include/link.h

   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, 2010 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 _LINK_H
  21 #define _LINK_H 1
  22
  23 #include <features.h>
  24 #include <elf.h>
  25 #ifdef __HAVE_SHARED__
  26 #include <dlfcn.h>
  27 #endif
  28 #include <sys/types.h>
  29 #if defined _LIBC && defined __UCLIBC_HAS_TLS__
  30 #include <tls.h>
  31 #endif
  32
  33 /* We use this macro to refer to ELF types independent of the native wordsize.
  34    `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'.  */
  35 #define ElfW(type)      _ElfW (Elf, __ELF_NATIVE_CLASS, type)
  36 #define _ElfW(e,w,t)    _ElfW_1 (e, w, _##t)
  37 #define _ElfW_1(e,w,t)  e##w##t
  38
  39 #include <bits/elfclass.h>              /* Defines __ELF_NATIVE_CLASS.  */
  40
  41 /* Rendezvous structure used by the run-time dynamic linker to communicate
  42    details of shared object loading to the debugger.  If the executable's
  43    dynamic section has a DT_DEBUG element, the run-time linker sets that
  44    element's value to the address where this structure can be found.  */
  45
  46 struct r_debug
  47   {
  48     int r_version;              /* Version number for this protocol.  */
  49
  50     struct link_map *r_map;     /* Head of the chain of loaded objects.  */
  51
  52     /* This is the address of a function internal to the run-time linker,
  53        that will always be called when the linker begins to map in a
  54        library or unmap it, and again when the mapping change is complete.
  55        The debugger can set a breakpoint at this address if it wants to
  56        notice shared object mapping changes.  */
  57     ElfW(Addr) r_brk;
  58     enum
  59       {
  60         /* This state value describes the mapping change taking place when
  61            the `r_brk' address is called.  */
  62         RT_CONSISTENT,          /* Mapping change is complete.  */
  63         RT_ADD,                 /* Beginning to add a new object.  */
  64         RT_DELETE               /* Beginning to remove an object mapping.  */
  65       } r_state;
  66
  67     ElfW(Addr) r_ldbase;        /* Base address the linker is loaded at.  */
  68   };
  69
  70 /* This is the instance of that structure used by the dynamic linker.  */
  71 extern struct r_debug _r_debug;
  72
  73 /* This symbol refers to the "dynamic structure" in the `.dynamic' section
  74    of whatever module refers to `_DYNAMIC'.  So, to find its own
  75    `struct r_debug', a program could do:
  76      for (dyn = _DYNAMIC; dyn->d_tag != DT_NULL; ++dyn)
  77        if (dyn->d_tag == DT_DEBUG)
  78          r_debug = (struct r_debug *) dyn->d_un.d_ptr;
  79    */
  80 extern ElfW(Dyn) _DYNAMIC[];
  81
  82 #ifdef __FDPIC__
  83 # include <bits/elf-fdpic.h>
  84 #endif
  85 #ifdef __DSBT__
  86 # include <bits/elf-dsbt.h>
  87 #endif
  88
  89 /* Structure describing a loaded shared object.  The `l_next' and `l_prev'
  90    members form a chain of all the shared objects loaded at startup.
  91
  92    These data structures exist in space used by the run-time dynamic linker;
  93    modifying them may have disastrous results.  */
  94
  95 struct link_map
  96   {
  97     /* These first few members are part of the protocol with the debugger.
  98        This is the same format used in SVR4.  */
  99
 100 #ifdef __FDPIC__
 101     struct elf32_fdpic_loadaddr l_addr;
 102 #else
 103 #ifdef __DSBT__
 104     struct elf32_dsbt_loadaddr l_addr;
 105 #else
 106     ElfW(Addr) l_addr;          /* Base address shared object is loaded at.  */
 107 #endif
 108 #endif
 109     char *l_name;               /* Absolute file name object was found in.  */
 110     ElfW(Dyn) *l_ld;            /* Dynamic section of the shared object.  */
 111     struct link_map *l_next, *l_prev; /* Chain of loaded objects.  */
 112 #ifdef _LIBC
 113 #if defined(USE_TLS) && USE_TLS
 114     /* Thread-local storage related info.  */
 115
 116     /* Start of the initialization image.  */
 117     void *l_tls_initimage;
 118     /* Size of the initialization image.  */
 119     size_t l_tls_initimage_size;
 120     /* Size of the TLS block.  */
 121     size_t l_tls_blocksize;
 122     /* Alignment requirement of the TLS block.  */
 123     size_t l_tls_align;
 124     /* Offset of first byte module alignment.  */
 125     size_t l_tls_firstbyte_offset;
 126 # ifndef NO_TLS_OFFSET
 127 #  define NO_TLS_OFFSET 0
 128 # endif
 129     /* For objects present at startup time: offset in the static TLS block.  */
 130     ptrdiff_t l_tls_offset;
 131     /* Index of the module in the dtv array.  */
 132     size_t l_tls_modid;
