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
  19 #include <asm/uaccess.h>
  20 #include <asm/pgtable.h>
  21 #include <asm/system.h>
  22 #include <asm/processor.h>
  23 #include <asm/i387.h>
  24 #include <asm/debugreg.h>
  25 #include <asm/ldt.h>
  26 #include <asm/desc.h>
  27
  28 /*
  29  * does not yet catch signals sent when the child dies.
  30  * in exit.c or in signal.c.
  31  */
  32
  33 /* determines which flags the user has access to. */
  34 /* 1 = access 0 = no access */
  35 #define FLAG_MASK 0x00044dd5
  36
  37 /* set's the trap flag. */
  38 #define TRAP_FLAG 0x100
  39
  40 /*
  41  * Offset of eflags on child stack..
  42  */
  43 #define EFL_OFFSET ((EFL-2)*4-sizeof(struct pt_regs))
  44
  45 /*
  46  * this routine will get a word off of the processes privileged stack.
  47  * the offset is how far from the base addr as stored in the TSS.
  48  * this routine assumes that all the privileged stacks are in our
  49  * data space.
  50  */
  51 static inline int get_stack_long(struct task_struct *task, int offset)
  52 {
  53         unsigned char *stack;
  54
  55         stack = (unsigned char *)task->thread.esp0;
  56         stack += offset;
  57         return (*((int *)stack));
  58 }
  59
  60 /*
  61  * this routine will put a word on the processes privileged stack.
  62  * the offset is how far from the base addr as stored in the TSS.
  63  * this routine assumes that all the privileged stacks are in our
  64  * data space.
  65  */
  66 static inline int put_stack_long(struct task_struct *task, int offset,
  67         unsigned long data)
  68 {
  69         unsigned char * stack;
  70
  71         stack = (unsigned char *) task->thread.esp0;
  72         stack += offset;
  73         *(unsigned long *) stack = data;
  74         return 0;
  75 }
  76
  77 static int putreg(struct task_struct *child,
  78         unsigned long regno, unsigned long value)
  79 {
  80         switch (regno >> 2) {
  81                 case FS:
  82                         if (value && (value & 3) != 3)
  83                                 return -EIO;
  84                         child->thread.fs = value;
  85                         return 0;
  86                 case GS:
  87                         if (value && (value & 3) != 3)
  88                                 return -EIO;
  89                         child->thread.gs = value;
  90                         return 0;
  91                 case DS:
  92                 case ES:
  93                         if (value && (value & 3) != 3)
  94                                 return -EIO;
  95                         value &= 0xffff;
  96                         break;
  97                 case SS:
  98                 case CS:
  99                         if ((value & 3) != 3)
 100                                 return -EIO;
 101                         value &= 0xffff;
 102                         break;
 103                 case EFL:
 104                         value &= FLAG_MASK;
 105                         value |= get_stack_long(child, EFL_OFFSET) & ~FLAG_MASK;
 106                         break;
 107         }
 108         if (regno > GS*4)
 109                 regno -= 2*4;
 110         put_stack_long(child, regno - sizeof(struct pt_regs), value);
 111         return 0;
 112 }
 113
 114 static unsigned long getreg(struct task_struct *child,
 115         unsigned long regno)
 116 {
 117         unsigned long retval = ~0UL;
 118
 119         switch (regno >> 2) {
 120                 case FS:
 121                         retval = child->thread.fs;
 122                         break;
 123                 case GS:
 124                         retval = child->thread.gs;
 125                         break;
 126                 case DS:
 127                 case ES:
 128                 case SS:
 129                 case CS:
 130                         retval = 0xffff;
 131                         /* fall through */
 132                 default:
 133                         if (regno > GS*4)
 134                                 regno -= 2*4;
 135                         regno = regno - sizeof(struct pt_regs);
 136                         retval &= get_stack_long(child, regno);
 137         }
 138         return retval;
 139 }
 140
 141 /*
 142  * Called by kernel/ptrace.c when detaching..
 143  *
 144  * Make sure the single step bit is not set.
