1 /*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "elf_fixup.h"
18
19 #include "base/logging.h"
20 #include "base/stringprintf.h"
21 #include "elf_file.h"
22 #include "elf_writer.h"
23 #include "UniquePtr.h"
24
25 namespace art {
26
27 static const bool DEBUG_FIXUP = false;
28
Fixup(File * file,uintptr_t oat_data_begin)29 bool ElfFixup::Fixup(File* file, uintptr_t oat_data_begin) {
30 UniquePtr<ElfFile> elf_file(ElfFile::Open(file, true, false));
31 CHECK(elf_file.get() != NULL);
32
33 // Lookup "oatdata" symbol address.
34 ::llvm::ELF::Elf32_Addr oatdata_address = ElfWriter::GetOatDataAddress(elf_file.get());
35 ::llvm::ELF::Elf32_Off base_address = oat_data_begin - oatdata_address;
36
37 if (!FixupDynamic(*elf_file.get(), base_address)) {
38 LOG(WARNING) << "Failed fo fixup .dynamic in " << file->GetPath();
39 return false;
40 }
41 if (!FixupSectionHeaders(*elf_file.get(), base_address)) {
42 LOG(WARNING) << "Failed fo fixup section headers in " << file->GetPath();
43 return false;
44 }
45 if (!FixupProgramHeaders(*elf_file.get(), base_address)) {
46 LOG(WARNING) << "Failed fo fixup program headers in " << file->GetPath();
47 return false;
48 }
49 if (!FixupSymbols(*elf_file.get(), base_address, true)) {
50 LOG(WARNING) << "Failed fo fixup .dynsym in " << file->GetPath();
51 return false;
52 }
53 if (!FixupSymbols(*elf_file.get(), base_address, false)) {
54 LOG(WARNING) << "Failed fo fixup .symtab in " << file->GetPath();
55 return false;
56 }
57 if (!FixupRelocations(*elf_file.get(), base_address)) {
58 LOG(WARNING) << "Failed fo fixup .rel.dyn in " << file->GetPath();
59 return false;
60 }
61 return true;
62 }
63
64 // MIPS seems to break the rules d_val vs d_ptr even though their values are between DT_LOPROC and DT_HIPROC
65 #define DT_MIPS_RLD_VERSION 0x70000001 // d_val
66 #define DT_MIPS_TIME_STAMP 0x70000002 // d_val
67 #define DT_MIPS_ICHECKSUM 0x70000003 // d_val
68 #define DT_MIPS_IVERSION 0x70000004 // d_val
69 #define DT_MIPS_FLAGS 0x70000005 // d_val
70 #define DT_MIPS_BASE_ADDRESS 0x70000006 // d_ptr
71 #define DT_MIPS_CONFLICT 0x70000008 // d_ptr
72 #define DT_MIPS_LIBLIST 0x70000009 // d_ptr
73 #define DT_MIPS_LOCAL_GOTNO 0x7000000A // d_val
74 #define DT_MIPS_CONFLICTNO 0x7000000B // d_val
75 #define DT_MIPS_LIBLISTNO 0x70000010 // d_val
76 #define DT_MIPS_SYMTABNO 0x70000011 // d_val
77 #define DT_MIPS_UNREFEXTNO 0x70000012 // d_val
78 #define DT_MIPS_GOTSYM 0x70000013 // d_val
79 #define DT_MIPS_HIPAGENO 0x70000014 // d_val
80 #define DT_MIPS_RLD_MAP 0x70000016 // d_ptr
81
FixupDynamic(ElfFile & elf_file,uintptr_t base_address)82 bool ElfFixup::FixupDynamic(ElfFile& elf_file, uintptr_t base_address) {
83 for (::llvm::ELF::Elf32_Word i = 0; i < elf_file.GetDynamicNum(); i++) {
84 ::llvm::ELF::Elf32_Dyn& elf_dyn = elf_file.GetDynamic(i);
85 ::llvm::ELF::Elf32_Word d_tag = elf_dyn.d_tag;
86 bool elf_dyn_needs_fixup = false;
87 switch (d_tag) {
88 // case 1: well known d_tag values that imply Elf32_Dyn.d_un contains an address in d_ptr
89 case ::llvm::ELF::DT_PLTGOT:
90 case ::llvm::ELF::DT_HASH:
91 case ::llvm::ELF::DT_STRTAB:
92 case ::llvm::ELF::DT_SYMTAB:
93 case ::llvm::ELF::DT_RELA:
94 case ::llvm::ELF::DT_INIT:
95 case ::llvm::ELF::DT_FINI:
96 case ::llvm::ELF::DT_REL:
97 case ::llvm::ELF::DT_DEBUG:
98 case ::llvm::ELF::DT_JMPREL: {
99 elf_dyn_needs_fixup = true;
100 break;
101 }
102 // d_val or ignored values
103 case ::llvm::ELF::DT_NULL:
104 case ::llvm::ELF::DT_NEEDED:
