granicus.if.org Git - strace/blob - syscall.c

   1 /*
   2  * Copyright (c) 1991, 1992 Paul Kranenburg <pk@cs.few.eur.nl>
   3  * Copyright (c) 1993 Branko Lankester <branko@hacktic.nl>
   4  * Copyright (c) 1993, 1994, 1995, 1996 Rick Sladkey <jrs@world.std.com>
   5  * Copyright (c) 1996-1999 Wichert Akkerman <wichert@cistron.nl>
   6  * Copyright (c) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
   7  *                     Linux for s390 port by D.J. Barrow
   8  *                    <barrow_dj@mail.yahoo.com,djbarrow@de.ibm.com>
   9  * All rights reserved.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  * 3. The name of the author may not be used to endorse or promote products
  20  *    derived from this software without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  23  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  24  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  25  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  27  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  28  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  29  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  30  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  31  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  32  */
  33
  34 #include "defs.h"
  35 #include "native_defs.h"
  36 #include <sys/param.h>
  37 #include <signal.h>
  38
  39 /* for struct iovec */
  40 #include <sys/uio.h>
  41
  42 #include "regs.h"
  43 #include "ptrace.h"
  44
  45 #if defined(SPARC64)
  46 # undef PTRACE_GETREGS
  47 # define PTRACE_GETREGS PTRACE_GETREGS64
  48 # undef PTRACE_SETREGS
  49 # define PTRACE_SETREGS PTRACE_SETREGS64
  50 #endif
  51
  52 #if defined SPARC64
  53 # include <asm/psrcompat.h>
  54 #elif defined SPARC
  55 # include <asm/psr.h>
  56 #endif
  57
  58 #ifdef IA64
  59 # include <asm/rse.h>
  60 #endif
  61
  62 #ifndef NT_PRSTATUS
  63 # define NT_PRSTATUS 1
  64 #endif
  65
  66 #ifndef NSIG
  67 # warning: NSIG is not defined, using 32
  68 # define NSIG 32
  69 #endif
  70
  71 #include "syscall.h"
  72
  73 /* Define these shorthand notations to simplify the syscallent files. */
  74 #define TD TRACE_DESC
  75 #define TF TRACE_FILE
  76 #define TI TRACE_IPC
  77 #define TN TRACE_NETWORK
  78 #define TP TRACE_PROCESS
  79 #define TS TRACE_SIGNAL
  80 #define TM TRACE_MEMORY
  81 #define NF SYSCALL_NEVER_FAILS
  82 #define MA MAX_ARGS
  83 #define SI STACKTRACE_INVALIDATE_CACHE
  84 #define SE STACKTRACE_CAPTURE_ON_ENTER
  85
  86 #define SEN(syscall_name) SEN_ ## syscall_name, SYS_FUNC_NAME(sys_ ## syscall_name)
  87
  88 const struct_sysent sysent0[] = {
  89 #include "syscallent.h"
  90 };
  91
  92 #if SUPPORTED_PERSONALITIES > 1
  93 # include PERSONALITY1_INCLUDE_FUNCS
  94 static const struct_sysent sysent1[] = {
  95 # include "syscallent1.h"
  96 };
  97 #endif
  98
  99 #if SUPPORTED_PERSONALITIES > 2
 100 # include PERSONALITY2_INCLUDE_FUNCS
 101 static const struct_sysent sysent2[] = {
 102 # include "syscallent2.h"
 103 };
 104 #endif
 105
 106 /* Now undef them since short defines cause wicked namespace pollution. */
 107 #undef SEN
 108 #undef TD
 109 #undef TF
 110 #undef TI
 111 #undef TN
 112 #undef TP
 113 #undef TS
 114 #undef TM
 115 #undef NF
 116 #undef MA
 117 #undef SI
 118 #undef SE
 119
 120 /*
 121  * `ioctlent[012].h' files are automatically generated by the auxiliary
 122  * program `ioctlsort', such that the list is sorted by the `code' field.
 123  * This has the side-effect of resolving the _IO.. macros into
 124  * plain integers, eliminating the need to include here everything
 125  * in "/usr/include".
 126  */
 127
 128 const char *const errnoent0[] = {
 129 #include "errnoent.h"
 130 };
 131 const char *const signalent0[] = {
 132 #include "signalent.h"
 133 };
 134 const struct_ioctlent ioctlent0[] = {
 135 #include "ioctlent0.h"
 136 };
 137
 138 #if SUPPORTED_PERSONALITIES > 1
 139 static const char *const errnoent1[] = {
 140 # include "errnoent1.h"
 141 };
 142 static const char *const signalent1[] = {
 143 # include "signalent1.h"
 144 };
 145 static const struct_ioctlent ioctlent1[] = {
 146 # include "ioctlent1.h"
 147 };
 148 # include PERSONALITY0_INCLUDE_PRINTERS_DECLS
 149 static const struct_printers printers0 = {
 150 # include PERSONALITY0_INCLUDE_PRINTERS_DEFS
 151 };
 152 # include PERSONALITY1_INCLUDE_PRINTERS_DECLS
 153 static const struct_printers printers1 = {
 154 # include PERSONALITY1_INCLUDE_PRINTERS_DEFS
 155 };
 156 #endif
 157
 158 #if SUPPORTED_PERSONALITIES > 2
 159 static const char *const errnoent2[] = {
 160 # include "errnoent2.h"
 161 };
 162 static const char *const signalent2[] = {
 163 # include "signalent2.h"
 164 };
 165 static const struct_ioctlent ioctlent2[] = {
 166 # include "ioctlent2.h"
 167 };
 168 # include PERSONALITY2_INCLUDE_PRINTERS_DECLS
 169 static const struct_printers printers2 = {
 170 # include PERSONALITY2_INCLUDE_PRINTERS_DEFS
 171 };
 172 #endif
 173
 174 enum {
 175         nsyscalls0 = ARRAY_SIZE(sysent0)
 176 #if SUPPORTED_PERSONALITIES > 1
 177         , nsyscalls1 = ARRAY_SIZE(sysent1)
 178 # if SUPPORTED_PERSONALITIES > 2
 179         , nsyscalls2 = ARRAY_SIZE(sysent2)
 180 # endif
 181 #endif
 182 };
 183
 184 enum {
 185         nerrnos0 = ARRAY_SIZE(errnoent0)
