/** Parses an ELF Section Table and constructs and parses all sections reachable from the table. The section is extended as
* necessary based on the number of entries and the size of each entry. */
SgAsmElfSectionTable *
SgAsmElfSectionTable::parse()
{
SgAsmGenericSection::parse();
SgAsmElfFileHeader *fhdr = dynamic_cast<SgAsmElfFileHeader*>(get_header());
ROSE_ASSERT(fhdr!=NULL);
ByteOrder::Endianness sex = fhdr->get_sex();
size_t ent_size, struct_size, opt_size, nentries;
calculate_sizes(&ent_size, &struct_size, &opt_size, &nentries);
ROSE_ASSERT(opt_size==fhdr->get_shextrasz() && nentries==fhdr->get_e_shnum());
/* If the current size is very small (0 or 1 byte) then we're coming straight from the constructor and the parsing should
* also extend this section to hold all the entries. Otherwise the caller must have assigned a specific size for a good
* reason and we should leave that alone, reading zeros if the entries extend beyond the defined size. */
if (get_size()<=1 && get_size()<nentries*ent_size)
extend(nentries*ent_size - get_size());
// Read all the section headers. Section headers are not essential to the Unix loader, which uses only segments. Therefore
// we should be prepared to handle bad entries.
std::vector<SgAsmElfSectionTableEntry*> entries;
rose_addr_t offset = 0;
try {
for (size_t i=0; i<nentries; i++, offset+=ent_size) {
SgAsmElfSectionTableEntry *shdr = NULL;
if (4 == fhdr->get_word_size()) {
SgAsmElfSectionTableEntry::Elf32SectionTableEntry_disk disk;
read_content_local(offset, &disk, struct_size);
shdr = new SgAsmElfSectionTableEntry(sex, &disk);
} else {
SgAsmElfSectionTableEntry::Elf64SectionTableEntry_disk disk;
read_content_local(offset, &disk, struct_size);
shdr = new SgAsmElfSectionTableEntry(sex, &disk);
}
if (opt_size>0)
shdr->get_extra() = read_content_local_ucl(offset+struct_size, opt_size);
entries.push_back(shdr);
}
} catch (const ShortRead &error) {
mlog[ERROR] <<"short read for elf section header #" <<entries.size()
<<" at file offset " <<StringUtility::addrToString(error.offset)
<<" when reading " <<StringUtility::plural(error.size, "bytes") <<"\n";
mlog[ERROR] <<"expected " <<StringUtility::plural(nentries, "sections") <<", but bailing out early\n";
nentries = entries.size();
}
/* This vector keeps track of which sections have already been parsed. We could get the same information by calling
* fhdr->get_section_by_id() and passing the entry number since entry numbers and IDs are one and the same in ELF. However,
* this is a bit easier. */
std::vector<SgAsmElfSection*> is_parsed;
is_parsed.resize(entries.size(), NULL);
/* All sections implicitly depend on the section string table for their names. */
SgAsmElfStringSection *section_name_strings=NULL;
if (fhdr->get_e_shstrndx() > 0 && fhdr->get_e_shstrndx() < entries.size()) {
SgAsmElfSectionTableEntry *entry = entries[fhdr->get_e_shstrndx()];
ASSERT_not_null(entry);
section_name_strings = new SgAsmElfStringSection(fhdr);
section_name_strings->init_from_section_table(entry, section_name_strings, fhdr->get_e_shstrndx());
section_name_strings->parse();
is_parsed[fhdr->get_e_shstrndx()] = section_name_strings;
}
/* Read all the sections. Some sections depend on other sections, so we read them in such an order that all dependencies
* are satisfied first. */
while (1) {
bool try_again=false;
for (size_t i=0; i<entries.size(); i++) {
SgAsmElfSectionTableEntry *entry = entries[i];
ROSE_ASSERT(entry->get_sh_link()<entries.size());
/* Some sections might reference another section through the sh_link member. */
bool need_linked = entry->get_sh_link() > 0;
ROSE_ASSERT(!need_linked || entry->get_sh_link()<entries.size());
SgAsmElfSection *linked = need_linked ? is_parsed[entry->get_sh_link()] : NULL;
/* Relocation sections might have a second linked section stored in sh_info. */
bool need_info_linked = (entry->get_sh_type() == SgAsmElfSectionTableEntry::SHT_REL ||
entry->get_sh_type() == SgAsmElfSectionTableEntry::SHT_RELA) &&
entry->get_sh_info() > 0;
