arch/i386/kernel/ptrace.c

   1 /* ptrace.c */
   2 /* By Ross Biro 1/23/92 */
   3 /* edited by Linus Torvalds */
   4
   5 #include <linux/config.h> /* for CONFIG_MATH_EMULATION */
   6 #include <linux/kernel.h>
   7 #include <linux/sched.h>
   8 #include <linux/mm.h>
   9 #include <linux/smp.h>
  10 #include <linux/smp_lock.h>
  11 #include <linux/errno.h>
  12 #include <linux/ptrace.h>
  13 #include <linux/user.h>
  14
  15 #include <asm/uaccess.h>
  16 #include <asm/pgtable.h>
  17 #include <asm/system.h>
  18 #include <asm/processor.h>
  19 #include <asm/debugreg.h>
  20
  21 /*
  22  * does not yet catch signals sent when the child dies.
  23  * in exit.c or in signal.c.
  24  */
  25
  26 /* determines which flags the user has access to. */
  27 /* 1 = access 0 = no access */
  28 #define FLAG_MASK 0x00044dd5
  29
  30 /* set's the trap flag. */
  31 #define TRAP_FLAG 0x100
  32
  33 /*
  34  * Offset of eflags on child stack..
  35  */
  36 #define EFL_OFFSET ((EFL-2)*4-sizeof(struct pt_regs))
  37
  38 /*
  39  * this routine will get a word off of the processes privileged stack.
  40  * the offset is how far from the base addr as stored in the TSS.
  41  * this routine assumes that all the privileged stacks are in our
  42  * data space.
  43  */
  44 static inline int get_stack_long(struct task_struct *task, int offset)
  45 {
  46         unsigned char *stack;
  47
  48         stack = (unsigned char *)task->thread.esp0;
  49         stack += offset;
  50         return (*((int *)stack));
  51 }
  52
  53 /*
  54  * this routine will put a word on the processes privileged stack.
  55  * the offset is how far from the base addr as stored in the TSS.
  56  * this routine assumes that all the privileged stacks are in our
  57  * data space.
  58  */
  59 static inline int put_stack_long(struct task_struct *task, int offset,
  60         unsigned long data)
  61 {
  62         unsigned char * stack;
  63
  64         stack = (unsigned char *) task->thread.esp0;
  65         stack += offset;
  66         *(unsigned long *) stack = data;
  67         return 0;
  68 }
  69
  70 static int putreg(struct task_struct *child,
  71         unsigned long regno, unsigned long value)
  72 {
  73         switch (regno >> 2) {
  74                 case FS:
  75                         if (value && (value & 3) != 3)
  76                                 return -EIO;
  77                         child->thread.fs = value;
  78                         return 0;
  79                 case GS:
  80                         if (value && (value & 3) != 3)
  81                                 return -EIO;
  82                         child->thread.gs = value;
  83                         return 0;
  84                 case DS:
  85                 case ES:
  86                         if (value && (value & 3) != 3)
  87                                 return -EIO;
  88                         value &= 0xffff;
  89                         break;
  90                 case SS:
  91                 case CS:
  92                         if ((value & 3) != 3)
  93                                 return -EIO;
  94                         value &= 0xffff;
  95                         break;
  96                 case EFL:
  97                         value &= FLAG_MASK;
  98                         value |= get_stack_long(child, EFL_OFFSET) & ~FLAG_MASK;
  99         }
 100         if (regno > GS*4)
 101                 regno -= 2*4;
 102         put_stack_long(child, regno - sizeof(struct pt_regs), value);
 103         return 0;
 104 }
 105
 106 static unsigned long getreg(struct task_struct *child,
 107         unsigned long regno)
 108 {
 109         unsigned long retval = ~0UL;
 110
 111         switch (regno >> 2) {
 112                 case FS:
 113                         retval = child->thread.fs;
 114                         break;
 115                 case GS:
 116                         retval = child->thread.gs;
 117                         break;
 118                 case DS:
 119                 case ES:
 120                 case SS:
 121                 case CS:
 122                         retval = 0xffff;
 123                         /* fall through */
 124                 default:
 125                         if (regno > GS*4)
 126                                 regno -= 2*4;
 127                         regno = regno - sizeof(struct pt_regs);
 128                         retval &= get_stack_long(child, regno);
 129         }
 130         return retval;
 131 }
 132
 133 asmlinkage int sys_ptrace(long request, long pid, long addr, long data)
 134 {
 135         struct task_struct *child;
