Relocation improvements for .eh_frame

This is necessary to handle LSDA references in the future once unwinding
is supported.

Author: bjorn3

src/debuginfo/emit.rs

@@ -81,13 +81,36 @@ impl WriterRelocate {
     /// Perform the collected relocations to be usable for JIT usage.
     #[cfg(all(feature = "jit", not(windows)))]
     pub(super) fn relocate_for_jit(mut self, jit_module: &cranelift_jit::JITModule) -> Vec<u8> {
+        use cranelift_module::Module;
+
         for reloc in self.relocs.drain(..) {
             match reloc.name {
                 super::DebugRelocName::Section(_) => unreachable!(),
                 super::DebugRelocName::Symbol(sym) => {
-                    let addr = jit_module.get_finalized_function(
-                        cranelift_module::FuncId::from_u32(sym.try_into().unwrap()),
-                    );
+                    let addr = if sym & 1 << 31 == 0 {
+                        let func_id = FuncId::from_u32(sym.try_into().unwrap());
+                        // FIXME make JITModule::get_address public and use it here instead.
+                        // HACK rust_eh_personality is likely not defined in the same crate,
+                        // so get_finalized_function won't work. Use the rust_eh_personality
+                        // of cg_clif itself, which is likely ABI compatible.
+                        if jit_module.declarations().get_function_decl(func_id).name.as_deref()
+                            == Some("rust_eh_personality")
+                        {
+                            extern "C" {
+                                fn rust_eh_personality() -> !;
+                            }
+                            rust_eh_personality as *const u8
+                        } else {
+                            jit_module.get_finalized_function(func_id)
+                        }
+                    } else {
+                        jit_module
+                            .get_finalized_data(DataId::from_u32(
+                                u32::try_from(sym).unwrap() & !(1 << 31),
+                            ))
+                            .0
+                    };
+
                     let val = (addr as u64 as i64 + reloc.addend) as u64;
                     self.writer.write_udata_at(reloc.offset as usize, val, reloc.size).unwrap();
                 }
@@ -196,6 +219,16 @@ impl Writer for WriterRelocate {
                     });
                     self.write_udata(0, size)
                 }
+                gimli::DW_EH_PE_absptr => {
+                    self.relocs.push(DebugReloc {
+                        offset: self.len() as u32,
+                        size: size.into(),
+                        name: DebugRelocName::Symbol(symbol),
+                        addend,
+                        kind: object::RelocationKind::Absolute,
+                    });
+                    self.write_udata(0, size.into())
+                }
                 _ => Err(gimli::write::Error::UnsupportedPointerEncoding(eh_pe)),
             },
         }