ROSE_ASSERT(!need_info_linked || entry->get_sh_info()<entries.size());
SgAsmElfSection *info_linked = need_info_linked ? is_parsed[entry->get_sh_info()] : NULL;
if (is_parsed[i]) {
/* This section has already been parsed. */
} else if ((need_linked && !linked) || (need_info_linked && !info_linked)) {
/* Don't parse this section yet because it depends on something that's not parsed yet. */
try_again = true;
} else {
switch (entry->get_sh_type()) {
case SgAsmElfSectionTableEntry::SHT_NULL:
/* Null entry. We still create the section just to hold the section header. */
is_parsed[i] = new SgAsmElfSection(fhdr);
break;
case SgAsmElfSectionTableEntry::SHT_NOBITS:
/* These types of sections don't occupy any file space (e.g., BSS) */
is_parsed[i] = new SgAsmElfSection(fhdr);
break;
case SgAsmElfSectionTableEntry::SHT_DYNAMIC: {
SgAsmElfStringSection *strsec = dynamic_cast<SgAsmElfStringSection*>(linked);
ROSE_ASSERT(strsec);
is_parsed[i] = new SgAsmElfDynamicSection(fhdr, strsec);
break;
}
case SgAsmElfSectionTableEntry::SHT_DYNSYM: {
SgAsmElfStringSection *strsec = dynamic_cast<SgAsmElfStringSection*>(linked);
ROSE_ASSERT(strsec);
SgAsmElfSymbolSection *symsec = new SgAsmElfSymbolSection(fhdr, strsec);
symsec->set_is_dynamic(true);
is_parsed[i] = symsec;
break;
}
case SgAsmElfSectionTableEntry::SHT_SYMTAB: {
SgAsmElfStringSection *strsec = dynamic_cast<SgAsmElfStringSection*>(linked);
ROSE_ASSERT(strsec);
SgAsmElfSymbolSection *symsec = new SgAsmElfSymbolSection(fhdr, strsec);
symsec->set_is_dynamic(false);
is_parsed[i] = symsec;
break;
}
case SgAsmElfSectionTableEntry::SHT_STRTAB:
is_parsed[i] = new SgAsmElfStringSection(fhdr);
break;
case SgAsmElfSectionTableEntry::SHT_REL: {
SgAsmElfSymbolSection *symbols = dynamic_cast<SgAsmElfSymbolSection*>(linked);
SgAsmElfRelocSection *relocsec = new SgAsmElfRelocSection(fhdr, symbols, info_linked);
relocsec->set_uses_addend(false);
is_parsed[i] = relocsec;
break;
}
case SgAsmElfSectionTableEntry::SHT_RELA: {
SgAsmElfSymbolSection *symbols = dynamic_cast<SgAsmElfSymbolSection*>(linked);
SgAsmElfRelocSection *relocsec = new SgAsmElfRelocSection(fhdr, symbols, info_linked);
relocsec->set_uses_addend(true);
is_parsed[i] = relocsec;
break;
}
case SgAsmElfSectionTableEntry::SHT_PROGBITS: {
if (!section_name_strings) {
fprintf(stderr, "SgAsmElfSectionTable::parse(): no string table for section table\n");
is_parsed[i] = new SgAsmElfSection(fhdr);
} else {
std::string section_name = section_name_strings->read_content_local_str(entry->get_sh_name());
if (section_name == ".eh_frame") {
is_parsed[i] = new SgAsmElfEHFrameSection(fhdr);
} else {
is_parsed[i] = new SgAsmElfSection(fhdr);
}
}
break;
}
case SgAsmElfSectionTableEntry::SHT_GNU_versym: {
is_parsed[i] = new SgAsmElfSymverSection(fhdr);
break;
}
case SgAsmElfSectionTableEntry::SHT_GNU_verdef: {
SgAsmElfStringSection *strsec = dynamic_cast<SgAsmElfStringSection*>(linked);
ROSE_ASSERT(strsec);
is_parsed[i] = new SgAsmElfSymverDefinedSection(fhdr,strsec);
break;
}
case SgAsmElfSectionTableEntry::SHT_GNU_verneed: {
SgAsmElfStringSection *strsec = dynamic_cast<SgAsmElfStringSection*>(linked);
ROSE_ASSERT(strsec);
is_parsed[i] = new SgAsmElfSymverNeededSection(fhdr,strsec);
break;
}
default:
is_parsed[i] = new SgAsmElfSection(fhdr);
break;
}
is_parsed[i]->init_from_section_table(entry, section_name_strings, i);
is_parsed[i]->parse();
}
}
if (!try_again)
break;
}
/* Initialize links between sections */
for (size_t i = 0; i < entries.size(); i++) {
SgAsmElfSectionTableEntry *shdr = entries[i];
if (shdr->get_sh_link() > 0) {
SgAsmElfSection *source = isSgAsmElfSection(fhdr->get_file()->get_section_by_id(i));
SgAsmElfSection *target = isSgAsmElfSection(fhdr->get_file()->get_section_by_id(shdr->get_sh_link()));
assert(source); /* because we created it above */
source->set_linked_section(target);
}
}
/* Finish parsing sections now that we have basic info for all the sections. */
for (size_t i=0; i<is_parsed.size(); i++)
is_parsed[i]->finish_parsing();
return this;
}
