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