Merge pull request #1836 from carlokok/feature/object_file_section

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

cranelift/faerie/src/backend.rs

@@ -211,8 +211,17 @@ impl Backend for FaerieBackend {
             ref data_decls,
             ref function_relocs,
             ref data_relocs,
+            ref custom_segment_section,
         } = data_ctx.description();
 
+        if let Some((segment, section)) = custom_segment_section {
+            return Err(cranelift_module::ModuleError::Backend(anyhow::anyhow!(
+                "Custom section not supported by cranelift-faerie: `{}:{}`",
+                segment,
+                section
+            )));
+        }
+
         for &(offset, id) in function_relocs {
             let to = &namespace.get_function_decl(&function_decls[id]).name;
             self.artifact

cranelift/module/src/data_context.rs

@@ -3,7 +3,9 @@
 use cranelift_codegen::binemit::{Addend, CodeOffset};
 use cranelift_codegen::entity::PrimaryMap;
 use cranelift_codegen::ir;
+use std::borrow::ToOwned;
 use std::boxed::Box;
+use std::string::String;
 use std::vec::Vec;
 
 /// This specifies how data is to be initialized.
@@ -46,6 +48,8 @@ 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 custom_segment_section: Option<(String, String)>,
 }
 
 /// This is to data objects what cranelift_codegen::Context is to functions.
@@ -63,6 +67,7 @@ impl DataContext {
                 data_decls: PrimaryMap::new(),
                 function_relocs: vec![],
                 data_relocs: vec![],
+                custom_segment_section: None,
             },
         }
     }
@@ -90,6 +95,11 @@ impl DataContext {
         self.description.init = Init::Bytes { contents };
     }
 
+    /// Override the segment/section for data, only supported on Object backend
+    pub fn set_segment_section(&mut self, seg: &str, sec: &str) {
+        self.description.custom_segment_section = Some((seg.to_owned(), sec.to_owned()))
+    }
+
     /// Declare an external function import.
     ///
     /// Users of the `Module` API generally should call

cranelift/object/src/backend.rs

@@ -271,6 +271,7 @@ impl Backend for ObjectBackend {
             ref data_decls,
             ref function_relocs,
             ref data_relocs,
+            ref custom_segment_section,
         } = data_ctx.description();
 
         let reloc_size = match self.isa.triple().pointer_width().unwrap() {
@@ -301,6 +302,7 @@ impl Backend for ObjectBackend {
         }
 
         let symbol = self.data_objects[data_id].unwrap();
+        let section = if custom_segment_section.is_none() {
             let section_kind = if let Init::Zeros { .. } = *init {
                 if tls {
                     StandardSection::UninitializedTls
@@ -316,7 +318,24 @@ impl Backend for ObjectBackend {
             } else {
                 StandardSection::ReadOnlyDataWithRel
             };
-        let section = self.object.section_id(section_kind);
+            self.object.section_id(section_kind)
+        } else {
+            if tls {
+                return Err(cranelift_module::ModuleError::Backend(anyhow::anyhow!(
+                    "Custom section not supported for TLS"
+                )));
+            }
+            let (seg, sec) = &custom_segment_section.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 {

cranelift/simplejit/src/backend.rs

@@ -361,6 +361,7 @@ impl<'simple_jit_backend> Backend for SimpleJITBackend {
             ref data_decls,
             ref function_relocs,
             ref data_relocs,
+            custom_segment_section: _,
         } = data.description();
 
         let size = init.size();