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Diffstat (limited to '')
| -rw-r--r-- | build/unix/elfhack/elf.cpp | 935 |
1 files changed, 935 insertions, 0 deletions
diff --git a/build/unix/elfhack/elf.cpp b/build/unix/elfhack/elf.cpp new file mode 100644 index 0000000000..b2a21e4901 --- /dev/null +++ b/build/unix/elfhack/elf.cpp @@ -0,0 +1,935 @@ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#undef NDEBUG +#include <cstring> +#include <assert.h> +#include "elfxx.h" + +template <class endian, typename R, typename T> +void Elf_Ehdr_Traits::swap(T& t, R& r) { + memcpy(r.e_ident, t.e_ident, sizeof(r.e_ident)); + r.e_type = endian::swap(t.e_type); + r.e_machine = endian::swap(t.e_machine); + r.e_version = endian::swap(t.e_version); + r.e_entry = endian::swap(t.e_entry); + r.e_phoff = endian::swap(t.e_phoff); + r.e_shoff = endian::swap(t.e_shoff); + r.e_flags = endian::swap(t.e_flags); + r.e_ehsize = endian::swap(t.e_ehsize); + r.e_phentsize = endian::swap(t.e_phentsize); + r.e_phnum = endian::swap(t.e_phnum); + r.e_shentsize = endian::swap(t.e_shentsize); + r.e_shnum = endian::swap(t.e_shnum); + r.e_shstrndx = endian::swap(t.e_shstrndx); +} + +template <class endian, typename R, typename T> +void Elf_Phdr_Traits::swap(T& t, R& r) { + r.p_type = endian::swap(t.p_type); + r.p_offset = endian::swap(t.p_offset); + r.p_vaddr = endian::swap(t.p_vaddr); + r.p_paddr = endian::swap(t.p_paddr); + r.p_filesz = endian::swap(t.p_filesz); + r.p_memsz = endian::swap(t.p_memsz); + r.p_flags = endian::swap(t.p_flags); + r.p_align = endian::swap(t.p_align); +} + +template <class endian, typename R, typename T> +void Elf_Shdr_Traits::swap(T& t, R& r) { + r.sh_name = endian::swap(t.sh_name); + r.sh_type = endian::swap(t.sh_type); + r.sh_flags = endian::swap(t.sh_flags); + r.sh_addr = endian::swap(t.sh_addr); + r.sh_offset = endian::swap(t.sh_offset); + r.sh_size = endian::swap(t.sh_size); + r.sh_link = endian::swap(t.sh_link); + r.sh_info = endian::swap(t.sh_info); + r.sh_addralign = endian::swap(t.sh_addralign); + r.sh_entsize = endian::swap(t.sh_entsize); +} + +template <class endian, typename R, typename T> +void Elf_Dyn_Traits::swap(T& t, R& r) { + r.d_tag = endian::swap(t.d_tag); + r.d_un.d_val = endian::swap(t.d_un.d_val); +} + +template <class endian, typename R, typename T> +void Elf_Sym_Traits::swap(T& t, R& r) { + r.st_name = endian::swap(t.st_name); + r.st_value = endian::swap(t.st_value); + r.st_size = endian::swap(t.st_size); + r.st_info = t.st_info; + r.st_other = t.st_other; + r.st_shndx = endian::swap(t.st_shndx); +} + +template <class endian> +struct _Rel_info { + static inline void swap(Elf32_Word& t, Elf32_Word& r) { r = endian::swap(t); } + static inline void swap(Elf64_Xword& t, Elf64_Xword& r) { + r = endian::swap(t); + } + static inline void swap(Elf64_Xword& t, Elf32_Word& r) { + r = endian::swap(ELF32_R_INFO(ELF64_R_SYM(t), ELF64_R_TYPE(t))); + } + static inline void swap(Elf32_Word& t, Elf64_Xword& r) { + r = endian::swap(ELF64_R_INFO(ELF32_R_SYM(t), ELF32_R_TYPE(t))); + } +}; + +template <class endian, typename R, typename T> +void Elf_Rel_Traits::swap(T& t, R& r) { + r.r_offset = endian::swap(t.r_offset); + _Rel_info<endian>::swap(t.r_info, r.r_info); +} + +template <class endian, typename R, typename T> +void Elf_Rela_Traits::swap(T& t, R& r) { + r.r_offset = endian::swap(t.r_offset); + _Rel_info<endian>::swap(t.r_info, r.r_info); + r.r_addend = endian::swap(t.r_addend); +} + +static const Elf64_Shdr null64_section = {0, SHT_NULL, 0, 0, 0, + 0, SHN_UNDEF, 0, 0, 0}; + +Elf_Shdr null_section(null64_section); + +Elf_Ehdr::Elf_Ehdr(std::ifstream& file, unsigned char ei_class, + unsigned char ei_data) + : serializable<Elf_Ehdr_Traits>(file, ei_class, ei_data), + ElfSection(null_section, nullptr, nullptr) { + shdr.sh_size = Elf_Ehdr::size(ei_class); +} + +Elf::Elf(std::ifstream& file) { + if (!file.is_open()) throw std::runtime_error("Error opening file"); + + file.exceptions(std::ifstream::eofbit | std::ifstream::failbit | + std::ifstream::badbit); + // Read ELF magic number and identification information + unsigned char e_ident[EI_VERSION]; + file.seekg(0); + file.read((char*)e_ident, sizeof(e_ident)); + file.seekg(0); + ehdr = new Elf_Ehdr(file, e_ident[EI_CLASS], e_ident[EI_DATA]); + + // ELFOSABI_LINUX is kept unsupported because I haven't looked whether + // STB_GNU_UNIQUE or STT_GNU_IFUNC would need special casing. + if ((ehdr->e_ident[EI_OSABI] != ELFOSABI_NONE) && + (ehdr->e_ident[EI_ABIVERSION] != 0)) + throw std::runtime_error("unsupported ELF ABI"); + + if (ehdr->e_version != 1) throw std::runtime_error("unsupported ELF version"); + + // Sanity checks + if (ehdr->e_shnum == 0) + throw std::runtime_error("sstripped ELF files aren't supported"); + + if (ehdr->e_ehsize != Elf_Ehdr::size(e_ident[EI_CLASS])) + throw std::runtime_error( + "unsupported ELF inconsistency: ehdr.e_ehsize != sizeof(ehdr)"); + + if (ehdr->e_shentsize != Elf_Shdr::size(e_ident[EI_CLASS])) + throw std::runtime_error( + "unsupported ELF inconsistency: ehdr.e_shentsize != sizeof(shdr)"); + + if (ehdr->e_phnum == 0) { + if (ehdr->e_phoff != 0) + throw std::runtime_error( + "unsupported ELF inconsistency: e_phnum == 0 && e_phoff != 0"); + if (ehdr->e_phentsize != 0) + throw std::runtime_error( + "unsupported ELF inconsistency: e_phnum == 0 && e_phentsize != 0"); + } else if (ehdr->e_phoff != ehdr->e_ehsize) + throw std::runtime_error( + "unsupported ELF inconsistency: ehdr->e_phoff != ehdr->e_ehsize"); + else if (ehdr->e_phentsize != Elf_Phdr::size(e_ident[EI_CLASS])) + throw std::runtime_error( + "unsupported ELF inconsistency: ehdr->e_phentsize != sizeof(phdr)"); + + // Read section headers + Elf_Shdr** shdr = new Elf_Shdr*[ehdr->e_shnum]; + file.seekg(ehdr->e_shoff); + for (int i = 0; i < ehdr->e_shnum; i++) + shdr[i] = new Elf_Shdr(file, e_ident[EI_CLASS], e_ident[EI_DATA]); + + // Sanity check in section header for index 0 + if ((shdr[0]->sh_name != 0) || (shdr[0]->sh_type != SHT_NULL) || + (shdr[0]->sh_flags != 0) || (shdr[0]->sh_addr != 0) || + (shdr[0]->sh_offset != 0) || (shdr[0]->sh_size != 0) || + (shdr[0]->sh_link != SHN_UNDEF) || (shdr[0]->sh_info != 0) || + (shdr[0]->sh_addralign != 0) || (shdr[0]->sh_entsize != 0)) + throw std::runtime_error( + "Section header for index 0 contains unsupported values"); + + if ((shdr[ehdr->e_shstrndx]->sh_link != 0) || + (shdr[ehdr->e_shstrndx]->sh_info != 0)) + throw std::runtime_error( + "unsupported ELF content: string table with sh_link != 0 || sh_info != " + "0"); + + // Store these temporarily + tmp_shdr = shdr; + tmp_file = &file; + + // Fill sections list + sections = new ElfSection*[ehdr->e_shnum]; + for (int i = 0; i < ehdr->e_shnum; i++) sections[i] = nullptr; + for (int i = 1; i < ehdr->e_shnum; i++) { + // The .dynamic section is going to have references to other sections, + // so it's better to start with that one and recursively initialize those + // other sections first, to avoid possible infinite recursion (bug 1606739). + if (tmp_shdr[i]->sh_type == SHT_DYNAMIC) { + getSection(i); + } + } + for (int i = 1; i < ehdr->e_shnum; i++) { + if (sections[i] != nullptr) continue; + getSection(i); + } + Elf_Shdr s; + s.sh_name = 0; + s.sh_type = SHT_NULL; + s.sh_flags = 0; + s.sh_addr = 0; + s.sh_offset = ehdr->e_shoff; + s.sh_entsize = Elf_Shdr::size(e_ident[EI_CLASS]); + s.sh_size = s.sh_entsize * ehdr->e_shnum; + s.sh_link = 0; + s.sh_info = 0; + s.sh_addralign = (e_ident[EI_CLASS] == ELFCLASS32) ? 