Boot Linux faster!

Check our new training course

Boot Linux faster!

Check our new training course
and Creative Commons CC-BY-SA
lecture and lab materials

Bootlin logo

Elixir Cross Referencer

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
/*
 *  linux/kernel/sys.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/mm.h>
#include <linux/utsname.h>
#include <linux/mman.h>
#include <linux/smp_lock.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/prctl.h>

#include <asm/uaccess.h>
#include <asm/io.h>

/*
 * this indicates whether you can reboot with ctrl-alt-del: the default is yes
 */

int C_A_D = 1;


/*
 *	Notifier list for kernel code which wants to be called
 *	at shutdown. This is used to stop any idling DMA operations
 *	and the like. 
 */

struct notifier_block *reboot_notifier_list = NULL;

int register_reboot_notifier(struct notifier_block * nb)
{
	return notifier_chain_register(&reboot_notifier_list, nb);
}

int unregister_reboot_notifier(struct notifier_block * nb)
{
	return notifier_chain_unregister(&reboot_notifier_list, nb);
}



extern void adjust_clock(void);

asmlinkage int sys_ni_syscall(void)
{
	return -ENOSYS;
}

static int proc_sel(struct task_struct *p, int which, int who)
{
	if(p->pid)
	{
		switch (which) {
			case PRIO_PROCESS:
				if (!who && p == current)
					return 1;
				return(p->pid == who);
			case PRIO_PGRP:
				if (!who)
					who = current->pgrp;
				return(p->pgrp == who);
			case PRIO_USER:
				if (!who)
					who = current->uid;
				return(p->uid == who);
		}
	}
	return 0;
}

asmlinkage int sys_setpriority(int which, int who, int niceval)
{
	struct task_struct *p;
	unsigned int priority;
	int error;

	if (which > 2 || which < 0)
		return -EINVAL;

	/* normalize: avoid signed division (rounding problems) */
	error = ESRCH;
	priority = niceval;
	if (niceval < 0)
		priority = -niceval;
	if (priority > 20)
		priority = 20;
	priority = (priority * DEF_PRIORITY + 10) / 20 + DEF_PRIORITY;

	if (niceval >= 0) {
		priority = 2*DEF_PRIORITY - priority;
		if (!priority)
			priority = 1;
	}

	read_lock(&tasklist_lock);
	for_each_task(p) {
		if (!proc_sel(p, which, who))
			continue;
		if (p->uid != current->euid &&
			p->uid != current->uid && !capable(CAP_SYS_NICE)) {
			error = EPERM;
			continue;
		}
		if (error == ESRCH)
			error = 0;
		if (priority > p->priority && !capable(CAP_SYS_NICE))
			error = EACCES;
		else
			p->priority = priority;
	}
	read_unlock(&tasklist_lock);

	return -error;
}

/*
 * Ugh. To avoid negative return values, "getpriority()" will
 * not return the normal nice-value, but a value that has been
 * offset by 20 (ie it returns 0..40 instead of -20..20)
 */
asmlinkage int sys_getpriority(int which, int who)
{
	struct task_struct *p;
	long max_prio = -ESRCH;

	if (which > 2 || which < 0)
		return -EINVAL;

	read_lock(&tasklist_lock);
	for_each_task (p) {
		if (!proc_sel(p, which, who))
			continue;
		if (p->priority > max_prio)
			max_prio = p->priority;
	}
	read_unlock(&tasklist_lock);

	/* scale the priority from timeslice to 0..40 */
	if (max_prio > 0)
		max_prio = (max_prio * 20 + DEF_PRIORITY/2) / DEF_PRIORITY;
	return max_prio;
}


/*
 * Reboot system call: for obvious reasons only root may call it,
 * and even root needs to set up some magic numbers in the registers
 * so that some mistake won't make this reboot the whole machine.
 * You can also set the meaning of the ctrl-alt-del-key here.
 *
 * reboot doesn't sync: do that yourself before calling this.
 */
asmlinkage int sys_reboot(int magic1, int magic2, int cmd, void * arg)
{
	char buffer[256];

	/* We only trust the superuser with rebooting the system. */
	if (!capable(CAP_SYS_BOOT))
		return -EPERM;

