1 /* Data structure for communication from the run-time dynamic linker for 2 loaded ELF shared objects. 3 Copyright (C) 1995-2022 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 <https://www.gnu.org/licenses/>. */ 19 20 #ifndef _LINK_H 21 #define _LINK_H 1 22 23 #include <features.h> 24 #include <elf.h> 25 #include <dlfcn.h> 26 #include <sys/types.h> 27 28 /* We use this macro to refer to ELF types independent of the native wordsize. 29 `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'. */ 30 #define ElfW(type) _ElfW (Elf, __ELF_NATIVE_CLASS, type) 31 #define _ElfW(e,w,t) _ElfW_1 (e, w, _##t) 32 #define _ElfW_1(e,w,t) e##w##t 33 34 #include <bits/elfclass.h> /* Defines __ELF_NATIVE_CLASS. */ 35 #include <bits/link.h> 36 37 /* The legacy rendezvous structure used by the run-time dynamic linker to 38 communicate details of shared object loading to the debugger. */ 39 40 struct r_debug 41 { 42 /* Version number for this protocol. It should be greater than 0. */ 43 int r_version; 44 45 struct link_map *r_map; /* Head of the chain of loaded objects. */ 46 47 /* This is the address of a function internal to the run-time linker, 48 that will always be called when the linker begins to map in a 49 library or unmap it, and again when the mapping change is complete. 50 The debugger can set a breakpoint at this address if it wants to 51 notice shared object mapping changes. */ 52 ElfW(Addr) r_brk; 53 enum 54 { 55 /* This state value describes the mapping change taking place when 56 the `r_brk' address is called. */ 57 RT_CONSISTENT, /* Mapping change is complete. */ 58 RT_ADD, /* Beginning to add a new object. */ 59 RT_DELETE /* Beginning to remove an object mapping. */ 60 } r_state; 61 62 ElfW(Addr) r_ldbase; /* Base address the linker is loaded at. */ 63 }; 64 65 /* This is the symbol of that structure provided by the dynamic linker. */ 66 extern struct r_debug _r_debug; 67 68 /* The extended rendezvous structure used by the run-time dynamic linker 69 to communicate details of shared object loading to the debugger. If 70 the executable's dynamic section has a DT_DEBUG element, the run-time 71 linker sets that element's value to the address where this structure 72 can be found. */ 73 74 struct r_debug_extended 75 { 76 struct r_debug base; 77 78 /* The following field is added by r_version == 2. */ 79 80 /* Link to the next r_debug_extended structure. Each r_debug_extended 81 structure represents a different namespace. The first 82 r_debug_extended structure is for the default namespace. */ 83 struct r_debug_extended *r_next; 84 }; 85 86 /* This symbol refers to the "dynamic structure" in the `.dynamic' section 87 of whatever module refers to `_DYNAMIC'. So, to find its own 88 `struct r_debug_extended', a program could do: 89 for (dyn = _DYNAMIC; dyn->d_tag != DT_NULL; ++dyn) 90 if (dyn->d_tag == DT_DEBUG) 91 r_debug_extended = (struct r_debug_extended *) dyn->d_un.d_ptr; 92 */ 93 extern ElfW(Dyn) _DYNAMIC[]; 94 95 /* Structure describing a loaded shared object. The `l_next' and `l_prev' 96 members form a chain of all the shared objects loaded at startup. 97 98 These data structures exist in space used by the run-time dynamic linker; 99 modifying them may have disastrous results. */ 100 101 struct link_map 102 { 103 /* These first few members are part of the protocol with the debugger. 