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

   1 /*
   2  * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
   3  * Copyright (C) 2002- 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   4  * Licensed under the GPL
   5  */
   6
   7 #include <stdlib.h>
   8 #include <unistd.h>
   9 #include <sched.h>
  10 #include <errno.h>
  11 #include <string.h>
  12 #include <sys/mman.h>
  13 #include <sys/wait.h>
  14 #include <asm/unistd.h>
  15 #include <as-layout.h>
  16 #include <init.h>
  17 #include <kern_util.h>
  18 #include <mem.h>
  19 #include <os.h>
  20 #include <ptrace_user.h>
  21 #include <registers.h>
  22 #include <skas.h>
  23 #include <sysdep/stub.h>
  24
  25 int is_skas_winch(int pid, int fd, void *data)
  26 {
  27         return pid == getpgrp();
  28 }
  29
  30 static int ptrace_dump_regs(int pid)
  31 {
  32         unsigned long regs[MAX_REG_NR];
  33         int i;
  34
  35         if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
  36                 return -errno;
  37
  38         printk(UM_KERN_ERR "Stub registers -\n");
  39         for (i = 0; i < ARRAY_SIZE(regs); i++)
  40                 printk(UM_KERN_ERR "\t%d - %lx\n", i, regs[i]);
  41
  42         return 0;
  43 }
  44
  45 /*
  46  * Signals that are OK to receive in the stub - we'll just continue it.
  47  * SIGWINCH will happen when UML is inside a detached screen.
  48  */
  49 #define STUB_SIG_MASK ((1 << SIGALRM) | (1 << SIGWINCH))
  50
  51 /* Signals that the stub will finish with - anything else is an error */
  52 #define STUB_DONE_MASK (1 << SIGTRAP)
  53
  54 void wait_stub_done(int pid)
  55 {
  56         int n, status, err;
  57
  58         while (1) {
  59                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
  60                 if ((n < 0) || !WIFSTOPPED(status))
  61                         goto bad_wait;
  62
  63                 if (((1 << WSTOPSIG(status)) & STUB_SIG_MASK) == 0)
  64                         break;
  65
  66                 err = ptrace(PTRACE_CONT, pid, 0, 0);
  67                 if (err) {
  68                         printk(UM_KERN_ERR "wait_stub_done : continue failed, "
  69                                "errno = %d\n", errno);
  70                         fatal_sigsegv();
  71                 }
  72         }
  73
  74         if (((1 << WSTOPSIG(status)) & STUB_DONE_MASK) != 0)
  75                 return;
  76
  77 bad_wait:
  78         err = ptrace_dump_regs(pid);
  79         if (err)
  80                 printk(UM_KERN_ERR "Failed to get registers from stub, "
  81                        "errno = %d\n", -err);
  82         printk(UM_KERN_ERR "wait_stub_done : failed to wait for SIGTRAP, "
  83                "pid = %d, n = %d, errno = %d, status = 0x%x\n", pid, n, errno,
  84                status);
  85         fatal_sigsegv();
  86 }
  87
  88 extern unsigned long current_stub_stack(void);
  89
  90 static void get_skas_faultinfo(int pid, struct faultinfo *fi)
  91 {
  92         int err;
  93         unsigned long fpregs[FP_SIZE];
  94
  95         err = get_fp_registers(pid, fpregs);
  96         if (err < 0) {
  97                 printk(UM_KERN_ERR "save_fp_registers returned %d\n",
  98                        err);
  99                 fatal_sigsegv();
 100         }
 101         err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);
 102         if (err) {
 103                 printk(UM_KERN_ERR "Failed to continue stub, pid = %d, "
 104                        "errno = %d\n", pid, errno);
 105                 fatal_sigsegv();
 106         }
 107         wait_stub_done(pid);
 108
 109         /*
 110          * faultinfo is prepared by the stub-segv-handler at start of
 111          * the stub stack page. We just have to copy it.