	/* For safety, we require "magic" arguments. */
	if (magic1 != LINUX_REBOOT_MAGIC1 ||
	    (magic2 != LINUX_REBOOT_MAGIC2 && magic2 != LINUX_REBOOT_MAGIC2A &&
			magic2 != LINUX_REBOOT_MAGIC2B))
		return -EINVAL;

	lock_kernel();
	switch (cmd) {
	case LINUX_REBOOT_CMD_RESTART:
		notifier_call_chain(&reboot_notifier_list, SYS_RESTART, NULL);
		printk(KERN_EMERG "Restarting system.\n");
		machine_restart(NULL);
		break;

	case LINUX_REBOOT_CMD_CAD_ON:
		C_A_D = 1;
		break;

	case LINUX_REBOOT_CMD_CAD_OFF:
		C_A_D = 0;
		break;

	case LINUX_REBOOT_CMD_HALT:
		notifier_call_chain(&reboot_notifier_list, SYS_HALT, NULL);
		printk(KERN_EMERG "System halted.\n");
		machine_halt();
		do_exit(0);
		break;

	case LINUX_REBOOT_CMD_POWER_OFF:
		notifier_call_chain(&reboot_notifier_list, SYS_POWER_OFF, NULL);
		printk(KERN_EMERG "Power down.\n");
		machine_power_off();
		do_exit(0);
		break;

	case LINUX_REBOOT_CMD_RESTART2:
		if (strncpy_from_user(&buffer[0], (char *)arg, sizeof(buffer) - 1) < 0) {
			unlock_kernel();
			return -EFAULT;
		}
		buffer[sizeof(buffer) - 1] = '\0';

		notifier_call_chain(&reboot_notifier_list, SYS_RESTART, buffer);
		printk(KERN_EMERG "Restarting system with command '%s'.\n", buffer);
		machine_restart(buffer);
		break;

	default:
		unlock_kernel();
		return -EINVAL;
		break;
	};
	unlock_kernel();
	return 0;
}

/*
 * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
 * As it's called within an interrupt, it may NOT sync: the only choice
 * is whether to reboot at once, or just ignore the ctrl-alt-del.
 */
void ctrl_alt_del(void)
{
	if (C_A_D) {
		notifier_call_chain(&reboot_notifier_list, SYS_RESTART, NULL);
		machine_restart(NULL);
	} else
		kill_proc(1, SIGINT, 1);
}
	

/*
 * Unprivileged users may change the real gid to the effective gid
 * or vice versa.  (BSD-style)
 *
 * If you set the real gid at all, or set the effective gid to a value not
 * equal to the real gid, then the saved gid is set to the new effective gid.
 *
 * This makes it possible for a setgid program to completely drop its
 * privileges, which is often a useful assertion to make when you are doing
 * a security audit over a program.
 *
 * The general idea is that a program which uses just setregid() will be
 * 100% compatible with BSD.  A program which uses just setgid() will be
 * 100% compatible with POSIX with saved IDs. 
 *
 * SMP: There are not races, the GIDs are checked only by filesystem
 *      operations (as far as semantic preservation is concerned).
 */
asmlinkage int sys_setregid(gid_t rgid, gid_t egid)
{
	int old_rgid = current->gid;
	int old_egid = current->egid;

	if (rgid != (gid_t) -1) {
		if ((old_rgid == rgid) ||
		    (current->egid==rgid) ||
		    capable(CAP_SETGID))
			current->gid = rgid;
		else
			return -EPERM;
	}
	if (egid != (gid_t) -1) {
		if ((old_rgid == egid) ||
		    (current->egid == egid) ||
		    (current->sgid == egid) ||
		    capable(CAP_SETGID))
			current->fsgid = current->egid = egid;
		else {
			current->gid = old_rgid;
			return -EPERM;
		}
	}
	if (rgid != (gid_t) -1 ||
	    (egid != (gid_t) -1 && egid != old_rgid))
		current->sgid = current->egid;
	current->fsgid = current->egid;
	if (current->egid != old_egid)
		current->dumpable = 0;
	return 0;
}

