elf/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 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 #include <dlfcn.h>
  27 #include <sys/types.h>
  28
  29 /* We use this macro to refer to ELF types independent of the native wordsize.
  30    `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'.  */
  31 #define ElfW(type)      _ElfW (Elf, __ELF_NATIVE_CLASS, type)
  32 #define _ElfW(e,w,t)    _ElfW_1 (e, w, _##t)
  33 #define _ElfW_1(e,w,t)  e##w##t
  34
  35 #include <bits/elfclass.h>              /* Defines __ELF_NATIVE_CLASS.  */
  36 #include <bits/link.h>
  37
  38 /* Rendezvous structure used by the run-time dynamic linker to communicate
  39    details of shared object loading to the debugger.  If the executable's
  40    dynamic section has a DT_DEBUG element, the run-time linker sets that
  41    element's value to the address where this structure can be found.  */
  42
  43 struct r_debug
  44   {
  45     int r_version;              /* Version number for this protocol.  */
  46
  47     struct link_map *r_map;     /* Head of the chain of loaded objects.  */
  48
  49     /* This is the address of a function internal to the run-time linker,
  50        that will always be called when the linker begins to map in a
  51        library or unmap it, and again when the mapping change is complete.
  52        The debugger can set a breakpoint at this address if it wants to
  53        notice shared object mapping changes.  */
  54     ElfW(Addr) r_brk;
  55     enum
  56       {
  57         /* This state value describes the mapping change taking place when
  58            the `r_brk' address is called.  */
  59         RT_CONSISTENT,          /* Mapping change is complete.  */
  60         RT_ADD,                 /* Beginning to add a new object.  */
  61         RT_DELETE               /* Beginning to remove an object mapping.  */
  62       } r_state;
  63
  64     ElfW(Addr) r_ldbase;        /* Base address the linker is loaded at.  */
  65   };
  66
  67 /* This is the instance of that structure used by the dynamic linker.  */
  68 extern struct r_debug _r_debug;
  69
  70 /* This symbol refers to the "dynamic structure" in the `.dynamic' section
  71    of whatever module refers to `_DYNAMIC'.  So, to find its own
  72    `struct r_debug', a program could do:
  73      for (dyn = _DYNAMIC; dyn->d_tag != DT_NULL; ++dyn)
  74        if (dyn->d_tag == DT_DEBUG)
  75          r_debug = (struct r_debug *) dyn->d_un.d_ptr;
  76    */
  77 extern ElfW(Dyn) _DYNAMIC[];
  78
  79 /* Structure describing a loaded shared object.  The `l_next' and `l_prev'
  80    members form a chain of all the shared objects loaded at startup.
  81
  82    These data structures exist in space used by the run-time dynamic linker;
  83    modifying them may have disastrous results.  */
  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
  96 #ifdef __USE_GNU
  97
  98 /* Version numbers for la_version handshake interface.  */
  99 #define LAV_CURRENT     1
 100
 101 /* Activity types signaled through la_activity.  */
 102 enum
 103   {
 104     LA_ACT_CONSISTENT,          /* Link map consistent again.  */
 105     LA_ACT_ADD,                 /* New object will be added.  */
 106     LA_ACT_DELETE               /* Objects will be removed.  */
 107   };
 108
 109 /* Values representing origin of name for dynamic loading.  */
 110 enum
 111   {
 112     LA_SER_ORIG = 0x01,         /* Original name.  */
 113     LA_SER_LIBPATH = 0x02,      /* Directory from LD_LIBRARY_PATH.  */
 114     LA_SER_RUNPATH = 0x04,      /* Directory from RPATH/RUNPATH.  */
 115     LA_SER_CONFIG = 0x08,       /* Found through ldconfig.  */
 116     LA_SER_DEFAULT = 0x40,      /* Default directory.  */
 117     LA_SER_SECURE = 0x80        /* Unused.  */
 118   };
 119
 120 /* Values for la_objopen return value.  */
 121 enum
 122   {
 123     LA_FLG_BINDTO = 0x01,       /* Audit symbols bound to this object.  */
 124     LA_FLG_BINDFROM = 0x02      /* Audit symbols bound from this object.  */
 125   };
 126
 127 /* Values for la_symbind flags parameter.  */
 128 enum
 129   {
 130     LA_SYMB_NOPLTENTER = 0x01,  /* la_pltenter will not be called.  */
 131     LA_SYMB_NOPLTEXIT = 0x02,   /* la_pltexit will not be called.  */
 132     LA_SYMB_STRUCTCALL = 0x04,  /* Return value is a structure.  */
 133     LA_SYMB_DLSYM = 0x08,       /* Binding due to dlsym call.  */
 134     LA_SYMB_ALTVALUE = 0x10     /* Value has been changed by a previous
 135                                    la_symbind call.  */
 136   };
 137
 138
 139 struct dl_phdr_info
 140   {
 141     ElfW(Addr) dlpi_addr;
 142     const char *dlpi_name;
 143     const ElfW(Phdr) *dlpi_phdr;
 144     ElfW(Half) dlpi_phnum;
 145
 146     /* Note: the next two members were introduced after the first
 147        version of this structure was available.  Check the SIZE
 148        argument passed to the dl_iterate_phdr() callback to determine
 149        whether or not they are provided.  */
 150
 151     /* Incremented when a new object may have been added.  */
 152     unsigned long long int dlpi_adds;
 153     /* Incremented when an object may have been removed.  */
 154     unsigned long long int dlpi_subs;
 155   };
 156
 157 __BEGIN_DECLS
 158
 159 extern int dl_iterate_phdr (int (*__callback) (struct dl_phdr_info *,
 160                                                size_t, void *),
 161                             void *__data);
 162
 163
 164 /* Prototypes for the ld.so auditing interfaces.  These are not
 165    defined anywhere in ld.so but instead have to be provided by the
 166    auditing DSO.  */
 167 extern unsigned int la_version (unsigned int __version);
 168 extern void la_activity (uintptr_t *__cookie, unsigned int __flag);
 169 extern char *la_objsearch (const char *__name, uintptr_t *__cookie,
 170                            unsigned int __flag);
 171 extern unsigned int la_objopen (struct link_map *__map, Lmid_t __lmid,
 172                                 uintptr_t *__cookie);
 173 extern void la_preinit (uintptr_t *__cookie);
 174 extern uintptr_t la_symbind32 (Elf32_Sym *__sym, unsigned int __ndx,
 175                                uintptr_t *__refcook, uintptr_t *__defcook,
 176                                unsigned int *__flags, const char *__symname);
 177 extern uintptr_t la_symbind64 (Elf64_Sym *__sym, unsigned int __ndx,
 178                                uintptr_t *__refcook, uintptr_t *__defcook,
 179                                unsigned int *__flags, const char *__symname);
 180 extern unsigned int la_objclose (uintptr_t *__cookie);
 181
 182 __END_DECLS
 183
 184 #endif
 185
 186 #endif /* link.h */