diff options
Diffstat (limited to 'third_party/rust/object/src/write/mod.rs')
| -rw-r--r-- | third_party/rust/object/src/write/mod.rs | 674 |
1 files changed, 674 insertions, 0 deletions
diff --git a/third_party/rust/object/src/write/mod.rs b/third_party/rust/object/src/write/mod.rs new file mode 100644 index 0000000000..79ffc16599 --- /dev/null +++ b/third_party/rust/object/src/write/mod.rs @@ -0,0 +1,674 @@ +//! Interface for writing object files. + +#![allow(clippy::collapsible_if)] +#![allow(clippy::cognitive_complexity)] +#![allow(clippy::module_inception)] + +use scroll::Pwrite; +use std::collections::HashMap; +use std::string::String; + +use crate::alloc::vec::Vec; +use crate::target_lexicon::{Architecture, BinaryFormat, Endianness, PointerWidth}; +use crate::{RelocationEncoding, RelocationKind, SectionKind, SymbolKind, SymbolScope}; + +mod coff; +mod elf; +mod macho; +mod string; +mod util; + +/// A writable object file. +#[derive(Debug)] +pub struct Object { + format: BinaryFormat, + architecture: Architecture, + sections: Vec<Section>, + standard_sections: HashMap<StandardSection, SectionId>, + symbols: Vec<Symbol>, + symbol_map: HashMap<Vec<u8>, SymbolId>, + stub_symbols: HashMap<SymbolId, SymbolId>, + subsection_via_symbols: bool, + /// The symbol name mangling scheme. + pub mangling: Mangling, + /// Mach-O "_tlv_bootstrap" symbol. + tlv_bootstrap: Option<SymbolId>, +} + +impl Object { + /// Create an empty object file. + pub fn new(format: BinaryFormat, architecture: Architecture) -> Object { + Object { + format, + architecture, + sections: Vec::new(), + standard_sections: HashMap::new(), + symbols: Vec::new(), + symbol_map: HashMap::new(), + stub_symbols: HashMap::new(), + subsection_via_symbols: false, + mangling: Mangling::default(format, architecture), + tlv_bootstrap: None, + } + } + + /// Return the file format. + #[inline] + pub fn format(&self) -> BinaryFormat { + self.format + } + + /// Return the architecture. + #[inline] + pub fn architecture(&self) -> Architecture { + self.architecture + } + + /// Return the current mangling setting. + #[inline] + pub fn mangling(&self) -> Mangling { + self.mangling + } + + /// Return the current mangling setting. + #[inline] + pub fn set_mangling(&mut self, mangling: Mangling) { + self.mangling = mangling; + } + + /// Return the name for a standard segment. + /// + /// This will vary based on the file format. + pub fn segment_name(&self, segment: StandardSegment) -> &'static [u8] { + match self.format { + BinaryFormat::Elf | BinaryFormat::Coff => &[], + BinaryFormat::Macho => self.macho_segment_name(segment), + _ => unimplemented!(), + } + } + + /// Get the section with the given `SectionId`. + #[inline] + pub fn section(&self, section: SectionId) -> &Section { + &self.sections[section.0] + } + + /// Mutably get the section with the given `SectionId`. + #[inline] + pub fn section_mut(&mut self, section: SectionId) -> &mut Section { + &mut self.sections[section.0] + } + + /// Append data to an existing section. Returns the section offset of the data. + pub fn append_section_data(&mut self, section: SectionId, data: &[u8], align: u64) -> u64 { + self.sections[section.0].append_data(data, align) + } + + /// Append zero-initialized data to an existing section. Returns the section offset of the data. + pub fn append_section_bss(&mut self, section: SectionId, size: u64, align: u64) -> u64 { + self.sections[section.0].append_bss(size, align) + } + + /// Return the `SectionId` of a standard section. + /// + /// If the section doesn't already exist then it is created. + pub fn section_id(&mut self, section: StandardSection) -> SectionId { + self.standard_sections + .get(§ion) + .cloned() + .unwrap_or_else(|| { + let (segment, name, kind) = self.section_info(section); + self.add_section(segment.to_vec(), name.to_vec(), kind) + }) + } + + /// Add a new section and return its `SectionId`. + /// + /// This also creates a section symbol. + pub fn add_section(&mut self, segment: Vec<u8>, name: Vec<u8>, kind: SectionKind) -> SectionId { + let id = SectionId(self.sections.len()); + self.sections.push(Section { + segment, + name, + kind, + size: 0, + align: 1, + data: Vec::new(), + relocations: Vec::new(), + symbol: None, + }); + + // Add to self.standard_sections if required. This may match multiple standard sections. + let section = &self.sections[id.0]; + for standard_section in StandardSection::all() { + if !self.standard_sections.contains_key(standard_section) { + let (segment, name, kind) = self.section_info(*standard_section); + if segment == &*section.segment && name == &*section.name && kind == section.kind { + self.standard_sections.insert(*standard_section, id); + } + } + } + + id + } + + fn section_info( + &self, + section: StandardSection, + ) -> (&'static [u8], &'static [u8], SectionKind) { + match self.format { + BinaryFormat::Elf => self.elf_section_info(section), + BinaryFormat::Coff => self.coff_section_info(section), + BinaryFormat::Macho => self.macho_section_info(section), + _ => unimplemented!(), + } + } + + /// Add a subsection. Returns the `SectionId` and section offset of the data. + pub fn add_subsection( + &mut self, + section: StandardSection, + name: &[u8], + data: &[u8], + align: u64, + ) -> (SectionId, u64) { + let section_id = if self.has_subsection_via_symbols() { + self.subsection_via_symbols = true; + self.section_id(section) + } else { + let (segment, name, kind) = self.subsection_info(section, name); + self.add_section(segment.to_vec(), name, kind) + }; + let offset = self.append_section_data(section_id, data, align); + (section_id, offset) + } + + fn has_subsection_via_symbols(&self) -> bool { + match self.format { + BinaryFormat::Elf | BinaryFormat::Coff => false, + BinaryFormat::Macho => true, + _ => unimplemented!(), + } + } + + fn subsection_info( + &self, + section: StandardSection, + value: &[u8], + ) -> (&'static [u8], Vec<u8>, SectionKind) { + let (segment, section, kind) = self.section_info(section); + let name = self.subsection_name(section, value); + (segment, name, kind) + } + + fn subsection_name(&self, section: &[u8], value: &[u8]) -> Vec<u8> { + debug_assert!(!self.has_subsection_via_symbols()); + match self.format { + BinaryFormat::Elf => self.elf_subsection_name(section, value), + BinaryFormat::Coff => self.coff_subsection_name(section, value), + _ => unimplemented!(), + } + } + + /// Get the `SymbolId` of the symbol with the given name. + pub fn symbol_id(&self, name: &[u8]) -> Option<SymbolId> { + self.symbol_map.get(name).cloned() + } + + /// Get the symbol with the given `SymbolId`. + #[inline] + pub fn symbol(&self, symbol: SymbolId) -> &Symbol { + &self.symbols[symbol.0] + } + + /// Mutably get the symbol with the given `SymbolId`. + #[inline] + pub fn symbol_mut(&mut self, symbol: SymbolId) -> &mut Symbol { + &mut self.symbols[symbol.0] + } + + /// Add a new symbol and return its `SymbolId`. + pub fn add_symbol(&mut self, mut symbol: Symbol) -> SymbolId { + // Defined symbols must have a scope. + debug_assert!(symbol.is_undefined() || symbol.scope != SymbolScope::Unknown); + if symbol.kind == SymbolKind::Section { + return self.section_symbol(symbol.section.unwrap()); + } + if !symbol.name.is_empty() + && (symbol.kind == SymbolKind::Text + || symbol.kind == SymbolKind::Data + || symbol.kind == SymbolKind::Tls) + { + let unmangled_name = symbol.name.clone(); + if let Some(prefix) = self.mangling.global_prefix() { + symbol.name.insert(0, prefix); + } + let symbol_id = self.add_raw_symbol(symbol); + self.symbol_map.insert(unmangled_name, symbol_id); + symbol_id + } else { + self.add_raw_symbol(symbol) + } + } + + fn add_raw_symbol(&mut self, symbol: Symbol) -> SymbolId { + let symbol_id = SymbolId(self.symbols.len()); + self.symbols.push(symbol); + symbol_id + } + + /// Return true if the file format supports `StandardSection::UninitializedTls`. + pub fn has_uninitialized_tls(&self) -> bool { + self.format != BinaryFormat::Coff + } + + /// Add a new file symbol and return its `SymbolId`. + pub fn add_file_symbol(&mut self, name: Vec<u8>) -> SymbolId { + self.add_raw_symbol(Symbol { + name, + value: 0, + size: 0, + kind: SymbolKind::File, + scope: SymbolScope::Compilation, + weak: false, + section: None, + }) + } + + /// Get the symbol for a section. + pub fn section_symbol(&mut self, section_id: SectionId) -> SymbolId { + let section = &mut self.sections[section_id.0]; + if let Some(symbol) = section.symbol { + return symbol; + } + let name = if self.format == BinaryFormat::Coff { + section.name.clone() + } else { + Vec::new() + }; + let symbol_id = SymbolId(self.symbols.len()); + self.symbols.push(Symbol { + name, + value: 0, + size: 0, + kind: SymbolKind::Section, + scope: SymbolScope::Compilation, + weak: false, + section: Some(section_id), + }); + section.symbol = Some(symbol_id); + symbol_id + } + + /// Append data to an existing section, and update a symbol to refer to it. + /// + /// For Mach-O, this also creates a `__thread_vars` entry for TLS symbols, and the + /// symbol will indirectly point to the added data via the `__thread_vars` entry. + /// + /// Returns the section offset of the data. + pub fn add_symbol_data( + &mut self, + symbol_id: SymbolId, + section: SectionId, + data: &[u8], + align: u64, + ) -> u64 { + let offset = self.append_section_data(section, data, align); + self.set_symbol_data(symbol_id, section, offset, data.len() as u64); + offset + } + + /// Append zero-initialized data to an existing section, and update a symbol to refer to it. + /// + /// For Mach-O, this also creates a `__thread_vars` entry for TLS symbols, and the + /// symbol will indirectly point to the added data via the `__thread_vars` entry. + /// + /// Returns the section offset of the data. + pub fn add_symbol_bss( + &mut self, + symbol_id: SymbolId, + section: SectionId, + size: u64, + align: u64, + ) -> u64 { + let offset = self.append_section_bss(section, size, align); + self.set_symbol_data(symbol_id, section, offset, size); + offset + } + + /// Update a symbol to refer to the given data within a section. + /// + /// For Mach-O, this also creates a `__thread_vars` entry for TLS symbols, and the + /// symbol will indirectly point to the data via the `__thread_vars` entry. + pub fn set_symbol_data( + &mut self, + mut symbol_id: SymbolId, + section: SectionId, + offset: u64, + size: u64, + ) { + // Defined symbols must have a scope. + debug_assert!(self.symbol(symbol_id).scope != SymbolScope::Unknown); + if self.format == BinaryFormat::Macho { + symbol_id = self.macho_add_thread_var(symbol_id); + } + let symbol = self.symbol_mut(symbol_id); + symbol.value = offset; + symbol.size = size; + symbol.section = Some(section); + } + + /// Convert a symbol to a section symbol and offset. + /// + /// Returns an error if the symbol is not defined. + pub fn symbol_section_and_offset( + &mut self, + symbol_id: SymbolId, + ) -> Result<(SymbolId, u64), ()> { + let symbol = self.symbol(symbol_id); + if symbol.kind == SymbolKind::Section { + return Ok((symbol_id, 0)); + } + let symbol_offset = symbol.value; + let section = symbol.section.ok_or(())?; + let section_symbol = self.section_symbol(section); + Ok((section_symbol, symbol_offset)) + } + + /// Add a relocation to a section. + /// + /// Relocations must only be added after the referenced symbols have been added + /// and defined (if applicable). + pub fn add_relocation( + &mut self, + section: SectionId, + mut relocation: Relocation, + ) -> Result<(), String> { + let addend = match self.format { + BinaryFormat::Elf => self.elf_fixup_relocation(&mut relocation)?, + BinaryFormat::Coff => self.coff_fixup_relocation(&mut relocation), + BinaryFormat::Macho => self.macho_fixup_relocation(&mut relocation), + _ => unimplemented!