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 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 struct dl_phdr_info 139 { 140 ElfW(Addr) dlpi_addr; 141 const char *dlpi_name; 142 const ElfW(Phdr) *dlpi_phdr; 143 ElfW(Half) dlpi_phnum; 144 145 /* Note: Following members were introduced after the first 146 version of this structure was available. Check the SIZE 147 argument passed to the dl_iterate_phdr callback to determine 148 whether or not each later member is available. */ 149 150 /* Incremented when a new object may have been added. */ 151 unsigned long long int dlpi_adds; 152 /* Incremented when an object may have been removed. */ 153 unsigned long long int dlpi_subs; 154 155 /* If there is a PT_TLS segment, its module ID as used in 156 TLS relocations, else zero. */ 157 size_t dlpi_tls_modid; 158 159 /* The address of the calling thread's instance of this module's 160 PT_TLS segment, if it has one and it has been allocated 161 in the calling thread, otherwise a null pointer. */ 162 void *dlpi_tls_data; 163 }; 164 165 __BEGIN_DECLS 166 167 extern int dl_iterate_phdr (int (*__callback) (struct dl_phdr_info *, 168 size_t, void *), 169 void *__data); 170 171 172 /* Prototypes for the ld.so auditing interfaces. These are not 173 defined anywhere in ld.so but instead have to be provided by the 174 auditing DSO. */ 175 extern unsigned int la_version (unsigned int __version); 176 extern void la_activity (uintptr_t *__cookie, unsigned int __flag); 177 extern char *la_objsearch (const char *__name, uintptr_t *__cookie, 178 unsigned int __flag); 179 extern unsigned int la_objopen (struct link_map *__map, Lmid_t __lmid, 180 uintptr_t *__cookie); 181 extern void la_preinit (uintptr_t *__cookie); 182 extern uintptr_t la_symbind32 (Elf32_Sym *__sym, unsigned int __ndx, 183 uintptr_t *__refcook, uintptr_t *__defcook, 184 unsigned int *__flags, const char *__symname); 185 extern uintptr_t la_symbind64 (Elf64_Sym *__sym, unsigned int __ndx, 186 uintptr_t *__refcook, uintptr_t *__defcook, 187 unsigned int *__flags, const char *__symname); 188 extern unsigned int la_objclose (uintptr_t *__cookie); 189 190 __END_DECLS 191 192 #endif 193 194 #endif /* link.h */ 195