Source code
Revision control
Copy as Markdown
Other Tools
/* 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
#include <stdexcept>
#include <list>
#include <vector>
#include <cstring>
#include <fstream>
#include <algorithm>
#include <elf.h>
#include <asm/byteorder.h>
// Technically, __*_to_cpu and __cpu_to* function are equivalent,
// so swap can use either of both.
#define def_swap(endian, type, bits) \
static inline type##bits##_t swap(type##bits##_t i) { \
return __##endian##bits##_to_cpu(i); \
}
class little_endian {
public:
def_swap(le, uint, 16);
def_swap(le, uint, 32);
def_swap(le, uint, 64);
def_swap(le, int, 16);
def_swap(le, int, 32);
def_swap(le, int, 64);
};
class big_endian {
public:
def_swap(be, uint, 16);
def_swap(be, uint, 32);
def_swap(be, uint, 64);
def_swap(be, int, 16);
def_swap(be, int, 32);
def_swap(be, int, 64);
};
// forward declaration
class ElfSection;
class ElfSegment;
// TODO: Rename Elf_* types
class Elf_Ehdr;
class Elf_Phdr;
class Elf;
class ElfDynamic_Section;
class ElfStrtab_Section;
template <typename X>
class FixedSizeData {
public:
struct Wrapper {
X value;
};
typedef Wrapper Type32;
typedef Wrapper Type64;
template <class endian, typename R, typename T>
static void swap(T& t, R& r) {
r.value = endian::swap(t.value);
}
};
class Elf_Ehdr_Traits {
public:
typedef Elf32_Ehdr Type32;
typedef Elf64_Ehdr Type64;
template <class endian, typename R, typename T>
static void swap(T& t, R& r);
};
class Elf_Phdr_Traits {
public:
typedef Elf32_Phdr Type32;
typedef Elf64_Phdr Type64;
template <class endian, typename R, typename T>
static void swap(T& t, R& r);
};
class Elf_Shdr_Traits {
public:
typedef Elf32_Shdr Type32;
typedef Elf64_Shdr Type64;
template <class endian, typename R, typename T>
static void swap(T& t, R& r);
};
class Elf_Dyn_Traits {
public:
typedef Elf32_Dyn Type32;
typedef Elf64_Dyn Type64;
template <class endian, typename R, typename T>
static void swap(T& t, R& r);
};
class Elf_Sym_Traits {
public:
typedef Elf32_Sym Type32;
typedef Elf64_Sym Type64;
template <class endian, typename R, typename T>
static void swap(T& t, R& r);
};
class Elf_Rel_Traits {
public:
typedef Elf32_Rel Type32;
typedef Elf64_Rel Type64;
template <class endian, typename R, typename T>
static void swap(T& t, R& r);
};
class Elf_Rela_Traits {
public:
typedef Elf32_Rela Type32;
typedef Elf64_Rela Type64;
template <class endian, typename R, typename T>
static void swap(T& t, R& r);
};
class ElfValue {
public:
virtual unsigned int getValue() { return 0; }
virtual ElfSection* getSection() { return nullptr; }
};
class ElfPlainValue : public ElfValue {
unsigned int value;
public:
ElfPlainValue(unsigned int val) : value(val) {};
unsigned int getValue() { return value; }
};
class ElfLocation : public ElfValue {
ElfSection* section;
unsigned int offset;
public:
enum position { ABSOLUTE, RELATIVE };
ElfLocation() : section(nullptr), offset(0) {};
ElfLocation(ElfSection* section, unsigned int off,
enum position pos = RELATIVE);
ElfLocation(unsigned int location, Elf* elf);
unsigned int getValue();
ElfSection* getSection() { return section; }
const char* getBuffer();
};
class ElfSize : public ElfValue {
ElfSection* section;
public:
ElfSize(ElfSection* s) : section(s) {};
unsigned int getValue();
ElfSection* getSection() { return section; }
};
class ElfEntSize : public ElfValue {
ElfSection* section;
public:
ElfEntSize(ElfSection* s) : section(s) {};
unsigned int getValue();
ElfSection* getSection() { return section; }
};
template <typename T>
class serializable : public T::Type64 {
public:
serializable() {};
serializable(const typename T::Type64& p) : T::Type64(p) {};
private:
template <typename R>
void init(const char* buf, size_t len, unsigned char ei_data) {
R e;
assert(len >= sizeof(e));