/*
 * setgid() is implemented like SysV w/ SAVED_IDS 
 *
 * SMP: Same implicit races as above.
 */
asmlinkage int sys_setgid(gid_t gid)
{
	int old_egid = current->egid;

	if (capable(CAP_SETGID))
		current->gid = current->egid = current->sgid = current->fsgid = gid;
	else if ((gid == current->gid) || (gid == current->sgid))
		current->egid = current->fsgid = gid;
	else
		return -EPERM;

	if (current->egid != old_egid)
		current->dumpable = 0;
	return 0;
}
  
/* 
 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
 * a process after a call to setuid, setreuid, or setresuid.
 *
 *  1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
 *  {r,e,s}uid != 0, the permitted and effective capabilities are
 *  cleared.
 *
 *  2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
 *  capabilities of the process are cleared.
 *
 *  3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
 *  capabilities are set to the permitted capabilities.
 *
 *  fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 
 *  never happen.
 *
 *  -astor 
 */
extern inline void cap_emulate_setxuid(int old_ruid, int old_euid, 
				       int old_suid)
{
	if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
	    (current->uid != 0 && current->euid != 0 && current->suid != 0)) {
		cap_clear(current->cap_permitted);
		cap_clear(current->cap_effective);
	}
	if (old_euid == 0 && current->euid != 0) {
		cap_clear(current->cap_effective);
	}
	if (old_euid != 0 && current->euid == 0) {
		current->cap_effective = current->cap_permitted;
	}
}

/*
 * Unprivileged users may change the real uid to the effective uid
 * or vice versa.  (BSD-style)
 *
 * If you set the real uid at all, or set the effective uid to a value not
 * equal to the real uid, then the saved uid is set to the new effective uid.
 *
 * This makes it possible for a setuid program to completely drop its
 * privileges, which is often a useful assertion to make when you are doing
 * a security audit over a program.
 *
 * The general idea is that a program which uses just setreuid() will be
 * 100% compatible with BSD.  A program which uses just setuid() will be
 * 100% compatible with POSIX with saved IDs. 
 */
asmlinkage int sys_setreuid(uid_t ruid, uid_t euid)
{
	int old_ruid, old_euid, old_suid, new_ruid;

	new_ruid = old_ruid = current->uid;
	old_euid = current->euid;
	old_suid = current->suid;
	if (ruid != (uid_t) -1) {
		if ((old_ruid == ruid) || 
		    (current->euid==ruid) ||
		    capable(CAP_SETUID))
			new_ruid = ruid;
		else
			return -EPERM;
	}
	if (euid != (uid_t) -1) {
		if ((old_ruid == euid) ||
		    (current->euid == euid) ||
		    (current->suid == euid) ||
		    capable(CAP_SETUID))
			current->fsuid = current->euid = euid;
		else
			return -EPERM;
	}
	if (ruid != (uid_t) -1 ||
	    (euid != (uid_t) -1 && euid != old_ruid))
		current->suid = current->euid;
	current->fsuid = current->euid;
	if (current->euid != old_euid)
		current->dumpable = 0;

	if(new_ruid != old_ruid) {
		/* What if a process setreuid()'s and this brings the
		 * new uid over his NPROC rlimit?  We can check this now
		 * cheaply with the new uid cache, so if it matters
		 * we should be checking for it.  -DaveM
		 */
		free_uid(current);
		current->uid = new_ruid;
		alloc_uid(current);
	}
	
	if (!issecure(SECURE_NO_SETUID_FIXUP)) {
		cap_emulate_setxuid(old_ruid, old_euid, old_suid);
	}

	return 0;
}


		
/*
 * setuid() is implemented like SysV with SAVED_IDS 
 * 
 * Note that SAVED_ID's is deficient in that a setuid root program
 * like sendmail, for example, cannot set its uid to be a normal 
 * user and then switch back, because if you're root, setuid() sets
 * the saved uid too.  If you don't like this, blame the bright people
 * in the POSIX committee and/or USG.  Note that the BSD-style setreuid()
 * will allow a root program to temporarily drop privileges and be able to
 * regain them by swapping the real and effective uid.  
 */
asmlinkage int sys_setuid(uid_t uid)
{
	int old_euid = current->euid;
	int old_ruid, old_suid, new_ruid;

	old_ruid = new_ruid = current->uid;
	old_suid = current->suid;
	if (capable(CAP_SETUID))
		new_ruid = current->euid = current->suid = current->fsuid = uid;
	else if ((uid == current->uid) || (uid == current->suid))
		current->fsuid = current->euid = uid;
	else
		return -EPERM;

