root/kernel/sys.c

/* */

DEFINITIONS

1. proc_sel
2. sys_setpriority
3. sys_getpriority
4. sys_profil
5. sys_ftime
6. sys_break
7. sys_stty
8. sys_gtty
9. sys_prof
10. sys_reboot
11. ctrl_alt_del
12. sys_setregid
13. sys_setgid
14. sys_acct
15. sys_phys
16. sys_lock
17. sys_mpx
18. sys_ulimit
19. sys_time
20. sys_setreuid
21. sys_setuid
22. sys_stime
23. sys_times
24. sys_brk
25. sys_setpgid
26. sys_getpgrp
27. sys_setsid
28. sys_getgroups
29. sys_setgroups
30. in_group_p
31. sys_uname
32. sys_sethostname
33. sys_getrlimit
34. sys_setrlimit
35. sys_getrusage
36. sys_gettimeofday
37. sys_settimeofday
38. adjust_clock
39. sys_umask

   1 /*
   2  *  linux/kernel/sys.c
   3  *
   4  *  (C) 1991  Linus Torvalds
   5  */
   6 
   7 #include <errno.h>
   8 
   9 #include <linux/sched.h>
  10 #include <linux/tty.h>
  11 #include <linux/kernel.h>
  12 #include <linux/config.h>
  13 #include <asm/segment.h>
  14 #include <sys/times.h>
  15 #include <sys/utsname.h>
  16 #include <sys/param.h>
  17 #include <sys/resource.h>
  18 #include <linux/string.h>
  19 
  20 /*
  21  * this indicates wether you can reboot with ctrl-alt-del: the deault is yes
  22  */
  23 static int C_A_D = 1;
  24 
  25 /* 
  26  * The timezone where the local system is located.  Used as a default by some
  27  * programs who obtain this value by using gettimeofday.
  28  */
  29 struct timezone sys_tz = { 0, 0};
  30 
  31 extern int session_of_pgrp(int pgrp);
  32 
  33 #define PZERO   15
  34 
  35 static int proc_sel(struct task_struct *p, int which, int who)
     /*  */
  36 {
  37         switch (which) {
  38                 case PRIO_PROCESS:
  39                         if (!who && p == current)
  40                                 return 1;
  41                         return(p->pid == who);
  42                 case PRIO_PGRP:
  43                         if (!who)
  44                                 who = current->pgrp;
  45                         return(p->pgrp == who);
  46                 case PRIO_USER:
  47                         if (!who)
  48                                 who = current->uid;
  49                         return(p->uid == who);
  50         }
  51         return 0;
  52 }
  53 
  54 int sys_setpriority(int which, int who, int niceval)
     /*  */
  55 {
  56         struct task_struct **p;
  57         int error = ESRCH;
  58         int priority;
  59 
  60         if (which > 2 || which < 0)
  61                 return -EINVAL;
  62 
  63         if ((priority = PZERO - niceval) <= 0)
  64                 priority = 1;
  65 
  66         for(p = &LAST_TASK; p > &FIRST_TASK; --p) {
  67                 if (!*p || !proc_sel(*p, which, who))
  68                         continue;
  69                 if ((*p)->uid != current->euid &&
  70                         (*p)->uid != current->uid && !suser()) {
  71                         error = EPERM;
  72                         continue;
  73                 }
  74                 if (error == ESRCH)
  75                         error = 0;
  76                 if (priority > (*p)->priority && !suser())
  77                         error = EACCES;
  78                 else
  79                         (*p)->priority = priority;
  80         }
  81         return -error;
  82 }
  83 
  84 int sys_getpriority(int which, int who)
     /*  */
  85 {
  86         struct task_struct **p;
  87         int max_prio = 0;
  88 
  89         if (which > 2 || which < 0)
  90                 return -EINVAL;
  91 
  92         for(p = &LAST_TASK; p > &FIRST_TASK; --p) {
  93                 if (!*p || !proc_sel(*p, which, who))
  94                         continue;
  95                 if ((*p)->priority > max_prio)
  96                         max_prio = (*p)->priority;
  97         }
  98         return(max_prio ? max_prio : -ESRCH);
  99 }
 100 
 101 int sys_profil()
     /*  */
 102 {
 103         return -ENOSYS;
 104 }
 105 
 106 int sys_ftime()
     /*  */
 107 {
 108         return -ENOSYS;
 109 }
 110 
 111 int sys_break()
     /*  */
 112 {
 113         return -ENOSYS;
 114 }
 115 
 116 int sys_stty()
     /*  */
 117 {
 118         return -ENOSYS;
 119 }
 120 
 121 int sys_gtty()
     /*  */
 122 {
 123         return -ENOSYS;
 124 }
 125 
 126 int sys_prof()
     /*  */
 127 {
 128         return -ENOSYS;
 129 }
 130 
 131 extern void hard_reset_now(void);
 132 
 133 /*
 134  * Reboot system call: for obvious reasons only root may call it,
 135  * and even root needs to set up some magic numbers in the registers
 136  * so that some mistake won't make this reboot the whole machine.
