Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 725 insertions, 0 deletions

diff --git a/third_party/rust/object/src/write/coff.rs b/third_party/rust/object/src/write/coff.rs
new file mode 100644
index 0000000000..d2f7ccc640
--- /dev/null
+++ b/third_party/rust/object/src/write/coff.rs
@@ -0,0 +1,725 @@
+use alloc::vec::Vec;
+use core::mem;
+
+use crate::endian::{LittleEndian as LE, U16Bytes, U32Bytes, U16, U32};
+use crate::pe as coff;
+use crate::write::string::*;
+use crate::write::util::*;
+use crate::write::*;
+
+#[derive(Default, Clone, Copy)]
+struct SectionOffsets {
+    offset: usize,
+    str_id: Option<StringId>,
+    reloc_offset: usize,
+    selection: u8,
+    associative_section: u16,
+}
+
+#[derive(Default, Clone, Copy)]
+struct SymbolOffsets {
+    index: usize,
+    str_id: Option<StringId>,
+    aux_count: u8,
+}
+
+/// Internal format to use for the `.drectve` section containing linker
+/// directives for symbol exports.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum CoffExportStyle {
+    /// MSVC format supported by link.exe and LLD.
+    Msvc,
+    /// Gnu format supported by GNU LD and LLD.
+    Gnu,
+}
+
+impl<'a> Object<'a> {
+    pub(crate) fn coff_section_info(
+        &self,
+        section: StandardSection,
+    ) -> (&'static [u8], &'static [u8], SectionKind, SectionFlags) {
+        match section {
+            StandardSection::Text => (&[], &b".text"[..], SectionKind::Text, SectionFlags::None),
+            StandardSection::Data => (&[], &b".data"[..], SectionKind::Data, SectionFlags::None),
+            StandardSection::ReadOnlyData
+            | StandardSection::ReadOnlyDataWithRel
+            | StandardSection::ReadOnlyString => (
+                &[],
+                &b".rdata"[..],
+                SectionKind::ReadOnlyData,
+                SectionFlags::None,
+            ),
+            StandardSection::UninitializedData => (
+                &[],
+                &b".bss"[..],
+                SectionKind::UninitializedData,
+                SectionFlags::None,
+            ),
+            // TLS sections are data sections with a special name.
+            StandardSection::Tls => (&[], &b".tls$"[..], SectionKind::Data, SectionFlags::None),
+            StandardSection::UninitializedTls => {
+                // Unsupported section.
+                (&[], &[], SectionKind::UninitializedTls, SectionFlags::None)
+            }
+            StandardSection::TlsVariables => {
+                // Unsupported section.
+                (&[], &[], SectionKind::TlsVariables, SectionFlags::None)
+            }
+            StandardSection::Common => {
+                // Unsupported section.
+                (&[], &[], SectionKind::Common, SectionFlags::None)
+            }
+            StandardSection::GnuProperty => {
+                // Unsupported section.
+                (&[], &[], SectionKind::Note, SectionFlags::None)
+            }
+        }
+    }
+
+    pub(crate) fn coff_subsection_name(&self, section: &[u8], value: &[u8]) -> Vec<u8> {
+        let mut name = section.to_vec();
+        name.push(b'$');
+        name.extend_from_slice(value);
+        name
+    }
+
+    pub(crate) fn coff_fixup_relocation(&mut self, mut relocation: &mut Relocation) -> i64 {
+        if relocation.kind == RelocationKind::GotRelative {
+            // Use a stub symbol for the relocation instead.
+            // This isn't really a GOT, but it's a similar purpose.
+            // TODO: need to handle DLL imports differently?
+            relocation.kind = RelocationKind::Relative;
+            relocation.symbol = self.coff_add_stub_symbol(relocation.symbol);
+        } else if relocation.kind == RelocationKind::PltRelative {
+            // Windows doesn't need a separate relocation type for
+            // references to functions in import libraries.
+            // For convenience, treat this the same as Relative.
