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// Copyright 2018 pdb Developers // // Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or // http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or // http://opensource.org/licenses/MIT>, at your option. This file may not be // copied, modified, or distributed except according to those terms. //! Utilities for translating addresses between PDB offsets and _Relative Virtual Addresses_ (RVAs). use std::cmp::Ordering; use std::mem; use std::slice; use common::*; use msf::Stream; use pe::ImageSectionHeader; /// A address translation record from an `OMAPTable`. /// /// This record applies to the half-open interval [ `record.source_address`, /// `next_record.source_address` ). #[repr(C, packed)] #[derive(Clone, Copy, Debug, Eq, PartialEq)] pub struct OMAPRecord { source_address: u32, target_address: u32, } impl OMAPRecord { /// Returns the address in the source space. #[inline] pub fn source_address(self) -> u32 { u32::from_le(self.source_address) } /// Returns the start of the mapped portion in the target address space. #[inline] pub fn target_address(self) -> u32 { u32::from_le(self.target_address) } } impl PartialOrd for OMAPRecord { #[inline] fn partial_cmp(&self, other: &Self) -> Option<Ordering> { self.source_address().partial_cmp(&other.source_address()) } } impl Ord for OMAPRecord { #[inline] fn cmp(&self, other: &Self) -> Ordering { self.source_address().cmp(&other.source_address()) } } /// PDBs can contain OMAP tables, which translate relative virtual addresses (RVAs) from one address /// space into another. /// /// For more information on the pratical use of OMAPs, see the [module level documentation] and /// [`AddressMap`]. A PDB can contain two OMAPs: /// /// - `omap_from_src`: A mapping from the original address space to the transformed address space /// of an optimized binary. Use `PDB::omap_from_src` to obtain an instance of this OMAP. Also, /// `PdbInternalRva::rva` performs this conversion in a safe manner. /// - `omap_to_src`: A mapping from the transformed address space back into the original address /// space of the unoptimized binary. Use `PDB::omap_to_src` to obtain an instace of this OMAP. /// Also, `Rva::original_rva` performs this conversion in a safe manner. /// /// # Structure /// /// OMAP tables are dense arrays, sequentially storing `OMAPRecord` structs sorted by source /// address. /// /// Each record applies to a range of addresses: i.e. record N indicates that addresses in the /// half-open interval [ `record[n].source_address`, `record[n+1].source_address` ) were relocated /// to a starting address of `record[n].target_address`. If `target_address` is zero, the `lookup()` /// will return None, since this indicates a non-existent location in the target address space. /// /// Given that the table is sorted, lookups by source address can be efficiently serviced using a /// binary search directly against the underlying data without secondary data structures. This is /// not the most cache efficient data structure (especially given that half of each cache line is /// storing target addresses), but given that OMAP tables are an uncommon PDBs feature, the obvious /// binary search implementation seems appropriate. /// /// [module level documentation]: ./index.html /// [`AddressMap`]: struct.AddressMap.html #[derive(Debug)] pub struct OMAPTable<'s> { stream: Stream<'s>, } impl<'s> OMAPTable<'s> { pub(crate) fn parse(stream: Stream<'s>) -> Result<Self> { if stream.as_slice().len() % 8 != 0 { Err(Error::UnimplementedFeature( "OMAP tables must be a multiple of the record size", )) } else { Ok(OMAPTable { stream }) } } /// Returns a direct view onto the records stored in this OMAP table. #[inline] pub fn records(&self) -> &'s [OMAPRecord] { let bytes = self.stream.as_slice(); unsafe { slice::from_raw_parts( bytes.as_ptr() as *const OMAPRecord, bytes.len() / mem::size_of::<OMAPRecord>(), ) } } /// Look up `source_address` to yield a target address. /// /// Note that `lookup()` can return zero, which (probably) means that `source_address` does not /// exist in the target address space. This is not a lookup failure per sé, so it's not a /// `Result::Error`, and zero _is_ a valid address, so it's not an `Option::None`. It's just /// zero. pub fn lookup(&self, source_address: u32) -> Option<u32> { let records = self.records(); let index = match records.binary_search_by_key(&source_address, |r| r.source_address()) { Ok(i) => i, Err(0) => return None, Err(i) => i - 1, }; let record = records[index]; // As a special case, `target_address` can be zero, which seems to indicate that the // `source_address` does not exist in the target address space. if record.target_address() == 0 { return None; } debug_assert!