 112          */
 113         memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));
 114
 115         err = put_fp_registers(pid, fpregs);
 116         if (err < 0) {
 117                 printk(UM_KERN_ERR "put_fp_registers returned %d\n",
 118                        err);
 119                 fatal_sigsegv();
 120         }
 121 }
 122
 123 static void handle_segv(int pid, struct uml_pt_regs * regs)
 124 {
 125         get_skas_faultinfo(pid, &regs->faultinfo);
 126         segv(regs->faultinfo, 0, 1, NULL);
 127 }
 128
 129 /*
 130  * To use the same value of using_sysemu as the caller, ask it that value
 131  * (in local_using_sysemu
 132  */
 133 static void handle_trap(int pid, struct uml_pt_regs *regs,
 134                         int local_using_sysemu)
 135 {
 136         int err, status;
 137
 138         if ((UPT_IP(regs) >= STUB_START) && (UPT_IP(regs) < STUB_END))
 139                 fatal_sigsegv();
 140
 141         if (!local_using_sysemu)
 142         {
 143                 err = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_NR_OFFSET,
 144                              __NR_getpid);
 145                 if (err < 0) {
 146                         printk(UM_KERN_ERR "handle_trap - nullifying syscall "
 147                                "failed, errno = %d\n", errno);
 148                         fatal_sigsegv();
 149                 }
 150
 151                 err = ptrace(PTRACE_SYSCALL, pid, 0, 0);
 152                 if (err < 0) {
 153                         printk(UM_KERN_ERR "handle_trap - continuing to end of "
 154                                "syscall failed, errno = %d\n", errno);
 155                         fatal_sigsegv();
 156                 }
 157
 158                 CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
 159                 if ((err < 0) || !WIFSTOPPED(status) ||
 160                     (WSTOPSIG(status) != SIGTRAP + 0x80)) {
 161                         err = ptrace_dump_regs(pid);
 162                         if (err)
 163                                 printk(UM_KERN_ERR "Failed to get registers "
 164                                        "from process, errno = %d\n", -err);
 165                         printk(UM_KERN_ERR "handle_trap - failed to wait at "
 166                                "end of syscall, errno = %d, status = %d\n",
 167                                errno, status);
 168                         fatal_sigsegv();
 169                 }
 170         }
 171
 172         handle_syscall(regs);
 173 }
 174
 175 extern char __syscall_stub_start[];
 176
 177 static int userspace_tramp(void *stack)
 178 {
 179         void *addr;
 180         int fd;
 181         unsigned long long offset;
 182
 183         ptrace(PTRACE_TRACEME, 0, 0, 0);
 184
 185         signal(SIGTERM, SIG_DFL);
 186         signal(SIGWINCH, SIG_IGN);
 187
 188         /*
 189          * This has a pte, but it can't be mapped in with the usual
 190          * tlb_flush mechanism because this is part of that mechanism
 191          */
 192         fd = phys_mapping(to_phys(__syscall_stub_start), &offset);
 193         addr = mmap64((void *) STUB_CODE, UM_KERN_PAGE_SIZE,
 194                       PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset);
 195         if (addr == MAP_FAILED) {
 196                 printk(UM_KERN_ERR "mapping mmap stub at 0x%lx failed, "
 197                        "errno = %d\n", STUB_CODE, errno);
 198                 exit(1);
 199         }
 200
 201         if (stack != NULL) {
 202                 fd = phys_mapping(to_phys(stack), &offset);
 203                 addr = mmap((void *) STUB_DATA,
 204                             UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
 205                             MAP_FIXED | MAP_SHARED, fd, offset);
 206                 if (addr == MAP_FAILED) {
 207                         printk(UM_KERN_ERR "mapping segfault stack "
 208                                "at 0x%lx failed, errno = %d\n",
 209                                STUB_DATA, errno);
 210                         exit(1);
 211                 }
 212         }
 213         if (stack != NULL) {
 214                 struct sigaction sa;
 215
 216                 unsigned long v = STUB_CODE +
 217                                   (unsigned long) stub_segv_handler -
 218                                   (unsigned long) __syscall_stub_start;
 219
 220                 set_sigstack((void *) STUB_DATA, UM_KERN_PAGE_SIZE);
 221                 sigemptyset(&sa.sa_mask);
 222                 sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO;
 223                 sa.sa_sigaction = (void *) v;
 224                 sa.sa_restorer = NULL;
 225                 if (sigaction(SIGSEGV, &sa, NULL) < 0) {
 226                         printk(UM_KERN_ERR "userspace_tramp - setting SIGSEGV "
 227                                "handler failed - errno = %d\n", errno);
 228                         exit(1);
 229                 }
 230         }
 231
 232         kill(os_getpid(), SIGSTOP);
 233         return 0;
 234 }
 235
 236 /* Each element set once, and only accessed by a single processor anyway */
 237 #undef NR_CPUS
 238 #define NR_CPUS 1
 239 int userspace_pid[NR_CPUS];
 240
 241 int start_userspace(unsigned long stub_stack)
 242 {
 243         void *stack;
 244         unsigned long sp;
