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//! Support for reading short import files.
//!
//! These are used by some Windows linkers as a more compact way to describe
//! dynamically imported symbols.
use crate::read::{Architecture, Error, ReadError, ReadRef, Result};
use crate::{pe, ByteString, Bytes, LittleEndian as LE};
/// A Windows short form description of a symbol to import.
///
/// Used in Windows import libraries to provide a mapping from
/// a symbol name to a DLL export. This is not an object file.
#[derive(Debug, Clone)]
pub struct ImportFile<'data> {
header: &'data pe::ImportObjectHeader,
kind: ImportType,
dll: ByteString<'data>,
symbol: ByteString<'data>,
import: Option<ByteString<'data>>,
}
impl<'data> ImportFile<'data> {
/// Parse it.
pub fn parse<R: ReadRef<'data>>(data: R) -> Result<Self> {
let mut offset = 0;
let header = pe::ImportObjectHeader::parse(data, &mut offset)?;
let data = header.parse_data(data, &mut offset)?;
// Unmangles a name by removing a `?`, `@` or `_` prefix.
fn strip_prefix(s: &[u8]) -> &[u8] {
match s.split_first() {
Some((b, rest)) if [b'?', b'@', b'_'].contains(b) => rest,
_ => s,
}
}
Ok(Self {
header,
dll: data.dll,
symbol: data.symbol,
kind: match header.import_type() {
pe::IMPORT_OBJECT_CODE => ImportType::Code,
pe::IMPORT_OBJECT_DATA => ImportType::Data,
pe::IMPORT_OBJECT_CONST => ImportType::Const,
_ => return Err(Error("Invalid COFF import library import type")),
},
import: match header.name_type() {
pe::IMPORT_OBJECT_ORDINAL => None,
pe::IMPORT_OBJECT_NAME => Some(data.symbol()),
pe::IMPORT_OBJECT_NAME_NO_PREFIX => Some(strip_prefix(data.symbol())),
pe::IMPORT_OBJECT_NAME_UNDECORATE => Some(
strip_prefix(data.symbol())
.split(|&b| b == b'@')
.next()
.unwrap(),
),
pe::IMPORT_OBJECT_NAME_EXPORTAS => data.export(),
_ => return Err(Error("Unknown COFF import library name type")),
}
.map(ByteString),
})
}
/// Get the machine type.
pub fn architecture(&self) -> Architecture {
match self.header.machine.get(LE) {
pe::IMAGE_FILE_MACHINE_ARMNT => Architecture::Arm,
pe::IMAGE_FILE_MACHINE_ARM64 => Architecture::Aarch64,
pe::IMAGE_FILE_MACHINE_I386 => Architecture::I386,
pe::IMAGE_FILE_MACHINE_AMD64 => Architecture::X86_64,
_ => Architecture::Unknown,
}
}
/// The public symbol name.
pub fn symbol(&self) -> &'data [u8] {
self.symbol.0
}
/// The name of the DLL to import the symbol from.
pub fn dll(&self) -> &'data [u8] {
self.dll.0
}
/// The name exported from the DLL.
pub fn import(&self) -> ImportName<'data> {
match self.import {
Some(name) => ImportName::Name(name.0),
None => ImportName::Ordinal(self.header.ordinal_or_hint.get(LE)),
}
}
/// The type of import. Usually either a function or data.
pub fn import_type(&self) -> ImportType {
self.kind
}
}
/// The name or ordinal to import from a DLL.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ImportName<'data> {
/// Import by ordinal. Ordinarily this is a 1-based index.
Ordinal(u16),
/// Import by name.
Name(&'data [u8]),
}
/// The kind of import symbol.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum ImportType {
/// An executable code symbol.
Code,
/// A data symbol.
Data,
/// A constant value.
Const,
}
impl pe::ImportObjectHeader {
/// Read the short import header.
///
/// Also checks that the signature and version are valid.
/// Directly following this header will be the string data.
pub fn parse<'data, R: ReadRef<'data>>(data: R, offset: &mut u64) -> Result<&'data Self> {
let header = data
.read::<pe::ImportObjectHeader>(offset)
.read_error("Invalid COFF import library header size")?;
if header.sig1.get(LE) != 0 || header.sig2.get(LE) != pe::IMPORT_OBJECT_HDR_SIG2 {
Err(Error("Invalid COFF import library header"))
} else if header.version.get(LE) != 0 {
Err(Error("Unknown COFF import library header version"))
} else {
Ok(header)
}
}
/// Parse the data following the header.
pub fn parse_data<'data, R: ReadRef<'data>>(
&self,
data: R,
offset: &mut u64,
) -> Result<ImportObjectData<'data>> {
let mut data = Bytes(
data.read_bytes(offset, u64::from(self.size_of_data.get(LE)))
.read_error("Invalid COFF import library data size")?,
);
let symbol = data
.read_string()
.map(ByteString)
.read_error("Could not read COFF import library symbol name")?;
let dll = data
.read_string()
.map(ByteString)
.read_error("Could not read COFF import library DLL name")?;
let export = if self.name_type() == pe::IMPORT_OBJECT_NAME_EXPORTAS {
data.read_string()
.map(ByteString)
.map(Some)
.read_error("Could not read COFF import library export name")?
} else {
None
};
Ok(ImportObjectData {
symbol,
dll,
export,
})
}
/// The type of import.
///
/// This is one of the `IMPORT_OBJECT_*` constants.
pub fn import_type(&self) -> u16 {
self.name_type.get(LE) & pe::IMPORT_OBJECT_TYPE_MASK
}
/// The type of import name.
///
/// This is one of the `IMPORT_OBJECT_*` constants.
pub fn name_type(&self) -> u16 {
(self.name_type.get(LE) >> pe::IMPORT_OBJECT_NAME_SHIFT) & pe::IMPORT_OBJECT_NAME_MASK
}
}
/// The data following `ImportObjectHeader`.
#[derive(Debug, Clone)]
pub struct ImportObjectData<'data> {
symbol: ByteString<'data>,
dll: ByteString<'data>,
export: Option<ByteString<'data>>,
}
impl<'data> ImportObjectData<'data> {
/// The public symbol name.
pub fn symbol(&self) -> &'data [u8] {
self.symbol.0
}
/// The name of the DLL to import the symbol from.
pub fn dll(&self) -> &'data [u8] {
self.dll.0
}
/// The name exported from the DLL.
///
/// This is only set if the name is not derived from the symbol name.
pub fn export(&self) -> Option<&'data [u8]> {
self.export.map(|export| export.0)
}
}