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/ptrace.h>
  13 #include <sys/wait.h>
  14 #include <asm/unistd.h>
  15 #include "as-layout.h"
  16 #include "chan_user.h"
  17 #include "kern_constants.h"
  18 #include "mem.h"
  19 #include "os.h"
  20 #include "process.h"
  21 #include "proc_mm.h"
  22 #include "ptrace_user.h"
  23 #include "registers.h"
  24 #include "skas.h"
  25 #include "skas_ptrace.h"
  26 #include "user.h"
  27 #include "sysdep/stub.h"
  28
  29 int is_skas_winch(int pid, int fd, void *data)
  30 {
  31         if (pid != getpgrp())
  32                 return 0;
  33
  34         register_winch_irq(-1, fd, -1, data, 0);
  35         return 1;
  36 }
  37
  38 static int ptrace_dump_regs(int pid)
  39 {
  40         unsigned long regs[MAX_REG_NR];
  41         int i;
  42
  43         if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
  44                 return -errno;
  45
  46         printk(UM_KERN_ERR "Stub registers -\n");
  47         for (i = 0; i < ARRAY_SIZE(regs); i++)
  48                 printk(UM_KERN_ERR "\t%d - %lx\n", i, regs[i]);
  49
  50         return 0;
  51 }
  52
  53 /*
  54  * Signals that are OK to receive in the stub - we'll just continue it.
  55  * SIGWINCH will happen when UML is inside a detached screen.
  56  */
  57 #define STUB_SIG_MASK ((1 << SIGVTALRM) | (1 << SIGWINCH))
  58
  59 /* Signals that the stub will finish with - anything else is an error */
  60 #define STUB_DONE_MASK ((1 << SIGUSR1) | (1 << SIGTRAP))
  61
  62 void wait_stub_done(int pid)
  63 {
  64         int n, status, err;
  65
  66         while (1) {
  67                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
  68                 if ((n < 0) || !WIFSTOPPED(status))
  69                         goto bad_wait;
  70
  71                 if (((1 << WSTOPSIG(status)) & STUB_SIG_MASK) == 0)
  72                         break;
  73
  74                 err = ptrace(PTRACE_CONT, pid, 0, 0);
  75                 if (err)
  76                         panic("wait_stub_done : continue failed, errno = %d\n",
  77                               errno);
  78         }
  79
  80         if (((1 << WSTOPSIG(status)) & STUB_DONE_MASK) != 0)
  81                 return;
  82
  83 bad_wait:
  84         err = ptrace_dump_regs(pid);
  85         if (err)
  86                 printk(UM_KERN_ERR "Failed to get registers from stub, "
  87                        "errno = %d\n", -err);
  88         panic("wait_stub_done : failed to wait for SIGUSR1/SIGTRAP, pid = %d, "
  89               "n = %d, errno = %d, status = 0x%x\n", pid, n, errno, status);
  90 }
  91
  92 extern unsigned long current_stub_stack(void);
  93
  94 void get_skas_faultinfo(int pid, struct faultinfo * fi)
  95 {
  96         int err;
  97
  98         if (ptrace_faultinfo) {
  99                 err = ptrace(PTRACE_FAULTINFO, pid, 0, fi);
 100                 if (err)
 101                         panic("get_skas_faultinfo - PTRACE_FAULTINFO failed, "
 102                               "errno = %d\n", errno);
 103
 104                 /* Special handling for i386, which has different structs */
 105                 if (sizeof(struct ptrace_faultinfo) < sizeof(struct faultinfo))
 106                         memset((char *)fi + sizeof(struct ptrace_faultinfo), 0,
 107                                sizeof(struct faultinfo) -
 108                                sizeof(struct ptrace_faultinfo));
 109         }
 110         else {
 111                 err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);
 112                 if (err)
 113                         panic("Failed to continue stub, pid = %d, errno = %d\n",
 114                               pid, errno);
 115                 wait_stub_done(pid);
 116
 117                 /*
 118                  * faultinfo is prepared by the stub-segv-handler at start of
 119                  * the stub stack page. We just have to copy it.
