include/link.h

   1 /* Data structure for communication from the run-time dynamic linker for
   2    loaded ELF shared objects.
   3    Copyright (C) 1995-2002,2003,2004,2005,2006 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 _PRIVATE_LINK_H
  22 #define _PRIVATE_LINK_H 1
  23
  24 #ifdef _LINK_H
  25 # error this should be impossible
  26 #endif
  27
  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 #include <elf/link.h>
  34 #undef  link_map
  35 #undef  la_objopen
  36
  37 struct link_map;
  38 extern unsigned int la_objopen (struct link_map *__map, Lmid_t __lmid,
  39                                 uintptr_t *__cookie);
  40
  41
  42 #include <stddef.h>
  43 #include <bits/linkmap.h>
  44 #include <dl-lookupcfg.h>
  45 #include <tls.h>                /* Defines USE_TLS.  */
  46
  47
  48 /* Some internal data structures of the dynamic linker used in the
  49    linker map.  We only provide forward declarations.  */
  50 struct libname_list;
  51 struct r_found_version;
  52 struct r_search_path_elem;
  53
  54 /* Forward declaration.  */
  55 struct link_map;
  56
  57 /* Structure to describe a single list of scope elements.  The lookup
  58    functions get passed an array of pointers to such structures.  */
  59 struct r_scope_elem
  60 {
  61   /* Array of maps for the scope.  */
  62   struct link_map **r_list;
  63   /* Number of entries in the scope.  */
  64   unsigned int r_nlist;
  65 };
  66
  67
  68 /* Structure to record search path and allocation mechanism.  */
  69 struct r_search_path_struct
  70   {
  71     struct r_search_path_elem **dirs;
  72     int malloced;
  73   };
  74
  75
  76 /* Structure describing a loaded shared object.  The `l_next' and `l_prev'
  77    members form a chain of all the shared objects loaded at startup.
  78
  79    These data structures exist in space used by the run-time dynamic linker;
  80    modifying them may have disastrous results.
  81
  82    This data structure might change in future, if necessary.  User-level
  83    programs must avoid defining objects of this type.  */
  84
  85 struct link_map
  86   {
  87     /* These first few members are part of the protocol with the debugger.
  88        This is the same format used in SVR4.  */
  89
  90     ElfW(Addr) l_addr;          /* Base address shared object is loaded at.  */
  91     char *l_name;               /* Absolute file name object was found in.  */
  92     ElfW(Dyn) *l_ld;            /* Dynamic section of the shared object.  */
  93     struct link_map *l_next, *l_prev; /* Chain of loaded objects.  */
  94
  95     /* All following members are internal to the dynamic linker.
  96        They may change without notice.  */
  97
  98     /* This is an element which is only ever different from a pointer to
  99        the very same copy of this type for ld.so when it is used in more
 100        than one namespace.  */
 101     struct link_map *l_real;
 102
 103     /* Number of the namespace this link map belongs to.  */
 104     Lmid_t l_ns;
 105
 106     struct libname_list *l_libname;
 107     /* Indexed pointers to dynamic section.
 108        [0,DT_NUM) are indexed by the processor-independent tags.
 109        [DT_NUM,DT_NUM+DT_THISPROCNUM) are indexed by the tag minus DT_LOPROC.
 110        [DT_NUM+DT_THISPROCNUM,DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM) are
 111        indexed by DT_VERSIONTAGIDX(tagvalue).
 112        [DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM,
 113         DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM) are indexed by
 114        DT_EXTRATAGIDX(tagvalue).
 115        [DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM,
 116         DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM+DT_VALNUM) are
 117        indexed by DT_VALTAGIDX(tagvalue) and
 118        [DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM+DT_VALNUM,
 119         DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM+DT_VALNUM+DT_ADDRNUM)
 120        are indexed by DT_ADDRTAGIDX(tagvalue), see <elf.h>.  */
 121
 122     ElfW(Dyn) *l_info[DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGNUM
 123                      + DT_EXTRANUM + DT_VALNUM + DT_ADDRNUM];
 124     const ElfW(Phdr) *l_phdr;   /* Pointer to program header table in core.  */
 125     ElfW(Addr) l_entry;         /* Entry point location.  */
 126     ElfW(Half) l_phnum;         /* Number of program header entries.  */
 127     ElfW(Half) l_ldnum; /* Number of dynamic segment entries.  */
 128
 129     /* Array of DT_NEEDED dependencies and their dependencies, in
 130        dependency order for symbol lookup (with and without
 131        duplicates).  There is no entry before the dependencies have
 132        been loaded.  */
 133     struct r_scope_elem l_searchlist;
 134
 135     /* We need a special searchlist to process objects marked with
 136        DT_SYMBOLIC.  */
 137     struct r_scope_elem l_symbolic_searchlist;
 138
 139     /* Dependent object that first caused this object to be loaded.  */
 140     struct link_map *l_loader;
 141
 142     /* Symbol hash table.  */
 143     Elf_Symndx l_nbuckets;
 144     const Elf_Symndx *l_buckets, *l_chain;
 145
 146     unsigned int l_direct_opencount; /* Reference count for dlopen/dlclose.  */
 147     enum                        /* Where this object came from.  */
 148       {
 149         lt_executable,          /* The main executable program.  */
 150         lt_library,             /* Library needed by main executable.  */
 151         lt_loaded               /* Extra run-time loaded shared object.  */
 152       } l_type:2;
 153     unsigned int l_relocated:1; /* Nonzero if object's relocations done.  */
