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).

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"),
             };