 145  */
 146 void ptrace_disable(struct task_struct *child)
 147 {
 148         long tmp;
 149
 150         clear_tsk_thread_flag(child, TIF_SINGLESTEP);
 151         tmp = get_stack_long(child, EFL_OFFSET) & ~TRAP_FLAG;
 152         put_stack_long(child, EFL_OFFSET, tmp);
 153 }
 154
 155 /*
 156  * Perform get_thread_area on behalf of the traced child.
 157  */
 158 static int
 159 ptrace_get_thread_area(struct task_struct *child,
 160                        int idx, struct user_desc __user *user_desc)
 161 {
 162         struct user_desc info;
 163         struct desc_struct *desc;
 164
 165 /*
 166  * Get the current Thread-Local Storage area:
 167  */
 168
 169 #define GET_BASE(desc) ( \
 170         (((desc)->a >> 16) & 0x0000ffff) | \
 171         (((desc)->b << 16) & 0x00ff0000) | \
 172         ( (desc)->b        & 0xff000000)   )
 173
 174 #define GET_LIMIT(desc) ( \
 175         ((desc)->a & 0x0ffff) | \
 176          ((desc)->b & 0xf0000) )
 177
 178 #define GET_32BIT(desc)         (((desc)->b >> 22) & 1)
 179 #define GET_CONTENTS(desc)      (((desc)->b >> 10) & 3)
 180 #define GET_WRITABLE(desc)      (((desc)->b >>  9) & 1)
 181 #define GET_LIMIT_PAGES(desc)   (((desc)->b >> 23) & 1)
 182 #define GET_PRESENT(desc)       (((desc)->b >> 15) & 1)
 183 #define GET_USEABLE(desc)       (((desc)->b >> 20) & 1)
 184
 185         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
 186                 return -EINVAL;
 187
 188         desc = child->thread.tls_array + idx - GDT_ENTRY_TLS_MIN;
 189
 190         info.entry_number = idx;
 191         info.base_addr = GET_BASE(desc);
 192         info.limit = GET_LIMIT(desc);
 193         info.seg_32bit = GET_32BIT(desc);
 194         info.contents = GET_CONTENTS(desc);
 195         info.read_exec_only = !GET_WRITABLE(desc);
 196         info.limit_in_pages = GET_LIMIT_PAGES(desc);
 197         info.seg_not_present = !GET_PRESENT(desc);
 198         info.useable = GET_USEABLE(desc);
 199
 200         if (copy_to_user(user_desc, &info, sizeof(info)))
 201                 return -EFAULT;
 202
 203         return 0;
 204 }
 205
 206 /*
 207  * Perform set_thread_area on behalf of the traced child.
 208  */
 209 static int
 210 ptrace_set_thread_area(struct task_struct *child,
 211                        int idx, struct user_desc __user *user_desc)
 212 {
 213         struct user_desc info;
 214         struct desc_struct *desc;
 215
 216         if (copy_from_user(&info, user_desc, sizeof(info)))
 217                 return -EFAULT;
 218
 219         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
 220                 return -EINVAL;
 221
 222         desc = child->thread.tls_array + idx - GDT_ENTRY_TLS_MIN;
 223         if (LDT_empty(&info)) {
 224                 desc->a = 0;
 225                 desc->b = 0;
 226         } else {
 227                 desc->a = LDT_entry_a(&info);
 228                 desc->b = LDT_entry_b(&info);
 229         }
 230
 231         return 0;
 232 }
 233
 234 asmlinkage int sys_ptrace(long request, long pid, long addr, long data)
 235 {
 236         struct task_struct *child;
 237         struct user * dummy = NULL;
 238         int i, ret;
 239         unsigned long __user *datap = (unsigned long __user *)data;
 240
 241         lock_kernel();
 242         ret = -EPERM;
 243         if (request == PTRACE_TRACEME) {
 244                 /* are we already being traced? */
 245                 if (current->ptrace & PT_PTRACED)
 246                         goto out;
 247                 ret = security_ptrace(current->parent, current);
 248                 if (ret)
 249                         goto out;
 250                 /* set the ptrace bit in the process flags. */
 251                 current->ptrace |= PT_PTRACED;
 252                 ret = 0;
 253                 goto out;
 254         }
 255         ret = -ESRCH;
 256         read_lock(&tasklist_lock);
 257         child = find_task_by_pid(pid);
 258         if (child)
 259                 get_task_struct(child);
 260         read_unlock(&tasklist_lock);
 261         if (!child)
 262                 goto out;
 263
 264         ret = -EPERM;
 265         if (pid == 1)           /* you may not mess with init */
