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

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
   4  * Copyright (C) 2002- 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   5  */
   6
   7 #include <stdlib.h>
   8 #include <stdbool.h>
   9 #include <unistd.h>
  10 #include <sched.h>
  11 #include <errno.h>
  12 #include <string.h>
  13 #include <sys/mman.h>
  14 #include <sys/wait.h>
  15 #include <asm/unistd.h>
  16 #include <as-layout.h>
  17 #include <init.h>
  18 #include <kern_util.h>
  19 #include <mem.h>
  20 #include <os.h>
  21 #include <ptrace_user.h>
  22 #include <registers.h>
  23 #include <skas.h>
  24 #include <sysdep/stub.h>
  25 #include <linux/threads.h>
  26
  27 int is_skas_winch(int pid, int fd, void *data)
  28 {
  29         return pid == getpgrp();
  30 }
  31
  32 static const char *ptrace_reg_name(int idx)
  33 {
  34 #define R(n) case HOST_##n: return #n
  35
  36         switch (idx) {
  37 #ifdef __x86_64__
  38         R(BX);
  39         R(CX);
  40         R(DI);
  41         R(SI);
  42         R(DX);
  43         R(BP);
  44         R(AX);
  45         R(R8);
  46         R(R9);
  47         R(R10);
  48         R(R11);
  49         R(R12);
  50         R(R13);
  51         R(R14);
  52         R(R15);
  53         R(ORIG_AX);
  54         R(CS);
  55         R(SS);
  56         R(EFLAGS);
  57 #elif defined(__i386__)
  58         R(IP);
  59         R(SP);
  60         R(EFLAGS);
  61         R(AX);
  62         R(BX);
  63         R(CX);
  64         R(DX);
  65         R(SI);
  66         R(DI);
  67         R(BP);
  68         R(CS);
  69         R(SS);
  70         R(DS);
  71         R(FS);
  72         R(ES);
  73         R(GS);
  74         R(ORIG_AX);
  75 #endif
  76         }
  77         return "";
  78 }
  79
  80 static int ptrace_dump_regs(int pid)
  81 {
  82         unsigned long regs[MAX_REG_NR];
  83         int i;
  84
  85         if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
  86                 return -errno;
  87
  88         printk(UM_KERN_ERR "Stub registers -\n");
  89         for (i = 0; i < ARRAY_SIZE(regs); i++) {
  90                 const char *regname = ptrace_reg_name(i);
  91
  92                 printk(UM_KERN_ERR "\t%s\t(%2d): %lx\n", regname, i, regs[i]);
  93         }
  94
  95         return 0;
  96 }
  97
  98 /*
  99  * Signals that are OK to receive in the stub - we'll just continue it.
 100  * SIGWINCH will happen when UML is inside a detached screen.