 186 #if SUPPORTED_PERSONALITIES > 1
 187         , nerrnos1 = ARRAY_SIZE(errnoent1)
 188 # if SUPPORTED_PERSONALITIES > 2
 189         , nerrnos2 = ARRAY_SIZE(errnoent2)
 190 # endif
 191 #endif
 192 };
 193
 194 enum {
 195         nsignals0 = ARRAY_SIZE(signalent0)
 196 #if SUPPORTED_PERSONALITIES > 1
 197         , nsignals1 = ARRAY_SIZE(signalent1)
 198 # if SUPPORTED_PERSONALITIES > 2
 199         , nsignals2 = ARRAY_SIZE(signalent2)
 200 # endif
 201 #endif
 202 };
 203
 204 enum {
 205         nioctlents0 = ARRAY_SIZE(ioctlent0)
 206 #if SUPPORTED_PERSONALITIES > 1
 207         , nioctlents1 = ARRAY_SIZE(ioctlent1)
 208 # if SUPPORTED_PERSONALITIES > 2
 209         , nioctlents2 = ARRAY_SIZE(ioctlent2)
 210 # endif
 211 #endif
 212 };
 213
 214 #if SUPPORTED_PERSONALITIES > 1
 215 const struct_sysent *sysent = sysent0;
 216 const char *const *errnoent = errnoent0;
 217 const char *const *signalent = signalent0;
 218 const struct_ioctlent *ioctlent = ioctlent0;
 219 const struct_printers *printers = &printers0;
 220 #endif
 221
 222 unsigned nsyscalls = nsyscalls0;
 223 unsigned nerrnos = nerrnos0;
 224 unsigned nsignals = nsignals0;
 225 unsigned nioctlents = nioctlents0;
 226
 227 const unsigned int nsyscall_vec[SUPPORTED_PERSONALITIES] = {
 228         nsyscalls0,
 229 #if SUPPORTED_PERSONALITIES > 1
 230         nsyscalls1,
 231 #endif
 232 #if SUPPORTED_PERSONALITIES > 2
 233         nsyscalls2,
 234 #endif
 235 };
 236 const struct_sysent *const sysent_vec[SUPPORTED_PERSONALITIES] = {
 237         sysent0,
 238 #if SUPPORTED_PERSONALITIES > 1
 239         sysent1,
 240 #endif
 241 #if SUPPORTED_PERSONALITIES > 2
 242         sysent2,
 243 #endif
 244 };
 245
 246 #if SUPPORTED_PERSONALITIES > 1
 247 unsigned current_personality;
 248
 249 # ifndef current_wordsize
 250 unsigned current_wordsize;
 251 static const int personality_wordsize[SUPPORTED_PERSONALITIES] = {
 252         PERSONALITY0_WORDSIZE,
 253         PERSONALITY1_WORDSIZE,
 254 # if SUPPORTED_PERSONALITIES > 2
 255         PERSONALITY2_WORDSIZE,
 256 # endif
 257 };
 258 # endif
 259
 260 # ifndef current_klongsize
 261 unsigned current_klongsize;
 262 static const int personality_klongsize[SUPPORTED_PERSONALITIES] = {
 263         PERSONALITY0_KLONGSIZE,
 264         PERSONALITY1_KLONGSIZE,
 265 #  if SUPPORTED_PERSONALITIES > 2
 266         PERSONALITY2_KLONGSIZE,
 267 #  endif
 268 };
 269 # endif
 270
 271 void
 272 set_personality(int personality)
 273 {
 274         nsyscalls = nsyscall_vec[personality];
 275         sysent = sysent_vec[personality];
 276
 277         switch (personality) {
 278         case 0:
 279                 errnoent = errnoent0;
 280                 nerrnos = nerrnos0;
 281                 ioctlent = ioctlent0;
 282                 nioctlents = nioctlents0;
 283                 signalent = signalent0;
 284                 nsignals = nsignals0;
 285                 printers = &printers0;
 286                 break;
 287
 288         case 1:
 289                 errnoent = errnoent1;
 290                 nerrnos = nerrnos1;
 291                 ioctlent = ioctlent1;
 292                 nioctlents = nioctlents1;
 293                 signalent = signalent1;
 294                 nsignals = nsignals1;
 295                 printers = &printers1;
 296                 break;
 297
 298 # if SUPPORTED_PERSONALITIES > 2
 299         case 2:
 300                 errnoent = errnoent2;
 301                 nerrnos = nerrnos2;
 302                 ioctlent = ioctlent2;
 303                 nioctlents = nioctlents2;
 304                 signalent = signalent2;
 305                 nsignals = nsignals2;
 306                 printers = &printers2;
 307                 break;
 308 # endif
 309         }
 310
 311         current_personality = personality;
 312 # ifndef current_wordsize
 313         current_wordsize = personality_wordsize[personality];
 314 # endif
 315 # ifndef current_klongsize
 316         current_klongsize = personality_klongsize[personality];
 317 # endif
 318 }
 319
 320 static void
 321 update_personality(struct tcb *tcp, unsigned int personality)
 322 {
 323         if (personality == current_personality)
 324                 return;
 325         set_personality(personality);
 326
 327         if (personality == tcp->currpers)
 328                 return;
 329         tcp->currpers = personality;
 330
 331 # undef PERSONALITY_NAMES
 332 # if defined POWERPC64
 333 #  define PERSONALITY_NAMES {"64 bit", "32 bit"}
 334 # elif defined X86_64
 335 #  define PERSONALITY_NAMES {"64 bit", "32 bit", "x32"}
 336 # elif defined X32
 337 #  define PERSONALITY_NAMES {"x32", "32 bit"}
 338 # elif defined AARCH64
 339 #  define PERSONALITY_NAMES {"64 bit", "32 bit"}
 340 # elif defined TILE
 341 #  define PERSONALITY_NAMES {"64-bit", "32-bit"}
 342 # endif
 343 # ifdef PERSONALITY_NAMES
 344         if (!qflag) {
 345                 static const char *const names[] = PERSONALITY_NAMES;
 346                 error_msg("[ Process PID=%d runs in %s mode. ]",
 347                           tcp->pid, names[personality]);
 348         }
 349 # endif
 350 }
 351 #endif
 352
 353 #ifdef SYS_socket_subcall
 354 static void
 355 decode_socket_subcall(struct tcb *tcp)
 356 {
 357         const int call = tcp->u_arg[0];
 358
 359         if (call < 1 || call >= SYS_socket_nsubcalls)
