kernel/arch/um/os-Linux/skas/process.c

   1 /*
   2  * Copyright (C) 2002- 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <stdlib.h>
   7 #include <unistd.h>
   8 #include <sched.h>
   9 #include <errno.h>
  10 #include <string.h>
  11 #include <sys/mman.h>
  12 #include <sys/wait.h>
  13 #include <asm/unistd.h>
  14 #include <as-layout.h>
  15 #include <init.h>
  16 #include <kern_util.h>
  17 #include <mem.h>
  18 #include <os.h>
  19 #include <ptrace_user.h>
  20 #include <registers.h>
  21 #include <skas.h>
  22 #include <sysdep/stub.h>
  23
  24 int is_skas_winch(int pid, int fd, void *data)
  25 {
  26         return pid == getpgrp();
  27 }
  28
  29 static int ptrace_dump_regs(int pid)
  30 {
  31         unsigned long regs[MAX_REG_NR];
  32         int i;
  33
  34         if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
  35                 return -errno;
  36
  37         printk(UM_KERN_ERR "Stub registers -\n");
  38         for (i = 0; i < ARRAY_SIZE(regs); i++)
  39                 printk(UM_KERN_ERR "\t%d - %lx\n", i, regs[i]);
  40
  41         return 0;
  42 }
  43
  44 /*
  45  * Signals that are OK to receive in the stub - we'll just continue it.
  46  * SIGWINCH will happen when UML is inside a detached screen.
  47  */
  48 #define STUB_SIG_MASK ((1 << SIGVTALRM) | (1 << SIGWINCH))
  49
  50 /* Signals that the stub will finish with - anything else is an error */
  51 #define STUB_DONE_MASK (1 << SIGTRAP)
  52
  53 void wait_stub_done(int pid)
  54 {
  55         int n, status, err;
  56
  57         while (1) {
  58                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
  59                 if ((n < 0) || !WIFSTOPPED(status))
  60                         goto bad_wait;
  61
  62                 if (((1 << WSTOPSIG(status)) & STUB_SIG_MASK) == 0)
  63                         break;
  64
  65                 err = ptrace(PTRACE_CONT, pid, 0, 0);
  66                 if (err) {
  67                         printk(UM_KERN_ERR "wait_stub_done : continue failed, "
  68                                "errno = %d\n", errno);
  69                         fatal_sigsegv();
  70                 }
  71         }
  72
  73         if (((1 << WSTOPSIG(status)) & STUB_DONE_MASK) != 0)
  74                 return;
  75
  76 bad_wait:
  77         err = ptrace_dump_regs(pid);
  78         if (err)
  79                 printk(UM_KERN_ERR "Failed to get registers from stub, "
  80                        "errno = %d\n", -err);
  81         printk(UM_KERN_ERR "wait_stub_done : failed to wait for SIGTRAP, "
  82                "pid = %d, n = %d, errno = %d, status = 0x%x\n", pid, n, errno,
  83                status);
  84         fatal_sigsegv();
  85 }
  86
  87 extern unsigned long current_stub_stack(void);
  88
  89 static void get_skas_faultinfo(int pid, struct faultinfo *fi)
  90 {
  91         int err;
  92         unsigned long fpregs[FP_SIZE];
  93
  94         err = get_fp_registers(pid, fpregs);
  95         if (err < 0) {
  96                 printk(UM_KERN_ERR "save_fp_registers returned %d\n",
  97                        err);
  98                 fatal_sigsegv();
  99         }
 100         err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);
 101         if (err) {
 102                 printk(UM_KERN_ERR "Failed to continue stub, pid = %d, "
 103                        "errno = %d\n", pid, errno);
 104                 fatal_sigsegv();
 105         }
 106         wait_stub_done(pid);
 107
 108         /*
 109          * faultinfo is prepared by the stub-segv-handler at start of
 110          * the stub stack page. We just have to copy it.
