link.h 8.1 KB

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  1. /* Data structure for communication from the run-time dynamic linker for
  2. loaded ELF shared objects.
  3. Copyright (C) 1995-2001, 2004, 2005, 2006 Free Software Foundation, Inc.
  4. This file is part of the GNU C Library.
  5. The GNU C Library is free software; you can redistribute it and/or
  6. modify it under the terms of the GNU Lesser General Public
  7. License as published by the Free Software Foundation; either
  8. version 2.1 of the License, or (at your option) any later version.
  9. The GNU C Library is distributed in the hope that it will be useful,
  10. but WITHOUT ANY WARRANTY; without even the implied warranty of
  11. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  12. Lesser General Public License for more details.
  13. You should have received a copy of the GNU Lesser General Public
  14. License along with the GNU C Library; if not, write to the Free
  15. Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  16. 02111-1307 USA. */
  17. #ifndef _LINK_H
  18. #define _LINK_H 1
  19. #include <features.h>
  20. #include <elf.h>
  21. #ifdef __HAVE_SHARED__
  22. #include <dlfcn.h>
  23. #endif
  24. #include <sys/types.h>
  25. #if defined _LIBC && defined __UCLIBC_HAS_TLS__
  26. #include <tls.h>
  27. #endif
  28. /* We use this macro to refer to ELF types independent of the native wordsize.
  29. `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'. */
  30. #define ElfW(type) _ElfW (Elf, __ELF_NATIVE_CLASS, type)
  31. #define _ElfW(e,w,t) _ElfW_1 (e, w, _##t)
  32. #define _ElfW_1(e,w,t) e##w##t
  33. #include <bits/elfclass.h> /* Defines __ELF_NATIVE_CLASS. */
  34. /* Rendezvous structure used by the run-time dynamic linker to communicate
  35. details of shared object loading to the debugger. If the executable's
  36. dynamic section has a DT_DEBUG element, the run-time linker sets that
  37. element's value to the address where this structure can be found. */
  38. struct r_debug
  39. {
  40. int r_version; /* Version number for this protocol. */
  41. struct link_map *r_map; /* Head of the chain of loaded objects. */
  42. /* This is the address of a function internal to the run-time linker,
  43. that will always be called when the linker begins to map in a
  44. library or unmap it, and again when the mapping change is complete.
  45. The debugger can set a breakpoint at this address if it wants to
  46. notice shared object mapping changes. */
  47. ElfW(Addr) r_brk;
  48. enum
  49. {
  50. /* This state value describes the mapping change taking place when
  51. the `r_brk' address is called. */
  52. RT_CONSISTENT, /* Mapping change is complete. */
  53. RT_ADD, /* Beginning to add a new object. */
  54. RT_DELETE /* Beginning to remove an object mapping. */
  55. } r_state;
  56. ElfW(Addr) r_ldbase; /* Base address the linker is loaded at. */
  57. };
  58. /* This is the instance of that structure used by the dynamic linker. */
  59. extern struct r_debug _r_debug;
  60. /* This symbol refers to the "dynamic structure" in the `.dynamic' section
  61. of whatever module refers to `_DYNAMIC'. So, to find its own
  62. `struct r_debug', a program could do:
  63. for (dyn = _DYNAMIC; dyn->d_tag != DT_NULL; ++dyn)
  64. if (dyn->d_tag == DT_DEBUG)
  65. r_debug = (struct r_debug *) dyn->d_un.d_ptr;
  66. */
  67. extern ElfW(Dyn) _DYNAMIC[];
  68. #ifdef __FDPIC__
  69. # include <bits/elf-fdpic.h>
  70. #endif
  71. /* Structure describing a loaded shared object. The `l_next' and `l_prev'
  72. members form a chain of all the shared objects loaded at startup.
  73. These data structures exist in space used by the run-time dynamic linker;
  74. modifying them may have disastrous results. */
  75. struct link_map
  76. {
  77. /* These first few members are part of the protocol with the debugger.