105 case ::llvm::ELF::DT_PLTRELSZ:
106 case ::llvm::ELF::DT_RELASZ:
107 case ::llvm::ELF::DT_RELAENT:
108 case ::llvm::ELF::DT_STRSZ:
109 case ::llvm::ELF::DT_SYMENT:
110 case ::llvm::ELF::DT_SONAME:
111 case ::llvm::ELF::DT_RPATH:
112 case ::llvm::ELF::DT_SYMBOLIC:
113 case ::llvm::ELF::DT_RELSZ:
114 case ::llvm::ELF::DT_RELENT:
115 case ::llvm::ELF::DT_PLTREL:
116 case ::llvm::ELF::DT_TEXTREL:
117 case ::llvm::ELF::DT_BIND_NOW:
118 case ::llvm::ELF::DT_INIT_ARRAYSZ:
119 case ::llvm::ELF::DT_FINI_ARRAYSZ:
120 case ::llvm::ELF::DT_RUNPATH:
121 case ::llvm::ELF::DT_FLAGS: {
122 break;
123 }
124 // boundary values that should not be used
125 case ::llvm::ELF::DT_ENCODING:
126 case ::llvm::ELF::DT_LOOS:
127 case ::llvm::ELF::DT_HIOS:
128 case ::llvm::ELF::DT_LOPROC:
129 case ::llvm::ELF::DT_HIPROC: {
130 LOG(FATAL) << "Illegal d_tag value 0x" << std::hex << d_tag;
131 break;
132 }
133 default: {
134 // case 2: "regular" DT_* ranges where even d_tag values imply an address in d_ptr
135 if ((::llvm::ELF::DT_ENCODING < d_tag && d_tag < ::llvm::ELF::DT_LOOS)
136 || (::llvm::ELF::DT_LOOS < d_tag && d_tag < ::llvm::ELF::DT_HIOS)
137 || (::llvm::ELF::DT_LOPROC < d_tag && d_tag < ::llvm::ELF::DT_HIPROC)) {
138 // Special case for MIPS which breaks the regular rules between DT_LOPROC and DT_HIPROC
139 if (elf_file.GetHeader().e_machine == ::llvm::ELF::EM_MIPS) {
140 switch (d_tag) {
141 case DT_MIPS_RLD_VERSION:
142 case DT_MIPS_TIME_STAMP:
143 case DT_MIPS_ICHECKSUM:
144 case DT_MIPS_IVERSION:
145 case DT_MIPS_FLAGS:
146 case DT_MIPS_LOCAL_GOTNO:
147 case DT_MIPS_CONFLICTNO:
148 case DT_MIPS_LIBLISTNO:
149 case DT_MIPS_SYMTABNO:
150 case DT_MIPS_UNREFEXTNO:
151 case DT_MIPS_GOTSYM:
152 case DT_MIPS_HIPAGENO: {
153 break;
154 }
155 case DT_MIPS_BASE_ADDRESS:
156 case DT_MIPS_CONFLICT:
157 case DT_MIPS_LIBLIST:
158 case DT_MIPS_RLD_MAP: {
159 elf_dyn_needs_fixup = true;
160 break;
161 }
162 default: {
163 LOG(FATAL) << "Unknown MIPS d_tag value 0x" << std::hex << d_tag;
164 break;
165 }
166 }
167 } else if ((elf_dyn.d_tag % 2) == 0) {
168 elf_dyn_needs_fixup = true;
169 }
170 } else {
171 LOG(FATAL) << "Unknown d_tag value 0x" << std::hex << d_tag;
172 }
173 break;
174 }
175 }
176 if (elf_dyn_needs_fixup) {
177 uint32_t d_ptr = elf_dyn.d_un.d_ptr;
178 if (DEBUG_FIXUP) {
179 LOG(INFO) << StringPrintf("In %s moving Elf32_Dyn[%d] from 0x%08x to 0x%08x",
180 elf_file.GetFile().GetPath().c_str(), i,
181 d_ptr, d_ptr + base_address);
182 }
183 d_ptr += base_address;
184 elf_dyn.d_un.d_ptr = d_ptr;
185 }
186 }
187 return true;
188 }
189
FixupSectionHeaders(ElfFile & elf_file,uintptr_t base_address)190 bool ElfFixup::FixupSectionHeaders(ElfFile& elf_file, uintptr_t base_address) {
191 for (::llvm::ELF::Elf32_Word i = 0; i < elf_file.GetSectionHeaderNum(); i++) {
192 ::llvm::ELF::Elf32_Shdr& sh = elf_file.GetSectionHeader(i);
193 // 0 implies that the section will not exist in the memory of the process
194 if (sh.sh_addr == 0) {
195 continue;
196 }
197 if (DEBUG_FIXUP) {
198 LOG(INFO) << StringPrintf("In %s moving Elf32_Shdr[%d] from 0x%08x to 0x%08x",
199 elf_file.GetFile().GetPath().c_str(), i,
200 sh.sh_addr, sh.sh_addr + base_address);
201 }
202 sh.sh_addr += base_address;
203 }
204 return true;
205 }
206
FixupProgramHeaders(ElfFile & elf_file,uintptr_t base_address)207 bool ElfFixup::FixupProgramHeaders(ElfFile& elf_file, uintptr_t base_address) {
208 // TODO: ELFObjectFile doesn't have give to Elf32_Phdr, so we do that ourselves for now.
