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Rollup merge of rust-lang#133088 - the8472:randomize-me-harder, r=wor…
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…kingjubilee

`-Zrandomize-layout` harder. `Foo<T> != Foo<U>`

Tracking issue: rust-lang#106764

Previously randomize-layout only used a deterministic shuffle based on the seed stored in an Adt's ReprOptions, meaning that `Foo<T>`  and `Foo<U>` were shuffled by the same seed. This change adds a similar seed to each calculated LayoutData so that a struct can be randomized both based on the layout of its fields and its per-type seed.
Primitives start with simple seed derived from some of their properties. Though some types can no longer be distinguished at that point, e.g. usize and u64 will still be treated the same.
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workingjubilee authored Jan 10, 2025
2 parents 62bf38f + d89b6d5 commit 85ff229
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Showing 39 changed files with 400 additions and 78 deletions.
43 changes: 36 additions & 7 deletions compiler/rustc_abi/src/layout.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -119,6 +119,8 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
.chain(Niche::from_scalar(dl, Size::ZERO, a))
.max_by_key(|niche| niche.available(dl));

let combined_seed = a.size(&self.cx).bytes().wrapping_add(b.size(&self.cx).bytes());

LayoutData {
variants: Variants::Single { index: VariantIdx::new(0) },
fields: FieldsShape::Arbitrary {
Expand All @@ -131,6 +133,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
size,
max_repr_align: None,
unadjusted_abi_align: align.abi,
randomization_seed: combined_seed,
}
}

Expand Down Expand Up @@ -223,6 +226,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
size: Size::ZERO,
max_repr_align: None,
unadjusted_abi_align: dl.i8_align.abi,
randomization_seed: 0,
}
}

Expand Down Expand Up @@ -385,6 +389,11 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
return Err(LayoutCalculatorError::EmptyUnion);
};

let combined_seed = only_variant
.iter()
.map(|v| v.randomization_seed)
.fold(repr.field_shuffle_seed, |acc, seed| acc.wrapping_add(seed));

Ok(LayoutData {
variants: Variants::Single { index: only_variant_idx },
fields: FieldsShape::Union(union_field_count),
Expand All @@ -394,6 +403,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
size: size.align_to(align.abi),
max_repr_align,
unadjusted_abi_align,
randomization_seed: combined_seed,
})
}

Expand Down Expand Up @@ -650,6 +660,11 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
BackendRepr::Memory { sized: true }
};

let combined_seed = variant_layouts
.iter()
.map(|v| v.randomization_seed)
.fold(repr.field_shuffle_seed, |acc, seed| acc.wrapping_add(seed));

let layout = LayoutData {
variants: Variants::Multiple {
tag: niche_scalar,
Expand All @@ -671,6 +686,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
align,
max_repr_align,
unadjusted_abi_align,
randomization_seed: combined_seed,
};

Some(TmpLayout { layout, variants: variant_layouts })
Expand Down Expand Up @@ -961,6 +977,11 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {

let largest_niche = Niche::from_scalar(dl, Size::ZERO, tag);

let combined_seed = layout_variants
.iter()
.map(|v| v.randomization_seed)
.fold(repr.field_shuffle_seed, |acc, seed| acc.wrapping_add(seed));

let tagged_layout = LayoutData {
variants: Variants::Multiple {
tag,
Expand All @@ -978,6 +999,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
size,
max_repr_align,
unadjusted_abi_align,
randomization_seed: combined_seed,
};

let tagged_layout = TmpLayout { layout: tagged_layout, variants: layout_variants };
Expand Down Expand Up @@ -1030,12 +1052,15 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
let mut max_repr_align = repr.align;
let mut inverse_memory_index: IndexVec<u32, FieldIdx> = fields.indices().collect();
let optimize_field_order = !repr.inhibit_struct_field_reordering();
if optimize_field_order && fields.len() > 1 {
let end =
if let StructKind::MaybeUnsized = kind { fields.len() - 1 } else { fields.len() };
let optimizing = &mut inverse_memory_index.raw[..end];
let fields_excluding_tail = &fields.raw[..end];
let end = if let StructKind::MaybeUnsized = kind { fields.len() - 1 } else { fields.len() };
let optimizing = &mut inverse_memory_index.raw[..end];
let fields_excluding_tail = &fields.raw[..end];
// unsizable tail fields are excluded so that we use the same seed for the sized and unsized layouts.
let field_seed = fields_excluding_tail
.iter()
.fold(0u64, |acc, f| acc.wrapping_add(f.randomization_seed));

