arch/um/os-Linux/start_up.c

   1 /*
   2  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <stdarg.h>
   9 #include <unistd.h>
  10 #include <errno.h>
  11 #include <fcntl.h>
  12 #include <sched.h>
  13 #include <signal.h>
  14 #include <string.h>
  15 #include <sys/mman.h>
  16 #include <sys/ptrace.h>
  17 #include <sys/stat.h>
  18 #include <sys/wait.h>
  19 #include <asm/unistd.h>
  20 #include "init.h"
  21 #include "kern_constants.h"
  22 #include "os.h"
  23 #include "mem_user.h"
  24 #include "ptrace_user.h"
  25 #include "registers.h"
  26 #include "skas.h"
  27 #include "skas_ptrace.h"
  28
  29 static void ptrace_child(void)
  30 {
  31         int ret;
  32         /* Calling os_getpid because some libcs cached getpid incorrectly */
  33         int pid = os_getpid(), ppid = getppid();
  34         int sc_result;
  35
  36         if (change_sig(SIGWINCH, 0) < 0 ||
  37             ptrace(PTRACE_TRACEME, 0, 0, 0) < 0) {
  38                 perror("ptrace");
  39                 kill(pid, SIGKILL);
  40         }
  41         kill(pid, SIGSTOP);
  42
  43         /*
  44          * This syscall will be intercepted by the parent. Don't call more than
  45          * once, please.
  46          */
  47         sc_result = os_getpid();
  48
  49         if (sc_result == pid)
  50                 /* Nothing modified by the parent, we are running normally. */
  51                 ret = 1;
  52         else if (sc_result == ppid)
  53                 /*
  54                  * Expected in check_ptrace and check_sysemu when they succeed
  55                  * in modifying the stack frame
  56                  */
  57                 ret = 0;
  58         else
  59                 /* Serious trouble! This could be caused by a bug in host 2.6
  60                  * SKAS3/2.6 patch before release -V6, together with a bug in
  61                  * the UML code itself.
  62                  */
  63                 ret = 2;
  64
  65         exit(ret);
  66 }
  67
  68 static void fatal_perror(const char *str)
  69 {
  70         perror(str);
  71         exit(1);
  72 }
  73
  74 static void fatal(char *fmt, ...)
  75 {
  76         va_list list;
  77
  78         va_start(list, fmt);
  79         vfprintf(stderr, fmt, list);
  80         va_end(list);
  81
  82         exit(1);
  83 }
  84
  85 static void non_fatal(char *fmt, ...)
  86 {
  87         va_list list;
  88
  89         va_start(list, fmt);
  90         vfprintf(stderr, fmt, list);
  91         va_end(list);
  92 }
  93
  94 static int start_ptraced_child(void)
  95 {
  96         int pid, n, status;
  97
  98         pid = fork();
  99         if (pid == 0)
 100                 ptrace_child();
 101         else if (pid < 0)
 102                 fatal_perror("start_ptraced_child : fork failed");
 103
 104         CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 105         if (n < 0)
 106                 fatal_perror("check_ptrace : waitpid failed");
 107         if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
 108                 fatal("check_ptrace : expected SIGSTOP, got status = %d",
 109                       status);
 110
 111         return pid;
 112 }
 113
 114 /* When testing for SYSEMU support, if it is one of the broken versions, we
 115  * must just avoid using sysemu, not panic, but only if SYSEMU features are
 116  * broken.
 117  * So only for SYSEMU features we test mustpanic, while normal host features
 118  * must work anyway!