 101  */
 102 #define STUB_SIG_MASK ((1 << SIGALRM) | (1 << SIGWINCH))
 103
 104 /* Signals that the stub will finish with - anything else is an error */
 105 #define STUB_DONE_MASK (1 << SIGTRAP)
 106
 107 void wait_stub_done(int pid)
 108 {
 109         int n, status, err;
 110
 111         while (1) {
 112                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
 113                 if ((n < 0) || !WIFSTOPPED(status))
 114                         goto bad_wait;
 115
 116                 if (((1 << WSTOPSIG(status)) & STUB_SIG_MASK) == 0)
 117                         break;
 118
 119                 err = ptrace(PTRACE_CONT, pid, 0, 0);
 120                 if (err) {
 121                         printk(UM_KERN_ERR "wait_stub_done : continue failed, "
 122                                "errno = %d\n", errno);
 123                         fatal_sigsegv();
 124                 }
 125         }
 126
 127         if (((1 << WSTOPSIG(status)) & STUB_DONE_MASK) != 0)
 128                 return;
 129
 130 bad_wait:
 131         err = ptrace_dump_regs(pid);
 132         if (err)
 133                 printk(UM_KERN_ERR "Failed to get registers from stub, "
 134                        "errno = %d\n", -err);
 135         printk(UM_KERN_ERR "wait_stub_done : failed to wait for SIGTRAP, "
 136                "pid = %d, n = %d, errno = %d, status = 0x%x\n", pid, n, errno,
 137                status);
 138         fatal_sigsegv();
 139 }
 140
 141 extern unsigned long current_stub_stack(void);
 142
 143 static void get_skas_faultinfo(int pid, struct faultinfo *fi, unsigned long *aux_fp_regs)
 144 {
 145         int err;
 146
 147         err = get_fp_registers(pid, aux_fp_regs);
 148         if (err < 0) {
 149                 printk(UM_KERN_ERR "save_fp_registers returned %d\n",
 150                        err);
 151                 fatal_sigsegv();
 152         }
 153         err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);
 154         if (err) {
 155                 printk(UM_KERN_ERR "Failed to continue stub, pid = %d, "
 156                        "errno = %d\n", pid, errno);
 157                 fatal_sigsegv();
 158         }
 159         wait_stub_done(pid);
 160
 161         /*
 162          * faultinfo is prepared by the stub_segv_handler at start of
 163          * the stub stack page. We just have to copy it.
 164          */
 165         memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));
 166
 167         err = put_fp_registers(pid, aux_fp_regs);
 168         if (err < 0) {
 169                 printk(UM_KERN_ERR "put_fp_registers returned %d\n",
 170                        err);
 171                 fatal_sigsegv();
 172         }
 173 }
 174
 175 static void handle_segv(int pid, struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
 176 {
 177         get_skas_faultinfo(pid, &regs->faultinfo, aux_fp_regs);
 178         segv(regs->faultinfo, 0, 1, NULL);
 179 }
 180
 181 /*
 182  * To use the same value of using_sysemu as the caller, ask it that value
 183  * (in local_using_sysemu
 184  */
 185 static void handle_trap(int pid, struct uml_pt_regs *regs,
 186                         int local_using_sysemu)
 187 {
 188         int err, status;
 189
 190         if ((UPT_IP(regs) >= STUB_START) && (UPT_IP(regs) < STUB_END))
 191                 fatal_sigsegv();
 192
 193         if (!local_using_sysemu)
 194         {
 195                 err = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_NR_OFFSET,
 196                              __NR_getpid);
 197                 if (err < 0) {
 198                         printk(UM_KERN_ERR "handle_trap - nullifying syscall "
 199                                "failed, errno = %d\n", errno);
 200                         fatal_sigsegv();
 201                 }
 202
 203                 err = ptrace(PTRACE_SYSCALL, pid, 0, 0);
 204                 if (err < 0) {
 205                         printk(UM_KERN_ERR "handle_trap - continuing to end of "
 206                                "syscall failed, errno = %d\n", errno);
 207                         fatal_sigsegv();
 208                 }
 209
 210                 CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
 211                 if ((err < 0) || !WIFSTOPPED(status) ||
 212                     (WSTOPSIG(status) != SIGTRAP + 0x80)) {
 213                         err = ptrace_dump_regs(pid);
 214                         if (err)
 215                                 printk(UM_KERN_ERR "Failed to get registers "
 216                                        "from process, errno = %d\n", -err);
 217                         printk(UM_KERN_ERR "handle_trap - failed to wait at "
 218                                "end of syscall, errno = %d, status = %d\n",
 219                                errno, status);
 220                         fatal_sigsegv();
 221                 }
 222         }
 223
 224         handle_syscall(regs);
 225 }
 226
 227 extern char __syscall_stub_start[];
 228
 229 /**
 230  * userspace_tramp() - userspace trampoline
 231  * @stack:      pointer to the new userspace stack page, can be NULL, if? FIXME:
 232  *
 233  * The userspace trampoline is used to setup a new userspace process in start_userspace() after it was clone()'ed.