 137  * You can also set the meaning of the ctrl-alt-del-key here.
 138  *
 139  * reboot doesn't sync: do that yourself before calling this.
 140  */
 141 int sys_reboot(int magic, int magic_too, int flag)
     /*  */
 142 {
 143         if (!suser())
 144                 return -EPERM;
 145         if (magic != 0xfee1dead || magic_too != 672274793)
 146                 return -EINVAL;
 147         if (flag == 0x01234567)
 148                 hard_reset_now();
 149         else if (flag == 0x89ABCDEF)
 150                 C_A_D = 1;
 151         else if (!flag)
 152                 C_A_D = 0;
 153         else
 154                 return -EINVAL;
 155         return (0);
 156 }
 157 
 158 /*
 159  * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
 160  * As it's called within an interrupt, it may NOT sync: the only choice
 161  * is wether to reboot at once, or just ignore the ctrl-alt-del.
 162  */
 163 void ctrl_alt_del(void)
     /*  */
 164 {
 165         if (C_A_D)
 166                 hard_reset_now();
 167 }
 168         
 169 
 170 /*
 171  * This is done BSD-style, with no consideration of the saved gid, except
 172  * that if you set the effective gid, it sets the saved gid too.  This 
 173  * makes it possible for a setgid program to completely drop its privileges,
 174  * which is often a useful assertion to make when you are doing a security
 175  * audit over a program.
 176  *
 177  * The general idea is that a program which uses just setregid() will be
 178  * 100% compatible with BSD.  A program which uses just setgid() will be
 179  * 100% compatible with POSIX w/ Saved ID's. 
 180  */
 181 int sys_setregid(int rgid, int egid)
     /*  */
 182 {
 183         if (rgid>0) {
 184                 if ((current->gid == rgid) || 
 185                     suser())
 186                         current->gid = rgid;
 187                 else
 188                         return(-EPERM);
 189         }
 190         if (egid>0) {
 191                 if ((current->gid == egid) ||
 192                     (current->egid == egid) ||
 193                     suser()) {
 194                         current->egid = egid;
 195                         current->sgid = egid;
 196                 } else
 197                         return(-EPERM);
 198         }
 199         return 0;
 200 }
 201 
 202 /*
 203  * setgid() is implemeneted like SysV w/ SAVED_IDS 
 204  */
 205 int sys_setgid(int gid)
     /*  */
 206 {
 207         if (suser())
 208                 current->gid = current->egid = current->sgid = gid;
 209         else if ((gid == current->gid) || (gid == current->sgid))
 210                 current->egid = gid;
 211         else
 212                 return -EPERM;
 213         return 0;
 214 }
 215 
 216 int sys_acct()
     /*  */
 217 {
 218         return -ENOSYS;
 219 }
 220 
 221 int sys_phys()
     /*  */
 222 {
 223         return -ENOSYS;
 224 }
 225 
 226 int sys_lock()
     /*  */
 227 {
 228         return -ENOSYS;
 229 }
 230 
 231 int sys_mpx()
     /*  */
 232 {
 233         return -ENOSYS;
 234 }
 235 
 236 int sys_ulimit()
     /*  */
 237 {
 238         return -ENOSYS;
 239 }
 240 
 241 int sys_time(long * tloc)
     /*  */
 242 {
 243         int i;
 244 
 245         i = CURRENT_TIME;
 246         if (tloc) {
 247                 verify_area(tloc,4);
 248                 put_fs_long(i,(unsigned long *)tloc);
 249         }
 250         return i;
 251 }
 252 
 253 /*
 254  * Unprivileged users may change the real user id to the effective uid
 255  * or vice versa.  (BSD-style)
 256  *
 257  * When you set the effective uid, it sets the saved uid too.  This 
 258  * makes it possible for a setuid program to completely drop its privileges,
 259  * which is often a useful assertion to make when you are doing a security
 260  * audit over a program.