+            relocation.kind = RelocationKind::Relative;
+        }
+
+        let constant = match self.architecture {
+            Architecture::I386 | Architecture::Arm | Architecture::Aarch64 => match relocation.kind
+            {
+                RelocationKind::Relative => {
+                    // IMAGE_REL_I386_REL32, IMAGE_REL_ARM_REL32, IMAGE_REL_ARM64_REL32
+                    relocation.addend + 4
+                }
+                _ => relocation.addend,
+            },
+            Architecture::X86_64 => match relocation.kind {
+                RelocationKind::Relative => {
+                    // IMAGE_REL_AMD64_REL32 through to IMAGE_REL_AMD64_REL32_5
+                    if relocation.addend <= -4 && relocation.addend >= -9 {
+                        0
+                    } else {
+                        relocation.addend + 4
+                    }
+                }
+                _ => relocation.addend,
+            },
+            _ => unimplemented!(),
+        };
+        relocation.addend -= constant;
+        constant
+    }
+
+    fn coff_add_stub_symbol(&mut self, symbol_id: SymbolId) -> SymbolId {
+        if let Some(stub_id) = self.stub_symbols.get(&symbol_id) {
+            return *stub_id;
+        }
+        let stub_size = self.architecture.address_size().unwrap().bytes();
+
+        let name = b".rdata$.refptr".to_vec();
+        let section_id = self.add_section(Vec::new(), name, SectionKind::ReadOnlyData);
+        let section = self.section_mut(section_id);
+        section.set_data(vec![0; stub_size as usize], u64::from(stub_size));
+        section.relocations = vec![Relocation {
+            offset: 0,
+            size: stub_size * 8,
+            kind: RelocationKind::Absolute,
+            encoding: RelocationEncoding::Generic,
+            symbol: symbol_id,
+            addend: 0,
+        }];
+
+        let mut name = b".refptr.".to_vec();
+        name.extend_from_slice(&self.symbol(symbol_id).name);
+        let stub_id = self.add_raw_symbol(Symbol {
+            name,
+            value: 0,
+            size: u64::from(stub_size),
+            kind: SymbolKind::Data,
+            scope: SymbolScope::Compilation,
+            weak: false,
+            section: SymbolSection::Section(section_id),
+            flags: SymbolFlags::None,
+        });
+        self.stub_symbols.insert(symbol_id, stub_id);
+
+        stub_id
+    }
+
+    /// Appends linker directives to the `.drectve` section to tell the linker
+    /// to export all symbols with `SymbolScope::Dynamic`.
+    ///
+    /// This must be called after all symbols have been defined.
+    pub fn add_coff_exports(&mut self, style: CoffExportStyle) {
+        assert_eq!(self.format, BinaryFormat::Coff);
+
+        let mut directives = vec![];
+        for symbol in &self.symbols {
+            if symbol.scope == SymbolScope::Dynamic {
+                match style {
+                    CoffExportStyle::Msvc => directives.extend(b" /EXPORT:\""),
+                    CoffExportStyle::Gnu => directives.extend(b" -export:\""),
+                }
+                directives.extend(&symbol.name);
+                directives.extend(b"\"");
+                if symbol.kind != SymbolKind::Text {
+                    match style {
+                        CoffExportStyle::Msvc => directives.extend(b",DATA"),
+                        CoffExportStyle::Gnu => directives.extend(b",data"),
+                    }
+                }
+            }
+        }
+        let drectve = self.add_section(vec![], b".drectve".to_vec(), SectionKind::Linker);
+        self.append_section_data(drectve, &directives, 1);
+    }
+
+    pub(crate) fn coff_write(&self, buffer: &mut dyn WritableBuffer) -> Result<()> {
+        // Calculate offsets of everything, and build strtab.
+        let mut offset = 0;
+        let mut strtab = StringTable::default();
+
+        // COFF header.
+        offset += mem::size_of::<coff::ImageFileHeader>();
+
+        // Section headers.
+        offset += self.sections.len() * mem::size_of::<coff::ImageSectionHeader>();
+
+        // Calculate size of section data and add section strings to strtab.