 234  * This function will run on a temporary stack page.
 235  * It ptrace()'es itself, then
 236  * Two pages are mapped into the userspace address space:
 237  * - STUB_CODE (with EXEC), which contains the skas stub code
 238  * - STUB_DATA (with R/W), which contains a data page that is used to transfer certain data between the UML userspace process and the UML kernel.
 239  * Also for the userspace process a SIGSEGV handler is installed to catch pagefaults in the userspace process.
 240  * And last the process stops itself to give control to the UML kernel for this userspace process.
 241  *
 242  * Return: Always zero, otherwise the current userspace process is ended with non null exit() call
 243  */
 244 static int userspace_tramp(void *stack)
 245 {
 246         void *addr;
 247         int fd;
 248         unsigned long long offset;
 249
 250         ptrace(PTRACE_TRACEME, 0, 0, 0);
 251
 252         signal(SIGTERM, SIG_DFL);
 253         signal(SIGWINCH, SIG_IGN);
 254
 255         fd = phys_mapping(uml_to_phys(__syscall_stub_start), &offset);
 256         addr = mmap64((void *) STUB_CODE, UM_KERN_PAGE_SIZE,
 257                       PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset);
 258         if (addr == MAP_FAILED) {
 259                 printk(UM_KERN_ERR "mapping mmap stub at 0x%lx failed, "
 260                        "errno = %d\n", STUB_CODE, errno);
 261                 exit(1);
 262         }
 263
 264         if (stack != NULL) {
 265                 fd = phys_mapping(uml_to_phys(stack), &offset);
 266                 addr = mmap((void *) STUB_DATA,
 267                             UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
 268                             MAP_FIXED | MAP_SHARED, fd, offset);
 269                 if (addr == MAP_FAILED) {
 270                         printk(UM_KERN_ERR "mapping segfault stack "
 271                                "at 0x%lx failed, errno = %d\n",
 272                                STUB_DATA, errno);
 273                         exit(1);
 274                 }
 275         }
 276         if (stack != NULL) {
 277                 struct sigaction sa;
 278
 279                 unsigned long v = STUB_CODE +
 280                                   (unsigned long) stub_segv_handler -
 281                                   (unsigned long) __syscall_stub_start;
 282
 283                 set_sigstack((void *) STUB_DATA, UM_KERN_PAGE_SIZE);
 284                 sigemptyset(&sa.sa_mask);
 285                 sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO;
 286                 sa.sa_sigaction = (void *) v;
 287                 sa.sa_restorer = NULL;
 288                 if (sigaction(SIGSEGV, &sa, NULL) < 0) {
 289                         printk(UM_KERN_ERR "userspace_tramp - setting SIGSEGV "
 290                                "handler failed - errno = %d\n", errno);
 291                         exit(1);
 292                 }
 293         }
 294
 295         kill(os_getpid(), SIGSTOP);
 296         return 0;
 297 }
 298
 299 int userspace_pid[NR_CPUS];
 300 int kill_userspace_mm[NR_CPUS];
 301
 302 /**
 303  * start_userspace() - prepare a new userspace process
 304  * @stub_stack: pointer to the stub stack. Can be NULL, if? FIXME:
 305  *
 306  * Setups a new temporary stack page that is used while userspace_tramp() runs
 307  * Clones the kernel process into a new userspace process, with FDs only.
 308  *
 309  * Return: When positive: the process id of the new userspace process,
 310  *         when negative: an error number.
 311  * FIXME: can PIDs become negative?!
