include/link.h

   1 /* Data structure for communication from the run-time dynamic linker for
   2    loaded ELF shared objects.
   3    Copyright (C) 1995-2016 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, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef _PRIVATE_LINK_H
  21 #define _PRIVATE_LINK_H 1
  22
  23 #ifdef _LINK_H
  24 # error this should be impossible
  25 #endif
  26
  27 /* Get most of the contents from the public header, but we define a
  28    different `struct link_map' type for private use.  The la_objopen
  29    prototype uses the type, so we have to declare it separately.  */
  30 #define link_map        link_map_public
  31 #define la_objopen      la_objopen_wrongproto
  32 #include <elf/link.h>
  33 #undef  link_map
  34 #undef  la_objopen
  35
  36 struct link_map;
  37 extern unsigned int la_objopen (struct link_map *__map, Lmid_t __lmid,
  38                                 uintptr_t *__cookie);
  39
  40 #include <stdint.h>
  41 #include <stddef.h>
  42 #include <linkmap.h>
  43 #include <dl-fileid.h>
  44 #include <dl-lookupcfg.h>
  45 #include <tls.h>
  46 #include <libc-lock.h>
  47
  48
  49 /* Some internal data structures of the dynamic linker used in the
  50    linker map.  We only provide forward declarations.  */
  51 struct libname_list;
  52 struct r_found_version;
  53 struct r_search_path_elem;
  54
  55 /* Forward declaration.  */
  56 struct link_map;
  57
  58 /* Structure to describe a single list of scope elements.  The lookup
  59    functions get passed an array of pointers to such structures.  */
  60 struct r_scope_elem
  61 {
  62   /* Array of maps for the scope.  */
  63   struct link_map **r_list;
  64   /* Number of entries in the scope.  */
  65   unsigned int r_nlist;
  66 };
  67
  68
  69 /* Structure to record search path and allocation mechanism.  */
  70 struct r_search_path_struct
  71   {
  72     struct r_search_path_elem **dirs;
  73     int malloced;
  74   };
  75
  76
  77 /* Structure describing a loaded shared object.  The `l_next' and `l_prev'
  78    members form a chain of all the shared objects loaded at startup.
  79
  80    These data structures exist in space used by the run-time dynamic linker;
  81    modifying them may have disastrous results.
  82
  83    This data structure might change in future, if necessary.  User-level
  84    programs must avoid defining objects of this type.  */
  85
  86 struct link_map
  87   {
  88     /* These first few members are part of the protocol with the debugger.
  89        This is the same format used in SVR4.  */
  90
  91     ElfW(Addr) l_addr;          /* Difference between the address in the ELF
  92                                    file and the addresses in memory.  */
  93     char *l_name;               /* Absolute file name object was found in.  */
  94     ElfW(Dyn) *l_ld;            /* Dynamic section of the shared object.  */
  95     struct link_map *l_next, *l_prev; /* Chain of loaded objects.  */
  96
  97     /* All following members are internal to the dynamic linker.
  98        They may change without notice.  */
  99
 100     /* This is an element which is only ever different from a pointer to
 101        the very same copy of this type for ld.so when it is used in more
 102        than one namespace.  */
 103     struct link_map *l_real;
 104
 105     /* Number of the namespace this link map belongs to.  */
 106     Lmid_t l_ns;
 107
 108     struct libname_list *l_libname;
 109     /* Indexed pointers to dynamic section.
 110        [0,DT_NUM) are indexed by the processor-independent tags.
 111        [DT_NUM,DT_NUM+DT_THISPROCNUM) are indexed by the tag minus DT_LOPROC.
 112        [DT_NUM+DT_THISPROCNUM,DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM) are
 113        indexed by DT_VERSIONTAGIDX(tagvalue).
