1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162

pub use crate::transform::transform_dwarf;
use gimli::write::{Address, Dwarf, EndianVec, FrameTable, Result, Sections, Writer};
use gimli::{RunTimeEndian, SectionId};
use wasmtime_environ::entity::EntityRef;
use wasmtime_environ::ir::Endianness;
use wasmtime_environ::isa::{unwind::UnwindInfo, TargetIsa};
use wasmtime_environ::{CompiledFunctions, DebugInfoData, ModuleMemoryOffset};

#[derive(Clone)]
pub enum DwarfSectionRelocTarget {
    Func(usize),
    Section(&'static str),
}

#[derive(Clone)]
pub struct DwarfSectionReloc {
    pub target: DwarfSectionRelocTarget,
    pub offset: u32,
    pub addend: i32,
    pub size: u8,
}

pub struct DwarfSection {
    pub name: &'static str,
    pub body: Vec<u8>,
    pub relocs: Vec<DwarfSectionReloc>,
}

fn emit_dwarf_sections(
    isa: &dyn TargetIsa,
    mut dwarf: Dwarf,
    frames: Option<FrameTable>,
) -> anyhow::Result<Vec<DwarfSection>> {
    let endian = match isa.endianness() {
        Endianness::Little => RunTimeEndian::Little,
        Endianness::Big => RunTimeEndian::Big,
    };
    let writer = WriterRelocate {
        relocs: Vec::new(),
        writer: EndianVec::new(endian),
    };
    let mut sections = Sections::new(writer);
    dwarf.write(&mut sections)?;
    if let Some(frames) = frames {
        frames.write_debug_frame(&mut sections.debug_frame)?;
    }

    let mut result = Vec::new();
    sections.for_each_mut(|id, s| -> anyhow::Result<()> {
        let name = id.name();
        let body = s.writer.take();
        let mut relocs = vec![];
        ::std::mem::swap(&mut relocs, &mut s.relocs);
        result.push(DwarfSection { name, body, relocs });
        Ok(())
    })?;

    Ok(result)
}

#[derive(Clone)]
pub struct WriterRelocate {
    relocs: Vec<DwarfSectionReloc>,
    writer: EndianVec<RunTimeEndian>,
}

impl Writer for WriterRelocate {
    type Endian = RunTimeEndian;

    fn endian(&self) -> Self::Endian {
        self.writer.endian()
    }

    fn len(&self) -> usize {
        self.writer.len()
    }

    fn write(&mut self, bytes: &[u8]) -> Result<()> {
        self.writer.write(bytes)
    }

    fn write_at(&mut self, offset: usize, bytes: &[u8]) -> Result<()> {
        self.writer.write_at(offset, bytes)
    }

    fn write_address(&mut self, address: Address, size: u8) -> Result<()> {
        match address {
            Address::Constant(val) => self.write_udata(val, size),
            Address::Symbol { symbol, addend } => {
                let offset = self.len() as u32;
                self.relocs.push(DwarfSectionReloc {
                    target: DwarfSectionRelocTarget::Func(symbol),
                    offset,
                    size,
                    addend: addend as i32,
                });
                self.write_udata(addend as u64, size)
            }
        }
    }

    fn write_offset(&mut self, val: usize, section: SectionId, size: u8) -> Result<()> {
        let offset = self.len() as u32;
        let target = DwarfSectionRelocTarget::Section(section.name());
        self.relocs.push(DwarfSectionReloc {
            target,
            offset,
            size,
            addend: val as i32,
        });
        self.write_udata(val as u64, size)
    }

    fn write_offset_at(
        &mut self,
        offset: usize,
        val: usize,
        section: SectionId,
        size: u8,
    ) -> Result<()> {
        let target = DwarfSectionRelocTarget::Section(section.name());
        self.relocs.push(DwarfSectionReloc {
            target,
            offset: offset as u32,
            size,
            addend: val as i32,
        });
        self.write_udata_at(offset, val as u64, size)
    }
}

fn create_frame_table<'a>(isa: &dyn TargetIsa, funcs: &CompiledFunctions) -> Option<FrameTable> {
    let mut table = FrameTable::default();

    let cie_id = table.add_cie(isa.create_systemv_cie()?);

    for (i, f) in funcs {
        if let Some(UnwindInfo::SystemV(info)) = &f.unwind_info {
            table.add_fde(
                cie_id,
                info.to_fde(Address::Symbol {
                    symbol: i.index(),
                    addend: 0,
                }),
            );
        }
    }

    Some(table)
}

pub fn emit_dwarf<'a>(
    isa: &dyn TargetIsa,
    debuginfo_data: &DebugInfoData,
    funcs: &CompiledFunctions,
    memory_offset: &ModuleMemoryOffset,
) -> anyhow::Result<Vec<DwarfSection>> {
    let dwarf = transform_dwarf(isa, debuginfo_data, funcs, memory_offset)?;
    let frame_table = create_frame_table(isa, funcs);
    let sections = emit_dwarf_sections(isa, dwarf, frame_table)?;
    Ok(sections)
}