kernel/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 int get_syscall(struct uml_pt_regs *regs)
 176 {
 177         UPT_SYSCALL_NR(regs) = PT_SYSCALL_NR(regs->gp);
 178
 179         return UPT_SYSCALL_NR(regs);
 180 }
 181
 182 extern char __syscall_stub_start[];
 183
 184 static int userspace_tramp(void *stack)
 185 {
 186         void *addr;
 187         int fd;
 188         unsigned long long offset;
 189
 190         ptrace(PTRACE_TRACEME, 0, 0, 0);
 191
 192         signal(SIGTERM, SIG_DFL);
 193         signal(SIGWINCH, SIG_IGN);
 194
 195         /*
 196          * This has a pte, but it can't be mapped in with the usual
 197          * tlb_flush mechanism because this is part of that mechanism
 198          */
 199         fd = phys_mapping(to_phys(__syscall_stub_start), &offset);
 200         addr = mmap64((void *) STUB_CODE, UM_KERN_PAGE_SIZE,
 201                       PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset);
 202         if (addr == MAP_FAILED) {
 203                 printk(UM_KERN_ERR "mapping mmap stub at 0x%lx failed, "
 204                        "errno = %d\n", STUB_CODE, errno);
 205                 exit(1);
 206         }
 207
 208         if (stack != NULL) {
 209                 fd = phys_mapping(to_phys(stack), &offset);
 210                 addr = mmap((void *) STUB_DATA,
 211                             UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
 212                             MAP_FIXED | MAP_SHARED, fd, offset);
 213                 if (addr == MAP_FAILED) {
 214                         printk(UM_KERN_ERR "mapping segfault stack "
 215                                "at 0x%lx failed, errno = %d\n",
 216                                STUB_DATA, errno);
 217                         exit(1);
 218                 }
 219         }
 220         if (stack != NULL) {
 221                 struct sigaction sa;
 222
 223                 unsigned long v = STUB_CODE +
 224                                   (unsigned long) stub_segv_handler -
 225                                   (unsigned long) __syscall_stub_start;
 226
 227                 set_sigstack((void *) STUB_DATA, UM_KERN_PAGE_SIZE);
 228                 sigemptyset(&sa.sa_mask);
 229                 sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO;
 230                 sa.sa_sigaction = (void *) v;
 231                 sa.sa_restorer = NULL;
 232                 if (sigaction(SIGSEGV, &sa, NULL) < 0) {
 233                         printk(UM_KERN_ERR "userspace_tramp - setting SIGSEGV "
 234                                "handler failed - errno = %d\n", errno);
 235                         exit(1);
 236                 }
 237         }
 238
 239         kill(os_getpid(), SIGSTOP);
 240         return 0;
 241 }
 242
 243 /* Each element set once, and only accessed by a single processor anyway */
 244 #undef NR_CPUS
 245 #define NR_CPUS 1
 246 int userspace_pid[NR_CPUS];
 247
 248 int start_userspace(unsigned long stub_stack)
 249 {
 250         void *stack;
 251         unsigned long sp;
 252         int pid, status, n, flags, err;
 253
 254         stack = mmap(NULL, UM_KERN_PAGE_SIZE,
 255                      PROT_READ | PROT_WRITE | PROT_EXEC,
 256                      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 257         if (stack == MAP_FAILED) {
 258                 err = -errno;
 259                 printk(UM_KERN_ERR "start_userspace : mmap failed, "
 260                        "errno = %d\n", errno);
 261                 return err;
 262         }
 263
 264         sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
 265
 266         flags = CLONE_FILES | SIGCHLD;
 267
 268         pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
 269         if (pid < 0) {
 270                 err = -errno;
 271                 printk(UM_KERN_ERR "start_userspace : clone failed, "
 272                        "errno = %d\n", errno);
 273                 return err;
 274         }
 275
 276         do {
 277                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
 278                 if (n < 0) {
 279                         err = -errno;
 280                         printk(UM_KERN_ERR "start_userspace : wait failed, "
 281                                "errno = %d\n", errno);
 282                         goto out_kill;
 283                 }
 284         } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM));
 285
 286         if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
 287                 err = -EINVAL;
