components/nacl/loader/nonsfi/irt_memory.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include <errno.h>
   6 #include <sys/mman.h>
   7
   8 #include "base/logging.h"
   9 #include "components/nacl/loader/nonsfi/irt_interfaces.h"
  10 #include "components/nacl/loader/nonsfi/irt_util.h"
  11 #include "native_client/src/trusted/service_runtime/include/machine/_types.h"
  12 #include "native_client/src/trusted/service_runtime/include/sys/mman.h"
  13
  14 namespace nacl {
  15 namespace nonsfi {
  16 namespace {
  17
  18 int NaClProtToProt(int nacl_prot) {
  19   int prot = 0;
  20   if ((nacl_prot & NACL_ABI_PROT_MASK) == NACL_ABI_PROT_NONE)
  21     return PROT_NONE;
  22
  23   if (nacl_prot & NACL_ABI_PROT_READ)
  24     prot |= PROT_READ;
  25   if (nacl_prot & NACL_ABI_PROT_WRITE)
  26     prot |= PROT_WRITE;
  27   if (nacl_prot & NACL_ABI_PROT_EXEC)
  28     prot |= PROT_EXEC;
  29   return prot;
  30 }
  31
  32 int NaClFlagsToFlags(int nacl_flags) {
  33   int flags = 0;
  34
  35   if (nacl_flags & NACL_ABI_MAP_SHARED)
  36     flags |= MAP_SHARED;
  37   if (nacl_flags & NACL_ABI_MAP_PRIVATE)
  38     flags |= MAP_PRIVATE;
  39   if (nacl_flags & NACL_ABI_MAP_FIXED)
  40     flags |= MAP_FIXED;
  41
  42   // Note: NACL_ABI_MAP_ANON is an alias of NACL_ABI_MAP_ANONYMOUS.
  43   if (nacl_flags & NACL_ABI_MAP_ANONYMOUS)
  44     flags |= MAP_ANONYMOUS;
  45   return flags;
  46 }
  47
  48 int IrtMMap(void** addr, size_t len, int prot, int flags,
  49             int fd, nacl_abi_off_t off) {
  50   const int host_prot = NaClProtToProt(prot);
  51   // On Chrome OS, mmap can fail if PROT_EXEC is set in |host_prot|,
  52   // but mprotect will allow changing the permissions later.
  53   // This is because Chrome OS mounts writable filesystems with "noexec".
  54   void* result = mmap(
  55       *addr, len, host_prot & ~PROT_EXEC, NaClFlagsToFlags(flags), fd, off);
  56   if (result == MAP_FAILED)
  57     return errno;
  58   if (host_prot & PROT_EXEC) {
  59     if (mprotect(result, len, host_prot) != 0) {
  60       // This aborts here because it cannot easily undo the mmap() call.
  61       PLOG(FATAL) << "IrtMMap: mprotect to turn on PROT_EXEC failed.";
  62     }
  63   }
  64
  65   *addr = result;
  66   return 0;
  67 }
  68
  69 int IrtMUnmap(void* addr, size_t len) {
  70   return CheckError(munmap(addr, len));
  71 }
  72
  73 int IrtMProtect(void* addr, size_t len, int prot) {
  74   return CheckError(mprotect(addr, len, NaClProtToProt(prot)));
  75 }
  76
  77 }  // namespace
  78
  79 // For mmap, the argument types should be nacl_abi_off_t rather than off_t.
  80 // However, the definition of nacl_irt_memory uses the host type off_t, so here
  81 // we need to cast it.
  82 const nacl_irt_memory kIrtMemory = {
  83   reinterpret_cast<int(*)(void**, size_t, int, int, int, off_t)>(IrtMMap),
  84   IrtMUnmap,
  85   IrtMProtect,
  86 };
  87
  88 }  // namespace nonsfi
  89 }  // namespace nacl