 111          */
 112         memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));
 113
 114         err = put_fp_registers(pid, fpregs);
 115         if (err < 0) {
 116                 printk(UM_KERN_ERR "put_fp_registers returned %d\n",
 117                        err);
 118                 fatal_sigsegv();
 119         }
 120 }
 121
 122 static void handle_segv(int pid, struct uml_pt_regs * regs)
 123 {
 124         get_skas_faultinfo(pid, &regs->faultinfo);
 125         segv(regs->faultinfo, 0, 1, NULL);
 126 }
 127
 128 /*
 129  * To use the same value of using_sysemu as the caller, ask it that value
 130  * (in local_using_sysemu
 131  */
 132 static void handle_trap(int pid, struct uml_pt_regs *regs,
 133                         int local_using_sysemu)
 134 {
 135         int err, status;
 136
 137         if ((UPT_IP(regs) >= STUB_START) && (UPT_IP(regs) < STUB_END))
 138                 fatal_sigsegv();
 139
 140         /* Mark this as a syscall */
 141         UPT_SYSCALL_NR(regs) = PT_SYSCALL_NR(regs->gp);
 142
 143         if (!local_using_sysemu)
 144         {
 145                 err = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_NR_OFFSET,
 146                              __NR_getpid);
 147                 if (err < 0) {
 148                         printk(UM_KERN_ERR "handle_trap - nullifying syscall "
 149                                "failed, errno = %d\n", errno);
 150                         fatal_sigsegv();
 151                 }
 152
 153                 err = ptrace(PTRACE_SYSCALL, pid, 0, 0);
 154                 if (err < 0) {
 155                         printk(UM_KERN_ERR "handle_trap - continuing to end of "
 156                                "syscall failed, errno = %d\n", errno);
 157                         fatal_sigsegv();
 158                 }
 159
 160                 CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
 161                 if ((err < 0) || !WIFSTOPPED(status) ||
 162                     (WSTOPSIG(status) != SIGTRAP + 0x80)) {
 163                         err = ptrace_dump_regs(pid);
 164                         if (err)
 165                                 printk(UM_KERN_ERR "Failed to get registers "
 166                                        "from process, errno = %d\n", -err);
 167                         printk(UM_KERN_ERR "handle_trap - failed to wait at "
 168                                "end of syscall, errno = %d, status = %d\n",
 169                                errno, status);
 170                         fatal_sigsegv();
 171                 }
 172         }
 173
 174         handle_syscall(regs);
 175 }
 176
 177 extern int __syscall_stub_start;
 178
 179 static int userspace_tramp(void *stack)
 180 {
 181         void *addr;
 182         int err, fd;
 183         unsigned long long offset;
 184
 185         ptrace(PTRACE_TRACEME, 0, 0, 0);
 186
 187         signal(SIGTERM, SIG_DFL);
 188         signal(SIGWINCH, SIG_IGN);
 189         err = set_interval();
 190         if (err) {
 191                 printk(UM_KERN_ERR "userspace_tramp - setting timer failed, "
 192                        "errno = %d\n", err);
 193                 exit(1);
 194         }
 195
 196         /*
 197          * This has a pte, but it can't be mapped in with the usual
 198          * tlb_flush mechanism because this is part of that mechanism
 199          */
 200         fd = phys_mapping(to_phys(&__syscall_stub_start), &offset);
 201         addr = mmap64((void *) STUB_CODE, UM_KERN_PAGE_SIZE,
 202                       PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset);
 203         if (addr == MAP_FAILED) {
 204                 printk(UM_KERN_ERR "mapping mmap stub at 0x%lx failed, "
 205                        "errno = %d\n", STUB_CODE, errno);
 206                 exit(1);
 207         }
 208
 209         if (stack != NULL) {
 210                 fd = phys_mapping(to_phys(stack), &offset);
 211                 addr = mmap((void *) STUB_DATA,
 212                             UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
 213                             MAP_FIXED | MAP_SHARED, fd, offset);
 214                 if (addr == MAP_FAILED) {
 215                         printk(UM_KERN_ERR "mapping segfault stack "
 216                                "at 0x%lx failed, errno = %d\n",
 217                                STUB_DATA, errno);
 218                         exit(1);
 219                 }
 220         }
 221         if (stack != NULL) {
 222                 struct sigaction sa;
 223
 224                 unsigned long v = STUB_CODE +
 225                                   (unsigned long) stub_segv_handler -