 360                 return;
 361
 362         const kernel_scno_t scno = SYS_socket_subcall + call;
 363         const unsigned int nargs = sysent[scno].nargs;
 364         uint64_t buf[nargs];
 365
 366         if (umoven(tcp, tcp->u_arg[1], nargs * current_wordsize, buf) < 0)
 367                 return;
 368
 369         tcp->scno = scno;
 370         tcp->qual_flg = qual_flags(scno);
 371         tcp->s_ent = &sysent[scno];
 372
 373         unsigned int i;
 374         for (i = 0; i < nargs; ++i)
 375                 tcp->u_arg[i] = (sizeof(uint32_t) == current_wordsize)
 376                                 ? ((uint32_t *) (void *) buf)[i] : buf[i];
 377 }
 378 #endif
 379
 380 #ifdef SYS_ipc_subcall
 381 static void
 382 decode_ipc_subcall(struct tcb *tcp)
 383 {
 384         unsigned int call = tcp->u_arg[0];
 385         const unsigned int version = call >> 16;
 386
 387         if (version) {
 388 # if defined S390 || defined S390X
 389                 return;
 390 # else
 391 #  ifdef SPARC64
 392                 if (current_wordsize == 8)
 393                         return;
 394 #  endif
 395                 set_tcb_priv_ulong(tcp, version);
 396                 call &= 0xffff;
 397 # endif
 398         }
 399
 400         switch (call) {
 401                 case  1: case  2: case  3: case  4:
 402                 case 11: case 12: case 13: case 14:
 403                 case 21: case 22: case 23: case 24:
 404                         break;
 405                 default:
 406                         return;
 407         }
 408
 409         tcp->scno = SYS_ipc_subcall + call;
 410         tcp->qual_flg = qual_flags(tcp->scno);
 411         tcp->s_ent = &sysent[tcp->scno];
 412
 413         const unsigned int n = tcp->s_ent->nargs;
 414         unsigned int i;
 415         for (i = 0; i < n; i++)
 416                 tcp->u_arg[i] = tcp->u_arg[i + 1];
 417 }
 418 #endif
 419
 420 #ifdef LINUX_MIPSO32
 421 static void
 422 decode_mips_subcall(struct tcb *tcp)
 423 {
 424         if (!scno_is_valid(tcp->u_arg[0]))
 425                 return;
 426         tcp->scno = tcp->u_arg[0];
 427         tcp->qual_flg = qual_flags(tcp->scno);
 428         tcp->s_ent = &sysent[tcp->scno];
 429         memmove(&tcp->u_arg[0], &tcp->u_arg[1],
 430                 sizeof(tcp->u_arg) - sizeof(tcp->u_arg[0]));
 431         /*
 432          * Fetching the last arg of 7-arg syscalls (fadvise64_64
 433          * and sync_file_range) requires additional code,
 434          * see linux/mips/get_syscall_args.c
 435          */
 436         if (tcp->s_ent->nargs == MAX_ARGS) {
 437                 if (umoven(tcp,
 438                            mips_REG_SP + MAX_ARGS * sizeof(tcp->u_arg[0]),
 439                            sizeof(tcp->u_arg[0]),
 440                            &tcp->u_arg[MAX_ARGS - 1]) < 0)
 441                 tcp->u_arg[MAX_ARGS - 1] = 0;
 442         }
 443 }
 444 #endif /* LINUX_MIPSO32 */
 445
 446 static void
 447 dumpio(struct tcb *tcp)
 448 {
 449         if (syserror(tcp))
 450                 return;
 451
 452         int fd = tcp->u_arg[0];
 453         if (fd < 0)
 454                 return;
 455
 456         if (is_number_in_set(fd, &read_set)) {
 457                 switch (tcp->s_ent->sen) {
 458                 case SEN_read:
 459                 case SEN_pread:
 460                 case SEN_recv:
 461                 case SEN_recvfrom:
 462                 case SEN_mq_timedreceive:
 463                         dumpstr(tcp, tcp->u_arg[1], tcp->u_rval);
 464                         return;
 465                 case SEN_readv:
 466                 case SEN_preadv:
 467                 case SEN_preadv2:
 468                         dumpiov_upto(tcp, tcp->u_arg[2], tcp->u_arg[1],
 469                                      tcp->u_rval);
 470                         return;
 471                 case SEN_recvmsg:
 472                         dumpiov_in_msghdr(tcp, tcp->u_arg[1], tcp->u_rval);
 473                         return;
 474                 case SEN_recvmmsg:
 475                         dumpiov_in_mmsghdr(tcp, tcp->u_arg[1]);
 476                         return;
 477                 }
 478         }
 479         if (is_number_in_set(fd, &write_set)) {
 480                 switch (tcp->s_ent->sen) {
 481                 case SEN_write:
 482                 case SEN_pwrite:
 483                 case SEN_send:
 484                 case SEN_sendto:
 485                 case SEN_mq_timedsend:
 486                         dumpstr(tcp, tcp->u_arg[1], tcp->u_arg[2]);
 487                         break;
 488                 case SEN_writev:
 489                 case SEN_pwritev:
 490                 case SEN_pwritev2:
 491                 case SEN_vmsplice:
 492                         dumpiov(tcp, tcp->u_arg[2], tcp->u_arg[1]);
 493                         break;
 494                 case SEN_sendmsg:
 495                         dumpiov_in_msghdr(tcp, tcp->u_arg[1], -1UL);
 496                         break;
 497                 case SEN_sendmmsg:
 498                         dumpiov_in_mmsghdr(tcp, tcp->u_arg[1]);
 499                         break;
 500                 }
 501         }
 502 }
 503
 504 /*
 505  * Shuffle syscall numbers so that we don't have huge gaps in syscall table.