 245         int pid, status, n, flags, err;
 246
 247         stack = mmap(NULL, UM_KERN_PAGE_SIZE,
 248                      PROT_READ | PROT_WRITE | PROT_EXEC,
 249                      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 250         if (stack == MAP_FAILED) {
 251                 err = -errno;
 252                 printk(UM_KERN_ERR "start_userspace : mmap failed, "
 253                        "errno = %d\n", errno);
 254                 return err;
 255         }
 256
 257         sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
 258
 259         flags = CLONE_FILES | SIGCHLD;
 260
 261         pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
 262         if (pid < 0) {
 263                 err = -errno;
 264                 printk(UM_KERN_ERR "start_userspace : clone failed, "
 265                        "errno = %d\n", errno);
 266                 return err;
 267         }
 268
 269         do {
 270                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
 271                 if (n < 0) {
 272                         err = -errno;
 273                         printk(UM_KERN_ERR "start_userspace : wait failed, "
 274                                "errno = %d\n", errno);
 275                         goto out_kill;
 276                 }
 277         } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM));
 278
 279         if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
 280                 err = -EINVAL;
 281                 printk(UM_KERN_ERR "start_userspace : expected SIGSTOP, got "
 282                        "status = %d\n", status);
 283                 goto out_kill;
 284         }
 285
 286         if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
 287                    (void *) PTRACE_O_TRACESYSGOOD) < 0) {
 288                 err = -errno;
 289                 printk(UM_KERN_ERR "start_userspace : PTRACE_OLDSETOPTIONS "
 290                        "failed, errno = %d\n", errno);
 291                 goto out_kill;
 292         }
 293
 294         if (munmap(stack, UM_KERN_PAGE_SIZE) < 0) {
 295                 err = -errno;
 296                 printk(UM_KERN_ERR "start_userspace : munmap failed, "
 297                        "errno = %d\n", errno);
 298                 goto out_kill;
 299         }
 300
 301         return pid;
 302
 303  out_kill:
 304         os_kill_ptraced_process(pid, 1);
 305         return err;
 306 }
 307
 308 void userspace(struct uml_pt_regs *regs)
 309 {
 310         int err, status, op, pid = userspace_pid[0];
 311         /* To prevent races if using_sysemu changes under us.*/
 312         int local_using_sysemu;
 313         siginfo_t si;
 314
 315         /* Handle any immediate reschedules or signals */
 316         interrupt_end();
 317
 318         while (1) {
 319
 320                 /*
 321                  * This can legitimately fail if the process loads a
 322                  * bogus value into a segment register.  It will
 323                  * segfault and PTRACE_GETREGS will read that value
 324                  * out of the process.  However, PTRACE_SETREGS will
 325                  * fail.  In this case, there is nothing to do but
 326                  * just kill the process.
 327                  */
 328                 if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp))
 329                         fatal_sigsegv();
 330
 331                 if (put_fp_registers(pid, regs->fp))
 332                         fatal_sigsegv();
 333
 334                 /* Now we set local_using_sysemu to be used for one loop */
 335                 local_using_sysemu = get_using_sysemu();
 336
 337                 op = SELECT_PTRACE_OPERATION(local_using_sysemu,
 338                                              singlestepping(NULL));
 339
 340                 if (ptrace(op, pid, 0, 0)) {
 341                         printk(UM_KERN_ERR "userspace - ptrace continue "
 342                                "failed, op = %d, errno = %d\n", op, errno);
 343                         fatal_sigsegv();
 344                 }
 345
 346                 CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
 347                 if (err < 0) {
 348                         printk(UM_KERN_ERR "userspace - wait failed, "
 349                                "errno = %d\n", errno);
 350                         fatal_sigsegv();
 351                 }
 352
 353                 regs->is_user = 1;
 354                 if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp)) {
 355                         printk(UM_KERN_ERR "userspace - PTRACE_GETREGS failed, "
 356                                "errno = %d\n", errno);
 357                         fatal_sigsegv();
 358                 }
 359
 360                 if (get_fp_registers(pid, regs->fp)) {
 361                         printk(UM_KERN_ERR "userspace -  get_fp_registers failed, "
 362                                "errno = %d\n", errno);
 363                         fatal_sigsegv();
 364                 }
 365
 366                 UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */
 367
 368                 if (WIFSTOPPED(status)) {
 369                         int sig = WSTOPSIG(status);
 370
 371                         ptrace(PTRACE_GETSIGINFO, pid, 0, (struct siginfo *)&si);
 372
