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 <elf.h>
33 #include <inttypes.h>
34 #include <link.h>
35 #include <unistd.h>
36 #include <android/dlext.h>
37 #include <sys/stat.h>
38 
39 #include "private/libc_logging.h"
40 #include "linked_list.h"
41 
42 #define DL_ERR(fmt, x...) \
43     do { \
44       __libc_format_buffer(linker_get_error_buffer(), linker_get_error_buffer_size(), fmt, ##x); \
45       /* If LD_DEBUG is set high enough, log every dlerror(3) message. */ \
46       DEBUG("%s\n", linker_get_error_buffer()); \
47     } while (false)
48 
49 #define DL_WARN(fmt, x...) \
50     do { \
51       __libc_format_log(ANDROID_LOG_WARN, "linker", fmt, ##x); \
52       __libc_format_fd(2, "WARNING: linker: "); \
53       __libc_format_fd(2, fmt, ##x); \
54       __libc_format_fd(2, "\n"); \
55     } while (false)
56 
57 #if defined(__LP64__)
58 #define ELFW(what) ELF64_ ## what
59 #else
60 #define ELFW(what) ELF32_ ## what
61 #endif
62 
63 // mips64 interprets Elf64_Rel structures' r_info field differently.
64 // bionic (like other C libraries) has macros that assume regular ELF files,
65 // but the dynamic linker needs to be able to load mips64 ELF files.
66 #if defined(__mips__) && defined(__LP64__)
67 #undef ELF64_R_SYM
68 #undef ELF64_R_TYPE
69 #undef ELF64_R_INFO
70 #define ELF64_R_SYM(info)   (((info) >> 0) & 0xffffffff)
71 #define ELF64_R_SSYM(info)  (((info) >> 32) & 0xff)
72 #define ELF64_R_TYPE3(info) (((info) >> 40) & 0xff)
73 #define ELF64_R_TYPE2(info) (((info) >> 48) & 0xff)
74 #define ELF64_R_TYPE(info)  (((info) >> 56) & 0xff)
75 #endif
76 
77 // Returns the address of the page containing address 'x'.
78 #define PAGE_START(x)  ((x) & PAGE_MASK)
79 
80 // Returns the offset of address 'x' in its page.
81 #define PAGE_OFFSET(x) ((x) & ~PAGE_MASK)
82 
83 // Returns the address of the next page after address 'x', unless 'x' is
84 // itself at the start of a page.
85 #define PAGE_END(x)    PAGE_START((x) + (PAGE_SIZE-1))
86 
87 #define FLAG_LINKED     0x00000001
88 #define FLAG_EXE        0x00000004 // The main executable
89 #define FLAG_LINKER     0x00000010 // The linker itself
90 #define FLAG_NEW_SOINFO 0x40000000 // new soinfo format
91 
92 #define SOINFO_VERSION 0
93 
94 #define SOINFO_NAME_LEN 128
95 
96 typedef void (*linker_function_t)();
97 
98 // Android uses RELA for aarch64 and x86_64. mips64 still uses REL.
99 #if defined(__aarch64__) || defined(__x86_64__)
100 #define USE_RELA 1
101 #endif
102 
103 struct soinfo;
104 
105 class SoinfoListAllocator {
106 public:
107   static LinkedListEntry<soinfo>* alloc();
108   static void free(LinkedListEntry<soinfo>* entry);
109 private:
110   // unconstructable
111   DISALLOW_IMPLICIT_CONSTRUCTORS(SoinfoListAllocator);
112 };
113 
114 struct soinfo {
115  public:
116   typedef LinkedList<soinfo, SoinfoListAllocator> soinfo_list_t;
117  public:
118   char name[SOINFO_NAME_LEN];
119   const ElfW(Phdr)* phdr;
120   size_t phnum;
121   ElfW(Addr) entry;
122   ElfW(Addr) base;
123   size_t size;
124 
125 #ifndef __LP64__
126   uint32_t unused1;  // DO NOT USE, maintained for compatibility.