 136         struct user * dummy = NULL;
 137         unsigned long flags;
 138         int i, ret;
 139
 140         lock_kernel();
 141         ret = -EPERM;
 142         if (request == PTRACE_TRACEME) {
 143                 /* are we already being traced? */
 144                 if (current->flags & PF_PTRACED)
 145                         goto out;
 146                 /* set the ptrace bit in the process flags. */
 147                 current->flags |= PF_PTRACED;
 148                 ret = 0;
 149                 goto out;
 150         }
 151         ret = -ESRCH;
 152         read_lock(&tasklist_lock);
 153         child = find_task_by_pid(pid);
 154         read_unlock(&tasklist_lock);    /* FIXME!!! */
 155         if (!child)
 156                 goto out;
 157         ret = -EPERM;
 158         if (pid == 1)           /* you may not mess with init */
 159                 goto out;
 160         if (request == PTRACE_ATTACH) {
 161                 if (child == current)
 162                         goto out;
 163                 if ((!child->dumpable ||
 164                     (current->uid != child->euid) ||
 165                     (current->uid != child->suid) ||
 166                     (current->uid != child->uid) ||
 167                     (current->gid != child->egid) ||
 168                     (current->gid != child->sgid) ||
 169                     (!cap_issubset(child->cap_permitted, current->cap_permitted)) ||
 170                     (current->gid != child->gid)) && !capable(CAP_SYS_PTRACE))
 171                         goto out;
 172                 /* the same process cannot be attached many times */
 173                 if (child->flags & PF_PTRACED)
 174                         goto out;
 175                 child->flags |= PF_PTRACED;
 176
 177                 write_lock_irqsave(&tasklist_lock, flags);
 178                 if (child->p_pptr != current) {
 179                         REMOVE_LINKS(child);
 180                         child->p_pptr = current;
 181                         SET_LINKS(child);
 182                 }
 183                 write_unlock_irqrestore(&tasklist_lock, flags);
 184
 185                 send_sig(SIGSTOP, child, 1);
 186                 ret = 0;
 187                 goto out;
 188         }
 189         ret = -ESRCH;
 190         if (!(child->flags & PF_PTRACED))
 191                 goto out;
 192         if (child->state != TASK_STOPPED) {
 193                 if (request != PTRACE_KILL)
 194                         goto out;
 195         }
 196         if (child->p_pptr != current)
 197                 goto out;
 198
 199         switch (request) {
 200         /* when I and D space are separate, these will need to be fixed. */
 201         case PTRACE_PEEKTEXT: /* read word at location addr. */
 202         case PTRACE_PEEKDATA: {
 203                 unsigned long tmp;
 204                 int copied;
 205
 206                 copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
 207                 ret = -EIO;
 208                 if (copied != sizeof(tmp))
 209                         break;
 210                 ret = put_user(tmp,(unsigned long *) data);
 211                 break;
 212         }
 213
 214         /* read the word at location addr in the USER area. */
 215         case PTRACE_PEEKUSR: {
 216                 unsigned long tmp;
 217
 218                 ret = -EIO;
 219                 if ((addr & 3) || addr < 0 ||
 220                     addr > sizeof(struct user) - 3)
 221                         break;
 222
 223                 tmp = 0;  /* Default return condition */
 224                 if(addr < 17*sizeof(long))
 225                         tmp = getreg(child, addr);
 226                 if(addr >= (long) &dummy->u_debugreg[0] &&
 227                    addr <= (long) &dummy->u_debugreg[7]){
 228                         addr -= (long) &dummy->u_debugreg[0];
 229                         addr = addr >> 2;
 230                         tmp = child->thread.debugreg[addr];
 231                 }
 232                 ret = put_user(tmp,(unsigned long *) data);
 233                 break;
 234         }
 235
 236         /* when I and D space are separate, this will have to be fixed. */
 237         case PTRACE_POKETEXT: /* write the word at location addr. */
 238         case PTRACE_POKEDATA:
 239                 ret = 0;
 240                 if (access_process_vm(child, addr, &data, sizeof(data), 1) == sizeof(data))
 241                         break;
 242                 ret = -EIO;
 243                 break;
 244
