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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:18:32 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:18:32 +0000 |
commit | 4547b622d8d29df964fa2914213088b148c498fc (patch) | |
tree | 9fc6b25f3c3add6b745be9a2400a6e96140046e9 /compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs | |
parent | Releasing progress-linux version 1.66.0+dfsg1-1~progress7.99u1. (diff) | |
download | rustc-4547b622d8d29df964fa2914213088b148c498fc.tar.xz rustc-4547b622d8d29df964fa2914213088b148c498fc.zip |
Merging upstream version 1.67.1+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs | 321 |
1 files changed, 321 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs b/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs new file mode 100644 index 000000000..ddd3f3943 --- /dev/null +++ b/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs @@ -0,0 +1,321 @@ +//! Store the provenance for each byte in the range, with a more efficient +//! representation for the common case where PTR_SIZE consecutive bytes have the same provenance. + +use std::cmp; + +use rustc_data_structures::sorted_map::SortedMap; +use rustc_target::abi::{HasDataLayout, Size}; + +use super::{alloc_range, AllocError, AllocId, AllocRange, AllocResult, Provenance}; +use rustc_serialize::{Decodable, Decoder, Encodable, Encoder}; + +/// Stores the provenance information of pointers stored in memory. +#[derive(Clone, PartialEq, Eq, Hash, Debug)] +#[derive(HashStable)] +pub struct ProvenanceMap<Prov = AllocId> { + /// Provenance in this map applies from the given offset for an entire pointer-size worth of + /// bytes. Two entires in this map are always at least a pointer size apart. + ptrs: SortedMap<Size, Prov>, + /// Provenance in this map only applies to the given single byte. + /// This map is disjoint from the previous. It will always be empty when + /// `Prov::OFFSET_IS_ADDR` is false. + bytes: Option<Box<SortedMap<Size, Prov>>>, +} + +impl<D: Decoder, Prov: Provenance + Decodable<D>> Decodable<D> for ProvenanceMap<Prov> { + fn decode(d: &mut D) -> Self { + assert!(!Prov::OFFSET_IS_ADDR); // only `AllocId` is ever serialized + Self { ptrs: Decodable::decode(d), bytes: None } + } +} + +impl<S: Encoder, Prov: Provenance + Encodable<S>> Encodable<S> for ProvenanceMap<Prov> { + fn encode(&self, s: &mut S) { + let Self { ptrs, bytes } = self; + assert!(!Prov::OFFSET_IS_ADDR); // only `AllocId` is ever serialized + debug_assert!(bytes.is_none()); + ptrs.encode(s) + } +} + +impl<Prov> ProvenanceMap<Prov> { + pub fn new() -> Self { + ProvenanceMap { ptrs: SortedMap::new(), bytes: None } + } + + /// The caller must guarantee that the given provenance list is already sorted + /// by address and contain no duplicates. + pub fn from_presorted_ptrs(r: Vec<(Size, Prov)>) -> Self { + ProvenanceMap { ptrs: SortedMap::from_presorted_elements(r), bytes: None } + } +} + +impl ProvenanceMap { + /// Give access to the ptr-sized provenances (which can also be thought of as relocations, and + /// indeed that is how codegen treats them). + /// + /// Only exposed with `AllocId` provenance, since it panics if there is bytewise provenance. + #[inline] + pub fn ptrs(&self) -> &SortedMap<Size, AllocId> { + debug_assert!(self.bytes.is_none()); // `AllocId::OFFSET_IS_ADDR` is false so this cannot fail + &self.ptrs + } +} + +impl<Prov: Provenance> ProvenanceMap<Prov> { + /// Returns all ptr-sized provenance in the given range. + /// If the range has length 0, returns provenance that crosses the edge between `start-1` and + /// `start`. + fn range_get_ptrs(&self, range: AllocRange, cx: &impl HasDataLayout) -> &[(Size, Prov)] { + // We have to go back `pointer_size - 1` bytes, as that one would still overlap with + // the beginning of this range. + let adjusted_start = Size::from_bytes( + range.start.bytes().saturating_sub(cx.data_layout().pointer_size.bytes() - 1), + ); + self.ptrs.range(adjusted_start..range.end()) + } + + /// Returns all byte-wise provenance in the given range. + fn range_get_bytes(&self, range: AllocRange) -> &[(Size, Prov)] { + if let Some(bytes) = self.bytes.as_ref() { + bytes.range(range.start..range.end()) + } else { + &[] + } + } + + /// Get the provenance of a single byte. + pub fn get(&self, offset: Size, cx: &impl HasDataLayout) -> Option<Prov> { + let prov = self.range_get_ptrs(alloc_range(offset, Size::from_bytes(1)), cx); + debug_assert!