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