 154     unsigned int l_init_called:1; /* Nonzero if DT_INIT function called.  */
 155     unsigned int l_global:1;    /* Nonzero if object in _dl_global_scope.  */
 156     unsigned int l_reserved:2;  /* Reserved for internal use.  */
 157     unsigned int l_phdr_allocated:1; /* Nonzero if the data structure pointed
 158                                         to by `l_phdr' is allocated.  */
 159     unsigned int l_soname_added:1; /* Nonzero if the SONAME is for sure in
 160                                       the l_libname list.  */
 161     unsigned int l_faked:1;     /* Nonzero if this is a faked descriptor
 162                                    without associated file.  */
 163     unsigned int l_need_tls_init:1; /* Nonzero if GL(dl_init_static_tls)
 164                                        should be called on this link map
 165                                        when relocation finishes.  */
 166     unsigned int l_used:1;      /* Nonzero if the DSO is used.  */
 167     unsigned int l_auditing:1;  /* Nonzero if the DSO is used in auditing.  */
 168     unsigned int l_audit_any_plt:1; /* Nonzero if at least one audit module
 169                                        is interested in the PLT interception.*/
 170     unsigned int l_removed:1;   /* Nozero if the object cannot be used anymore
 171                                    since it is removed.  */
 172
 173     /* Array with version names.  */
 174     unsigned int l_nversions;
 175     struct r_found_version *l_versions;
 176
 177     /* Collected information about own RPATH directories.  */
 178     struct r_search_path_struct l_rpath_dirs;
 179
 180     /* Collected results of relocation while profiling.  */
 181     struct reloc_result
 182     {
 183       DL_FIXUP_VALUE_TYPE addr;
 184       struct link_map *bound;
 185       unsigned int boundndx;
 186       uint32_t enterexit;
 187       unsigned int flags;
 188     } *l_reloc_result;
 189
 190     /* Pointer to the version information if available.  */
 191     ElfW(Versym) *l_versyms;
 192
 193     /* String specifying the path where this object was found.  */
 194     const char *l_origin;
 195
 196     /* Start and finish of memory map for this object.  l_map_start
 197        need not be the same as l_addr.  */
 198     ElfW(Addr) l_map_start, l_map_end;
 199     /* End of the executable part of the mapping.  */
 200     ElfW(Addr) l_text_end;
 201
 202     /* Default array for 'l_scope'.  */
 203     struct r_scope_elem *l_scope_mem[4];
 204     /* Size of array allocated for 'l_scope'.  */
 205     size_t l_scope_max;
 206     /* This is an array defining the lookup scope for this link map.
 207        There are at most three different scope lists.  */
 208     struct r_scope_elem **l_scope;
 209
 210     /* A similar array, this time only with the local scope.  This is
 211        used occasionally.  */
 212     struct r_scope_elem *l_local_scope[2];
 213
 214     /* This information is kept to check for sure whether a shared
 215        object is the same as one already loaded.  */
 216     dev_t l_dev;
 217     ino64_t l_ino;
 218
 219     /* Collected information about own RUNPATH directories.  */
 220     struct r_search_path_struct l_runpath_dirs;
 221
 222     /* List of object in order of the init and fini calls.  */
 223     struct link_map **l_initfini;
 224
 225     /* List of the dependencies introduced through symbol binding.  */
 226     unsigned int l_reldepsmax;
 227     unsigned int l_reldepsact;
 228     struct link_map **l_reldeps;
 229
 230     /* Various flag words.  */
 231     ElfW(Word) l_feature_1;
 232     ElfW(Word) l_flags_1;
 233     ElfW(Word) l_flags;
 234
 235     /* Temporarily used in `dl_close'.  */
 236     int l_idx;
 237
 238     struct link_map_machine l_mach;
 239
 240     struct
 241     {
 242       const ElfW(Sym) *sym;
 243       int type_class;
 244       struct link_map *value;
 245       const ElfW(Sym) *ret;
 246     } l_lookup_cache;
 247
 248 #ifdef USE_TLS
 249     /* Thread-local storage related info.  */
 250
 251     /* Start of the initialization image.  */
 252     void *l_tls_initimage;
 253     /* Size of the initialization image.  */
 254     size_t l_tls_initimage_size;
 255     /* Size of the TLS block.  */
 256     size_t l_tls_blocksize;
 257     /* Alignment requirement of the TLS block.  */
 258     size_t l_tls_align;
 259     /* Offset of first byte module alignment.  */
 260     size_t l_tls_firstbyte_offset;
 261 # ifndef NO_TLS_OFFSET
 262 #  define NO_TLS_OFFSET 0
 263 # endif
 264     /* For objects present at startup time: offset in the static TLS block.  */
 265     ptrdiff_t l_tls_offset;
 266     /* Index of the module in the dtv array.  */
 267     size_t l_tls_modid;
 268 #endif
 269
 270     /* Information used to change permission after the relocations are
 271        done.  */
 272     ElfW(Addr) l_relro_addr;
 273     size_t l_relro_size;
 274
 275     /* Audit information.  This array apparent must be the last in the
 276        structure.  Never add something after it.  */
 277     struct auditstate
 278     {
 279       uintptr_t cookie;
 280       unsigned int bindflags;
 281     } l_audit[0];
 282   };
 283
 284
 285 #if __ELF_NATIVE_CLASS == 32
 286 # define symbind symbind32
 287 #elif __ELF_NATIVE_CLASS == 64
 288 # define symbind symbind64
 289 #else
 290 # error "__ELF_NATIVE_CLASS must be defined"
 291 #endif
 292
 293 extern int __dl_iterate_phdr (int (*callback) (struct dl_phdr_info *info,
 294                                                size_t size, void *data),
 295                               void *data);
 296
 297 #endif /* include/link.h */