	if (current->euid != old_euid)
		current->dumpable = 0;

       if (new_ruid != old_ruid) {
		/* See comment above about NPROC rlimit issues... */
		free_uid(current);
		current->uid = new_ruid;
		alloc_uid(current);
	}

	if (!issecure(SECURE_NO_SETUID_FIXUP)) {
		cap_emulate_setxuid(old_ruid, old_euid, old_suid);
	}

	return 0;
}


/*
 * This function implements a generic ability to update ruid, euid,
 * and suid.  This allows you to implement the 4.4 compatible seteuid().
 */
asmlinkage int sys_setresuid(uid_t ruid, uid_t euid, uid_t suid)
{
	int old_ruid = current->uid;
	int old_euid = current->euid;
	int old_suid = current->suid;

	if (!capable(CAP_SETUID)) {
		if ((ruid != (uid_t) -1) && (ruid != current->uid) &&
		    (ruid != current->euid) && (ruid != current->suid))
			return -EPERM;
		if ((euid != (uid_t) -1) && (euid != current->uid) &&
		    (euid != current->euid) && (euid != current->suid))
			return -EPERM;
		if ((suid != (uid_t) -1) && (suid != current->uid) &&
		    (suid != current->euid) && (suid != current->suid))
			return -EPERM;
	}
	if (ruid != (uid_t) -1) {
		/* See above commentary about NPROC rlimit issues here. */
		free_uid(current);
		current->uid = ruid;
		alloc_uid(current);
	}
	if (euid != (uid_t) -1) {
		if (euid != current->euid)
			current->dumpable = 0;
		current->euid = euid;
		current->fsuid = euid;
	}
	if (suid != (uid_t) -1)
		current->suid = suid;

	if (!issecure(SECURE_NO_SETUID_FIXUP)) {
		cap_emulate_setxuid(old_ruid, old_euid, old_suid);
	}

	return 0;
}

asmlinkage int sys_getresuid(uid_t *ruid, uid_t *euid, uid_t *suid)
{
	int retval;

	if (!(retval = put_user(current->uid, ruid)) &&
	    !(retval = put_user(current->euid, euid)))
		retval = put_user(current->suid, suid);

	return retval;
}

/*
 * Same as above, but for rgid, egid, sgid.
 */
asmlinkage int sys_setresgid(gid_t rgid, gid_t egid, gid_t sgid)
{
       if (!capable(CAP_SETGID)) {
		if ((rgid != (gid_t) -1) && (rgid != current->gid) &&
		    (rgid != current->egid) && (rgid != current->sgid))
			return -EPERM;
		if ((egid != (gid_t) -1) && (egid != current->gid) &&
		    (egid != current->egid) && (egid != current->sgid))
			return -EPERM;
		if ((sgid != (gid_t) -1) && (sgid != current->gid) &&
		    (sgid != current->egid) && (sgid != current->sgid))
			return -EPERM;
	}
	if (rgid != (gid_t) -1)
		current->gid = rgid;
	if (egid != (gid_t) -1) {
		if (egid != current->egid)
			current->dumpable = 0;
		current->egid = egid;
		current->fsgid = egid;
	}
	if (sgid != (gid_t) -1)
		current->sgid = sgid;
	return 0;
}

asmlinkage int sys_getresgid(gid_t *rgid, gid_t *egid, gid_t *sgid)
{
	int retval;

	if (!(retval = put_user(current->gid, rgid)) &&
	    !(retval = put_user(current->egid, egid)))
		retval = put_user(current->sgid, sgid);

	return retval;
}


/*
 * "setfsuid()" sets the fsuid - the uid used for filesystem checks. This
 * is used for "access()" and for the NFS daemon (letting nfsd stay at
 * whatever uid it wants to). It normally shadows "euid", except when
 * explicitly set by setfsuid() or for access..
 */
asmlinkage int sys_setfsuid(uid_t uid)
{
	int old_fsuid;

	old_fsuid = current->fsuid;
	if (uid == current->uid || uid == current->euid ||
	    uid == current->suid || uid == current->fsuid || 
	    capable(CAP_SETUID))
		current->fsuid = uid;
	if (current->fsuid != old_fsuid)
		current->dumpable = 0;

