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|
//! Apply relocations to addresses and offsets during parsing, instead of requiring the data
//! to be fully relocated prior to parsing. Necessary to load object files that reference dwarf
//! objects (not just executables). Implementation derived from Gimli's `dwarfdump` example.
use std::borrow::Cow;
use gimli;
use hashbrown::HashMap;
use object::{Object, ObjectSection, ObjectSymbol, RelocationKind, RelocationTarget};
use crate::{Error, Result};
pub(crate) type RelocationMap = HashMap<usize, object::Relocation>;
#[derive(Debug, Clone)]
pub(crate) struct Relocate<'a, R: gimli::Reader<Offset = usize>> {
pub(crate) relocations: &'a RelocationMap,
pub(crate) section: R,
pub(crate) reader: R,
}
impl<'a, R: gimli::Reader<Offset = usize>> Relocate<'a, R> {
fn relocate(&self, offset: usize, value: u64) -> u64 {
if let Some(relocation) = self.relocations.get(&offset) {
if matches!(relocation.kind(), RelocationKind::Absolute) {
if relocation.has_implicit_addend() {
// Use the explicit addend too, because it may have the symbol value.
return value.wrapping_add(relocation.addend() as u64);
} else {
return relocation.addend() as u64;
}
}
};
value
}
}
impl<'a, R: gimli::Reader<Offset = usize>> gimli::Reader for Relocate<'a, R> {
type Endian = R::Endian;
type Offset = R::Offset;
fn read_address(&mut self, address_size: u8) -> gimli::Result<u64> {
let offset = self.reader.offset_from(&self.section);
let value = self.reader.read_address(address_size)?;
Ok(self.relocate(offset, value))
}
fn read_length(&mut self, format: gimli::Format) -> gimli::Result<usize> {
let offset = self.reader.offset_from(&self.section);
let value = self.reader.read_length(format)?;
<usize as gimli::ReaderOffset>::from_u64(self.relocate(offset, value as u64))
}
fn read_offset(&mut self, format: gimli::Format) -> gimli::Result<usize> {
let offset = self.reader.offset_from(&self.section);
let value = self.reader.read_offset(format)?;
<usize as gimli::ReaderOffset>::from_u64(self.relocate(offset, value as u64))
}
fn read_sized_offset(&mut self, size: u8) -> gimli::Result<usize> {
let offset = self.reader.offset_from(&self.section);
let value = self.reader.read_sized_offset(size)?;
<usize as gimli::ReaderOffset>::from_u64(self.relocate(offset, value as u64))
}
#[inline]
fn split(&mut self, len: Self::Offset) -> gimli::Result<Self> {
let mut other = self.clone();
other.reader.truncate(len)?;
self.reader.skip(len)?;
Ok(other)
}
// All remaining methods simply delegate to `self.reader`.
#[inline]
fn endian(&self) -> Self::Endian {
self.reader.endian()
}
#[inline]
fn len(&self) -> Self::Offset {
self.reader.len()
}
#[inline]
fn empty(&mut self) {
self.reader.empty()
}
#[inline]
fn truncate(&mut self, len: Self::Offset) -> gimli::Result<()> {
self.reader.truncate(len)
}
#[inline]
fn offset_from(&self, base: &Self) -> Self::Offset {
self.reader.offset_from(&base.reader)
}
#[inline]
fn offset_id(&self) -> gimli::ReaderOffsetId {
self.reader.offset_id()
}
#[inline]
fn lookup_offset_id(&self, id: gimli::ReaderOffsetId) -> Option<Self::Offset> {
self.reader.lookup_offset_id(id)
}
#[inline]
fn find(&self, byte: u8) -> gimli::Result<Self::Offset> {
self.reader.find(byte)
}
#[inline]
fn skip(&mut self, len: Self::Offset) -> gimli::Result<()> {
self.reader.skip(len)
}
#[inline]
fn to_slice(&self) -> gimli::Result<Cow<'_, [u8]>> {
self.reader.to_slice()
}
#[inline]
fn to_string(&self) -> gimli::Result<Cow<'_, str>> {
self.reader.to_string()
}
#[inline]
fn to_string_lossy(&self) -> gimli::Result<Cow<'_, str>> {
self.reader.to_string_lossy()
}
#[inline]
fn read_slice(&mut self, buf: &mut [u8]) -> gimli::Result<()> {
self.reader.read_slice(buf)
}
}
pub(crate) fn add_relocations(
relocations: &mut RelocationMap,
file: &object::File<'_>,
section: &object::Section<'_, '_>,
) -> Result<()> {
for (offset64, mut relocation) in section.relocations() {
let offset = offset64 as usize;
if offset as u64 != offset64 {
continue;
}
let offset = offset as usize;
if matches!(relocation.kind(), RelocationKind::Absolute) {
if let RelocationTarget::Symbol(symbol_idx) = relocation.target() {
match file.symbol_by_index(symbol_idx) {
Ok(symbol) => {
let addend = symbol.address().wrapping_add(relocation.addend() as u64);
relocation.set_addend(addend as i64);
}
Err(_) => {
return Err(Error::RelocationWithInvalidSymbol(
section
.name()
.map_err(|e| Error::NamelessSection(e, offset))?
.to_string(),
offset,
));
}
}
}
if relocations.insert(offset, relocation).is_some() {
return Err(Error::MultipleRelocations(
section.name().map_err(|e| Error::NamelessSection(e, offset))?.to_string(),
offset,
));
}
} else {
return Err(Error::UnsupportedRelocation(
section.name().map_err(|e| Error::NamelessSection(e, offset))?.to_string(),
offset,
));
}
}
Ok(())
}
|