4 : 8; + shdr_section = new ElfSection(s, nullptr, nullptr); + + // Fake section for program headers + s.sh_offset = ehdr->e_phoff; + s.sh_addr = ehdr->e_phoff; + s.sh_entsize = Elf_Phdr::size(e_ident[EI_CLASS]); + s.sh_size = s.sh_entsize * ehdr->e_phnum; + phdr_section = new ElfSection(s, nullptr, nullptr); + + phdr_section->insertAfter(ehdr, false); + + sections[1]->insertAfter(phdr_section, false); + for (int i = 2; i < ehdr->e_shnum; i++) { + // TODO: this should be done in a better way + if ((shdr_section->getPrevious() == nullptr) && + (shdr[i]->sh_offset > ehdr->e_shoff)) { + shdr_section->insertAfter(sections[i - 1], false); + sections[i]->insertAfter(shdr_section, false); + } else + sections[i]->insertAfter(sections[i - 1], false); + } + if (shdr_section->getPrevious() == nullptr) + shdr_section->insertAfter(sections[ehdr->e_shnum - 1], false); + + tmp_file = nullptr; + tmp_shdr = nullptr; + for (int i = 0; i < ehdr->e_shnum; i++) delete shdr[i]; + delete[] shdr; + + eh_shstrndx = (ElfStrtab_Section*)sections[ehdr->e_shstrndx]; + + // Skip reading program headers if there aren't any + if (ehdr->e_phnum == 0) return; + + bool adjusted_phdr_section = false; + // Read program headers + file.seekg(ehdr->e_phoff); + for (int i = 0; i < ehdr->e_phnum; i++) { + Elf_Phdr phdr(file, e_ident[EI_CLASS], e_ident[EI_DATA]); + if (phdr.p_type == PT_LOAD) { + // Default alignment for PT_LOAD on x86-64 prevents elfhack from + // doing anything useful. However, the system doesn't actually + // require such a big alignment, so in order for elfhack to work + // efficiently, reduce alignment when it's originally the default + // one. + if ((ehdr->e_machine == EM_X86_64) && (phdr.p_align == 0x200000)) + phdr.p_align = 0x1000; + } + ElfSegment* segment = new ElfSegment(&phdr); + // Some segments aren't entirely filled (if at all) by sections + // For those, we use fake sections + if ((phdr.p_type == PT_LOAD) && (phdr.p_offset == 0)) { + // Use a fake section for ehdr and phdr + ehdr->getShdr().sh_addr = phdr.p_vaddr; + if (!adjusted_phdr_section) { + phdr_section->getShdr().sh_addr += phdr.p_vaddr; + adjusted_phdr_section = true; + } + segment->addSection(ehdr); + segment->addSection(phdr_section); + } + if (phdr.p_type == PT_PHDR) { + if (!adjusted_phdr_section) { + phdr_section->getShdr().sh_addr = phdr.p_vaddr; + adjusted_phdr_section = true; + } + segment->addSection(phdr_section); + } + for (int j = 1; j < ehdr->e_shnum; j++) + if (phdr.contains(sections[j])) segment->addSection(sections[j]); + // Make sure that our view of segments corresponds to the original + // ELF file. + // GNU gold likes to start some segments before the first section + // they contain. https://sourceware.org/bugzilla/show_bug.cgi?id=19392 + unsigned int gold_adjustment = segment->getAddr() - phdr.p_vaddr; + assert(segment->getFileSize() == phdr.p_filesz - gold_adjustment); + // gold makes TLS segments end on an aligned virtual address, even + // when the underlying section ends before that, while bfd ld + // doesn't. It's fine if we don't keep that alignment. + unsigned int memsize = segment->getMemSize(); + if (phdr.p_type == PT_TLS && memsize != phdr.p_memsz) { + unsigned int align = segment->getAlign(); + memsize = (memsize + align - 1) & ~(align - 1); + } + assert(memsize == phdr.p_memsz - gold_adjustment); + segments.push_back(segment); + } + + new (&eh_entry) ElfLocation(ehdr->e_entry, this); +} + +Elf::~Elf() { + for (std::vector<ElfSegment*>::iterator seg = segments.begin(); + seg != segments.end(); seg++) + delete *seg; + delete[] sections; + ElfSection* section = ehdr; + while (section != nullptr) { + ElfSection* next = section->getNext(); + delete section; + section = next; + } +} + +// TODO: This shouldn't fail after inserting sections +ElfSection* Elf::getSection(int index) { + if ((index < -1) || (index >= ehdr->e_shnum)) + throw std::runtime_error("Section