 312  */
 313 int start_userspace(unsigned long stub_stack)
 314 {
 315         void *stack;
 316         unsigned long sp;
 317         int pid, status, n, flags, err;
 318
 319         /* setup a temporary stack page */
 320         stack = mmap(NULL, UM_KERN_PAGE_SIZE,
 321                      PROT_READ | PROT_WRITE | PROT_EXEC,
 322                      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 323         if (stack == MAP_FAILED) {
 324                 err = -errno;
 325                 printk(UM_KERN_ERR "start_userspace : mmap failed, "
 326                        "errno = %d\n", errno);
 327                 return err;
 328         }
 329
 330         /* set stack pointer to the end of the stack page, so it can grow downwards */
 331         sp = (unsigned long)stack + UM_KERN_PAGE_SIZE;
 332
 333         flags = CLONE_FILES | SIGCHLD;
 334
 335         /* clone into new userspace process */
 336         pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
 337         if (pid < 0) {
 338                 err = -errno;
 339                 printk(UM_KERN_ERR "start_userspace : clone failed, "
 340                        "errno = %d\n", errno);
 341                 return err;
 342         }
 343
 344         do {
 345                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
 346                 if (n < 0) {
 347                         err = -errno;
 348                         printk(UM_KERN_ERR "start_userspace : wait failed, "
 349                                "errno = %d\n", errno);
 350                         goto out_kill;
 351                 }
 352         } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM));
 353
 354         if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
 355                 err = -EINVAL;
 356                 printk(UM_KERN_ERR "start_userspace : expected SIGSTOP, got "
 357                        "status = %d\n", status);
 358                 goto out_kill;
 359         }
 360
 361         if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
 362                    (void *) PTRACE_O_TRACESYSGOOD) < 0) {
 363                 err = -errno;
 364                 printk(UM_KERN_ERR "start_userspace : PTRACE_OLDSETOPTIONS "
 365                        "failed, errno = %d\n", errno);
 366                 goto out_kill;
 367         }
 368
 369         if (munmap(stack, UM_KERN_PAGE_SIZE) < 0) {
 370                 err = -errno;
 371                 printk(UM_KERN_ERR "start_userspace : munmap failed, "
 372                        "errno = %d\n", errno);
 373                 goto out_kill;
 374         }
 375
 376         return pid;
 377
 378  out_kill:
 379         os_kill_ptraced_process(pid, 1);
 380         return err;
 381 }
 382
 383 void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
 384 {
 385         int err, status, op, pid = userspace_pid[0];
 386         /* To prevent races if using_sysemu changes under us.*/
 387         int local_using_sysemu;
 388         siginfo_t si;
 389
 390         /* Handle any immediate reschedules or signals */
 391         interrupt_end();
 392
 393         while (1) {
 394                 if (kill_userspace_mm[0])
 395                         fatal_sigsegv();
 396
 397                 /*
 398                  * This can legitimately fail if the process loads a
 399                  * bogus value into a segment register.  It will
 400                  * segfault and PTRACE_GETREGS will read that value
 401                  * out of the process.  However, PTRACE_SETREGS will
 402                  * fail.  In this case, there is nothing to do but
 403                  * just kill the process.
 404                  */
 405                 if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp)) {
 406                         printk(UM_KERN_ERR "userspace - ptrace set regs "
 407                                "failed, errno = %d\n", errno);
 408                         fatal_sigsegv();
 409                 }
 410
 411                 if (put_fp_registers(pid, regs->fp)) {
 412                         printk(UM_KERN_ERR "userspace - ptrace set fp regs "
 413                                "failed, errno = %d\n", errno);
 414                         fatal_sigsegv();
 415                 }
 416
 417                 /* Now we set local_using_sysemu to be used for one loop */
 418                 local_using_sysemu = get_using_sysemu();
 419
 420                 op = SELECT_PTRACE_OPERATION(local_using_sysemu,
 421                                              singlestepping(NULL));
 422
 423                 if (ptrace(op, pid, 0, 0)) {
 424                         printk(UM_KERN_ERR "userspace - ptrace continue "
 425                                "failed, op = %d, errno = %d\n", op, errno);
 426                         fatal_sigsegv();
 427                 }
 428
 429                 CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
 430                 if (err < 0) {
 431                         printk(UM_KERN_ERR "userspace - wait failed, "
 432                                "errno = %d\n", errno);
 433                         fatal_sigsegv();
 434                 }
 435
 436                 regs->is_user = 1;
 437                 if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp)) {
 438                         printk(UM_KERN_ERR "userspace - PTRACE_GETREGS failed, "
 439                                "errno = %d\n", errno);
 440                         fatal_sigsegv();
 441                 }
 442
 443                 if (get_fp_registers(pid, regs->fp)) {
 444                         printk(UM_KERN_ERR "userspace -  get_fp_registers failed, "
 445                                "errno = %d\n", errno);
 446                         fatal_sigsegv();
 447                 }
 448
 449                 UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */
 450
 451                 if (WIFSTOPPED(status)) {
 452                         int sig = WSTOPSIG(status);
 453
 454                         /* These signal handlers need the si argument.
