arch/um/kernel/process.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 <unistd.h>
   8 #include <signal.h>
   9 #include <sched.h>
  10 #include <errno.h>
  11 #include <stdarg.h>
  12 #include <stdlib.h>
  13 #include <setjmp.h>
  14 #include <sys/time.h>
  15 #include <sys/wait.h>
  16 #include <sys/mman.h>
  17 #include <asm/unistd.h>
  18 #include <asm/page.h>
  19 #include "user_util.h"
  20 #include "kern_util.h"
  21 #include "user.h"
  22 #include "process.h"
  23 #include "signal_kern.h"
  24 #include "signal_user.h"
  25 #include "sysdep/ptrace.h"
  26 #include "sysdep/sigcontext.h"
  27 #include "irq_user.h"
  28 #include "ptrace_user.h"
  29 #include "time_user.h"
  30 #include "init.h"
  31 #include "os.h"
  32 #include "uml-config.h"
  33 #include "ptrace_user.h"
  34 #include "choose-mode.h"
  35 #include "mode.h"
  36 #ifdef UML_CONFIG_MODE_SKAS
  37 #include "skas.h"
  38 #include "skas_ptrace.h"
  39 #include "registers.h"
  40 #endif
  41
  42 void init_new_thread_stack(void *sig_stack, void (*usr1_handler)(int))
  43 {
  44         int flags = 0, pages;
  45
  46         if(sig_stack != NULL){
  47                 pages = (1 << UML_CONFIG_KERNEL_STACK_ORDER);
  48                 set_sigstack(sig_stack, pages * page_size());
  49                 flags = SA_ONSTACK;
  50         }
  51         if(usr1_handler) set_handler(SIGUSR1, usr1_handler, flags, -1);
  52 }
  53
  54 void init_new_thread_signals(int altstack)
  55 {
  56         int flags = altstack ? SA_ONSTACK : 0;
  57
  58         set_handler(SIGSEGV, (__sighandler_t) sig_handler, flags,
  59                     SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
  60         set_handler(SIGTRAP, (__sighandler_t) sig_handler, flags,
  61                     SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
  62         set_handler(SIGFPE, (__sighandler_t) sig_handler, flags,
  63                     SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
  64         set_handler(SIGILL, (__sighandler_t) sig_handler, flags,
  65                     SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
  66         set_handler(SIGBUS, (__sighandler_t) sig_handler, flags,
  67                     SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
  68         set_handler(SIGWINCH, (__sighandler_t) sig_handler, flags,
  69                     SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
  70         set_handler(SIGUSR2, (__sighandler_t) sig_handler,
  71                     flags, SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
  72         signal(SIGHUP, SIG_IGN);
  73
  74         init_irq_signals(altstack);
  75 }
  76
  77 struct tramp {
  78         int (*tramp)(void *);
  79         void *tramp_data;
  80         unsigned long temp_stack;
  81         int flags;
  82         int pid;
  83 };
  84
  85 /* See above for why sigkill is here */
  86
  87 int sigkill = SIGKILL;
  88
  89 int outer_tramp(void *arg)
  90 {
  91         struct tramp *t;
  92         int sig = sigkill;
  93
  94         t = arg;
  95         t->pid = clone(t->tramp, (void *) t->temp_stack + page_size()/2,
  96                        t->flags, t->tramp_data);
  97         if(t->pid > 0) wait_for_stop(t->pid, SIGSTOP, PTRACE_CONT, NULL);
  98         kill(os_getpid(), sig);
  99         _exit(0);
 100 }
 101
 102 int start_fork_tramp(void *thread_arg, unsigned long temp_stack,
 103                      int clone_flags, int (*tramp)(void *))
 104 {
 105         struct tramp arg;
 106         unsigned long sp;
 107         int new_pid, status, err;
 108
 109         /* The trampoline will run on the temporary stack */
 110         sp = stack_sp(temp_stack);
 111
 112         clone_flags |= CLONE_FILES | SIGCHLD;
 113
 114         arg.tramp = tramp;
 115         arg.tramp_data = thread_arg;
 116         arg.temp_stack = temp_stack;
 117         arg.flags = clone_flags;
 118
 119         /* Start the process and wait for it to kill itself */
 120         new_pid = clone(outer_tramp, (void *) sp, clone_flags, &arg);
 121         if(new_pid < 0)
 122                 return(new_pid);
 123
 124         CATCH_EINTR(err = waitpid(new_pid, &status, 0));
 125         if(err < 0)
 126                 panic("Waiting for outer trampoline failed - errno = %d",
 127                       errno);
 128
 129         if(!WIFSIGNALED(status) || (WTERMSIG(status) != SIGKILL))
 130                 panic("outer trampoline didn't exit with SIGKILL, "
 131                       "status = %d", status);
 132
 133         return(arg.pid);
 134 }
 135
 136 static int ptrace_child(void *arg)
 137 {
 138         int ret;
 139         int pid = os_getpid(), ppid = getppid();
 140         int sc_result;
 141
 142         if(ptrace(PTRACE_TRACEME, 0, 0, 0) < 0){
 143                 perror("ptrace");
 144                 os_kill_process(pid, 0);
 145         }
 146         os_stop_process(pid);
 147
 148         /*This syscall will be intercepted by the parent. Don't call more than
 149          * once, please.*/
 150         sc_result = os_getpid();
 151
 152         if (sc_result == pid)
 153                 ret = 1; /*Nothing modified by the parent, we are running
 154                            normally.*/