 266                 goto out_tsk;
 267
 268         if (request == PTRACE_ATTACH) {
 269                 ret = ptrace_attach(child);
 270                 goto out_tsk;
 271         }
 272
 273         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 274         if (ret < 0)
 275                 goto out_tsk;
 276
 277         switch (request) {
 278         /* when I and D space are separate, these will need to be fixed. */
 279         case PTRACE_PEEKTEXT: /* read word at location addr. */
 280         case PTRACE_PEEKDATA: {
 281                 unsigned long tmp;
 282                 int copied;
 283
 284                 copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
 285                 ret = -EIO;
 286                 if (copied != sizeof(tmp))
 287                         break;
 288                 ret = put_user(tmp, datap);
 289                 break;
 290         }
 291
 292         /* read the word at location addr in the USER area. */
 293         case PTRACE_PEEKUSR: {
 294                 unsigned long tmp;
 295
 296                 ret = -EIO;
 297                 if ((addr & 3) || addr < 0 ||
 298                     addr > sizeof(struct user) - 3)
 299                         break;
 300
 301                 tmp = 0;  /* Default return condition */
 302                 if(addr < FRAME_SIZE*sizeof(long))
 303                         tmp = getreg(child, addr);
 304                 if(addr >= (long) &dummy->u_debugreg[0] &&
 305                    addr <= (long) &dummy->u_debugreg[7]){
 306                         addr -= (long) &dummy->u_debugreg[0];
 307                         addr = addr >> 2;
 308                         tmp = child->thread.debugreg[addr];
 309                 }
 310                 ret = put_user(tmp, datap);
 311                 break;
 312         }
 313
 314         /* when I and D space are separate, this will have to be fixed. */
 315         case PTRACE_POKETEXT: /* write the word at location addr. */
 316         case PTRACE_POKEDATA:
 317                 ret = 0;
 318                 if (access_process_vm(child, addr, &data, sizeof(data), 1) == sizeof(data))
 319                         break;
 320                 ret = -EIO;
 321                 break;
 322
 323         case PTRACE_POKEUSR: /* write the word at location addr in the USER area */
 324                 ret = -EIO;
 325                 if ((addr & 3) || addr < 0 ||
 326                     addr > sizeof(struct user) - 3)
 327                         break;
 328
 329                 if (addr < FRAME_SIZE*sizeof(long)) {
 330                         ret = putreg(child, addr, data);
 331                         break;
 332                 }
 333                 /* We need to be very careful here.  We implicitly
 334                    want to modify a portion of the task_struct, and we
 335                    have to be selective about what portions we allow someone
 336                    to modify. */
 337
 338                   ret = -EIO;
 339                   if(addr >= (long) &dummy->u_debugreg[0] &&
 340                      addr <= (long) &dummy->u_debugreg[7]){
 341
 342                           if(addr == (long) &dummy->u_debugreg[4]) break;
 343                           if(addr == (long) &dummy->u_debugreg[5]) break;
 344                           if(addr < (long) &dummy->u_debugreg[4] &&
 345                              ((unsigned long) data) >= TASK_SIZE-3) break;
 346
 347                           if(addr == (long) &dummy->u_debugreg[7]) {
 348                                   data &= ~DR_CONTROL_RESERVED;
 349                                   for(i=0; i<4; i++)
 350                                           if ((0x5f54 >> ((data >> (16 + 4*i)) & 0xf)) & 1)
 351                                                   goto out_tsk;
 352                           }
 353
 354                           addr -= (long) &dummy->u_debugreg;
 355                           addr = addr >> 2;
 356                           child->thread.debugreg[addr] = data;
 357                           ret = 0;
 358                   }
 359                   break;
 360
