1 | /* Data structure for communication from the run-time dynamic linker for |
2 | loaded ELF shared objects. |
3 | Copyright (C) 1995-2018 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 | #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 | /* Rendezvous structure used by the run-time dynamic linker to communicate |
38 | details of shared object loading to the debugger. If the executable's |
39 | dynamic section has a DT_DEBUG element, the run-time linker sets that |
40 | element's value to the address where this structure can be found. */ |
41 | |
42 | struct r_debug |
43 | { |
44 | int r_version; /* Version number for this protocol. */ |
45 | |
46 | struct link_map *r_map; /* Head of the chain of loaded objects. */ |
47 | |
48 | /* This is the address of a function internal to the run-time linker, |
49 | that will always be called when the linker begins to map in a |
50 | library or unmap it, and again when the mapping change is complete. |
51 | The debugger can set a breakpoint at this address if it wants to |
52 | notice shared object mapping changes. */ |
53 | ElfW(Addr) r_brk; |
54 | enum |
55 | { |
56 | /* This state value describes the mapping change taking place when |
57 | the `r_brk' address is called. */ |
58 | RT_CONSISTENT, /* Mapping change is complete. */ |
59 | RT_ADD, /* Beginning to add a new object. */ |
60 | RT_DELETE /* Beginning to remove an object mapping. */ |
61 | } r_state; |
62 | |
63 | ElfW(Addr) r_ldbase; /* Base address the linker is loaded at. */ |
64 | }; |
65 | |
66 | /* This is the instance of that structure used by the dynamic linker. */ |
67 | extern struct r_debug _r_debug; |
68 | |
69 | /* This symbol refers to the "dynamic structure" in the `.dynamic' section |
70 | of whatever module refers to `_DYNAMIC'. So, to find its own |
71 | `struct r_debug', a program could do: |
72 | for (dyn = _DYNAMIC; dyn->d_tag != DT_NULL; ++dyn) |
73 | if (dyn->d_tag == DT_DEBUG) |
74 | r_debug = (struct r_debug *) dyn->d_un.d_ptr; |
75 | */ |
76 | extern ElfW(Dyn) _DYNAMIC[]; |
77 | |
78 | /* Structure describing a loaded shared object. The `l_next' and `l_prev' |
79 | members form a chain of all the shared objects loaded at startup. |
80 | |
81 | These data structures exist in space used by the run-time dynamic linker; |
82 | modifying them may have disastrous results. */ |
83 | |
84 | struct link_map |
85 | { |
86 | /* These first few members are part of the protocol with the debugger. |
87 | This is the same format used in SVR4. */ |
88 | |
89 | ElfW(Addr) l_addr; /* Difference between the address in the ELF |
90 | file and the addresses in memory. */ |
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 | __extension__ unsigned long long int dlpi_adds; |
152 | /* Incremented when an object may have been removed. */ |
153 | __extension__ 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 | |