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