 261  *
 262  * The general idea is that a program which uses just setreuid() will be
 263  * 100% compatible with BSD.  A program which uses just setuid() will be
 264  * 100% compatible with POSIX w/ Saved ID's. 
 265  */
 266 int sys_setreuid(int ruid, int euid)
     /*  */
 267 {
 268         int old_ruid = current->uid;
 269         
 270         if (ruid>0) {
 271                 if ((current->euid==ruid) ||
 272                     (old_ruid == ruid) ||
 273                     suser())
 274                         current->uid = ruid;
 275                 else
 276                         return(-EPERM);
 277         }
 278         if (euid>0) {
 279                 if ((old_ruid == euid) ||
 280                     (current->euid == euid) ||
 281                     suser()) {
 282                         current->euid = euid;
 283                         current->suid = euid;
 284                 } else {
 285                         current->uid = old_ruid;
 286                         return(-EPERM);
 287                 }
 288         }
 289         return 0;
 290 }
 291 
 292 /*
 293  * setuid() is implemeneted like SysV w/ SAVED_IDS 
 294  * 
 295  * Note that SAVED_ID's is deficient in that a setuid root program
 296  * like sendmail, for example, cannot set its uid to be a normal 
 297  * user and then switch back, because if you're root, setuid() sets
 298  * the saved uid too.  If you don't like this, blame the bright people
 299  * in the POSIX commmittee and/or USG.  Note that the BSD-style setreuid()
 300  * will allow a root program to temporarily drop privileges and be able to
 301  * regain them by swapping the real and effective uid.  
 302  */
 303 int sys_setuid(int uid)
     /*  */
 304 {
 305         if (suser())
 306                 current->uid = current->euid = current->suid = uid;
 307         else if ((uid == current->uid) || (uid == current->suid))
 308                 current->euid = uid;
 309         else
 310                 return -EPERM;
 311         return(0);
 312 }
 313 
 314 int sys_stime(long * tptr)
     /*  */
 315 {
 316         if (!suser())
 317                 return -EPERM;
 318         startup_time = get_fs_long((unsigned long *)tptr) - jiffies/HZ;
 319         jiffies_offset = 0;
 320         return 0;
 321 }
 322 
 323 int sys_times(struct tms * tbuf)
     /*  */
 324 {
 325         if (tbuf) {
 326                 verify_area(tbuf,sizeof *tbuf);
 327                 put_fs_long(current->utime,(unsigned long *)&tbuf->tms_utime);
 328                 put_fs_long(current->stime,(unsigned long *)&tbuf->tms_stime);
 329                 put_fs_long(current->cutime,(unsigned long *)&tbuf->tms_cutime);
 330                 put_fs_long(current->cstime,(unsigned long *)&tbuf->tms_cstime);
 331         }
 332         return jiffies;
 333 }
 334 
 335 int sys_brk(unsigned long end_data_seg)
     /*  */
 336 {
 337         if (end_data_seg >= current->end_code &&
 338             end_data_seg < current->start_stack - 16384)
 339                 current->brk = end_data_seg;
 340         return current->brk;
 341 }
 342 
 343 /*
 344  * This needs some heave checking ...
