Read short import files

crates/examples/src/objdump.rs

@@ -1,6 +1,7 @@
 use object::read::archive::ArchiveFile;
+use object::read::coff;
 use object::read::macho::{DyldCache, FatArch, FatHeader};
-use object::{Endianness, Object, ObjectComdat, ObjectSection, ObjectSymbol};
+use object::{Endianness, FileKind, Object, ObjectComdat, ObjectSection, ObjectSymbol};
 use std::io::{Result, Write};
 
 pub fn print<W: Write, E: Write>(
@@ -21,7 +22,11 @@ pub fn print<W: Write, E: Write>(
                         writeln!(w)?;
                         writeln!(w, "{}:", String::from_utf8_lossy(member.name()))?;
                         if let Ok(data) = member.data(file) {
-                            dump_object(w, e, data)?;
+                            if FileKind::parse(data) == Ok(FileKind::CoffImportFile) {
+                                dump_import(w, e, data)?;
+                            } else {
+                                dump_object(w, e, data)?;
+                            }
                         }
                     }
                 }
@@ -245,3 +250,25 @@ fn dump_parsed_object<W: Write, E: Write>(w: &mut W, e: &mut E, file: &object::F
 
     Ok(())
 }
+
+fn dump_import<W: Write, E: Write>(w: &mut W, e: &mut E, data: &[u8]) -> Result<()> {
+    let file = match coff::CoffImportFile::parse(data) {
+        Ok(import) => import,
+        Err(err) => {
+            writeln!(e, "Failed to parse short import: {}", err)?;
+            return Ok(());
+        }
+    };
+
+    writeln!(w, "Format: Short Import File")?;
+    writeln!(w, "Architecture: {:?}", file.architecture())?;
+    writeln!(w, "DLL: {:?}", String::from_utf8_lossy(file.dll()))?;
+    writeln!(w, "Symbol: {:?}", String::from_utf8_lossy(file.symbol()))?;
+    write!(w, "Import: ")?;
+    match file.import() {
+        coff::ImportName::Ordinal(n) => writeln!(w, "Ordinal({})", n)?,
+        coff::ImportName::Name(name) => writeln!(w, "Name({:?})", String::from_utf8_lossy(name))?,
+    }
+    writeln!(w, "Type: {:?}", file.import_type())?;
+    Ok(())
+}

src/read/coff/import.rs

@@ -0,0 +1,145 @@
+//! 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. This is not an object file.
+#[derive(Debug, Clone)]
+pub struct CoffImportFile<'data> {
+    header: &'data pe::ImportObjectHeader,
+    dll: ByteString<'data>,
+    symbol: ByteString<'data>,
+    kind: ImportType,
+    import: Option<ByteString<'data>>,
+}
+impl<'data> CoffImportFile<'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_size = header.size_of_data.get(LE);
+        let mut strings = Bytes(
+            data.read_bytes(&mut offset, data_size as u64)
+                .read_error("Invalid COFF import library data size")?,
+        );
+        let symbol = strings
+            .read_string()
+            .read_error("Could not read COFF import library symbol name")?;
+        let dll = strings
+            .read_string()
+            .read_error("Could not read COFF import library DLL name")?;
+
+        // 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: ByteString(dll),
+            symbol: ByteString(symbol),
+            kind: match header.name_type.get(LE) & 0b11 {
+                pe::IMPORT_OBJECT_CODE => ImportType::Code,
+                pe::IMPORT_OBJECT_DATA => ImportType::Data,
+                pe::IMPORT_OBJECT_CONST => ImportType::Const,
+                0b11 => return Err(Error("Invalid COFF import library import type")),
+                _ => unreachable!("COFF import library ImportType must be a two bit number"),
+            },
+            import: match (header.name_type.get(LE) >> 2) & 0b111 {
+                pe::IMPORT_OBJECT_ORDINAL => None,
+                pe::IMPORT_OBJECT_NAME => Some(symbol),
+                pe::IMPORT_OBJECT_NAME_NO_PREFIX => Some(strip_prefix(symbol)),
+                pe::IMPORT_OBJECT_NAME_UNDECORATE => {
+                    Some(strip_prefix(symbol).split(|&b| b == b'@').next().unwrap())
+                }
+                pe::IMPORT_OBJECT_NAME_EXPORTAS => Some(
+                    strings
+                        .read_string()
+                        .read_error("Could not read COFF import library export name")?,
+                ),
+                5..=7 => return Err(Error("Unknown COFF import library name type")),
+                _ => unreachable!("COFF import library name type must be a three bit number"),
+            }
+            .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 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 public symbol name
+    pub fn symbol(&self) -> &'data [u8] {
+        self.symbol.0
+    }
+}
+
+/// The name or ordinal to import.
+#[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.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum ImportType {
+    /// Executable code
+    Code,
+    /// Some data
+    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::<crate::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)
+        }
+    }
+}

src/read/coff/mod.rs

@@ -16,3 +16,6 @@ pub use relocation::*;
 
 mod comdat;
 pub use comdat::*;
+
+mod import;
+pub use import::*;

src/read/mod.rs

@@ -156,6 +156,9 @@ pub enum FileKind {
     /// This supports a larger number of sections.
     #[cfg(feature = "coff")]
     CoffBig,
+    /// A Windows short import file.
+    #[cfg(feature = "coff")]
+    CoffImportFile,
     /// A dyld cache file containing Mach-O images.
     #[cfg(feature = "macho")]
     DyldCache,
@@ -263,6 +266,8 @@ impl FileKind {
             [0x01, 0xDF, ..] => FileKind::Xcoff32,
             #[cfg(feature = "xcoff")]
             [0x01, 0xF7, ..] => FileKind::Xcoff64,
+            #[cfg(feature = "coff")]
+            [0, 0, 0xFF, 0xFF, ..] => FileKind::CoffImportFile,
             _ => return Err(Error("Unknown file magic")),
         };
         Ok(kind)