include/link.h

   1 /* Data structure for communication from the run-time dynamic linker for
   2    loaded ELF shared objects.
   3    Copyright (C) 1995-2017 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 # ifndef _ISOMAC
  28 /* Get most of the contents from the public header, but we define a
  29    different `struct link_map' type for private use.  The la_objopen
  30    prototype uses the type, so we have to declare it separately.  */
  31 #  define link_map      link_map_public
  32 #  define la_objopen    la_objopen_wrongproto
  33 # endif
  34
  35 #include <elf/link.h>
  36
  37 # ifndef _ISOMAC
  38
  39 #undef  link_map
  40 #undef  la_objopen
  41
  42 struct link_map;
  43 extern unsigned int la_objopen (struct link_map *__map, Lmid_t __lmid,
  44                                 uintptr_t *__cookie);
  45
  46 #include <stdint.h>
  47 #include <stddef.h>
  48 #include <linkmap.h>
  49 #include <dl-fileid.h>
  50 #include <dl-lookupcfg.h>
  51 #include <tls.h>
  52 #include <libc-lock.h>
  53
  54
  55 /* Some internal data structures of the dynamic linker used in the
  56    linker map.  We only provide forward declarations.  */
  57 struct libname_list;
  58 struct r_found_version;
  59 struct r_search_path_elem;
  60
  61 /* Forward declaration.  */
  62 struct link_map;
  63
  64 /* Structure to describe a single list of scope elements.  The lookup
  65    functions get passed an array of pointers to such structures.  */
  66 struct r_scope_elem
  67 {
  68   /* Array of maps for the scope.  */
  69   struct link_map **r_list;
  70   /* Number of entries in the scope.  */
  71   unsigned int r_nlist;
  72 };
  73
  74
  75 /* Structure to record search path and allocation mechanism.  */
  76 struct r_search_path_struct
  77   {
  78     struct r_search_path_elem **dirs;
  79     int malloced;
  80   };
  81
  82
  83 /* Structure describing a loaded shared object.  The `l_next' and `l_prev'
  84    members form a chain of all the shared objects loaded at startup.
  85
  86    These data structures exist in space used by the run-time dynamic linker;
  87    modifying them may have disastrous results.
  88
  89    This data structure might change in future, if necessary.  User-level
  90    programs must avoid defining objects of this type.  */
  91
  92 struct link_map
  93   {
  94     /* These first few members are part of the protocol with the debugger.
  95        This is the same format used in SVR4.  */
  96
  97     ElfW(Addr) l_addr;          /* Difference between the address in the ELF
  98                                    file and the addresses in memory.  */
  99     char *l_name;               /* Absolute file name object was found in.  */
 100     ElfW(Dyn) *l_ld;            /* Dynamic section of the shared object.  */
 101     struct link_map *l_next, *l_prev; /* Chain of loaded objects.  */
 102
 103     /* All following members are internal to the dynamic linker.
 104        They may change without notice.  */
 105
 106     /* This is an element which is only ever different from a pointer to
 107        the very same copy of this type for ld.so when it is used in more
 108        than one namespace.  */
 109     struct link_map *l_real;
 110
 111     /* Number of the namespace this link map belongs to.  */
 112     Lmid_t l_ns;
 113
 114     struct libname_list *l_libname;
 115     /* Indexed pointers to dynamic section.
 116        [0,DT_NUM) are indexed by the processor-independent tags.
 117        [DT_NUM,DT_NUM+DT_THISPROCNUM) are indexed by the tag minus DT_LOPROC.
 118        [DT_NUM+DT_THISPROCNUM,DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM) are
 119        indexed by DT_VERSIONTAGIDX(tagvalue).