 120                  */
 121                 memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));
 122         }
 123 }
 124
 125 static void handle_segv(int pid, struct uml_pt_regs * regs)
 126 {
 127         get_skas_faultinfo(pid, &regs->faultinfo);
 128         segv(regs->faultinfo, 0, 1, NULL);
 129 }
 130
 131 /*
 132  * To use the same value of using_sysemu as the caller, ask it that value
 133  * (in local_using_sysemu
 134  */
 135 static void handle_trap(int pid, struct uml_pt_regs *regs,
 136                         int local_using_sysemu)
 137 {
 138         int err, status;
 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_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
 146                              __NR_getpid);
 147                 if (err < 0)
 148                         panic("handle_trap - nullifying syscall failed, "
 149                               "errno = %d\n", errno);
 150
 151                 err = ptrace(PTRACE_SYSCALL, pid, 0, 0);
 152                 if (err < 0)
 153                         panic("handle_trap - continuing to end of syscall "
 154                               "failed, errno = %d\n", errno);
 155
 156                 CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED));
 157                 if ((err < 0) || !WIFSTOPPED(status) ||
 158                    (WSTOPSIG(status) != SIGTRAP + 0x80)) {
 159                         err = ptrace_dump_regs(pid);
 160                         if (err)
 161                                 printk(UM_KERN_ERR "Failed to get registers "
 162                                        "from process, errno = %d\n", -err);
 163                         panic("handle_trap - failed to wait at end of syscall, "
 164                               "errno = %d, status = %d\n", errno, status);
 165                 }
 166         }
 167
 168         handle_syscall(regs);
 169 }
 170
 171 extern int __syscall_stub_start;
 172
 173 static int userspace_tramp(void *stack)
 174 {
 175         void *addr;
 176         int err;
 177
 178         ptrace(PTRACE_TRACEME, 0, 0, 0);
 179
 180         init_new_thread_signals();
 181         err = set_interval();
 182         if (err)
 183                 panic("userspace_tramp - setting timer failed, errno = %d\n",
 184                       err);
 185
 186         if (!proc_mm) {
 187                 /*
 188                  * This has a pte, but it can't be mapped in with the usual
 189                  * tlb_flush mechanism because this is part of that mechanism
 190                  */
 191                 int fd;
 192                 unsigned long long offset;
 193                 fd = phys_mapping(to_phys(&__syscall_stub_start), &offset);
 194                 addr = mmap64((void *) UML_CONFIG_STUB_CODE, UM_KERN_PAGE_SIZE,
 195                               PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset);
 196                 if (addr == MAP_FAILED) {
 197                         printk(UM_KERN_ERR "mapping mmap stub failed, "
 198                                "errno = %d\n", errno);
 199                         exit(1);
 200                 }
 201
 202                 if (stack != NULL) {
 203                         fd = phys_mapping(to_phys(stack), &offset);
 204                         addr = mmap((void *) UML_CONFIG_STUB_DATA,
 205                                     UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
 206                                     MAP_FIXED | MAP_SHARED, fd, offset);
 207                         if (addr == MAP_FAILED) {
 208                                 printk(UM_KERN_ERR "mapping segfault stack "
 209                                        "failed, errno = %d\n", errno);
 210                                 exit(1);
 211                         }
 212                 }
 213         }
 214         if (!ptrace_faultinfo && (stack != NULL)) {
 215                 struct sigaction sa;
 216
 217                 unsigned long v = UML_CONFIG_STUB_CODE +
 218                                   (unsigned long) stub_segv_handler -
 219                                   (unsigned long) &__syscall_stub_start;
 220
 221                 set_sigstack((void *) UML_CONFIG_STUB_DATA, UM_KERN_PAGE_SIZE);
 222                 sigemptyset(&sa.sa_mask);
 223                 sigaddset(&sa.sa_mask, SIGIO);
 224                 sigaddset(&sa.sa_mask, SIGWINCH);
 225                 sigaddset(&sa.sa_mask, SIGVTALRM);
 226                 sigaddset(&sa.sa_mask, SIGUSR1);
 227                 sa.sa_flags = SA_ONSTACK;