 119  */
 120 static int stop_ptraced_child(int pid, int exitcode, int mustexit)
 121 {
 122         int status, n, ret = 0;
 123
 124         if (ptrace(PTRACE_CONT, pid, 0, 0) < 0) {
 125                 perror("stop_ptraced_child : ptrace failed");
 126                 return -1;
 127         }
 128         CATCH_EINTR(n = waitpid(pid, &status, 0));
 129         if (!WIFEXITED(status) || (WEXITSTATUS(status) != exitcode)) {
 130                 int exit_with = WEXITSTATUS(status);
 131                 if (exit_with == 2)
 132                         non_fatal("check_ptrace : child exited with status 2. "
 133                                   "\nDisabling SYSEMU support.\n");
 134                 non_fatal("check_ptrace : child exited with exitcode %d, while "
 135                           "expecting %d; status 0x%x\n", exit_with,
 136                           exitcode, status);
 137                 if (mustexit)
 138                         exit(1);
 139                 ret = -1;
 140         }
 141
 142         return ret;
 143 }
 144
 145 /* Changed only during early boot */
 146 int ptrace_faultinfo;
 147 static int disable_ptrace_faultinfo;
 148
 149 int ptrace_ldt;
 150 static int disable_ptrace_ldt;
 151
 152 int proc_mm;
 153 static int disable_proc_mm;
 154
 155 int have_switch_mm;
 156 static int disable_switch_mm;
 157
 158 int skas_needs_stub;
 159
 160 static int __init skas0_cmd_param(char *str, int* add)
 161 {
 162         disable_ptrace_faultinfo = 1;
 163         disable_ptrace_ldt = 1;
 164         disable_proc_mm = 1;
 165         disable_switch_mm = 1;
 166
 167         return 0;
 168 }
 169
 170 /* The two __uml_setup would conflict, without this stupid alias. */
 171
 172 static int __init mode_skas0_cmd_param(char *str, int* add)
 173         __attribute__((alias("skas0_cmd_param")));
 174
 175 __uml_setup("skas0", skas0_cmd_param,
 176 "skas0\n"
 177 "    Disables SKAS3 and SKAS4 usage, so that SKAS0 is used\n\n");
 178
 179 __uml_setup("mode=skas0", mode_skas0_cmd_param,
 180 "mode=skas0\n"
 181 "    Disables SKAS3 and SKAS4 usage, so that SKAS0 is used.\n\n");
 182
 183 /* Changed only during early boot */
 184 static int force_sysemu_disabled = 0;
 185
 186 static int __init nosysemu_cmd_param(char *str, int* add)
 187 {
 188         force_sysemu_disabled = 1;
 189         return 0;
 190 }
 191
 192 __uml_setup("nosysemu", nosysemu_cmd_param,
 193 "nosysemu\n"
 194 "    Turns off syscall emulation patch for ptrace (SYSEMU) on.\n"
 195 "    SYSEMU is a performance-patch introduced by Laurent Vivier. It changes\n"
 196 "    behaviour of ptrace() and helps reducing host context switch rate.\n"
 197 "    To make it working, you need a kernel patch for your host, too.\n"
 198 "    See http://perso.wanadoo.fr/laurent.vivier/UML/ for further \n"
 199 "    information.\n\n");
 200
 201 static void __init check_sysemu(void)
 202 {
 203         unsigned long regs[MAX_REG_NR];
 204         int pid, n, status, count=0;
 205
 206         non_fatal("Checking syscall emulation patch for ptrace...");
 207         sysemu_supported = 0;
 208         pid = start_ptraced_child();
 209
 210         if (ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
 211                 goto fail;
 212
 213         CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 214         if (n < 0)
 215                 fatal_perror("check_sysemu : wait failed");
 216         if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
 217                 fatal("check_sysemu : expected SIGTRAP, got status = %d\n",
 218                       status);
 219
 220         if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
 221                 fatal_perror("check_sysemu : PTRACE_GETREGS failed");
 222         if (PT_SYSCALL_NR(regs) != __NR_getpid) {
 223                 non_fatal("check_sysemu got system call number %d, "
 224                           "expected %d...", PT_SYSCALL_NR(regs), __NR_getpid);
 225                 goto fail;
 226         }
 227
 228         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET, os_getpid());
 229         if (n < 0) {
 230                 non_fatal("check_sysemu : failed to modify system call "
 231                           "return");
 232                 goto fail;
 233         }
 234
 235         if (stop_ptraced_child(pid, 0, 0) < 0)
 236                 goto fail_stopped;
 237
 238         sysemu_supported = 1;
 239         non_fatal("OK\n");
 240         set_using_sysemu(!force_sysemu_disabled);
 241
 242         non_fatal("Checking advanced syscall emulation patch for ptrace...");
 243         pid = start_ptraced_child();
 244
 245         if ((ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
 246                    (void *) PTRACE_O_TRACESYSGOOD) < 0))
 247                 fatal_perror("check_sysemu: PTRACE_OLDSETOPTIONS failed");
 248
 249         while (1) {
 250                 count++;
 251                 if (ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
 252                         goto fail;
 253                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 254                 if (n < 0)