 120        [DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM,
 121         DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM) are indexed by
 122        DT_EXTRATAGIDX(tagvalue).
 123        [DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM,
 124         DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM+DT_VALNUM) are
 125        indexed by DT_VALTAGIDX(tagvalue) and
 126        [DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM+DT_VALNUM,
 127         DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM+DT_VALNUM+DT_ADDRNUM)
 128        are indexed by DT_ADDRTAGIDX(tagvalue), see <elf.h>.  */
 129
 130     ElfW(Dyn) *l_info[DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGNUM
 131                       + DT_EXTRANUM + DT_VALNUM + DT_ADDRNUM];
 132     const ElfW(Phdr) *l_phdr;   /* Pointer to program header table in core.  */
 133     ElfW(Addr) l_entry;         /* Entry point location.  */
 134     ElfW(Half) l_phnum;         /* Number of program header entries.  */
 135     ElfW(Half) l_ldnum;         /* Number of dynamic segment entries.  */
 136
 137     /* Array of DT_NEEDED dependencies and their dependencies, in
 138        dependency order for symbol lookup (with and without
 139        duplicates).  There is no entry before the dependencies have
 140        been loaded.  */
 141     struct r_scope_elem l_searchlist;
 142
 143     /* We need a special searchlist to process objects marked with
 144        DT_SYMBOLIC.  */
 145     struct r_scope_elem l_symbolic_searchlist;
 146
 147     /* Dependent object that first caused this object to be loaded.  */
 148     struct link_map *l_loader;
 149
 150     /* Array with version names.  */
 151     struct r_found_version *l_versions;
 152     unsigned int l_nversions;
 153
 154     /* Symbol hash table.  */
 155     Elf_Symndx l_nbuckets;
 156     Elf32_Word l_gnu_bitmask_idxbits;
 157     Elf32_Word l_gnu_shift;
 158     const ElfW(Addr) *l_gnu_bitmask;
 159     union
 160     {
 161       const Elf32_Word *l_gnu_buckets;
 162       const Elf_Symndx *l_chain;
 163     };
 164     union
 165     {
 166       const Elf32_Word *l_gnu_chain_zero;
 167       const Elf_Symndx *l_buckets;
 168     };
 169
 170     unsigned int l_direct_opencount; /* Reference count for dlopen/dlclose.  */
 171     enum                        /* Where this object came from.  */
 172       {
 173         lt_executable,          /* The main executable program.  */
 174         lt_library,             /* Library needed by main executable.  */
 175         lt_loaded               /* Extra run-time loaded shared object.  */
 176       } l_type:2;
 177     unsigned int l_relocated:1; /* Nonzero if object's relocations done.  */
 178     unsigned int l_init_called:1; /* Nonzero if DT_INIT function called.  */
 179     unsigned int l_global:1;    /* Nonzero if object in _dl_global_scope.  */
 180     unsigned int l_reserved:2;  /* Reserved for internal use.  */
 181     unsigned int l_phdr_allocated:1; /* Nonzero if the data structure pointed
 182                                         to by `l_phdr' is allocated.  */
 183     unsigned int l_soname_added:1; /* Nonzero if the SONAME is for sure in
 184                                       the l_libname list.  */
 185     unsigned int l_faked:1;     /* Nonzero if this is a faked descriptor
 186                                    without associated file.  */
 187     unsigned int l_need_tls_init:1; /* Nonzero if GL(dl_init_static_tls)
 188                                        should be called on this link map
 189                                        when relocation finishes.  */
 190     unsigned int l_auditing:1;  /* Nonzero if the DSO is used in auditing.  */
 191     unsigned int l_audit_any_plt:1; /* Nonzero if at least one audit module
 192                                        is interested in the PLT interception.*/
 193     unsigned int l_removed:1;   /* Nozero if the object cannot be used anymore
 194                                    since it is removed.  */
 195     unsigned int l_contiguous:1; /* Nonzero if inter-segment holes are
 196                                     mprotected or if no holes are present at
 197                                     all.  */
 198     unsigned int l_symbolic_in_local_scope:1; /* Nonzero if l_local_scope
 199                                                  during LD_TRACE_PRELINKING=1
 200                                                  contains any DT_SYMBOLIC
 201                                                  libraries.  */
 202     unsigned int l_free_initfini:1; /* Nonzero if l_initfini can be
 203                                        freed, ie. not allocated with
 204                                        the dummy malloc in ld.so.  */
 205
 206 #include <link_map.h>
 207
 208     /* Collected information about own RPATH directories.  */
 209     struct r_search_path_struct l_rpath_dirs;
 210
 211     /* Collected results of relocation while profiling.  */
 212     struct reloc_result
 213     {
 214       DL_FIXUP_VALUE_TYPE addr;
 215       struct link_map *bound;
 216       unsigned int boundndx;
 217       uint32_t enterexit;
 218       unsigned int flags;
 219     } *l_reloc_result;
 220
 221     /* Pointer to the version information if available.  */
 222     ElfW(Versym) *l_versyms;
 223
 224     /* String specifying the path where this object was found.  */
 225     const char *l_origin;
 226
 227     /* Start and finish of memory map for this object.  l_map_start
 228        need not be the same as l_addr.  */
 229     ElfW(Addr) l_map_start, l_map_end;
 230     /* End of the executable part of the mapping.  */
 231     ElfW(Addr) l_text_end;
 232
 233     /* Default array for 'l_scope'.  */
 234     struct r_scope_elem *l_scope_mem[4];
 235     /* Size of array allocated for 'l_scope'.  */
 236     size_t l_scope_max;
 237     /* This is an array defining the lookup scope for this link map.