index out of bounds"); + if (index == -1) + index = ehdr->e_shstrndx; // TODO: should be fixed to use the actual + // current number + // Special case: the section at index 0 is void + if (index == 0) return nullptr; + // Infinite recursion guard + if (sections[index] == (ElfSection*)this) return nullptr; + if (sections[index] == nullptr) { + sections[index] = (ElfSection*)this; + switch (tmp_shdr[index]->sh_type) { + case SHT_DYNAMIC: + sections[index] = + new ElfDynamic_Section(*tmp_shdr[index], tmp_file, this); + break; + case SHT_REL: + sections[index] = + new ElfRel_Section<Elf_Rel>(*tmp_shdr[index], tmp_file, this); + break; + case SHT_RELA: + sections[index] = + new ElfRel_Section<Elf_Rela>(*tmp_shdr[index], tmp_file, this); + break; + case SHT_DYNSYM: + case SHT_SYMTAB: + sections[index] = + new ElfSymtab_Section(*tmp_shdr[index], tmp_file, this); + break; + case SHT_STRTAB: + sections[index] = + new ElfStrtab_Section(*tmp_shdr[index], tmp_file, this); + break; + default: + sections[index] = new ElfSection(*tmp_shdr[index], tmp_file, this); + } + } + return sections[index]; +} + +ElfSection* Elf::getSectionAt(Elf64_Off offset) { + for (int i = 1; i < ehdr->e_shnum; i++) { + ElfSection* section = getSection(i); + if ((section != nullptr) && (section->getFlags() & SHF_ALLOC) && + !(section->getFlags() & SHF_TLS) && (offset >= section->getAddr()) && + (offset < section->getAddr() + section->getSize())) + return section; + } + return nullptr; +} + +ElfSegment* Elf::getSegmentByType(unsigned int type, ElfSegment* last) { + std::vector<ElfSegment*>::iterator seg; + if (last) { + seg = std::find(segments.begin(), segments.end(), last); + ++seg; + } else + seg = segments.begin(); + for (; seg != segments.end(); seg++) + if ((*seg)->getType() == type) return *seg; + return nullptr; +} + +void Elf::removeSegment(ElfSegment* segment) { + if (!segment) return; + std::vector<ElfSegment*>::iterator seg; + seg = std::find(segments.begin(), segments.end(), segment); + if (seg == segments.end()) return; + segment->clear(); + segments.erase(seg); +} + +ElfDynamic_Section* Elf::getDynSection() { + for (std::vector<ElfSegment*>::iterator seg = segments.begin(); + seg != segments.end(); seg++) + if (((*seg)->getType() == PT_DYNAMIC) && + ((*seg)->getFirstSection() != nullptr) && + (*seg)->getFirstSection()->getType() == SHT_DYNAMIC) + return (ElfDynamic_Section*)(*seg)->getFirstSection(); + + return nullptr; +} + +void Elf::normalize() { + // fixup section headers sh_name; TODO: that should be done by sections + // themselves + for (ElfSection* section = ehdr; section != nullptr; + section = section->getNext()) { + if (section->getIndex() == 0) + continue; + else + ehdr->e_shnum = section->getIndex() + 1; + section->getShdr().sh_name = eh_shstrndx->getStrIndex(section->getName()); + } + ehdr->markDirty(); + // Check segments consistency + int i = 0; + for (std::vector<ElfSegment*>::iterator seg = segments.begin(); + seg != segments.end(); seg++, i++) { + std::list<ElfSection*>::iterator it = (*seg)->begin(); + for (ElfSection* last = *(it++); it != (*seg)->end(); last = *(it++)) { + if (((*it)->getType() != SHT_NOBITS) && + ((*it)->getAddr() - last->getAddr()) != + ((*it)->getOffset() - last->getOffset())) { + throw std::runtime_error("Segments inconsistency"); + } + } + } + + ElfSegment* prevLoad = nullptr; + for (auto& it : segments) { + if (it->getType() == PT_LOAD) { + if (prevLoad) { + size_t alignedPrevEnd = (prevLoad->getAddr() + prevLoad->getMemSize() + + prevLoad->getAlign() - 1) & + ~(prevLoad->getAlign() - 1); + size_t alignedStart = it->getAddr() & ~(it->getAlign() - 1); + if (alignedPrevEnd > alignedStart) { + throw std::runtime_error("Segments overlap"); + } + } + prevLoad = it; + } + } + + // fixup ehdr before writing + if (ehdr->e_phnum != segments.size()) { + ehdr->e_phnum = segments.size(); + phdr_section->getShdr().sh_size = + segments.size() * Elf_Phdr::size(ehdr->e_ident[EI_CLASS]); + phdr_section->getNext()->markDirty(); + } + // fixup shdr before writing + if (ehdr->e_shnum != shdr_section->getSize() / shdr_section->getEntSize()) + shdr_section->getShdr().sh_size = + ehdr->e_shnum * Elf_Shdr::size(ehdr->e_ident[EI_CLASS]); + ehdr->e_shoff = shdr_section->getOffset(); + ehdr->e_entry = eh_entry.getValue(); + ehdr->e_shstrndx = eh_shstrndx->getIndex(); + + // Check sections consistency + unsigned int minOffset = 0; + for (ElfSection* section = ehdr; section != nullptr; + section = section->getNext()) { + unsigned int offset = section->getOffset(); + if (offset < minOffset) { + throw std::runtime_error("Sections overlap"); + } + if (section->getType() != SHT_NOBITS) { + minOffset = offset + section->getSize(); + } + } +} + +void Elf::write(std::ofstream& file) { + normalize(); + for (ElfSection* section = ehdr; section != nullptr; + section = section->getNext()) { + file.seekp(section->getOffset()); + if (section == phdr_section) { + for (std::vector<ElfSegment*>::iterator seg = segments.begin(); + seg != segments.end(); seg++) { + Elf_Phdr phdr; + phdr.p_type = (*seg)->getType(); + phdr.p_flags = (*seg)->getFlags(); + phdr.p_offset = (*seg)->getOffset(); + phdr.p_vaddr = (*seg)->getAddr(); + phdr.p_paddr = phdr.p_vaddr + (*seg)->getVPDiff(); + phdr.p_filesz = (*seg)->getFileSize(); + phdr.p_memsz = (*seg)->getMemSize(); + phdr.p_align = (*seg)->getAlign(); + phdr.serialize(file, ehdr->e_ident[EI_CLASS], ehdr->e_ident[EI_DATA]); + } + } else if (section == shdr_section) { + null_section.serialize(file, ehdr->e_ident[EI_CLASS], + ehdr->e_ident[EI_DATA]); + for (ElfSection* sec = ehdr; sec != nullptr; sec = sec->getNext()) { + if (sec->getType() != SHT_NULL) + sec->getShdr().serialize(file, ehdr->e_ident[EI_CLASS], + ehdr->e_ident[EI_DATA]); + } + } else + section->serialize(file, ehdr->e_ident[EI_CLASS], ehdr->e_ident[EI_DATA]); + } +} + +ElfSection::ElfSection(Elf_Shdr& s, std::ifstream* file, Elf* parent) + : shdr(s), + link(shdr.sh_link == SHN_UNDEF ? nullptr + : parent->getSection(shdr.sh_link)), + next(nullptr), + previous(nullptr), + index(-1) { + if ((file == nullptr) || (shdr.sh_type == SHT_NULL) || + (shdr.sh_type == SHT_NOBITS)) + data = nullptr; + else { + data = static_cast<char*>(malloc(shdr.sh_size)); + if (!data) { + throw std::runtime_error("Could not malloc ElfSection data"); + } + auto pos = file->tellg(); + file->seekg(shdr.sh_offset); + file->read(data, shdr.sh_size); + file->seekg(pos); + } + if (shdr.sh_name == 0) + name = nullptr; + else { + ElfStrtab_Section* strtab = (ElfStrtab_Section*)parent->getSection(-1); + // Special case (see elfgeneric.cpp): if strtab is nullptr, the + // section being created is the strtab. + if (strtab == nullptr) + name = &data[shdr.sh_name]; + else + name = strtab->getStr(shdr.sh_name); + } + // Only SHT_REL/SHT_RELA sections use sh_info to store a section + // number. + if ((shdr.sh_type == SHT_REL) || (shdr.sh_type == SHT_RELA)) + info.section = shdr.sh_info ? parent->getSection(shdr.sh_info) : nullptr; + else + info.index = shdr.sh_info; +} + +Elf64_Addr ElfSection::getAddr() { + if (shdr.sh_addr != (Elf64_Addr)-1) return shdr.sh_addr; + + // It should be safe to adjust sh_addr for all allocated sections that + // are neither SHT_NOBITS nor SHT_PROGBITS + if ((previous != nullptr) && isRelocatable()) { + unsigned int addr = previous->getAddr(); + if (previous->getType() != SHT_NOBITS) addr += previous->getSize(); + + if (addr & (getAddrAlign() - 1)) addr = (addr | (getAddrAlign() - 1)) + 1; + + return (shdr.sh_addr = addr); + } + return shdr.sh_addr; +} + +Elf64_Off