209 for (::llvm::ELF::Elf32_Word i = 0; i < elf_file.GetProgramHeaderNum(); i++) {
210 ::llvm::ELF::Elf32_Phdr& ph = elf_file.GetProgramHeader(i);
211 CHECK_EQ(ph.p_vaddr, ph.p_paddr) << elf_file.GetFile().GetPath() << " i=" << i;
212 CHECK((ph.p_align == 0) || (0 == ((ph.p_vaddr - ph.p_offset) & (ph.p_align - 1))))
213 << elf_file.GetFile().GetPath() << " i=" << i;
214 if (DEBUG_FIXUP) {
215 LOG(INFO) << StringPrintf("In %s moving Elf32_Phdr[%d] from 0x%08x to 0x%08x",
216 elf_file.GetFile().GetPath().c_str(), i,
217 ph.p_vaddr, ph.p_vaddr + base_address);
218 }
219 ph.p_vaddr += base_address;
220 ph.p_paddr += base_address;
221 CHECK((ph.p_align == 0) || (0 == ((ph.p_vaddr - ph.p_offset) & (ph.p_align - 1))))
222 << elf_file.GetFile().GetPath() << " i=" << i;
223 }
224 return true;
225 }
226
FixupSymbols(ElfFile & elf_file,uintptr_t base_address,bool dynamic)227 bool ElfFixup::FixupSymbols(ElfFile& elf_file, uintptr_t base_address, bool dynamic) {
228 ::llvm::ELF::Elf32_Word section_type = dynamic ? ::llvm::ELF::SHT_DYNSYM : ::llvm::ELF::SHT_SYMTAB;
229 // TODO: Unfortunate ELFObjectFile has protected symbol access, so use ElfFile
230 ::llvm::ELF::Elf32_Shdr* symbol_section = elf_file.FindSectionByType(section_type);
231 if (symbol_section == NULL) {
232 // file is missing optional .symtab
233 CHECK(!dynamic) << elf_file.GetFile().GetPath();
234 return true;
235 }
236 for (uint32_t i = 0; i < elf_file.GetSymbolNum(*symbol_section); i++) {
237 ::llvm::ELF::Elf32_Sym& symbol = elf_file.GetSymbol(section_type, i);
238 if (symbol.st_value != 0) {
239 if (DEBUG_FIXUP) {
240 LOG(INFO) << StringPrintf("In %s moving Elf32_Sym[%d] from 0x%08x to 0x%08x",
241 elf_file.GetFile().GetPath().c_str(), i,
242 symbol.st_value, symbol.st_value + base_address);
243 }
244 symbol.st_value += base_address;
245 }
246 }
247 return true;
248 }
249
FixupRelocations(ElfFile & elf_file,uintptr_t base_address)250 bool ElfFixup::FixupRelocations(ElfFile& elf_file, uintptr_t base_address) {
251 for (llvm::ELF::Elf32_Word i = 0; i < elf_file.GetSectionHeaderNum(); i++) {
252 llvm::ELF::Elf32_Shdr& sh = elf_file.GetSectionHeader(i);
253 if (sh.sh_type == llvm::ELF::SHT_REL) {
254 for (uint32_t i = 0; i < elf_file.GetRelNum(sh); i++) {
255 llvm::ELF::Elf32_Rel& rel = elf_file.GetRel(sh, i);
256 if (DEBUG_FIXUP) {
257 LOG(INFO) << StringPrintf("In %s moving Elf32_Rel[%d] from 0x%08x to 0x%08x",
258 elf_file.GetFile().GetPath().c_str(), i,
259 rel.r_offset, rel.r_offset + base_address);
260 }
261 rel.r_offset += base_address;
262 }
263 } else if (sh.sh_type == llvm::ELF::SHT_RELA) {
264 for (uint32_t i = 0; i < elf_file.GetRelaNum(sh); i++) {
265 llvm::ELF::Elf32_Rela& rela = elf_file.GetRela(sh, i);
266 if (DEBUG_FIXUP) {
267 LOG(INFO) << StringPrintf("In %s moving Elf32_Rela[%d] from 0x%08x to 0x%08x",
268 elf_file.GetFile().GetPath().c_str(), i,
269 rela.r_offset, rela.r_offset + base_address);
270 }
271 rela.r_offset += base_address;
272 }
273 }
274 }
275 return true;
276 }
277
278 } // namespace art
279