 155         else if (sc_result == ppid)
 156                 ret = 0; /*Expected in check_ptrace and check_sysemu when they
 157                            succeed in modifying the stack frame*/
 158         else
 159                 ret = 2; /*Serious trouble! This could be caused by a bug in
 160                            host 2.6 SKAS3/2.6 patch before release -V6, together
 161                            with a bug in the UML code itself.*/
 162         _exit(ret);
 163 }
 164
 165 static int start_ptraced_child(void **stack_out)
 166 {
 167         void *stack;
 168         unsigned long sp;
 169         int pid, n, status;
 170
 171         stack = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
 172                      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 173         if(stack == MAP_FAILED)
 174                 panic("check_ptrace : mmap failed, errno = %d", errno);
 175         sp = (unsigned long) stack + PAGE_SIZE - sizeof(void *);
 176         pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL);
 177         if(pid < 0)
 178                 panic("check_ptrace : clone failed, errno = %d", errno);
 179         CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 180         if(n < 0)
 181                 panic("check_ptrace : wait failed, errno = %d", errno);
 182         if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
 183                 panic("check_ptrace : expected SIGSTOP, got status = %d",
 184                       status);
 185
 186         *stack_out = stack;
 187         return(pid);
 188 }
 189
 190 /* When testing for SYSEMU support, if it is one of the broken versions, we must
 191  * just avoid using sysemu, not panic, but only if SYSEMU features are broken.
 192  * So only for SYSEMU features we test mustpanic, while normal host features
 193  * must work anyway!*/
 194 static int stop_ptraced_child(int pid, void *stack, int exitcode, int mustpanic)
 195 {
 196         int status, n, ret = 0;
 197
 198         if(ptrace(PTRACE_CONT, pid, 0, 0) < 0)
 199                 panic("check_ptrace : ptrace failed, errno = %d", errno);
 200         CATCH_EINTR(n = waitpid(pid, &status, 0));
 201         if(!WIFEXITED(status) || (WEXITSTATUS(status) != exitcode)) {
 202                 int exit_with = WEXITSTATUS(status);
 203                 if (exit_with == 2)
 204                         printk("check_ptrace : child exited with status 2. "
 205                                "Serious trouble happening! Try updating your "
 206                                "host skas patch!\nDisabling SYSEMU support.");
 207                 printk("check_ptrace : child exited with exitcode %d, while "
 208                       "expecting %d; status 0x%x", exit_with,
 209                       exitcode, status);
 210                 if (mustpanic)
 211                         panic("\n");
 212                 else
 213                         printk("\n");
 214                 ret = -1;
 215         }
 216
 217         if(munmap(stack, PAGE_SIZE) < 0)
 218                 panic("check_ptrace : munmap failed, errno = %d", errno);
 219         return ret;
 220 }
 221
 222 static int force_sysemu_disabled = 0;
 223
 224 static int __init nosysemu_cmd_param(char *str, int* add)
 225 {
 226         force_sysemu_disabled = 1;
 227         return 0;
 228 }
 229
 230 __uml_setup("nosysemu", nosysemu_cmd_param,
 231                 "nosysemu\n"
 232                 "    Turns off syscall emulation patch for ptrace (SYSEMU) on.\n"
 233                 "    SYSEMU is a performance-patch introduced by Laurent Vivier. It changes\n"
 234                 "    behaviour of ptrace() and helps reducing host context switch rate.\n"
 235                 "    To make it working, you need a kernel patch for your host, too.\n"
 236                 "    See http://perso.wanadoo.fr/laurent.vivier/UML/ for further information.\n\n");
 237
 238 static void __init check_sysemu(void)
 239 {
 240         void *stack;
 241         int pid, syscall, n, status, count=0;
 242
 243         printk("Checking syscall emulation patch for ptrace...");
 244         sysemu_supported = 0;
 245         pid = start_ptraced_child(&stack);
 246
 247         if(ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
 248                 goto fail;
 249
 250         CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 251         if (n < 0)
 252                 panic("check_sysemu : wait failed, errno = %d", errno);
 253         if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
 254                 panic("check_sysemu : expected SIGTRAP, "
 255                       "got status = %d", status);
 256
 257         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
 258                    os_getpid());
 259         if(n < 0)
 260                 panic("check_sysemu : failed to modify system "
 261                       "call return, errno = %d", errno);
 262
 263         if (stop_ptraced_child(pid, stack, 0, 0) < 0)
 264                 goto fail_stopped;
 265
 266         sysemu_supported = 1;
 267         printk("OK\n");
 268         set_using_sysemu(!force_sysemu_disabled);
 269
 270         printk("Checking advanced syscall emulation patch for ptrace...");
 271         pid = start_ptraced_child(&stack);
