Support IDO .mdebug for line numbers (#264)

* Support IDO .mdebug for line numbers

Resolves #179

* Fix wasm build && cargo clippy --fix

* Resolve review comment

objdiff-core/src/obj/mdebug.rs

@@ -0,0 +1,401 @@
+use alloc::vec::Vec;
+
+use anyhow::{Context, Result, bail, ensure};
+use object::{Endianness, Object, ObjectSection};
+
+use super::{Section, SectionKind};
+
+const HDRR_SIZE: usize = 0x60;
+const FDR_SIZE: usize = 0x48;
+const PDR_SIZE: usize = 0x34;
+const SYMR_SIZE: usize = 0x0c;
+
+const ST_PROC: u8 = 6;
+const ST_STATICPROC: u8 = 14;
+const ST_END: u8 = 8;
+
+pub(super) fn parse_line_info_mdebug(
+    obj_file: &object::File,
+    sections: &mut [Section],
+) -> Result<()> {
+    let Some(section) = obj_file.section_by_name(".mdebug") else {
+        return Ok(());
+    };
+
+    let data = section.data().context("failed to read .mdebug contents")?;
+    if data.len() < HDRR_SIZE {
+        return Ok(());
+    }
+
+    let section_file_offset = section.file_range().map(|(offset, _)| offset as usize);
+
+    let endianness = obj_file.endianness();
+    let header = Header::parse(data, endianness)?;
+
+    let symbols_data = slice_at(
+        data,
+        header.cb_sym_offset,
+        header.isym_max.checked_mul(SYMR_SIZE as u32).context("symbol table size overflow")?,
+        section_file_offset,
+    )?;
+    let symbols = parse_symbols(symbols_data, endianness)?;
+
+    let fdr_data = slice_at(
+        data,
+        header.cb_fd_offset,
+        header
+            .ifd_max
+            .checked_mul(FDR_SIZE as u32)
+            .context("file descriptor table size overflow")?,
+        section_file_offset,
+    )?;
+
+    for fdr_index in 0..header.ifd_max as usize {
+        let fdr_offset = fdr_index * FDR_SIZE;
+        let fdr = FileDescriptor::parse(&fdr_data[fdr_offset..fdr_offset + FDR_SIZE], endianness)?;
+        if fdr.cpd == 0 || fdr.csym == 0 {
+            continue;
+        }
+
+        let sym_base = fdr.isym_base as usize;
+        let sym_end = sym_base + fdr.csym as usize;
+        if sym_end > symbols.len() {
+            continue;
+        }
+
+        let Some(line_file_offset) = header.cb_line_offset.checked_add(fdr.cb_line_offset) else {
+            continue;
+        };
+        let Some(line_file_base) =
+            resolve_offset(line_file_offset, data.len(), section_file_offset)
+        else {
+            continue;
+        };
+        let Some(line_file_end) = line_file_base.checked_add(fdr.cb_line as usize) else {
+            continue;
+        };
+        if line_file_end > data.len() {
+            continue;
+        }
+
+        for local_proc_index in 0..fdr.cpd as usize {
+            let pdr_index = fdr.ipd_first as usize + local_proc_index;
+            let pdr_offset = header
+                .cb_pd_offset
+                .checked_add((pdr_index as u32) * PDR_SIZE as u32)
+                .context("procedure descriptor offset overflow")?;
+            let pdr_data = match slice_at(data, pdr_offset, PDR_SIZE as u32, section_file_offset) {
+                Ok(data) => data,
+                Err(_) => continue,
+            };
+            let pdr = ProcDescriptor::parse(pdr_data, endianness)?;
+            if pdr.isym as usize >= fdr.csym as usize {
+                continue;
+            }
+            let global_sym_index = sym_base + pdr.isym as usize;
+            let Some(start_symbol) = symbols.get(global_sym_index) else {
+                continue;
+            };
+            if start_symbol.st != ST_PROC && start_symbol.st != ST_STATICPROC {
+                continue;
+            }
+
+            let local_index = pdr.isym as u32;
+            let mut end_address = None;
+            for sym in &symbols[global_sym_index..sym_end] {
+                if sym.st == ST_END && sym.index == local_index {
+                    end_address = Some(sym.value);
+                    break;
+                }
+            }
+            let Some(end_address) = end_address else {
+                continue;
+            };
+            let Some(size) = end_address.checked_sub(start_symbol.value) else {
+                continue;
+            };
+            if size == 0 || size % 4 != 0 {
+                continue;
+            }
+            let word_count = (size / 4) as usize;
+            if word_count == 0 {
+                continue;
+            }
+
+            let Some(mut cursor) = line_file_base.checked_add(pdr.cb_line_offset as usize) else {
+                continue;
+            };
+            if cursor >= line_file_end {
+                continue;
+            }
+
+            let mut line_number = pdr.ln_low as i32;
+            let mut lines = Vec::with_capacity(word_count);
+            while lines.len() < word_count && cursor < line_file_end {
+                let b0 = data[cursor];
+                cursor += 1;
+                let count = (b0 & 0x0f) as usize + 1;
+                let delta = decode_delta(endianness, b0 >> 4, data, &mut cursor, line_file_end)?;