 255                         fatal_perror("check_sysemu: wait failed");
 256
 257                 if (WIFSTOPPED(status) &&
 258                     (WSTOPSIG(status) == (SIGTRAP|0x80))) {
 259                         if (!count) {
 260                                 non_fatal("check_sysemu: SYSEMU_SINGLESTEP "
 261                                           "doesn't singlestep");
 262                                 goto fail;
 263                         }
 264                         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
 265                                    os_getpid());
 266                         if (n < 0)
 267                                 fatal_perror("check_sysemu : failed to modify "
 268                                              "system call return");
 269                         break;
 270                 }
 271                 else if (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGTRAP))
 272                         count++;
 273                 else {
 274                         non_fatal("check_sysemu: expected SIGTRAP or "
 275                                   "(SIGTRAP | 0x80), got status = %d\n",
 276                                   status);
 277                         goto fail;
 278                 }
 279         }
 280         if (stop_ptraced_child(pid, 0, 0) < 0)
 281                 goto fail_stopped;
 282
 283         sysemu_supported = 2;
 284         non_fatal("OK\n");
 285
 286         if (!force_sysemu_disabled)
 287                 set_using_sysemu(sysemu_supported);
 288         return;
 289
 290 fail:
 291         stop_ptraced_child(pid, 1, 0);
 292 fail_stopped:
 293         non_fatal("missing\n");
 294 }
 295
 296 static void __init check_ptrace(void)
 297 {
 298         int pid, syscall, n, status;
 299
 300         non_fatal("Checking that ptrace can change system call numbers...");
 301         pid = start_ptraced_child();
 302
 303         if ((ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
 304                    (void *) PTRACE_O_TRACESYSGOOD) < 0))
 305                 fatal_perror("check_ptrace: PTRACE_OLDSETOPTIONS failed");
 306
 307         while (1) {
 308                 if (ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)
 309                         fatal_perror("check_ptrace : ptrace failed");
 310
 311                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 312                 if (n < 0)
 313                         fatal_perror("check_ptrace : wait failed");
 314
 315                 if (!WIFSTOPPED(status) ||
 316                    (WSTOPSIG(status) != (SIGTRAP | 0x80)))
 317                         fatal("check_ptrace : expected (SIGTRAP|0x80), "
 318                                "got status = %d", status);
 319
 320                 syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
 321                                  0);
 322                 if (syscall == __NR_getpid) {
 323                         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
 324                                    __NR_getppid);
 325                         if (n < 0)
 326                                 fatal_perror("check_ptrace : failed to modify "
 327                                              "system call");
 328                         break;
 329                 }
 330         }
 331         stop_ptraced_child(pid, 0, 1);
 332         non_fatal("OK\n");
 333         check_sysemu();
 334 }
 335
 336 extern void check_tmpexec(void);
 337
 338 static void __init check_coredump_limit(void)
 339 {
 340         struct rlimit lim;
 341         int err = getrlimit(RLIMIT_CORE, &lim);
 342
 343         if (err) {
 344                 perror("Getting core dump limit");
 345                 return;
 346         }
 347
 348         printf("Core dump limits :\n\tsoft - ");
 349         if (lim.rlim_cur == RLIM_INFINITY)
 350                 printf("NONE\n");
 351         else printf("%lu\n", lim.rlim_cur);
 352
 353         printf("\thard - ");
 354         if (lim.rlim_max == RLIM_INFINITY)
 355                 printf("NONE\n");
 356         else printf("%lu\n", lim.rlim_max);
 357 }
 358
 359 void __init os_early_checks(void)
 360 {
 361         int pid;
 362
 363         /* Print out the core dump limits early */
 364         check_coredump_limit();
 365
 366         check_ptrace();
 367
 368         /* Need to check this early because mmapping happens before the
 369          * kernel is running.
 370          */
 371         check_tmpexec();
 372
 373         pid = start_ptraced_child();
 374         if (init_registers(pid))
 375                 fatal("Failed to initialize default registers");
 376         stop_ptraced_child(pid, 1, 1);
 377 }
 378
 379 static int __init noprocmm_cmd_param(char *str, int* add)
 380 {
 381         disable_proc_mm = 1;
 382         return 0;
 383 }
 384
 385 __uml_setup("noprocmm", noprocmm_cmd_param,
 386 "noprocmm\n"
 387 "    Turns off usage of /proc/mm, even if host supports it.\n"
 388 "    To support /proc/mm, the host needs to be patched using\n"
 389 "    the current skas3 patch.\n\n");
 390
