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use std::collections::HashMap;
use std::path::PathBuf;
use goblin::elf::header::{ET_DYN, ET_EXEC};
use goblin::elf::program_header::{PT_INTERP, PT_LOAD};
use goblin::elf::section_header::SHN_UNDEF;
use goblin::elf::Elf as GoblinElf;
use once_cell::sync::OnceCell;
pub struct Elf<'a> {
path: PathBuf,
elf: GoblinElf<'a>,
symbols: OnceCell<HashMap<&'a str, usize>>,
got: OnceCell<HashMap<&'a str, usize>>,
plt: OnceCell<HashMap<&'a str, usize>>,
statically_linked: bool,
address: usize,
}
impl<'a> Elf<'a> {
pub fn new(path: impl Into<PathBuf>) -> Self {
let path = path.into();
let mapped = Box::new(
unsafe {
memmap::MmapOptions::new()
.map(&std::fs::File::open(&path).expect("Could not open file"))
}
.expect("Could not mmap file"),
);
let mapped = Box::leak(mapped);
Self::construct(path, mapped)
}
pub fn from_bytes(bytes: &'a [u8]) -> Self {
Self::construct("".into(), bytes)
}
fn construct(path: PathBuf, bytes: &'a [u8]) -> Self {
let internal = GoblinElf::parse(bytes).expect("Not a valid ELF file");
let mut load_address = 0;
if internal.header.e_type != ET_DYN {
internal
.program_headers
.iter()
.filter(|seg| seg.p_type == PT_LOAD)
.for_each(|seg| {
let addr = seg.p_vaddr;
if addr != 0 && (addr < load_address || load_address == 0) {
load_address = addr;
}
});
}
let mut statically_linked = internal.header.e_type == ET_EXEC && load_address != 0;
if internal
.program_headers
.iter()
.any(|seg| seg.p_type == PT_INTERP)
{
statically_linked = false;
}
Self {
path,
elf: internal,
symbols: Default::default(),
got: Default::default(),
plt: Default::default(),
statically_linked,
address: load_address as usize,
}
}
pub fn path(&self) -> &PathBuf {
&self.path
}
pub fn bits(&self) -> usize {
if self.elf.is_64 {
64
} else {
32
}
}
pub fn symbols(&self) -> &HashMap<&'a str, usize> {
self.symbols.get_or_init(|| self.populate_symbols())
}
fn populate_symbols(&self) -> HashMap<&'a str, usize> {
let mut syms = HashMap::new();
for sym in &self.elf.syms {
if sym.st_value == 0 {
continue;
}
let name = self.elf.strtab.get_at(sym.st_name).unwrap_or("");
if name.is_empty() {
continue;
}
syms.insert(name, sym.st_value as usize);
}
for sym in &self.elf.dynsyms {
if sym.st_value == 0 {
continue;
}
let name = self.elf.dynstrtab.get_at(sym.st_name).unwrap_or("");
if name.is_empty() {
continue;
}
syms.insert(name, sym.st_value as usize);
}
for (name, addr) in self.plt() {
if !syms.contains_key(name) {
syms.insert(name, *addr);
}
}
for (name, addr) in self.got() {
if !syms.contains_key(name) {
syms.insert(name, *addr);
}
}
syms
}
pub fn got(&self) -> &HashMap<&'a str, usize> {
self.got.get_or_init(|| self.populate_got())
}
fn populate_got(&self) -> HashMap<&'a str, usize> {
if self.statically_linked {
return Default::default();
}
let mut got = HashMap::new();
for (idx, sec) in &self.elf.shdr_relocs {
let shdr = &self.elf.section_headers[*idx];
if shdr.sh_link == SHN_UNDEF {
continue;
}
for reloc in sec.iter() {
let sym = reloc.r_sym;
if sym == 0 {
continue;
}
if let Some(sym) = self.elf.dynsyms.get(sym) {
if let Some(name) = self.elf.dynstrtab.get_at(sym.st_name) {
if name.is_empty() || reloc.r_offset == 0 {
continue;
}
got.insert(name, reloc.r_offset as usize);
}
}
}
}
got
}
pub fn plt(&self) -> &HashMap<&'a str, usize> {
self.plt.get_or_init(|| self.populate_plt())
}
fn populate_plt(&self) -> HashMap<&'a str, usize> {
if self.statically_linked || self.got().is_empty() {
return Default::default();
}
let plt_section = self
.elf
.section_headers
.iter()
.find(|shdr| matches!(self.elf.shdr_strtab.get_at(shdr.sh_name), Some(".plt")))
.expect("No .plt section");
let mut plt = HashMap::new();
for (i, reloc) in self.elf.pltrelocs.iter().enumerate() {
if let Some(sym) = self.elf.dynsyms.get(reloc.r_sym) {
if let Some(name) = self.elf.dynstrtab.get_at(sym.st_name) {
plt.insert(
name,
(plt_section.sh_addr + (plt_section.sh_entsize * (i + 1) as u64)) as usize,
);
}
}
}
plt
}
pub fn address(&self) -> usize {
self.address
}
pub fn set_address(&mut self, address: usize) -> usize {
let delta = address as i64 - self.address as i64;
self.address = address;
self.symbols();
self.symbols
.get_mut()
.unwrap()
.iter_mut()
.for_each(|(_, v)| {
let tmp = *v as i64;
*v = (tmp + delta) as usize
});
self.got();
self.got.get_mut().unwrap().iter_mut().for_each(|(_, v)| {
let tmp = *v as i64;
*v = (tmp + delta) as usize
});
self.plt();
self.plt.get_mut().unwrap().iter_mut().for_each(|(_, v)| {
let tmp = *v as i64;
*v = (tmp + delta) as usize
});
address
}
}