1 /* Data structure for communication from the run-time dynamic linker for 2 loaded ELF shared objects. 3 Copyright (C) 1995-1999, 2000, 2001 Free Software Foundation, Inc. 4 This file is part of the GNU C Library. 5 6 The GNU C Library is free software; you can redistribute it and/or 7 modify it under the terms of the GNU Lesser General Public 8 License as published by the Free Software Foundation; either 9 version 2.1 of the License, or (at your option) any later version. 10 11 The GNU C Library is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 Lesser General Public License for more details. 15 16 You should have received a copy of the GNU Lesser General Public 17 License along with the GNU C Library; if not, write to the Free 18 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 19 02111-1307 USA. */ 20 21 #ifndef _LINK_H 22 #define _LINK_H 1 23 24 #include <features.h> 25 #include <elf.h> 26 #include <dlfcn.h> 27 #include <sys/types.h> 28 29 #define DT_THISPROCNUM 0 30 /* We use this macro to refer to ELF types independent of the native wordsize. 31 `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'. */ 32 #define ElfW(type) _ElfW (Elf, __ELF_NATIVE_CLASS, type) 33 #define _ElfW(e,w,t) _ElfW_1 (e, w, _##t) 34 #define _ElfW_1(e,w,t) e##w##t 35 36 #include <sys/elfclass.h> /* Defines __ELF_NATIVE_CLASS. */ 37 #include <sys/link.h> 38 #include <dl-lookupcfg.h> 39 40 /* Rendezvous structure used by the run-time dynamic linker to communicate 41 details of shared object loading to the debugger. If the executable's 42 dynamic section has a DT_DEBUG element, the run-time linker sets that 43 element's value to the address where this structure can be found. */ 44 45 struct r_debug 46 { 47 int r_version; /* Version number for this protocol. */ 48 49 struct link_map *r_map; /* Head of the chain of loaded objects. */ 50 51 /* This is the address of a function internal to the run-time linker, 52 that will always be called when the linker begins to map in a 53 library or unmap it, and again when the mapping change is complete. 54 The debugger can set a breakpoint at this address if it wants to 55 notice shared object mapping changes. */ 56 ElfW(Addr) r_brk; 57 enum 58 { 59 /* This state value describes the mapping change taking place when 60 the `r_brk' address is called. */ 61 RT_CONSISTENT, /* Mapping change is complete. */ 62 RT_ADD, /* Beginning to add a new object. */ 63 RT_DELETE /* Beginning to remove an object mapping. */ 64 } r_state; 65 66 ElfW(Addr) r_ldbase; /* Base address the linker is loaded at. */ 67 }; 68 69 /* This is the instance of that structure used by the dynamic linker. */ 70 extern struct r_debug _r_debug; 71 72 /* This symbol refers to the "dynamic structure" in the `.dynamic' section 73 of whatever module refers to `_DYNAMIC'. So, to find its own 74 `struct r_debug', a program could do: 75 for (dyn = _DYNAMIC; dyn->d_tag != DT_NULL; ++dyn) 76 if (dyn->d_tag == DT_DEBUG) 77 r_debug = (struct r_debug *) dyn->d_un.d_ptr; 78 */ 79 extern ElfW(Dyn) _DYNAMIC[]; 80 81 82 /* Some internal data structures of the dynamic linker used in the 83 linker map. We only provide forward declarations. */ 84 struct libname_list; 85 struct r_found_version; 86 struct r_search_path_elem; 87 88 /* Forward declaration. */ 89 struct link_map; 90 91 /* Structure to describe a single list of scope elements. The lookup 92 functions get passed an array of pointers to such structures. */ 93 struct r_scope_elem 94 { 95 /* Array of maps for the scope. */ 96 struct link_map **r_list; 97 /* Number of entries in the scope. */ 98 unsigned int r_nlist; 99 }; 100 101 102 /* Structure to record search path and allocation mechanism. */ 103 struct r_search_path_struct 104 { 105 struct r_search_path_elem **dirs; 106 int malloced; 107 }; 108 109 110 /* Structure describing a loaded shared object. The `l_next' and `l_prev' 111 members form a chain of all the shared objects loaded at startup. 112 113 These data structures exist in space used by the run-time dynamic linker; 114 modifying them may have disastrous results. 115 116 This data structure might change in future, if necessary. User-level 117 programs must avoid defining objects of this type. */ 118 119 struct link_map 120 { 121 /* These first few members are part of the protocol with the debugger. 122 This is the same format used in SVR4. */ 123 124 ElfW(Addr) l_addr; /* Base address shared object is loaded at. */ 125 char *l_name; /* Absolute file name object was found in. */ 126 ElfW(Dyn) *l_ld; /* Dynamic section of the shared object. */ 127 struct link_map *l_next, *l_prev; /* Chain of loaded objects. */ 128 129 /* All following members are internal to the dynamic linker. 130 They may change without notice. */ 131 132 struct libname_list *l_libname; 133 /* Indexed pointers to dynamic section. 