memcpy(&e, buf, sizeof(e));
if (ei_data == ELFDATA2LSB) {
T::template swap<little_endian>(e, *this);
return;
} else if (ei_data == ELFDATA2MSB) {
T::template swap<big_endian>(e, *this);
return;
}
throw std::runtime_error("Unsupported ELF data encoding");
}
template <typename R>
void serialize(const char* buf, size_t len, unsigned char ei_data) {
assert(len >= sizeof(R));
if (ei_data == ELFDATA2LSB) {
T::template swap<little_endian>(*this, *(R*)buf);
return;
} else if (ei_data == ELFDATA2MSB) {
T::template swap<big_endian>(*this, *(R*)buf);
return;
}
throw std::runtime_error("Unsupported ELF data encoding");
}
public:
serializable(const char* buf, size_t len, unsigned char ei_class,
unsigned char ei_data) {
if (ei_class == ELFCLASS32) {
init<typename T::Type32>(buf, len, ei_data);
return;
} else if (ei_class == ELFCLASS64) {
init<typename T::Type64>(buf, len, ei_data);
return;
}
throw std::runtime_error("Unsupported ELF class");
}
serializable(std::ifstream& file, unsigned char ei_class,
unsigned char ei_data) {
if (ei_class == ELFCLASS32) {
typename T::Type32 e;
file.read((char*)&e, sizeof(e));
init<typename T::Type32>((char*)&e, sizeof(e), ei_data);
return;
} else if (ei_class == ELFCLASS64) {
typename T::Type64 e;
file.read((char*)&e, sizeof(e));
init<typename T::Type64>((char*)&e, sizeof(e), ei_data);
return;
}
throw std::runtime_error("Unsupported ELF class or data encoding");
}
void serialize(std::ofstream& file, unsigned char ei_class,
unsigned char ei_data) {
if (ei_class == ELFCLASS32) {
typename T::Type32 e;
serialize<typename T::Type32>((char*)&e, sizeof(e), ei_data);
file.write((char*)&e, sizeof(e));
return;
} else if (ei_class == ELFCLASS64) {
typename T::Type64 e;
serialize<typename T::Type64>((char*)&e, sizeof(e), ei_data);
file.write((char*)&e, sizeof(e));
return;
}
throw std::runtime_error("Unsupported ELF class or data encoding");
}
void serialize(char* buf, size_t len, unsigned char ei_class,
unsigned char ei_data) {
if (ei_class == ELFCLASS32) {
serialize<typename T::Type32>(buf, len, ei_data);
return;
} else if (ei_class == ELFCLASS64) {
serialize<typename T::Type64>(buf, len, ei_data);
return;
}
throw std::runtime_error("Unsupported ELF class");
}
static inline unsigned int size(unsigned char ei_class) {
if (ei_class == ELFCLASS32)
return sizeof(typename T::Type32);
else if (ei_class == ELFCLASS64)
return sizeof(typename T::Type64);
return 0;
}
};
typedef serializable<Elf_Shdr_Traits> Elf_Shdr;
class Elf {
public:
Elf(std::ifstream& file);
~Elf();
/* index == -1 is treated as index == ehdr.e_shstrndx */
ElfSection* getSection(int index);
ElfSection* getSectionAt(Elf64_Off offset);
ElfSegment* getSegmentByType(unsigned int type, ElfSegment* last = nullptr);
ElfDynamic_Section* getDynSection();
void normalize();
void write(std::ofstream& file);
unsigned char getClass();
unsigned char getData();
unsigned char getType();
unsigned char getMachine();
unsigned int getSize();
void insertSegmentAfter(ElfSegment* previous, ElfSegment* segment) {
std::vector<ElfSegment*>::iterator prev =
std::find(segments.begin(), segments.end(), previous);
segments.insert(prev + 1, segment);
}
void removeSegment(ElfSegment* segment);
private:
Elf_Ehdr* ehdr;
ElfLocation eh_entry;
ElfStrtab_Section* eh_shstrndx;
ElfSection** sections;
std::vector<ElfSegment*> segments;
ElfSection *shdr_section, *phdr_section;
/* Values used only during initialization */
Elf_Shdr** tmp_shdr;
std::ifstream* tmp_file;
};
class ElfSection {
public:
typedef union {
ElfSection* section;
int index;
} SectionInfo;
ElfSection(Elf_Shdr& s, std::ifstream* file, Elf* parent);
virtual ~ElfSection() { free(data); }
const char* getName() { return name; }
unsigned int getType() { return shdr.sh_type; }
unsigned int getFlags() { return shdr.sh_flags; }