 455                          * The SIGIO and SIGALARM handlers which constitute the
 456                          * majority of invocations, do not use it.
 457                          */
 458                         switch (sig) {
 459                         case SIGSEGV:
 460                         case SIGTRAP:
 461                         case SIGILL:
 462                         case SIGBUS:
 463                         case SIGFPE:
 464                         case SIGWINCH:
 465                                 ptrace(PTRACE_GETSIGINFO, pid, 0, (struct siginfo *)&si);
 466                                 break;
 467                         }
 468
 469                         switch (sig) {
 470                         case SIGSEGV:
 471                                 if (PTRACE_FULL_FAULTINFO) {
 472                                         get_skas_faultinfo(pid,
 473                                                            &regs->faultinfo, aux_fp_regs);
 474                                         (*sig_info[SIGSEGV])(SIGSEGV, (struct siginfo *)&si,
 475                                                              regs);
 476                                 }
 477                                 else handle_segv(pid, regs, aux_fp_regs);
 478                                 break;
 479                         case SIGTRAP + 0x80:
 480                                 handle_trap(pid, regs, local_using_sysemu);
 481                                 break;
 482                         case SIGTRAP:
 483                                 relay_signal(SIGTRAP, (struct siginfo *)&si, regs);
 484                                 break;
 485                         case SIGALRM:
 486                                 break;
 487                         case SIGIO:
 488                         case SIGILL:
 489                         case SIGBUS:
 490                         case SIGFPE:
 491                         case SIGWINCH:
 492                                 block_signals_trace();
 493                                 (*sig_info[sig])(sig, (struct siginfo *)&si, regs);
 494                                 unblock_signals_trace();
 495                                 break;
 496                         default:
 497                                 printk(UM_KERN_ERR "userspace - child stopped "
 498                                        "with signal %d\n", sig);
 499                                 fatal_sigsegv();
 500                         }
 501                         pid = userspace_pid[0];
 502                         interrupt_end();
 503
 504                         /* Avoid -ERESTARTSYS handling in host */
 505                         if (PT_SYSCALL_NR_OFFSET != PT_SYSCALL_RET_OFFSET)
 506                                 PT_SYSCALL_NR(regs->gp) = -1;
 507                 }
 508         }
 509 }
 510
 511 static unsigned long thread_regs[MAX_REG_NR];
 512 static unsigned long thread_fp_regs[FP_SIZE];
 513
 514 static int __init init_thread_regs(void)
 515 {
 516         get_safe_registers(thread_regs, thread_fp_regs);
 517         /* Set parent's instruction pointer to start of clone-stub */
 518         thread_regs[REGS_IP_INDEX] = STUB_CODE +
 519                                 (unsigned long) stub_clone_handler -
 520                                 (unsigned long) __syscall_stub_start;
 521         thread_regs[REGS_SP_INDEX] = STUB_DATA + UM_KERN_PAGE_SIZE -
 522                 sizeof(void *);
 523 #ifdef __SIGNAL_FRAMESIZE
 524         thread_regs[REGS_SP_INDEX] -= __SIGNAL_FRAMESIZE;
 525 #endif
 526         return 0;
 527 }
 528
 529 __initcall(init_thread_regs);
 530
 531 int copy_context_skas0(unsigned long new_stack, int pid)
 532 {
 533         int err;
 534         unsigned long current_stack = current_stub_stack();
 535         struct stub_data *data = (struct stub_data *) current_stack;
 536         struct stub_data *child_data = (struct stub_data *) new_stack;
 537         unsigned long long new_offset;
 538         int new_fd = phys_mapping(uml_to_phys((void *)new_stack), &new_offset);
