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fune/build/unix/elfhack/elf.cpp
Mike Hommey b54839958c Bug 1378986 - Adjust the fake phdr section properly. r=froydnj 
The PT_PHDR segment is optional, but the Android toolchain decides to
create one in some cases, and places it first. When that happens, the
work around for bug 1233963 fails, because the fake phdr section has not
been adjusted yet (it only happens when we see a PT_LOAD).

So we adjust the fake phdr section when we see a PT_PHDR segment (and
avoid re-updating it when we see a subsequent PT_LOAD).

--HG--
extra : rebase_source : 2190ec2f20ba9d144b8828874f9f8d70dd5ad2f6
2017-07-07 18:29:06 +09:00

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/* 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 Elf32_Shdr null32_section =
{ 0, SHT_NULL, 0, 0, 0, 0, SHN_UNDEF, 0, 0, 0 };
Elf_Shdr null_section(null32_section);
Elf_Ehdr::Elf_Ehdr(std::ifstream &file, char ei_class, 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
char e_ident[EI_VERSION];
file.seekg(0);
file.read(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++) {
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(unsigned int 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");
}
}
}
// 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();
}
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 = new char[shdr.sh_size];
int 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;
}
unsigned int ElfSection::getAddr()
{
if (shdr.sh_addr != (Elf32_Word)-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;
}
unsigned int ElfSection::getOffset()
{
if (shdr.sh_offset != (Elf32_Word)-1)
return shdr.sh_offset;
if (previous == nullptr)
return (shdr.sh_offset = 0);
unsigned int 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;
// Two subsequent sections can't be mapped in the same page in memory
// if they aren't in the same 4K block on disk.
if ((getType() != SHT_NOBITS) && getAddr()) {
if (((offset >> 12) != (previous->getOffset() >> 12)) &&
((getAddr() >> 12) == (previous->getAddr() >> 12)))
throw std::runtime_error("Moving section would require overlapping segments");
}
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 == (Elf32_Word)-1)
shdr.sh_link = getLink() ? getLink()->getIndex() : 0;
if (shdr.sh_info == (Elf32_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 || isElfHackFillerSegment())
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 || isElfHackFillerSegment())
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");
// Neither bionic nor glibc linkers seem to like when the offset of that segment is 0
if (isElfHackFillerSegment())
return vaddr;
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");
if (isElfHackFillerSegment())
return vaddr;
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)
{
int 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, char ei_class, 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)
{
int 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, char ei_class, 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, char ei_class, 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);
}
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