Elf64_Addr getAddr();
Elf64_Off getSize() { return shdr.sh_size; }
unsigned int getAddrAlign() { return shdr.sh_addralign; }
unsigned int getEntSize() { return shdr.sh_entsize; }
const char* getData() { return data; }
ElfSection* getLink() { return link; }
SectionInfo getInfo() { return info; }
void shrink(unsigned int newsize) {
if (newsize < shdr.sh_size) {
shdr.sh_size = newsize;
markDirty();
}
}
void grow(unsigned int newsize) {
if (newsize > shdr.sh_size) {
data = static_cast<char*>(realloc(data, newsize));
memset(data + shdr.sh_size, 0, newsize - shdr.sh_size);
shdr.sh_size = newsize;
markDirty();
}
}
Elf64_Off getOffset();
int getIndex();
Elf_Shdr& getShdr();
ElfSection* getNext() { return next; }
ElfSection* getPrevious() { return previous; }
virtual bool isRelocatable() {
return ((getType() == SHT_SYMTAB) || (getType() == SHT_STRTAB) ||
(getType() == SHT_RELA) || (getType() == SHT_HASH) ||
(getType() == SHT_NOTE) || (getType() == SHT_REL) ||
(getType() == SHT_DYNSYM) || (getType() == SHT_GNU_HASH) ||
(getType() == SHT_GNU_verdef) || (getType() == SHT_GNU_verneed) ||
(getType() == SHT_GNU_versym) || getSegmentByType(PT_INTERP)) &&
(getFlags() & SHF_ALLOC);
}
void insertAfter(ElfSection* section, bool dirty = true) {
if (previous != nullptr) previous->next = next;
if (next != nullptr) next->previous = previous;
previous = section;
if (section != nullptr) {
next = section->next;
section->next = this;
} else
next = nullptr;
if (next != nullptr) next->previous = this;
if (dirty) markDirty();
insertInSegments(section->segments);
}
virtual void insertBefore(ElfSection* section, bool dirty = true) {
if (previous != nullptr) previous->next = next;
if (next != nullptr) next->previous = previous;
next = section;
if (section != nullptr) {
previous = section->previous;
section->previous = this;
} else
previous = nullptr;
if (previous != nullptr) previous->next = this;
if (dirty) markDirty();
insertInSegments(section->segments);
}
void markDirty() {
if (link != nullptr) shdr.sh_link = -1;
if (info.index) shdr.sh_info = -1;
shdr.sh_offset = -1;
if (isRelocatable()) shdr.sh_addr = -1;
if (next) next->markDirty();
}
virtual void serialize(std::ofstream& file, unsigned char ei_class,
unsigned char ei_data) {
if (getType() == SHT_NOBITS) return;
file.seekp(getOffset());
file.write(data, getSize());
}
ElfSegment* getSegmentByType(unsigned int type);
private:
friend class ElfSegment;
void addToSegment(ElfSegment* segment) { segments.push_back(segment); }
void removeFromSegment(ElfSegment* segment) {
std::vector<ElfSegment*>::iterator i =
std::find(segments.begin(), segments.end(), segment);
segments.erase(i, i + 1);
}
void insertInSegments(std::vector<ElfSegment*>& segs);
protected:
Elf_Shdr shdr;
char* data;
const char* name;
private:
ElfSection* link;
SectionInfo info;
ElfSection *next, *previous;
int index;
std::vector<ElfSegment*> segments;
};
class ElfSegment {
public:
ElfSegment(Elf_Phdr* phdr);
unsigned int getType() { return type; }
unsigned int getFlags() { return flags; }
unsigned int getAlign() { return align; }
ElfSection* getFirstSection() {
return sections.empty() ? nullptr : sections.front();
}
int getVPDiff() { return v_p_diff; }
unsigned int getFileSize();
unsigned int getMemSize();
unsigned int getOffset();
unsigned int getAddr();
void addSection(ElfSection* section);
void removeSection(ElfSection* section);
std::list<ElfSection*>::iterator begin() { return sections.begin(); }
std::list<ElfSection*>::iterator end() { return sections.end(); }
void clear();
private:
unsigned int type;
int v_p_diff; // Difference between physical and virtual address
unsigned int flags;
unsigned int align;
std::list<ElfSection*> sections;
// The following are only really used for PT_GNU_RELRO until something
// better is found.