 373                         switch (sig) {
 374                         case SIGSEGV:
 375                                 if (PTRACE_FULL_FAULTINFO) {
 376                                         get_skas_faultinfo(pid,
 377                                                            &regs->faultinfo);
 378                                         (*sig_info[SIGSEGV])(SIGSEGV, (struct siginfo *)&si,
 379                                                              regs);
 380                                 }
 381                                 else handle_segv(pid, regs);
 382                                 break;
 383                         case SIGTRAP + 0x80:
 384                                 handle_trap(pid, regs, local_using_sysemu);
 385                                 break;
 386                         case SIGTRAP:
 387                                 relay_signal(SIGTRAP, (struct siginfo *)&si, regs);
 388                                 break;
 389                         case SIGALRM:
 390                                 break;
 391                         case SIGIO:
 392                         case SIGILL:
 393                         case SIGBUS:
 394                         case SIGFPE:
 395                         case SIGWINCH:
 396                                 block_signals();
 397                                 (*sig_info[sig])(sig, (struct siginfo *)&si, regs);
 398                                 unblock_signals();
 399                                 break;
 400                         default:
 401                                 printk(UM_KERN_ERR "userspace - child stopped "
 402                                        "with signal %d\n", sig);
 403                                 fatal_sigsegv();
 404                         }
 405                         pid = userspace_pid[0];
 406                         interrupt_end();
 407
 408                         /* Avoid -ERESTARTSYS handling in host */
 409                         if (PT_SYSCALL_NR_OFFSET != PT_SYSCALL_RET_OFFSET)
 410                                 PT_SYSCALL_NR(regs->gp) = -1;
 411                 }
 412         }
 413 }
 414
 415 static unsigned long thread_regs[MAX_REG_NR];
 416 static unsigned long thread_fp_regs[FP_SIZE];
 417
 418 static int __init init_thread_regs(void)
 419 {
 420         get_safe_registers(thread_regs, thread_fp_regs);
 421         /* Set parent's instruction pointer to start of clone-stub */
 422         thread_regs[REGS_IP_INDEX] = STUB_CODE +
 423                                 (unsigned long) stub_clone_handler -
 424                                 (unsigned long) __syscall_stub_start;
 425         thread_regs[REGS_SP_INDEX] = STUB_DATA + UM_KERN_PAGE_SIZE -
 426                 sizeof(void *);
 427 #ifdef __SIGNAL_FRAMESIZE
 428         thread_regs[REGS_SP_INDEX] -= __SIGNAL_FRAMESIZE;
 429 #endif
 430         return 0;
 431 }
 432
 433 __initcall(init_thread_regs);
 434
 435 int copy_context_skas0(unsigned long new_stack, int pid)
 436 {
 437         int err;
 438         unsigned long current_stack = current_stub_stack();
 439         struct stub_data *data = (struct stub_data *) current_stack;
 440         struct stub_data *child_data = (struct stub_data *) new_stack;
 441         unsigned long long new_offset;
 442         int new_fd = phys_mapping(to_phys((void *)new_stack), &new_offset);
 443
 444         /*
 445          * prepare offset and fd of child's stack as argument for parent's
 446          * and child's mmap2 calls
 447          */
 448         *data = ((struct stub_data) {
 449                         .offset = MMAP_OFFSET(new_offset),
 450                         .fd     = new_fd
 451         });
 452
 453         err = ptrace_setregs(pid, thread_regs);
 454         if (err < 0) {
 455                 err = -errno;
 456                 printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_SETREGS "
 457                        "failed, pid = %d, errno = %d\n", pid, -err);
 458                 return err;
 459         }
 460
 461         err = put_fp_registers(pid, thread_fp_regs);
 462         if (err < 0) {
 463                 printk(UM_KERN_ERR "copy_context_skas0 : put_fp_registers "
 464                        "failed, pid = %d, err = %d\n", pid, err);
 465                 return err;
 466         }
 467
 468         /* set a well known return code for detection of child write failure */
 469         child_data->err = 12345678;
 470
 471         /*
 472          * Wait, until parent has finished its work: read child's pid from
 473          * parent's stack, and check, if bad result.
 474          */
 475         err = ptrace(PTRACE_CONT, pid, 0, 0);
 476         if (err) {
 477                 err = -errno;
 478                 printk(UM_KERN_ERR "Failed to continue new process, pid = %d, "
 479                        "errno = %d\n", pid, errno);
 480                 return err;
 481         }
 482
 483         wait_stub_done(pid);
 484
 485         pid = data->err;
 486         if (pid < 0) {
 487                 printk(UM_KERN_ERR "copy_context_skas0 - stub-parent reports "
 488                        "error %d\n", -pid);
 489                 return pid;
 490         }
 491
 492         /*
 493          * Wait, until child has finished too: read child's result from
 494          * child's stack and check it.