 245         case PTRACE_POKEUSR: /* write the word at location addr in the USER area */
 246                 ret = -EIO;
 247                 if ((addr & 3) || addr < 0 ||
 248                     addr > sizeof(struct user) - 3)
 249                         break;
 250
 251                 if (addr < 17*sizeof(long)) {
 252                         ret = putreg(child, addr, data);
 253                         break;
 254                 }
 255                 /* We need to be very careful here.  We implicitly
 256                    want to modify a portion of the task_struct, and we
 257                    have to be selective about what portions we allow someone
 258                    to modify. */
 259
 260                   ret = -EIO;
 261                   if(addr >= (long) &dummy->u_debugreg[0] &&
 262                      addr <= (long) &dummy->u_debugreg[7]){
 263
 264                           if(addr == (long) &dummy->u_debugreg[4]) break;
 265                           if(addr == (long) &dummy->u_debugreg[5]) break;
 266                           if(addr < (long) &dummy->u_debugreg[4] &&
 267                              ((unsigned long) data) >= TASK_SIZE-3) break;
 268
 269                           if(addr == (long) &dummy->u_debugreg[7]) {
 270                                   data &= ~DR_CONTROL_RESERVED;
 271                                   for(i=0; i<4; i++)
 272                                           if ((0x5f54 >> ((data >> (16 + 4*i)) & 0xf)) & 1)
 273                                                   goto out;
 274                           }
 275
 276                           addr -= (long) &dummy->u_debugreg;
 277                           addr = addr >> 2;
 278                           child->thread.debugreg[addr] = data;
 279                           ret = 0;
 280                   }
 281                   break;
 282
 283         case PTRACE_SYSCALL: /* continue and stop at next (return from) syscall */
 284         case PTRACE_CONT: { /* restart after signal. */
 285                 long tmp;
 286
 287                 ret = -EIO;
 288                 if ((unsigned long) data > _NSIG)
 289                         break;
 290                 if (request == PTRACE_SYSCALL)
 291                         child->flags |= PF_TRACESYS;
 292                 else
 293                         child->flags &= ~PF_TRACESYS;
 294                 child->exit_code = data;
 295         /* make sure the single step bit is not set. */
 296                 tmp = get_stack_long(child, EFL_OFFSET) & ~TRAP_FLAG;
 297                 put_stack_long(child, EFL_OFFSET,tmp);
 298                 wake_up_process(child);
 299                 ret = 0;
 300                 break;
 301         }
 302
 303 /*
 304  * make the child exit.  Best I can do is send it a sigkill.
 305  * perhaps it should be put in the status that it wants to
 306  * exit.
 307  */
 308         case PTRACE_KILL: {
 309                 long tmp;
 310
 311                 ret = 0;
 312                 if (child->state == TASK_ZOMBIE)        /* already dead */
 313                         break;
 314                 child->exit_code = SIGKILL;
 315                 /* make sure the single step bit is not set. */
 316                 tmp = get_stack_long(child, EFL_OFFSET) & ~TRAP_FLAG;
 317                 put_stack_long(child, EFL_OFFSET, tmp);
 318                 wake_up_process(child);
 319                 break;
 320         }
 321
 322         case PTRACE_SINGLESTEP: {  /* set the trap flag. */
 323                 long tmp;
 324
 325                 ret = -EIO;
 326                 if ((unsigned long) data > _NSIG)
 327                         break;
 328                 child->flags &= ~PF_TRACESYS;
 329                 if ((child->flags & PF_DTRACE) == 0) {
 330                         /* Spurious delayed TF traps may occur */
 331                         child->flags |= PF_DTRACE;
 332                 }
 333                 tmp = get_stack_long(child, EFL_OFFSET) | TRAP_FLAG;
 334                 put_stack_long(child, EFL_OFFSET, tmp);
 335                 child->exit_code = data;
 336                 /* give it a chance to run. */
 337                 wake_up_process(child);
 338                 ret = 0;
 339                 break;
 340         }
 341
 342         case PTRACE_DETACH: { /* detach a process that was attached. */
 343                 long tmp;
 344
 345                 ret = -EIO;
 346                 if ((unsigned long) data > _NSIG)
 347                         break;
 348                 child->flags &= ~(PF_PTRACED|PF_TRACESYS);
 349                 child->exit_code = data;