unsigned int vaddr;
unsigned int filesz, memsz;
};
class Elf_Ehdr : public serializable<Elf_Ehdr_Traits>, public ElfSection {
public:
Elf_Ehdr(std::ifstream& file, unsigned char ei_class, unsigned char ei_data);
void serialize(std::ofstream& file, unsigned char ei_class,
unsigned char ei_data) {
serializable<Elf_Ehdr_Traits>::serialize(file, ei_class, ei_data);
}
};
class Elf_Phdr : public serializable<Elf_Phdr_Traits> {
public:
Elf_Phdr() {};
Elf_Phdr(std::ifstream& file, unsigned char ei_class, unsigned char ei_data)
: serializable<Elf_Phdr_Traits>(file, ei_class, ei_data) {};
bool contains(ElfSection* section) {
unsigned int size = section->getSize();
unsigned int addr = section->getAddr();
// This may be biased, but should work in most cases
if ((section->getFlags() & SHF_ALLOC) == 0) return false;
// Special case for PT_DYNAMIC. Eventually, this should
// be better handled than special cases
if ((p_type == PT_DYNAMIC) && (section->getType() != SHT_DYNAMIC))
return false;
// Special case for PT_TLS.
if ((p_type == PT_TLS) && !(section->getFlags() & SHF_TLS)) return false;
return (addr >= p_vaddr) && (addr + size <= p_vaddr + p_memsz);
}
};
typedef serializable<Elf_Dyn_Traits> Elf_Dyn;
struct Elf_DynValue {
unsigned int tag;
ElfValue* value;
};
class ElfDynamic_Section : public ElfSection {
public:
ElfDynamic_Section(Elf_Shdr& s, std::ifstream* file, Elf* parent);
~ElfDynamic_Section();
void serialize(std::ofstream& file, unsigned char ei_class,
unsigned char ei_data);
ElfValue* getValueForType(unsigned int tag);
ElfSection* getSectionForType(unsigned int tag);
bool setValueForType(unsigned int tag, ElfValue* val);
private:
std::vector<Elf_DynValue> dyns;
};
typedef serializable<Elf_Sym_Traits> Elf_Sym;
struct Elf_SymValue {
const char* name;
unsigned char info;
unsigned char other;
ElfLocation value;
unsigned int size;
bool defined;
};
#define STT(type) (1 << STT_##type)
class ElfSymtab_Section : public ElfSection {
public:
ElfSymtab_Section(Elf_Shdr& s, std::ifstream* file, Elf* parent);
void serialize(std::ofstream& file, unsigned char ei_class,
unsigned char ei_data);
Elf_SymValue* lookup(const char* name,
unsigned int type_filter = STT(OBJECT) | STT(FUNC));
// private: // Until we have a real API
std::vector<Elf_SymValue> syms;
};
class Elf_Rel : public serializable<Elf_Rel_Traits> {
public:
Elf_Rel() : serializable<Elf_Rel_Traits>() {};
Elf_Rel(std::ifstream& file, unsigned char ei_class, unsigned char ei_data)
: serializable<Elf_Rel_Traits>(file, ei_class, ei_data) {};
static const unsigned int sh_type = SHT_REL;
static const unsigned int d_tag = DT_REL;
static const unsigned int d_tag_count = DT_RELCOUNT;
};
class Elf_Rela : public serializable<Elf_Rela_Traits> {
public:
Elf_Rela() : serializable<Elf_Rela_Traits>() {};
Elf_Rela(std::ifstream& file, unsigned char ei_class, unsigned char ei_data)
: serializable<Elf_Rela_Traits>(file, ei_class, ei_data) {};
static const unsigned int sh_type = SHT_RELA;
static const unsigned int d_tag = DT_RELA;
static const unsigned int d_tag_count = DT_RELACOUNT;
};
template <class Rel>