 272         while(1){
 273                 count++;
 274                 if(ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
 275                         goto fail;
 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))
 280                         panic("check_ptrace : expected (SIGTRAP|SYSCALL_TRAP), "
 281                               "got status = %d", status);
 282
 283                 syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
 284                                  0);
 285                 if(syscall == __NR_getpid){
 286                         if (!count)
 287                                 panic("check_ptrace : SYSEMU_SINGLESTEP doesn't singlestep");
 288                         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
 289                                    os_getpid());
 290                         if(n < 0)
 291                                 panic("check_sysemu : failed to modify system "
 292                                       "call return, errno = %d", errno);
 293                         break;
 294                 }
 295         }
 296         if (stop_ptraced_child(pid, stack, 0, 0) < 0)
 297                 goto fail_stopped;
 298
 299         sysemu_supported = 2;
 300         printk("OK\n");
 301
 302         if ( !force_sysemu_disabled )
 303                 set_using_sysemu(sysemu_supported);
 304         return;
 305
 306 fail:
 307         stop_ptraced_child(pid, stack, 1, 0);
 308 fail_stopped:
 309         printk("missing\n");
 310 }
 311
 312 void __init check_ptrace(void)
 313 {
 314         void *stack;
 315         int pid, syscall, n, status;
 316
 317         printk("Checking that ptrace can change system call numbers...");
 318         pid = start_ptraced_child(&stack);
 319
 320         if (ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
 321                 panic("check_ptrace: PTRACE_SETOPTIONS failed, errno = %d", errno);
 322
 323         while(1){
 324                 if(ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)
 325                         panic("check_ptrace : ptrace failed, errno = %d",
 326                               errno);
 327                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 328                 if(n < 0)
 329                         panic("check_ptrace : wait failed, errno = %d", errno);
 330                 if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP + 0x80))
 331                         panic("check_ptrace : expected SIGTRAP + 0x80, "
 332                               "got status = %d", status);
 333
 334                 syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
 335                                  0);
 336                 if(syscall == __NR_getpid){
 337                         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
 338                                    __NR_getppid);
 339                         if(n < 0)
 340                                 panic("check_ptrace : failed to modify system "
 341                                       "call, errno = %d", errno);
 342                         break;
 343                 }
 344         }
 345         stop_ptraced_child(pid, stack, 0, 1);
 346         printk("OK\n");
 347         check_sysemu();
 348 }
 349
 350 int run_kernel_thread(int (*fn)(void *), void *arg, void **jmp_ptr)
 351 {
 352         sigjmp_buf buf;
 353         int n;
 354
 355         *jmp_ptr = &buf;
 356         n = sigsetjmp(buf, 1);
 357         if(n != 0)
 358                 return(n);
 359         (*fn)(arg);
 360         return(0);
 361 }
 362
 363 void forward_pending_sigio(int target)
 364 {
 365         sigset_t sigs;
 366
 367         if(sigpending(&sigs))
 368                 panic("forward_pending_sigio : sigpending failed");
 369         if(sigismember(&sigs, SIGIO))
 370                 kill(target, SIGIO);
 371 }
 372
 373 #ifdef UML_CONFIG_MODE_SKAS
 374 static inline int check_skas3_ptrace_support(void)
 375 {
 376         struct ptrace_faultinfo fi;
 377         void *stack;
 378         int pid, n, ret = 1;
 379
 380         printf("Checking for the skas3 patch in the host...");
 381         pid = start_ptraced_child(&stack);
 382
 383         n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
 384         if (n < 0) {
 385                 if(errno == EIO)
 386                         printf("not found\n");
 387                 else {
 388                         perror("not found");
 389                 }
 390                 ret = 0;
 391         } else {
 392                 printf("found\n");
 393         }
 394
 395         init_registers(pid);
 396         stop_ptraced_child(pid, stack, 1, 1);
 397
 398         return(ret);
 399 }
 400
 401 int can_do_skas(void)
 402 {
 403         int ret = 1;
 404
 405         printf("Checking for /proc/mm...");
 406         if (os_access("/proc/mm", OS_ACC_W_OK) < 0) {
 407                 printf("not found\n");
 408                 ret = 0;
 409                 goto out;
 410         } else {
 411                 printf("found\n");
 412         }
 413
 414         ret = check_skas3_ptrace_support();
 415 out:
 416         return ret;
 417 }
 418 #else
 419 int can_do_skas(void)
 420 {
 421         return(0);
 422 }
 423 #endif