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
42struct 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. */
67extern 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 */
76extern 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
84struct 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. */
102enum
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. */
110enum
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. */
121enum
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. */
128enum
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
138struct 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
167extern 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. */
175extern unsigned int la_version (unsigned int __version);
176extern void la_activity (uintptr_t *__cookie, unsigned int __flag);
177extern char *la_objsearch (const char *__name, uintptr_t *__cookie,
178 unsigned int __flag);
179extern unsigned int la_objopen (struct link_map *__map, Lmid_t __lmid,
180 uintptr_t *__cookie);
181extern void la_preinit (uintptr_t *__cookie);
182extern uintptr_t la_symbind32 (Elf32_Sym *__sym, unsigned int __ndx,
183 uintptr_t *__refcook, uintptr_t *__defcook,
184 unsigned int *__flags, const char *__symname);
185extern uintptr_t la_symbind64 (Elf64_Sym *__sym, unsigned int __ndx,
186 uintptr_t *__refcook, uintptr_t *__defcook,
187 unsigned int *__flags, const char *__symname);
188extern unsigned int la_objclose (uintptr_t *__cookie);
189
190__END_DECLS
191
192#endif
193
194#endif /* link.h */
195