 133     /* Nonzero if _dl_init_static_tls should be called for this module */
 134     unsigned int l_need_tls_init:1;
 135     /* Address of TLS descriptor hash table.  */
 136     void *l_tlsdesc_table;
 137 #endif
 138 #endif
 139   };
 140
 141 #ifdef __USE_GNU
 142
 143 #if 0
 144 /* Version numbers for la_version handshake interface.  */
 145 #define LAV_CURRENT     1
 146
 147 /* Activity types signaled through la_activity.  */
 148 enum
 149   {
 150     LA_ACT_CONSISTENT,          /* Link map consistent again.  */
 151     LA_ACT_ADD,                 /* New object will be added.  */
 152     LA_ACT_DELETE               /* Objects will be removed.  */
 153   };
 154
 155 /* Values representing origin of name for dynamic loading.  */
 156 enum
 157   {
 158     LA_SER_ORIG = 0x01,         /* Original name.  */
 159     LA_SER_LIBPATH = 0x02,      /* Directory from LD_LIBRARY_PATH.  */
 160     LA_SER_RUNPATH = 0x04,      /* Directory from RPATH/RUNPATH.  */
 161     LA_SER_CONFIG = 0x08,       /* Found through ldconfig.  */
 162     LA_SER_DEFAULT = 0x40,      /* Default directory.  */
 163     LA_SER_SECURE = 0x80        /* Unused.  */
 164   };
 165
 166 /* Values for la_objopen return value.  */
 167 enum
 168   {
 169     LA_FLG_BINDTO = 0x01,       /* Audit symbols bound to this object.  */
 170     LA_FLG_BINDFROM = 0x02      /* Audit symbols bound from this object.  */
 171   };
 172
 173 /* Values for la_symbind flags parameter.  */
 174 enum
 175   {
 176     LA_SYMB_NOPLTENTER = 0x01,  /* la_pltenter will not be called.  */
 177     LA_SYMB_NOPLTEXIT = 0x02,   /* la_pltexit will not be called.  */
 178     LA_SYMB_STRUCTCALL = 0x04,  /* Return value is a structure.  */
 179     LA_SYMB_DLSYM = 0x08,       /* Binding due to dlsym call.  */
 180     LA_SYMB_ALTVALUE = 0x10     /* Value has been changed by a previous
 181                                    la_symbind call.  */
 182   };
 183 #endif
 184
 185 struct dl_phdr_info
 186   {
 187 #ifdef __FDPIC__
 188     struct elf32_fdpic_loadaddr dlpi_addr;
 189 #else
 190 #ifdef __DSBT__
 191     struct elf32_dsbt_loadaddr dlpi_addr;
 192 #else
 193     ElfW(Addr) dlpi_addr;
 194 #endif
 195 #endif
 196     const char *dlpi_name;
 197     const ElfW(Phdr) *dlpi_phdr;
 198     ElfW(Half) dlpi_phnum;
 199
 200 #if 0
 201     /* Note: Following members were introduced after the first
 202        version of this structure was available.  Check the SIZE
 203        argument passed to the dl_iterate_phdr callback to determine
 204        whether or not each later member is available.  */
 205
 206     /* Incremented when a new object may have been added.  */
 207     unsigned long long int dlpi_adds;
 208     /* Incremented when an object may have been removed.  */
 209     unsigned long long int dlpi_subs;
 210
 211     /* If there is a PT_TLS segment, its module ID as used in
 212        TLS relocations, else zero.  */
 213     size_t dlpi_tls_modid;
 214
 215     /* The address of the calling thread's instance of this module's
 216        PT_TLS segment, if it has one and it has been allocated
 217        in the calling thread, otherwise a null pointer.  */
 218     void *dlpi_tls_data;
 219 #endif
 220   };
 221
 222 __BEGIN_DECLS
 223
 224 extern int dl_iterate_phdr (int (*__callback) (struct dl_phdr_info *,
 225                                                size_t, void *),
 226                             void *__data);
 227
 228
 229 #if 0
 230 /* Prototypes for the ld.so auditing interfaces.  These are not
 231    defined anywhere in ld.so but instead have to be provided by the
 232    auditing DSO.  */
 233 extern unsigned int la_version (unsigned int __version);
 234 extern void la_activity (uintptr_t *__cookie, unsigned int __flag);
 235 extern char *la_objsearch (const char *__name, uintptr_t *__cookie,
 236                            unsigned int __flag);
 237 extern unsigned int la_objopen (struct link_map *__map, Lmid_t __lmid,
 238                                 uintptr_t *__cookie);
 239 extern void la_preinit (uintptr_t *__cookie);
 240 extern uintptr_t la_symbind32 (Elf32_Sym *__sym, unsigned int __ndx,
 241                                uintptr_t *__refcook, uintptr_t *__defcook,
 242                                unsigned int *__flags, const char *__symname);
 243 extern uintptr_t la_symbind64 (Elf64_Sym *__sym, unsigned int __ndx,
 244                                uintptr_t *__refcook, uintptr_t *__defcook,
 245                                unsigned int *__flags, const char *__symname);
 246 extern unsigned int la_objclose (uintptr_t *__cookie);
 247 #endif
 248
 249 __END_DECLS
 250
 251 #endif
 252
 253 #endif /* link.h */