 391 static int __init noptracefaultinfo_cmd_param(char *str, int* add)
 392 {
 393         disable_ptrace_faultinfo = 1;
 394         return 0;
 395 }
 396
 397 __uml_setup("noptracefaultinfo", noptracefaultinfo_cmd_param,
 398 "noptracefaultinfo\n"
 399 "    Turns off usage of PTRACE_FAULTINFO, even if host supports\n"
 400 "    it. To support PTRACE_FAULTINFO, the host needs to be patched\n"
 401 "    using the current skas3 patch.\n\n");
 402
 403 static int __init noptraceldt_cmd_param(char *str, int* add)
 404 {
 405         disable_ptrace_ldt = 1;
 406         return 0;
 407 }
 408
 409 __uml_setup("noptraceldt", noptraceldt_cmd_param,
 410 "noptraceldt\n"
 411 "    Turns off usage of PTRACE_LDT, even if host supports it.\n"
 412 "    To support PTRACE_LDT, the host needs to be patched using\n"
 413 "    the current skas3 patch.\n\n");
 414
 415 static inline void check_skas3_ptrace_faultinfo(void)
 416 {
 417         struct ptrace_faultinfo fi;
 418         int pid, n;
 419
 420         non_fatal("  - PTRACE_FAULTINFO...");
 421         pid = start_ptraced_child();
 422
 423         n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
 424         if (n < 0) {
 425                 if (errno == EIO)
 426                         non_fatal("not found\n");
 427                 else
 428                         perror("not found");
 429         } else if (disable_ptrace_faultinfo)
 430                 non_fatal("found but disabled on command line\n");
 431         else {
 432                 ptrace_faultinfo = 1;
 433                 non_fatal("found\n");
 434         }
 435
 436         stop_ptraced_child(pid, 1, 1);
 437 }
 438
 439 static inline void check_skas3_ptrace_ldt(void)
 440 {
 441 #ifdef PTRACE_LDT
 442         int pid, n;
 443         unsigned char ldtbuf[40];
 444         struct ptrace_ldt ldt_op = (struct ptrace_ldt) {
 445                 .func = 2, /* read default ldt */
 446                 .ptr = ldtbuf,
 447                 .bytecount = sizeof(ldtbuf)};
 448
 449         non_fatal("  - PTRACE_LDT...");
 450         pid = start_ptraced_child();
 451
 452         n = ptrace(PTRACE_LDT, pid, 0, (unsigned long) &ldt_op);
 453         if (n < 0) {
 454                 if (errno == EIO)
 455                         non_fatal("not found\n");
 456                 else
 457                         perror("not found");
 458         } else if (disable_ptrace_ldt)
 459                 non_fatal("found, but use is disabled\n");
 460         else {
 461                 ptrace_ldt = 1;
 462                 non_fatal("found\n");
 463         }
 464
 465         stop_ptraced_child(pid, 1, 1);
 466 #endif
 467 }
 468
 469 static inline void check_skas3_proc_mm(void)
 470 {
 471         non_fatal("  - /proc/mm...");
 472         if (access("/proc/mm", W_OK) < 0)
 473                 perror("not found");
 474         else if (disable_proc_mm)
 475                 non_fatal("found but disabled on command line\n");
 476         else {
 477                 proc_mm = 1;
 478                 non_fatal("found\n");
 479         }
 480 }
 481
 482 void can_do_skas(void)
 483 {
 484         non_fatal("Checking for the skas3 patch in the host:\n");
 485
 486         check_skas3_proc_mm();
 487         check_skas3_ptrace_faultinfo();
 488         check_skas3_ptrace_ldt();
 489
 490         if (!proc_mm || !ptrace_faultinfo || !ptrace_ldt)
 491                 skas_needs_stub = 1;
 492 }
 493
 494 int __init parse_iomem(char *str, int *add)
 495 {
 496         struct iomem_region *new;
 497         struct stat64 buf;
 498         char *file, *driver;
 499         int fd, size;
 500
 501         driver = str;
 502         file = strchr(str,',');
 503         if (file == NULL) {
 504                 fprintf(stderr, "parse_iomem : failed to parse iomem\n");
 505                 goto out;
 506         }
 507         *file = '\0';
 508         file++;
 509         fd = open(file, O_RDWR, 0);
 510         if (fd < 0) {
 511                 perror("parse_iomem - Couldn't open io file");
 512                 goto out;
 513         }
 514
 515         if (fstat64(fd, &buf) < 0) {
 516                 perror("parse_iomem - cannot stat_fd file");
 517                 goto out_close;
 518         }
 519
 520         new = malloc(sizeof(*new));
 521         if (new == NULL) {
 522                 perror("Couldn't allocate iomem_region struct");
 523                 goto out_close;
 524         }
 525
 526         size = (buf.st_size + UM_KERN_PAGE_SIZE) & ~(UM_KERN_PAGE_SIZE - 1);
 527
 528         *new = ((struct iomem_region) { .next           = iomem_regions,
 529                                         .driver         = driver,
 530                                         .fd             = fd,
 531                                         .size           = size,
 532                                         .phys           = 0,
 533                                         .virt           = 0 });
 534         iomem_regions = new;
 535         iomem_size += new->size + UM_KERN_PAGE_SIZE;
 536
 537         return 0;
 538  out_close:
 539         close(fd);
 540  out:
 541         return 1;
 542 }