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