 228                 sa.sa_handler = (void *) v;
 229                 sa.sa_restorer = NULL;
 230                 if (sigaction(SIGSEGV, &sa, NULL) < 0)
 231                         panic("userspace_tramp - setting SIGSEGV handler "
 232                               "failed - errno = %d\n", errno);
 233         }
 234
 235         kill(os_getpid(), SIGSTOP);
 236         return 0;
 237 }
 238
 239 /* Each element set once, and only accessed by a single processor anyway */
 240 #undef NR_CPUS
 241 #define NR_CPUS 1
 242 int userspace_pid[NR_CPUS];
 243
 244 int start_userspace(unsigned long stub_stack)
 245 {
 246         void *stack;
 247         unsigned long sp;
 248         int pid, status, n, flags;
 249
 250         stack = mmap(NULL, UM_KERN_PAGE_SIZE,
 251                      PROT_READ | PROT_WRITE | PROT_EXEC,
 252                      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 253         if (stack == MAP_FAILED)
 254                 panic("start_userspace : mmap failed, errno = %d", errno);
 255         sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
 256
 257         flags = CLONE_FILES | SIGCHLD;
 258         if (proc_mm)
 259                 flags |= CLONE_VM;
 260
 261         pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
 262         if (pid < 0)
 263                 panic("start_userspace : clone failed, errno = %d", errno);
 264
 265         do {
 266                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 267                 if (n < 0)
 268                         panic("start_userspace : wait failed, errno = %d",
 269                               errno);
 270         } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGVTALRM));
 271
 272         if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
 273                 panic("start_userspace : expected SIGSTOP, got status = %d",
 274                       status);
 275
 276         if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
 277                    (void *) PTRACE_O_TRACESYSGOOD) < 0)
 278                 panic("start_userspace : PTRACE_OLDSETOPTIONS failed, "
 279                       "errno = %d\n", errno);
 280
 281         if (munmap(stack, UM_KERN_PAGE_SIZE) < 0)
 282                 panic("start_userspace : munmap failed, errno = %d\n", errno);
 283
 284         return pid;
 285 }
 286
 287 void userspace(struct uml_pt_regs *regs)
 288 {
 289         struct itimerval timer;
 290         unsigned long long nsecs, now;
 291         int err, status, op, pid = userspace_pid[0];
 292         /* To prevent races if using_sysemu changes under us.*/
 293         int local_using_sysemu;
 294
 295         if (getitimer(ITIMER_VIRTUAL, &timer))
 296                 printk("Failed to get itimer, errno = %d\n", errno);
 297         nsecs = timer.it_value.tv_sec * UM_NSEC_PER_SEC +
 298                 timer.it_value.tv_usec * UM_NSEC_PER_USEC;
 299         nsecs += os_nsecs();
 300
 301         while (1) {
 302                 restore_registers(pid, regs);
 303
 304                 /* Now we set local_using_sysemu to be used for one loop */
 305                 local_using_sysemu = get_using_sysemu();
 306
 307                 op = SELECT_PTRACE_OPERATION(local_using_sysemu,
 308                                              singlestepping(NULL));
 309
 310                 err = ptrace(op, pid, 0, 0);
 311                 if (err)
 312                         panic("userspace - could not resume userspace process, "
 313                               "pid=%d, ptrace operation = %d, errno = %d\n",
 314                               pid, op, errno);
 315
 316                 CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED));
 317                 if (err < 0)
 318                         panic("userspace - waitpid failed, errno = %d\n",
 319                               errno);
 320
 321                 regs->is_user = 1;
 322                 save_registers(pid, regs);
 323                 UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */
 324
 325                 if (WIFSTOPPED(status)) {
 326                         int sig = WSTOPSIG(status);
 327                         switch(sig) {
 328                         case SIGSEGV:
 329                                 if (PTRACE_FULL_FAULTINFO ||
 330                                     !ptrace_faultinfo) {
 331                                         get_skas_faultinfo(pid,
 332                                                            &regs->faultinfo);
 333                                         (*sig_info[SIGSEGV])(SIGSEGV, regs);
