bool ElfFile::decode(address addr, char* buf, int buflen, int* offset) {
// something already went wrong, just give up
if (NullDecoder::is_error(m_status)) {
return false;
}
ElfSymbolTable* symbol_table = m_symbol_tables;
int string_table_index;
int pos_in_string_table;
int off = INT_MAX;
bool found_symbol = false;
while (symbol_table != NULL) {
if (symbol_table->lookup(addr, &string_table_index, &pos_in_string_table, &off)) {
found_symbol = true;
}
symbol_table = symbol_table->m_next;
}
if (!found_symbol) return false;
ElfStringTable* string_table = get_string_table(string_table_index);
if (string_table == NULL) {
m_status = NullDecoder::file_invalid;
return false;
}
if (offset) *offset = off;
return string_table->string_at(pos_in_string_table, buf, buflen);
}
bool ElfFile::load_tables() {
assert(m_file, "file not open");
assert(!NullDecoder::is_error(m_status), "already in error");
// read elf file header
if (fread(&m_elfHdr, sizeof(m_elfHdr), 1, m_file) != 1) {
m_status = NullDecoder::file_invalid;
return false;
}
if (!is_elf_file(m_elfHdr)) {
m_status = NullDecoder::file_invalid;
return false;
}
// walk elf file's section headers, and load string tables
Elf_Shdr shdr;
if (!fseek(m_file, m_elfHdr.e_shoff, SEEK_SET)) {
if (NullDecoder::is_error(m_status)) return false;
for (int index = 0; index < m_elfHdr.e_shnum; index ++) {
if (fread((void*)&shdr, sizeof(Elf_Shdr), 1, m_file) != 1) {
m_status = NullDecoder::file_invalid;
return false;
}
if (shdr.sh_type == SHT_STRTAB) {
// string tables
ElfStringTable* table = new (std::nothrow) ElfStringTable(m_file, shdr, index);
if (table == NULL) {
m_status = NullDecoder::out_of_memory;
return false;
}
add_string_table(table);
} else if (shdr.sh_type == SHT_SYMTAB || shdr.sh_type == SHT_DYNSYM) {
// symbol tables
ElfSymbolTable* table = new (std::nothrow) ElfSymbolTable(m_file, shdr);
if (table == NULL) {
m_status = NullDecoder::out_of_memory;
return false;
}
add_symbol_table(table);
}
}
#if defined(PPC64) && !defined(ABI_ELFv2)
// Now read the .opd section wich contains the PPC64 function descriptor table.
// The .opd section is only available on PPC64 (see for example:
// http://refspecs.linuxfoundation.org/LSB_3.1.1/LSB-Core-PPC64/LSB-Core-PPC64/specialsections.html)
// so this code should do no harm on other platforms but because of performance reasons we only
// execute it on PPC64 platforms.
// Notice that we can only find the .opd section after we have successfully read in the string
// tables in the previous loop, because we need to query the name of each section which is
// contained in one of the string tables (i.e. the one with the index m_elfHdr.e_shstrndx).
// Reset the file pointer
if (fseek(m_file, m_elfHdr.e_shoff, SEEK_SET)) {
m_status = NullDecoder::file_invalid;
return false;
}
for (int index = 0; index < m_elfHdr.e_shnum; index ++) {
if (fread((void*)&shdr, sizeof(Elf_Shdr), 1, m_file) != 1) {
m_status = NullDecoder::file_invalid;
return false;
}
if (m_elfHdr.e_shstrndx != SHN_UNDEF && shdr.sh_type == SHT_PROGBITS) {
ElfStringTable* string_table = get_string_table(m_elfHdr.e_shstrndx);
if (string_table == NULL) {
m_status = NullDecoder::file_invalid;
return false;
}
char buf[8]; // '8' is enough because we only want to read ".opd"
if (string_table->string_at(shdr.sh_name, buf, sizeof(buf)) && !strncmp(".opd", buf, 4)) {
m_funcDesc_table = new (std::nothrow) ElfFuncDescTable(m_file, shdr, index);
if (m_funcDesc_table == NULL) {
m_status = NullDecoder::out_of_memory;
return false;
}
break;
}
}
}
#endif
}
return true;
}