service_runtime/nacl_syscall_hook.c

   1 /*
   2  * Copyright 2008, Google Inc.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met:
   8  *
   9  *     * Redistributions of source code must retain the above copyright
  10  * notice, this list of conditions and the following disclaimer.
  11  *     * Redistributions in binary form must reproduce the above
  12  * copyright notice, this list of conditions and the following disclaimer
  13  * in the documentation and/or other materials provided with the
  14  * distribution.
  15  *     * Neither the name of Google Inc. nor the names of its
  16  * contributors may be used to endorse or promote products derived from
  17  * this software without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  20  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  21  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  22  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  23  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  26  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  27  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  28  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  29  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 /*
  33  * NaCl service run-time.
  34  */
  35
  36 #include "native_client/include/portability.h"
  37 #include "native_client/include/nacl_platform.h"
  38
  39 #include <stdlib.h>
  40 #include <errno.h>
  41 #if NACL_WINDOWS
  42 /* TODO: IS THIS STILL NEEDED FOR WINDOWS ??? */
  43 #include <sys/timeb.h>
  44 #endif
  45 #include <fcntl.h>
  46 #include <time.h>
  47
  48 #include "native_client/service_runtime/nacl_globals.h"
  49 #include "native_client/service_runtime/nacl_config.h"
  50 #include "native_client/service_runtime/nacl_log.h"
  51 #include "native_client/service_runtime/sel_ldr.h"
  52 #include "native_client/service_runtime/nacl_switch_to_app.h"
  53 #include "native_client/service_runtime/nacl_syscall_handlers.h"
  54
  55 #include "native_client/service_runtime/include/sys/errno.h"
  56 #include "native_client/service_runtime/include/bits/nacl_syscalls.h"
  57
  58 /*
  59  * Simple RPC support.  The default socket file descriptor is invalid.
  60  */
  61 int NaClSrpcFileDescriptor = -1;
  62
  63
  64
  65 NORETURN void NaClSyscallCSegHook(int32_t ldt_ix)
  66 {
  67   struct NaClAppThread      *natp = nacl_thread[ldt_ix];
  68   struct NaClApp            *nap = natp->nap;
  69   struct NaClThreadContext  *user = &natp->user;
  70   uintptr_t                 tramp_addr;
  71   uint32_t                  tramp_ret;
  72   uint32_t                  aligned_tramp_ret;
  73   uint32_t                  sysnum;
  74
  75   /* esp must be okay for control to have gotten here */
  76 #if !BENCHMARK
  77   NaClLog(4, "Entered NaClSyscallCSegHook\n");
  78   NaClLog(4, "user esp 0x%08x\n", user->esp);
  79 #endif
  80   /*
  81    * on user stack:
  82    *  esp+0:  retaddr from lcall
  83    *  esp+4:  code seg from lcall
  84    *  esp+8:  retaddr from syscall wrapper
  85    *  esp+c:  ...
  86    */
  87   tramp_addr = NaClUserToSys(nap, user->esp);
  88   tramp_ret = *(uint32_t *) tramp_addr;
  89   /*
  90    * return addr could have been tampered with by another thread, but
  91    * the only result would be a bad sysnum.
  92    */
  93   sysnum = (tramp_ret - NACL_SYSCALL_START_ADDR)
  94       >> NACL_SYSCALL_BLOCK_SHIFT;
  95
  96 #if !BENCHMARK
  97   NaClLog(4, "system call %d\n", sysnum);
  98 #endif
  99   /*
 100    * keep tramp_ret in user addr; do not bother to ensure tramp_addr +
 101    * 8 is valid, since even if we loaded two NaClApps next to each
 102    * other this would just load the trampoline code, or hit the
 103    * inaccessible page for NULL pointer detection (once we get that
 104    * implemented).  if it is not a valid address, we would just crash.
 105    */
 106   tramp_ret = *(uint32_t *) (tramp_addr + 8);
 107   if (0 != nap->xlate_base) {
 108     /*
 109      * ensure that tramp_ret value is ok.  no need to ensure that this
 110      * is in the app's address space, since the syscall return will
 111      * just result in a fault after we reconstitute the sandbox and
 112      * attempt to pass control to this address.
 113      */
 114     aligned_tramp_ret = tramp_ret & ~(nap->align_boundary - 1);
 115     if (tramp_ret != aligned_tramp_ret) {
 116       NaClLog(LOG_FATAL, ("NaClSyscallCSegHook: tramp_ret infinite loop:"
 117                           " %08x != %08x\nMake sure NaCl SDK and sel_ldr"
 118                           " agree on alignment (ELF header of NaCl app"
 119                           " claims alignment is %d).\n"),
 120               tramp_ret, aligned_tramp_ret, nap->align_boundary);
 121     }
 122     tramp_ret = aligned_tramp_ret;
 123   }
 124
 125   user->esp += 0xc;  /* call, lcall */
 126   if (sysnum >= NACL_MAX_SYSCALLS) {
 127     NaClLog(2, "INVALID system call %d\n", sysnum);
 128     natp->sysret = -NACL_ABI_EINVAL;
 129   } else {
 130 #if !BENCHMARK
 131     NaClLog(4, "making system call %d, handler 0x%08x\n",
 132             sysnum, (uintptr_t) nacl_syscall[sysnum].handler);
 133 #endif
 134
 135     natp->x_esp = (uint32_t *) (tramp_addr + 0xc);
 136     natp->sysret = (*nacl_syscall[sysnum].handler)(natp);
 137   }
 138 #if !BENCHMARK
 139   NaClLog(4, "returning from system call %d, return value %d (0x%x)\n",
 140           sysnum, natp->sysret, natp->sysret);
 141
 142   NaClLog(4, "return target 0x%08x\n", tramp_ret);
 143   NaClLog(4, "user esp 0x%08x\n", user->esp);
 144 #endif
 145   NaClSwitchToApp(natp, tramp_ret);
 146  /* NOTREACHED */
 147
 148   fprintf(stderr, "NORETURN NaClSwitchToApp returned!?!\n");
 149   abort();
 150 }