(record.source_address() <= source_address); Some((source_address - record.source_address()) + record.target_address()) } } /// A mapping between addresses and offsets used in the PDB and PE file. /// /// To obtain an instace of this address map, call `PDB::address_map`. It will determine the correct /// translation mode and read all internal state from the PDB. Then use the conversion methods on /// the address and offset types to translate addresses. /// /// # Background /// /// Addresses in PDBs are stored as offsets into sections of the PE file. The `AddressMap` contains /// the PE's section headers to translate between the offsets and virtual addresses relative to the /// image base (RVAs). /// /// Additionally, Microsoft has been reordering the Windows system and application binaries to /// optimize them for paging reduction, using a toolset reported to be derived from and/or built on /// top of the [Vulcan research project]. Relatively little else is known about the tools or the /// methods they use. Looking at Windows system binaries like `ntoskrnl.exe`, it is apparent that /// their layout has been rearranged, and their respective symbol files contain _OMAP_ re-mapping /// information. The [Microsoft Binary Technologies Projects] may be involved in this. /// /// The internals of this transformation are not well understood. According to [1997 reference /// material]: /// /// > Yet another form of debug information is relatively new and undocumented, except for a few /// > obscure references in `WINNT.H` and the Win32 SDK help. This type of information is known as /// > OMAP. Apparently, as part of Microsoft's internal build procedure, small fragments of code in /// > EXEs and DLLs are moved around to put the most commonly used code at the beginning of the code /// > section. This presumably keeps the process memory working set as small as possible. However, /// > when shifting around the blocks of code, the corresponding debug information isn't updated. /// > Instead, OMAP information is created. It lets symbol table code translate between the original /// > address in a symbol table and the modified address where the variable or line of code really /// > exists in memory. /// /// # Usage /// /// To aid with translating addresses and offsets, this module exposes `AddressMap`, a helper that /// contains all information to apply the correct translation of any kind of address or offset to /// another. Due to the rearranging optimizations, there are four types involved: /// /// - [`Rva`]: A _Relative Virtual Address_ in the actual binary. This address directly corresponds /// to instruction pointers seen in stack traces and symbol addresses reported by debuggers. /// - [`PdbInternalRva`]: An RVA as it would have appeared before the optimization. This value does /// not have any practical use, as it never occurs in the PDB or the actual binary. /// - [`SectionOffset`]: An offset into a section of the actual binary. A `section` member of _n_ /// refers to section _n - 1_, which makes a section number of _0_ a null pointer. /// - [`PdbInternalSectionOffset`]: An offset into a section of the original binary. These offsets /// are used throughout the PDB and can be converted to either `SectionOffset`, or directly to /// `Rva` in the actual address space. /// /// For binaries that have not been optimized that way, the `PdbInternal*` values are effectively /// equal to their regular counterparts and the conversion between the two are no-ops. Address /// translation still has to assume different address spaces, which is why there is no direct /// conversion without an `AddressMap`. /// /// # Example /// /// ```rust /// # use pdb::{Rva, FallibleIterator}; /// # /// # fn test() -> pdb::Result<()> { /// # let source = std::fs::File::open("fixtures/self/foo.pdb")?; /// let mut pdb = pdb::PDB::open(source)?; /// /// // Compute the address map once and reuse it /// let address_map = pdb.address_map()?; /// /// # let symbol_table = pdb.global_symbols()?; /// # let symbol = symbol_table.iter().next()?.unwrap(); /// # match symbol.parse() { Ok(pdb::SymbolData::PublicSymbol(pubsym)) => { /// // Obtain some section offset, eg from a symbol, and convert it /// match pubsym.offset.to_rva(&address_map) { /// Some(rva) => { /// println!