+        let mut section_offsets = vec![SectionOffsets::default(); self.sections.len()];
+        for (index, section) in self.sections.iter().enumerate() {
+            if section.name.len() > 8 {
+                section_offsets[index].str_id = Some(strtab.add(&section.name));
+            }
+
+            let len = section.data.len();
+            if len != 0 {
+                // TODO: not sure what alignment is required here, but this seems to match LLVM
+                offset = align(offset, 4);
+                section_offsets[index].offset = offset;
+                offset += len;
+            } else {
+                section_offsets[index].offset = 0;
+            }
+
+            // Calculate size of relocations.
+            let mut count = section.relocations.len();
+            if count != 0 {
+                section_offsets[index].reloc_offset = offset;
+                if count > 0xffff {
+                    count += 1;
+                }
+                offset += count * mem::size_of::<coff::ImageRelocation>();
+            }
+        }
+
+        // Set COMDAT flags.
+        for comdat in &self.comdats {
+            let symbol = &self.symbols[comdat.symbol.0];
+            let comdat_section = match symbol.section {
+                SymbolSection::Section(id) => id.0,
+                _ => {
+                    return Err(Error(format!(
+                        "unsupported COMDAT symbol `{}` section {:?}",
+                        symbol.name().unwrap_or(""),
+                        symbol.section
+                    )));
+                }
+            };
+            section_offsets[comdat_section].selection = match comdat.kind {
+                ComdatKind::NoDuplicates => coff::IMAGE_COMDAT_SELECT_NODUPLICATES,
+                ComdatKind::Any => coff::IMAGE_COMDAT_SELECT_ANY,
+                ComdatKind::SameSize => coff::IMAGE_COMDAT_SELECT_SAME_SIZE,
+                ComdatKind::ExactMatch => coff::IMAGE_COMDAT_SELECT_EXACT_MATCH,
+                ComdatKind::Largest => coff::IMAGE_COMDAT_SELECT_LARGEST,
+                ComdatKind::Newest => coff::IMAGE_COMDAT_SELECT_NEWEST,
+                ComdatKind::Unknown => {
+                    return Err(Error(format!(
+                        "unsupported COMDAT symbol `{}` kind {:?}",
+                        symbol.name().unwrap_or(""),
+                        comdat.kind
+                    )));
+                }
+            };
+            for id in &comdat.sections {
+                let section = &self.sections[id.0];
+                if section.symbol.is_none() {
+                    return Err(Error(format!(
+                        "missing symbol for COMDAT section `{}`",
+                        section.name().unwrap_or(""),
+                    )));
+                }
+                if id.0 != comdat_section {
+                    section_offsets[id.0].selection = coff::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
+                    section_offsets[id.0].associative_section = comdat_section as u16 + 1;
+                }
+            }
+        }
+
+        // Calculate size of symbols and add symbol strings to strtab.
+        let mut symbol_offsets = vec![SymbolOffsets::default(); self.symbols.len()];
+        let mut symtab_count = 0;
+        for (index, symbol) in self.symbols.iter().enumerate() {
+            symbol_offsets[index].index = symtab_count;
+            symtab_count += 1;
+            match symbol.kind {
+                SymbolKind::File => {
+                    // Name goes in auxiliary symbol records.
+                    let aux_count = (symbol.name.len() + coff::IMAGE_SIZEOF_SYMBOL - 1)
+                        / coff::IMAGE_SIZEOF_SYMBOL;
+                    symbol_offsets[index].aux_count = aux_count as u8;
+                    symtab_count += aux_count;
+                    // Don't add name to strtab.
+                    continue;
+                }
+                SymbolKind::Section => {
+                    symbol_offsets[index].aux_count = 1;
+                    symtab_count += 1;
+                }
+                _ => {}
+            }
+            if symbol.name.len() > 8 {
+                symbol_offsets[index].str_id = Some(strtab.add(&symbol.name));
+            }
+        }
+
+        // Calculate size of symtab.
