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Fix several issues with string literal detection (#351)

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* Support detecting more symbol names for strings

* Fix string detectiong being broken for encodings that use null terminators

* Add test cases for string detection and decoding

* Fix test helper function sometimes being considered dead code

* Clippy fixes
This commit is contained in:
LagoLunatic
2026-05-03 21:27:12 -04:00
committed by GitHub
parent 3cebee6766
commit 13f1267eac
7 changed files with 139 additions and 22 deletions
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objdiff-core/src/arch/mod.rs
+21 -18
View File
@@ -42,15 +42,15 @@ pub mod x86;
pub const OPCODE_INVALID: u16 = u16::MAX;
pub const OPCODE_DATA: u16 = u16::MAX - 1;
const SUPPORTED_ENCODINGS: [(&encoding_rs::Encoding, &str); 7] = [
const SUPPORTED_ENCODINGS_WITH_NULL_TERM: [(&encoding_rs::Encoding, &str); 5] = [
(encoding_rs::UTF_8, "UTF-8"),
(encoding_rs::SHIFT_JIS, "Shift JIS"),
(encoding_rs::UTF_16BE, "UTF-16BE"),
(encoding_rs::UTF_16LE, "UTF-16LE"),
(encoding_rs::WINDOWS_1252, "Windows-1252"),
(encoding_rs::EUC_JP, "EUC-JP"),
(encoding_rs::BIG5, "Big5"),
];
const SUPPORTED_ENCODINGS_NO_NULL_TERM: [(&encoding_rs::Encoding, &str); 2] =
[(encoding_rs::UTF_16BE, "UTF-16BE"), (encoding_rs::UTF_16LE, "UTF-16LE")];
/// Represents the type of data associated with an instruction
#[derive(PartialEq)]
@@ -174,24 +174,27 @@ impl DataType {
strs.push((format!("{bytes:#?}"), None, None));
}
DataType::String => {
// Special case to display (ASCII) as the label for ASCII-only strings.
let mut is_ascii = false;
if bytes.is_ascii()
&& let Ok(str) = str::from_utf8(bytes)
{
let trimmed = str.trim_end_matches('\0');
if !trimmed.is_empty() {
let copy_string = escape_special_ascii_characters(trimmed);
strs.push((trimmed.to_string(), Some("ASCII".into()), Some(copy_string)));
is_ascii = true;
if let Some(nul_idx) = bytes.iter().position(|&c| c == b'\0') {
let str_bytes = &bytes[..nul_idx];
// Special case to display (ASCII) as the label for ASCII-only strings.
let (cow, _, had_errors) = encoding_rs::UTF_8.decode(str_bytes);
if !had_errors && cow.is_ascii() {
let string = format!("{cow}");
let copy_string = escape_special_ascii_characters(&string);
strs.push((string, Some("ASCII".into()), Some(copy_string)));
}
for (encoding, encoding_name) in SUPPORTED_ENCODINGS_WITH_NULL_TERM {
let (cow, _, had_errors) = encoding.decode(str_bytes);
// Avoid showing ASCII-only strings more than once if the encoding is ASCII-compatible.
if !had_errors && (!encoding.is_ascii_compatible() || !cow.is_ascii()) {
let string = format!("{cow}");
let copy_string = escape_special_ascii_characters(&string);
strs.push((string, Some(encoding_name.into()), Some(copy_string)));
}
}
}
for (encoding, encoding_name) in SUPPORTED_ENCODINGS {
// Avoid showing ASCII-only strings more than once if the encoding is ASCII-compatible.
if is_ascii && encoding.is_ascii_compatible() {
continue;
}
for (encoding, encoding_name) in SUPPORTED_ENCODINGS_NO_NULL_TERM {
let (cow, _, had_errors) = encoding.decode(bytes);
if had_errors {
continue;
objdiff-core/src/arch/ppc/flow_analysis.rs
+2
View File
@@ -513,6 +513,8 @@ pub fn ppc_data_flow_analysis(
)
}
// Note: This function only supports MWCC ASCII strings.
// Other encodings and other compilers are currently not supported.
fn get_string_data(obj: &Object, symbol_index: usize, offset: Simm) -> Option<&str> {
if let Some(sym) = obj.symbols.get(symbol_index)
&& sym.name.starts_with("@stringBase")
objdiff-core/src/arch/ppc/mod.rs
+5 -2
View File
@@ -359,9 +359,12 @@ impl Arch for ArchPpc {
fn guess_data_type(&self, resolved: ResolvedInstructionRef, bytes: &[u8]) -> Option<DataType> {
if resolved.relocation.is_some_and(|r| {
r.symbol.name.starts_with("@stringBase") || r.symbol.name.starts_with("$SG")
r.symbol.name.starts_with("@stringBase")
|| r.symbol.name.starts_with("@wstringBase")
|| r.symbol.name.starts_with("$SG")
|| r.symbol.demangled_name == Some("`string'".to_string())
}) {
// Pooled string.
// Compiler-generated symbol name for a string or a pool of strings.
return Some(DataType::String);
}
let opcode = powerpc::Opcode::from(resolved.ins_ref.opcode);