void serialize(std::ofstream &file, char ei_class, char ei_data)
{
// Readjust code offsets
for (std::vector<ElfSection *>::iterator c = code.begin(); c != code.end(); c++)
(*c)->getShdr().sh_addr += getAddr();
// Apply relocations
for (ElfSection *rel = elf->getSection(1); rel != NULL; rel = rel->getNext())
if ((rel->getType() == SHT_REL) || (rel->getType() == SHT_RELA)) {
ElfSection *section = rel->getInfo().section;
if ((section->getType() == SHT_PROGBITS) && (section->getFlags() & SHF_EXECINSTR)) {
if (rel->getType() == SHT_REL)
apply_relocations((ElfRel_Section<Elf_Rel> *)rel, section);
else
apply_relocations((ElfRel_Section<Elf_Rela> *)rel, section);
}
}
ElfSection::serialize(file, ei_class, ei_data);
}
ElfRelHackCode_Section(Elf_Shdr &s, Elf &e)
: ElfSection(s, NULL, NULL), parent(e) {
std::string file(rundir);
init = parent.getDynSection()->getSectionForType(DT_INIT);
file += "/inject/";
switch (parent.getMachine()) {
case EM_386:
file += "x86";
break;
case EM_X86_64:
file += "x86_64";
break;
case EM_ARM:
file += "arm";
break;
default:
throw std::runtime_error("unsupported architecture");
}
if (init == NULL)
file += "-noinit";
file += ".o";
std::ifstream inject(file.c_str(), std::ios::in|std::ios::binary);
elf = new Elf(inject);
if (elf->getType() != ET_REL)
throw std::runtime_error("object for injected code is not ET_REL");
if (elf->getMachine() != parent.getMachine())
throw std::runtime_error("architecture of object for injected code doesn't match");
ElfSymtab_Section *symtab = NULL;
// Get all executable sections from the injected code object.
// Most of the time, there will only be one for the init function,
// but on e.g. x86, there is a separate section for
// __i686.get_pc_thunk.$reg
// Find the symbol table at the same time.
for (ElfSection *section = elf->getSection(1); section != NULL;
section = section->getNext()) {
if ((section->getType() == SHT_PROGBITS) &&
(section->getFlags() & SHF_EXECINSTR)) {
code.push_back(section);
// We need to align this section depending on the greater
// alignment required by code sections.
if (shdr.sh_addralign < section->getAddrAlign())
shdr.sh_addralign = section->getAddrAlign();
} else if (section->getType() == SHT_SYMTAB) {
symtab = (ElfSymtab_Section *) section;
}
}
assert(code.size() != 0);
if (symtab == NULL)
throw std::runtime_error("Couldn't find a symbol table for the injected code");
// Find the init symbol
entry_point = -1;
int shndx = 0;
for (std::vector<Elf_SymValue>::iterator sym = symtab->syms.begin();
sym != symtab->syms.end(); sym++) {
if (strcmp(sym->name, "init") == 0) {
entry_point = sym->value.getValue();
shndx = sym->value.getSection()->getIndex();
break;
}
}
if (entry_point == -1)
throw std::runtime_error("Couldn't find an 'init' symbol in the injected code");
// Adjust code sections offsets according to their size
std::vector<ElfSection *>::iterator c = code.begin();
(*c)->getShdr().sh_addr = 0;
for(ElfSection *last = *(c++); c != code.end(); c++) {
unsigned int addr = last->getShdr().sh_addr + last->getSize();
if (addr & ((*c)->getAddrAlign() - 1))
addr = (addr | ((*c)->getAddrAlign() - 1)) + 1;
(*c)->getShdr().sh_addr = addr;
}
shdr.sh_size = code.back()->getAddr() + code.back()->getSize();
data = new char[shdr.sh_size];
char *buf = data;
for (c = code.begin(); c != code.end(); c++) {
memcpy(buf, (*c)->getData(), (*c)->getSize());
buf += (*c)->getSize();
if ((*c)->getIndex() < shndx)
entry_point += (*c)->getSize();
}
name = elfhack_text;
}