+        let symtab_offset = offset;
+        let symtab_len = symtab_count * coff::IMAGE_SIZEOF_SYMBOL;
+        offset += symtab_len;
+
+        // Calculate size of strtab.
+        let strtab_offset = offset;
+        let mut strtab_data = Vec::new();
+        // First 4 bytes of strtab are the length.
+        strtab.write(4, &mut strtab_data);
+        let strtab_len = strtab_data.len() + 4;
+        offset += strtab_len;
+
+        // Start writing.
+        buffer
+            .reserve(offset)
+            .map_err(|_| Error(String::from("Cannot allocate buffer")))?;
+
+        // Write file header.
+        let header = coff::ImageFileHeader {
+            machine: U16::new(
+                LE,
+                match self.architecture {
+                    Architecture::Arm => coff::IMAGE_FILE_MACHINE_ARMNT,
+                    Architecture::Aarch64 => coff::IMAGE_FILE_MACHINE_ARM64,
+                    Architecture::I386 => coff::IMAGE_FILE_MACHINE_I386,
+                    Architecture::X86_64 => coff::IMAGE_FILE_MACHINE_AMD64,
+                    _ => {
+                        return Err(Error(format!(
+                            "unimplemented architecture {:?}",
+                            self.architecture
+                        )));
+                    }
+                },
+            ),
+            number_of_sections: U16::new(LE, self.sections.len() as u16),
+            time_date_stamp: U32::default(),
+            pointer_to_symbol_table: U32::new(LE, symtab_offset as u32),
+            number_of_symbols: U32::new(LE, symtab_count as u32),
+            size_of_optional_header: U16::default(),
+            characteristics: match self.flags {
+                FileFlags::Coff { characteristics } => U16::new(LE, characteristics),
+                _ => U16::default(),
+            },
+        };
+        buffer.write(&header);
+
+        // Write section headers.
+        for (index, section) in self.sections.iter().enumerate() {
+            let mut characteristics = if let SectionFlags::Coff {
+                characteristics, ..
+            } = section.flags
+            {
+                characteristics
+            } else {
+                match section.kind {
+                    SectionKind::Text => {
+                        coff::IMAGE_SCN_CNT_CODE
+                            | coff::IMAGE_SCN_MEM_EXECUTE
+                            | coff::IMAGE_SCN_MEM_READ
+                    }
+                    SectionKind::Data => {
+                        coff::IMAGE_SCN_CNT_INITIALIZED_DATA
+                            | coff::IMAGE_SCN_MEM_READ
+                            | coff::IMAGE_SCN_MEM_WRITE
+                    }
+                    SectionKind::UninitializedData => {
+                        coff::IMAGE_SCN_CNT_UNINITIALIZED_DATA
+                            | coff::IMAGE_SCN_MEM_READ
+                            | coff::IMAGE_SCN_MEM_WRITE
+                    }
+                    SectionKind::ReadOnlyData
+                    | SectionKind::ReadOnlyDataWithRel
+                    | SectionKind::ReadOnlyString => {
+                        coff::IMAGE_SCN_CNT_INITIALIZED_DATA | coff::IMAGE_SCN_MEM_READ
+                    }
+                    SectionKind::Debug | SectionKind::Other | SectionKind::OtherString => {
+                        coff::IMAGE_SCN_CNT_INITIALIZED_DATA
+                            | coff::IMAGE_SCN_MEM_READ
+                            | coff::IMAGE_SCN_MEM_DISCARDABLE
+                    }
+                    SectionKind::Linker => coff::IMAGE_SCN_LNK_INFO | coff::IMAGE_SCN_LNK_REMOVE,
+                    SectionKind::Common
+                    | SectionKind::Tls
+                    | SectionKind::UninitializedTls
+                    | SectionKind::TlsVariables
+                    | SectionKind::Note
+                    | SectionKind::Unknown
+                    | SectionKind::Metadata
+                    | SectionKind::Elf(_) => {
+                        return Err(Error(format!(
+                            "unimplemented section `{}` kind {:?}",
+                            section.name().unwrap_or(""),
+                            section.kind
+                        )));
+                    }
+                }
+            };