 238        There are initially at most three different scope lists.  */
 239     struct r_scope_elem **l_scope;
 240
 241     /* A similar array, this time only with the local scope.  This is
 242        used occasionally.  */
 243     struct r_scope_elem *l_local_scope[2];
 244
 245     /* This information is kept to check for sure whether a shared
 246        object is the same as one already loaded.  */
 247     struct r_file_id l_file_id;
 248
 249     /* Collected information about own RUNPATH directories.  */
 250     struct r_search_path_struct l_runpath_dirs;
 251
 252     /* List of object in order of the init and fini calls.  */
 253     struct link_map **l_initfini;
 254
 255     /* List of the dependencies introduced through symbol binding.  */
 256     struct link_map_reldeps
 257       {
 258         unsigned int act;
 259         struct link_map *list[];
 260       } *l_reldeps;
 261     unsigned int l_reldepsmax;
 262
 263     /* Nonzero if the DSO is used.  */
 264     unsigned int l_used;
 265
 266     /* Various flag words.  */
 267     ElfW(Word) l_feature_1;
 268     ElfW(Word) l_flags_1;
 269     ElfW(Word) l_flags;
 270
 271     /* Temporarily used in `dl_close'.  */
 272     int l_idx;
 273
 274     struct link_map_machine l_mach;
 275
 276     struct
 277     {
 278       const ElfW(Sym) *sym;
 279       int type_class;
 280       struct link_map *value;
 281       const ElfW(Sym) *ret;
 282     } l_lookup_cache;
 283
 284     /* Thread-local storage related info.  */
 285
 286     /* Start of the initialization image.  */
 287     void *l_tls_initimage;
 288     /* Size of the initialization image.  */
 289     size_t l_tls_initimage_size;
 290     /* Size of the TLS block.  */
 291     size_t l_tls_blocksize;
 292     /* Alignment requirement of the TLS block.  */
 293     size_t l_tls_align;
 294     /* Offset of first byte module alignment.  */
 295     size_t l_tls_firstbyte_offset;
 296 #ifndef NO_TLS_OFFSET
 297 # define NO_TLS_OFFSET  0
 298 #endif
 299 #ifndef FORCED_DYNAMIC_TLS_OFFSET
 300 # if NO_TLS_OFFSET == 0
 301 #  define FORCED_DYNAMIC_TLS_OFFSET -1
 302 # elif NO_TLS_OFFSET == -1
 303 #  define FORCED_DYNAMIC_TLS_OFFSET -2
 304 # else
 305 #  error "FORCED_DYNAMIC_TLS_OFFSET is not defined"
 306 # endif
 307 #endif
 308     /* For objects present at startup time: offset in the static TLS block.  */
 309     ptrdiff_t l_tls_offset;
 310     /* Index of the module in the dtv array.  */
 311     size_t l_tls_modid;
 312
 313     /* Number of thread_local objects constructed by this DSO.  This is
 314        atomically accessed and modified and is not always protected by the load
 315        lock.  See also: CONCURRENCY NOTES in cxa_thread_atexit_impl.c.  */
 316     size_t l_tls_dtor_count;
 317
 318     /* Information used to change permission after the relocations are
 319        done.  */
 320     ElfW(Addr) l_relro_addr;
 321     size_t l_relro_size;
 322
 323     unsigned long long int l_serial;
 324
 325     /* Audit information.  This array apparent must be the last in the
 326        structure.  Never add something after it.  */
 327     struct auditstate
 328     {
 329       uintptr_t cookie;
 330       unsigned int bindflags;
 331     } l_audit[0];
 332   };
 333
 334
 335 #if __ELF_NATIVE_CLASS == 32
 336 # define symbind symbind32
 337 #elif __ELF_NATIVE_CLASS == 64
 338 # define symbind symbind64
 339 #else
 340 # error "__ELF_NATIVE_CLASS must be defined"
 341 #endif
 342
 343 extern int __dl_iterate_phdr (int (*callback) (struct dl_phdr_info *info,
 344                                                size_t size, void *data),
 345                               void *data);
 346 hidden_proto (__dl_iterate_phdr)
 347
 348 /* We use this macro to refer to ELF macros independent of the native
 349    wordsize.  `ELFW(R_TYPE)' is used in place of `ELF32_R_TYPE' or
 350    `ELF64_R_TYPE'.  */
 351 #define ELFW(type)      _ElfW (ELF, __ELF_NATIVE_CLASS, type)
 352
 353 # endif /* !_ISOMAC */
 354 #endif /* include/link.h */