ElfSection::getOffset() { + if (shdr.sh_offset != (Elf64_Off)-1) return shdr.sh_offset; + + if (previous == nullptr) return (shdr.sh_offset = 0); + + Elf64_Off offset = previous->getOffset(); + + ElfSegment* ptload = getSegmentByType(PT_LOAD); + ElfSegment* prev_ptload = previous->getSegmentByType(PT_LOAD); + + if (ptload && (ptload == prev_ptload)) { + offset += getAddr() - previous->getAddr(); + return (shdr.sh_offset = offset); + } + + if (previous->getType() != SHT_NOBITS) offset += previous->getSize(); + + Elf32_Word align = 0x1000; + for (std::vector<ElfSegment*>::iterator seg = segments.begin(); + seg != segments.end(); seg++) + align = std::max(align, (*seg)->getAlign()); + + Elf32_Word mask = align - 1; + // SHF_TLS is used for .tbss which is some kind of special case. + if (((getType() != SHT_NOBITS) || (getFlags() & SHF_TLS)) && + (getFlags() & SHF_ALLOC)) { + if ((getAddr() & mask) < (offset & mask)) + offset = (offset | mask) + (getAddr() & mask) + 1; + else + offset = (offset & ~mask) + (getAddr() & mask); + } + if ((getType() != SHT_NOBITS) && (offset & (getAddrAlign() - 1))) + offset = (offset | (getAddrAlign() - 1)) + 1; + + return (shdr.sh_offset = offset); +} + +int ElfSection::getIndex() { + if (index != -1) return index; + if (getType() == SHT_NULL) return (index = 0); + ElfSection* reference; + for (reference = previous; + (reference != nullptr) && (reference->getType() == SHT_NULL); + reference = reference->getPrevious()) + ; + if (reference == nullptr) return (index = 1); + return (index = reference->getIndex() + 1); +} + +Elf_Shdr& ElfSection::getShdr() { + getOffset(); + if (shdr.sh_link == (Elf64_Word)-1) + shdr.sh_link = getLink() ? getLink()->getIndex() : 0; + if (shdr.sh_info == (Elf64_Word)-1) + shdr.sh_info = ((getType() == SHT_REL) || (getType() == SHT_RELA)) + ? (getInfo().section ? getInfo().section->getIndex() : 0) + : getInfo().index; + + return shdr; +} + +ElfSegment::ElfSegment(Elf_Phdr* phdr) + : type(phdr->p_type), + v_p_diff(phdr->p_paddr - phdr->p_vaddr), + flags(phdr->p_flags), + align(phdr->p_align), + vaddr(phdr->p_vaddr), + filesz(phdr->p_filesz), + memsz(phdr->p_memsz) {} + +void ElfSegment::addSection(ElfSection* section) { + // Make sure all sections in PT_GNU_RELRO won't be moved by elfhack + assert(!((type == PT_GNU_RELRO) && (section->isRelocatable()))); + + // TODO: Check overlapping sections + std::list<ElfSection*>::iterator i; + for (i = sections.begin(); i != sections.end(); ++i) + if ((*i)->getAddr() > section->getAddr()) break; + sections.insert(i, section); + section->addToSegment(this); +} + +void ElfSegment::removeSection(ElfSection* section) { + sections.remove(section); + section->removeFromSegment(this); +} + +unsigned int ElfSegment::getFileSize() { + if (type == PT_GNU_RELRO) return filesz; + + if (sections.empty()) return 0; + // Search the last section that is not SHT_NOBITS + std::list<ElfSection*>::reverse_iterator i; + for (i = sections.rbegin(); + (i != sections.rend()) && ((*i)->getType() == SHT_NOBITS); ++i) + ; + // All sections are SHT_NOBITS + if (i == sections.rend()) return 0; + + unsigned int end = (*i)->getAddr() + (*i)->getSize(); + + return end - sections.front()->getAddr(); +} + +unsigned int ElfSegment::getMemSize() { + if (type == PT_GNU_RELRO) return memsz; + + if (sections.empty()) return 0; + + unsigned int end = sections.back()->getAddr() + sections.back()->getSize(); + + return end - sections.front()->getAddr(); +} + +unsigned int ElfSegment::getOffset() { + if ((type == PT_GNU_RELRO) && !sections.empty() && + (sections.front()->getAddr() != vaddr)) + throw std::runtime_error( + "PT_GNU_RELRO segment doesn't start on a section start"); + + return sections.empty() ? 