 114        [DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM,
 115         DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM) are indexed by
 116        DT_EXTRATAGIDX(tagvalue).
 117        [DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM,
 118         DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM+DT_VALNUM) are
 119        indexed by DT_VALTAGIDX(tagvalue) and
 120        [DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM+DT_VALNUM,
 121         DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM+DT_VALNUM+DT_ADDRNUM)
 122        are indexed by DT_ADDRTAGIDX(tagvalue), see <elf.h>.  */
 123
 124     ElfW(Dyn) *l_info[DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGNUM
 125                       + DT_EXTRANUM + DT_VALNUM + DT_ADDRNUM];
 126     const ElfW(Phdr) *l_phdr;   /* Pointer to program header table in core.  */
 127     ElfW(Addr) l_entry;         /* Entry point location.  */
 128     ElfW(Half) l_phnum;         /* Number of program header entries.  */
 129     ElfW(Half) l_ldnum;         /* Number of dynamic segment entries.  */
 130
 131     /* Array of DT_NEEDED dependencies and their dependencies, in
 132        dependency order for symbol lookup (with and without
 133        duplicates).  There is no entry before the dependencies have
 134        been loaded.  */
 135     struct r_scope_elem l_searchlist;
 136
 137     /* We need a special searchlist to process objects marked with
 138        DT_SYMBOLIC.  */
 139     struct r_scope_elem l_symbolic_searchlist;
 140
 141     /* Dependent object that first caused this object to be loaded.  */
 142     struct link_map *l_loader;
 143
 144     /* Array with version names.  */
 145     struct r_found_version *l_versions;
 146     unsigned int l_nversions;
 147
 148     /* Symbol hash table.  */
 149     Elf_Symndx l_nbuckets;
 150     Elf32_Word l_gnu_bitmask_idxbits;
 151     Elf32_Word l_gnu_shift;
 152     const ElfW(Addr) *l_gnu_bitmask;
 153     union
 154     {
 155       const Elf32_Word *l_gnu_buckets;
 156       const Elf_Symndx *l_chain;
 157     };
 158     union
 159     {
 160       const Elf32_Word *l_gnu_chain_zero;
 161       const Elf_Symndx *l_buckets;
 162     };
 163
 164     unsigned int l_direct_opencount; /* Reference count for dlopen/dlclose.  */
 165     enum                        /* Where this object came from.  */
 166       {
 167         lt_executable,          /* The main executable program.  */
 168         lt_library,             /* Library needed by main executable.  */
 169         lt_loaded               /* Extra run-time loaded shared object.  */
 170       } l_type:2;
 171     unsigned int l_relocated:1; /* Nonzero if object's relocations done.  */
 172     unsigned int l_init_called:1; /* Nonzero if DT_INIT function called.  */
 173     unsigned int l_global:1;    /* Nonzero if object in _dl_global_scope.  */
 174     unsigned int l_reserved:2;  /* Reserved for internal use.  */
 175     unsigned int l_phdr_allocated:1; /* Nonzero if the data structure pointed
 176                                         to by `l_phdr' is allocated.  */
 177     unsigned int l_soname_added:1; /* Nonzero if the SONAME is for sure in
 178                                       the l_libname list.  */
 179     unsigned int l_faked:1;     /* Nonzero if this is a faked descriptor
 180                                    without associated file.  */
 181     unsigned int l_need_tls_init:1; /* Nonzero if GL(dl_init_static_tls)
 182                                        should be called on this link map
 183                                        when relocation finishes.  */
 184     unsigned int l_auditing:1;  /* Nonzero if the DSO is used in auditing.  */
 185     unsigned int l_audit_any_plt:1; /* Nonzero if at least one audit module
 186                                        is interested in the PLT interception.*/
 187     unsigned int l_removed:1;   /* Nozero if the object cannot be used anymore
 188                                    since it is removed.  */
 189     unsigned int l_contiguous:1; /* Nonzero if inter-segment holes are
 190                                     mprotected or if no holes are present at
 191                                     all.  */
 192     unsigned int l_symbolic_in_local_scope:1; /* Nonzero if l_local_scope
 193                                                  during LD_TRACE_PRELINKING=1
 194                                                  contains any DT_SYMBOLIC
 195                                                  libraries.  */
 196     unsigned int l_free_initfini:1; /* Nonzero if l_initfini can be
 197                                        freed, ie. not allocated with
 198                                        the dummy malloc in ld.so.  */
 199
 200     /* Collected information about own RPATH directories.  */
 201     struct r_search_path_struct l_rpath_dirs;
 202
 203     /* Collected results of relocation while profiling.  */
 204     struct reloc_result
 205     {
 206       DL_FIXUP_VALUE_TYPE addr;
 207       struct link_map *bound;
 208       unsigned int boundndx;
 209       uint32_t enterexit;
 210       unsigned int flags;
 211     } *l_reloc_result;
 212
 213     /* Pointer to the version information if available.  */
 214     ElfW(Versym) *l_versyms;
 215
 216     /* String specifying the path where this object was found.  */
 217     const char *l_origin;
 218
 219     /* Start and finish of memory map for this object.  l_map_start
 220        need not be the same as l_addr.  */
 221     ElfW(Addr) l_map_start, l_map_end;
 222     /* End of the executable part of the mapping.  */
 223     ElfW(Addr) l_text_end;
 224
 225     /* Default array for 'l_scope'.  */
 226     struct r_scope_elem *l_scope_mem[4];
 227     /* Size of array allocated for 'l_scope'.  */
 228     size_t l_scope_max;
 229     /* This is an array defining the lookup scope for this link map.
