Merge pull request #982 from bjorn3/backtrace_support

Implement .eh_frame writing

Cargo.toml

@@ -9,7 +9,7 @@ crate-type = ["dylib"]
 
 [dependencies]
 # These have to be in sync with each other
-cranelift-codegen = { git = "https://github.com/bytecodealliance/wasmtime/" }
+cranelift-codegen = { git = "https://github.com/bytecodealliance/wasmtime/", features = ["unwind"] }
 cranelift-frontend = { git = "https://github.com/bytecodealliance/wasmtime/" }
 cranelift-module = { git = "https://github.com/bytecodealliance/wasmtime/" }
 cranelift-object = { git = "https://github.com/bytecodealliance/wasmtime/" }

src/backend.rs

@@ -39,7 +39,7 @@ impl WriteMetadata for object::write::Object {
 }
 
 pub(crate) trait WriteDebugInfo {
-    type SectionId;
+    type SectionId: Copy;
 
     fn add_debug_section(&mut self, name: SectionId, data: Vec<u8>) -> Self::SectionId;
     fn add_debug_reloc(

src/debuginfo/emit.rs

@@ -1,6 +1,6 @@
 use rustc_data_structures::fx::FxHashMap;
 
-use gimli::write::{Address, AttributeValue, EndianVec, Result, Sections, Writer};
+use gimli::write::{Address, AttributeValue, EhFrame, EndianVec, Result, Sections, Writer, Section};
 use gimli::{RunTimeEndian, SectionId};
 
 use crate::backend::WriteDebugInfo;
@@ -20,6 +20,9 @@ impl DebugContext<'_> {
         let mut sections = Sections::new(WriterRelocate::new(self));
         self.dwarf.write(&mut sections).unwrap();
 
+        let mut eh_frame = EhFrame::from(WriterRelocate::new(self));
+        self.frame_table.write_eh_frame(&mut eh_frame).unwrap();
+
         let mut section_map = FxHashMap::default();
         let _: Result<()> = sections.for_each_mut(|id, section| {
             if !section.writer.slice().is_empty() {
@@ -37,6 +40,16 @@ impl DebugContext<'_> {
             }
             Ok(())
         });
+
+        if !eh_frame.0.writer.slice().is_empty() {
+            let id = eh_frame.id();
+            let section_id = product.add_debug_section(id, eh_frame.0.writer.into_vec());
+            section_map.insert(id, section_id);
+
+            for reloc in &eh_frame.0.relocs {
+                product.add_debug_reloc(&section_map, &self.symbols, &section_id, reloc);
+            }
+        }
     }
 }
 

src/debuginfo/mod.rs

@@ -1,5 +1,6 @@
 mod emit;
 mod line_info;
+mod unwind;
 
 use crate::prelude::*;
 
@@ -10,8 +11,8 @@ use cranelift_codegen::isa::TargetIsa;
 use cranelift_codegen::ValueLocRange;
 
 use gimli::write::{
-    self, Address, AttributeValue, DwarfUnit, Expression, LineProgram, LineString, Location,
+    self, Address, AttributeValue, CieId, DwarfUnit, Expression, FrameTable, LineProgram,
-    LocationList, Range, RangeList, UnitEntryId, Writer,
+    LineString, Location, LocationList, Range, RangeList, UnitEntryId, Writer,
 };
 use gimli::{Encoding, Format, LineEncoding, RunTimeEndian, X86_64};
 
@@ -34,13 +35,15 @@ pub(crate) struct DebugContext<'tcx> {
 
     dwarf: DwarfUnit,
     unit_range_list: RangeList,
+    frame_table: FrameTable,
 
+    cie: CieId,
     clif_types: FxHashMap<Type, UnitEntryId>,
     types: FxHashMap<Ty<'tcx>, UnitEntryId>,
 }
 
 impl<'tcx> DebugContext<'tcx> {
-    pub(crate) fn new(tcx: TyCtxt<'tcx>, address_size: u8) -> Self {
+    pub(crate) fn new(tcx: TyCtxt<'tcx>, isa: &dyn TargetIsa) -> Self {
         let encoding = Encoding {
             format: Format::Dwarf32,
             // TODO: this should be configurable
@@ -53,7 +56,7 @@ impl<'tcx> DebugContext<'tcx> {
                 // support it.
                 4
             },
-            address_size,
+            address_size: isa.frontend_config().pointer_bytes(),
         };
 
         let mut dwarf = DwarfUnit::new(encoding);
@@ -108,6 +111,9 @@ impl<'tcx> DebugContext<'tcx> {
             );
         }
 
+        let mut frame_table = FrameTable::default();
+        let cie = frame_table.add_cie(isa.create_systemv_cie().expect("SystemV unwind info CIE"));
+
         DebugContext {
             tcx,
 
@@ -116,7 +122,9 @@ impl<'tcx> DebugContext<'tcx> {
 
             dwarf,
             unit_range_list: RangeList(Vec::new()),
+            frame_table,
 
+            cie,
             clif_types: FxHashMap::default(),
             types: FxHashMap::default(),
         }
@@ -312,6 +320,8 @@ impl<'a, 'tcx> FunctionDebugContext<'a, 'tcx> {
         source_info_set: &indexmap::IndexSet<SourceInfo>,
         local_map: FxHashMap<mir::Local, CPlace<'tcx>>,
     ) {
+        self.create_unwind_info(context, isa);
+
         let end = self.create_debug_lines(context, isa, source_info_set);
 
         self.debug_context

src/debuginfo/unwind.rs

@@ -0,0 +1,31 @@
+use crate::prelude::*;
+
+use cranelift_codegen::isa::unwind::UnwindInfo;
+
+use gimli::write::Address;
+
+impl<'a, 'tcx> FunctionDebugContext<'a, 'tcx> {
+    pub(super) fn create_unwind_info(
+        &mut self,
+        context: &Context,
+        isa: &dyn cranelift_codegen::isa::TargetIsa,
+    ) {
+        let unwind_info = if let Some(unwind_info) = context.create_unwind_info(isa).unwrap() {
+            unwind_info
+        } else {
+            return;
+        };
+
+        match unwind_info {
+            UnwindInfo::SystemV(unwind_info) => {
+                self.debug_context.frame_table.add_fde(self.debug_context.cie, unwind_info.to_fde(Address::Symbol {
+                    symbol: self.symbol,
+                    addend: 0,
+                }));
+            },
+            UnwindInfo::WindowsX64(_) => {
+                // FIXME implement this
+            }
+        }
+    }
+}

src/driver/aot.rs

@@ -120,7 +120,7 @@ fn module_codegen(tcx: TyCtxt<'_>, cgu_name: rustc_span::Symbol) -> ModuleCodege
     let mut debug = if tcx.sess.opts.debuginfo != DebugInfo::None {
         let debug = DebugContext::new(
             tcx,
-            module.target_config().pointer_type().bytes() as u8,
+            module.isa(),
         );
         Some(debug)
     } else {