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