+                line_number = line_number.wrapping_add(delta as i32);
+                for _ in 0..count {
+                    if lines.len() == word_count {
+                        break;
+                    }
+                    lines.push(line_number);
+                }
+            }
+
+            if lines.len() != word_count {
+                continue;
+            }
+
+            assign_lines(sections, fdr.adr as u64 + pdr.addr as u64, &lines);
+        }
+    }
+
+    Ok(())
+}
+
+fn assign_lines(sections: &mut [Section], base_address: u64, lines: &[i32]) {
+    let mut address = base_address;
+    for &line in lines {
+        if line >= 0
+            && let Some(section) = find_code_section(sections, address)
+        {
+            section.line_info.insert(address, line as u32);
+        }
+        address = address.wrapping_add(4);
+    }
+}
+
+fn find_code_section(sections: &mut [Section], address: u64) -> Option<&mut Section> {
+    sections.iter_mut().find(|section| {
+        section.kind == SectionKind::Code
+            && address >= section.address
+            && address < section.address + section.size
+    })
+}
+
+fn decode_delta(
+    endianness: Endianness,
+    nibble: u8,
+    data: &[u8],
+    cursor: &mut usize,
+    end: usize,
+) -> Result<i32> {
+    if nibble == 8 {
+        ensure!(*cursor + 2 <= end, "extended delta out of range");
+        let bytes: [u8; 2] = data[*cursor..*cursor + 2].try_into().unwrap();
+        *cursor += 2;
+        Ok(match endianness {
+            Endianness::Big => i16::from_be_bytes(bytes) as i32,
+            Endianness::Little => i16::from_le_bytes(bytes) as i32,
+        })
+    } else {
+        let mut value = (nibble & 0x0f) as i32;
+        if value & 0x8 != 0 {
+            value -= 0x10;
+        }
+        Ok(value)
+    }
+}
+
+fn slice_at(
+    data: &[u8],
+    offset: u32,
+    size: u32,
+    section_file_offset: Option<usize>,
+) -> Result<&[u8]> {
+    let size = size as usize;
+    if size == 0 {
+        ensure!(
+            resolve_offset(offset, data.len(), section_file_offset).is_some(),
+            "offset outside of .mdebug section"
+        );
+        return Ok(&data[0..0]);
+    }
+    let Some(offset) = resolve_offset(offset, data.len(), section_file_offset) else {
+        bail!("offset outside of .mdebug section");
+    };
+    let end = offset.checked_add(size).context("range overflow")?;
+    ensure!(end <= data.len(), "range exceeds .mdebug size");
+    Ok(&data[offset..end])
+}
+
+fn resolve_offset(
+    offset: u32,
+    data_len: usize,
+    section_file_offset: Option<usize>,
+) -> Option<usize> {
+    let offset = offset as usize;
+    if offset <= data_len {
+        Some(offset)
+    } else if let Some(file_offset) = section_file_offset {
+        offset.checked_sub(file_offset).filter(|rel| *rel <= data_len)
+    } else {
+        None
+    }
+}
+
+#[derive(Clone, Copy)]
+struct Header {
+    cb_line_offset: u32,
+    cb_pd_offset: u32,
+    cb_sym_offset: u32,
+    cb_fd_offset: u32,
+    isym_max: u32,
+    ifd_max: u32,
+}
+
+impl Header {
+    fn parse(data: &[u8], endianness: Endianness) -> Result<Self> {
+        ensure!(HDRR_SIZE <= data.len(), ".mdebug header truncated");
+        let mut cursor = 0;
+        let magic = read_u16(data, &mut cursor, endianness)?;
+        let _vstamp = read_u16(data, &mut cursor, endianness)?;
+        ensure!(magic == 0x7009, "unexpected .mdebug magic: {magic:#x}");
+        let _iline_max = read_u32(data, &mut cursor, endianness)?;
+        let _cb_line = read_u32(data, &mut cursor, endianness)?;
+        let cb_line_offset = read_u32(data, &mut cursor, endianness)?;
+        let _idn_max = read_u32(data, &mut cursor, endianness)?;
+        let _cb_dn_offset = read_u32(data, &mut cursor, endianness)?;
+        let _ipd_max = read_u32(data, &mut cursor, endianness)?;
+        let cb_pd_offset = read_u32(data, &mut cursor, endianness)?;
+        let isym_max = read_u32(data, &mut cursor, endianness)?;
+        let cb_sym_offset = read_u32(data, &mut cursor, endianness)?;
+        let _iopt_max = read_u32(data, &mut cursor, endianness)?;
+        let _cb_opt_offset = read_u32(data, &mut cursor, endianness)?;
+        let _iaux_max = read_u32(data, &mut cursor, endianness)?;
+        let _cb_aux_offset = read_u32(data, &mut cursor, endianness)?;
+        let _iss_max = read_u32(data, &mut cursor, endianness)?;
+        let _cb_ss_offset = read_u32(data, &mut cursor, endianness)?;
+        let _iss_ext_max = read_u32(data, &mut cursor, endianness)?;
+        let _cb_ss_ext_offset = read_u32(data, &mut cursor, endianness)?;
+        let ifd_max = read_u32(data, &mut cursor, endianness)?;
+        let cb_fd_offset = read_u32(data, &mut cursor, endianness)?;
+        let _crfd = read_u32(data, &mut cursor, endianness)?;
+        let _cb_rfd_offset = read_u32(data, &mut cursor, endianness)?;
+        let _iext_max = read_u32(data, &mut cursor, endianness)?;
+        let _cb_ext_offset = read_u32(data, &mut cursor, endianness)?;