 539
 540         /*
 541          * prepare offset and fd of child's stack as argument for parent's
 542          * and child's mmap2 calls
 543          */
 544         *data = ((struct stub_data) {
 545                 .offset = MMAP_OFFSET(new_offset),
 546                 .fd     = new_fd,
 547                 .parent_err = -ESRCH,
 548                 .child_err = 0,
 549         });
 550
 551         *child_data = ((struct stub_data) {
 552                 .child_err = -ESRCH,
 553         });
 554
 555         err = ptrace_setregs(pid, thread_regs);
 556         if (err < 0) {
 557                 err = -errno;
 558                 printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_SETREGS "
 559                        "failed, pid = %d, errno = %d\n", pid, -err);
 560                 return err;
 561         }
 562
 563         err = put_fp_registers(pid, thread_fp_regs);
 564         if (err < 0) {
 565                 printk(UM_KERN_ERR "copy_context_skas0 : put_fp_registers "
 566                        "failed, pid = %d, err = %d\n", pid, err);
 567                 return err;
 568         }
 569
 570         /*
 571          * Wait, until parent has finished its work: read child's pid from
 572          * parent's stack, and check, if bad result.
 573          */
 574         err = ptrace(PTRACE_CONT, pid, 0, 0);
 575         if (err) {
 576                 err = -errno;
 577                 printk(UM_KERN_ERR "Failed to continue new process, pid = %d, "
 578                        "errno = %d\n", pid, errno);
 579                 return err;
 580         }
 581
 582         wait_stub_done(pid);
 583
 584         pid = data->parent_err;
 585         if (pid < 0) {
 586                 printk(UM_KERN_ERR "copy_context_skas0 - stub-parent reports "
 587                        "error %d\n", -pid);
 588                 return pid;
 589         }
 590
 591         /*
 592          * Wait, until child has finished too: read child's result from
 593          * child's stack and check it.
 594          */
 595         wait_stub_done(pid);
 596         if (child_data->child_err != STUB_DATA) {
 597                 printk(UM_KERN_ERR "copy_context_skas0 - stub-child %d reports "
 598                        "error %ld\n", pid, data->child_err);
 599                 err = data->child_err;
 600                 goto out_kill;
 601         }
 602
 603         if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
 604                    (void *)PTRACE_O_TRACESYSGOOD) < 0) {
 605                 err = -errno;
 606                 printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_OLDSETOPTIONS "
 607                        "failed, errno = %d\n", errno);
 608                 goto out_kill;
 609         }
 610
 611         return pid;
 612
 613  out_kill:
 614         os_kill_ptraced_process(pid, 1);
 615         return err;
 616 }
 617
 618 void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
 619 {
 620         (*buf)[0].JB_IP = (unsigned long) handler;
 621         (*buf)[0].JB_SP = (unsigned long) stack + UM_THREAD_SIZE -
 622                 sizeof(void *);
 623 }
 624
 625 #define INIT_JMP_NEW_THREAD 0
 626 #define INIT_JMP_CALLBACK 1
 627 #define INIT_JMP_HALT 2
 628 #define INIT_JMP_REBOOT 3
 629
 630 void switch_threads(jmp_buf *me, jmp_buf *you)
 631 {
 632         if (UML_SETJMP(me) == 0)
 633                 UML_LONGJMP(you, 1);
 634 }
 635
 636 static jmp_buf initial_jmpbuf;
 637
 638 /* XXX Make these percpu */
 639 static void (*cb_proc)(void *arg);
 640 static void *cb_arg;
 641 static jmp_buf *cb_back;
 642
 643 int start_idle_thread(void *stack, jmp_buf *switch_buf)
 644 {
 645         int n;
 646
 647         set_handler(SIGWINCH);
 648
 649         /*
 650          * Can't use UML_SETJMP or UML_LONGJMP here because they save
 651          * and restore signals, with the possible side-effect of
 652          * trying to handle any signals which came when they were
 653          * blocked, which can't be done on this stack.