 506  * The shuffling should be an involution: shuffle_scno(shuffle_scno(n)) == n.
 507  */
 508 static kernel_scno_t
 509 shuffle_scno(kernel_scno_t scno)
 510 {
 511 #if defined(ARM) || defined(AARCH64) /* So far only 32-bit ARM needs this */
 512         if (scno < ARM_FIRST_SHUFFLED_SYSCALL)
 513                 return scno;
 514
 515         /* __ARM_NR_cmpxchg? Swap with LAST_ORDINARY+1 */
 516         if (scno == ARM_FIRST_SHUFFLED_SYSCALL)
 517                 return 0x000ffff0;
 518         if (scno == 0x000ffff0)
 519                 return ARM_FIRST_SHUFFLED_SYSCALL;
 520
 521 # define ARM_SECOND_SHUFFLED_SYSCALL (ARM_FIRST_SHUFFLED_SYSCALL + 1)
 522         /*
 523          * Is it ARM specific syscall?
 524          * Swap [0x000f0000, 0x000f0000 + LAST_SPECIAL] range
 525          * with [SECOND_SHUFFLED, SECOND_SHUFFLED + LAST_SPECIAL] range.
 526          */
 527         if (scno >= 0x000f0000 &&
 528             scno <= 0x000f0000 + ARM_LAST_SPECIAL_SYSCALL) {
 529                 return scno - 0x000f0000 + ARM_SECOND_SHUFFLED_SYSCALL;
 530         }
 531         if (scno <= ARM_SECOND_SHUFFLED_SYSCALL + ARM_LAST_SPECIAL_SYSCALL) {
 532                 return scno + 0x000f0000 - ARM_SECOND_SHUFFLED_SYSCALL;
 533         }
 534 #endif /* ARM || AARCH64 */
 535
 536         return scno;
 537 }
 538
 539 const char *
 540 err_name(unsigned long err)
 541 {
 542         if ((err < nerrnos) && errnoent[err])
 543                 return errnoent[err];
 544
 545         return NULL;
 546 }
 547
 548 static long get_regs_error;
 549
 550 void
 551 clear_regs(void)
 552 {
 553         get_regs_error = -1;
 554 }
 555
 556 static int get_syscall_args(struct tcb *);
 557 static int get_syscall_result(struct tcb *);
 558 static int arch_get_scno(struct tcb *tcp);
 559 static int arch_set_scno(struct tcb *, kernel_scno_t);
 560 static void get_error(struct tcb *, const bool);
 561 static int arch_set_error(struct tcb *);
 562
 563 struct fault_opts *fault_vec[SUPPORTED_PERSONALITIES];
 564
 565 static struct fault_opts *
 566 tcb_fault_opts(struct tcb *tcp)
 567 {
 568         return (scno_in_range(tcp->scno) && tcp->fault_vec[current_personality])
 569                ? &tcp->fault_vec[current_personality][tcp->scno] : NULL;
 570 }
 571
 572
 573 static long
 574 inject_syscall_fault_entering(struct tcb *tcp)
 575 {
 576         if (!tcp->fault_vec[current_personality]) {
 577                 tcp->fault_vec[current_personality] =
 578                         xcalloc(nsyscalls, sizeof(**fault_vec));
 579                 memcpy(tcp->fault_vec[current_personality],
 580                        fault_vec[current_personality],
 581                        nsyscalls * sizeof(**fault_vec));
 582         }
 583
 584         struct fault_opts *opts = tcb_fault_opts(tcp);
 585
 586         if (!opts || opts->first == 0)
 587                 return 0;
 588
 589         --opts->first;
 590
 591         if (opts->first != 0)
 592                 return 0;
 593
 594         opts->first = opts->step;
 595
 596         if (!arch_set_scno(tcp, -1))
 597                 tcp->flags |= TCB_FAULT_INJ;
 598
 599         return 0;
 600 }
 601
 602 static long
 603 update_syscall_fault_exiting(struct tcb *tcp)
 604 {
 605         struct fault_opts *opts = tcb_fault_opts(tcp);
 606
 607         if (opts && opts->err && tcp->u_error != opts->err) {
 608                 unsigned long u_error = tcp->u_error;
 609                 tcp->u_error = opts->err;
 610                 if (arch_set_error(tcp))
 611                         tcp->u_error = u_error;
 612         }
 613
 614         return 0;
 615 }
 616
 617 static int
 618 trace_syscall_entering(struct tcb *tcp)
 619 {
 620         int res, scno_good;
 621
 622         scno_good = res = get_scno(tcp);
 623         if (res == 0)
 624                 return res;
 625         if (res == 1)
 626                 res = get_syscall_args(tcp);
 627
 628         if (res != 1) {
 629                 printleader(tcp);
 630                 tprintf("%s(", scno_good == 1 ? tcp->s_ent->sys_name : "????");
 631                 /*
 632                  * " <unavailable>" will be added later by the code which
 633                  * detects ptrace errors.