 361         case PTRACE_SYSCALL: /* continue and stop at next (return from) syscall */
 362         case PTRACE_CONT: { /* restart after signal. */
 363                 long tmp;
 364
 365                 ret = -EIO;
 366                 if ((unsigned long) data > _NSIG)
 367                         break;
 368                 if (request == PTRACE_SYSCALL) {
 369                         set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 370                 }
 371                 else {
 372                         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 373                 }
 374                 clear_tsk_thread_flag(child, TIF_SINGLESTEP);
 375                 child->exit_code = data;
 376         /* make sure the single step bit is not set. */
 377                 tmp = get_stack_long(child, EFL_OFFSET) & ~TRAP_FLAG;
 378                 put_stack_long(child, EFL_OFFSET,tmp);
 379                 wake_up_process(child);
 380                 ret = 0;
 381                 break;
 382         }
 383
 384 /*
 385  * make the child exit.  Best I can do is send it a sigkill.
 386  * perhaps it should be put in the status that it wants to
 387  * exit.
 388  */
 389         case PTRACE_KILL: {
 390                 long tmp;
 391
 392                 ret = 0;
 393                 if (child->state == TASK_ZOMBIE)        /* already dead */
 394                         break;
 395                 child->exit_code = SIGKILL;
 396                 clear_tsk_thread_flag(child, TIF_SINGLESTEP);
 397                 /* make sure the single step bit is not set. */
 398                 tmp = get_stack_long(child, EFL_OFFSET) & ~TRAP_FLAG;
 399                 put_stack_long(child, EFL_OFFSET, tmp);
 400                 wake_up_process(child);
 401                 break;
 402         }
 403
 404         case PTRACE_SINGLESTEP: {  /* set the trap flag. */
 405                 long tmp;
 406
 407                 ret = -EIO;
 408                 if ((unsigned long) data > _NSIG)
 409                         break;
 410                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 411                 if ((child->ptrace & PT_DTRACE) == 0) {
 412                         /* Spurious delayed TF traps may occur */
 413                         child->ptrace |= PT_DTRACE;
 414                 }
 415                 tmp = get_stack_long(child, EFL_OFFSET) | TRAP_FLAG;
 416                 put_stack_long(child, EFL_OFFSET, tmp);
 417                 set_tsk_thread_flag(child, TIF_SINGLESTEP);
 418                 child->exit_code = data;
 419                 /* give it a chance to run. */
 420                 wake_up_process(child);
 421                 ret = 0;
 422                 break;
 423         }
 424
 425         case PTRACE_DETACH:
 426                 /* detach a process that was attached. */
 427                 ret = ptrace_detach(child, data);
 428                 break;
 429
 430         case PTRACE_GETREGS: { /* Get all gp regs from the child. */
 431                 if (!access_ok(VERIFY_WRITE, datap, FRAME_SIZE*sizeof(long))) {
 432                         ret = -EIO;
 433                         break;
 434                 }
 435                 for ( i = 0; i < FRAME_SIZE*sizeof(long); i += sizeof(long) ) {
 436                         __put_user(getreg(child, i), datap);
 437                         datap++;
 438                 }
 439                 ret = 0;
 440                 break;
 441         }
 442
 443         case PTRACE_SETREGS: { /* Set all gp regs in the child. */
 444                 unsigned long tmp;
 445                 if (!access_ok(VERIFY_READ, datap, FRAME_SIZE*sizeof(long))) {
 446                         ret = -EIO;
 447                         break;
 448                 }
 449                 for ( i = 0; i < FRAME_SIZE*sizeof(long); i += sizeof(long) ) {
 450                         __get_user(tmp, datap);
 451                         putreg(child, i, tmp);
 452                         datap++;
 453                 }
 454                 ret = 0;
 455                 break;
 456         }
 457
 458         case PTRACE_GETFPREGS: { /* Get the child FPU state. */
 459                 if (!access_ok(VERIFY_WRITE, datap,
