Cranelift: Module data apis should allow specifying the object file section #1640

cranelift/module/src/data_context.rs

@@ -46,6 +46,8 @@ pub struct DataDescription {
     pub function_relocs: Vec<(CodeOffset, ir::FuncRef)>,
     /// Data addresses to write at specified offsets.
     pub data_relocs: Vec<(CodeOffset, ir::GlobalValue, Addend)>,
+    /// Object file section
+    pub section: Option<(std::string::String, std::string::String)>
 }
 
 /// This is to data objects what cranelift_codegen::Context is to functions.
@@ -63,6 +65,7 @@ impl DataContext {
                 data_decls: PrimaryMap::new(),
                 function_relocs: vec![],
                 data_relocs: vec![],
+                section: None
             },
         }
     }
@@ -90,6 +93,11 @@ impl DataContext {
         self.description.init = Init::Bytes { contents };
     }
 
+    /// Override the segment/section for data, only supported on Object backend
+    pub fn set_section(&mut self, seg: &str, sec: &str) {
+        self.description.section = Some((std::string::String::from(seg), std::string::String::from(sec)))
+    }
+
     /// Declare an external function import.
     ///
     /// Users of the `Module` API generally should call

cranelift/object/src/backend.rs

@@ -234,6 +234,7 @@ impl Backend for ObjectBackend {
             ref data_decls,
             ref function_relocs,
             ref data_relocs,
+            section: ref datasection
         } = data_ctx.description();
 
         let reloc_size = match self.isa.triple().pointer_width().unwrap() {
@@ -264,6 +265,8 @@ impl Backend for ObjectBackend {
         }
 
         let symbol = self.data_objects[data_id].unwrap();
+        let section = 
+            if datasection.is_none() {
                 let section_kind = if let Init::Zeros { .. } = *init {
                     if tls {
                         StandardSection::UninitializedTls
@@ -279,7 +282,13 @@ impl Backend for ObjectBackend {
                 } else {
                     StandardSection::ReadOnlyDataWithRel
                 };
-        let section = self.object.section_id(section_kind);
+                self.object.section_id(section_kind)
+            } else {
+                let (seg, sec) = &datasection.as_ref().unwrap();
+                self.object.add_section(seg.clone().into_bytes(), sec.clone().into_bytes(), 
+                    if writable { SectionKind::Data } else { SectionKind::ReadOnlyData }
+                )
+            };
 
         let align = u64::from(align.unwrap_or(1));
         let offset = match *init {