/** Returns info about the size of the entries based on information already available. Any or all arguments may be null
* pointers if the caller is not interested in the value. */
rose_addr_t
SgAsmElfSectionTable::calculate_sizes(size_t *entsize, size_t *required, size_t *optional, size_t *entcount) const
{
SgAsmElfFileHeader *fhdr = dynamic_cast<SgAsmElfFileHeader*>(get_header());
ROSE_ASSERT(fhdr!=NULL);
size_t struct_size = 0;
size_t extra_size = fhdr->get_shextrasz();
size_t entry_size = 0;
size_t nentries = 0;
/* Size of required part of each entry */
if (4==fhdr->get_word_size()) {
struct_size = sizeof(SgAsmElfSectionTableEntry::Elf32SectionTableEntry_disk);
} else if (8==fhdr->get_word_size()) {
struct_size = sizeof(SgAsmElfSectionTableEntry::Elf64SectionTableEntry_disk);
} else {
throw FormatError("bad ELF word size");
}
/* Entire entry should be at least large enough for the required part. */
entry_size = struct_size;
/* Size of optional parts. If we've parsed the table then use the largest optional part, otherwise assume the entry from
* the ELF File Header is correct. */
SgAsmGenericSectionPtrList sections = fhdr->get_sections()->get_sections();
for (size_t i=0; i<sections.size(); i++) {
SgAsmElfSection *elfsec = dynamic_cast<SgAsmElfSection*>(sections[i]);
if (elfsec && elfsec->get_section_entry()) {
ROSE_ASSERT(elfsec->get_id()>=0);
nentries = std::max(nentries, (size_t)elfsec->get_id()+1);
extra_size = std::max(extra_size, elfsec->get_section_entry()->get_extra().size());
}
}
/* Total number of entries. Either we haven't parsed the section table yet (nor created the sections it defines) or we
* have. In the former case we use the setting from the ELF File Header. Otherwise the table has to be large enough to
* store the section with the largest ID (ID also serves as the index into the ELF Section Table). */
if (0==nentries)
nentries = fhdr->get_e_shnum();
/* Return values */
if (entsize)
*entsize = entry_size;
if (required)
*required = struct_size;
if (optional)
*optional = extra_size;
if (entcount)
*entcount = nentries;
return entry_size * nentries;
}
/** Write the section table section back to disk */
void
SgAsmElfSectionTable::unparse(std::ostream &f) const
{
SgAsmElfFileHeader *fhdr = dynamic_cast<SgAsmElfFileHeader*>(get_header());
ROSE_ASSERT(fhdr!=NULL);
ByteOrder::Endianness sex = fhdr->get_sex();
SgAsmGenericSectionPtrList sections = fhdr->get_sectab_sections();
/* Write the sections first */
for (size_t i=0; i<sections.size(); i++)
sections[i]->unparse(f);
unparse_holes(f);
/* Calculate sizes. The ELF File Header should have been updated in reallocate() prior to unparsing. */
size_t ent_size, struct_size, opt_size, nentries;
calculate_sizes(&ent_size, &struct_size, &opt_size, &nentries);
ROSE_ASSERT(fhdr->get_shextrasz()==opt_size);
ROSE_ASSERT(fhdr->get_e_shnum()==nentries);
/* Write the section table entries */
for (size_t i=0; i<sections.size(); ++i) {
SgAsmElfSection *section = dynamic_cast<SgAsmElfSection*>(sections[i]);
ROSE_ASSERT(section!=NULL);
SgAsmElfSectionTableEntry *shdr = section->get_section_entry();
ROSE_ASSERT(shdr!=NULL);
ROSE_ASSERT(shdr->get_sh_offset()==section->get_offset());/*section table entry should have been updated in reallocate()*/
int id = section->get_id();
ROSE_ASSERT(id>=0 && (size_t)id<nentries);
SgAsmElfSectionTableEntry::Elf32SectionTableEntry_disk disk32;
SgAsmElfSectionTableEntry::Elf64SectionTableEntry_disk disk64;
void *disk = NULL;
if (4==fhdr->get_word_size()) {
disk = shdr->encode(sex, &disk32);
} else if (8==fhdr->get_word_size()) {
disk = shdr->encode(sex, &disk64);
} else {
ROSE_ASSERT(!"invalid word size");
}
/* The disk struct */
rose_addr_t spos = write(f, id*ent_size, struct_size, disk);
if (shdr->get_extra().size() > 0) {
ROSE_ASSERT(shdr->get_extra().size()<=opt_size);
write(f, spos, shdr->get_extra());
}
}
}
/** 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;
}
