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 "choose-mode.h"
  34 #include "mode.h"
  35 #include "tempfile.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(SIGUSR2, (__sighandler_t) sig_handler,
  69                     flags, SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
  70         signal(SIGHUP, SIG_IGN);
  71
  72         init_irq_signals(altstack);
  73 }
  74
  75 struct tramp {
  76         int (*tramp)(void *);
  77         void *tramp_data;
  78         unsigned long temp_stack;
  79         int flags;
  80         int pid;
  81 };
  82
  83 /* See above for why sigkill is here */
  84
  85 int sigkill = SIGKILL;
  86
  87 int outer_tramp(void *arg)
  88 {
  89         struct tramp *t;
  90         int sig = sigkill;
  91
  92         t = arg;
  93         t->pid = clone(t->tramp, (void *) t->temp_stack + page_size()/2,
  94                        t->flags, t->tramp_data);
  95         if(t->pid > 0) wait_for_stop(t->pid, SIGSTOP, PTRACE_CONT, NULL);
  96         kill(os_getpid(), sig);
  97         _exit(0);
  98 }
  99
 100 int start_fork_tramp(void *thread_arg, unsigned long temp_stack,
 101                      int clone_flags, int (*tramp)(void *))
 102 {
 103         struct tramp arg;
 104         unsigned long sp;
 105         int new_pid, status, err;
 106
 107         /* The trampoline will run on the temporary stack */
 108         sp = stack_sp(temp_stack);
 109
 110         clone_flags |= CLONE_FILES | SIGCHLD;
 111
 112         arg.tramp = tramp;
 113         arg.tramp_data = thread_arg;
 114         arg.temp_stack = temp_stack;
 115         arg.flags = clone_flags;
 116
 117         /* Start the process and wait for it to kill itself */
 118         new_pid = clone(outer_tramp, (void *) sp, clone_flags, &arg);
 119         if(new_pid < 0)
 120                 return(new_pid);
 121
 122         CATCH_EINTR(err = waitpid(new_pid, &status, 0));
 123         if(err < 0)
 124                 panic("Waiting for outer trampoline failed - errno = %d",
 125                       errno);
 126
 127         if(!WIFSIGNALED(status) || (WTERMSIG(status) != SIGKILL))
 128                 panic("outer trampoline didn't exit with SIGKILL, "
 129                       "status = %d", status);
 130
 131         return(arg.pid);
 132 }
 133
 134 static int ptrace_child(void *arg)
 135 {
 136         int ret;
 137         int pid = os_getpid(), ppid = getppid();
 138         int sc_result;
 139
 140         if(ptrace(PTRACE_TRACEME, 0, 0, 0) < 0){
 141                 perror("ptrace");
 142                 os_kill_process(pid, 0);
 143         }
 144         os_stop_process(pid);
 145
 146         /*This syscall will be intercepted by the parent. Don't call more than
 147          * once, please.*/
 148         sc_result = os_getpid();
 149
 150         if (sc_result == pid)
 151                 ret = 1; /*Nothing modified by the parent, we are running
 152                            normally.*/
 153         else if (sc_result == ppid)
 154                 ret = 0; /*Expected in check_ptrace and check_sysemu when they
 155                            succeed in modifying the stack frame*/
 156         else
 157                 ret = 2; /*Serious trouble! This could be caused by a bug in
 158                            host 2.6 SKAS3/2.6 patch before release -V6, together
 159                            with a bug in the UML code itself.*/
 160         _exit(ret);
 161 }
 162
 163 static int start_ptraced_child(void **stack_out)
 164 {
 165         void *stack;
 166         unsigned long sp;
 167         int pid, n, status;
 168
 169         stack = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
 170                      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 171         if(stack == MAP_FAILED)
 172                 panic("check_ptrace : mmap failed, errno = %d", errno);
 173         sp = (unsigned long) stack + PAGE_SIZE - sizeof(void *);
 174         pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL);
 175         if(pid < 0)
 176                 panic("check_ptrace : clone failed, errno = %d", errno);
 177         CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 178         if(n < 0)
 179                 panic("check_ptrace : wait failed, errno = %d", errno);
 180         if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
 181                 panic("check_ptrace : expected SIGSTOP, got status = %d",
 182                       status);
 183
 184         *stack_out = stack;
 185         return(pid);
 186 }
 187
 188 /* When testing for SYSEMU support, if it is one of the broken versions, we must
 189  * just avoid using sysemu, not panic, but only if SYSEMU features are broken.