 350                 write_lock_irqsave(&tasklist_lock, flags);
 351                 REMOVE_LINKS(child);
 352                 child->p_pptr = child->p_opptr;
 353                 SET_LINKS(child);
 354                 write_unlock_irqrestore(&tasklist_lock, flags);
 355                 /* make sure the single step bit is not set. */
 356                 tmp = get_stack_long(child, EFL_OFFSET) & ~TRAP_FLAG;
 357                 put_stack_long(child, EFL_OFFSET, tmp);
 358                 wake_up_process(child);
 359                 ret = 0;
 360                 break;
 361         }
 362
 363         case PTRACE_GETREGS: { /* Get all gp regs from the child. */
 364                 if (!access_ok(VERIFY_WRITE, (unsigned *)data, 17*sizeof(long))) {
 365                         ret = -EIO;
 366                         break;
 367                 }
 368                 for ( i = 0; i < 17*sizeof(long); i += sizeof(long) ) {
 369                         __put_user(getreg(child, i),(unsigned long *) data);
 370                         data += sizeof(long);
 371                 }
 372                 ret = 0;
 373                 break;
 374         }
 375
 376         case PTRACE_SETREGS: { /* Set all gp regs in the child. */
 377                 unsigned long tmp;
 378                 if (!access_ok(VERIFY_READ, (unsigned *)data, 17*sizeof(long))) {
 379                         ret = -EIO;
 380                         break;
 381                 }
 382                 for ( i = 0; i < 17*sizeof(long); i += sizeof(long) ) {
 383                         __get_user(tmp, (unsigned long *) data);
 384                         putreg(child, i, tmp);
 385                         data += sizeof(long);
 386                 }
 387                 ret = 0;
 388                 break;
 389         }
 390
 391         case PTRACE_GETFPREGS: { /* Get the child FPU state. */
 392                 if (!access_ok(VERIFY_WRITE, (unsigned *)data, sizeof(struct user_i387_struct))) {
 393                         ret = -EIO;
 394                         break;
 395                 }
 396                 ret = 0;
 397                 if ( !child->used_math ) {
 398                         /* Simulate an empty FPU. */
 399                         child->thread.i387.hard.cwd = 0xffff037f;
 400                         child->thread.i387.hard.swd = 0xffff0000;
 401                         child->thread.i387.hard.twd = 0xffffffff;
 402                 }
 403 #ifdef CONFIG_MATH_EMULATION
 404                 if ( boot_cpu_data.hard_math ) {
 405 #endif
 406                         __copy_to_user((void *)data, &child->thread.i387.hard, sizeof(struct user_i387_struct));
 407 #ifdef CONFIG_MATH_EMULATION
 408                 } else {
 409                         save_i387_soft(&child->thread.i387.soft, (struct _fpstate *)data);
 410                 }
 411 #endif
 412                 break;
 413         }
 414
 415         case PTRACE_SETFPREGS: { /* Set the child FPU state. */
 416                 if (!access_ok(VERIFY_READ, (unsigned *)data, sizeof(struct user_i387_struct))) {
 417                         ret = -EIO;
 418                         break;
 419                 }
 420                 child->used_math = 1;
 421 #ifdef CONFIG_MATH_EMULATION
 422                 if ( boot_cpu_data.hard_math ) {
 423 #endif
 424                         __copy_from_user(&child->thread.i387.hard, (void *)data, sizeof(struct user_i387_struct));
 425 #ifdef CONFIG_MATH_EMULATION
 426                 } else {
 427                         restore_i387_soft(&child->thread.i387.soft, (struct _fpstate *)data);
 428                 }
 429 #endif
 430                 ret = 0;
 431                 break;
 432         }
 433
 434         default:
 435                 ret = -EIO;
 436                 break;
 437         }
 438 out:
 439         unlock_kernel();
 440         return ret;
 441 }
 442
 443 asmlinkage void syscall_trace(void)
 444 {
 445         if ((current->flags & (PF_PTRACED|PF_TRACESYS))
 446                         != (PF_PTRACED|PF_TRACESYS))
 447                 return;
 448         current->exit_code = SIGTRAP;
 449         current->state = TASK_STOPPED;
 450         notify_parent(current, SIGCHLD);
 451         schedule();
 452         /*
 453          * this isn't the same as continuing with a signal, but it will do
 454          * for normal use.  strace only continues with a signal if the
 455          * stopping signal is not SIGTRAP.  -brl
 456          */
 457         if (current->exit_code) {
 458                 send_sig(current->exit_code, current, 1);
 459                 current->exit_code = 0;
 460         }
 461 }