 334                                 }
 335                                 else handle_segv(pid, regs);
 336                                 break;
 337                         case SIGTRAP + 0x80:
 338                                 handle_trap(pid, regs, local_using_sysemu);
 339                                 break;
 340                         case SIGTRAP:
 341                                 relay_signal(SIGTRAP, regs);
 342                                 break;
 343                         case SIGVTALRM:
 344                                 now = os_nsecs();
 345                                 if(now < nsecs)
 346                                         break;
 347                                 block_signals();
 348                                 (*sig_info[sig])(sig, regs);
 349                                 unblock_signals();
 350                                 nsecs = timer.it_value.tv_sec *
 351                                         UM_NSEC_PER_SEC +
 352                                         timer.it_value.tv_usec *
 353                                         UM_NSEC_PER_USEC;
 354                                 nsecs += os_nsecs();
 355                                 break;
 356                         case SIGIO:
 357                         case SIGILL:
 358                         case SIGBUS:
 359                         case SIGFPE:
 360                         case SIGWINCH:
 361                                 block_signals();
 362                                 (*sig_info[sig])(sig, regs);
 363                                 unblock_signals();
 364                                 break;
 365                         default:
 366                                 printk(UM_KERN_ERR "userspace - child stopped "
 367                                        "with signal %d\n", sig);
 368                         }
 369                         pid = userspace_pid[0];
 370                         interrupt_end();
 371
 372                         /* Avoid -ERESTARTSYS handling in host */
 373                         if (PT_SYSCALL_NR_OFFSET != PT_SYSCALL_RET_OFFSET)
 374                                 PT_SYSCALL_NR(regs->gp) = -1;
 375                 }
 376         }
 377 }
 378
 379 static unsigned long thread_regs[MAX_REG_NR];
 380
 381 static int __init init_thread_regs(void)
 382 {
 383         get_safe_registers(thread_regs);
 384         /* Set parent's instruction pointer to start of clone-stub */
 385         thread_regs[REGS_IP_INDEX] = UML_CONFIG_STUB_CODE +
 386                                 (unsigned long) stub_clone_handler -
 387                                 (unsigned long) &__syscall_stub_start;
 388         thread_regs[REGS_SP_INDEX] = UML_CONFIG_STUB_DATA + UM_KERN_PAGE_SIZE -
 389                 sizeof(void *);
 390 #ifdef __SIGNAL_FRAMESIZE
 391         thread_regs[REGS_SP_INDEX] -= __SIGNAL_FRAMESIZE;
 392 #endif
 393         return 0;
 394 }
 395
 396 __initcall(init_thread_regs);
 397
 398 int copy_context_skas0(unsigned long new_stack, int pid)
 399 {
 400         struct timeval tv = { .tv_sec = 0, .tv_usec = UM_USEC_PER_SEC / UM_HZ };
 401         int err;
 402         unsigned long current_stack = current_stub_stack();
 403         struct stub_data *data = (struct stub_data *) current_stack;
 404         struct stub_data *child_data = (struct stub_data *) new_stack;
 405         unsigned long long new_offset;
 406         int new_fd = phys_mapping(to_phys((void *)new_stack), &new_offset);
 407
 408         /*
 409          * prepare offset and fd of child's stack as argument for parent's
 410          * and child's mmap2 calls
 411          */
 412         *data = ((struct stub_data) { .offset   = MMAP_OFFSET(new_offset),
 413                                       .fd       = new_fd,
 414                                       .timer    = ((struct itimerval)
 415                                                    { .it_value = tv,
 416                                                      .it_interval = tv }) });
 417
 418         err = ptrace_setregs(pid, thread_regs);
 419         if (err < 0)
 420                 panic("copy_context_skas0 : PTRACE_SETREGS failed, "
 421                       "pid = %d, errno = %d\n", pid, -err);
 422
 423         /* set a well known return code for detection of child write failure */
 424         child_data->err = 12345678;
 425
 426         /*
 427          * Wait, until parent has finished its work: read child's pid from
 428          * parent's stack, and check, if bad result.