+            if section_offsets[index].selection != 0 {
+                characteristics |= coff::IMAGE_SCN_LNK_COMDAT;
+            };
+            if section.relocations.len() > 0xffff {
+                characteristics |= coff::IMAGE_SCN_LNK_NRELOC_OVFL;
+            }
+            characteristics |= match section.align {
+                1 => coff::IMAGE_SCN_ALIGN_1BYTES,
+                2 => coff::IMAGE_SCN_ALIGN_2BYTES,
+                4 => coff::IMAGE_SCN_ALIGN_4BYTES,
+                8 => coff::IMAGE_SCN_ALIGN_8BYTES,
+                16 => coff::IMAGE_SCN_ALIGN_16BYTES,
+                32 => coff::IMAGE_SCN_ALIGN_32BYTES,
+                64 => coff::IMAGE_SCN_ALIGN_64BYTES,
+                128 => coff::IMAGE_SCN_ALIGN_128BYTES,
+                256 => coff::IMAGE_SCN_ALIGN_256BYTES,
+                512 => coff::IMAGE_SCN_ALIGN_512BYTES,
+                1024 => coff::IMAGE_SCN_ALIGN_1024BYTES,
+                2048 => coff::IMAGE_SCN_ALIGN_2048BYTES,
+                4096 => coff::IMAGE_SCN_ALIGN_4096BYTES,
+                8192 => coff::IMAGE_SCN_ALIGN_8192BYTES,
+                _ => {
+                    return Err(Error(format!(
+                        "unimplemented section `{}` align {}",
+                        section.name().unwrap_or(""),
+                        section.align
+                    )));
+                }
+            };
+            let mut coff_section = coff::ImageSectionHeader {
+                name: [0; 8],
+                virtual_size: U32::default(),
+                virtual_address: U32::default(),
+                size_of_raw_data: U32::new(LE, section.size as u32),
+                pointer_to_raw_data: U32::new(LE, section_offsets[index].offset as u32),
+                pointer_to_relocations: U32::new(LE, section_offsets[index].reloc_offset as u32),
+                pointer_to_linenumbers: U32::default(),
+                number_of_relocations: if section.relocations.len() > 0xffff {
+                    U16::new(LE, 0xffff)
+                } else {
+                    U16::new(LE, section.relocations.len() as u16)
+                },
+                number_of_linenumbers: U16::default(),
+                characteristics: U32::new(LE, characteristics),
+            };
+            if section.name.len() <= 8 {
+                coff_section.name[..section.name.len()].copy_from_slice(&section.name);
+            } else {
+                let mut str_offset = strtab.get_offset(section_offsets[index].str_id.unwrap());
+                if str_offset <= 9_999_999 {
+                    let mut name = [0; 7];
+                    let mut len = 0;
+                    if str_offset == 0 {
+                        name[6] = b'0';
+                        len = 1;
+                    } else {
+                        while str_offset != 0 {
+                            let rem = (str_offset % 10) as u8;
+                            str_offset /= 10;
+                            name[6 - len] = b'0' + rem;
+                            len += 1;
+                        }
+                    }
+                    coff_section.name = [0; 8];
+                    coff_section.name[0] = b'/';
+                    coff_section.name[1..][..len].copy_from_slice(&name[7 - len..]);
+                } else if str_offset as u64 <= 0xf_ffff_ffff {
+                    coff_section.name[0] = b'/';
+                    coff_section.name[1] = b'/';
+                    for i in 0..6 {
+                        let rem = (str_offset % 64) as u8;
+                        str_offset /= 64;
+                        let c = match rem {
+                            0..=25 => b'A' + rem,
+                            26..=51 => b'a' + rem - 26,
+                            52..=61 => b'0' + rem - 52,
+                            62 => b'+',
+                            63 => b'/',
+                            _ => unreachable!(),
+                        };
+                        coff_section.name[7 - i] = c;
+                    }
+                } else {
+                    return Err(Error(format!("invalid section name offset {}", str_offset)));
+                }
+            }
+            buffer.write(&coff_section);
+        }
+
+        // Write section data and relocations.