 345  * I just haven't get the stomach for it. I also don't fully
 346  * understand sessions/pgrp etc. Let somebody who does explain it.
 347  *
 348  * OK, I think I have the protection semantics right.... this is really
 349  * only important on a multi-user system anyway, to make sure one user
 350  * can't send a signal to a process owned by another.  -TYT, 12/12/91
 351  */
 352 int sys_setpgid(int pid, int pgid)
     /*  */
 353 {
 354         int i; 
 355 
 356         if (!pid)
 357                 pid = current->pid;
 358         if (!pgid)
 359                 pgid = current->pid;
 360         if (pgid < 0)
 361                 return -EINVAL;
 362         for (i=0 ; i<NR_TASKS ; i++)
 363                 if (task[i] && (task[i]->pid == pid) &&
 364                     ((task[i]->p_pptr == current) || 
 365                      (task[i] == current))) {
 366                         if (task[i]->leader)
 367                                 return -EPERM;
 368                         if ((task[i]->session != current->session) ||
 369                             ((pgid != pid) && 
 370                              (session_of_pgrp(pgid) != current->session)))
 371                                 return -EPERM;
 372                         task[i]->pgrp = pgid;
 373                         return 0;
 374                 }
 375         return -ESRCH;
 376 }
 377 
 378 int sys_getpgrp(void)
     /*  */
 379 {
 380         return current->pgrp;
 381 }
 382 
 383 int sys_setsid(void)
     /*  */
 384 {
 385         if (current->leader && !suser())
 386                 return -EPERM;
 387         current->leader = 1;
 388         current->session = current->pgrp = current->pid;
 389         current->tty = -1;
 390         return current->pgrp;
 391 }
 392 
 393 /*
 394  * Supplementary group ID's
 395  */
 396 int sys_getgroups(int gidsetsize, gid_t *grouplist)
     /*  */
 397 {
 398         int     i;
 399 
 400         if (gidsetsize)
 401                 verify_area(grouplist, sizeof(gid_t) * gidsetsize);
 402 
 403         for (i = 0; (i < NGROUPS) && (current->groups[i] != NOGROUP);
 404              i++, grouplist++) {
 405                 if (gidsetsize) {
 406                         if (i >= gidsetsize)
 407                                 return -EINVAL;
 408                         put_fs_word(current->groups[i], (short *) grouplist);
 409                 }
 410         }
 411         return(i);
 412 }
 413 
 414 int sys_setgroups(int gidsetsize, gid_t *grouplist)
     /*  */
 415 {
 416         int     i;
 417 
 418         if (!suser())
 419                 return -EPERM;
 420         if (gidsetsize > NGROUPS)
 421                 return -EINVAL;
 422         for (i = 0; i < gidsetsize; i++, grouplist++) {
 423                 current->groups[i] = get_fs_word((unsigned short *) grouplist);
 424         }
 425         if (i < NGROUPS)
 426                 current->groups[i] = NOGROUP;
 427         return 0;
 428 }
 429 
 430 int in_group_p(gid_t grp)
     /*  */
 431 {
 432         int     i;
 433 
 434         if (grp == current->egid)
 435                 return 1;
 436 
 437         for (i = 0; i < NGROUPS; i++) {
 438                 if (current->groups[i] == NOGROUP)
 439                         break;
 440                 if (current->groups[i] == grp)
 441                         return 1;
 442         }
 443         return 0;
 444 }
 445 
 446 static struct utsname thisname = {
 447         UTS_SYSNAME, UTS_NODENAME, UTS_RELEASE, UTS_VERSION, UTS_MACHINE
 448 };
 449 
 450 int sys_uname(struct utsname * name)
     /*  */
 451 {
 452         int i;