127 #endif
128 
129   ElfW(Dyn)* dynamic;
130 
131 #ifndef __LP64__
132   uint32_t unused2; // DO NOT USE, maintained for compatibility
133   uint32_t unused3; // DO NOT USE, maintained for compatibility
134 #endif
135 
136   soinfo* next;
137   unsigned flags;
138 
139  private:
140   const char* strtab;
141  public:
142   ElfW(Sym)* symtab;
143 
144   size_t nbucket;
145   size_t nchain;
146   unsigned* bucket;
147   unsigned* chain;
148 
149 #if defined(__mips__) || !defined(__LP64__)
150   // This is only used by mips and mips64, but needs to be here for
151   // all 32-bit architectures to preserve binary compatibility.
152   ElfW(Addr)** plt_got;
153 #endif
154 
155 #if defined(USE_RELA)
156   ElfW(Rela)* plt_rela;
157   size_t plt_rela_count;
158 
159   ElfW(Rela)* rela;
160   size_t rela_count;
161 #else
162   ElfW(Rel)* plt_rel;
163   size_t plt_rel_count;
164 
165   ElfW(Rel)* rel;
166   size_t rel_count;
167 #endif
168 
169   linker_function_t* preinit_array;
170   size_t preinit_array_count;
171 
172   linker_function_t* init_array;
173   size_t init_array_count;
174   linker_function_t* fini_array;
175   size_t fini_array_count;
176 
177   linker_function_t init_func;
178   linker_function_t fini_func;
179 
180 #if defined(__arm__)
181   // ARM EABI section used for stack unwinding.
182   unsigned* ARM_exidx;
183   size_t ARM_exidx_count;
184 #elif defined(__mips__)
185   unsigned mips_symtabno;
186   unsigned mips_local_gotno;
187   unsigned mips_gotsym;
188 #endif
189 
190   size_t ref_count;
191   link_map link_map_head;
192 
193   bool constructors_called;
194 
195   // When you read a virtual address from the ELF file, add this
196   // value to get the corresponding address in the process' address space.
197   ElfW(Addr) load_bias;
198 
199 #if !defined(__LP64__)
200   bool has_text_relocations;
201 #endif
202   bool has_DT_SYMBOLIC;
203 
204   soinfo(const char* name, const struct stat* file_stat, off64_t file_offset);
205 
206   void CallConstructors();
207   void CallDestructors();
208   void CallPreInitConstructors();
209   bool PrelinkImage();
210   bool LinkImage(const android_dlextinfo* extinfo);
211 
212   void add_child(soinfo* child);
213   void remove_all_links();
214 
215   ino_t get_st_ino();
216   dev_t get_st_dev();
217   off64_t get_file_offset();
218 
219   soinfo_list_t& get_children();
220   soinfo_list_t& get_parents();
221 
222   ElfW(Addr) resolve_symbol_address(ElfW(Sym)* s);
223 
224   const char* get_string(ElfW(Word) index) const;
225 
has_min_versionsoinfo226   bool inline has_min_version(uint32_t min_version) const {
227     return (flags & FLAG_NEW_SOINFO) != 0 && version >= min_version;
228   }
229  private:
230   void CallArray(const char* array_name, linker_function_t* functions, size_t count, bool reverse);
231   void CallFunction(const char* function_name, linker_function_t function);
232 #if defined(USE_RELA)
233   int Relocate(ElfW(Rela)* rela, unsigned count);
234 #else
235   int Relocate(ElfW(Rel)* rel, unsigned count);
236 #endif
237 
238  private:
239   // This part of the structure is only available
240   // when FLAG_NEW_SOINFO is set in this->flags.
241   uint32_t version;
242 
243   // version >= 0
244   dev_t st_dev;
245   ino_t st_ino;
246 
247   // dependency graph
248   soinfo_list_t children;
249   soinfo_list_t parents;
250 
251   // version >= 1
252   off64_t file_offset;
253   int rtld_flags;
254   size_t strtab_size;
255 
256   friend soinfo* get_libdl_info();
257 };
258 
259 extern soinfo* get_libdl_info();
260 
261 void do_android_get_LD_LIBRARY_PATH(char*, size_t);
262 void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path);
263 soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo);
264 void do_dlclose(soinfo* si);
265 
266 ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start);
267 soinfo* find_containing_library(const void* addr);
268 
269 ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr);
270 ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name);
271 
272 void debuggerd_init();
273 extern "C" abort_msg_t* g_abort_message;
274 extern "C" void notify_gdb_of_libraries();
275 
276 char* linker_get_error_buffer();
277 size_t linker_get_error_buffer_size();
278 
279 #endif
280