  78. This is the same format used in SVR4. */
  79. #ifdef __FDPIC__
  80. struct elf32_fdpic_loadaddr l_addr;
  81. #else
  82. ElfW(Addr) l_addr; /* Base address shared object is loaded at. */
  83. #endif
  84. char *l_name; /* Absolute file name object was found in. */
  85. ElfW(Dyn) *l_ld; /* Dynamic section of the shared object. */
  86. struct link_map *l_next, *l_prev; /* Chain of loaded objects. */
  87. #ifdef USE_TLS
  88. /* Thread-local storage related info. */
  89. /* Start of the initialization image. */
  90. void *l_tls_initimage;
  91. /* Size of the initialization image. */
  92. size_t l_tls_initimage_size;
  93. /* Size of the TLS block. */
  94. size_t l_tls_blocksize;
  95. /* Alignment requirement of the TLS block. */
  96. size_t l_tls_align;
  97. /* Offset of first byte module alignment. */
  98. size_t l_tls_firstbyte_offset;
  99. # ifndef NO_TLS_OFFSET
  100. # define NO_TLS_OFFSET 0
  101. # endif
  102. /* For objects present at startup time: offset in the static TLS block. */
  103. ptrdiff_t l_tls_offset;
  104. /* Index of the module in the dtv array. */
  105. size_t l_tls_modid;
  106. /* Nonzero if _dl_init_static_tls should be called for this module */
  107. unsigned int l_need_tls_init:1;
  108. #endif
  109. };
  110. #ifdef __USE_GNU
  111. #if 0
  112. /* Version numbers for la_version handshake interface. */
  113. #define LAV_CURRENT 1
  114. /* Activity types signaled through la_activity. */
  115. enum
  116. {
  117. LA_ACT_CONSISTENT, /* Link map consistent again. */
  118. LA_ACT_ADD, /* New object will be added. */
  119. LA_ACT_DELETE /* Objects will be removed. */
  120. };
  121. /* Values representing origin of name for dynamic loading. */
  122. enum
  123. {
  124. LA_SER_ORIG = 0x01, /* Original name. */
  125. LA_SER_LIBPATH = 0x02, /* Directory from LD_LIBRARY_PATH. */
  126. LA_SER_RUNPATH = 0x04, /* Directory from RPATH/RUNPATH. */
  127. LA_SER_CONFIG = 0x08, /* Found through ldconfig. */
  128. LA_SER_DEFAULT = 0x40, /* Default directory. */
  129. LA_SER_SECURE = 0x80 /* Unused. */
  130. };
  131. /* Values for la_objopen return value. */
  132. enum
  133. {
  134. LA_FLG_BINDTO = 0x01, /* Audit symbols bound to this object. */
  135. LA_FLG_BINDFROM = 0x02 /* Audit symbols bound from this object. */
  136. };
  137. /* Values for la_symbind flags parameter. */
  138. enum
  139. {
  140. LA_SYMB_NOPLTENTER = 0x01, /* la_pltenter will not be called. */
  141. LA_SYMB_NOPLTEXIT = 0x02, /* la_pltexit will not be called. */
  142. LA_SYMB_STRUCTCALL = 0x04, /* Return value is a structure. */
  143. LA_SYMB_DLSYM = 0x08, /* Binding due to dlsym call. */
  144. LA_SYMB_ALTVALUE = 0x10 /* Value has been changed by a previous
  145. la_symbind call. */
  146. };
  147. #endif
  148. struct dl_phdr_info
  149. {
  150. #ifdef __FDPIC__
  151. struct elf32_fdpic_loadaddr dlpi_addr;
  152. #else
  153. ElfW(Addr) dlpi_addr;
  154. #endif
  155. const char *dlpi_name;
  156. const ElfW(Phdr) *dlpi_phdr;
  157. ElfW(Half) dlpi_phnum;
  158. #if 0
  159. /* Note: Following members were introduced after the first
  160. version of this structure was available. Check the SIZE
  161. argument passed to the dl_iterate_phdr callback to determine
  162. whether or not each later member is available. */
  163. /* Incremented when a new object may have been added. */
  164. unsigned long long int dlpi_adds;
  165. /* Incremented when an object may have been removed. */
  166. unsigned long long int dlpi_subs;
  167. /* If there is a PT_TLS segment, its module ID as used in
  168. TLS relocations, else zero. */
  169. size_t dlpi_tls_modid;
  170. /* The address of the calling thread's instance of this module's
  171. PT_TLS segment, if it has one and it has been allocated
  172. in the calling thread, otherwise a null pointer. */
  173. void *dlpi_tls_data;
  174. #endif
  175. };
  176. __BEGIN_DECLS
  177. extern int dl_iterate_phdr (int (*__callback) (struct dl_phdr_info *,
  178. size_t, void *),
  179. void *__data);
  180. #if 0
  181. /* Prototypes for the ld.so auditing interfaces. These are not
  182. defined anywhere in ld.so but instead have to be provided by the
  183. auditing DSO. */
  184. extern unsigned int la_version (unsigned int __version);
  185. extern void la_activity (uintptr_t *__cookie, unsigned int __flag);
  186. extern char *la_objsearch (const char *__name, uintptr_t *__cookie,
  187. unsigned int __flag);
  188. extern unsigned int la_objopen (struct link_map *__map, Lmid_t __lmid,
  189. uintptr_t *__cookie);
  190. extern void la_preinit (uintptr_t *__cookie);
  191. extern uintptr_t la_symbind32 (Elf32_Sym *__sym, unsigned int __ndx,
  192. uintptr_t *__refcook, uintptr_t *__defcook,
  193. unsigned int *__flags, const char *__symname);
  194. extern uintptr_t la_symbind64 (Elf64_Sym *__sym, unsigned int __ndx,
  195. uintptr_t *__refcook, uintptr_t *__defcook,
  196. unsigned int *__flags, const char *__symname);
  197. extern unsigned int la_objclose (uintptr_t *__cookie);
  198. #endif
  199. __END_DECLS
  200. #endif
  201. #endif /* link.h */