104 This is the same format used in SVR4. */ 105 106 ElfW(Addr) l_addr; /* Difference between the address in the ELF 107 file and the addresses in memory. */ 108 char *l_name; /* Absolute file name object was found in. */ 109 ElfW(Dyn) *l_ld; /* Dynamic section of the shared object. */ 110 struct link_map *l_next, *l_prev; /* Chain of loaded objects. */ 111 }; 112 113 #ifdef __USE_GNU 114 115 /* Version numbers for la_version handshake interface. */ 116 #include <bits/link_lavcurrent.h> 117 118 /* Activity types signaled through la_activity. */ 119 enum 120 { 121 LA_ACT_CONSISTENT, /* Link map consistent again. */ 122 LA_ACT_ADD, /* New object will be added. */ 123 LA_ACT_DELETE /* Objects will be removed. */ 124 }; 125 126 /* Values representing origin of name for dynamic loading. */ 127 enum 128 { 129 LA_SER_ORIG = 0x01, /* Original name. */ 130 LA_SER_LIBPATH = 0x02, /* Directory from LD_LIBRARY_PATH. */ 131 LA_SER_RUNPATH = 0x04, /* Directory from RPATH/RUNPATH. */ 132 LA_SER_CONFIG = 0x08, /* Found through ldconfig. */ 133 LA_SER_DEFAULT = 0x40, /* Default directory. */ 134 LA_SER_SECURE = 0x80 /* Unused. */ 135 }; 136 137 /* Values for la_objopen return value. */ 138 enum 139 { 140 LA_FLG_BINDTO = 0x01, /* Audit symbols bound to this object. */ 141 LA_FLG_BINDFROM = 0x02 /* Audit symbols bound from this object. */ 142 }; 143 144 /* Values for la_symbind flags parameter. */ 145 enum 146 { 147 LA_SYMB_NOPLTENTER = 0x01, /* la_pltenter will not be called. */ 148 LA_SYMB_NOPLTEXIT = 0x02, /* la_pltexit will not be called. */ 149 LA_SYMB_STRUCTCALL = 0x04, /* Return value is a structure. */ 150 LA_SYMB_DLSYM = 0x08, /* Binding due to dlsym call. */ 151 LA_SYMB_ALTVALUE = 0x10 /* Value has been changed by a previous 152 la_symbind call. */ 153 }; 154 155 struct dl_phdr_info 156 { 157 ElfW(Addr) dlpi_addr; 158 const char *dlpi_name; 159 const ElfW(Phdr) *dlpi_phdr; 160 ElfW(Half) dlpi_phnum; 161 162 /* Note: Following members were introduced after the first 163 version of this structure was available. Check the SIZE 164 argument passed to the dl_iterate_phdr callback to determine 165 whether or not each later member is available. */ 166 167 /* Incremented when a new object may have been added. */ 168 __extension__ unsigned long long int dlpi_adds; 169 /* Incremented when an object may have been removed. */ 170 __extension__ unsigned long long int dlpi_subs; 171 172 /* If there is a PT_TLS segment, its module ID as used in 173 TLS relocations, else zero. */ 174 size_t dlpi_tls_modid; 175 176 /* The address of the calling thread's instance of this module's 177 PT_TLS segment, if it has one and it has been allocated 178 in the calling thread, otherwise a null pointer. */ 179 void *dlpi_tls_data; 180 }; 181 182 __BEGIN_DECLS 183 184 extern int dl_iterate_phdr (int (*__callback) (struct dl_phdr_info *, 185 size_t, void *), 186 void *__data); 187 188 189 /* Prototypes for the ld.so auditing interfaces. These are not 190 defined anywhere in ld.so but instead have to be provided by the 191 auditing DSO. */ 192 extern unsigned int la_version (unsigned int __version); 193 extern void la_activity (uintptr_t *__cookie, unsigned int __flag); 194 extern char *la_objsearch (const char *__name, uintptr_t *__cookie, 195 unsigned int __flag); 196 extern unsigned int la_objopen (struct link_map *__map, Lmid_t __lmid, 197 uintptr_t *__cookie); 198 extern void la_preinit (uintptr_t *__cookie); 199 extern uintptr_t la_symbind32 (Elf32_Sym *__sym, unsigned int __ndx, 200 uintptr_t *__refcook, uintptr_t *__defcook, 201 unsigned int *__flags, const char *__symname); 202 extern uintptr_t la_symbind64 (Elf64_Sym *__sym, unsigned int __ndx, 203 uintptr_t *__refcook, uintptr_t *__defcook, 204 unsigned int *__flags, const char *__symname); 205 extern unsigned int la_objclose (uintptr_t *__cookie); 206 207 __END_DECLS 208 209 #endif 210 211 #endif /* link.h */ 212