+
+        Ok(Header { cb_line_offset, cb_pd_offset, cb_sym_offset, cb_fd_offset, isym_max, ifd_max })
+    }
+}
+
+#[derive(Clone, Copy)]
+struct FileDescriptor {
+    adr: u32,
+    isym_base: u32,
+    csym: u32,
+    ipd_first: u16,
+    cpd: u16,
+    cb_line_offset: u32,
+    cb_line: u32,
+}
+
+impl FileDescriptor {
+    fn parse(data: &[u8], endianness: Endianness) -> Result<Self> {
+        ensure!(data.len() >= FDR_SIZE, "FDR truncated");
+        let mut cursor = 0;
+        let adr = read_u32(data, &mut cursor, endianness)?;
+        let _rss = read_u32(data, &mut cursor, endianness)?;
+        let _iss_base = read_u32(data, &mut cursor, endianness)?;
+        let _cb_ss = read_u32(data, &mut cursor, endianness)?;
+        let isym_base = read_u32(data, &mut cursor, endianness)?;
+        let csym = read_u32(data, &mut cursor, endianness)?;
+        let _iline_base = read_u32(data, &mut cursor, endianness)?;
+        let _cline = read_u32(data, &mut cursor, endianness)?;
+        let _iopt_base = read_u32(data, &mut cursor, endianness)?;
+        let _copt = read_u32(data, &mut cursor, endianness)?;
+        let ipd_first = read_u16(data, &mut cursor, endianness)?;
+        let cpd = read_u16(data, &mut cursor, endianness)?;
+        let _iaux_base = read_u32(data, &mut cursor, endianness)?;
+        let _caux = read_u32(data, &mut cursor, endianness)?;
+        let _rfd_base = read_u32(data, &mut cursor, endianness)?;
+        let _crfd = read_u32(data, &mut cursor, endianness)?;
+        let _bits = read_u32(data, &mut cursor, endianness)?;
+        let cb_line_offset = read_u32(data, &mut cursor, endianness)?;
+        let cb_line = read_u32(data, &mut cursor, endianness)?;
+
+        Ok(FileDescriptor { adr, isym_base, csym, ipd_first, cpd, cb_line_offset, cb_line })
+    }
+}
+
+#[derive(Clone, Copy)]
+struct ProcDescriptor {
+    addr: u32,
+    isym: u32,
+    ln_low: i32,
+    cb_line_offset: u32,
+}
+
+impl ProcDescriptor {
+    fn parse(data: &[u8], endianness: Endianness) -> Result<Self> {
+        ensure!(data.len() >= PDR_SIZE, "PDR truncated");
+        let mut cursor = 0;
+        let addr = read_u32(data, &mut cursor, endianness)?;
+        let isym = read_u32(data, &mut cursor, endianness)?;
+        let _iline = read_u32(data, &mut cursor, endianness)?;
+        let _regmask = read_u32(data, &mut cursor, endianness)?;
+        let _regoffset = read_u32(data, &mut cursor, endianness)?;
+        let _iopt = read_u32(data, &mut cursor, endianness)?;
+        let _fregmask = read_u32(data, &mut cursor, endianness)?;
+        let _fregoffset = read_u32(data, &mut cursor, endianness)?;
+        let _frameoffset = read_u32(data, &mut cursor, endianness)?;
+        let _framereg = read_u16(data, &mut cursor, endianness)?;
+        let _pcreg = read_u16(data, &mut cursor, endianness)?;
+        let ln_low = read_i32(data, &mut cursor, endianness)?;
+        let _ln_high = read_i32(data, &mut cursor, endianness)?;
+        let cb_line_offset = read_u32(data, &mut cursor, endianness)?;
+
+        Ok(ProcDescriptor { addr, isym, ln_low, cb_line_offset })
+    }
+}
+
+#[derive(Clone, Copy)]
+struct SymbolEntry {
+    value: u32,
+    st: u8,
+    index: u32,
+}
+
+fn parse_symbols(data: &[u8], endianness: Endianness) -> Result<Vec<SymbolEntry>> {
+    ensure!(data.len().is_multiple_of(SYMR_SIZE), "symbol table misaligned");
+    let mut symbols = Vec::with_capacity(data.len() / SYMR_SIZE);
+    let mut cursor = 0;
+    while cursor + SYMR_SIZE <= data.len() {
+        let _iss = read_u32(data, &mut cursor, endianness)?;
+        let value = read_u32(data, &mut cursor, endianness)?;
+        let bits = read_u32(data, &mut cursor, endianness)?;
+        let (st, index) = match endianness {
+            Endianness::Big => (((bits >> 26) & 0x3f) as u8, bits & 0x000f_ffff),
+            Endianness::Little => (((bits & 0x3f) as u8), (bits >> 12) & 0x000f_ffff),
+        };
+        symbols.push(SymbolEntry { value, st, index });
+    }
+    Ok(symbols)
+}
+
+fn read_u16(data: &[u8], cursor: &mut usize, endianness: Endianness) -> Result<u16> {
+    ensure!(*cursor + 2 <= data.len(), "unexpected EOF while reading u16");
+    let bytes: [u8; 2] = data[*cursor..*cursor + 2].try_into().unwrap();
+    *cursor += 2;
+    Ok(match endianness {
+        Endianness::Big => u16::from_be_bytes(bytes),
+        Endianness::Little => u16::from_le_bytes(bytes),
+    })
+}
+
+fn read_u32(data: &[u8], cursor: &mut usize, endianness: Endianness) -> Result<u32> {
+    ensure!(*cursor + 4 <= data.len(), "unexpected EOF while reading u32");
+    let bytes: [u8; 4] = data[*cursor..*cursor + 4].try_into().unwrap();
+    *cursor += 4;
+    Ok(match endianness {
+        Endianness::Big => u32::from_be_bytes(bytes),
+        Endianness::Little => u32::from_le_bytes(bytes),
+    })
+}
+
+fn read_i32(data: &[u8], cursor: &mut usize, endianness: Endianness) -> Result<i32> {
+    Ok(read_u32(data, cursor, endianness)? as i32)
+}