 226                                   (unsigned long) &__syscall_stub_start;
 227
 228                 set_sigstack((void *) STUB_DATA, UM_KERN_PAGE_SIZE);
 229                 sigemptyset(&sa.sa_mask);
 230                 sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO;
 231                 sa.sa_sigaction = (void *) v;
 232                 sa.sa_restorer = NULL;
 233                 if (sigaction(SIGSEGV, &sa, NULL) < 0) {
 234                         printk(UM_KERN_ERR "userspace_tramp - setting SIGSEGV "
 235                                "handler failed - errno = %d\n", errno);
 236                         exit(1);
 237                 }
 238         }
 239
 240         kill(os_getpid(), SIGSTOP);
 241         return 0;
 242 }
 243
 244 /* Each element set once, and only accessed by a single processor anyway */
 245 #undef NR_CPUS
 246 #define NR_CPUS 1
 247 int userspace_pid[NR_CPUS];
 248
 249 int start_userspace(unsigned long stub_stack)
 250 {
 251         void *stack;
 252         unsigned long sp;
 253         int pid, status, n, flags, err;
 254
 255         stack = mmap(NULL, UM_KERN_PAGE_SIZE,
 256                      PROT_READ | PROT_WRITE | PROT_EXEC,
 257                      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 258         if (stack == MAP_FAILED) {
 259                 err = -errno;
 260                 printk(UM_KERN_ERR "start_userspace : mmap failed, "
 261                        "errno = %d\n", errno);
 262                 return err;
 263         }
 264
 265         sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
 266
 267         flags = CLONE_FILES | SIGCHLD;
 268
 269         pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
 270         if (pid < 0) {
 271                 err = -errno;
 272                 printk(UM_KERN_ERR "start_userspace : clone failed, "
 273                        "errno = %d\n", errno);
 274                 return err;
 275         }
 276
 277         do {
 278                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
 279                 if (n < 0) {
 280                         err = -errno;
 281                         printk(UM_KERN_ERR "start_userspace : wait failed, "
 282                                "errno = %d\n", errno);
 283                         goto out_kill;
 284                 }
 285         } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGVTALRM));
 286
 287         if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
 288                 err = -EINVAL;
 289                 printk(UM_KERN_ERR "start_userspace : expected SIGSTOP, got "
 290                        "status = %d\n", status);
 291                 goto out_kill;
 292         }
 293
 294         if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
 295                    (void *) PTRACE_O_TRACESYSGOOD) < 0) {
 296                 err = -errno;
 297                 printk(UM_KERN_ERR "start_userspace : PTRACE_OLDSETOPTIONS "
 298                        "failed, errno = %d\n", errno);
 299                 goto out_kill;
 300         }
 301
 302         if (munmap(stack, UM_KERN_PAGE_SIZE) < 0) {
 303                 err = -errno;
 304                 printk(UM_KERN_ERR "start_userspace : munmap failed, "
 305                        "errno = %d\n", errno);
 306                 goto out_kill;
 307         }
 308
 309         return pid;
 310
 311  out_kill:
 312         os_kill_ptraced_process(pid, 1);
 313         return err;
 314 }
 315
 316 void userspace(struct uml_pt_regs *regs)
 317 {
 318         struct itimerval timer;
 319         unsigned long long nsecs, now;
 320         int err, status, op, pid = userspace_pid[0];
 321         /* To prevent races if using_sysemu changes under us.*/
 322         int local_using_sysemu;
 323         siginfo_t si;
 324
 325         /* Handle any immediate reschedules or signals */
 326         interrupt_end();
 327
 328         if (getitimer(ITIMER_VIRTUAL, &timer))
 329                 printk(UM_KERN_ERR "Failed to get itimer, errno = %d\n", errno);
 330         nsecs = timer.it_value.tv_sec * UM_NSEC_PER_SEC +
 331                 timer.it_value.tv_usec * UM_NSEC_PER_USEC;
 332         nsecs += os_nsecs();
 333
 334         while (1) {
 335                 /*
 336                  * This can legitimately fail if the process loads a
 337                  * bogus value into a segment register.  It will
 338                  * segfault and PTRACE_GETREGS will read that value
 339                  * out of the process.  However, PTRACE_SETREGS will
 340                  * fail.  In this case, there is nothing to do but
 341                  * just kill the process.
