Object file support for s390x (#2872)

Add support for s390x binary format object files.  In particular,
add support for s390x ELF relocation types (currently only
S390xPCRel32Dbl).

crates/debug/src/lib.rs

@@ -120,6 +120,7 @@ fn ensure_supported_elf_format(bytes: &mut Vec<u8>) -> Result<Endianness, Error>
 
     match header.e_machine.get(e) {
         EM_X86_64 => (),
+        EM_S390 => (),
         machine => {
             bail!("Unsupported ELF target machine: {:x}", machine);
         }

crates/jit/src/link.rs

@@ -111,6 +111,19 @@ fn apply_reloc(
             );
             write_unaligned(reloc_address as *mut u32, reloc_delta_u64 as u32);
         },
+        #[cfg(target_pointer_width = "64")]
+        (RelocationKind::Relative, RelocationEncoding::S390xDbl, 32) => unsafe {
+            let reloc_address = body.add(offset as usize) as usize;
+            let reloc_addend = r.addend() as isize;
+            let reloc_delta_u64 = (target_func_address as u64)
+                .wrapping_sub(reloc_address as u64)
+                .wrapping_add(reloc_addend as u64);
+            assert!(
+                (reloc_delta_u64 as isize) >> 1 <= i32::max_value() as isize,
+                "relocation too large to fit in i32"
+            );
+            write_unaligned(reloc_address as *mut u32, (reloc_delta_u64 >> 1) as u32);
+        },
         (RelocationKind::Elf(elf::R_AARCH64_CALL26), RelocationEncoding::Generic, 32) => unsafe {
             let reloc_address = body.add(offset as usize) as usize;
             let reloc_addend = r.addend() as isize;

crates/obj/src/builder.rs

@@ -80,6 +80,7 @@ fn to_object_relocations<'a>(
                 RelocationEncoding::Generic,
                 32,
             ),
+            Reloc::S390xPCRel32Dbl => (RelocationKind::Relative, RelocationEncoding::S390xDbl, 32),
             other => unimplemented!("Unimplemented relocation {:?}", other),
         };
         Some(ObjectRelocation {
@@ -102,6 +103,7 @@ fn to_object_architecture(
         X86_64 => Architecture::X86_64,
         Arm(_) => Architecture::Arm,
         Aarch64(_) => Architecture::Aarch64,
+        S390x => Architecture::S390x,
         architecture => {
             anyhow::bail!("target architecture {:?} is unsupported", architecture,);
         }

crates/profiling/src/jitdump_linux.rs

@@ -241,6 +241,7 @@ impl State {
             Architecture::X86_32(_) => elf::EM_386 as u32,
             Architecture::Arm(_) => elf::EM_ARM as u32,
             Architecture::Aarch64(_) => elf::EM_AARCH64 as u32,
+            Architecture::S390x => elf::EM_S390 as u32,
             _ => unimplemented!("unrecognized architecture"),
         }
     }