0 : sections.front()->getOffset(); +} + +unsigned int ElfSegment::getAddr() { + if ((type == PT_GNU_RELRO) && !sections.empty() && + (sections.front()->getAddr() != vaddr)) + throw std::runtime_error( + "PT_GNU_RELRO segment doesn't start on a section start"); + + return sections.empty() ? 0 : sections.front()->getAddr(); +} + +void ElfSegment::clear() { + for (std::list<ElfSection*>::iterator i = sections.begin(); + i != sections.end(); ++i) + (*i)->removeFromSegment(this); + sections.clear(); +} + +ElfValue* ElfDynamic_Section::getValueForType(unsigned int tag) { + for (unsigned int i = 0; i < shdr.sh_size / shdr.sh_entsize; i++) + if (dyns[i].tag == tag) return dyns[i].value; + + return nullptr; +} + +ElfSection* ElfDynamic_Section::getSectionForType(unsigned int tag) { + ElfValue* value = getValueForType(tag); + return value ? value->getSection() : nullptr; +} + +bool ElfDynamic_Section::setValueForType(unsigned int tag, ElfValue* val) { + unsigned int i; + unsigned int shnum = shdr.sh_size / shdr.sh_entsize; + for (i = 0; (i < shnum) && (dyns[i].tag != DT_NULL); i++) + if (dyns[i].tag == tag) { + delete dyns[i].value; + dyns[i].value = val; + return true; + } + // If we get here, this means we didn't match for the given tag + // Most of the time, there are a few DT_NULL entries, that we can + // use to add our value, but if we are on the last entry, we can't. + if (i >= shnum - 1) return false; + + dyns[i].tag = tag; + dyns[i].value = val; + return true; +} + +ElfDynamic_Section::ElfDynamic_Section(Elf_Shdr& s, std::ifstream* file, + Elf* parent) + : ElfSection(s, file, parent) { + auto pos = file->tellg(); + dyns.resize(s.sh_size / s.sh_entsize); + file->seekg(shdr.sh_offset); + // Here we assume tags refer to only one section (e.g. DT_RELSZ accounts + // for .rel.dyn size) + for (unsigned int i = 0; i < s.sh_size / s.sh_entsize; i++) { + Elf_Dyn dyn(*file, parent->getClass(), parent->getData()); + dyns[i].tag = dyn.d_tag; + switch (dyn.d_tag) { + case DT_NULL: + case DT_SYMBOLIC: + case DT_TEXTREL: + case DT_BIND_NOW: + dyns[i].value = new ElfValue(); + break; + case DT_NEEDED: + case DT_SONAME: + case DT_RPATH: + case DT_PLTREL: + case DT_RUNPATH: + case DT_FLAGS: + case DT_RELACOUNT: + case DT_RELCOUNT: + case DT_VERDEFNUM: + case DT_VERNEEDNUM: + dyns[i].value = new ElfPlainValue(dyn.d_un.d_val); + break; + case DT_PLTGOT: + case DT_HASH: + case DT_STRTAB: + case DT_SYMTAB: + case DT_RELA: + case DT_INIT: + case DT_FINI: + case DT_REL: + case DT_JMPREL: + case DT_INIT_ARRAY: + case DT_FINI_ARRAY: + case DT_GNU_HASH: + case DT_VERSYM: + case DT_VERNEED: + case DT_VERDEF: + dyns[i].value = new ElfLocation(dyn.d_un.d_ptr, parent); + break; + default: + dyns[i].value = nullptr; + } + } + // Another loop to get the section sizes + for (unsigned int i = 0; i < s.sh_size / s.sh_entsize; i++) + switch (dyns[i].tag) { + case DT_PLTRELSZ: + dyns[i].value = new ElfSize(getSectionForType(DT_JMPREL)); + break; + case DT_RELASZ: + dyns[i].value = new ElfSize(getSectionForType(DT_RELA)); + break; + case DT_STRSZ: + dyns[i].value = new ElfSize(getSectionForType(DT_STRTAB)); + break; + case DT_RELSZ: + dyns[i].value = new ElfSize(getSectionForType(DT_REL)); + break; + case DT_INIT_ARRAYSZ: + dyns[i].value = new ElfSize(getSectionForType(DT_INIT_ARRAY)); + break; + case DT_FINI_ARRAYSZ: + dyns[i].value = new ElfSize(getSectionForType(DT_FINI_ARRAY)); + break; + case DT_RELAENT: + dyns[i].value = new ElfEntSize(getSectionForType(DT_RELA)); + break; + case DT_SYMENT: + dyns[i].value = new ElfEntSize(getSectionForType(DT_SYMTAB)); + break; + case DT_RELENT: + dyns[i].value = new ElfEntSize(getSectionForType(DT_REL)); + break; + } + + file->seekg(pos); +} + +ElfDynamic_Section::~ElfDynamic_Section() { + for (unsigned int i = 0; i < shdr.sh_size / shdr.sh_entsize; i++) + delete dyns[i].value; +} + +void