 342                  */
 343                 if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp))
 344                         fatal_sigsegv();
 345
 346                 if (put_fp_registers(pid, regs->fp))
 347                         fatal_sigsegv();
 348
 349                 /* Now we set local_using_sysemu to be used for one loop */
 350                 local_using_sysemu = get_using_sysemu();
 351
 352                 op = SELECT_PTRACE_OPERATION(local_using_sysemu,
 353                                              singlestepping(NULL));
 354
 355                 if (ptrace(op, pid, 0, 0)) {
 356                         printk(UM_KERN_ERR "userspace - ptrace continue "
 357                                "failed, op = %d, errno = %d\n", op, errno);
 358                         fatal_sigsegv();
 359                 }
 360
 361                 CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
 362                 if (err < 0) {
 363                         printk(UM_KERN_ERR "userspace - wait failed, "
 364                                "errno = %d\n", errno);
 365                         fatal_sigsegv();
 366                 }
 367
 368                 regs->is_user = 1;
 369                 if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp)) {
 370                         printk(UM_KERN_ERR "userspace - PTRACE_GETREGS failed, "
 371                                "errno = %d\n", errno);
 372                         fatal_sigsegv();
 373                 }
 374
 375                 if (get_fp_registers(pid, regs->fp)) {
 376                         printk(UM_KERN_ERR "userspace -  get_fp_registers failed, "
 377                                "errno = %d\n", errno);
 378                         fatal_sigsegv();
 379                 }
 380
 381                 UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */
 382
 383                 if (WIFSTOPPED(status)) {
 384                         int sig = WSTOPSIG(status);
 385
 386                         ptrace(PTRACE_GETSIGINFO, pid, 0, (struct siginfo *)&si);
 387
 388                         switch (sig) {
 389                         case SIGSEGV:
 390                                 if (PTRACE_FULL_FAULTINFO) {
 391                                         get_skas_faultinfo(pid,
 392                                                            &regs->faultinfo);
 393                                         (*sig_info[SIGSEGV])(SIGSEGV, (struct siginfo *)&si,
 394                                                              regs);
 395                                 }
 396                                 else handle_segv(pid, regs);
 397                                 break;
 398                         case SIGTRAP + 0x80:
 399                                 handle_trap(pid, regs, local_using_sysemu);
 400                                 break;
 401                         case SIGTRAP:
 402                                 relay_signal(SIGTRAP, (struct siginfo *)&si, regs);
 403                                 break;
 404                         case SIGVTALRM:
 405                                 now = os_nsecs();
 406                                 if (now < nsecs)
 407                                         break;
 408                                 block_signals();
 409                                 (*sig_info[sig])(sig, (struct siginfo *)&si, regs);
 410                                 unblock_signals();
 411                                 nsecs = timer.it_value.tv_sec *
 412                                         UM_NSEC_PER_SEC +
 413                                         timer.it_value.tv_usec *
 414                                         UM_NSEC_PER_USEC;
 415                                 nsecs += os_nsecs();
 416                                 break;
 417                         case SIGIO:
 418                         case SIGILL:
 419                         case SIGBUS:
 420                         case SIGFPE:
 421                         case SIGWINCH:
 422                                 block_signals();
 423                                 (*sig_info[sig])(sig, (struct siginfo *)&si, regs);
 424                                 unblock_signals();
