arch/um/os-Linux/start_up.c

   1 /*
   2  * Copyright (C) 2000, 2001, 2002 Jeff Dike (jdike@karaya.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <stdio.h>
   7 #include <stddef.h>
   8 #include <stdarg.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11 #include <unistd.h>
  12 #include <signal.h>
  13 #include <sched.h>
  14 #include <fcntl.h>
  15 #include <errno.h>
  16 #include <setjmp.h>
  17 #include <sys/time.h>
  18 #include <sys/wait.h>
  19 #include <sys/mman.h>
  20 #include <asm/unistd.h>
  21 #include <asm/page.h>
  22 #include <sys/types.h>
  23 #include "user_util.h"
  24 #include "kern_util.h"
  25 #include "user.h"
  26 #include "signal_kern.h"
  27 #include "signal_user.h"
  28 #include "sysdep/ptrace.h"
  29 #include "sysdep/sigcontext.h"
  30 #include "irq_user.h"
  31 #include "ptrace_user.h"
  32 #include "mem_user.h"
  33 #include "time_user.h"
  34 #include "init.h"
  35 #include "os.h"
  36 #include "uml-config.h"
  37 #include "choose-mode.h"
  38 #include "mode.h"
  39 #include "tempfile.h"
  40 #include "kern_constants.h"
  41
  42 #ifdef UML_CONFIG_MODE_SKAS
  43 #include "skas.h"
  44 #include "skas_ptrace.h"
  45 #include "registers.h"
  46 #endif
  47
  48 static int ptrace_child(void *arg)
  49 {
  50         int ret;
  51         int pid = os_getpid(), ppid = getppid();
  52         int sc_result;
  53
  54         if(ptrace(PTRACE_TRACEME, 0, 0, 0) < 0){
  55                 perror("ptrace");
  56                 os_kill_process(pid, 0);
  57         }
  58         os_stop_process(pid);
  59
  60         /*This syscall will be intercepted by the parent. Don't call more than
  61          * once, please.*/
  62         sc_result = os_getpid();
  63
  64         if (sc_result == pid)
  65                 ret = 1; /*Nothing modified by the parent, we are running
  66                            normally.*/
  67         else if (sc_result == ppid)
  68                 ret = 0; /*Expected in check_ptrace and check_sysemu when they
  69                            succeed in modifying the stack frame*/
  70         else
  71                 ret = 2; /*Serious trouble! This could be caused by a bug in
  72                            host 2.6 SKAS3/2.6 patch before release -V6, together
  73                            with a bug in the UML code itself.*/
  74         _exit(ret);
  75 }
  76
  77 static int start_ptraced_child(void **stack_out)
  78 {
  79         void *stack;
  80         unsigned long sp;
  81         int pid, n, status;
  82
  83         stack = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
  84                      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  85         if(stack == MAP_FAILED)
  86                 panic("check_ptrace : mmap failed, errno = %d", errno);
  87         sp = (unsigned long) stack + PAGE_SIZE - sizeof(void *);
  88         pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL);
  89         if(pid < 0)
  90                 panic("start_ptraced_child : clone failed, errno = %d", errno);
  91         CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
  92         if(n < 0)
  93                 panic("check_ptrace : clone failed, errno = %d", errno);
  94         if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
  95                 panic("check_ptrace : expected SIGSTOP, got status = %d",
  96                       status);
  97
  98         *stack_out = stack;
  99         return(pid);
 100 }
 101
 102 /* When testing for SYSEMU support, if it is one of the broken versions, we
 103  * must just avoid using sysemu, not panic, but only if SYSEMU features are
 104  * broken.
 105  * So only for SYSEMU features we test mustpanic, while normal host features
 106  * must work anyway!