(prov.len() <= 1); + if let Some(entry) = prov.first() { + // If it overlaps with this byte, it is on this byte. + debug_assert!(self.bytes.as_ref().map_or(true, |b| b.get(&offset).is_none())); + Some(entry.1) + } else { + // Look up per-byte provenance. + self.bytes.as_ref().and_then(|b| b.get(&offset).copied()) + } + } + + /// Check if here is ptr-sized provenance at the given index. + /// Does not mean anything for bytewise provenance! But can be useful as an optimization. + pub fn get_ptr(&self, offset: Size) -> Option<Prov> { + self.ptrs.get(&offset).copied() + } + + /// Returns whether this allocation has provenance overlapping with the given range. + /// + /// Note: this function exists to allow `range_get_provenance` to be private, in order to somewhat + /// limit access to provenance outside of the `Allocation` abstraction. + /// + pub fn range_empty(&self, range: AllocRange, cx: &impl HasDataLayout) -> bool { + self.range_get_ptrs(range, cx).is_empty() && self.range_get_bytes(range).is_empty() + } + + /// Yields all the provenances stored in this map. + pub fn provenances(&self) -> impl Iterator<Item = Prov> + '_ { + let bytes = self.bytes.iter().flat_map(|b| b.values()); + self.ptrs.values().chain(bytes).copied() + } + + pub fn insert_ptr(&mut self, offset: Size, prov: Prov, cx: &impl HasDataLayout) { + debug_assert!(self.range_empty(alloc_range(offset, cx.data_layout().pointer_size), cx)); + self.ptrs.insert(offset, prov); + } + + /// Removes all provenance inside the given range. + /// If there is provenance overlapping with the edges, might result in an error. + pub fn clear(&mut self, range: AllocRange, cx: &impl HasDataLayout) -> AllocResult { + let start = range.start; + let end = range.end(); + // Clear the bytewise part -- this is easy. + if Prov::OFFSET_IS_ADDR { + if let Some(bytes) = self.bytes.as_mut() { + bytes.remove_range(start..end); + } + } else { + debug_assert!(self.bytes.is_none()); + } + + // For the ptr-sized part, find the first (inclusive) and last (exclusive) byte of + // provenance that overlaps with the given range. + let (first, last) = { + // Find all provenance overlapping the given range. + let provenance = self.range_get_ptrs(range, cx); + if provenance.is_empty() { + // No provenance in this range, we are done. + return Ok(()); + } + + ( + provenance.first().unwrap().0, + provenance.last().unwrap().0 + cx.data_layout().pointer_size, + ) + }; + + // We need to handle clearing the provenance from parts of a pointer. + if first < start { + if !Prov::OFFSET_IS_ADDR { + // We can't split up the provenance into less than a pointer. + return Err(AllocError::PartialPointerOverwrite(first)); + } + // Insert the remaining part in the bytewise provenance. + let prov = self.ptrs[&first]; + let bytes = self.bytes.get_or_insert_with(Box::default); + for offset in first..start { + bytes.insert(offset, prov); + } + } + if last > end { + let begin_of_last = last - cx.data_layout().pointer_size; + if !Prov::OFFSET_IS_ADDR { + // We can't split up the provenance into less than a pointer. + return Err(AllocError::PartialPointerOverwrite(begin_of_last)); + } + // Insert the remaining part in the bytewise provenance. + let prov = self.ptrs[&begin_of_last]; + let bytes = self.bytes.get_or_insert_with(Box::default); + for offset in end..last { + bytes.insert(offset, prov); + } + } + + // Forget all the provenance. + // Since provenance do not overlap, we know that removing until `last` (exclusive) is fine, + // i.e., this will not remove any other provenance just after the ones we care about. + self.ptrs.remove_range(first..last); + + Ok(()) + } +} + +/// A partial, owned list of provenance to transfer into another allocation. +/// +/// Offsets are already adjusted to the destination allocation. +pub struct ProvenanceCopy<Prov> { + dest_ptrs: Option<Box<[(Size, Prov)]>>, + dest_bytes: Option<Box<[(Size, Prov)]>>, +} + +impl<Prov: Provenance> ProvenanceMap<Prov> { + pub fn prepare_copy( + &self, + src: AllocRange, + dest: Size, + count: u64, + cx: &impl HasDataLayout, + ) -> AllocResult<ProvenanceCopy<Prov>> { + let shift_offset = move |idx, offset| { + // compute offset for current repetition + let dest_offset = dest + src.size * idx; // `Size` operations + // shift offsets from source allocation to destination allocation + (offset - src.start) + dest_offset // `Size` operations + }; + let ptr_size = cx.data_layout().pointer_size; + + // # Pointer-sized provenances + // Get the provenances that