 634                  */
 635                 goto ret;
 636         }
 637
 638 #ifdef LINUX_MIPSO32
 639         if (SEN_syscall == tcp->s_ent->sen)
 640                 decode_mips_subcall(tcp);
 641 #endif
 642
 643 #if defined(SYS_socket_subcall) || defined(SYS_ipc_subcall)
 644         switch (tcp->s_ent->sen) {
 645 # ifdef SYS_socket_subcall
 646                 case SEN_socketcall:
 647                         decode_socket_subcall(tcp);
 648                         break;
 649 # endif
 650 # ifdef SYS_ipc_subcall
 651                 case SEN_ipc:
 652                         decode_ipc_subcall(tcp);
 653                         break;
 654 # endif
 655         }
 656 #endif
 657
 658         /* Restrain from fault injection while the trace executes strace code. */
 659         if (hide_log(tcp)) {
 660                 tcp->qual_flg &= ~QUAL_FAULT;
 661         }
 662
 663         switch (tcp->s_ent->sen) {
 664                 case SEN_execve:
 665                 case SEN_execveat:
 666 #if defined SPARC || defined SPARC64
 667                 case SEN_execv:
 668 #endif
 669                         tcp->flags &= ~TCB_HIDE_LOG;
 670                         break;
 671         }
 672
 673         if (!(tcp->qual_flg & QUAL_TRACE)
 674          || (tracing_paths && !pathtrace_match(tcp))
 675         ) {
 676                 tcp->flags |= TCB_INSYSCALL | TCB_FILTERED;
 677                 tcp->sys_func_rval = 0;
 678                 return 0;
 679         }
 680
 681         tcp->flags &= ~TCB_FILTERED;
 682
 683         if (hide_log(tcp)) {
 684                 res = 0;
 685                 goto ret;
 686         }
 687
 688         if (tcp->qual_flg & QUAL_FAULT)
 689                 inject_syscall_fault_entering(tcp);
 690
 691         if (cflag == CFLAG_ONLY_STATS) {
 692                 res = 0;
 693                 goto ret;
 694         }
 695
 696 #ifdef USE_LIBUNWIND
 697         if (stack_trace_enabled) {
 698                 if (tcp->s_ent->sys_flags & STACKTRACE_CAPTURE_ON_ENTER)
 699                         unwind_capture_stacktrace(tcp);
 700         }
 701 #endif
 702
 703         printleader(tcp);
 704         tprintf("%s(", tcp->s_ent->sys_name);
 705         if (tcp->qual_flg & QUAL_RAW)
 706                 res = printargs(tcp);
 707         else
 708                 res = tcp->s_ent->sys_func(tcp);
 709
 710         fflush(tcp->outf);
 711  ret:
 712         tcp->flags |= TCB_INSYSCALL;
 713         tcp->sys_func_rval = res;
 714         /* Measure the entrance time as late as possible to avoid errors. */
 715         if (Tflag || cflag)
 716                 gettimeofday(&tcp->etime, NULL);
 717         return res;
 718 }
 719
 720 static bool
 721 syscall_fault_injected(struct tcb *tcp)
 722 {
 723         return tcp->flags & TCB_FAULT_INJ;
 724 }
 725
 726 static int
 727 trace_syscall_exiting(struct tcb *tcp)
 728 {
 729         int sys_res;
 730         struct timeval tv;
 731         int res;
 732         unsigned long u_error;
 733         const char *u_error_str;
 734
 735         /* Measure the exit time as early as possible to avoid errors. */
 736         if (Tflag || cflag)
 737                 gettimeofday(&tv, NULL);
 738
 739 #ifdef USE_LIBUNWIND
 740         if (stack_trace_enabled) {
 741                 if (tcp->s_ent->sys_flags & STACKTRACE_INVALIDATE_CACHE)
 742                         unwind_cache_invalidate(tcp);
 743         }
 744 #endif
 745
 746 #if SUPPORTED_PERSONALITIES > 1
 747         update_personality(tcp, tcp->currpers);
 748 #endif
 749         res = (get_regs_error ? -1 : get_syscall_result(tcp));
 750         if (filtered(tcp) || hide_log(tcp))
 751                 goto ret;
 752
 753         if (syserror(tcp) && syscall_fault_injected(tcp))
 754                 update_syscall_fault_exiting(tcp);
 755
 756         if (cflag) {
 757                 count_syscall(tcp, &tv);
 758                 if (cflag == CFLAG_ONLY_STATS) {
 759                         goto ret;
 760                 }
 761         }
 762
 763         /* If not in -ff mode, and printing_tcp != tcp,
 764          * then the log currently does not end with output
 765          * of _our syscall entry_, but with something else.
 766          * We need to say which syscall's return is this.
 767          *
 768          * Forced reprinting via TCB_REPRINT is used only by
 769          * "strace -ff -oLOG test/threaded_execve" corner case.
 770          * It's the only case when -ff mode needs reprinting.
 771          */
 772         if ((followfork < 2 && printing_tcp != tcp) || (tcp->flags & TCB_REPRINT)) {
 773                 tcp->flags &= ~TCB_REPRINT;
 774                 printleader(tcp);
 775                 tprintf("<... %s resumed> ", tcp->s_ent->sys_name);
 776         }
 777         printing_tcp = tcp;
 778
 779         tcp->s_prev_ent = NULL;
 780         if (res != 1) {
 781                 /* There was error in one of prior ptrace ops */
 782                 tprints(") ");
 783                 tabto();
 784                 tprints("= ? <unavailable>\n");
 785                 line_ended();
 786                 tcp->flags &= ~(TCB_INSYSCALL | TCB_FAULT_INJ);
 787                 tcp->sys_func_rval = 0;
 788                 free_tcb_priv_data(tcp);
 789                 return res;
 790         }
 791         tcp->s_prev_ent = tcp->s_ent;
 792
 793         sys_res = 0;
 794         if (tcp->qual_flg & QUAL_RAW) {
 795                 /* sys_res = printargs(tcp); - but it's nop on sysexit */
 796         } else {
 797         /* FIXME: not_failing_only (IOW, option -z) is broken:
 798          * failure of syscall is known only after syscall return.
 799          * Thus we end up with something like this on, say, ENOENT:
 800          *     open("doesnt_exist", O_RDONLY <unfinished ...>
 801          *     {next syscall decode}
 802          * whereas the intended result is that open(...) line
 803          * is not shown at all.
 804          */
 805                 if (not_failing_only && tcp->u_error)
 806                         goto ret;       /* ignore failed syscalls */
 807                 if (tcp->sys_func_rval & RVAL_DECODED)
 808                         sys_res = tcp->sys_func_rval;
 809                 else
 810                         sys_res = tcp->s_ent->sys_func(tcp);
 811         }
 812
 813         tprints(") ");
 814         tabto();
 815         u_error = tcp->u_error;
 816
 817         if (tcp->qual_flg & QUAL_RAW) {
 818                 if (u_error) {
 819                         tprintf("= -1 (errno %lu)", u_error);
 820                         if (syscall_fault_injected(tcp))
 821                                 tprints(" (INJECTED)");
 822                 } else {
 823                         tprintf("= %#lx", tcp->u_rval);
 824                 }
 825         }
 826         else if (!(sys_res & RVAL_NONE) && u_error) {
 827                 switch (u_error) {
 828                 /* Blocked signals do not interrupt any syscalls.