 288                 printk(UM_KERN_ERR "start_userspace : expected SIGSTOP, got "
 289                        "status = %d\n", status);
 290                 goto out_kill;
 291         }
 292
 293         if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
 294                    (void *) PTRACE_O_TRACESYSGOOD) < 0) {
 295                 err = -errno;
 296                 printk(UM_KERN_ERR "start_userspace : PTRACE_OLDSETOPTIONS "
 297                        "failed, errno = %d\n", errno);
 298                 goto out_kill;
 299         }
 300
 301         if (munmap(stack, UM_KERN_PAGE_SIZE) < 0) {
 302                 err = -errno;
 303                 printk(UM_KERN_ERR "start_userspace : munmap failed, "
 304                        "errno = %d\n", errno);
 305                 goto out_kill;
 306         }
 307
 308         return pid;
 309
 310  out_kill:
 311         os_kill_ptraced_process(pid, 1);
 312         return err;
 313 }
 314
 315 void userspace(struct uml_pt_regs *regs)
 316 {
 317         int err, status, op, pid = userspace_pid[0];
 318         /* To prevent races if using_sysemu changes under us.*/
 319         int local_using_sysemu;
 320         siginfo_t si;
 321
 322         /* Handle any immediate reschedules or signals */
 323         interrupt_end();
 324
 325         while (1) {
 326
 327                 /*
 328                  * This can legitimately fail if the process loads a
 329                  * bogus value into a segment register.  It will
 330                  * segfault and PTRACE_GETREGS will read that value
 331                  * out of the process.  However, PTRACE_SETREGS will
 332                  * fail.  In this case, there is nothing to do but
 333                  * just kill the process.
 334                  */
 335                 if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp))
 336                         fatal_sigsegv();
 337
 338                 if (put_fp_registers(pid, regs->fp))
 339                         fatal_sigsegv();
 340
 341                 /* Now we set local_using_sysemu to be used for one loop */
 342                 local_using_sysemu = get_using_sysemu();
 343
 344                 op = SELECT_PTRACE_OPERATION(local_using_sysemu,
 345                                              singlestepping(NULL));
 346
 347                 if (ptrace(op, pid, 0, 0)) {
 348                         printk(UM_KERN_ERR "userspace - ptrace continue "
 349                                "failed, op = %d, errno = %d\n", op, errno);
 350                         fatal_sigsegv();
 351                 }
 352
 353                 CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
 354                 if (err < 0) {
 355                         printk(UM_KERN_ERR "userspace - wait failed, "
 356                                "errno = %d\n", errno);
 357                         fatal_sigsegv();
 358                 }
 359
 360                 regs->is_user = 1;
 361                 if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp)) {
 362                         printk(UM_KERN_ERR "userspace - PTRACE_GETREGS failed, "
 363                                "errno = %d\n", errno);
 364                         fatal_sigsegv();
 365                 }
 366
 367                 if (get_fp_registers(pid, regs->fp)) {
 368                         printk(UM_KERN_ERR "userspace -  get_fp_registers failed, "
 369                                "errno = %d\n", errno);
 370                         fatal_sigsegv();
 371                 }
 372
 373                 UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */
 374
 375                 if (WIFSTOPPED(status)) {
 376                         int sig = WSTOPSIG(status);
 377
 378                         ptrace(PTRACE_GETSIGINFO, pid, 0, (struct siginfo *)&si);
 379
 380                         switch (sig) {
 381                         case SIGSEGV:
 382                                 if (PTRACE_FULL_FAULTINFO) {
 383                                         get_skas_faultinfo(pid,
 384                                                            &regs->faultinfo);
 385                                         (*sig_info[SIGSEGV])(SIGSEGV, (struct siginfo *)&si,
 386                                                              regs);
 387                                 }
 388                                 else handle_segv(pid, regs);
 389                                 break;
 390                         case SIGTRAP + 0x80:
 391                                 handle_trap(pid, regs, local_using_sysemu);
 392                                 break;