are entirely within this range. + // (Different from `range_get_ptrs` which asks if they overlap the range.) + // Only makes sense if we are copying at least one pointer worth of bytes. + let mut dest_ptrs_box = None; + if src.size >= ptr_size { + let adjusted_end = Size::from_bytes(src.end().bytes() - (ptr_size.bytes() - 1)); + let ptrs = self.ptrs.range(src.start..adjusted_end); + // If `count` is large, this is rather wasteful -- we are allocating a big array here, which + // is mostly filled with redundant information since it's just N copies of the same `Prov`s + // at slightly adjusted offsets. The reason we do this is so that in `mark_provenance_range` + // we can use `insert_presorted`. That wouldn't work with an `Iterator` that just produces + // the right sequence of provenance for all N copies. + // Basically, this large array would have to be created anyway in the target allocation. + let mut dest_ptrs = Vec::with_capacity(ptrs.len() * (count as usize)); + for i in 0..count { + dest_ptrs + .extend(ptrs.iter().map(|&(offset, reloc)| (shift_offset(i, offset), reloc))); + } + debug_assert_eq!(dest_ptrs.len(), dest_ptrs.capacity()); + dest_ptrs_box = Some(dest_ptrs.into_boxed_slice()); + }; + + // # Byte-sized provenances + // This includes the existing bytewise provenance in the range, and ptr provenance + // that overlaps with the begin/end of the range. + let mut dest_bytes_box = None; + let begin_overlap = self.range_get_ptrs(alloc_range(src.start, Size::ZERO), cx).first(); + let end_overlap = self.range_get_ptrs(alloc_range(src.end(), Size::ZERO), cx).first(); + if !Prov::OFFSET_IS_ADDR { + // There can't be any bytewise provenance, and we cannot split up the begin/end overlap. + if let Some(entry) = begin_overlap { + return Err(AllocError::PartialPointerCopy(entry.0)); + } + if let Some(entry) = end_overlap { + return Err(AllocError::PartialPointerCopy(entry.0)); + } + debug_assert!(self.bytes.is_none()); + } else { + let mut bytes = Vec::new(); + // First, if there is a part of a pointer at the start, add that. + if let Some(entry) = begin_overlap { + trace!("start overlapping entry: {entry:?}"); + // For really small copies, make sure we don't run off the end of the `src` range. + let entry_end = cmp::min(entry.0 + ptr_size, src.end()); + for offset in src.start..entry_end { + bytes.push((offset, entry.1)); + } + } else { + trace!("no start overlapping entry"); + } + // Then the main part, bytewise provenance from `self.bytes`. + if let Some(all_bytes) = self.bytes.as_ref() { + bytes.extend(all_bytes.range(src.start..src.end())); + } + // And finally possibly parts of a pointer at the end. + if let Some(entry) = end_overlap { + trace!("end overlapping entry: {entry:?}"); + // For really small copies, make sure we don't start before `src` does. + let entry_start = cmp::max(entry.0, src.start); + for offset in entry_start..src.end() { + if bytes.last().map_or(true, |bytes_entry| bytes_entry.0 < offset) { + // The last entry, if it exists, has a lower offset than us. + bytes.push((offset, entry.1)); + } else { + // There already is an entry for this offset in there! This can happen when the + // start and end range checks actually end up hitting the same pointer, so we + // already added this in the "pointer at the start" part above. + assert!(entry.0 <= src.start); + } + } + } else { + trace!("no end overlapping entry"); + } + trace!("byte provenances: {bytes:?}"); + + // And again a buffer for the new list on the target side. + let mut dest_bytes = Vec::with_capacity(bytes.len() * (count as usize)); + for i in 0..count { + dest_bytes + .extend(bytes.iter().map(|&(offset, reloc)| (shift_offset(i, offset), reloc))); + } + debug_assert_eq!(dest_bytes.len(), dest_bytes.capacity()); + dest_bytes_box = Some(dest_bytes.into_boxed_slice()); + } + + Ok(ProvenanceCopy { dest_ptrs: dest_ptrs_box, dest_bytes: dest_bytes_box }) + } + + /// Applies a provenance copy. + /// The affected range, as defined in the parameters to `prepare_copy` is expected + /// to be clear of provenance. + pub fn apply_copy(&mut self, copy: ProvenanceCopy<Prov>) { + if let Some(dest_ptrs) = copy.dest_ptrs { + self.ptrs.insert_presorted(dest_ptrs.into()); + } + if Prov::OFFSET_IS_ADDR { + if let Some(dest_bytes) = copy.dest_bytes && !dest_bytes.is_empty() { + self.bytes.get_or_insert_with(Box::default).insert_presorted(dest_bytes.into()); + } + } else { + debug_assert!(copy.dest_bytes.is_none()); + } + } +} |