 495          */
 496         wait_stub_done(pid);
 497         if (child_data->err != STUB_DATA) {
 498                 printk(UM_KERN_ERR "copy_context_skas0 - stub-child reports "
 499                        "error %ld\n", child_data->err);
 500                 err = child_data->err;
 501                 goto out_kill;
 502         }
 503
 504         if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
 505                    (void *)PTRACE_O_TRACESYSGOOD) < 0) {
 506                 err = -errno;
 507                 printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_OLDSETOPTIONS "
 508                        "failed, errno = %d\n", errno);
 509                 goto out_kill;
 510         }
 511
 512         return pid;
 513
 514  out_kill:
 515         os_kill_ptraced_process(pid, 1);
 516         return err;
 517 }
 518
 519 void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
 520 {
 521         (*buf)[0].JB_IP = (unsigned long) handler;
 522         (*buf)[0].JB_SP = (unsigned long) stack + UM_THREAD_SIZE -
 523                 sizeof(void *);
 524 }
 525
 526 #define INIT_JMP_NEW_THREAD 0
 527 #define INIT_JMP_CALLBACK 1
 528 #define INIT_JMP_HALT 2
 529 #define INIT_JMP_REBOOT 3
 530
 531 void switch_threads(jmp_buf *me, jmp_buf *you)
 532 {
 533         if (UML_SETJMP(me) == 0)
 534                 UML_LONGJMP(you, 1);
 535 }
 536
 537 static jmp_buf initial_jmpbuf;
 538
 539 /* XXX Make these percpu */
 540 static void (*cb_proc)(void *arg);
 541 static void *cb_arg;
 542 static jmp_buf *cb_back;
 543
 544 int start_idle_thread(void *stack, jmp_buf *switch_buf)
 545 {
 546         int n;
 547
 548         set_handler(SIGWINCH);
 549
 550         /*
 551          * Can't use UML_SETJMP or UML_LONGJMP here because they save
 552          * and restore signals, with the possible side-effect of
 553          * trying to handle any signals which came when they were
 554          * blocked, which can't be done on this stack.
 555          * Signals must be blocked when jumping back here and restored
 556          * after returning to the jumper.
 557          */
 558         n = setjmp(initial_jmpbuf);
 559         switch (n) {
 560         case INIT_JMP_NEW_THREAD:
 561                 (*switch_buf)[0].JB_IP = (unsigned long) uml_finishsetup;
 562                 (*switch_buf)[0].JB_SP = (unsigned long) stack +
 563                         UM_THREAD_SIZE - sizeof(void *);
 564                 break;
 565         case INIT_JMP_CALLBACK:
 566                 (*cb_proc)(cb_arg);
 567                 longjmp(*cb_back, 1);
 568                 break;
 569         case INIT_JMP_HALT:
 570                 kmalloc_ok = 0;
 571                 return 0;
 572         case INIT_JMP_REBOOT:
 573                 kmalloc_ok = 0;
 574                 return 1;
 575         default:
 576                 printk(UM_KERN_ERR "Bad sigsetjmp return in "
 577                        "start_idle_thread - %d\n", n);
 578                 fatal_sigsegv();
 579         }
 580         longjmp(*switch_buf, 1);
 581 }
 582
 583 void initial_thread_cb_skas(void (*proc)(void *), void *arg)
 584 {
 585         jmp_buf here;
 586
 587         cb_proc = proc;
 588         cb_arg = arg;
 589         cb_back = &here;
 590
 591         block_signals();
 592         if (UML_SETJMP(&here) == 0)
 593                 UML_LONGJMP(&initial_jmpbuf, INIT_JMP_CALLBACK);
 594         unblock_signals();
 595
 596         cb_proc = NULL;
 597         cb_arg = NULL;
 598         cb_back = NULL;
 599 }
 600
 601 void halt_skas(void)
 602 {
 603         block_signals();
 604         UML_LONGJMP(&initial_jmpbuf, INIT_JMP_HALT);
 605 }
 606
 607 void reboot_skas(void)
 608 {
 609         block_signals();
 610         UML_LONGJMP(&initial_jmpbuf, INIT_JMP_REBOOT);
 611 }
 612
 613 void __switch_mm(struct mm_id *mm_idp)
 614 {
 615         userspace_pid[0] = mm_idp->u.pid;
 616 }