 425                                 break;
 426                         default:
 427                                 printk(UM_KERN_ERR "userspace - child stopped "
 428                                        "with signal %d\n", sig);
 429                                 fatal_sigsegv();
 430                         }
 431                         pid = userspace_pid[0];
 432                         interrupt_end();
 433
 434                         /* Avoid -ERESTARTSYS handling in host */
 435                         if (PT_SYSCALL_NR_OFFSET != PT_SYSCALL_RET_OFFSET)
 436                                 PT_SYSCALL_NR(regs->gp) = -1;
 437                 }
 438         }
 439 }
 440
 441 static unsigned long thread_regs[MAX_REG_NR];
 442 static unsigned long thread_fp_regs[FP_SIZE];
 443
 444 static int __init init_thread_regs(void)
 445 {
 446         get_safe_registers(thread_regs, thread_fp_regs);
 447         /* Set parent's instruction pointer to start of clone-stub */
 448         thread_regs[REGS_IP_INDEX] = STUB_CODE +
 449                                 (unsigned long) stub_clone_handler -
 450                                 (unsigned long) &__syscall_stub_start;
 451         thread_regs[REGS_SP_INDEX] = STUB_DATA + UM_KERN_PAGE_SIZE -
 452                 sizeof(void *);
 453 #ifdef __SIGNAL_FRAMESIZE
 454         thread_regs[REGS_SP_INDEX] -= __SIGNAL_FRAMESIZE;
 455 #endif
 456         return 0;
 457 }
 458
 459 __initcall(init_thread_regs);
 460
 461 int copy_context_skas0(unsigned long new_stack, int pid)
 462 {
 463         struct timeval tv = { .tv_sec = 0, .tv_usec = UM_USEC_PER_SEC / UM_HZ };
 464         int err;
 465         unsigned long current_stack = current_stub_stack();
 466         struct stub_data *data = (struct stub_data *) current_stack;
 467         struct stub_data *child_data = (struct stub_data *) new_stack;
 468         unsigned long long new_offset;
 469         int new_fd = phys_mapping(to_phys((void *)new_stack), &new_offset);
 470
 471         /*
 472          * prepare offset and fd of child's stack as argument for parent's
 473          * and child's mmap2 calls
 474          */
 475         *data = ((struct stub_data) { .offset   = MMAP_OFFSET(new_offset),
 476                                       .fd       = new_fd,
 477                                       .timer    = ((struct itimerval)
 478                                                    { .it_value = tv,
 479                                                      .it_interval = tv }) });
 480
 481         err = ptrace_setregs(pid, thread_regs);
 482         if (err < 0) {
 483                 err = -errno;
 484                 printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_SETREGS "
 485                        "failed, pid = %d, errno = %d\n", pid, -err);
 486                 return err;
 487         }
 488
 489         err = put_fp_registers(pid, thread_fp_regs);
 490         if (err < 0) {
 491                 printk(UM_KERN_ERR "copy_context_skas0 : put_fp_registers "
 492                        "failed, pid = %d, err = %d\n", pid, err);
 493                 return err;
 494         }
 495
 496         /* set a well known return code for detection of child write failure */
 497         child_data->err = 12345678;
 498
 499         /*
 500          * Wait, until parent has finished its work: read child's pid from
 501          * parent's stack, and check, if bad result.
 502          */
 503         err = ptrace(PTRACE_CONT, pid, 0, 0);
 504         if (err) {
 505                 err = -errno;
 506                 printk(UM_KERN_ERR "Failed to continue new process, pid = %d, "
 507                        "errno = %d\n", pid, errno);
 508                 return err;
 509         }
 510
 511         wait_stub_done(pid);
 512
 513         pid = data->err;
 514         if (pid < 0) {
 515                 printk(UM_KERN_ERR "copy_context_skas0 - stub-parent reports "
 516                        "error %d\n", -pid);
 517                 return pid;
 518         }
 519
 520         /*
 521          * Wait, until child has finished too: read child's result from
 522          * child's stack and check it.
