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Fix resolving symbols for section-relative relocations

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Also fixes MIPS `j` handling when jumping within the function.

Reworks `ObjReloc` struct to be a little more sensible.
This commit is contained in:
Luke Street
2024-10-11 18:09:18 -06:00
parent 83de98b5ee
commit 676488433f
11 changed files with 198 additions and 140 deletions
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106
objdiff-core/src/obj/read.rs
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@@ -13,8 +13,8 @@ use object::{
endian::LittleEndian as LE,
pe::{ImageAuxSymbolFunctionBeginEnd, ImageLinenumber},
read::coff::{CoffFile, CoffHeader, ImageSymbol},
BinaryFormat, File, Object, ObjectSection, ObjectSymbol, RelocationTarget, SectionIndex,
SectionKind, Symbol, SymbolIndex, SymbolKind, SymbolScope, SymbolSection,
BinaryFormat, File, Object, ObjectSection, ObjectSymbol, RelocationTarget, Section,
SectionIndex, SectionKind, Symbol, SymbolIndex, SymbolKind, SymbolScope,
};
use crate::{
@@ -41,7 +41,6 @@ fn to_obj_symbol(
arch: &dyn ObjArch,
obj_file: &File<'_>,
symbol: &Symbol<'_, '_>,
addend: i64,
split_meta: Option<&SplitMeta>,
) -> Result<ObjSymbol> {
let mut name = symbol.name().context("Failed to process symbol name")?;
@@ -111,7 +110,7 @@ fn to_obj_symbol(
size_known: symbol.size() != 0,
kind,
flags,
addend,
orig_section_index: symbol.section_index().map(|i| i.0),
virtual_address,
original_index: Some(symbol.index().0),
bytes: bytes.to_vec(),
@@ -177,7 +176,7 @@ fn symbols_by_section(
continue;
}
}
result.push(to_obj_symbol(arch, obj_file, symbol, 0, split_meta)?);
result.push(to_obj_symbol(arch, obj_file, symbol, split_meta)?);
}
result.sort_by(|a, b| a.address.cmp(&b.address).then(a.size.cmp(&b.size)));
let mut iter = result.iter_mut().peekable();
@@ -217,7 +216,7 @@ fn symbols_by_section(
ObjSectionKind::Data | ObjSectionKind::Bss => ObjSymbolKind::Object,
},
flags: Default::default(),
addend: 0,
orig_section_index: Some(section.orig_index),
virtual_address: None,
original_index: None,
bytes: Vec::new(),
@@ -234,7 +233,7 @@ fn common_symbols(
obj_file
.symbols()
.filter(Symbol::is_common)
.map(|symbol| to_obj_symbol(arch, obj_file, &symbol, 0, split_meta))
.map(|symbol| to_obj_symbol(arch, obj_file, &symbol, split_meta))
.collect::<Result<Vec<ObjSymbol>>>()
}
@@ -245,10 +244,18 @@ fn best_symbol<'r, 'data, 'file>(
symbols: &'r [Symbol<'data, 'file>],
address: u64,
) -> Option<&'r Symbol<'data, 'file>> {
let closest_symbol_index = match symbols.binary_search_by_key(&address, |s| s.address()) {
let mut closest_symbol_index = match symbols.binary_search_by_key(&address, |s| s.address()) {
Ok(index) => Some(index),
Err(index) => index.checked_sub(1),
}?;
// The binary search may not find the first symbol at the address, so work backwards
let target_address = symbols[closest_symbol_index].address();
while let Some(prev_index) = closest_symbol_index.checked_sub(1) {
if symbols[prev_index].address() != target_address {
break;
}
closest_symbol_index = prev_index;
}
let mut best_symbol: Option<&'r Symbol<'data, 'file>> = None;
for symbol in symbols.iter().skip(closest_symbol_index) {
if symbol.address() > address {
@@ -276,24 +283,15 @@ fn best_symbol<'r, 'data, 'file>(
fn find_section_symbol(
arch: &dyn ObjArch,
obj_file: &File<'_>,
section: &Section,
section_symbols: &[Symbol<'_, '_>],
target: &Symbol<'_, '_>,
address: u64,
split_meta: Option<&SplitMeta>,
) -> Result<ObjSymbol> {
if let Some(symbol) = best_symbol(section_symbols, address) {
return to_obj_symbol(
arch,
obj_file,
symbol,
address as i64 - symbol.address() as i64,
split_meta,
);
return to_obj_symbol(arch, obj_file, symbol, split_meta);
}
// Fallback to section symbol
let section_index =
target.section_index().ok_or_else(|| anyhow::Error::msg("Unknown section index"))?;
let section = obj_file.section_by_index(section_index)?;
Ok(ObjSymbol {
name: section.name()?.to_string(),
demangled_name: None,
@@ -303,7 +301,7 @@ fn find_section_symbol(
size_known: false,
kind: ObjSymbolKind::Section,
flags: Default::default(),
addend: address as i64 - section.address() as i64,
orig_section_index: Some(section.index().0),
virtual_address: None,
original_index: None,
bytes: Vec::new(),
@@ -314,7 +312,7 @@ fn relocations_by_section(
arch: &dyn ObjArch,
obj_file: &File<'_>,
section: &ObjSection,
section_symbols: &[Symbol<'_, '_>],
section_symbols: &[Vec<Symbol<'_, '_>>],
split_meta: Option<&SplitMeta>,
) -> Result<Vec<ObjReloc>> {
let obj_section = obj_file.section_by_index(SectionIndex(section.orig_index))?;
@@ -339,37 +337,36 @@ fn relocations_by_section(
_ => bail!("Unhandled relocation target: {:?}", reloc.target()),
};
let flags = reloc.flags(); // TODO validate reloc here?
