intermodule_comm/nacl_imc_unistd.cc

   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 inter-module communication primitives.
  34 //
  35 // This file implements common parts of IMC for "unix like systems" (i.e. not
  36 // used on Windows).
  37
  38 // TODO: Perhaps this file should go into a platform-specific directory
  39 // (posix? unixlike?)  We have a little convention going where mac/linux stuff
  40 // goes in the linux directory and is referenced by the mac build but that's a
  41 // little sloppy.
  42
  43 #include "native_client/intermodule_comm/nacl_imc.h"
  44
  45 #include <assert.h>
  46 #include <ctype.h>
  47 #include <errno.h>
  48 #include <fcntl.h>
  49 #include <limits.h>
  50 #include <stdio.h>
  51 #include <string.h>
  52 #include <unistd.h>
  53 #include <sys/mman.h>
  54 #include <sys/types.h>
  55
  56 #include <algorithm>
  57
  58 #include "native_client/include/atomic_ops.h"
  59
  60 namespace nacl {
  61
  62 namespace {
  63
  64 // The pathname prefix for memory objects created by CreateMemoryObject().
  65 const char kShmPrefix[] = "/google-nacl-shm-";
  66
  67 }  // namespace
  68
  69 bool WouldBlock() {
  70   return (errno == EAGAIN) ? true : false;
  71 }
  72
  73 int GetLastErrorString(char* buffer, size_t length) {
  74 #if NACL_LINUX
  75   // Note some Linux distributions provide only GNU version of strerror_r().
  76   if (buffer == NULL || length == 0) {
  77     errno = ERANGE;
  78     return -1;
  79   }
  80   char* message = strerror_r(errno, buffer, length);
  81   if (message != buffer) {
  82     size_t message_bytes = strlen(message) + 1;
  83     length = std::min(message_bytes, length);
  84     memmove(buffer, message, length);
  85     buffer[length - 1] = '\0';
  86   }
  87   return 0;
  88 #else
  89   return strerror_r(errno, buffer, length);
  90 #endif
  91 }
  92
  93 Handle CreateMemoryObject(size_t length) {
  94   static AtomicWord memory_object_count;
  95
  96   char name[PATH_MAX];
  97   for (;;) {
  98     snprintf(name, sizeof name, "%s-%u.%u", kShmPrefix,
  99              getpid(),
 100              static_cast<uint32_t>(AtomicIncrement(&memory_object_count, 1)));
 101     int m = shm_open(name, O_RDWR | O_CREAT | O_EXCL, 0666);
 102     if (0 <= m) {
 103       if (ftruncate(m, length) == -1) {
 104         close(m);
 105         m = -1;
 106       }
 107       shm_unlink(name);
 108       return m;
 109     }
 110     if (errno != EEXIST) {
 111       return -1;
 112     }
 113   }
 114 }
 115
 116 void* Map(void* start, size_t length, int prot, int flags,
 117           Handle memory, off_t offset) {
 118   static int posix_prot[4] = {
 119     PROT_NONE,
 120     PROT_READ,
 121     PROT_WRITE,
 122     PROT_READ | PROT_WRITE
 123   };
 124
 125   int adjusted = 0;
 126   if (flags & kMapShared) {
 127     adjusted |= MAP_SHARED;
 128   }
 129   if (flags & kMapPrivate) {
 130     adjusted |= MAP_PRIVATE;
 131   }
 132   if (flags & kMapFixed) {
 133     adjusted |= MAP_FIXED;
 134   }
 135   return mmap(start, length, posix_prot[prot & 3], adjusted, memory, offset);
 136 }
 137
 138 int Unmap(void* start, size_t length) {
 139   return munmap(start, length);
 140 }
 141
 142 }  // namespace nacl