 429          */
 430         err = ptrace(PTRACE_CONT, pid, 0, 0);
 431         if (err)
 432                 panic("Failed to continue new process, pid = %d, "
 433                       "errno = %d\n", pid, errno);
 434         wait_stub_done(pid);
 435
 436         pid = data->err;
 437         if (pid < 0)
 438                 panic("copy_context_skas0 - stub-parent reports error %d\n",
 439                       -pid);
 440
 441         /*
 442          * Wait, until child has finished too: read child's result from
 443          * child's stack and check it.
 444          */
 445         wait_stub_done(pid);
 446         if (child_data->err != UML_CONFIG_STUB_DATA)
 447                 panic("copy_context_skas0 - stub-child reports error %ld\n",
 448                       child_data->err);
 449
 450         if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
 451                    (void *)PTRACE_O_TRACESYSGOOD) < 0)
 452                 panic("copy_context_skas0 : PTRACE_OLDSETOPTIONS failed, "
 453                       "errno = %d\n", errno);
 454
 455         return pid;
 456 }
 457
 458 /*
 459  * This is used only, if stub pages are needed, while proc_mm is
 460  * available. Opening /proc/mm creates a new mm_context, which lacks
 461  * the stub-pages. Thus, we map them using /proc/mm-fd
 462  */
 463 void map_stub_pages(int fd, unsigned long code,
 464                     unsigned long data, unsigned long stack)
 465 {
 466         struct proc_mm_op mmop;
 467         int n;
 468         unsigned long long code_offset;
 469         int code_fd = phys_mapping(to_phys((void *) &__syscall_stub_start),
 470                                    &code_offset);
 471
 472         mmop = ((struct proc_mm_op) { .op        = MM_MMAP,
 473                                       .u         =
 474                                       { .mmap    =
 475                                         { .addr    = code,
 476                                           .len     = UM_KERN_PAGE_SIZE,
 477                                           .prot    = PROT_EXEC,
 478                                           .flags   = MAP_FIXED | MAP_PRIVATE,
 479                                           .fd      = code_fd,
 480                                           .offset  = code_offset
 481         } } });
 482         CATCH_EINTR(n = write(fd, &mmop, sizeof(mmop)));
 483         if (n != sizeof(mmop)) {
 484                 n = errno;
 485                 printk(UM_KERN_ERR "mmap args - addr = 0x%lx, fd = %d, "
 486                        "offset = %llx\n", code, code_fd,
 487                        (unsigned long long) code_offset);
 488                 panic("map_stub_pages : /proc/mm map for code failed, "
 489                       "err = %d\n", n);
 490         }
 491
 492         if (stack) {
 493                 unsigned long long map_offset;
 494                 int map_fd = phys_mapping(to_phys((void *)stack), &map_offset);
 495                 mmop = ((struct proc_mm_op)
 496                                 { .op        = MM_MMAP,
 497                                   .u         =
 498                                   { .mmap    =
 499                                     { .addr    = data,
 500                                       .len     = UM_KERN_PAGE_SIZE,
 501                                       .prot    = PROT_READ | PROT_WRITE,
 502                                       .flags   = MAP_FIXED | MAP_SHARED,
 503                                       .fd      = map_fd,
 504                                       .offset  = map_offset
 505                 } } });
 506                 CATCH_EINTR(n = write(fd, &mmop, sizeof(mmop)));
