src/debuginfo/emit.rs

   1 //! Write the debuginfo into an object file.
   2
   3 use rustc_data_structures::fx::FxHashMap;
   4
   5 use gimli::write::{Address, AttributeValue, EndianVec, Result, Sections, Writer};
   6 use gimli::{RunTimeEndian, SectionId};
   7
   8 use crate::backend::WriteDebugInfo;
   9
  10 use super::DebugContext;
  11
  12 impl DebugContext<'_> {
  13     pub(crate) fn emit<P: WriteDebugInfo>(&mut self, product: &mut P) {
  14         let unit_range_list_id = self.dwarf.unit.ranges.add(self.unit_range_list.clone());
  15         let root = self.dwarf.unit.root();
  16         let root = self.dwarf.unit.get_mut(root);
  17         root.set(
  18             gimli::DW_AT_ranges,
  19             AttributeValue::RangeListRef(unit_range_list_id),
  20         );
  21
  22         let mut sections = Sections::new(WriterRelocate::new(self.endian));
  23         self.dwarf.write(&mut sections).unwrap();
  24
  25         let mut section_map = FxHashMap::default();
  26         let _: Result<()> = sections.for_each_mut(|id, section| {
  27             if !section.writer.slice().is_empty() {
  28                 let section_id = product.add_debug_section(id, section.writer.take());
  29                 section_map.insert(id, section_id);
  30             }
  31             Ok(())
  32         });
  33
  34         let _: Result<()> = sections.for_each(|id, section| {
  35             if let Some(section_id) = section_map.get(&id) {
  36                 for reloc in &section.relocs {
  37                     product.add_debug_reloc(&section_map, section_id, reloc);
  38                 }
  39             }
  40             Ok(())
  41         });
  42     }
  43 }
  44
  45 #[derive(Clone)]
  46 pub(crate) struct DebugReloc {
  47     pub(crate) offset: u32,
  48     pub(crate) size: u8,
  49     pub(crate) name: DebugRelocName,
  50     pub(crate) addend: i64,
  51     pub(crate) kind: object::RelocationKind,
  52 }
  53
  54 #[derive(Clone)]
  55 pub(crate) enum DebugRelocName {
  56     Section(SectionId),
  57     Symbol(usize),
  58 }
  59
  60 /// A [`Writer`] that collects all necessary relocations.
  61 #[derive(Clone)]
  62 pub(super) struct WriterRelocate {
  63     pub(super) relocs: Vec<DebugReloc>,
  64     pub(super) writer: EndianVec<RunTimeEndian>,
  65 }
  66
  67 impl WriterRelocate {
  68     pub(super) fn new(endian: RunTimeEndian) -> Self {
  69         WriterRelocate {
  70             relocs: Vec::new(),
  71             writer: EndianVec::new(endian),
  72         }
  73     }
  74
  75     /// Perform the collected relocations to be usable for JIT usage.
  76     #[cfg(feature = "jit")]
  77     pub(super) fn relocate_for_jit(
  78         mut self,
  79         jit_module: &cranelift_simplejit::SimpleJITModule,
  80     ) -> Vec<u8> {
  81         use std::convert::TryInto;
  82
  83         for reloc in self.relocs.drain(..) {
  84             match reloc.name {
  85                 super::DebugRelocName::Section(_) => unreachable!(),
  86                 super::DebugRelocName::Symbol(sym) => {
  87                     let addr = jit_module.get_finalized_function(
  88                         cranelift_module::FuncId::from_u32(sym.try_into().unwrap()),
  89                     );
  90                     let val = (addr as u64 as i64 + reloc.addend) as u64;
  91                     self.writer
  92                         .write_udata_at(reloc.offset as usize, val, reloc.size)
  93                         .unwrap();
  94                 }
  95             }
  96         }
  97         self.writer.into_vec()
  98     }
  99 }
 100
 101 impl Writer for WriterRelocate {
 102     type Endian = RunTimeEndian;
 103
 104     fn endian(&self) -> Self::Endian {
 105         self.writer.endian()
 106     }
 107
 108     fn len(&self) -> usize {
 109         self.writer.len()
 110     }
 111
 112     fn write(&mut self, bytes: &[u8]) -> Result<()> {
 113         self.writer.write(bytes)
 114     }
 115
 116     fn write_at(&mut self, offset: usize, bytes: &[u8]) -> Result<()> {
 117         self.writer.write_at(offset, bytes)
 118     }
 119
 120     fn write_address(&mut self, address: Address, size: u8) -> Result<()> {
 121         match address {
 122             Address::Constant(val) => self.write_udata(val, size),
 123             Address::Symbol { symbol, addend } => {
 124                 let offset = self.len() as u64;
 125                 self.relocs.push(DebugReloc {
 126                     offset: offset as u32,
 127                     size,
 128                     name: DebugRelocName::Symbol(symbol),
 129                     addend: addend as i64,
 130                     kind: object::RelocationKind::Absolute,
 131                 });
 132                 self.write_udata(0, size)
 133             }
 134         }
 135     }
 136
 137     fn write_offset(&mut self, val: usize, section: SectionId, size: u8) -> Result<()> {
 138         let offset = self.len() as u32;
 139         self.relocs.push(DebugReloc {
 140             offset,
 141             size,
 142             name: DebugRelocName::Section(section),
 143             addend: val as i64,
 144             kind: object::RelocationKind::Absolute,
 145         });
 146         self.write_udata(0, size)
 147     }
 148
 149     fn write_offset_at(
 150         &mut self,
 151         offset: usize,
 152         val: usize,
 153         section: SectionId,
 154         size: u8,
 155     ) -> Result<()> {
 156         self.relocs.push(DebugReloc {
 157             offset: offset as u32,
 158             size,
 159             name: DebugRelocName::Section(section),
 160             addend: val as i64,
 161             kind: object::RelocationKind::Absolute,
 162         });
 163         self.write_udata_at(offset, 0, size)
 164     }
 165
 166     fn write_eh_pointer(&mut self, address: Address, eh_pe: gimli::DwEhPe, size: u8) -> Result<()> {
 167         match address {
 168             // Address::Constant arm copied from gimli
 169             Address::Constant(val) => {
 170                 // Indirect doesn't matter here.
 171                 let val = match eh_pe.application() {
 172                     gimli::DW_EH_PE_absptr => val,
 173                     gimli::DW_EH_PE_pcrel => {
 174                         // TODO: better handling of sign
 175                         let offset = self.len() as u64;
 176                         offset.wrapping_sub(val)
 177                     }
 178                     _ => {
 179                         return Err(gimli::write::Error::UnsupportedPointerEncoding(eh_pe));
 180                     }
 181                 };
 182                 self.write_eh_pointer_data(val, eh_pe.format(), size)
 183             }
 184             Address::Symbol { symbol, addend } => match eh_pe.application() {
 185                 gimli::DW_EH_PE_pcrel => {
 186                     let size = match eh_pe.format() {
 187                         gimli::DW_EH_PE_sdata4 => 4,
 188                         _ => return Err(gimli::write::Error::UnsupportedPointerEncoding(eh_pe)),
 189                     };
 190                     self.relocs.push(DebugReloc {
 191                         offset: self.len() as u32,
 192                         size,
 193                         name: DebugRelocName::Symbol(symbol),
 194                         addend,
 195                         kind: object::RelocationKind::Relative,
 196                     });
 197                     self.write_udata(0, size)
 198                 }
 199                 _ => Err(gimli::write::Error::UnsupportedPointerEncoding(eh_pe)),
 200             },
 201         }
 202     }
 203 }