 107  */
 108 static int stop_ptraced_child(int pid, void *stack, int exitcode,
 109                               int mustpanic)
 110 {
 111         int status, n, ret = 0;
 112
 113         if(ptrace(PTRACE_CONT, pid, 0, 0) < 0)
 114                 panic("check_ptrace : ptrace failed, errno = %d", errno);
 115         CATCH_EINTR(n = waitpid(pid, &status, 0));
 116         if(!WIFEXITED(status) || (WEXITSTATUS(status) != exitcode)) {
 117                 int exit_with = WEXITSTATUS(status);
 118                 if (exit_with == 2)
 119                         printk("check_ptrace : child exited with status 2. "
 120                                "Serious trouble happening! Try updating your "
 121                                "host skas patch!\nDisabling SYSEMU support.");
 122                 printk("check_ptrace : child exited with exitcode %d, while "
 123                       "expecting %d; status 0x%x", exit_with,
 124                       exitcode, status);
 125                 if (mustpanic)
 126                         panic("\n");
 127                 else
 128                         printk("\n");
 129                 ret = -1;
 130         }
 131
 132         if(munmap(stack, PAGE_SIZE) < 0)
 133                 panic("check_ptrace : munmap failed, errno = %d", errno);
 134         return ret;
 135 }
 136
 137 int ptrace_faultinfo = 1;
 138 int ptrace_ldt = 1;
 139 int proc_mm = 1;
 140 int skas_needs_stub = 0;
 141
 142 static int __init skas0_cmd_param(char *str, int* add)
 143 {
 144         ptrace_faultinfo = proc_mm = 0;
 145         return 0;
 146 }
 147
 148 /* The two __uml_setup would conflict, without this stupid alias. */
 149
 150 static int __init mode_skas0_cmd_param(char *str, int* add)
 151         __attribute__((alias("skas0_cmd_param")));
 152
 153 __uml_setup("skas0", skas0_cmd_param,
 154                 "skas0\n"
 155                 "    Disables SKAS3 usage, so that SKAS0 is used, unless \n"
 156                 "    you specify mode=tt.\n\n");
 157
 158 __uml_setup("mode=skas0", mode_skas0_cmd_param,
 159                 "mode=skas0\n"
 160                 "    Disables SKAS3 usage, so that SKAS0 is used, unless you \n"
 161                 "    specify mode=tt. Note that this was recently added - on \n"
 162                 "    older kernels you must use simply \"skas0\".\n\n");
 163
 164 static int force_sysemu_disabled = 0;
 165
 166 static int __init nosysemu_cmd_param(char *str, int* add)
 167 {
 168         force_sysemu_disabled = 1;
 169         return 0;
 170 }
 171
 172 __uml_setup("nosysemu", nosysemu_cmd_param,
 173 "nosysemu\n"
 174 "    Turns off syscall emulation patch for ptrace (SYSEMU) on.\n"
 175 "    SYSEMU is a performance-patch introduced by Laurent Vivier. It changes\n"
 176 "    behaviour of ptrace() and helps reducing host context switch rate.\n"
 177 "    To make it working, you need a kernel patch for your host, too.\n"
 178 "    See http://perso.wanadoo.fr/laurent.vivier/UML/ for further \n"
 179 "    information.\n\n");
 180
 181 static void __init check_sysemu(void)
 182 {
 183         void *stack;
 184         int pid, n, status, count=0;
 185
 186         printk("Checking syscall emulation patch for ptrace...");
 187         sysemu_supported = 0;
 188         pid = start_ptraced_child(&stack);
 189
 190         if(ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
 191                 goto fail;
 192
 193         CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 194         if (n < 0)
 195                 panic("check_sysemu : wait failed, errno = %d", errno);
 196         if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
 197                 panic("check_sysemu : expected SIGTRAP, "
 198                       "got status = %d", status);
 199
 200         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
 201                    os_getpid());
 202         if(n < 0)
 203                 panic("check_sysemu : failed to modify system "
 204                       "call return, errno = %d", errno);
 205
 206         if (stop_ptraced_child(pid, stack, 0, 0) < 0)
 207                 goto fail_stopped;
 208
 209         sysemu_supported = 1;
 210         printk("OK\n");
 211         set_using_sysemu(!force_sysemu_disabled);
 212
 213         printk("Checking advanced syscall emulation patch for ptrace...");
 214         pid = start_ptraced_child(&stack);
 215
 216         if(ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
 217                   (void *) PTRACE_O_TRACESYSGOOD) < 0)
 218                 panic("check_ptrace: PTRACE_OLDSETOPTIONS failed, errno = %d",
 219                       errno);
 220
 221         while(1){
 222                 count++;
 223                 if(ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
 224                         goto fail;
 225                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 226                 if(n < 0)
 227                         panic("check_ptrace : wait failed, errno = %d", errno);
 228                 if(WIFSTOPPED(status) && (WSTOPSIG(status) == (SIGTRAP|0x80))){
 229                         if (!count)
 230                                 panic("check_ptrace : SYSEMU_SINGLESTEP "
 231                                       "doesn't singlestep");
 232                         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
 233                                    os_getpid());
 234                         if(n < 0)
 235                                 panic("check_sysemu : failed to modify system "
 236                                       "call return, errno = %d", errno);
 237                         break;
 238                 }
 239                 else if(WIFSTOPPED(status) && (WSTOPSIG(status) == SIGTRAP))
 240                         count++;
 241                 else
 242                         panic("check_ptrace : expected SIGTRAP or "
 243                               "(SIGTRAP|0x80), got status = %d", status);
 244         }
 245         if (stop_ptraced_child(pid, stack, 0, 0) < 0)
 246                 goto fail_stopped;
 247
 248         sysemu_supported = 2;
 249         printk("OK\n");
 250
 251         if ( !force_sysemu_disabled )
 252                 set_using_sysemu(sysemu_supported);