 393                         case SIGTRAP:
 394                                 relay_signal(SIGTRAP, (struct siginfo *)&si, regs);
 395                                 break;
 396                         case SIGALRM:
 397                                 break;
 398                         case SIGIO:
 399                         case SIGILL:
 400                         case SIGBUS:
 401                         case SIGFPE:
 402                         case SIGWINCH:
 403                                 block_signals();
 404                                 (*sig_info[sig])(sig, (struct siginfo *)&si, regs);
 405                                 unblock_signals();
 406                                 break;
 407                         default:
 408                                 printk(UM_KERN_ERR "userspace - child stopped "
 409                                        "with signal %d\n", sig);
 410                                 fatal_sigsegv();
 411                         }
 412                         pid = userspace_pid[0];
 413                         interrupt_end();
 414
 415                         /* Avoid -ERESTARTSYS handling in host */
 416                         if (PT_SYSCALL_NR_OFFSET != PT_SYSCALL_RET_OFFSET)
 417                                 PT_SYSCALL_NR(regs->gp) = -1;
 418                 }
 419         }
 420 }
 421
 422 static unsigned long thread_regs[MAX_REG_NR];
 423 static unsigned long thread_fp_regs[FP_SIZE];
 424
 425 static int __init init_thread_regs(void)
 426 {
 427         get_safe_registers(thread_regs, thread_fp_regs);
 428         /* Set parent's instruction pointer to start of clone-stub */
 429         thread_regs[REGS_IP_INDEX] = STUB_CODE +
 430                                 (unsigned long) stub_clone_handler -
 431                                 (unsigned long) __syscall_stub_start;
 432         thread_regs[REGS_SP_INDEX] = STUB_DATA + UM_KERN_PAGE_SIZE -
 433                 sizeof(void *);
 434 #ifdef __SIGNAL_FRAMESIZE
 435         thread_regs[REGS_SP_INDEX] -= __SIGNAL_FRAMESIZE;
 436 #endif
 437         return 0;
 438 }
 439
 440 __initcall(init_thread_regs);
 441
 442 int copy_context_skas0(unsigned long new_stack, int pid)
 443 {
 444         int err;
 445         unsigned long current_stack = current_stub_stack();
 446         struct stub_data *data = (struct stub_data *) current_stack;
 447         struct stub_data *child_data = (struct stub_data *) new_stack;
 448         unsigned long long new_offset;
 449         int new_fd = phys_mapping(to_phys((void *)new_stack), &new_offset);
 450
 451         /*
 452          * prepare offset and fd of child's stack as argument for parent's
 453          * and child's mmap2 calls
 454          */
 455         *data = ((struct stub_data) {
 456                         .offset = MMAP_OFFSET(new_offset),
 457                         .fd     = new_fd
 458         });
 459
 460         err = ptrace_setregs(pid, thread_regs);
 461         if (err < 0) {
 462                 err = -errno;
 463                 printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_SETREGS "
 464                        "failed, pid = %d, errno = %d\n", pid, -err);
 465                 return err;
 466         }
 467
 468         err = put_fp_registers(pid, thread_fp_regs);
 469         if (err < 0) {
 470                 printk(UM_KERN_ERR "copy_context_skas0 : put_fp_registers "
 471                        "failed, pid = %d, err = %d\n", pid, err);
 472                 return err;
 473         }
 474
 475         /* set a well known return code for detection of child write failure */
 476         child_data->err = 12345678;
 477
 478         /*
 479          * Wait, until parent has finished its work: read child's pid from
 480          * parent's stack, and check, if bad result.
 481          */
 482         err = ptrace(PTRACE_CONT, pid, 0, 0);
 483         if (err) {
 484                 err = -errno;
 485                 printk(UM_KERN_ERR "Failed to continue new process, pid = %d, "
 486                        "errno = %d\n", pid, errno);
 487                 return err;
 488         }
 489
 490         wait_stub_done(pid);
 491
 492         pid = data->err;
 493         if (pid < 0) {
 494                 printk(UM_KERN_ERR "copy_context_skas0 - stub-parent reports "
 495                        "error %d\n", -pid);
 496                 return pid;
 497         }
 498
 499         /*
 500          * Wait, until child has finished too: read child's result from
 501          * child's stack and check it.