 453 
 454         if (!name)
 455                 return -EINVAL;
 456         verify_area(name,sizeof *name);
 457         for(i=0;i<sizeof *name;i++)
 458                 put_fs_byte(((char *) &thisname)[i],i+(char *) name);
 459         return 0;
 460 }
 461 
 462 /*
 463  * Only sethostname; gethostname can be implemented by calling uname()
 464  */
 465 int sys_sethostname(char *name, int len)
     /*  */
 466 {
 467         int     i;
 468         
 469         if (!suser())
 470                 return -EPERM;
 471         if (len > MAXHOSTNAMELEN)
 472                 return -EINVAL;
 473         for (i=0; i < len; i++) {
 474                 if ((thisname.nodename[i] = get_fs_byte(name+i)) == 0)
 475                         break;
 476         }
 477         if (thisname.nodename[i]) {
 478                 thisname.nodename[i>MAXHOSTNAMELEN ? MAXHOSTNAMELEN : i] = 0;
 479         }
 480         return 0;
 481 }
 482 
 483 int sys_getrlimit(int resource, struct rlimit *rlim)
     /*  */
 484 {
 485         if (resource >= RLIM_NLIMITS)
 486                 return -EINVAL;
 487         verify_area(rlim,sizeof *rlim);
 488         put_fs_long(current->rlim[resource].rlim_cur, 
 489                     (unsigned long *) rlim);
 490         put_fs_long(current->rlim[resource].rlim_max, 
 491                     ((unsigned long *) rlim)+1);
 492         return 0;       
 493 }
 494 
 495 int sys_setrlimit(int resource, struct rlimit *rlim)
     /*  */
 496 {
 497         struct rlimit new, *old;
 498 
 499         if (resource >= RLIM_NLIMITS)
 500                 return -EINVAL;
 501         old = current->rlim + resource;
 502         new.rlim_cur = get_fs_long((unsigned long *) rlim);
 503         new.rlim_max = get_fs_long(((unsigned long *) rlim)+1);
 504         if (((new.rlim_cur > old->rlim_max) ||
 505              (new.rlim_max > old->rlim_max)) &&
 506             !suser())
 507                 return -EPERM;
 508         *old = new;
 509         return 0;
 510 }
 511 
 512 /*
 513  * It would make sense to put struct rusuage in the task_struct,
 514  * except that would make the task_struct be *really big*.  After
 515  * task_struct gets moved into malloc'ed memory, it would
 516  * make sense to do this.  It will make moving the rest of the information
 517  * a lot simpler!  (Which we're not doing right now because we're not
 518  * measuring them yet).
 519  */
 520 int sys_getrusage(int who, struct rusage *ru)
     /*  */
 521 {
 522         struct rusage r;
 523         unsigned long   *lp, *lpend, *dest;
 524 
 525         if (who != RUSAGE_SELF && who != RUSAGE_CHILDREN)
 526                 return -EINVAL;
 527         verify_area(ru, sizeof *ru);
 528         memset((char *) &r, 0, sizeof(r));
 529         if (who == RUSAGE_SELF) {
 530                 r.ru_utime.tv_sec = CT_TO_SECS(current->utime);
 531                 r.ru_utime.tv_usec = CT_TO_USECS(current->utime);
 532                 r.ru_stime.tv_sec = CT_TO_SECS(current->stime);
 533                 r.ru_stime.tv_usec = CT_TO_USECS(current->stime);
 534                 r.ru_minflt = current->min_flt;
 535                 r.ru_majflt = current->maj_flt;
 536         } else {
 537                 r.ru_utime.tv_sec = CT_TO_SECS(current->cutime);
 538                 r.ru_utime.tv_usec = CT_TO_USECS(current->cutime);
 539                 r.ru_stime.tv_sec = CT_TO_SECS(current->cstime);
 540                 r.ru_stime.tv_usec = CT_TO_USECS(current->cstime);
 541                 r.ru_minflt = current->cmin_flt;
 542                 r.ru_majflt = current->cmaj_flt;
 543         }
