Fix __eh_frame for AArch64 on macOS

The relocations must use symbols (not sections), and the relative relocation
needs ARM64_RELOC_SUBTRACTOR.

The section must be in __TEXT rather than __DWARF, which is handled by
using StandardSection::EhFrame. This also changes the section type
for ELF x86-64.

Author: philipc

src/debuginfo/emit.rs

@@ -43,7 +43,7 @@ impl DebugContext {
         let _: Result<()> = sections.for_each(|id, section| {
             if let Some(section_id) = section_map.get(&id) {
                 for reloc in &section.relocs {
-                    product.add_debug_reloc(&section_map, section_id, reloc);
+                    product.add_debug_reloc(&section_map, section_id, reloc, false);
                 }
             }
             Ok(())

src/debuginfo/object.rs

@@ -1,7 +1,7 @@
 use cranelift_module::{DataId, FuncId};
 use cranelift_object::ObjectProduct;
 use gimli::SectionId;
-use object::write::{Relocation, StandardSegment};
+use object::write::{Relocation, StandardSection, StandardSegment};
 use object::{RelocationEncoding, RelocationFlags, SectionKind};
 use rustc_data_structures::fx::FxHashMap;
 
@@ -16,6 +16,7 @@ pub(super) trait WriteDebugInfo {
         section_map: &FxHashMap<SectionId, Self::SectionId>,
         from: &Self::SectionId,
         reloc: &DebugReloc,
+        use_section_symbol: bool,
     );
 }
 
@@ -27,29 +28,31 @@ impl WriteDebugInfo for ObjectProduct {
         id: SectionId,
         data: Vec<u8>,
     ) -> (object::write::SectionId, object::write::SymbolId) {
-        let name = if self.object.format() == object::BinaryFormat::MachO {
-            id.name().replace('.', "__") // machO expects __debug_info instead of .debug_info
+        let (section_id, align);
+        if id == SectionId::EhFrame {
+            section_id = self.object.section_id(StandardSection::EhFrame);
+            align = 8;
         } else {
-            id.name().to_string()
-        }
-        .into_bytes();
-
-        let segment = self.object.segment_name(StandardSegment::Debug).to_vec();
-        // FIXME use SHT_X86_64_UNWIND for .eh_frame
-        let section_id = self.object.add_section(
-            segment,
-            name,
-            if id == SectionId::DebugStr || id == SectionId::DebugLineStr {
-                SectionKind::DebugString
-            } else if id == SectionId::EhFrame {
-                SectionKind::ReadOnlyData
+            let name = if self.object.format() == object::BinaryFormat::MachO {
+                id.name().replace('.', "__") // machO expects __debug_info instead of .debug_info
             } else {
-                SectionKind::Debug
-            },
-        );
-        self.object
-            .section_mut(section_id)
-            .set_data(data, if id == SectionId::EhFrame { 8 } else { 1 });
+                id.name().to_string()
+            }
+            .into_bytes();
+
+            let segment = self.object.segment_name(StandardSegment::Debug).to_vec();
+            section_id = self.object.add_section(
+                segment,
+                name,
+                if id == SectionId::DebugStr || id == SectionId::DebugLineStr {
+                    SectionKind::DebugString
+                } else {
+                    SectionKind::Debug
+                },
+            );
+            align = 1;
+        }
+        self.object.section_mut(section_id).set_data(data, align);
         let symbol_id = self.object.section_symbol(section_id);
         (section_id, symbol_id)
     }
@@ -59,6 +62,7 @@ impl WriteDebugInfo for ObjectProduct {
         section_map: &FxHashMap<SectionId, Self::SectionId>,
         from: &Self::SectionId,
         reloc: &DebugReloc,
+        use_section_symbol: bool,
     ) {
         let (symbol, symbol_offset) = match reloc.name {
             DebugRelocName::Section(id) => (section_map.get(&id).unwrap().1, 0),
@@ -69,7 +73,11 @@ impl WriteDebugInfo for ObjectProduct {
                 } else {
                     self.data_symbol(DataId::from_u32(id & !(1 << 31)))
                 };
-                self.object.symbol_section_and_offset(symbol_id).unwrap_or((symbol_id, 0))
+                if use_section_symbol {
+                    self.object.symbol_section_and_offset(symbol_id).unwrap_or((symbol_id, 0))
+                } else {
+                    (symbol_id, 0)
+                }
             }
         };
         self.object

src/debuginfo/unwind.rs

@@ -120,13 +120,12 @@ impl UnwindContext {
         func_id: FuncId,
         context: &Context,
     ) {
-        if let target_lexicon::OperatingSystem::MacOSX { .. } =
-            module.isa().triple().operating_system
+        let triple = module.isa().triple();
+        if matches!(triple.operating_system, target_lexicon::OperatingSystem::MacOSX { .. })
+            && triple.architecture == target_lexicon::Architecture::X86_64
         {
             // The object crate doesn't currently support DW_GNU_EH_PE_absptr, which macOS
-            // requires for unwinding tables. In addition on arm64 it currently doesn't
-            // support 32bit relocations as we currently use for the unwinding table.
-            // See gimli-rs/object#415 and rust-lang/rustc_codegen_cranelift#1371
+            // requires for unwinding tables. See gimli-rs/object#415.
             return;
         }
 
@@ -250,8 +249,9 @@ impl UnwindContext {
             let mut section_map = FxHashMap::default();
             section_map.insert(id, section_id);
 
+            let use_section_symbol = product.object.format() != object::BinaryFormat::MachO;
             for reloc in &eh_frame.0.relocs {
-                product.add_debug_reloc(&section_map, &section_id, reloc);
+                product.add_debug_reloc(&section_map, &section_id, reloc, use_section_symbol);
             }
         }
     }