+        for (index, section) in self.sections.iter().enumerate() {
+            let len = section.data.len();
+            if len != 0 {
+                write_align(buffer, 4);
+                debug_assert_eq!(section_offsets[index].offset, buffer.len());
+                buffer.write_bytes(&section.data);
+            }
+
+            if !section.relocations.is_empty() {
+                debug_assert_eq!(section_offsets[index].reloc_offset, buffer.len());
+                if section.relocations.len() > 0xffff {
+                    let coff_relocation = coff::ImageRelocation {
+                        virtual_address: U32Bytes::new(LE, section.relocations.len() as u32 + 1),
+                        symbol_table_index: U32Bytes::new(LE, 0),
+                        typ: U16Bytes::new(LE, 0),
+                    };
+                    buffer.write(&coff_relocation);
+                }
+                for reloc in &section.relocations {
+                    //assert!(reloc.implicit_addend);
+                    let typ = match self.architecture {
+                        Architecture::I386 => match (reloc.kind, reloc.size, reloc.addend) {
+                            (RelocationKind::Absolute, 16, 0) => coff::IMAGE_REL_I386_DIR16,
+                            (RelocationKind::Relative, 16, 0) => coff::IMAGE_REL_I386_REL16,
+                            (RelocationKind::Absolute, 32, 0) => coff::IMAGE_REL_I386_DIR32,
+                            (RelocationKind::ImageOffset, 32, 0) => coff::IMAGE_REL_I386_DIR32NB,
+                            (RelocationKind::SectionIndex, 16, 0) => coff::IMAGE_REL_I386_SECTION,
+                            (RelocationKind::SectionOffset, 32, 0) => coff::IMAGE_REL_I386_SECREL,
+                            (RelocationKind::SectionOffset, 7, 0) => coff::IMAGE_REL_I386_SECREL7,
+                            (RelocationKind::Relative, 32, -4) => coff::IMAGE_REL_I386_REL32,
+                            (RelocationKind::Coff(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::X86_64 => match (reloc.kind, reloc.size, reloc.addend) {
+                            (RelocationKind::Absolute, 64, 0) => coff::IMAGE_REL_AMD64_ADDR64,
+                            (RelocationKind::Absolute, 32, 0) => coff::IMAGE_REL_AMD64_ADDR32,
+                            (RelocationKind::ImageOffset, 32, 0) => coff::IMAGE_REL_AMD64_ADDR32NB,
+                            (RelocationKind::Relative, 32, -4) => coff::IMAGE_REL_AMD64_REL32,
+                            (RelocationKind::Relative, 32, -5) => coff::IMAGE_REL_AMD64_REL32_1,
+                            (RelocationKind::Relative, 32, -6) => coff::IMAGE_REL_AMD64_REL32_2,
+                            (RelocationKind::Relative, 32, -7) => coff::IMAGE_REL_AMD64_REL32_3,
+                            (RelocationKind::Relative, 32, -8) => coff::IMAGE_REL_AMD64_REL32_4,
+                            (RelocationKind::Relative, 32, -9) => coff::IMAGE_REL_AMD64_REL32_5,
+                            (RelocationKind::SectionIndex, 16, 0) => coff::IMAGE_REL_AMD64_SECTION,
+                            (RelocationKind::SectionOffset, 32, 0) => coff::IMAGE_REL_AMD64_SECREL,
+                            (RelocationKind::SectionOffset, 7, 0) => coff::IMAGE_REL_AMD64_SECREL7,
+                            (RelocationKind::Coff(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::Arm => match (reloc.kind, reloc.size, reloc.addend) {
+                            (RelocationKind::Absolute, 32, 0) => coff::IMAGE_REL_ARM_ADDR32,
+                            (RelocationKind::ImageOffset, 32, 0) => coff::IMAGE_REL_ARM_ADDR32NB,
+                            (RelocationKind::Relative, 32, -4) => coff::IMAGE_REL_ARM_REL32,
+                            (RelocationKind::SectionIndex, 16, 0) => coff::IMAGE_REL_ARM_SECTION,