("symbol is at {}", rva); /// # assert_eq!(rva, Rva(26048)); /// } /// None => { /// println!("symbol refers to eliminated code"); /// # panic!("symbol should exist"); /// } /// } /// # } _ => unreachable!() } /// # Ok(()) /// # } /// # test().unwrap() /// ``` /// /// [Vulcan research project]: https://research.microsoft.com/pubs/69850/tr-2001-50.pdf /// [Microsoft Binary Technologies Projects]: https://microsoft.com/windows/cse/bit_projects.mspx /// [1997 reference material]: https://www.microsoft.com/msj/0597/hood0597.aspx /// [`Rva`]: struct.Rva.html /// [`PdbInternalRva`]: struct.PdbInternalRva.html /// [`SectionOffset`]: struct.SectionOffset.html /// [`PdbInternalSectionOffset`]: struct.PdbInternalSectionOffset.html pub struct AddressMap<'s> { pub(crate) original_sections: Vec<ImageSectionHeader>, pub(crate) transformed_sections: Option<Vec<ImageSectionHeader>>, pub(crate) transformed_to_original: Option<OMAPTable<'s>>, pub(crate) original_to_transformed: Option<OMAPTable<'s>>, } fn get_section_offset(sections: &[ImageSectionHeader], address: u32) -> Option<(u16, u32)> { // Section headers are sorted by virtual_address, so we only need to iterate until we exceed // the desired address. Since the number of section headers is relatively low, a sequential // search is the fastest option here. let (index, section) = sections .iter() .take_while(|s| s.virtual_address <= address) .enumerate() .find(|(_, s)| address < s.virtual_address + s.size_of_raw_data)?; Some((index as u16 + 1, address - section.virtual_address)) } fn get_virtual_address(sections: &[ImageSectionHeader], section: u16, offset: u32) -> Option<u32> { let section = sections.get(section as usize - 1)?; Some(section.virtual_address + offset) } impl Rva { pub fn to_internal_rva(self, translator: &AddressMap) -> Option<PdbInternalRva> { match translator.transformed_to_original { Some(ref omap) => omap.lookup(self.0).map(PdbInternalRva), None => Some(PdbInternalRva(self.0)), } } pub fn to_section_offset(self, translator: &AddressMap) -> Option<SectionOffset> { let (section, offset) = match translator.transformed_sections { Some(ref sections) => get_section_offset(sections, self.0)?, None => get_section_offset(&translator.original_sections, self.0)?, }; Some(SectionOffset { section, offset }) } pub fn to_internal_offset(self, translator: &AddressMap) -> Option<PdbInternalSectionOffset> { self.to_internal_rva(translator)?.to_internal_offset(translator) } } impl PdbInternalRva { pub fn to_rva(self, translator: &AddressMap) -> Option<Rva> { match translator.original_to_transformed { Some(ref omap) => omap.lookup(self.0).map(Rva), None => Some(Rva(self.0)), } } pub fn to_section_offset(self, translator: &AddressMap) -> Option<SectionOffset> { self.to_rva(translator)?.to_section_offset(translator) } pub fn to_internal_offset(self, translator: &AddressMap) -> Option<PdbInternalSectionOffset> { let (section, offset) = get_section_offset(&translator.original_sections, self.0)?; Some(PdbInternalSectionOffset { section, offset }) } } impl SectionOffset { pub fn to_rva(self, translator: &AddressMap) -> Option<Rva> { let address = match translator.transformed_sections { Some(ref sections) => get_virtual_address(sections, self.section, self.offset)?, None => get_virtual_address(&translator.original_sections, self.section, self.offset)?, }; Some(Rva(address)) } pub fn to_internal_rva(self, translator: &AddressMap) -> Option<PdbInternalRva> { self.to_rva(translator)?.to_internal_rva(translator) } pub fn to_internal_offset(self, translator: &AddressMap) -> Option<PdbInternalSectionOffset> { if translator.transformed_sections.is_none() { // Fast path to avoid section table lookups let SectionOffset { section, offset } = self; return Some(PdbInternalSectionOffset { section, offset }); } self.to_internal_rva(translator)?.to_internal_offset(translator) } } impl PdbInternalSectionOffset { pub fn to_rva(self, translator: &AddressMap) -> Option<Rva> { self.to_internal_rva(translator)?.to_rva(translator) } pub fn to_internal_rva(self, translator: &AddressMap) -> Option<PdbInternalRva> { get_virtual_address(&translator.original_sections, self.section, self.offset) .map(PdbInternalRva) } pub fn to_section_offset(self, translator: &AddressMap) -> Option<SectionOffset> { if translator.transformed_sections.is_none() { // Fast path to avoid section table lookups let PdbInternalSectionOffset { section, offset } = self; return Some(SectionOffset { section, offset }); } self.to_rva(translator)?.to_section_offset(translator) } }