(), + }; + if addend != 0 { + self.write_relocation_addend(section, &relocation, addend)?; + } + self.sections[section.0].relocations.push(relocation); + Ok(()) + } + + fn write_relocation_addend( + &mut self, + section: SectionId, + relocation: &Relocation, + addend: i64, + ) -> Result<(), String> { + let endian = match self.architecture.endianness().unwrap() { + Endianness::Little => scroll::LE, + Endianness::Big => scroll::BE, + }; + + let data = &mut self.sections[section.0].data; + if relocation.offset + (u64::from(relocation.size) + 7) / 8 > data.len() as u64 { + return Err(format!( + "invalid relocation offset {}+{} (max {})", + relocation.offset, + relocation.size, + data.len() + )); + } + match relocation.size { + 32 => { + data.pwrite_with(addend as i32, relocation.offset as usize, endian) + .unwrap(); + } + 64 => { + data.pwrite_with(addend, relocation.offset as usize, endian) + .unwrap(); + } + _ => return Err(format!("unimplemented relocation addend {:?}", relocation)), + } + Ok(()) + } + + /// Write the object to a `Vec`. + pub fn write(&self) -> Result<Vec<u8>, String> { + match self.format { + BinaryFormat::Elf => self.elf_write(), + BinaryFormat::Coff => self.coff_write(), + BinaryFormat::Macho => self.macho_write(), + _ => unimplemented!(), + } + } +} + +/// A standard segment kind. +#[allow(missing_docs)] +#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)] +pub enum StandardSegment { + Text, + Data, + Debug, +} + +/// A standard section kind. +#[allow(missing_docs)] +#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)] +pub enum StandardSection { + Text, + Data, + ReadOnlyData, + ReadOnlyDataWithRel, + ReadOnlyString, + UninitializedData, + Tls, + /// Zero-fill TLS initializers. Unsupported for COFF. + UninitializedTls, + /// TLS variable structures. Only supported for Mach-O. + TlsVariables, +} + +impl StandardSection { + /// Return the section kind of a standard section. + pub fn kind(self) -> SectionKind { + match self { + StandardSection::Text => SectionKind::Text, + StandardSection::Data => SectionKind::Data, + StandardSection::ReadOnlyData | StandardSection::ReadOnlyDataWithRel => { + SectionKind::ReadOnlyData + } + StandardSection::ReadOnlyString => SectionKind::ReadOnlyString, + StandardSection::UninitializedData => SectionKind::UninitializedData, + StandardSection::Tls => SectionKind::Tls, + StandardSection::UninitializedTls => SectionKind::UninitializedTls, + StandardSection::TlsVariables => SectionKind::TlsVariables, + } + } + + fn all() -> &'static [StandardSection] { + &[ + StandardSection::Text, + StandardSection::Data, + StandardSection::ReadOnlyData, + StandardSection::ReadOnlyDataWithRel, + StandardSection::ReadOnlyString, + StandardSection::UninitializedData, + StandardSection::Tls, + StandardSection::UninitializedTls, + StandardSection::TlsVariables, + ] + } +} + +/// An identifier used to reference a section. +#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)] +pub struct SectionId(usize); + +/// A section in an object file. +#[derive(Debug)] +pub struct Section { + segment: Vec<u8>, + name: Vec<u8>, + kind: SectionKind, + size: u64, + align: u64, + data: Vec<u8>, + relocations: Vec<Relocation>, + symbol: Option<SymbolId>, +} + +impl Section { + /// Return true if this section contains uninitialized data. + #[inline] + pub fn is_bss(&self) -> bool { + self.kind == SectionKind::UninitializedData || self.kind == SectionKind::UninitializedTls + } + + /// Set the data for a section. + /// + /// Must not be called for sections that already have data, or that contain uninitialized data. + pub fn set_data(&mut self, data: Vec<u8>, align: u64) { + debug_assert!(!self.is_bss()); + debug_assert_eq!(align & (align - 1), 0); + debug_assert!