+                            (RelocationKind::SectionOffset, 32, 0) => coff::IMAGE_REL_ARM_SECREL,
+                            (RelocationKind::Coff(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::Aarch64 => match (reloc.kind, reloc.size, reloc.addend) {
+                            (RelocationKind::Absolute, 32, 0) => coff::IMAGE_REL_ARM64_ADDR32,
+                            (RelocationKind::ImageOffset, 32, 0) => coff::IMAGE_REL_ARM64_ADDR32NB,
+                            (RelocationKind::SectionIndex, 16, 0) => coff::IMAGE_REL_ARM64_SECTION,
+                            (RelocationKind::SectionOffset, 32, 0) => coff::IMAGE_REL_ARM64_SECREL,
+                            (RelocationKind::Absolute, 64, 0) => coff::IMAGE_REL_ARM64_ADDR64,
+                            (RelocationKind::Relative, 32, -4) => coff::IMAGE_REL_ARM64_REL32,
+                            (RelocationKind::Coff(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        _ => {
+                            return Err(Error(format!(
+                                "unimplemented architecture {:?}",
+                                self.architecture
+                            )));
+                        }
+                    };
+                    let coff_relocation = coff::ImageRelocation {
+                        virtual_address: U32Bytes::new(LE, reloc.offset as u32),
+                        symbol_table_index: U32Bytes::new(
+                            LE,
+                            symbol_offsets[reloc.symbol.0].index as u32,
+                        ),
+                        typ: U16Bytes::new(LE, typ),
+                    };
+                    buffer.write(&coff_relocation);
+                }
+            }
+        }
+
+        // Write symbols.
+        debug_assert_eq!(symtab_offset, buffer.len());
+        for (index, symbol) in self.symbols.iter().enumerate() {
+            let mut name = &symbol.name[..];
+            let section_number = match symbol.section {
+                SymbolSection::None => {
+                    debug_assert_eq!(symbol.kind, SymbolKind::File);
+                    coff::IMAGE_SYM_DEBUG as u16
+                }
+                SymbolSection::Undefined => coff::IMAGE_SYM_UNDEFINED as u16,
+                SymbolSection::Absolute => coff::IMAGE_SYM_ABSOLUTE as u16,
+                SymbolSection::Common => coff::IMAGE_SYM_UNDEFINED as u16,
+                SymbolSection::Section(id) => id.0 as u16 + 1,
+            };
+            let typ = if symbol.kind == SymbolKind::Text {
+                coff::IMAGE_SYM_DTYPE_FUNCTION << coff::IMAGE_SYM_DTYPE_SHIFT
+            } else {
+                coff::IMAGE_SYM_TYPE_NULL
+            };
+            let storage_class = match symbol.kind {
+                SymbolKind::File => {
+                    // Name goes in auxiliary symbol records.
+                    name = b".file";
+                    coff::IMAGE_SYM_CLASS_FILE
+                }
+                SymbolKind::Section => coff::IMAGE_SYM_CLASS_STATIC,
+                SymbolKind::Label => coff::IMAGE_SYM_CLASS_LABEL,
+                SymbolKind::Text | SymbolKind::Data | SymbolKind::Tls => {
+                    match symbol.section {
+                        SymbolSection::None => {
+                            return Err(Error(format!(
+                                "missing section for symbol `{}`",
+                                symbol.name().unwrap_or("")
+                            )));
+                        }
+                        SymbolSection::Undefined | SymbolSection::Common => {
+                            coff::IMAGE_SYM_CLASS_EXTERNAL
+                        }
+                        SymbolSection::Absolute | SymbolSection::Section(_) => {
+                            match symbol.scope {
+                                // TODO: does this need aux symbol records too?