 190  * So only for SYSEMU features we test mustpanic, while normal host features
 191  * must work anyway!*/
 192 static int stop_ptraced_child(int pid, void *stack, int exitcode, int mustpanic)
 193 {
 194         int status, n, ret = 0;
 195
 196         if(ptrace(PTRACE_CONT, pid, 0, 0) < 0)
 197                 panic("check_ptrace : ptrace failed, errno = %d", errno);
 198         CATCH_EINTR(n = waitpid(pid, &status, 0));
 199         if(!WIFEXITED(status) || (WEXITSTATUS(status) != exitcode)) {
 200                 int exit_with = WEXITSTATUS(status);
 201                 if (exit_with == 2)
 202                         printk("check_ptrace : child exited with status 2. "
 203                                "Serious trouble happening! Try updating your "
 204                                "host skas patch!\nDisabling SYSEMU support.");
 205                 printk("check_ptrace : child exited with exitcode %d, while "
 206                       "expecting %d; status 0x%x", exit_with,
 207                       exitcode, status);
 208                 if (mustpanic)
 209                         panic("\n");
 210                 else
 211                         printk("\n");
 212                 ret = -1;
 213         }
 214
 215         if(munmap(stack, PAGE_SIZE) < 0)
 216                 panic("check_ptrace : munmap failed, errno = %d", errno);
 217         return ret;
 218 }
 219
 220 static int force_sysemu_disabled = 0;
 221
 222 int ptrace_faultinfo = 1;
 223 int proc_mm = 1;
 224
 225 static int __init skas0_cmd_param(char *str, int* add)
 226 {
 227         ptrace_faultinfo = proc_mm = 0;
 228         return 0;
 229 }
 230
 231 static int __init nosysemu_cmd_param(char *str, int* add)
 232 {
 233         force_sysemu_disabled = 1;
 234         return 0;
 235 }
 236
 237 __uml_setup("skas0", skas0_cmd_param,
 238                 "skas0\n"
 239                 "    Disables SKAS3 usage, so that SKAS0 is used, unless you \n"
 240                 "    specify mode=tt.\n\n");
 241
 242 __uml_setup("nosysemu", nosysemu_cmd_param,
 243                 "nosysemu\n"
 244                 "    Turns off syscall emulation patch for ptrace (SYSEMU) on.\n"
 245                 "    SYSEMU is a performance-patch introduced by Laurent Vivier. It changes\n"
 246                 "    behaviour of ptrace() and helps reducing host context switch rate.\n"
 247                 "    To make it working, you need a kernel patch for your host, too.\n"
 248                 "    See http://perso.wanadoo.fr/laurent.vivier/UML/ for further information.\n\n");
 249
 250 static void __init check_sysemu(void)
 251 {
 252         void *stack;
 253         int pid, syscall, n, status, count=0;
 254
 255         printk("Checking syscall emulation patch for ptrace...");
 256         sysemu_supported = 0;
 257         pid = start_ptraced_child(&stack);
 258
 259         if(ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
 260                 goto fail;
 261
 262         CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 263         if (n < 0)
 264                 panic("check_sysemu : wait failed, errno = %d", errno);
 265         if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
 266                 panic("check_sysemu : expected SIGTRAP, "
 267                       "got status = %d", status);
 268
 269         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
 270                    os_getpid());
 271         if(n < 0)
 272                 panic("check_sysemu : failed to modify system "
 273                       "call return, errno = %d", errno);
 274
 275         if (stop_ptraced_child(pid, stack, 0, 0) < 0)
 276                 goto fail_stopped;
 277
 278         sysemu_supported = 1;
 279         printk("OK\n");
 280         set_using_sysemu(!force_sysemu_disabled);
 281
 282         printk("Checking advanced syscall emulation patch for ptrace...");
 283         pid = start_ptraced_child(&stack);
 284         while(1){
 285                 count++;
 286                 if(ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
 287                         goto fail;
 288                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 289                 if(n < 0)
 290                         panic("check_ptrace : wait failed, errno = %d", errno);
 291                 if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
 292                         panic("check_ptrace : expected (SIGTRAP|SYSCALL_TRAP), "
 293                               "got status = %d", status);
 294
 295                 syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
 296                                  0);
 297                 if(syscall == __NR_getpid){
 298                         if (!count)
 299                                 panic("check_ptrace : SYSEMU_SINGLESTEP doesn't singlestep");