(self.data.is_empty()); + self.size = data.len() as u64; + self.data = data; + self.align = align; + } + + /// Append data to a section. + /// + /// Must not be called for sections that contain uninitialized data. + pub fn append_data(&mut self, data: &[u8], align: u64) -> u64 { + debug_assert!(!self.is_bss()); + debug_assert_eq!(align & (align - 1), 0); + if self.align < align { + self.align = align; + } + let align = align as usize; + let mut offset = self.data.len(); + if offset & (align - 1) != 0 { + offset += align - (offset & (align - 1)); + self.data.resize(offset, 0); + } + self.data.extend(data); + self.size = self.data.len() as u64; + offset as u64 + } + + /// Append unitialized data to a section. + /// + /// Must not be called for sections that contain initialized data. + pub fn append_bss(&mut self, size: u64, align: u64) -> u64 { + debug_assert!(self.is_bss()); + debug_assert_eq!(align & (align - 1), 0); + if self.align < align { + self.align = align; + } + let mut offset = self.size; + if offset & (align - 1) != 0 { + offset += align - (offset & (align - 1)); + self.size = offset; + } + self.size += size; + offset as u64 + } +} + +/// An identifier used to reference a symbol. +#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)] +pub struct SymbolId(usize); + +/// A symbol in an object file. +#[derive(Debug)] +pub struct Symbol { + /// The name of the symbol. + pub name: Vec<u8>, + /// The value of the symbol. + /// + /// If the symbol defined in a section, then this is the section offset of the symbol. + pub value: u64, + /// The size of the symbol. + pub size: u64, + /// The kind of the symbol. + pub kind: SymbolKind, + /// The scope of the symbol. + pub scope: SymbolScope, + /// Whether the symbol has weak binding. + pub weak: bool, + /// The section containing the symbol. + /// + /// Set to `None` for undefined symbols. + pub section: Option<SectionId>, +} + +impl Symbol { + /// Return true if the symbol is undefined. + #[inline] + pub fn is_undefined(&self) -> bool { + self.section.is_none() + } + + /// Return true if the symbol scope is local. + #[inline] + pub fn is_local(&self) -> bool { + self.scope == SymbolScope::Compilation + } +} + +/// A relocation in an object file. +#[derive(Debug)] +pub struct Relocation { + /// The section offset of the place of the relocation. + pub offset: u64, + /// The size in bits of the place of relocation. + pub size: u8, + /// The operation used to calculate the result of the relocation. + pub kind: RelocationKind, + /// Information about how the result of the relocation operation is encoded in the place. + pub encoding: RelocationEncoding, + /// The symbol referred to by the relocation. + /// + /// This may be a section symbol. + pub symbol: SymbolId, + /// The addend to use in the relocation calculation. + /// + /// This may be in addition to an implicit addend stored at the place of the relocation. + pub addend: i64, +} + +/// The symbol name mangling scheme. +#[derive(Debug, Clone, Copy, PartialEq, Eq)] +pub enum Mangling { + /// No symbol mangling. + None, + /// Windows COFF symbol mangling. + Coff, + /// Windows COFF i386 symbol mangling. + CoffI386, + /// ELF symbol mangling. + Elf, + /// Mach-O symbol mangling. + Macho, +} + +impl Mangling { + /// Return the default symboling mangling for the given format and architecture. + pub fn default(format: BinaryFormat, architecture: Architecture) -> Self { + match (format, architecture) { + (BinaryFormat::Coff, Architecture::I386) => Mangling::CoffI386, + (BinaryFormat::Coff, _) => Mangling::Coff, + (BinaryFormat::Elf, _) => Mangling::Elf, + (BinaryFormat::Macho, _) => Mangling::Macho, + _ => Mangling::None, + } + } + + /// Return the prefix to use for global symbols. + pub fn global_prefix(self) -> Option<u8> { + match self { + Mangling::None | Mangling::Elf | Mangling::Coff => None, + Mangling::CoffI386 | Mangling::Macho => Some(b'_'), + } + } +} |