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 #define ELFW(type) _ElfW (ELF, __ELF_NATIVE_CLASS, type) 40 41 #include <bits/elfclass.h> /* Defines __ELF_NATIVE_CLASS. */ 42 43 /* Rendezvous structure used by the run-time dynamic linker to communicate 44 details of shared object loading to the debugger. If the executable's 45 dynamic section has a DT_DEBUG element, the run-time linker sets that 46 element's value to the address where this structure can be found. */ 47 48 struct r_debug 49 { 50 int r_version; /* Version number for this protocol. */ 51 52 struct link_map *r_map; /* Head of the chain of loaded objects. */ 53 54 /* This is the address of a function internal to the run-time linker, 55 that will always be called when the linker begins to map in a 56 library or unmap it, and again when the mapping change is complete. 57 The debugger can set a breakpoint at this address if it wants to 58 notice shared object mapping changes. */ 59 ElfW(Addr) r_brk; 60 enum 61 { 62 /* This state value describes the mapping change taking place when 63 the `r_brk' address is called. */ 64 RT_CONSISTENT, /* Mapping change is complete. */ 65 RT_ADD, /* Beginning to add a new object. */ 66 RT_DELETE /* Beginning to remove an object mapping. */ 67 } r_state; 68 69 ElfW(Addr) r_ldbase; /* Base address the linker is loaded at. */ 70 }; 71 72 /* This is the instance of that structure used by the dynamic linker. */ 73 extern struct r_debug _r_debug; 74 75 /* This symbol refers to the "dynamic structure" in the `.dynamic' section 76 of whatever module refers to `_DYNAMIC'. So, to find its own 77 `struct r_debug', a program could do: 78 for (dyn = _DYNAMIC; dyn->d_tag != DT_NULL; ++dyn) 79 if (dyn->d_tag == DT_DEBUG) 80 r_debug = (struct r_debug *) dyn->d_un.d_ptr; 81 */ 82 extern ElfW(Dyn) _DYNAMIC[]; 83 84 #ifdef __FDPIC__ 85 # include <bits/elf-fdpic.h> 86 #endif 87 #ifdef __DSBT__ 88 # include <bits/elf-dsbt.h> 89 #endif 90 91 /* Structure describing a loaded shared object. The `l_next' and `l_prev' 92 members form a chain of all the shared objects loaded at startup. 93 94 These data structures exist in space used by the run-time dynamic linker; 95 modifying them may have disastrous results. */ 96 97 struct link_map 98 { 99 /* These first few members are part of the protocol with the debugger. 100 This is the same format used in SVR4. */ 101 102 #ifdef __FDPIC__ 103 struct elf32_fdpic_loadaddr l_addr; 104 #else 105 #ifdef __DSBT__ 106 struct elf32_dsbt_loadaddr l_addr; 107 #else 108 ElfW(Addr) l_addr; /* Base address shared object is loaded at. */ 109 #endif 110 #endif 111 char *l_name; /* Absolute file name object was found in. */ 112 ElfW(Dyn) *l_ld; /* Dynamic section of the shared object. */ 113 struct link_map *l_next, *l_prev; /* Chain of loaded objects. */ 114 #ifdef _LIBC 115 #if defined(USE_TLS) && USE_TLS 116 /* Thread-local storage related info. */ 117 118 /* Start of the initialization image. */ 119 void *l_tls_initimage; 120 /* Size of the initialization image. */ 121 size_t l_tls_initimage_size; 122 /* Size of the TLS block. */ 123 size_t l_tls_blocksize; 124 /* Alignment requirement of the TLS block. */ 125 size_t l_tls_align; 126 /* Offset of first byte module alignment. */ 127 size_t l_tls_firstbyte_offset; 128 # ifndef NO_TLS_OFFSET 129 # define NO_TLS_OFFSET 0 130 # endif 131 /* For objects present at startup time: offset in the static TLS block. */ 132 ptrdiff_t l_tls_offset; 133 /* Index of the module in the dtv array. */ 134 size_t l_tls_modid; 135 /* Nonzero if _dl_init_static_tls should be called for this module */ 136 unsigned int l_need_tls_init:1; 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 */ 254