 253         return;
 254
 255 fail:
 256         stop_ptraced_child(pid, stack, 1, 0);
 257 fail_stopped:
 258         printk("missing\n");
 259 }
 260
 261 static void __init check_ptrace(void)
 262 {
 263         void *stack;
 264         int pid, syscall, n, status;
 265
 266         printk("Checking that ptrace can change system call numbers...");
 267         pid = start_ptraced_child(&stack);
 268
 269         if(ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
 270                 panic("check_ptrace: PTRACE_OLDSETOPTIONS failed, errno = %d", errno);
 271
 272         while(1){
 273                 if(ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)
 274                         panic("check_ptrace : ptrace failed, errno = %d",
 275                               errno);
 276                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 277                 if(n < 0)
 278                         panic("check_ptrace : wait failed, errno = %d", errno);
 279                 if(!WIFSTOPPED(status) || (WSTOPSIG(status) != (SIGTRAP|0x80)))
 280                         panic("check_ptrace : expected (SIGTRAP|0x80), "
 281                               "got status = %d", status);
 282
 283                 syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
 284                                  0);
 285                 if(syscall == __NR_getpid){
 286                         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
 287                                    __NR_getppid);
 288                         if(n < 0)
 289                                 panic("check_ptrace : failed to modify system "
 290                                       "call, errno = %d", errno);
 291                         break;
 292                 }
 293         }
 294         stop_ptraced_child(pid, stack, 0, 1);
 295         printk("OK\n");
 296         check_sysemu();
 297 }
 298
 299 extern int create_tmp_file(unsigned long long len);
 300
 301 static void check_tmpexec(void)
 302 {
 303         void *addr;
 304         int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
 305
 306         addr = mmap(NULL, UM_KERN_PAGE_SIZE,
 307                     PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
 308         printf("Checking PROT_EXEC mmap in /tmp...");
 309         fflush(stdout);
 310         if(addr == MAP_FAILED){
 311                 err = errno;
 312                 perror("failed");
 313                 if(err == EPERM)
 314                         printf("/tmp must be not mounted noexec\n");
 315                 exit(1);
 316         }
 317         printf("OK\n");
 318         munmap(addr, UM_KERN_PAGE_SIZE);
 319
 320         close(fd);
 321 }
 322
 323 void os_early_checks(void)
 324 {
 325         check_ptrace();
 326
 327         /* Need to check this early because mmapping happens before the
 328          * kernel is running.
 329          */
 330         check_tmpexec();
 331 }
 332
 333 static int __init noprocmm_cmd_param(char *str, int* add)
 334 {
 335         proc_mm = 0;
 336         return 0;
 337 }
 338
 339 __uml_setup("noprocmm", noprocmm_cmd_param,
 340 "noprocmm\n"
 341 "    Turns off usage of /proc/mm, even if host supports it.\n"
 342 "    To support /proc/mm, the host needs to be patched using\n"
 343 "    the current skas3 patch.\n\n");
 344
 345 static int __init noptracefaultinfo_cmd_param(char *str, int* add)
 346 {
 347         ptrace_faultinfo = 0;
 348         return 0;
 349 }
 350
 351 __uml_setup("noptracefaultinfo", noptracefaultinfo_cmd_param,
 352 "noptracefaultinfo\n"
 353 "    Turns off usage of PTRACE_FAULTINFO, even if host supports\n"
 354 "    it. To support PTRACE_FAULTINFO, the host needs to be patched\n"
 355 "    using the current skas3 patch.\n\n");
 356
 357 static int __init noptraceldt_cmd_param(char *str, int* add)
 358 {
 359         ptrace_ldt = 0;
 360         return 0;
 361 }
 362
 363 __uml_setup("noptraceldt", noptraceldt_cmd_param,
 364 "noptraceldt\n"
 365 "    Turns off usage of PTRACE_LDT, even if host supports it.\n"
 366 "    To support PTRACE_LDT, the host needs to be patched using\n"
 367 "    the current skas3 patch.\n\n");
 368
 369 #ifdef UML_CONFIG_MODE_SKAS
 370 static inline void check_skas3_ptrace_faultinfo(void)
 371 {
 372         struct ptrace_faultinfo fi;
 373         void *stack;
 374         int pid, n;
 375
 376         printf("  - PTRACE_FAULTINFO...");
 377         pid = start_ptraced_child(&stack);
 378
 379         n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
 380         if (n < 0) {
 381                 ptrace_faultinfo = 0;
 382                 if(errno == EIO)
 383                         printf("not found\n");
 384                 else
 385                         perror("not found");
 386         }
 387         else {
 388                 if (!ptrace_faultinfo)
 389                         printf("found but disabled on command line\n");
 390                 else
 391                         printf("found\n");
 392         }
 393
 394         init_registers(pid);
 395         stop_ptraced_child(pid, stack, 1, 1);
 396 }
 397
 398 static inline void check_skas3_ptrace_ldt(void)
 399 {
 400 #ifdef PTRACE_LDT
 401         void *stack;
 402         int pid, n;
 403         unsigned char ldtbuf[40];
 404         struct ptrace_ldt ldt_op = (struct ptrace_ldt) {
 405                 .func = 2, /* read default ldt */
 406                 .ptr = ldtbuf,
 407                 .bytecount = sizeof(ldtbuf)};
 408
 409         printf("  - PTRACE_LDT...");
 410         pid = start_ptraced_child(&stack);
 411
 412         n = ptrace(PTRACE_LDT, pid, 0, (unsigned long) &ldt_op);
 413         if (n < 0) {
 414                 if(errno == EIO)
 415                         printf("not found\n");
 416                 else {
 417                         perror("not found");
 418                 }
 419                 ptrace_ldt = 0;
 420         }
 421         else {
 422                 if(ptrace_ldt)
 423                         printf("found\n");
 424                 else
 425                         printf("found, but use is disabled\n");
 426         }
 427
 428         stop_ptraced_child(pid, stack, 1, 1);
 429 #else
 430         /* PTRACE_LDT might be disabled via cmdline option.