 829                  * In this case syscalls don't return ERESTARTfoo codes.
 830                  *
 831                  * Deadly signals set to SIG_DFL interrupt syscalls
 832                  * and kill the process regardless of which of the codes below
 833                  * is returned by the interrupted syscall.
 834                  * In some cases, kernel forces a kernel-generated deadly
 835                  * signal to be unblocked and set to SIG_DFL (and thus cause
 836                  * death) if it is blocked or SIG_IGNed: for example, SIGSEGV
 837                  * or SIGILL. (The alternative is to leave process spinning
 838                  * forever on the faulty instruction - not useful).
 839                  *
 840                  * SIG_IGNed signals and non-deadly signals set to SIG_DFL
 841                  * (for example, SIGCHLD, SIGWINCH) interrupt syscalls,
 842                  * but kernel will always restart them.
 843                  */
 844                 case ERESTARTSYS:
 845                         /* Most common type of signal-interrupted syscall exit code.
 846                          * The system call will be restarted with the same arguments
 847                          * if SA_RESTART is set; otherwise, it will fail with EINTR.
 848                          */
 849                         tprints("= ? ERESTARTSYS (To be restarted if SA_RESTART is set)");
 850                         break;
 851                 case ERESTARTNOINTR:
 852                         /* Rare. For example, fork() returns this if interrupted.
 853                          * SA_RESTART is ignored (assumed set): the restart is unconditional.
 854                          */
 855                         tprints("= ? ERESTARTNOINTR (To be restarted)");
 856                         break;
 857                 case ERESTARTNOHAND:
 858                         /* pause(), rt_sigsuspend() etc use this code.
 859                          * SA_RESTART is ignored (assumed not set):
 860                          * syscall won't restart (will return EINTR instead)
 861                          * even after signal with SA_RESTART set. However,
 862                          * after SIG_IGN or SIG_DFL signal it will restart
 863                          * (thus the name "restart only if has no handler").
 864                          */
 865                         tprints("= ? ERESTARTNOHAND (To be restarted if no handler)");
 866                         break;
 867                 case ERESTART_RESTARTBLOCK:
 868                         /* Syscalls like nanosleep(), poll() which can't be
 869                          * restarted with their original arguments use this
 870                          * code. Kernel will execute restart_syscall() instead,
 871                          * which changes arguments before restarting syscall.
 872                          * SA_RESTART is ignored (assumed not set) similarly
 873                          * to ERESTARTNOHAND. (Kernel can't honor SA_RESTART
 874                          * since restart data is saved in "restart block"
 875                          * in task struct, and if signal handler uses a syscall
 876                          * which in turn saves another such restart block,
 877                          * old data is lost and restart becomes impossible)
 878                          */
 879                         tprints("= ? ERESTART_RESTARTBLOCK (Interrupted by signal)");
 880                         break;
 881                 default:
 882                         u_error_str = err_name(u_error);
 883                         if (u_error_str)
 884                                 tprintf("= -1 %s (%s)",
 885                                         u_error_str, strerror(u_error));
 886                         else
 887                                 tprintf("= -1 %lu (%s)",
 888                                         u_error, strerror(u_error));
 889                         break;
 890                 }
 891                 if (syscall_fault_injected(tcp))
 892                         tprintf(" (INJECTED)");
 893                 if ((sys_res & RVAL_STR) && tcp->auxstr)
 894                         tprintf(" (%s)", tcp->auxstr);
 895         }
 896         else {
 897                 if (sys_res & RVAL_NONE)
 898                         tprints("= ?");
 899                 else {
 900                         switch (sys_res & RVAL_MASK) {
 901                         case RVAL_HEX:
 902 #if SUPPORTED_PERSONALITIES > 1
 903                                 if (current_wordsize < sizeof(long))
 904                                         tprintf("= %#x",
 905                                                 (unsigned int) tcp->u_rval);
 906                                 else
 907 #endif
 908                                         tprintf("= %#lx", tcp->u_rval);
 909                                 break;
 910                         case RVAL_OCTAL:
 911                                 tprints("= ");
 912                                 print_numeric_long_umask(tcp->u_rval);
 913                                 break;
 914                         case RVAL_UDECIMAL:
 915 #if SUPPORTED_PERSONALITIES > 1
 916                                 if (current_wordsize < sizeof(long))
 917                                         tprintf("= %u",
 918                                                 (unsigned int) tcp->u_rval);
 919                                 else
 920 #endif
 921                                         tprintf("= %lu", tcp->u_rval);
 922                                 break;
 923                         case RVAL_DECIMAL:
 924                                 tprintf("= %ld", tcp->u_rval);
 925                                 break;
 926                         case RVAL_FD:
 927                                 if (show_fd_path) {
 928                                         tprints("= ");
 929                                         printfd(tcp, tcp->u_rval);
 930                                 }
 931                                 else
 932                                         tprintf("= %ld", tcp->u_rval);
 933                                 break;
 934 #if HAVE_STRUCT_TCB_EXT_ARG
 935                         /*
 936                         case RVAL_LHEX:
 937                                 tprintf("= %#llx", tcp->u_lrval);
 938                                 break;
 939                         case RVAL_LOCTAL:
 940                                 tprintf("= %#llo", tcp->u_lrval);
 941                                 break;
 942                         */
 943                         case RVAL_LUDECIMAL:
 944                                 tprintf("= %llu", tcp->u_lrval);
 945                                 break;
 946                         /*
 947                         case RVAL_LDECIMAL:
 948                                 tprintf("= %lld", tcp->u_lrval);
 949                                 break;
 950                         */
 951 #endif /* HAVE_STRUCT_TCB_EXT_ARG */
 952                         default:
 953                                 error_msg("invalid rval format");
 954                                 break;
 955                         }
 956                 }
 957                 if ((sys_res & RVAL_STR) && tcp->auxstr)
 958                         tprintf(" (%s)", tcp->auxstr);
 959         }
 960         if (Tflag) {
 961                 tv_sub(&tv, &tv, &tcp->etime);
 962                 tprintf(" <%ld.%06ld>",
 963                         (long) tv.tv_sec, (long) tv.tv_usec);
 964         }
 965         tprints("\n");
 966         dumpio(tcp);
 967         line_ended();
 968
 969 #ifdef USE_LIBUNWIND
 970         if (stack_trace_enabled)
 971                 unwind_print_stacktrace(tcp);
 972 #endif
 973
 974  ret:
 975         tcp->flags &= ~(TCB_INSYSCALL | TCB_FAULT_INJ);
 976         tcp->sys_func_rval = 0;
 977         free_tcb_priv_data(tcp);
 978         return 0;
 979 }
 980
 981 int
 982 trace_syscall(struct tcb *tcp)
 983 {
 984         return exiting(tcp) ?