 544         lp = (unsigned long *) &r;
 545         lpend = (unsigned long *) (&r+1);
 546         dest = (unsigned long *) ru;
 547         for (; lp < lpend; lp++, dest++) 
 548                 put_fs_long(*lp, dest);
 549         return(0);
 550 }
 551 
 552 int sys_gettimeofday(struct timeval *tv, struct timezone *tz)
     /*  */
 553 {
 554         if (tv) {
 555                 verify_area(tv, sizeof *tv);
 556                 put_fs_long(startup_time + CT_TO_SECS(jiffies+jiffies_offset),
 557                             (unsigned long *) tv);
 558                 put_fs_long(CT_TO_USECS(jiffies+jiffies_offset), 
 559                             ((unsigned long *) tv)+1);
 560         }
 561         if (tz) {
 562                 verify_area(tz, sizeof *tz);
 563                 put_fs_long(sys_tz.tz_minuteswest, (unsigned long *) tz);
 564                 put_fs_long(sys_tz.tz_dsttime, ((unsigned long *) tz)+1);
 565         }
 566         return 0;
 567 }
 568 
 569 /*
 570  * The first time we set the timezone, we will warp the clock so that
 571  * it is ticking GMT time instead of local time.  Presumably, 
 572  * if someone is setting the timezone then we are running in an
 573  * environment where the programs understand about timezones.
 574  * This should be done at boot time in the /etc/rc script, as
 575  * soon as possible, so that the clock can be set right.  Otherwise,
 576  * various programs will get confused when the clock gets warped.
 577  */
 578 int sys_settimeofday(struct timeval *tv, struct timezone *tz)
     /*  */
 579 {
 580         static int      firsttime = 1;
 581         void            adjust_clock();
 582 
 583         if (!suser())
 584                 return -EPERM;
 585         if (tz) {
 586                 sys_tz.tz_minuteswest = get_fs_long((unsigned long *) tz);
 587                 sys_tz.tz_dsttime = get_fs_long(((unsigned long *) tz)+1);
 588                 if (firsttime) {
 589                         firsttime = 0;
 590                         if (!tv)
 591                                 adjust_clock();
 592                 }
 593         }
 594         if (tv) {
 595                 int sec, usec;
 596 
 597                 sec = get_fs_long((unsigned long *)tv);
 598                 usec = get_fs_long(((unsigned long *)tv)+1);
 599         
 600                 startup_time = sec - jiffies/HZ;
 601                 jiffies_offset = usec * HZ / 1000000 - jiffies%HZ;
 602         }
 603         return 0;
 604 }
 605 
 606 /*
 607  * Adjust the time obtained from the CMOS to be GMT time instead of
 608  * local time.
 609  * 
 610  * This is ugly, but preferable to the alternatives.  Otherwise we
 611  * would either need to write a program to do it in /etc/rc (and risk
 612  * confusion if the program gets run more than once; it would also be 
 613  * hard to make the program warp the clock precisely n hours)  or
 614  * compile in the timezone information into the kernel.  Bad, bad....
 615  *
 616  * XXX Currently does not adjust for daylight savings time.  May not
 617  * need to do anything, depending on how smart (dumb?) the BIOS
 618  * is.  Blast it all.... the best thing to do not depend on the CMOS
 619  * clock at all, but get the time via NTP or timed if you're on a 
 620  * network....                          - TYT, 1/1/92
 621  */
 622 void adjust_clock()
     /*  */
 623 {
 624         startup_time += sys_tz.tz_minuteswest*60;
 625 }
 626 
 627 int sys_umask(int mask)
     /*  */
 628 {
 629         int old = current->umask;
 630 
 631         current->umask = mask & 0777;
 632         return (old);
 633 }
 634 

/* */