 502          */
 503         wait_stub_done(pid);
 504         if (child_data->err != STUB_DATA) {
 505                 printk(UM_KERN_ERR "copy_context_skas0 - stub-child reports "
 506                        "error %ld\n", child_data->err);
 507                 err = child_data->err;
 508                 goto out_kill;
 509         }
 510
 511         if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
 512                    (void *)PTRACE_O_TRACESYSGOOD) < 0) {
 513                 err = -errno;
 514                 printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_OLDSETOPTIONS "
 515                        "failed, errno = %d\n", errno);
 516                 goto out_kill;
 517         }
 518
 519         return pid;
 520
 521  out_kill:
 522         os_kill_ptraced_process(pid, 1);
 523         return err;
 524 }
 525
 526 void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
 527 {
 528         (*buf)[0].JB_IP = (unsigned long) handler;
 529         (*buf)[0].JB_SP = (unsigned long) stack + UM_THREAD_SIZE -
 530                 sizeof(void *);
 531 }
 532
 533 #define INIT_JMP_NEW_THREAD 0
 534 #define INIT_JMP_CALLBACK 1
 535 #define INIT_JMP_HALT 2
 536 #define INIT_JMP_REBOOT 3
 537
 538 void switch_threads(jmp_buf *me, jmp_buf *you)
 539 {
 540         if (UML_SETJMP(me) == 0)
 541                 UML_LONGJMP(you, 1);
 542 }
 543
 544 static jmp_buf initial_jmpbuf;
 545
 546 /* XXX Make these percpu */
 547 static void (*cb_proc)(void *arg);
 548 static void *cb_arg;
 549 static jmp_buf *cb_back;
 550
 551 int start_idle_thread(void *stack, jmp_buf *switch_buf)
 552 {
 553         int n;
 554
 555         set_handler(SIGWINCH);
 556
 557         /*
 558          * Can't use UML_SETJMP or UML_LONGJMP here because they save
 559          * and restore signals, with the possible side-effect of
 560          * trying to handle any signals which came when they were
 561          * blocked, which can't be done on this stack.
 562          * Signals must be blocked when jumping back here and restored
 563          * after returning to the jumper.
 564          */
 565         n = setjmp(initial_jmpbuf);
 566         switch (n) {
 567         case INIT_JMP_NEW_THREAD:
 568                 (*switch_buf)[0].JB_IP = (unsigned long) uml_finishsetup;
 569                 (*switch_buf)[0].JB_SP = (unsigned long) stack +
 570                         UM_THREAD_SIZE - sizeof(void *);
 571                 break;
 572         case INIT_JMP_CALLBACK:
 573                 (*cb_proc)(cb_arg);
 574                 longjmp(*cb_back, 1);
 575                 break;
 576         case INIT_JMP_HALT:
 577                 kmalloc_ok = 0;
 578                 return 0;
 579         case INIT_JMP_REBOOT:
 580                 kmalloc_ok = 0;
 581                 return 1;
 582         default:
 583                 printk(UM_KERN_ERR "Bad sigsetjmp return in "
 584                        "start_idle_thread - %d\n", n);
 585                 fatal_sigsegv();
 586         }
 587         longjmp(*switch_buf, 1);
 588 }
 589
 590 void initial_thread_cb_skas(void (*proc)(void *), void *arg)
 591 {
 592         jmp_buf here;
 593
 594         cb_proc = proc;
 595         cb_arg = arg;
 596         cb_back = &here;
 597
 598         block_signals();
 599         if (UML_SETJMP(&here) == 0)
 600                 UML_LONGJMP(&initial_jmpbuf, INIT_JMP_CALLBACK);
 601         unblock_signals();
 602
 603         cb_proc = NULL;
 604         cb_arg = NULL;
 605         cb_back = NULL;
 606 }
 607
 608 void halt_skas(void)
 609 {
 610         block_signals();
 611         UML_LONGJMP(&initial_jmpbuf, INIT_JMP_HALT);
 612 }
 613
 614 void reboot_skas(void)
 615 {
 616         block_signals();
 617         UML_LONGJMP(&initial_jmpbuf, INIT_JMP_REBOOT);
 618 }
 619
 620 void __switch_mm(struct mm_id *mm_idp)
 621 {
 622         userspace_pid[0] = mm_idp->u.pid;
 623 }