 654          * Signals must be blocked when jumping back here and restored
 655          * after returning to the jumper.
 656          */
 657         n = setjmp(initial_jmpbuf);
 658         switch (n) {
 659         case INIT_JMP_NEW_THREAD:
 660                 (*switch_buf)[0].JB_IP = (unsigned long) uml_finishsetup;
 661                 (*switch_buf)[0].JB_SP = (unsigned long) stack +
 662                         UM_THREAD_SIZE - sizeof(void *);
 663                 break;
 664         case INIT_JMP_CALLBACK:
 665                 (*cb_proc)(cb_arg);
 666                 longjmp(*cb_back, 1);
 667                 break;
 668         case INIT_JMP_HALT:
 669                 kmalloc_ok = 0;
 670                 return 0;
 671         case INIT_JMP_REBOOT:
 672                 kmalloc_ok = 0;
 673                 return 1;
 674         default:
 675                 printk(UM_KERN_ERR "Bad sigsetjmp return in "
 676                        "start_idle_thread - %d\n", n);
 677                 fatal_sigsegv();
 678         }
 679         longjmp(*switch_buf, 1);
 680
 681         /* unreachable */
 682         printk(UM_KERN_ERR "impossible long jump!");
 683         fatal_sigsegv();
 684         return 0;
 685 }
 686
 687 void initial_thread_cb_skas(void (*proc)(void *), void *arg)
 688 {
 689         jmp_buf here;
 690
 691         cb_proc = proc;
 692         cb_arg = arg;
 693         cb_back = &here;
 694
 695         block_signals_trace();
 696         if (UML_SETJMP(&here) == 0)
 697                 UML_LONGJMP(&initial_jmpbuf, INIT_JMP_CALLBACK);
 698         unblock_signals_trace();
 699
 700         cb_proc = NULL;
 701         cb_arg = NULL;
 702         cb_back = NULL;
 703 }
 704
 705 void halt_skas(void)
 706 {
 707         block_signals_trace();
 708         UML_LONGJMP(&initial_jmpbuf, INIT_JMP_HALT);
 709 }
 710
 711 static bool noreboot;
 712
 713 static int __init noreboot_cmd_param(char *str, int *add)
 714 {
 715         noreboot = true;
 716         return 0;
 717 }
 718
 719 __uml_setup("noreboot", noreboot_cmd_param,
 720 "noreboot\n"
 721 "    Rather than rebooting, exit always, akin to QEMU's -no-reboot option.\n"
 722 "    This is useful if you're using CONFIG_PANIC_TIMEOUT in order to catch\n"
 723 "    crashes in CI\n");
 724
 725 void reboot_skas(void)
 726 {
 727         block_signals_trace();
 728         UML_LONGJMP(&initial_jmpbuf, noreboot ? INIT_JMP_HALT : INIT_JMP_REBOOT);
 729 }
 730
 731 void __switch_mm(struct mm_id *mm_idp)
 732 {
 733         userspace_pid[0] = mm_idp->u.pid;
 734         kill_userspace_mm[0] = mm_idp->kill;
 735 }