+                                _ if symbol.weak => coff::IMAGE_SYM_CLASS_WEAK_EXTERNAL,
+                                SymbolScope::Unknown => {
+                                    return Err(Error(format!(
+                                        "unimplemented symbol `{}` scope {:?}",
+                                        symbol.name().unwrap_or(""),
+                                        symbol.scope
+                                    )));
+                                }
+                                SymbolScope::Compilation => coff::IMAGE_SYM_CLASS_STATIC,
+                                SymbolScope::Linkage | SymbolScope::Dynamic => {
+                                    coff::IMAGE_SYM_CLASS_EXTERNAL
+                                }
+                            }
+                        }
+                    }
+                }
+                SymbolKind::Unknown | SymbolKind::Null => {
+                    return Err(Error(format!(
+                        "unimplemented symbol `{}` kind {:?}",
+                        symbol.name().unwrap_or(""),
+                        symbol.kind
+                    )));
+                }
+            };
+            let number_of_aux_symbols = symbol_offsets[index].aux_count;
+            let value = if symbol.section == SymbolSection::Common {
+                symbol.size as u32
+            } else {
+                symbol.value as u32
+            };
+            let mut coff_symbol = coff::ImageSymbol {
+                name: [0; 8],
+                value: U32Bytes::new(LE, value),
+                section_number: U16Bytes::new(LE, section_number),
+                typ: U16Bytes::new(LE, typ),
+                storage_class,
+                number_of_aux_symbols,
+            };
+            if name.len() <= 8 {
+                coff_symbol.name[..name.len()].copy_from_slice(name);
+            } else {
+                let str_offset = strtab.get_offset(symbol_offsets[index].str_id.unwrap());
+                coff_symbol.name[4..8].copy_from_slice(&u32::to_le_bytes(str_offset as u32));
+            }
+            buffer.write(&coff_symbol);
+
+            // Write auxiliary symbols.
+            match symbol.kind {
+                SymbolKind::File => {
+                    let aux_len = number_of_aux_symbols as usize * coff::IMAGE_SIZEOF_SYMBOL;
+                    debug_assert!(aux_len >= symbol.name.len());
+                    let old_len = buffer.len();
+                    buffer.write_bytes(&symbol.name);
+                    buffer.resize(old_len + aux_len);
+                }
+                SymbolKind::Section => {
+                    debug_assert_eq!(number_of_aux_symbols, 1);
+                    let section_index = symbol.section.id().unwrap().0;
+                    let section = &self.sections[section_index];
+                    let aux = coff::ImageAuxSymbolSection {
+                        length: U32Bytes::new(LE, section.size as u32),
+                        number_of_relocations: if section.relocations.len() > 0xffff {
+                            U16Bytes::new(LE, 0xffff)
+                        } else {
+                            U16Bytes::new(LE, section.relocations.len() as u16)
+                        },
+                        number_of_linenumbers: U16Bytes::default(),
+                        check_sum: U32Bytes::new(LE, checksum(section.data())),
+                        number: U16Bytes::new(
+                            LE,
+                            section_offsets[section_index].associative_section,
+                        ),
+                        selection: section_offsets[section_index].selection,
+                        reserved: 0,
+                        // TODO: bigobj
+                        high_number: U16Bytes::default(),
+                    };
+                    buffer.write(&aux);
+                }
+                _ => {
+                    debug_assert_eq!(number_of_aux_symbols, 0);
+                }
+            }
+        }
+
+        // Write strtab section.
+        debug_assert_eq!(strtab_offset, buffer.len());
+        buffer.write_bytes(&u32::to_le_bytes(strtab_len as u32));
+        buffer.write_bytes(&strtab_data);
+
+        debug_assert_eq!(offset, buffer.len());
+
+        Ok(())
+    }
+}
+
+// JamCRC
+fn checksum(data: &[u8]) -> u32 {
+    let mut hasher = crc32fast::Hasher::new_with_initial(0xffff_ffff);
+    hasher.update(data);
+    !hasher.finalize()
+}