class ElfRel_Section : public ElfSection {
public:
ElfRel_Section(Elf_Shdr& s, std::ifstream* file, Elf* parent)
: ElfSection(s, file, parent) {
auto pos = file->tellg();
file->seekg(shdr.sh_offset);
for (unsigned int i = 0; i < s.sh_size / s.sh_entsize; i++) {
Rel r(*file, parent->getClass(), parent->getData());
rels.push_back(r);
}
file->seekg(pos);
}
void serialize(std::ofstream& file, unsigned char ei_class,
unsigned char ei_data) {
for (typename std::vector<Rel>::iterator i = rels.begin(); i != rels.end();
++i)
(*i).serialize(file, ei_class, ei_data);
}
// private: // Until we have a real API
std::vector<Rel> rels;
};
class ElfStrtab_Section : public ElfSection {
public:
ElfStrtab_Section(Elf_Shdr& s, std::ifstream* file, Elf* parent)
: ElfSection(s, file, parent) {
table.push_back(table_storage(data, shdr.sh_size));
}
~ElfStrtab_Section() {
for (std::vector<table_storage>::iterator t = table.begin() + 1;
t != table.end(); ++t)
delete[] t->buf;
}
const char* getStr(unsigned int index);
const char* getStr(const char* string);
unsigned int getStrIndex(const char* string);
void serialize(std::ofstream& file, unsigned char ei_class,
unsigned char ei_data);
private:
struct table_storage {
unsigned int size, used;
char* buf;
table_storage() : size(4096), used(0), buf(new char[4096]) {}
table_storage(const char* data, unsigned int sz)
: size(sz), used(sz), buf(const_cast<char*>(data)) {}
};
std::vector<table_storage> table;
};
inline unsigned char Elf::getClass() { return ehdr->e_ident[EI_CLASS]; }
inline unsigned char Elf::getData() { return ehdr->e_ident[EI_DATA]; }
inline unsigned char Elf::getType() { return ehdr->e_type; }
inline unsigned char Elf::getMachine() { return ehdr->e_machine; }
inline unsigned int Elf::getSize() {
ElfSection* section;
for (section = shdr_section /* It's usually not far from the end */;
section->getNext() != nullptr; section = section->getNext());
return section->getOffset() + section->getSize();
}
inline ElfSegment* ElfSection::getSegmentByType(unsigned int type) {
for (std::vector<ElfSegment*>::iterator seg = segments.begin();
seg != segments.end(); ++seg)
if ((*seg)->getType() == type) return *seg;
return nullptr;
}
inline void ElfSection::insertInSegments(std::vector<ElfSegment*>& segs) {
for (std::vector<ElfSegment*>::iterator it = segs.begin(); it != segs.end();
++it) {
(*it)->addSection(this);
}
}
inline ElfLocation::ElfLocation(ElfSection* section, unsigned int off,
enum position pos)
: section(section) {
if ((pos == ABSOLUTE) && section)
offset = off - section->getAddr();
else
offset = off;
}
inline ElfLocation::ElfLocation(unsigned int location, Elf* elf) {
section = elf->getSectionAt(location);
offset = location - (section ? section->getAddr() : 0);
}
inline unsigned int ElfLocation::getValue() {
return (section ? section->getAddr() : 0) + offset;
}
inline const char* ElfLocation::getBuffer() {
return section ? section->getData() + offset : nullptr;
}
inline unsigned int ElfSize::getValue() { return section->getSize(); }
inline unsigned int ElfEntSize::getValue() { return section->getEntSize(); }