Object file support for s390x (bytecodealliance#2872)

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

cranelift/codegen/src/binemit/mod.rs

@@ -60,6 +60,8 @@ pub enum Reloc {
     Arm64Call,
     /// RISC-V call target
     RiscvCall,
+    /// s390x PC-relative 4-byte offset
+    S390xPCRel32Dbl,
 
     /// Elf x86_64 32 bit signed PC relative offset to two GOT entries for GD symbol.
     ElfX86_64TlsGd,
@@ -75,6 +77,7 @@ impl fmt::Display for Reloc {
         match *self {
             Self::Abs4 => write!(f, "Abs4"),
             Self::Abs8 => write!(f, "Abs8"),
+            Self::S390xPCRel32Dbl => write!(f, "PCRel32Dbl"),
             Self::X86PCRel4 => write!(f, "PCRel4"),
             Self::X86PCRelRodata4 => write!(f, "PCRelRodata4"),
             Self::X86CallPCRel4 => write!(f, "CallPCRel4"),

cranelift/jit/src/compiled_blob.rs

@@ -72,6 +72,15 @@ impl CompiledBlob {
                         write_unaligned(at as *mut i32, pcrel)
                     };
                 }
+                Reloc::S390xPCRel32Dbl => {
+                    let base = get_address(name);
+                    let what = unsafe { base.offset(isize::try_from(addend).unwrap()) };
+                    let pcrel = i32::try_from(((what as isize) - (at as isize)) >> 1).unwrap();
+                    #[cfg_attr(feature = "cargo-clippy", allow(clippy::cast_ptr_alignment))]
+                    unsafe {
+                        write_unaligned(at as *mut i32, pcrel)
+                    };
+                }
                 _ => unimplemented!(),
             }
         }

cranelift/src/disasm.rs

@@ -153,6 +153,11 @@ cfg_if! {
                     cs.set_skipdata(true).map_err(map_caperr)?;
                     cs
                 }
+                Architecture::S390x {..} => Capstone::new()
+                    .sysz()
+                    .mode(arch::sysz::ArchMode::Default)
+                    .build()
+                    .map_err(map_caperr)?,
                 _ => anyhow::bail!("Unknown ISA"),
             };
 

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"),
         }
     }