 523          */
 524         wait_stub_done(pid);
 525         if (child_data->err != STUB_DATA) {
 526                 printk(UM_KERN_ERR "copy_context_skas0 - stub-child reports "
 527                        "error %ld\n", child_data->err);
 528                 err = child_data->err;
 529                 goto out_kill;
 530         }
 531
 532         if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
 533                    (void *)PTRACE_O_TRACESYSGOOD) < 0) {
 534                 err = -errno;
 535                 printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_OLDSETOPTIONS "
 536                        "failed, errno = %d\n", errno);
 537                 goto out_kill;
 538         }
 539
 540         return pid;
 541
 542  out_kill:
 543         os_kill_ptraced_process(pid, 1);
 544         return err;
 545 }
 546
 547 void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
 548 {
 549         (*buf)[0].JB_IP = (unsigned long) handler;
 550         (*buf)[0].JB_SP = (unsigned long) stack + UM_THREAD_SIZE -
 551                 sizeof(void *);
 552 }
 553
 554 #define INIT_JMP_NEW_THREAD 0
 555 #define INIT_JMP_CALLBACK 1
 556 #define INIT_JMP_HALT 2
 557 #define INIT_JMP_REBOOT 3
 558
 559 void switch_threads(jmp_buf *me, jmp_buf *you)
 560 {
 561         if (UML_SETJMP(me) == 0)
 562                 UML_LONGJMP(you, 1);
 563 }
 564
 565 static jmp_buf initial_jmpbuf;
 566
 567 /* XXX Make these percpu */
 568 static void (*cb_proc)(void *arg);
 569 static void *cb_arg;
 570 static jmp_buf *cb_back;
 571
 572 int start_idle_thread(void *stack, jmp_buf *switch_buf)
 573 {
 574         int n;
 575
 576         set_handler(SIGWINCH);
 577
 578         /*
 579          * Can't use UML_SETJMP or UML_LONGJMP here because they save
 580          * and restore signals, with the possible side-effect of
 581          * trying to handle any signals which came when they were
 582          * blocked, which can't be done on this stack.
 583          * Signals must be blocked when jumping back here and restored
 584          * after returning to the jumper.
 585          */
 586         n = setjmp(initial_jmpbuf);
 587         switch (n) {
 588         case INIT_JMP_NEW_THREAD:
 589                 (*switch_buf)[0].JB_IP = (unsigned long) uml_finishsetup;
 590                 (*switch_buf)[0].JB_SP = (unsigned long) stack +
 591                         UM_THREAD_SIZE - sizeof(void *);
 592                 break;
 593         case INIT_JMP_CALLBACK:
 594                 (*cb_proc)(cb_arg);
 595                 longjmp(*cb_back, 1);
 596                 break;
 597         case INIT_JMP_HALT:
 598                 kmalloc_ok = 0;
 599                 return 0;
 600         case INIT_JMP_REBOOT:
 601                 kmalloc_ok = 0;
 602                 return 1;
 603         default:
 604                 printk(UM_KERN_ERR "Bad sigsetjmp return in "
 605                        "start_idle_thread - %d\n", n);
 606                 fatal_sigsegv();
 607         }
 608         longjmp(*switch_buf, 1);
 609 }
 610
 611 void initial_thread_cb_skas(void (*proc)(void *), void *arg)
 612 {
 613         jmp_buf here;
 614
 615         cb_proc = proc;
 616         cb_arg = arg;
 617         cb_back = &here;
 618
 619         block_signals();
 620         if (UML_SETJMP(&here) == 0)
 621                 UML_LONGJMP(&initial_jmpbuf, INIT_JMP_CALLBACK);
 622         unblock_signals();
 623
 624         cb_proc = NULL;
 625         cb_arg = NULL;
 626         cb_back = NULL;
 627 }
 628
 629 void halt_skas(void)
 630 {
 631         block_signals();
 632         UML_LONGJMP(&initial_jmpbuf, INIT_JMP_HALT);
 633 }
 634
 635 void reboot_skas(void)
 636 {
 637         block_signals();
 638         UML_LONGJMP(&initial_jmpbuf, INIT_JMP_REBOOT);
 639 }
 640
 641 void __switch_mm(struct mm_id *mm_idp)
 642 {
 643         userspace_pid[0] = mm_idp->u.pid;
 644 }