 985                 trace_syscall_exiting(tcp) : trace_syscall_entering(tcp);
 986 }
 987
 988 bool
 989 is_erestart(struct tcb *tcp)
 990 {
 991         switch (tcp->u_error) {
 992                 case ERESTARTSYS:
 993                 case ERESTARTNOINTR:
 994                 case ERESTARTNOHAND:
 995                 case ERESTART_RESTARTBLOCK:
 996                         return true;
 997                 default:
 998                         return false;
 999         }
1000 }
1001
1002 static unsigned long saved_u_error;
1003
1004 void
1005 temporarily_clear_syserror(struct tcb *tcp)
1006 {
1007         saved_u_error = tcp->u_error;
1008         tcp->u_error = 0;
1009 }
1010
1011 void
1012 restore_cleared_syserror(struct tcb *tcp)
1013 {
1014         tcp->u_error = saved_u_error;
1015 }
1016
1017 /*
1018  * Check the syscall return value register value for whether it is
1019  * a negated errno code indicating an error, or a success return value.
1020  */
1021 static inline bool
1022 is_negated_errno(kernel_ulong_t val)
1023 {
1024         /* Linux kernel defines MAX_ERRNO to 4095. */
1025         kernel_ulong_t max = -(kernel_long_t) 4095;
1026
1027 #ifndef current_klongsize
1028         if (current_klongsize < sizeof(val)) {
1029                 val = (uint32_t) val;
1030                 max = (uint32_t) max;
1031         }
1032 #endif /* !current_klongsize */
1033
1034         return val >= max;
1035 }
1036
1037 #include "arch_regs.c"
1038
1039 #ifdef HAVE_GETRVAL2
1040 # include "arch_getrval2.c"
1041 #endif
1042
1043 void
1044 print_pc(struct tcb *tcp)
1045 {
1046 #if defined ARCH_PC_REG
1047 # define ARCH_GET_PC 0
1048 #elif defined ARCH_PC_PEEK_ADDR
1049         long pc;
1050 # define ARCH_PC_REG pc
1051 # define ARCH_GET_PC upeek(tcp->pid, ARCH_PC_PEEK_ADDR, &pc)
1052 #else
1053 # error Neither ARCH_PC_REG nor ARCH_PC_PEEK_ADDR is defined
1054 #endif
1055         if (get_regs_error || ARCH_GET_PC)
1056                 tprints(current_wordsize == 4 ? "[????????] "
1057                                               : "[????????????????] ");
1058         else
1059                 tprintf(current_wordsize == 4 ? "[%08lx] " : "[%016lx] ",
1060                         (unsigned long) ARCH_PC_REG);
1061 }
1062
1063 #include "getregs_old.h"
1064
1065 #undef ptrace_getregset_or_getregs
1066 #undef ptrace_setregset_or_setregs
1067 #ifdef ARCH_REGS_FOR_GETREGSET
1068
1069 # define ptrace_getregset_or_getregs ptrace_getregset
1070 static long
1071 ptrace_getregset(pid_t pid)
1072 {
1073 # ifdef ARCH_IOVEC_FOR_GETREGSET
1074         /* variable iovec */
1075         ARCH_IOVEC_FOR_GETREGSET.iov_len = sizeof(ARCH_REGS_FOR_GETREGSET);
1076         return ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS,
1077                       &ARCH_IOVEC_FOR_GETREGSET);
1078 # else
1079         /* constant iovec */
1080         static struct iovec io = {
1081                 .iov_base = &ARCH_REGS_FOR_GETREGSET,
1082                 .iov_len = sizeof(ARCH_REGS_FOR_GETREGSET)
1083         };
1084         return ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &io);
1085
1086 # endif
1087 }
1088
1089 # ifndef HAVE_GETREGS_OLD
1090 #  define ptrace_setregset_or_setregs ptrace_setregset
1091 static int
1092 ptrace_setregset(pid_t pid)
1093 {
1094 #  ifdef ARCH_IOVEC_FOR_GETREGSET
1095         /* variable iovec */
1096         return ptrace(PTRACE_SETREGSET, pid, NT_PRSTATUS,
1097                       &ARCH_IOVEC_FOR_GETREGSET);
1098 #  else
1099         /* constant iovec */
1100         static struct iovec io = {
1101                 .iov_base = &ARCH_REGS_FOR_GETREGSET,
1102                 .iov_len = sizeof(ARCH_REGS_FOR_GETREGSET)
1103         };
1104         return ptrace(PTRACE_SETREGSET, pid, NT_PRSTATUS, &io);
1105 #  endif
1106 }
1107 # endif /* !HAVE_GETREGS_OLD */
1108
1109 #elif defined ARCH_REGS_FOR_GETREGS
1110
1111 # define ptrace_getregset_or_getregs ptrace_getregs
1112 static long
1113 ptrace_getregs(pid_t pid)
1114 {
1115 # if defined SPARC || defined SPARC64
1116         /* SPARC systems have the meaning of data and addr reversed */
1117         return ptrace(PTRACE_GETREGS, pid, (void *) &ARCH_REGS_FOR_GETREGS, 0);
1118 # else
1119         return ptrace(PTRACE_GETREGS, pid, NULL, &ARCH_REGS_FOR_GETREGS);
1120 # endif
1121 }
1122
1123 # ifndef HAVE_GETREGS_OLD
1124 #  define ptrace_setregset_or_setregs ptrace_setregs
1125 static int
1126 ptrace_setregs(pid_t pid)
1127 {
1128 #  if defined SPARC || defined SPARC64
1129         /* SPARC systems have the meaning of data and addr reversed */
1130         return ptrace(PTRACE_SETREGS, pid, (void *) &ARCH_REGS_FOR_GETREGS, 0);
1131 #  else
1132         return ptrace(PTRACE_SETREGS, pid, NULL, &ARCH_REGS_FOR_GETREGS);
1133 #  endif
1134 }
1135 # endif /* !HAVE_GETREGS_OLD */
1136
1137 #endif /* ARCH_REGS_FOR_GETREGSET || ARCH_REGS_FOR_GETREGS */
1138
1139 void
1140 get_regs(pid_t pid)
1141 {
1142 #undef USE_GET_SYSCALL_RESULT_REGS
1143 #ifdef ptrace_getregset_or_getregs
1144
1145 # ifdef HAVE_GETREGS_OLD
1146         /*
1147          * Try PTRACE_GETREGSET/PTRACE_GETREGS first,
1148          * fallback to getregs_old.
