base/android/linker/android_dlext.h

   1 // Copyright 2015 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 // Definitions for android_dlopen_ext().
   6 //
   7 // This function was added for Android L-MR1 and made available in android-21
   8 // but we currently build Chromium with android-16. Placing the declarations
   9 // we need here allows code that uses android_dlopen_ext() to build with
  10 // android-16. At runtime we check the target's SDK_INT to ensure that we
  11 // are on a system new enough to offer this function, and also only access
  12 // it with dlsym so that the runtime linker on pre-Android L-MR1 targets will
  13 // not complain about a missing symbol when loading our library.
  14 //
  15 // Details below taken from:
  16 //   third_party/android_tools/ndk/platforms/android-21
  17 //       /arch-arm/usr/include/android/dlext.h
  18 //
  19 // Although taken specifically from arch-arm, there are no architecture-
  20 // specific elements in dlext.h. All android-21/arch-* directories contain
  21 // identical copies of dlext.h.
  22
  23 #ifndef BASE_ANDROID_LINKER_ANDROID_DLEXT_H_
  24 #define BASE_ANDROID_LINKER_ANDROID_DLEXT_H_
  25
  26 #include <stddef.h>
  27 #include <stdint.h>
  28
  29 /* bitfield definitions for android_dlextinfo.flags */
  30 enum {
  31   /* When set, the reserved_addr and reserved_size fields must point to an
  32    * already-reserved region of address space which will be used to load the
  33    * library if it fits. If the reserved region is not large enough, the load
  34    * will fail.
  35    */
  36   ANDROID_DLEXT_RESERVED_ADDRESS      = 0x1,
  37
  38   /* As DLEXT_RESERVED_ADDRESS, but if the reserved region is not large enough,
  39    * the linker will choose an available address instead.
  40    */
  41   ANDROID_DLEXT_RESERVED_ADDRESS_HINT = 0x2,
  42
  43   /* When set, write the GNU RELRO section of the mapped library to relro_fd
  44    * after relocation has been performed, to allow it to be reused by another
  45    * process loading the same library at the same address. This implies
  46    * ANDROID_DLEXT_USE_RELRO.
  47    */
  48   ANDROID_DLEXT_WRITE_RELRO           = 0x4,
  49
  50   /* When set, compare the GNU RELRO section of the mapped library to relro_fd
  51    * after relocation has been performed, and replace any relocated pages that
  52    * are identical with a version mapped from the file.
  53    */
  54   ANDROID_DLEXT_USE_RELRO             = 0x8,
  55
  56   /* Instruct dlopen to use library_fd instead of opening file by name.
  57    * The filename parameter is still used to identify the library.
  58    */
  59   ANDROID_DLEXT_USE_LIBRARY_FD        = 0x10,
  60
  61   /* Mask of valid bits */
  62   ANDROID_DLEXT_VALID_FLAG_BITS       = ANDROID_DLEXT_RESERVED_ADDRESS |
  63                                         ANDROID_DLEXT_RESERVED_ADDRESS_HINT |
  64                                         ANDROID_DLEXT_WRITE_RELRO |
  65                                         ANDROID_DLEXT_USE_RELRO |
  66                                         ANDROID_DLEXT_USE_LIBRARY_FD,
  67 };
  68
  69 typedef struct {
  70   uint64_t flags;
  71   void*   reserved_addr;
  72   size_t  reserved_size;
  73   int     relro_fd;
  74   int     library_fd;
  75 } android_dlextinfo;
  76
  77 #endif  // BASE_ANDROID_LINKER_ANDROID_DLEXT_H_