 460                                sizeof(struct user_i387_struct))) {
 461                         ret = -EIO;
 462                         break;
 463                 }
 464                 ret = 0;
 465                 if (!child->used_math)
 466                         init_fpu(child);
 467                 get_fpregs((struct user_i387_struct __user *)data, child);
 468                 break;
 469         }
 470
 471         case PTRACE_SETFPREGS: { /* Set the child FPU state. */
 472                 if (!access_ok(VERIFY_READ, datap,
 473                                sizeof(struct user_i387_struct))) {
 474                         ret = -EIO;
 475                         break;
 476                 }
 477                 child->used_math = 1;
 478                 set_fpregs(child, (struct user_i387_struct __user *)data);
 479                 ret = 0;
 480                 break;
 481         }
 482
 483         case PTRACE_GETFPXREGS: { /* Get the child extended FPU state. */
 484                 if (!access_ok(VERIFY_WRITE, datap,
 485                                sizeof(struct user_fxsr_struct))) {
 486                         ret = -EIO;
 487                         break;
 488                 }
 489                 if (!child->used_math)
 490                         init_fpu(child);
 491                 ret = get_fpxregs((struct user_fxsr_struct __user *)data, child);
 492                 break;
 493         }
 494
 495         case PTRACE_SETFPXREGS: { /* Set the child extended FPU state. */
 496                 if (!access_ok(VERIFY_READ, datap,
 497                                sizeof(struct user_fxsr_struct))) {
 498                         ret = -EIO;
 499                         break;
 500                 }
 501                 child->used_math = 1;
 502                 ret = set_fpxregs(child, (struct user_fxsr_struct __user *)data);
 503                 break;
 504         }
 505
 506         case PTRACE_GET_THREAD_AREA:
 507                 ret = ptrace_get_thread_area(child, addr,
 508                                         (struct user_desc __user *) data);
 509                 break;
 510
 511         case PTRACE_SET_THREAD_AREA:
 512                 ret = ptrace_set_thread_area(child, addr,
 513                                         (struct user_desc __user *) data);
 514                 break;
 515
 516         default:
 517                 ret = ptrace_request(child, request, addr, data);
 518                 break;
 519         }
 520 out_tsk:
 521         put_task_struct(child);
 522 out:
 523         unlock_kernel();
 524         return ret;
 525 }
 526
 527 /* notification of system call entry/exit
 528  * - triggered by current->work.syscall_trace
 529  */
 530 __attribute__((regparm(3)))
 531 void do_syscall_trace(struct pt_regs *regs, int entryexit)
 532 {
 533         if (unlikely(current->audit_context)) {
 534                 if (!entryexit)
 535                         audit_syscall_entry(current, regs->orig_eax,
 536                                             regs->ebx, regs->ecx,
 537                                             regs->edx, regs->esi);
 538                 else
 539                         audit_syscall_exit(current, regs->eax);
 540         }
 541
 542         if (!test_thread_flag(TIF_SYSCALL_TRACE) &&
 543             !test_thread_flag(TIF_SINGLESTEP))
 544                 return;
 545         if (!(current->ptrace & PT_PTRACED))
 546                 return;
 547         /* the 0x80 provides a way for the tracing parent to distinguish
 548            between a syscall stop and SIGTRAP delivery */
 549         ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD) &&
 550                                  !test_thread_flag(TIF_SINGLESTEP) ? 0x80 : 0));
 551
 552         /*
 553          * this isn't the same as continuing with a signal, but it will do
 554          * for normal use.  strace only continues with a signal if the
 555          * stopping signal is not SIGTRAP.  -brl
 556          */
 557         if (current->exit_code) {
 558                 send_sig(current->exit_code, current, 1);
 559                 current->exit_code = 0;
 560         }
 561 }