objdiff-core/src/obj/mod.rs

@@ -1,5 +1,6 @@
 #[cfg(feature = "dwarf")]
 mod dwarf2;
+mod mdebug;
 pub mod read;
 pub mod split_meta;
 

objdiff-core/src/obj/read.rs

@@ -654,6 +654,10 @@ fn parse_line_info(
         log::warn!("Failed to parse COFF line info: {e}");
     }
 
+    if let Err(e) = super::mdebug::parse_line_info_mdebug(obj_file, sections) {
+        log::warn!("Failed to parse MIPS mdebug line info: {e}");
+    }
+
     Ok(())
 }
 

objdiff-core/tests/arch_mips.rs

@@ -62,3 +62,21 @@ fn filter_non_matching() {
     .unwrap();
     insta::assert_debug_snapshot!(obj.symbols);
 }
+
+#[test]
+#[cfg(feature = "mips")]
+fn ido_mdebug_line_numbers() {
+    let diff_config = diff::DiffObjConfig::default();
+    let obj = obj::read::parse(
+        include_object!("data/mips/ido_lines_example.o"),
+        &diff_config,
+        diff::DiffSide::Base,
+    )
+    .unwrap();
+
+    let text_section = obj.sections.iter().find(|s| s.name == ".text").unwrap();
+    assert_eq!(text_section.line_info.get(&0), Some(&6));
+    assert_eq!(text_section.line_info.get(&12), Some(&7));
+    assert_eq!(text_section.line_info.get(&56), Some(&9));
+    assert_eq!(text_section.line_info.len(), 66);
+}