 507                 if (n != sizeof(mmop))
 508                         panic("map_stub_pages : /proc/mm map for data failed, "
 509                               "err = %d\n", errno);
 510         }
 511 }
 512
 513 void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
 514 {
 515         (*buf)[0].JB_IP = (unsigned long) handler;
 516         (*buf)[0].JB_SP = (unsigned long) stack + UM_THREAD_SIZE -
 517                 sizeof(void *);
 518 }
 519
 520 #define INIT_JMP_NEW_THREAD 0
 521 #define INIT_JMP_CALLBACK 1
 522 #define INIT_JMP_HALT 2
 523 #define INIT_JMP_REBOOT 3
 524
 525 void switch_threads(jmp_buf *me, jmp_buf *you)
 526 {
 527         if (UML_SETJMP(me) == 0)
 528                 UML_LONGJMP(you, 1);
 529 }
 530
 531 static jmp_buf initial_jmpbuf;
 532
 533 /* XXX Make these percpu */
 534 static void (*cb_proc)(void *arg);
 535 static void *cb_arg;
 536 static jmp_buf *cb_back;
 537
 538 int start_idle_thread(void *stack, jmp_buf *switch_buf)
 539 {
 540         int n;
 541
 542         set_handler(SIGWINCH, (__sighandler_t) sig_handler,
 543                     SA_ONSTACK | SA_RESTART, SIGUSR1, SIGIO, SIGVTALRM, -1);
 544
 545         /*
 546          * Can't use UML_SETJMP or UML_LONGJMP here because they save
 547          * and restore signals, with the possible side-effect of
 548          * trying to handle any signals which came when they were
 549          * blocked, which can't be done on this stack.
 550          * Signals must be blocked when jumping back here and restored
 551          * after returning to the jumper.
 552          */
 553         n = setjmp(initial_jmpbuf);
 554         switch(n) {
 555         case INIT_JMP_NEW_THREAD:
 556                 (*switch_buf)[0].JB_IP = (unsigned long) new_thread_handler;
 557                 (*switch_buf)[0].JB_SP = (unsigned long) stack +
 558                         UM_THREAD_SIZE - sizeof(void *);
 559                 break;
 560         case INIT_JMP_CALLBACK:
 561                 (*cb_proc)(cb_arg);
 562                 longjmp(*cb_back, 1);
 563                 break;
 564         case INIT_JMP_HALT:
 565                 kmalloc_ok = 0;
 566                 return 0;
 567         case INIT_JMP_REBOOT:
 568                 kmalloc_ok = 0;
 569                 return 1;
 570         default:
 571                 panic("Bad sigsetjmp return in start_idle_thread - %d\n", n);
 572         }
 573         longjmp(*switch_buf, 1);
 574 }
 575
 576 void initial_thread_cb_skas(void (*proc)(void *), void *arg)
 577 {
 578         jmp_buf here;
 579
 580         cb_proc = proc;
 581         cb_arg = arg;
 582         cb_back = &here;
 583
 584         block_signals();
 585         if (UML_SETJMP(&here) == 0)
 586                 UML_LONGJMP(&initial_jmpbuf, INIT_JMP_CALLBACK);
 587         unblock_signals();
 588
 589         cb_proc = NULL;
 590         cb_arg = NULL;
 591         cb_back = NULL;
 592 }
 593
 594 void halt_skas(void)
 595 {
 596         block_signals();
 597         UML_LONGJMP(&initial_jmpbuf, INIT_JMP_HALT);
 598 }
 599
 600 void reboot_skas(void)
 601 {
 602         block_signals();
 603         UML_LONGJMP(&initial_jmpbuf, INIT_JMP_REBOOT);
 604 }
 605
 606 void __switch_mm(struct mm_id *mm_idp)
 607 {
 608         int err;
 609
 610         /* FIXME: need cpu pid in __switch_mm */
 611         if (proc_mm) {
 612                 err = ptrace(PTRACE_SWITCH_MM, userspace_pid[0], 0,
 613                              mm_idp->u.mm_fd);
 614                 if (err)
 615                         panic("__switch_mm - PTRACE_SWITCH_MM failed, "
 616                               "errno = %d\n", errno);
 617         }
 618         else userspace_pid[0] = mm_idp->u.pid;
 619 }