 300                         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
 301                                    os_getpid());
 302                         if(n < 0)
 303                                 panic("check_sysemu : failed to modify system "
 304                                       "call return, errno = %d", errno);
 305                         break;
 306                 }
 307         }
 308         if (stop_ptraced_child(pid, stack, 0, 0) < 0)
 309                 goto fail_stopped;
 310
 311         sysemu_supported = 2;
 312         printk("OK\n");
 313
 314         if ( !force_sysemu_disabled )
 315                 set_using_sysemu(sysemu_supported);
 316         return;
 317
 318 fail:
 319         stop_ptraced_child(pid, stack, 1, 0);
 320 fail_stopped:
 321         printk("missing\n");
 322 }
 323
 324 void __init check_ptrace(void)
 325 {
 326         void *stack;
 327         int pid, syscall, n, status;
 328
 329         printk("Checking that ptrace can change system call numbers...");
 330         pid = start_ptraced_child(&stack);
 331
 332         if (ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
 333                 panic("check_ptrace: PTRACE_SETOPTIONS failed, errno = %d", errno);
 334
 335         while(1){
 336                 if(ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)
 337                         panic("check_ptrace : ptrace failed, errno = %d",
 338                               errno);
 339                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 340                 if(n < 0)
 341                         panic("check_ptrace : wait failed, errno = %d", errno);
 342                 if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP + 0x80))
 343                         panic("check_ptrace : expected SIGTRAP + 0x80, "
 344                               "got status = %d", status);
 345
 346                 syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
 347                                  0);
 348                 if(syscall == __NR_getpid){
 349                         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
 350                                    __NR_getppid);
 351                         if(n < 0)
 352                                 panic("check_ptrace : failed to modify system "
 353                                       "call, errno = %d", errno);
 354                         break;
 355                 }
 356         }
 357         stop_ptraced_child(pid, stack, 0, 1);
 358         printk("OK\n");
 359         check_sysemu();
 360 }
 361
 362 int run_kernel_thread(int (*fn)(void *), void *arg, void **jmp_ptr)
 363 {
 364         sigjmp_buf buf;
 365         int n;
 366
 367         *jmp_ptr = &buf;
 368         n = sigsetjmp(buf, 1);
 369         if(n != 0)
 370                 return(n);
 371         (*fn)(arg);
 372         return(0);
 373 }
 374
 375 void forward_pending_sigio(int target)
 376 {
 377         sigset_t sigs;
 378
 379         if(sigpending(&sigs))
 380                 panic("forward_pending_sigio : sigpending failed");
 381         if(sigismember(&sigs, SIGIO))
 382                 kill(target, SIGIO);
 383 }
 384
 385 extern void *__syscall_stub_start, __syscall_stub_end;
 386
 387 #ifdef UML_CONFIG_MODE_SKAS
 388
 389 static inline void check_skas3_ptrace_support(void)
 390 {
 391         struct ptrace_faultinfo fi;
 392         void *stack;
 393         int pid, n;
 394
 395         printf("Checking for the skas3 patch in the host...");
 396         pid = start_ptraced_child(&stack);
 397
 398         n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
 399         if (n < 0) {
 400                 ptrace_faultinfo = 0;
 401                 if(errno == EIO)
 402                         printf("not found\n");
 403                 else {
 404                         perror("not found");
 405                 }
 406         }
 407         else {
 408                 if (!ptrace_faultinfo)
 409                         printf("found but disabled on command line\n");
 410                 else
 411                         printf("found\n");
 412         }
 413
 414         init_registers(pid);
 415         stop_ptraced_child(pid, stack, 1, 1);
 416 }
 417
 418 int can_do_skas(void)
 419 {
 420         printf("Checking for /proc/mm...");
 421         if (os_access("/proc/mm", OS_ACC_W_OK) < 0) {
 422                 proc_mm = 0;
 423                 printf("not found\n");
 424         } else {
 425                 if (!proc_mm)
 426                         printf("found but disabled on command line\n");
 427                 else
 428                         printf("found\n");
 429         }
 430
 431         check_skas3_ptrace_support();
 432         return 1;
 433 }
 434 #else
 435 int can_do_skas(void)
 436 {
 437         return(0);
 438 }
 439 #endif