIF_SINGLESTEP);
 661         int ret = 0;
 662
 663         /* do the secure computing check first */
 664         if (!entryexit)
 665                 secure_computing(regs->orig_eax);
 666
 667         if (unlikely(current->audit_context)) {
 668                 if (entryexit)
 669                         audit_syscall_exit(AUDITSC_RESULT(regs->eax),
 670                                                 regs->eax);
 671                 /* Debug traps, when using PTRACE_SINGLESTEP, must be sent only
 672                  * on the syscall exit path. Normally, when TIF_SYSCALL_AUDIT is
 673                  * not used, entry.S will call us only on syscall exit, not
 674                  * entry; so when TIF_SYSCALL_AUDIT is used we must avoid
 675                  * calling send_sigtrap() on syscall entry.
 676                  *
 677                  * Note that when PTRACE_SYSEMU_SINGLESTEP is used,
 678                  * is_singlestep is false, despite his name, so we will still do
 679                  * the correct thing.
 680                  */
 681                 else if (is_singlestep)
 682                         goto out;
 683         }
 684
 685         if (!(current->ptrace & PT_PTRACED))
 686                 goto out;
 687
 688         /* If a process stops on the 1st tracepoint with SYSCALL_TRACE
 689          * and then is resumed with SYSEMU_SINGLESTEP, it will come in
 690          * here. We have to check this and return */
 691         if (is_sysemu && entryexit)
 692                 return 0;
 693
 694         /* Fake a debug trap */
 695         if (is_singlestep)
 696                 send_sigtrap(current, regs, 0);
 697
 698         if (!test_thread_flag(TIF_SYSCALL_TRACE) && !is_sysemu)
 699                 goto out;
 700
 701         /* the 0x80 provides a way for the tracing parent to distinguish
 702            between a syscall stop and SIGTRAP delivery */
 703         /* Note that the debugger could change the result of test_thread_flag!*/
 704         ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD) ? 0x80:0));
 705
 706         /*
 707          * this isn't the same as continuing with a signal, but it will do
 708          * for normal use.  strace only continues with a signal if the
 709          * stopping signal is not SIGTRAP.  -brl
 710          */
 711         if (current->exit_code) {
 712                 send_sig(current->exit_code, current, 1);
 713                 current->exit_code = 0;
 714         }
 715         ret = is_sysemu;
 716 out:
 717         if (unlikely(current->audit_context) && !entryexit)
 718                 audit_syscall_entry(AUDIT_ARCH_I386, regs->orig_eax,
 719                                     regs->ebx, regs->ecx, regs->edx, regs->esi);
 720         if (ret == 0)
 721                 return 0;
 722
 723         regs->orig_eax = -1; /* force skip of syscall restarting */
 724         if (unlikely(current->audit_context))
 725                 audit_syscall_exit(AUDITSC_RESULT(regs->eax), regs->eax);
 726         return 1;
 727 }