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Update GOT relocations

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This commit is contained in:
Brendan Hansknecht 2021-08-26 21:20:52 -07:00
parent f0f37bfe03
commit a188720a16
2 changed files with 62 additions and 23 deletions
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83
linker/src/lib.rs
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@ -177,18 +177,18 @@ pub fn preprocess(matches: &ArgMatches) -> io::Result<i32> {
let name = sym.name().unwrap().to_string();
// special exceptions for memcpy and memset.
if &name == "roc_memcpy" {
md.roc_func_addresses
md.roc_symbol_vaddresses
.insert("memcpy".to_string(), sym.address() as u64);
} else if name == "roc_memset" {
md.roc_func_addresses
md.roc_symbol_vaddresses
.insert("memset".to_string(), sym.address() as u64);
}
md.roc_func_addresses.insert(name, sym.address() as u64);
md.roc_symbol_vaddresses.insert(name, sym.address() as u64);
}
println!(
"Found roc function definitions: {:x?}",
md.roc_func_addresses
"Found roc symbol definitions: {:x?}",
md.roc_symbol_vaddresses
);
let exec_parsing_duration = exec_parsing_start.elapsed().unwrap();
@ -749,6 +749,16 @@ pub fn preprocess(matches: &ArgMatches) -> io::Result<i32> {
let r_offset = rel.r_offset.get(NativeEndian);
if md.virtual_shift_start <= r_offset {
rel.r_offset = endian::U64::new(LittleEndian, r_offset + md.added_byte_count);
// Deal with potential adjusts to absolute jumps.
match rel.r_type(LittleEndian, false) {
elf::R_X86_64_RELATIVE => {
let r_addend = rel.r_addend.get(LittleEndian);
rel.r_addend
.set(LittleEndian, r_addend + md.added_byte_count as i64);
}
// TODO: Verify other relocation types.
_ => {}
}
}
}
}
@ -988,6 +998,7 @@ pub fn surgery(matches: &ArgMatches) -> io::Result<i32> {
let mut sh_tab = vec![];
sh_tab.extend_from_slice(&exec_mmap[sh_offset as usize..sh_offset as usize + sh_size]);
// TODO: I think this can move in by sh_size.
let mut offset = md.exec_len as usize;
offset = aligned_offset(offset);
// TODO: Switch to using multiple segments.
@ -1049,10 +1060,13 @@ pub fn surgery(matches: &ArgMatches) -> io::Result<i32> {
exec_mmap[offset..offset + data.len()].copy_from_slice(&data);
for sym in symbols.iter() {
if sym.section() == SymbolSection::Section(sec.index()) {
symbol_offset_map.insert(
sym.index().0,
offset + sym.address() as usize - new_segment_offset,
);
let name = sym.name().unwrap_or_default().to_string();
if !md.roc_symbol_vaddresses.contains_key(&name) {
symbol_offset_map.insert(
sym.index().0,
offset + sym.address() as usize - new_segment_offset,
);
}
}
}
offset += size;
@ -1076,6 +1090,7 @@ pub fn surgery(matches: &ArgMatches) -> io::Result<i32> {
let new_text_section_offset = offset;
let mut app_func_size_map: MutMap<String, u64> = MutMap::default();
let mut app_func_segment_offset_map: MutMap<String, usize> = MutMap::default();
let mut got_sections: Vec<(u64, u64)> = vec![];
for sec in text_sections {
let data = match sec.uncompressed_data() {
Ok(data) => data,
@ -1103,11 +1118,13 @@ pub fn surgery(matches: &ArgMatches) -> io::Result<i32> {
let current_section_offset = (offset - new_segment_offset) as i64;
for sym in symbols.iter() {
if sym.section() == SymbolSection::Section(sec.index()) {
symbol_offset_map.insert(
sym.index().0,
offset + sym.address() as usize - new_segment_offset,
);
let name = sym.name().unwrap_or_default().to_string();
if !md.roc_symbol_vaddresses.contains_key(&name) {
symbol_offset_map.insert(
sym.index().0,
offset + sym.address() as usize - new_segment_offset,
);
}
if md.app_functions.contains(&name) {
app_func_segment_offset_map.insert(
name.clone(),
@ -1117,7 +1134,8 @@ pub fn surgery(matches: &ArgMatches) -> io::Result<i32> {
}
}
}
let mut got_offset = aligned_offset(offset + size);
offset = aligned_offset(offset + size);
let mut got_offset = offset;
for rel in sec.relocations() {
if verbose {
println!("\tFound Relocation: {:x?}", rel);
@ -1130,7 +1148,7 @@ pub fn surgery(matches: &ArgMatches) -> io::Result<i32> {
} else if let Ok(sym) = app_obj.symbol_by_index(index) {
// Not one of the apps symbols, check if it is from the roc host.
if let Ok(name) = sym.name() {
if let Some(address) = md.roc_func_addresses.get(name) {
if let Some(address) = md.roc_symbol_vaddresses.get(name) {
Some(
(*address + md.added_byte_count) as i64
- new_segment_vaddr as i64,
@ -1156,15 +1174,33 @@ pub fn surgery(matches: &ArgMatches) -> io::Result<i32> {
if verbose {
println!("GOT hacking this may not work right");
}
let got_val = target_offset as u64 + new_segment_vaddr;
let target_offset = (got_offset - new_segment_offset) as i64;
let data = got_val.to_le_bytes();
// TODO: This doesn't actually work. We also need to add a relocatoin to the rela section.
// These offsets are not actually global offsets due to aslr.
// We either need to actually put these in the GOT, add a new GOT section, or some other hack.
// Putting them in the real GOT is the most correct solution.
// Another solution may be to make the host define all global data.
// The follow code assumes that is the case and will generate invalid code otherwise.
// Also, I wonder if it is possible to avoid true globals somehow.
let target_vaddr = target_offset + new_segment_vaddr as i64;
let data = target_vaddr.to_le_bytes();
exec_mmap[got_offset..got_offset + 8].copy_from_slice(&data);
got_offset = aligned_offset(got_offset + 8);
target_offset - (rel.0 as i64 + current_section_offset)
+ rel.1.addend()
let target_offset = (got_offset - new_segment_offset) as i64;
let base_offset = rel.0 as i64 + current_section_offset;
if verbose {
println!(
"\tThe base offset is: 0x{:x}",
base_offset + current_section_offset
);
println!(
"\tThe got target is: 0x{:x}",
target_offset + current_section_offset
);
println!("\tThe final target is: 0x{:x}", target_vaddr);
}
target_offset - base_offset + rel.1.addend()
}
RelocationKind::Absolute => target_offset + new_segment_vaddr as i64,
x => {
println!("Relocation Kind not yet support: {:?}", x);
return Ok(-1);
@ -1202,7 +1238,10 @@ pub fn surgery(matches: &ArgMatches) -> io::Result<i32> {
}
}
}
offset = got_offset;
if got_offset != offset {
got_sections.push((offset, got_offset - offset));
offset = got_offset;
}
}
if verbose {