 431          * We want to override this, else we might use the stub
 432          * without real need
 433          */
 434         ptrace_ldt = 1;
 435 #endif
 436 }
 437
 438 static inline void check_skas3_proc_mm(void)
 439 {
 440         printf("  - /proc/mm...");
 441         if (os_access("/proc/mm", OS_ACC_W_OK) < 0) {
 442                 proc_mm = 0;
 443                 printf("not found\n");
 444         }
 445         else {
 446                 if (!proc_mm)
 447                         printf("found but disabled on command line\n");
 448                 else
 449                         printf("found\n");
 450         }
 451 }
 452
 453 int can_do_skas(void)
 454 {
 455         printf("Checking for the skas3 patch in the host:\n");
 456
 457         check_skas3_proc_mm();
 458         check_skas3_ptrace_faultinfo();
 459         check_skas3_ptrace_ldt();
 460
 461         if(!proc_mm || !ptrace_faultinfo || !ptrace_ldt)
 462                 skas_needs_stub = 1;
 463
 464         return 1;
 465 }
 466 #else
 467 int can_do_skas(void)
 468 {
 469         return(0);
 470 }
 471 #endif
 472
 473 int have_devanon = 0;
 474
 475 void check_devanon(void)
 476 {
 477         int fd;
 478
 479         printk("Checking for /dev/anon on the host...");
 480         fd = open("/dev/anon", O_RDWR);
 481         if(fd < 0){
 482                 printk("Not available (open failed with errno %d)\n", errno);
 483                 return;
 484         }
 485
 486         printk("OK\n");
 487         have_devanon = 1;
 488 }
 489
 490 int __init parse_iomem(char *str, int *add)
 491 {
 492         struct iomem_region *new;
 493         struct uml_stat buf;
 494         char *file, *driver;
 495         int fd, err, size;
 496
 497         driver = str;
 498         file = strchr(str,',');
 499         if(file == NULL){
 500                 printf("parse_iomem : failed to parse iomem\n");
 501                 goto out;
 502         }
 503         *file = '\0';
 504         file++;
 505         fd = os_open_file(file, of_rdwr(OPENFLAGS()), 0);
 506         if(fd < 0){
 507                 os_print_error(fd, "parse_iomem - Couldn't open io file");
 508                 goto out;
 509         }
 510
 511         err = os_stat_fd(fd, &buf);
 512         if(err < 0){
 513                 os_print_error(err, "parse_iomem - cannot stat_fd file");
 514                 goto out_close;
 515         }
 516
 517         new = malloc(sizeof(*new));
 518         if(new == NULL){
 519                 perror("Couldn't allocate iomem_region struct");
 520                 goto out_close;
 521         }
 522
 523         size = (buf.ust_size + UM_KERN_PAGE_SIZE) & ~(UM_KERN_PAGE_SIZE - 1);
 524
 525         *new = ((struct iomem_region) { .next           = iomem_regions,
 526                                         .driver         = driver,
 527                                         .fd             = fd,
 528                                         .size           = size,
 529                                         .phys           = 0,
 530                                         .virt           = 0 });
 531         iomem_regions = new;
 532         iomem_size += new->size + UM_KERN_PAGE_SIZE;
 533
 534         return(0);
 535  out_close:
 536         os_close_file(fd);
 537  out:
 538         return(1);
 539 }
 540