Don't fail on line info parsing; use gimli::RelocateReader

Workaround for #228

objdiff-core/src/obj/dwarf2.rs

@@ -0,0 +1,106 @@
+use anyhow::{Context, Result};
+use object::{Object, ObjectSection};
+use typed_arena::Arena;
+
+use crate::obj::{Section, SectionKind};
+
+/// Parse line information from DWARF 2+ sections.
+pub(crate) fn parse_line_info_dwarf2(
+    obj_file: &object::File,
+    sections: &mut [Section],
+) -> Result<()> {
+    let arena_data = Arena::new();
+    let arena_relocations = Arena::new();
+    let endian = match obj_file.endianness() {
+        object::Endianness::Little => gimli::RunTimeEndian::Little,
+        object::Endianness::Big => gimli::RunTimeEndian::Big,
+    };
+    let dwarf = gimli::Dwarf::load(|id: gimli::SectionId| -> Result<_> {
+        load_file_section(id, obj_file, endian, &arena_data, &arena_relocations)
+    })
+    .context("loading DWARF sections")?;
+
+    let mut iter = dwarf.units();
+    if let Some(header) = iter.next().map_err(|e| gimli_error(e, "iterating over DWARF units"))? {
+        let unit = dwarf.unit(header).map_err(|e| gimli_error(e, "loading DWARF unit"))?;
+        if let Some(program) = unit.line_program.clone() {
+            let mut text_sections = sections.iter_mut().filter(|s| s.kind == SectionKind::Code);
+            let mut lines = text_sections.next().map(|section| &mut section.line_info);
+
+            let mut rows = program.rows();
+            while let Some((_header, row)) =
+                rows.next_row().map_err(|e| gimli_error(e, "loading program row"))?
+            {
+                if let (Some(line), Some(lines)) = (row.line(), &mut lines) {
+                    lines.insert(row.address(), line.get() as u32);
+                }
+                if row.end_sequence() {
+                    // The next row is the start of a new sequence, which means we must
+                    // advance to the next .text section.
+                    lines = text_sections.next().map(|section| &mut section.line_info);
+                }
+            }
+        }
+    }
+    if iter.next().map_err(|e| gimli_error(e, "checking for next unit"))?.is_some() {
+        log::warn!("Multiple units found in DWARF data, only processing the first");
+    }
+
+    Ok(())
+}
+
+#[derive(Debug, Default)]
+struct RelocationMap(object::read::RelocationMap);
+
+impl RelocationMap {
+    fn add(&mut self, file: &object::File, section: &object::Section) {
+        for (offset, relocation) in section.relocations() {
+            if let Err(e) = self.0.add(file, offset, relocation) {
+                log::error!(
+                    "Relocation error for section {} at offset 0x{:08x}: {}",
+                    section.name().unwrap(),
+                    offset,
+                    e
+                );
+            }
+        }
+    }
+}
+
+impl gimli::read::Relocate for &'_ RelocationMap {
+    fn relocate_address(&self, offset: usize, value: u64) -> gimli::Result<u64> {
+        Ok(self.0.relocate(offset as u64, value))
+    }
+
+    fn relocate_offset(&self, offset: usize, value: usize) -> gimli::Result<usize> {
+        <usize as gimli::ReaderOffset>::from_u64(self.0.relocate(offset as u64, value as u64))
+    }
+}
+
+type Relocate<'a, R> = gimli::RelocateReader<R, &'a RelocationMap>;
+
+fn load_file_section<'input, 'arena, Endian: gimli::Endianity>(
+    id: gimli::SectionId,
+    file: &object::File<'input>,
+    endian: Endian,
+    arena_data: &'arena Arena<alloc::borrow::Cow<'input, [u8]>>,
+    arena_relocations: &'arena Arena<RelocationMap>,
+) -> Result<Relocate<'arena, gimli::EndianSlice<'arena, Endian>>> {
+    let mut relocations = RelocationMap::default();
+    let data = match file.section_by_name(id.name()) {
+        Some(ref section) => {
+            relocations.add(file, section);
+            section.uncompressed_data()?
+        }
+        // Use a non-zero capacity so that `ReaderOffsetId`s are unique.
+        None => alloc::borrow::Cow::Owned(Vec::with_capacity(1)),
+    };
+    let data_ref = arena_data.alloc(data);
+    let section = gimli::EndianSlice::new(data_ref, endian);
+    let relocations = arena_relocations.alloc(relocations);
+    Ok(Relocate::new(section, relocations))
+}
+
+fn gimli_error(e: gimli::Error, context: &str) -> anyhow::Error {
+    anyhow::anyhow!("gimli error {context}: {e:?}")
+}