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 proc_mm = 1;
 139
 140 static int __init skas0_cmd_param(char *str, int* add)
 141 {
 142         ptrace_faultinfo = proc_mm = 0;
 143         return 0;
 144 }
 145
 146 /* The two __uml_setup would conflict, without this stupid alias. */
 147
 148 static int __init mode_skas0_cmd_param(char *str, int* add)
 149         __attribute__((alias("skas0_cmd_param")));
 150
 151 __uml_setup("skas0", skas0_cmd_param,
 152                 "skas0\n"
 153                 "    Disables SKAS3 usage, so that SKAS0 is used, unless \n"
 154                 "    you specify mode=tt.\n\n");
 155
 156 __uml_setup("mode=skas0", mode_skas0_cmd_param,
 157                 "mode=skas0\n"
 158                 "    Disables SKAS3 usage, so that SKAS0 is used, unless you \n"
 159                 "    specify mode=tt. Note that this was recently added - on \n"
 160                 "    older kernels you must use simply \"skas0\".\n\n");
 161
 162 static int force_sysemu_disabled = 0;
 163
 164 static int __init nosysemu_cmd_param(char *str, int* add)
 165 {
 166         force_sysemu_disabled = 1;
 167         return 0;
 168 }
 169
 170 __uml_setup("nosysemu", nosysemu_cmd_param,
 171 "nosysemu\n"
 172 "    Turns off syscall emulation patch for ptrace (SYSEMU) on.\n"
 173 "    SYSEMU is a performance-patch introduced by Laurent Vivier. It changes\n"
 174 "    behaviour of ptrace() and helps reducing host context switch rate.\n"
 175 "    To make it working, you need a kernel patch for your host, too.\n"
 176 "    See http://perso.wanadoo.fr/laurent.vivier/UML/ for further \n"
 177 "    information.\n\n");
 178
 179 static void __init check_sysemu(void)
 180 {
 181         void *stack;
 182         int pid, n, status, count=0;
 183
 184         printk("Checking syscall emulation patch for ptrace...");
 185         sysemu_supported = 0;
 186         pid = start_ptraced_child(&stack);
 187
 188         if(ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
 189                 goto fail;
 190
 191         CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 192         if (n < 0)
 193                 panic("check_sysemu : wait failed, errno = %d", errno);
 194         if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
 195                 panic("check_sysemu : expected SIGTRAP, "
 196                       "got status = %d", status);
 197
 198         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
 199                    os_getpid());
 200         if(n < 0)
 201                 panic("check_sysemu : failed to modify system "
 202                       "call return, errno = %d", errno);
 203
 204         if (stop_ptraced_child(pid, stack, 0, 0) < 0)
 205                 goto fail_stopped;
 206
 207         sysemu_supported = 1;
 208         printk("OK\n");
 209         set_using_sysemu(!force_sysemu_disabled);
 210
 211         printk("Checking advanced syscall emulation patch for ptrace...");
 212         pid = start_ptraced_child(&stack);
 213
 214         if(ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
 215                   (void *) PTRACE_O_TRACESYSGOOD) < 0)
 216                 panic("check_ptrace: PTRACE_OLDSETOPTIONS failed, errno = %d",
 217                       errno);
 218
 219         while(1){
 220                 count++;
 221                 if(ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
 222                         goto fail;
 223                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 224                 if(n < 0)
 225                         panic("check_ptrace : wait failed, errno = %d", errno);
 226                 if(WIFSTOPPED(status) && (WSTOPSIG(status) == (SIGTRAP|0x80))){
 227                         if (!count)
 228                                 panic("check_ptrace : SYSEMU_SINGLESTEP "
 229                                       "doesn't singlestep");