	/* We emulate fsuid by essentially doing a scaled-down version
	 * of what we did in setresuid and friends. However, we only
	 * operate on the fs-specific bits of the process' effective
	 * capabilities 
	 *
	 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
	 *          if not, we might be a bit too harsh here.
	 */
	
	if (!issecure(SECURE_NO_SETUID_FIXUP)) {
		if (old_fsuid == 0 && current->fsuid != 0) {
			cap_t(current->cap_effective) &= ~CAP_FS_MASK;
		}
		if (old_fsuid != 0 && current->fsuid == 0) {
			cap_t(current->cap_effective) |=
				(cap_t(current->cap_permitted) & CAP_FS_MASK);
		}
	}

	return old_fsuid;
}

/*
 * Samma på svenska..
 */
asmlinkage int sys_setfsgid(gid_t gid)
{
	int old_fsgid;

	old_fsgid = current->fsgid;
	if (gid == current->gid || gid == current->egid ||
	    gid == current->sgid || gid == current->fsgid || 
	    capable(CAP_SETGID))
		current->fsgid = gid;
	if (current->fsgid != old_fsgid)
		current->dumpable = 0;

	return old_fsgid;
}

asmlinkage long sys_times(struct tms * tbuf)
{
	/*
	 *	In the SMP world we might just be unlucky and have one of
	 *	the times increment as we use it. Since the value is an
	 *	atomically safe type this is just fine. Conceptually its
	 *	as if the syscall took an instant longer to occur.
	 */
	if (tbuf)
		if (copy_to_user(tbuf, &current->times, sizeof(struct tms)))
			return -EFAULT;
	return jiffies;
}

/*
 * This needs some heavy checking ...
 * I just haven't the stomach for it. I also don't fully
 * understand sessions/pgrp etc. Let somebody who does explain it.
 *
 * OK, I think I have the protection semantics right.... this is really
 * only important on a multi-user system anyway, to make sure one user
 * can't send a signal to a process owned by another.  -TYT, 12/12/91
 *
 * Auch. Had to add the 'did_exec' flag to conform completely to POSIX.
 * LBT 04.03.94
 */

asmlinkage int sys_setpgid(pid_t pid, pid_t pgid)
{
	struct task_struct * p;
	int err = -EINVAL;

	if (!pid)
		pid = current->pid;
	if (!pgid)
		pgid = pid;
	if (pgid < 0)
		return -EINVAL;

	/* From this point forward we keep holding onto the tasklist lock
	 * so that our parent does not change from under us. -DaveM
	 */
	read_lock(&tasklist_lock);

	err = -ESRCH;
	p = find_task_by_pid(pid);
	if (!p)
		goto out;

	if (p->p_pptr == current || p->p_opptr == current) {
		err = -EPERM;
		if (p->session != current->session)
			goto out;
		err = -EACCES;
		if (p->did_exec)
			goto out;
	} else if (p != current)
		goto out;
	err = -EPERM;
	if (p->leader)
		goto out;
	if (pgid != pid) {
		struct task_struct * tmp;
		for_each_task (tmp) {
			if (tmp->pgrp == pgid &&
			    tmp->session == current->session)
				goto ok_pgid;
		}
		goto out;
	}

ok_pgid:
	p->pgrp = pgid;
	err = 0;
out:
	/* All paths lead to here, thus we are safe. -DaveM */
	read_unlock(&tasklist_lock);
	return err;
}

asmlinkage int sys_getpgid(pid_t pid)
{
	if (!pid) {
		return current->pgrp;
	} else {
		int retval;
		struct task_struct *p;

		read_lock(&tasklist_lock);
		p = find_task_by_pid(pid);

		retval = -ESRCH;
		if (p)
			retval = p->pgrp;
		read_unlock(&tasklist_lock);
		return retval;
	}
}

asmlinkage int sys_getpgrp(void)
{
	/* SMP - assuming writes are word atomic this is fine */
	return current->pgrp;
}

asmlinkage int sys_getsid(pid_t pid)
{
	if (!pid) {
		return current->session;
	} else {
		int retval;
		struct task_struct *p;

		read_lock(&tasklist_lock);
		p = find_task_by_pid(pid);

		retval = -ESRCH;
		if(p)
			retval = p->session;
		read_unlock(&tasklist_lock);
		return retval;
	}
}

asmlinkage int sys_setsid(void)
{
	struct task_struct * p;
	int err = -EPERM;

	read_lock(&tasklist_lock);
	for_each_task(p) {
		if (p->pgrp == current->pid)
			goto out;
	}

	current->leader = 1;
	current->session = current->pgrp = current->pid;
	current->tty = NULL;
	current->tty_old_pgrp = 0;
	err = current->pgrp;
out:
	read_unlock(&tasklist_lock);
	return err;
}