ElfDynamic_Section::serialize(std::ofstream& file, unsigned char ei_class, + unsigned char ei_data) { + for (unsigned int i = 0; i < shdr.sh_size / shdr.sh_entsize; i++) { + Elf_Dyn dyn; + dyn.d_tag = dyns[i].tag; + dyn.d_un.d_val = (dyns[i].value != nullptr) ? dyns[i].value->getValue() : 0; + dyn.serialize(file, ei_class, ei_data); + } +} + +ElfSymtab_Section::ElfSymtab_Section(Elf_Shdr& s, std::ifstream* file, + Elf* parent) + : ElfSection(s, file, parent) { + auto pos = file->tellg(); + syms.resize(s.sh_size / s.sh_entsize); + ElfStrtab_Section* strtab = (ElfStrtab_Section*)getLink(); + file->seekg(shdr.sh_offset); + for (unsigned int i = 0; i < shdr.sh_size / shdr.sh_entsize; i++) { + Elf_Sym sym(*file, parent->getClass(), parent->getData()); + syms[i].name = strtab->getStr(sym.st_name); + syms[i].info = sym.st_info; + syms[i].other = sym.st_other; + ElfSection* section = + (sym.st_shndx == SHN_ABS) ? nullptr : parent->getSection(sym.st_shndx); + new (&syms[i].value) + ElfLocation(section, sym.st_value, ElfLocation::ABSOLUTE); + syms[i].size = sym.st_size; + syms[i].defined = (sym.st_shndx != SHN_UNDEF); + } + file->seekg(pos); +} + +void ElfSymtab_Section::serialize(std::ofstream& file, unsigned char ei_class, + unsigned char ei_data) { + ElfStrtab_Section* strtab = (ElfStrtab_Section*)getLink(); + for (unsigned int i = 0; i < shdr.sh_size / shdr.sh_entsize; i++) { + Elf_Sym sym; + sym.st_name = strtab->getStrIndex(syms[i].name); + sym.st_info = syms[i].info; + sym.st_other = syms[i].other; + sym.st_value = syms[i].value.getValue(); + ElfSection* section = syms[i].value.getSection(); + if (syms[i].defined) + sym.st_shndx = section ? section->getIndex() : SHN_ABS; + else + sym.st_shndx = SHN_UNDEF; + sym.st_size = syms[i].size; + sym.serialize(file, ei_class, ei_data); + } +} + +Elf_SymValue* ElfSymtab_Section::lookup(const char* name, + unsigned int type_filter) { + for (std::vector<Elf_SymValue>::iterator sym = syms.begin(); + sym != syms.end(); sym++) { + if ((type_filter & (1 << ELF32_ST_TYPE(sym->info))) && + (strcmp(sym->name, name) == 0)) { + return &*sym; + } + } + return nullptr; +} + +const char* ElfStrtab_Section::getStr(unsigned int index) { + for (std::vector<table_storage>::iterator t = table.begin(); t != table.end(); + t++) { + if (index < t->used) return t->buf + index; + index -= t->used; + } + assert(1 == 0); + return nullptr; +} + +const char* ElfStrtab_Section::getStr(const char* string) { + if (string == nullptr) return nullptr; + + // If the given string is within the section, return it + for (std::vector<table_storage>::iterator t = table.begin(); t != table.end(); + t++) + if ((string >= t->buf) && (string < t->buf + t->used)) return string; + + // TODO: should scan in the section to find an existing string + + // If not, we need to allocate the string in the section + size_t len = strlen(string) + 1; + + if (table.back().size - table.back().used < len) + table.resize(table.size() + 1); + + char* alloc_str = table.back().buf + table.back().used; + memcpy(alloc_str, string, len); + table.back().used += len; + + shdr.sh_size += len; + markDirty(); + + return alloc_str; +} + +unsigned int ElfStrtab_Section::getStrIndex(const char* string) { + if (string == nullptr) return 0; + + unsigned int index = 0; + string = getStr(string); + for (std::vector<table_storage>::iterator t = table.begin(); t != table.end(); + t++) { + if ((string >= t->buf) && (string < t->buf + t->used)) + return index + (string - t->buf); + index += t->used; + } + + assert(1 == 0); + return 0; +} + +void ElfStrtab_Section::serialize(std::ofstream& file, unsigned char ei_class, + unsigned char ei_data) { + file.seekp(getOffset()); + for (std::vector<table_storage>::iterator t = table.begin(); t != table.end(); + t++) + file.write(t->buf, t->used); +} |