about summary refs log tree commit diff
path: root/elf/link.h
blob: f448141bab5e2e32a5972f753f08cab28470e7e2 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
/* Data structure for communication from the run-time dynamic linker for
   loaded ELF shared objects.
   Copyright (C) 1995-2016 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#ifndef	_LINK_H
#define	_LINK_H	1

#include <features.h>
#include <elf.h>
#include <dlfcn.h>
#include <sys/types.h>

/* We use this macro to refer to ELF types independent of the native wordsize.
   `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'.  */
#define ElfW(type)	_ElfW (Elf, __ELF_NATIVE_CLASS, type)
#define _ElfW(e,w,t)	_ElfW_1 (e, w, _##t)
#define _ElfW_1(e,w,t)	e##w##t

#include <bits/elfclass.h>		/* Defines __ELF_NATIVE_CLASS.  */
#include <bits/link.h>

/* Rendezvous structure used by the run-time dynamic linker to communicate
   details of shared object loading to the debugger.  If the executable's
   dynamic section has a DT_DEBUG element, the run-time linker sets that
   element's value to the address where this structure can be found.  */

struct r_debug
  {
    int r_version;		/* Version number for this protocol.  */

    struct link_map *r_map;	/* Head of the chain of loaded objects.  */

    /* This is the address of a function internal to the run-time linker,
       that will always be called when the linker begins to map in a
       library or unmap it, and again when the mapping change is complete.
       The debugger can set a breakpoint at this address if it wants to
       notice shared object mapping changes.  */
    ElfW(Addr) r_brk;
    enum
      {
	/* This state value describes the mapping change taking place when
	   the `r_brk' address is called.  */
	RT_CONSISTENT,		/* Mapping change is complete.  */
	RT_ADD,			/* Beginning to add a new object.  */
	RT_DELETE		/* Beginning to remove an object mapping.  */
      } r_state;

    ElfW(Addr) r_ldbase;	/* Base address the linker is loaded at.  */
  };

/* This is the instance of that structure used by the dynamic linker.  */
extern struct r_debug _r_debug;

/* This symbol refers to the "dynamic structure" in the `.dynamic' section
   of whatever module refers to `_DYNAMIC'.  So, to find its own
   `struct r_debug', a program could do:
     for (dyn = _DYNAMIC; dyn->d_tag != DT_NULL; ++dyn)
       if (dyn->d_tag == DT_DEBUG)
	 r_debug = (struct r_debug *) dyn->d_un.d_ptr;
   */
extern ElfW(Dyn) _DYNAMIC[];

/* Structure describing a loaded shared object.  The `l_next' and `l_prev'
   members form a chain of all the shared objects loaded at startup.

   These data structures exist in space used by the run-time dynamic linker;
   modifying them may have disastrous results.  */

struct link_map
  {
    /* These first few members are part of the protocol with the debugger.
       This is the same format used in SVR4.  */

    ElfW(Addr) l_addr;		/* Difference between the address in the ELF
				   file and the addresses in memory.  */
    char *l_name;		/* Absolute file name object was found in.  */
    ElfW(Dyn) *l_ld;		/* Dynamic section of the shared object.  */
    struct link_map *l_next, *l_prev; /* Chain of loaded objects.  */
  };

#ifdef __USE_GNU

/* Version numbers for la_version handshake interface.  */
#define LAV_CURRENT	1

/* Activity types signaled through la_activity.  */
enum
  {
    LA_ACT_CONSISTENT,		/* Link map consistent again.  */
    LA_ACT_ADD,			/* New object will be added.  */
    LA_ACT_DELETE		/* Objects will be removed.  */
  };

/* Values representing origin of name for dynamic loading.  */
enum
  {
    LA_SER_ORIG = 0x01,		/* Original name.  */
    LA_SER_LIBPATH = 0x02,	/* Directory from LD_LIBRARY_PATH.  */
    LA_SER_RUNPATH = 0x04,	/* Directory from RPATH/RUNPATH.  */
    LA_SER_CONFIG = 0x08,	/* Found through ldconfig.  */
    LA_SER_DEFAULT = 0x40,	/* Default directory.  */
    LA_SER_SECURE = 0x80	/* Unused.  */
  };

/* Values for la_objopen return value.  */
enum
  {
    LA_FLG_BINDTO = 0x01,	/* Audit symbols bound to this object.  */
    LA_FLG_BINDFROM = 0x02	/* Audit symbols bound from this object.  */
  };

/* Values for la_symbind flags parameter.  */
enum
  {
    LA_SYMB_NOPLTENTER = 0x01,	/* la_pltenter will not be called.  */
    LA_SYMB_NOPLTEXIT = 0x02,	/* la_pltexit will not be called.  */
    LA_SYMB_STRUCTCALL = 0x04,	/* Return value is a structure.  */
    LA_SYMB_DLSYM = 0x08,	/* Binding due to dlsym call.  */
    LA_SYMB_ALTVALUE = 0x10	/* Value has been changed by a previous
				   la_symbind call.  */
  };

struct dl_phdr_info
  {
    ElfW(Addr) dlpi_addr;
    const char *dlpi_name;
    const ElfW(Phdr) *dlpi_phdr;
    ElfW(Half) dlpi_phnum;

    /* Note: Following members were introduced after the first
       version of this structure was available.  Check the SIZE
       argument passed to the dl_iterate_phdr callback to determine
       whether or not each later member is available.  */

    /* Incremented when a new object may have been added.  */
    __extension__ unsigned long long int dlpi_adds;
    /* Incremented when an object may have been removed.  */
    __extension__ unsigned long long int dlpi_subs;

    /* If there is a PT_TLS segment, its module ID as used in
       TLS relocations, else zero.  */
    size_t dlpi_tls_modid;

    /* The address of the calling thread's instance of this module's
       PT_TLS segment, if it has one and it has been allocated
       in the calling thread, otherwise a null pointer.  */
    void *dlpi_tls_data;
  };

__BEGIN_DECLS

extern int dl_iterate_phdr (int (*__callback) (struct dl_phdr_info *,
					       size_t, void *),
			    void *__data);


/* Prototypes for the ld.so auditing interfaces.  These are not
   defined anywhere in ld.so but instead have to be provided by the
   auditing DSO.  */
extern unsigned int la_version (unsigned int __version);
extern void la_activity (uintptr_t *__cookie, unsigned int __flag);
extern char *la_objsearch (const char *__name, uintptr_t *__cookie,
			   unsigned int __flag);
extern unsigned int la_objopen (struct link_map *__map, Lmid_t __lmid,
				uintptr_t *__cookie);
extern void la_preinit (uintptr_t *__cookie);
extern uintptr_t la_symbind32 (Elf32_Sym *__sym, unsigned int __ndx,
			       uintptr_t *__refcook, uintptr_t *__defcook,
			       unsigned int *__flags, const char *__symname);
extern uintptr_t la_symbind64 (Elf64_Sym *__sym, unsigned int __ndx,
			       uintptr_t *__refcook, uintptr_t *__defcook,
			       unsigned int *__flags, const char *__symname);
extern unsigned int la_objclose (uintptr_t *__cookie);

__END_DECLS

#endif

#endif /* link.h */