 230        There are initially at most three different scope lists.  */
 231     struct r_scope_elem **l_scope;
 232
 233     /* A similar array, this time only with the local scope.  This is
 234        used occasionally.  */
 235     struct r_scope_elem *l_local_scope[2];
 236
 237     /* This information is kept to check for sure whether a shared
 238        object is the same as one already loaded.  */
 239     struct r_file_id l_file_id;
 240
 241     /* Collected information about own RUNPATH directories.  */
 242     struct r_search_path_struct l_runpath_dirs;
 243
 244     /* List of object in order of the init and fini calls.  */
 245     struct link_map **l_initfini;
 246
 247     /* List of the dependencies introduced through symbol binding.  */
 248     struct link_map_reldeps
 249       {
 250         unsigned int act;
 251         struct link_map *list[];
 252       } *l_reldeps;
 253     unsigned int l_reldepsmax;
 254
 255     /* Nonzero if the DSO is used.  */
 256     unsigned int l_used;
 257
 258     /* Various flag words.  */
 259     ElfW(Word) l_feature_1;
 260     ElfW(Word) l_flags_1;
 261     ElfW(Word) l_flags;
 262
 263     /* Temporarily used in `dl_close'.  */
 264     int l_idx;
 265
 266     struct link_map_machine l_mach;
 267
 268     struct
 269     {
 270       const ElfW(Sym) *sym;
 271       int type_class;
 272       struct link_map *value;
 273       const ElfW(Sym) *ret;
 274     } l_lookup_cache;
 275
 276     /* Thread-local storage related info.  */
 277
 278     /* Start of the initialization image.  */
 279     void *l_tls_initimage;
 280     /* Size of the initialization image.  */
 281     size_t l_tls_initimage_size;
 282     /* Size of the TLS block.  */
 283     size_t l_tls_blocksize;
 284     /* Alignment requirement of the TLS block.  */
 285     size_t l_tls_align;
 286     /* Offset of first byte module alignment.  */
 287     size_t l_tls_firstbyte_offset;
 288 #ifndef NO_TLS_OFFSET
 289 # define NO_TLS_OFFSET  0
 290 #endif
 291 #ifndef FORCED_DYNAMIC_TLS_OFFSET
 292 # if NO_TLS_OFFSET == 0
 293 #  define FORCED_DYNAMIC_TLS_OFFSET -1
 294 # elif NO_TLS_OFFSET == -1
 295 #  define FORCED_DYNAMIC_TLS_OFFSET -2
 296 # else
 297 #  error "FORCED_DYNAMIC_TLS_OFFSET is not defined"
 298 # endif
 299 #endif
 300     /* For objects present at startup time: offset in the static TLS block.  */
 301     ptrdiff_t l_tls_offset;
 302     /* Index of the module in the dtv array.  */
 303     size_t l_tls_modid;
 304
 305     /* Number of thread_local objects constructed by this DSO.  This is
 306        atomically accessed and modified and is not always protected by the load
 307        lock.  See also: CONCURRENCY NOTES in cxa_thread_atexit_impl.c.  */
 308     size_t l_tls_dtor_count;
 309
 310     /* Information used to change permission after the relocations are
 311        done.  */
 312     ElfW(Addr) l_relro_addr;
 313     size_t l_relro_size;
 314
 315     unsigned long long int l_serial;
 316
 317     /* Audit information.  This array apparent must be the last in the
 318        structure.  Never add something after it.  */
 319     struct auditstate
 320     {
 321       uintptr_t cookie;
 322       unsigned int bindflags;
 323     } l_audit[0];
 324   };
 325
 326
 327 #if __ELF_NATIVE_CLASS == 32
 328 # define symbind symbind32
 329 #elif __ELF_NATIVE_CLASS == 64
 330 # define symbind symbind64
 331 #else
 332 # error "__ELF_NATIVE_CLASS must be defined"
 333 #endif
 334
 335 extern int __dl_iterate_phdr (int (*callback) (struct dl_phdr_info *info,
 336                                                size_t size, void *data),
 337                               void *data);
 338
 339 /* We use this macro to refer to ELF macros independent of the native
 340    wordsize.  `ELFW(R_TYPE)' is used in place of `ELF32_R_TYPE' or
 341    `ELF64_R_TYPE'.  */
 342 #define ELFW(type)      _ElfW (ELF, __ELF_NATIVE_CLASS, type)
 343
 344 #endif /* include/link.h */