linker.h revision c1bd559d5b0fdcc25db2b6ae2705914103b24699 
1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *  * Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 *  * Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in
12 *    the documentation and/or other materials provided with the
13 *    distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#ifndef _LINKER_H_
30#define _LINKER_H_
31
32#include <unistd.h>
33#include <sys/types.h>
34#include <elf.h>
35#include <sys/exec_elf.h>
36
37#undef PAGE_MASK
38#undef PAGE_SIZE
39#define PAGE_SIZE 4096
40#define PAGE_MASK (PAGE_SIZE-1)
41
42/* Convenience macros to make page address/offset computations more explicit */
43
44/* Returns the address of the page starting at address 'x' */
45#define PAGE_START(x)  ((x) & ~PAGE_MASK)
46
47/* Returns the offset of address 'x' in its memory page, i.e. this is the
48 * same than 'x' - PAGE_START(x) */
49#define PAGE_OFFSET(x) ((x) & PAGE_MASK)
50
51/* Returns the address of the next page after address 'x', unless 'x' is
52 * itself at the start of a page. Equivalent to:
53 *
54 *  (x == PAGE_START(x)) ? x : PAGE_START(x)+PAGE_SIZE
55 */
56#define PAGE_END(x)    PAGE_START((x) + (PAGE_SIZE-1))
57
58void debugger_init();
59const char *addr_to_name(unsigned addr);
60
61/* magic shared structures that GDB knows about */
62
63struct link_map
64{
65    uintptr_t l_addr;
66    char * l_name;
67    uintptr_t l_ld;
68    struct link_map * l_next;
69    struct link_map * l_prev;
70};
71
72/* needed for dl_iterate_phdr to be passed to the callbacks provided */
73struct dl_phdr_info
74{
75    Elf32_Addr dlpi_addr;
76    const char *dlpi_name;
77    const Elf32_Phdr *dlpi_phdr;
78    Elf32_Half dlpi_phnum;
79};
80
81
82// Values for r_debug->state
83enum {
84    RT_CONSISTENT,
85    RT_ADD,
86    RT_DELETE
87};
88
89struct r_debug
90{
91    int32_t r_version;
92    struct link_map * r_map;
93    void (*r_brk)(void);
94    int32_t r_state;
95    uintptr_t r_ldbase;
96};
97
98typedef struct soinfo soinfo;
99
100#define FLAG_LINKED     0x00000001
101#define FLAG_ERROR      0x00000002
102#define FLAG_EXE        0x00000004 // The main executable
103#define FLAG_LINKER     0x00000010 // The linker itself
104
105#define SOINFO_NAME_LEN 128
106
107struct soinfo
108{
109    const char name[SOINFO_NAME_LEN];
110    Elf32_Phdr *phdr;
111    int phnum;
112    unsigned entry;
113    unsigned base;
114    unsigned size;
115
116    int unused;  // DO NOT USE, maintained for compatibility.
117
118    unsigned *dynamic;
119
120    unsigned wrprotect_start;
121    unsigned wrprotect_end;
122
123    soinfo *next;
124    unsigned flags;
125
126    const char *strtab;
127    Elf32_Sym *symtab;
128
129    unsigned nbucket;
130    unsigned nchain;
131    unsigned *bucket;
132    unsigned *chain;
133
134    unsigned *plt_got;
135
136    Elf32_Rel *plt_rel;
137    unsigned plt_rel_count;
138
139    Elf32_Rel *rel;
140    unsigned rel_count;
141
142    unsigned *preinit_array;
143    unsigned preinit_array_count;
144
145    unsigned *init_array;
146    unsigned init_array_count;
147    unsigned *fini_array;
148    unsigned fini_array_count;
149
150    void (*init_func)(void);
151    void (*fini_func)(void);
152
153#ifdef ANDROID_ARM_LINKER
154    /* ARM EABI section used for stack unwinding. */
155    unsigned *ARM_exidx;
156    unsigned ARM_exidx_count;
157#endif
158
159    unsigned refcount;
160    struct link_map linkmap;
161
162    int constructors_called;
163
164    Elf32_Addr gnu_relro_start;
165    unsigned gnu_relro_len;
166
167    /* When you read a virtual address from the ELF file, add the load
168     * address (= "base" field) minus this value (= "load_offset") to get the
169     * real, corresponding address in the process' address space */
170    Elf32_Addr load_offset;
171};
172
173
174extern soinfo libdl_info;
175
176#ifdef ANDROID_ARM_LINKER
177
178#define R_ARM_COPY       20
179#define R_ARM_GLOB_DAT   21
180#define R_ARM_JUMP_SLOT  22
181#define R_ARM_RELATIVE   23
182
183/* According to the AAPCS specification, we only
184 * need the above relocations. However, in practice,
185 * the following ones turn up from time to time.
186 */
187#define R_ARM_ABS32      2
188#define R_ARM_REL32      3
189
190#elif defined(ANDROID_X86_LINKER)
191
192#define R_386_32         1
193#define R_386_PC32       2
194#define R_386_GLOB_DAT   6
195#define R_386_JUMP_SLOT  7
196#define R_386_RELATIVE   8
197
198#endif
199
200#ifndef DT_INIT_ARRAY
201#define DT_INIT_ARRAY      25
202#endif
203
204#ifndef DT_FINI_ARRAY
205#define DT_FINI_ARRAY      26
206#endif
207
208#ifndef DT_INIT_ARRAYSZ
209#define DT_INIT_ARRAYSZ    27
210#endif
211
212#ifndef DT_FINI_ARRAYSZ
213#define DT_FINI_ARRAYSZ    28
214#endif
215
216#ifndef DT_PREINIT_ARRAY
217#define DT_PREINIT_ARRAY   32
218#endif
219
220#ifndef DT_PREINIT_ARRAYSZ
221#define DT_PREINIT_ARRAYSZ 33
222#endif
223
224soinfo *find_library(const char *name);
225Elf32_Sym *lookup(const char *name, soinfo **found, soinfo *start);
226soinfo *find_containing_library(const void *addr);
227const char *linker_get_error(void);
228
229unsigned soinfo_unload(soinfo *si);
230Elf32_Sym *soinfo_find_symbol(soinfo* si, const void *addr);
231Elf32_Sym *soinfo_lookup(soinfo *si, const char *name);
232void soinfo_call_constructors(soinfo *si);
233
234#ifdef ANDROID_ARM_LINKER
235typedef long unsigned int *_Unwind_Ptr;
236_Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int *pcount);
237#elif defined(ANDROID_X86_LINKER)
238int dl_iterate_phdr(int (*cb)(struct dl_phdr_info *, size_t, void *), void *);
239#endif
240
241#endif
242