/*
 * Supplementary group IDs
 */
asmlinkage int sys_getgroups(int gidsetsize, gid_t *grouplist)
{
	int i;
	
	/*
	 *	SMP: Nobody else can change our grouplist. Thus we are
	 *	safe.
	 */

	if (gidsetsize < 0)
		return -EINVAL;
	i = current->ngroups;
	if (gidsetsize) {
		if (i > gidsetsize)
			return -EINVAL;
		if (copy_to_user(grouplist, current->groups, sizeof(gid_t)*i))
			return -EFAULT;
	}
	return i;
}

/*
 *	SMP: Our groups are not shared. We can copy to/from them safely
 *	without another task interfering.
 */
 
asmlinkage int sys_setgroups(int gidsetsize, gid_t *grouplist)
{
	if (!capable(CAP_SETGID))
		return -EPERM;
	if ((unsigned) gidsetsize > NGROUPS)
		return -EINVAL;
	if(copy_from_user(current->groups, grouplist, gidsetsize * sizeof(gid_t)))
		return -EFAULT;
	current->ngroups = gidsetsize;
	return 0;
}

int in_group_p(gid_t grp)
{
	if (grp != current->fsgid) {
		int i = current->ngroups;
		if (i) {
			gid_t *groups = current->groups;
			do {
				if (*groups == grp)
					goto out;
				groups++;
				i--;
			} while (i);
		}
		return 0;
	}
out:
	return 1;
}

/*
 * This should really be a blocking read-write lock
 * rather than a semaphore. Anybody want to implement
 * one?
 */
struct semaphore uts_sem = MUTEX;

asmlinkage int sys_newuname(struct new_utsname * name)
{
	int errno = 0;

	down(&uts_sem);
	if (copy_to_user(name,&system_utsname,sizeof *name))
		errno = -EFAULT;
	up(&uts_sem);
	return errno;
}

asmlinkage int sys_sethostname(char *name, int len)
{
	int errno;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
	if (len < 0 || len > __NEW_UTS_LEN)
		return -EINVAL;
	down(&uts_sem);
	errno = -EFAULT;
	if (!copy_from_user(system_utsname.nodename, name, len)) {
		system_utsname.nodename[len] = 0;
		errno = 0;
	}
	up(&uts_sem);
	return errno;
}

asmlinkage int sys_gethostname(char *name, int len)
{
	int i, errno;

	if (len < 0)
		return -EINVAL;
	down(&uts_sem);
	i = 1 + strlen(system_utsname.nodename);
	if (i > len)
		i = len;
	errno = 0;
	if (copy_to_user(name, system_utsname.nodename, i))
		errno = -EFAULT;
	up(&uts_sem);
	return errno;
}

/*
 * Only setdomainname; getdomainname can be implemented by calling
 * uname()
 */
asmlinkage int sys_setdomainname(char *name, int len)
{
	int errno;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
	if (len < 0 || len > __NEW_UTS_LEN)
		return -EINVAL;

	down(&uts_sem);
	errno = -EFAULT;
	if (!copy_from_user(system_utsname.domainname, name, len)) {
		errno = 0;
		system_utsname.domainname[len] = 0;
	}
	up(&uts_sem);
	return errno;
}

asmlinkage int sys_getrlimit(unsigned int resource, struct rlimit *rlim)
{
	if (resource >= RLIM_NLIMITS)
		return -EINVAL;
	else
		return copy_to_user(rlim, current->rlim + resource, sizeof(*rlim))
			? -EFAULT : 0;
}

asmlinkage int sys_setrlimit(unsigned int resource, struct rlimit *rlim)
{
	struct rlimit new_rlim, *old_rlim;

	if (resource >= RLIM_NLIMITS)
		return -EINVAL;
	if(copy_from_user(&new_rlim, rlim, sizeof(*rlim)))
		return -EFAULT;
	if (new_rlim.rlim_cur < 0 || new_rlim.rlim_max < 0)
		return -EINVAL;
	old_rlim = current->rlim + resource;
	if (((new_rlim.rlim_cur > old_rlim->rlim_max) ||
	     (new_rlim.rlim_max > old_rlim->rlim_max)) &&
	    !capable(CAP_SYS_RESOURCE))
		return -EPERM;
	if (resource == RLIMIT_NOFILE) {
		if (new_rlim.rlim_cur > NR_OPEN || new_rlim.rlim_max > NR_OPEN)
			return -EPERM;
	}
	*old_rlim = new_rlim;
	return 0;
}