1149          */
1150         static int use_getregs_old;
1151         if (use_getregs_old < 0) {
1152                 get_regs_error = ptrace_getregset_or_getregs(pid);
1153                 return;
1154         } else if (use_getregs_old == 0) {
1155                 get_regs_error = ptrace_getregset_or_getregs(pid);
1156                 if (get_regs_error >= 0) {
1157                         use_getregs_old = -1;
1158                         return;
1159                 }
1160                 if (errno == EPERM || errno == ESRCH)
1161                         return;
1162                 use_getregs_old = 1;
1163         }
1164         get_regs_error = getregs_old(pid);
1165 # else /* !HAVE_GETREGS_OLD */
1166         /* Assume that PTRACE_GETREGSET/PTRACE_GETREGS works. */
1167         get_regs_error = ptrace_getregset_or_getregs(pid);
1168 # endif /* !HAVE_GETREGS_OLD */
1169
1170 #else /* !ptrace_getregset_or_getregs */
1171
1172 # define USE_GET_SYSCALL_RESULT_REGS 1
1173 # warning get_regs is not implemented for this architecture yet
1174         get_regs_error = 0;
1175
1176 #endif /* !ptrace_getregset_or_getregs */
1177 }
1178
1179 #ifdef ptrace_setregset_or_setregs
1180 static int
1181 set_regs(pid_t pid)
1182 {
1183         return ptrace_setregset_or_setregs(pid);
1184 }
1185 #endif /* ptrace_setregset_or_setregs */
1186
1187 struct sysent_buf {
1188         struct tcb *tcp;
1189         struct_sysent ent;
1190         char buf[sizeof("syscall_%lu") + sizeof(long) * 3];
1191 };
1192
1193 static void
1194 free_sysent_buf(void *ptr)
1195 {
1196         struct sysent_buf *s = ptr;
1197         s->tcp->s_prev_ent = s->tcp->s_ent = NULL;
1198         free(ptr);
1199 }
1200
1201 /*
1202  * Returns:
1203  * 0: "ignore this ptrace stop", bail out of trace_syscall_entering() silently.
1204  * 1: ok, continue in trace_syscall_entering().
1205  * other: error, trace_syscall_entering() should print error indicator
1206  *    ("????" etc) and bail out.
1207  */
1208 int
1209 get_scno(struct tcb *tcp)
1210 {
1211         if (get_regs_error)
1212                 return -1;
1213
1214         int rc = arch_get_scno(tcp);
1215         if (rc != 1)
1216                 return rc;
1217
1218         if (scno_is_valid(tcp->scno)) {
1219                 tcp->s_ent = &sysent[tcp->scno];
1220                 tcp->qual_flg = qual_flags(tcp->scno);
1221         } else {
1222                 struct sysent_buf *s = xcalloc(1, sizeof(*s));
1223
1224                 s->tcp = tcp;
1225                 s->ent.nargs = MAX_ARGS;
1226                 s->ent.sen = SEN_printargs;
1227                 s->ent.sys_func = printargs;
1228                 s->ent.sys_name = s->buf;
1229                 sprintf(s->buf, "syscall_%lu", shuffle_scno(tcp->scno));
1230
1231                 tcp->s_ent = &s->ent;
1232                 tcp->qual_flg = QUAL_RAW | DEFAULT_QUAL_FLAGS;
1233
1234                 set_tcb_priv_data(tcp, s, free_sysent_buf);
1235
1236                 if (debug_flag)
1237                         error_msg("pid %d invalid syscall %ld", tcp->pid, tcp->scno);
1238         }
1239         return 1;
1240 }
1241
1242 #ifdef USE_GET_SYSCALL_RESULT_REGS
1243 static int get_syscall_result_regs(struct tcb *);
1244 #endif
1245
1246 /* Returns:
1247  * 1: ok, continue in trace_syscall_exiting().
1248  * -1: error, trace_syscall_exiting() should print error indicator
1249  *    ("????" etc) and bail out.
1250  */
1251 static int
1252 get_syscall_result(struct tcb *tcp)
1253 {
1254 #ifdef USE_GET_SYSCALL_RESULT_REGS
1255         if (get_syscall_result_regs(tcp))
1256                 return -1;
1257 #endif
1258         tcp->u_error = 0;
1259         get_error(tcp, !(tcp->s_ent->sys_flags & SYSCALL_NEVER_FAILS));
1260
1261         return 1;
1262 }
1263
1264 #include "get_scno.c"
1265 #include "set_scno.c"
1266 #include "get_syscall_args.c"
1267 #ifdef USE_GET_SYSCALL_RESULT_REGS
1268 # include "get_syscall_result.c"
1269 #endif
1270 #include "get_error.c"
1271 #include "set_error.c"
1272 #ifdef HAVE_GETREGS_OLD
1273 # include "getregs_old.c"
1274 #endif
1275
1276 const char *
1277 syscall_name(kernel_scno_t scno)
1278 {
1279 #if defined X32_PERSONALITY_NUMBER && defined __X32_SYSCALL_BIT
1280         if (current_personality == X32_PERSONALITY_NUMBER)
1281                 scno &= ~__X32_SYSCALL_BIT;
1282 #endif
1283         return scno_is_valid(scno) ? sysent[scno].sys_name: NULL;
1284 }