let target_section = match symbol.section() {
SymbolSection::Common => Some(".comm".to_string()),
SymbolSection::Section(idx) => {
obj_file.section_by_index(idx).and_then(|s| s.name().map(|s| s.to_string())).ok()
}
_ => None,
};
let addend = if reloc.has_implicit_addend() {
let mut addend = if reloc.has_implicit_addend() {
arch.implcit_addend(obj_file, section, address, &reloc)?
} else {
reloc.addend()
};
// println!("Reloc: {reloc:?}, symbol: {symbol:?}, addend: {addend:#x}");
let target = match symbol.kind() {
SymbolKind::Text | SymbolKind::Data | SymbolKind::Label | SymbolKind::Unknown => {
to_obj_symbol(arch, obj_file, &symbol, addend, split_meta)
to_obj_symbol(arch, obj_file, &symbol, split_meta)?
}
SymbolKind::Section => {
ensure!(addend >= 0, "Negative addend in reloc: {addend}");
find_section_symbol(
ensure!(addend >= 0, "Negative addend in section reloc: {addend}");
let section_index = symbol
.section_index()
.ok_or_else(|| anyhow!("Section symbol {symbol:?} has no section index"))?;
let section = obj_file.section_by_index(section_index)?;
let symbol = find_section_symbol(
arch,
obj_file,
section_symbols,
&symbol,
&section,
&section_symbols[section_index.0],
addend as u64,
split_meta,
)
)?;
// Adjust addend to be relative to the selected symbol
addend = (symbol.address - section.address()) as i64;
symbol
}
kind => Err(anyhow!("Unhandled relocation symbol type {kind:?}")),
}?;
relocations.push(ObjReloc { flags, address, target, target_section });
kind => bail!("Unhandled relocation symbol type {kind:?}"),
};
relocations.push(ObjReloc { flags, address, target, addend });
}
Ok(relocations)
}
@@ -591,7 +588,7 @@ fn update_combined_symbol(symbol: ObjSymbol, address_change: i64) -> Result<ObjS
size_known: symbol.size_known,
kind: symbol.kind,
flags: symbol.flags,
addend: symbol.addend,
orig_section_index: symbol.orig_section_index,
virtual_address: if let Some(virtual_address) = symbol.virtual_address {
Some((virtual_address as i64 + address_change).try_into()?)
} else {
@@ -617,8 +614,8 @@ fn combine_sections(section: ObjSection, combine: ObjSection) -> Result<ObjSecti
relocations.push(ObjReloc {
flags: reloc.flags,
address: (reloc.address as i64 + address_change).try_into()?,
target: reloc.target, // TODO: Should be updated?
target_section: reloc.target_section, // TODO: Same as above
target: reloc.target, // TODO: Should be updated?
addend: reloc.addend,
});
}
@@ -698,27 +695,38 @@ pub fn parse(data: &[u8], config: &DiffObjConfig) -> Result<ObjInfo> {
let obj_file = File::parse(data)?;
let arch = new_arch(&obj_file)?;
let split_meta = split_meta(&obj_file)?;
let mut sections = filter_sections(&obj_file, split_meta.as_ref())?;
let mut name_counts: HashMap<String, u32> = HashMap::new();
for section in &mut sections {
// Create sorted symbol list for each section
let mut section_symbols = Vec::with_capacity(obj_file.sections().count());
for section in obj_file.sections() {
let mut symbols = obj_file
.symbols()
.filter(|s| s.section_index() == Some(SectionIndex(section.orig_index)))
.filter(|s| s.section_index() == Some(section.index()))
.collect::<Vec<_>>();
symbols.sort_by_key(|s| s.address());
let section_index = section.index().0;
if section_index >= section_symbols.len() {
section_symbols.resize_with(section_index + 1, Vec::new);
}
section_symbols[section_index] = symbols;
}
let mut sections = filter_sections(&obj_file, split_meta.as_ref())?;
let mut section_name_counts: HashMap<String, u32> = HashMap::new();
for section in &mut sections {
section.symbols = symbols_by_section(
arch.as_ref(),
&obj_file,
section,
&symbols,
&section_symbols[section.orig_index],
split_meta.as_ref(),
&mut name_counts,
&mut section_name_counts,
)?;
section.relocations = relocations_by_section(
arch.as_ref(),
&obj_file,
section,
&symbols,
&section_symbols,
split_meta.as_ref(),
)?;
}