/*
 * It would make sense to put struct rusage in the task_struct,
 * except that would make the task_struct be *really big*.  After
 * task_struct gets moved into malloc'ed memory, it would
 * make sense to do this.  It will make moving the rest of the information
 * a lot simpler!  (Which we're not doing right now because we're not
 * measuring them yet).
 *
 * This is SMP safe.  Either we are called from sys_getrusage on ourselves
 * below (we know we aren't going to exit/disappear and only we change our
 * rusage counters), or we are called from wait4() on a process which is
 * either stopped or zombied.  In the zombied case the task won't get
 * reaped till shortly after the call to getrusage(), in both cases the
 * task being examined is in a frozen state so the counters won't change.
 */
int getrusage(struct task_struct *p, int who, struct rusage *ru)
{
	struct rusage r;

	memset((char *) &r, 0, sizeof(r));
	switch (who) {
		case RUSAGE_SELF:
			r.ru_utime.tv_sec = CT_TO_SECS(p->times.tms_utime);
			r.ru_utime.tv_usec = CT_TO_USECS(p->times.tms_utime);
			r.ru_stime.tv_sec = CT_TO_SECS(p->times.tms_stime);
			r.ru_stime.tv_usec = CT_TO_USECS(p->times.tms_stime);
			r.ru_minflt = p->min_flt;
			r.ru_majflt = p->maj_flt;
			r.ru_nswap = p->nswap;
			break;
		case RUSAGE_CHILDREN:
			r.ru_utime.tv_sec = CT_TO_SECS(p->times.tms_cutime);
			r.ru_utime.tv_usec = CT_TO_USECS(p->times.tms_cutime);
			r.ru_stime.tv_sec = CT_TO_SECS(p->times.tms_cstime);
			r.ru_stime.tv_usec = CT_TO_USECS(p->times.tms_cstime);
			r.ru_minflt = p->cmin_flt;
			r.ru_majflt = p->cmaj_flt;
			r.ru_nswap = p->cnswap;
			break;
		default:
			r.ru_utime.tv_sec = CT_TO_SECS(p->times.tms_utime + p->times.tms_cutime);
			r.ru_utime.tv_usec = CT_TO_USECS(p->times.tms_utime + p->times.tms_cutime);
			r.ru_stime.tv_sec = CT_TO_SECS(p->times.tms_stime + p->times.tms_cstime);
			r.ru_stime.tv_usec = CT_TO_USECS(p->times.tms_stime + p->times.tms_cstime);
			r.ru_minflt = p->min_flt + p->cmin_flt;
			r.ru_majflt = p->maj_flt + p->cmaj_flt;
			r.ru_nswap = p->nswap + p->cnswap;
			break;
	}
	return copy_to_user(ru, &r, sizeof(r)) ? -EFAULT : 0;
}

asmlinkage int sys_getrusage(int who, struct rusage *ru)
{
	if (who != RUSAGE_SELF && who != RUSAGE_CHILDREN)
		return -EINVAL;
	return getrusage(current, who, ru);
}

asmlinkage int sys_umask(int mask)
{
	mask = xchg(&current->fs->umask, mask & S_IRWXUGO);
	return mask;
}
    
asmlinkage int sys_prctl(int option, unsigned long arg2, unsigned long arg3,
			 unsigned long arg4, unsigned long arg5)
{
	int error = 0;
	int sig;

	switch (option) {
		case PR_SET_PDEATHSIG:
			sig = arg2;
			if (sig > _NSIG) {
				error = -EINVAL;
				break;
			}
			current->pdeath_signal = sig;
			break;
		default:
			error = -EINVAL;
			break;
	}
	return error;
}