 230                         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
 231                                    os_getpid());
 232                         if(n < 0)
 233                                 panic("check_sysemu : failed to modify system "
 234                                       "call return, errno = %d", errno);
 235                         break;
 236                 }
 237                 else if(WIFSTOPPED(status) && (WSTOPSIG(status) == SIGTRAP))
 238                         count++;
 239                 else
 240                         panic("check_ptrace : expected SIGTRAP or "
 241                               "(SIGTRAP|0x80), got status = %d", status);
 242         }
 243         if (stop_ptraced_child(pid, stack, 0, 0) < 0)
 244                 goto fail_stopped;
 245
 246         sysemu_supported = 2;
 247         printk("OK\n");
 248
 249         if ( !force_sysemu_disabled )
 250                 set_using_sysemu(sysemu_supported);
 251         return;
 252
 253 fail:
 254         stop_ptraced_child(pid, stack, 1, 0);
 255 fail_stopped:
 256         printk("missing\n");
 257 }
 258
 259 static void __init check_ptrace(void)
 260 {
 261         void *stack;
 262         int pid, syscall, n, status;
 263
 264         printk("Checking that ptrace can change system call numbers...");
 265         pid = start_ptraced_child(&stack);
 266
 267         if(ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
 268                 panic("check_ptrace: PTRACE_OLDSETOPTIONS failed, errno = %d", errno);
 269
 270         while(1){
 271                 if(ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)
 272                         panic("check_ptrace : ptrace failed, errno = %d",
 273                               errno);
 274                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 275                 if(n < 0)
 276                         panic("check_ptrace : wait failed, errno = %d", errno);
 277                 if(!WIFSTOPPED(status) || (WSTOPSIG(status) != (SIGTRAP|0x80)))
 278                         panic("check_ptrace : expected (SIGTRAP|0x80), "
 279                               "got status = %d", status);
 280
 281                 syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
 282                                  0);
 283                 if(syscall == __NR_getpid){
 284                         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
 285                                    __NR_getppid);
 286                         if(n < 0)
 287                                 panic("check_ptrace : failed to modify system "
 288                                       "call, errno = %d", errno);
 289                         break;
 290                 }
 291         }
 292         stop_ptraced_child(pid, stack, 0, 1);
 293         printk("OK\n");
 294         check_sysemu();
 295 }
 296
 297 extern int create_tmp_file(unsigned long len);
 298
 299 static void check_tmpexec(void)
 300 {
 301         void *addr;
 302         int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
 303
 304         addr = mmap(NULL, UM_KERN_PAGE_SIZE,
 305                     PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
 306         printf("Checking PROT_EXEC mmap in /tmp...");
 307         fflush(stdout);
 308         if(addr == MAP_FAILED){
 309                 err = errno;
 310                 perror("failed");
 311                 if(err == EPERM)
 312                         printf("/tmp must be not mounted noexec\n");
 313                 exit(1);
 314         }
 315         printf("OK\n");
 316         munmap(addr, UM_KERN_PAGE_SIZE);
 317
 318         close(fd);
 319 }
 320
 321 void os_early_checks(void)
 322 {
 323         check_ptrace();
 324
 325         /* Need to check this early because mmapping happens before the
 326          * kernel is running.