134 [0,DT_NUM) are indexed by the processor-independent tags. 135 [DT_NUM,DT_NUM+DT_THISPROCNUM) are indexed by the tag minus DT_LOPROC. 136 [DT_NUM+DT_THISPROCNUM,DT_NUM+DT_THISPROCNUM+DT_EXTRANUM) are indexed 137 by DT_EXTRATAGIDX(tagvalue) and 138 [DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM, 139 DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM) 140 are indexed by DT_EXTRATAGIDX(tagvalue) (see <elf.h>). */ 141 142 ElfW(Dyn) *l_info[DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGNUM 143 + DT_EXTRANUM]; 144 const ElfW(Phdr) *l_phdr; /* Pointer to program header table in core. */ 145 ElfW(Addr) l_entry; /* Entry point location. */ 146 ElfW(Half) l_phnum; /* Number of program header entries. */ 147 ElfW(Half) l_ldnum; /* Number of dynamic segment entries. */ 148 149 /* Array of DT_NEEDED dependencies and their dependencies, in 150 dependency order for symbol lookup (with and without 151 duplicates). There is no entry before the dependencies have 152 been loaded. */ 153 struct r_scope_elem l_searchlist; 154 155 /* We need a special searchlist to process objects marked with 156 DT_SYMBOLIC. */ 157 struct r_scope_elem l_symbolic_searchlist; 158 159 /* Dependent object that first caused this object to be loaded. */ 160 struct link_map *l_loader; 161 162 /* Symbol hash table. */ 163 Elf_Symndx l_nbuckets; 164 const Elf_Symndx *l_buckets, *l_chain; 165 166 unsigned int l_opencount; /* Reference count for dlopen/dlclose. */ 167 enum /* Where this object came from. */ 168 { 169 lt_executable, /* The main executable program. */ 170 lt_library, /* Library needed by main executable. */ 171 lt_loaded /* Extra run-time loaded shared object. */ 172 } l_type:2; 173 unsigned int l_relocated:1; /* Nonzero if object's relocations done. */ 174 unsigned int l_init_called:1; /* Nonzero if DT_INIT function called. */ 175 unsigned int l_global:1; /* Nonzero if object in _dl_global_scope. */ 176 unsigned int l_reserved:2; /* Reserved for internal use. */ 177 unsigned int l_phdr_allocated:1; /* Nonzero if the data structure pointed 178 to by `l_phdr' is allocated. */ 179 unsigned int l_soname_added:1; /* Nonzero if the SONAME is for sure in 180 the l_libname list. */ 181 unsigned int l_faked:1; /* Nonzero if this is a faked descriptor 182 without associated file. */ 183 184 /* Array with version names. */ 185 unsigned int l_nversions; 186 struct r_found_version *l_versions; 187 188 /* Collected information about own RPATH directories. */ 189 struct r_search_path_struct l_rpath_dirs; 190 191 /* Collected results of relocation while profiling. */ 192 ElfW(Addr) *l_reloc_result; 193 194 /* Pointer to the version information if available. */ 195 ElfW(Versym) *l_versyms; 196 197 /* String specifying the path where this object was found. */ 198 const char *l_origin; 199 200 /* Start and finish of memory map for this object. l_map_start 201 need not be the same as l_addr. */ 202 ElfW(Addr) l_map_start, l_map_end; 203 204 /* Default array for 'l_scope'. */ 205 struct r_scope_elem *l_scope_mem[4]; 206 /* Size of array allocated for 'l_scope'. */ 207 size_t l_scope_max; 208 /* This is an array defining the lookup scope for this link map. 209 There are at most three different scope lists. */ 210 struct r_scope_elem **l_scope; 211 212 /* A similar array, this time only with the local scope. This is 213 used occasionally. */ 214 struct r_scope_elem *l_local_scope[2]; 215 216 /* This information is kept to check for sure whether a shared 217 object is the same as one already loaded. */ 218 dev_t l_dev; 219 ino64_t l_ino; 220 221 /* Collected information about own RUNPATH directories. */ 222 struct r_search_path_struct l_runpath_dirs; 223 224 /* List of object in order of the init and fini calls. */ 225 struct link_map **l_initfini; 226 227 /* List of the dependencies introduced through symbol binding. */ 228 unsigned int l_reldepsmax; 229 unsigned int l_reldepsact; 230 struct link_map **l_reldeps; 231 232 /* Various flag words. */ 233 ElfW(Word) l_feature_1; 234 ElfW(Word) l_flags_1; 235 236 /* Temporarily used in `dl_close'. */ 237 unsigned int l_idx; 238 239 struct link_map_machine l_mach; 240 241 struct 242 { 243 const ElfW(Sym) *sym; 244 int type_class; 245 #ifdef DL_LOOKUP_RETURNS_MAP 246 struct link_map *value; 247 #else 248 ElfW(Addr) value; 249 #endif 250 const ElfW(Sym) *ret; 251 } l_lookup_cache; 252 }; 253 254 struct dl_phdr_info 255 { 256 ElfW(Addr) dlpi_addr; 257 const char *dlpi_name; 258 const ElfW(Phdr) *dlpi_phdr; 259 ElfW(Half) dlpi_phnum; 260 }; 261 262 extern int dl_iterate_phdr (int (*callback) (struct dl_phdr_info *info, 263 size_t size, void *data), 264 void *data); 265 extern int __dl_iterate_phdr (int (*callback) (struct dl_phdr_info *info, 266 size_t size, void *data), 267 void *data); 268 269 #endif /* link.h */ 270