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 <inttypes.h> 20 #include <memory> 21 22 #include "base/logging.h" 23 #include "base/stringprintf.h" 24 #include "elf_file.h" 25 #include "elf_writer.h" 26 27 namespace art { 28 29 static const bool DEBUG_FIXUP = false; 30 31 bool ElfFixup::Fixup(File* file, uintptr_t oat_data_begin) { 32 std::string error_msg; 33 std::unique_ptr<ElfFile> elf_file(ElfFile::Open(file, true, false, &error_msg)); 34 CHECK(elf_file.get() != nullptr) << error_msg; 35 36 // Lookup "oatdata" symbol address. 37 Elf32_Addr oatdata_address = ElfWriter::GetOatDataAddress(elf_file.get()); 38 Elf32_Off base_address = oat_data_begin - oatdata_address; 39 40 if (!FixupDynamic(*elf_file.get(), base_address)) { 41 LOG(WARNING) << "Failed fo fixup .dynamic in " << file->GetPath(); 42 return false; 43 } 44 if (!FixupSectionHeaders(*elf_file.get(), base_address)) { 45 LOG(WARNING) << "Failed fo fixup section headers in " << file->GetPath(); 46 return false; 47 } 48 if (!FixupProgramHeaders(*elf_file.get(), base_address)) { 49 LOG(WARNING) << "Failed fo fixup program headers in " << file->GetPath(); 50 return false; 51 } 52 if (!FixupSymbols(*elf_file.get(), base_address, true)) { 53 LOG(WARNING) << "Failed fo fixup .dynsym in " << file->GetPath(); 54 return false; 55 } 56 if (!FixupSymbols(*elf_file.get(), base_address, false)) { 57 LOG(WARNING) << "Failed fo fixup .symtab in " << file->GetPath(); 58 return false; 59 } 60 if (!FixupRelocations(*elf_file.get(), base_address)) { 61 LOG(WARNING) << "Failed fo fixup .rel.dyn in " << file->GetPath(); 62 return false; 63 } 64 return true; 65 } 66 67 68 bool ElfFixup::FixupDynamic(ElfFile& elf_file, uintptr_t base_address) { 69 for (Elf32_Word i = 0; i < elf_file.GetDynamicNum(); i++) { 70 Elf32_Dyn& elf_dyn = elf_file.GetDynamic(i); 71 Elf32_Word d_tag = elf_dyn.d_tag; 72 if (IsDynamicSectionPointer(d_tag, elf_file.GetHeader().e_machine)) { 73 uint32_t d_ptr = elf_dyn.d_un.d_ptr; 74 if (DEBUG_FIXUP) { 75 LOG(INFO) << StringPrintf("In %s moving Elf32_Dyn[%d] from 0x%08x to 0x%08" PRIxPTR, 76 elf_file.GetFile().GetPath().c_str(), i, 77 d_ptr, d_ptr + base_address); 78 } 79 d_ptr += base_address; 80 elf_dyn.d_un.d_ptr = d_ptr; 81 } 82 } 83 return true; 84 } 85 86 bool ElfFixup::FixupSectionHeaders(ElfFile& elf_file, uintptr_t base_address) { 87 for (Elf32_Word i = 0; i < elf_file.GetSectionHeaderNum(); i++) { 88 Elf32_Shdr* sh = elf_file.GetSectionHeader(i); 89 CHECK(sh != nullptr); 90 // 0 implies that the section will not exist in the memory of the process 91 if (sh->sh_addr == 0) { 92 continue; 93 } 94 if (DEBUG_FIXUP) { 95 LOG(INFO) << StringPrintf("In %s moving Elf32_Shdr[%d] from 0x%08x to 0x%08" PRIxPTR, 96 elf_file.GetFile().GetPath().c_str(), i, 97 sh->sh_addr, sh->sh_addr + base_address); 98 } 99 sh->sh_addr += base_address; 100 } 101 return true; 102 } 103 104 bool ElfFixup::FixupProgramHeaders(ElfFile& elf_file, uintptr_t base_address) { 105 // TODO: ELFObjectFile doesn't have give to Elf32_Phdr, so we do that ourselves for now. 106 for (Elf32_Word i = 0; i < elf_file.GetProgramHeaderNum(); i++) { 107 Elf32_Phdr* ph = elf_file.GetProgramHeader(i); 108 CHECK(ph != nullptr); 109 CHECK_EQ(ph->p_vaddr, ph->p_paddr) << elf_file.GetFile().GetPath() << " i=" << i; 110 CHECK((ph->p_align == 0) || (0 == ((ph->p_vaddr - ph->p_offset) & (ph->p_align - 1)))) 111 << elf_file.GetFile().GetPath() << " i=" << i; 112 if (DEBUG_FIXUP) { 113 LOG(INFO) << StringPrintf("In %s moving Elf32_Phdr[%d] from 0x%08x to 0x%08" PRIxPTR, 114 elf_file.GetFile().GetPath().c_str(), i, 115 ph->p_vaddr, ph->p_vaddr + base_address); 116 } 117 ph->p_vaddr += base_address; 118 ph->p_paddr += base_address; 119 CHECK((ph->p_align == 0) || (0 == ((ph->p_vaddr - ph->p_offset) & (ph->p_align - 1)))) 120 << elf_file.GetFile().GetPath() << " i=" << i; 121 } 122 return true; 123 } 124 125 bool ElfFixup::FixupSymbols(ElfFile& elf_file, uintptr_t base_address, bool dynamic) { 126 Elf32_Word section_type = dynamic ? SHT_DYNSYM : SHT_SYMTAB; 127 // TODO: Unfortunate ELFObjectFile has protected symbol access, so use ElfFile 128 Elf32_Shdr* symbol_section = elf_file.FindSectionByType(section_type); 129 if (symbol_section == nullptr) { 130 // file is missing optional .symtab 131 CHECK(!dynamic) << elf_file.GetFile().GetPath(); 132 return true; 133 } 134 for (uint32_t i = 0; i < elf_file.GetSymbolNum(*symbol_section); i++) { 135 Elf32_Sym* symbol = elf_file.GetSymbol(section_type, i); 136 CHECK(symbol != nullptr); 137 if (symbol->st_value != 0) { 138 if (DEBUG_FIXUP) { 139 LOG(INFO) << StringPrintf("In %s moving Elf32_Sym[%d] from 0x%08x to 0x%08" PRIxPTR, 140 elf_file.GetFile().GetPath().c_str(), i, 141 symbol->st_value, symbol->st_value + base_address); 142 } 143 symbol->st_value += base_address; 144 } 145 } 146 return true; 147 } 148 149 bool ElfFixup::FixupRelocations(ElfFile& elf_file, uintptr_t base_address) { 150 for (Elf32_Word i = 0; i < elf_file.GetSectionHeaderNum(); i++) { 151 Elf32_Shdr* sh = elf_file.GetSectionHeader(i); 152 CHECK(sh != nullptr); 153 if (sh->sh_type == SHT_REL) { 154 for (uint32_t i = 0; i < elf_file.GetRelNum(*sh); i++) { 155 Elf32_Rel& rel = elf_file.GetRel(*sh, i); 156 if (DEBUG_FIXUP) { 157 LOG(INFO) << StringPrintf("In %s moving Elf32_Rel[%d] from 0x%08x to 0x%08" PRIxPTR, 158 elf_file.GetFile().GetPath().c_str(), i, 159 rel.r_offset, rel.r_offset + base_address); 160 } 161 rel.r_offset += base_address; 162 } 163 } else if (sh->sh_type == SHT_RELA) { 164 for (uint32_t i = 0; i < elf_file.GetRelaNum(*sh); i++) { 165 Elf32_Rela& rela = elf_file.GetRela(*sh, i); 166 if (DEBUG_FIXUP) { 167 LOG(INFO) << StringPrintf("In %s moving Elf32_Rela[%d] from 0x%08x to 0x%08" PRIxPTR, 168 elf_file.GetFile().GetPath().c_str(), i, 169 rela.r_offset, rela.r_offset + base_address); 170 } 171 rela.r_offset += base_address; 172 } 173 } 174 } 175 return true; 176 } 177 178 } // namespace art 179