 327          */
 328         check_tmpexec();
 329 }
 330
 331 static int __init noprocmm_cmd_param(char *str, int* add)
 332 {
 333         proc_mm = 0;
 334         return 0;
 335 }
 336
 337 __uml_setup("noprocmm", noprocmm_cmd_param,
 338 "noprocmm\n"
 339 "    Turns off usage of /proc/mm, even if host supports it.\n"
 340 "    To support /proc/mm, the host needs to be patched using\n"
 341 "    the current skas3 patch.\n\n");
 342
 343 static int __init noptracefaultinfo_cmd_param(char *str, int* add)
 344 {
 345         ptrace_faultinfo = 0;
 346         return 0;
 347 }
 348
 349 __uml_setup("noptracefaultinfo", noptracefaultinfo_cmd_param,
 350 "noptracefaultinfo\n"
 351 "    Turns off usage of PTRACE_FAULTINFO, even if host supports\n"
 352 "    it. To support PTRACE_FAULTINFO, the host needs to be patched\n"
 353 "    using the current skas3 patch.\n\n");
 354
 355 #ifdef UML_CONFIG_MODE_SKAS
 356 static inline void check_skas3_ptrace_support(void)
 357 {
 358         struct ptrace_faultinfo fi;
 359         void *stack;
 360         int pid, n;
 361
 362         printf("Checking for the skas3 patch in the host...");
 363         pid = start_ptraced_child(&stack);
 364
 365         n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
 366         if (n < 0) {
 367                 ptrace_faultinfo = 0;
 368                 if(errno == EIO)
 369                         printf("not found\n");
 370                 else
 371                         perror("not found");
 372         }
 373         else {
 374                 if (!ptrace_faultinfo)
 375                         printf("found but disabled on command line\n");
 376                 else
 377                         printf("found\n");
 378         }
 379
 380         init_registers(pid);
 381         stop_ptraced_child(pid, stack, 1, 1);
 382 }
 383
 384 int can_do_skas(void)
 385 {
 386         printf("Checking for /proc/mm...");
 387         if (os_access("/proc/mm", OS_ACC_W_OK) < 0) {
 388                 proc_mm = 0;
 389                 printf("not found\n");
 390         }
 391         else {
 392                 if (!proc_mm)
 393                         printf("found but disabled on command line\n");
 394                 else
 395                         printf("found\n");
 396         }
 397
 398         check_skas3_ptrace_support();
 399         return 1;
 400 }
 401 #else
 402 int can_do_skas(void)
 403 {
 404         return(0);
 405 }
 406 #endif
 407
 408 int have_devanon = 0;
 409
 410 void check_devanon(void)
 411 {
 412         int fd;
 413
 414         printk("Checking for /dev/anon on the host...");
 415         fd = open("/dev/anon", O_RDWR);
 416         if(fd < 0){
 417                 printk("Not available (open failed with errno %d)\n", errno);
 418                 return;
 419         }
 420
 421         printk("OK\n");
 422         have_devanon = 1;
 423 }
 424
 425 int __init parse_iomem(char *str, int *add)
 426 {
 427         struct iomem_region *new;
 428         struct uml_stat buf;
 429         char *file, *driver;
 430         int fd, err, size;
 431
 432         driver = str;
 433         file = strchr(str,',');
 434         if(file == NULL){
 435                 printf("parse_iomem : failed to parse iomem\n");
 436                 goto out;
 437         }
 438         *file = '\0';
 439         file++;
 440         fd = os_open_file(file, of_rdwr(OPENFLAGS()), 0);
 441         if(fd < 0){
 442                 os_print_error(fd, "parse_iomem - Couldn't open io file");
 443                 goto out;
 444         }
 445
 446         err = os_stat_fd(fd, &buf);
 447         if(err < 0){
 448                 os_print_error(err, "parse_iomem - cannot stat_fd file");
 449                 goto out_close;
 450         }
 451
 452         new = malloc(sizeof(*new));
 453         if(new == NULL){
 454                 perror("Couldn't allocate iomem_region struct");
 455                 goto out_close;
 456         }
 457
 458         size = (buf.ust_size + UM_KERN_PAGE_SIZE) & ~(UM_KERN_PAGE_SIZE - 1);
 459
 460         *new = ((struct iomem_region) { .next           = iomem_regions,
 461                                         .driver         = driver,
 462                                         .fd             = fd,
 463                                         .size           = size,
 464                                         .phys           = 0,
 465                                         .virt           = 0 });
 466         iomem_regions = new;
 467         iomem_size += new->size + UM_KERN_PAGE_SIZE;
 468
 469         return(0);
 470  out_close:
 471         os_close_file(fd);
 472  out:
 473         return(1);
 474 }
 475