if optimize_field_order && fields.len() > 1 {
// If `-Z randomize-layout` was enabled for the type definition we can shuffle
// the field ordering to try and catch some code making assumptions about layouts
// we don't guarantee.
Expand All @@ -1046,8 +1071,9 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
use rand::seq::SliceRandom;
// `ReprOptions.field_shuffle_seed` is a deterministic seed we can use to randomize field
// ordering.
let mut rng =
rand_xoshiro::Xoshiro128StarStar::seed_from_u64(repr.field_shuffle_seed);
let mut rng = rand_xoshiro::Xoshiro128StarStar::seed_from_u64(
field_seed.wrapping_add(repr.field_shuffle_seed),
);

// Shuffle the ordering of the fields.
optimizing.shuffle(&mut rng);
Expand Down Expand Up @@ -1344,6 +1370,8 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
unadjusted_abi_align
};

let seed = field_seed.wrapping_add(repr.field_shuffle_seed);

Ok(LayoutData {
variants: Variants::Single { index: VariantIdx::new(0) },
fields: FieldsShape::Arbitrary { offsets, memory_index },
Expand All @@ -1353,6 +1381,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
size,
max_repr_align,
unadjusted_abi_align,
randomization_seed: seed,
})
}

Expand Down
39 changes: 39 additions & 0 deletions compiler/rustc_abi/src/lib.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1719,6 +1719,18 @@ pub struct LayoutData<FieldIdx: Idx, VariantIdx: Idx> {
/// Only used on aarch64-linux, where the argument passing ABI ignores the requested alignment
/// in some cases.
pub unadjusted_abi_align: Align,

/// The randomization seed based on this type's own repr and its fields.
///
/// Since randomization is toggled on a per-crate basis even crates that do not have randomization
/// enabled should still calculate a seed so that downstream uses can use it to distinguish different
/// types.
///
/// For every T and U for which we do not guarantee that a repr(Rust) `Foo<T>` can be coerced or
/// transmuted to `Foo<U>` we aim to create probalistically distinct seeds so that Foo can choose
/// to reorder its fields based on that information. The current implementation is a conservative
/// approximation of this goal.
pub randomization_seed: u64,
}

impl<FieldIdx: Idx, VariantIdx: Idx> LayoutData<FieldIdx, VariantIdx> {
Expand All @@ -1739,6 +1751,30 @@ impl<FieldIdx: Idx, VariantIdx: Idx> LayoutData<FieldIdx, VariantIdx> {
let largest_niche = Niche::from_scalar(cx, Size::ZERO, scalar);
let size = scalar.size(cx);
let align = scalar.align(cx);

let range = scalar.valid_range(cx);

// All primitive types for which we don't have subtype coercions should get a distinct seed,
// so that types wrapping them can use randomization to arrive at distinct layouts.
//
// Some type information is already lost at this point, so as an approximation we derive
// the seed from what remains. For example on 64-bit targets usize and u64 can no longer
// be distinguished.
let randomization_seed = size
.bytes()
.wrapping_add(
match scalar.primitive() {
Primitive::Int(_, true) => 1,
Primitive::Int(_, false) => 2,
Primitive::Float(_) => 3,
Primitive::Pointer(_) => 4,
} << 32,
)
// distinguishes references from pointers
.wrapping_add((range.start as u64).rotate_right(16))
// distinguishes char from u32 and bool from u8
.wrapping_add((range.end as u64).rotate_right(16));

LayoutData {
variants: Variants::Single { index: VariantIdx::new(0) },
fields: FieldsShape::Primitive,
Expand All @@ -1748,6 +1784,7 @@ impl<FieldIdx: Idx, VariantIdx: Idx> LayoutData<FieldIdx, VariantIdx> {
align,
max_repr_align: None,
unadjusted_abi_align: align.abi,
randomization_seed,
}
}
}
Expand All @@ -1770,6 +1807,7 @@ where
variants,
max_repr_align,
unadjusted_abi_align,
ref randomization_seed,
} = self;
f.debug_struct("Layout")
.field("size", size)
Expand All @@ -1780,6 +1818,7 @@ where
.field("variants", variants)
.field("max_repr_align", max_repr_align)
.field("unadjusted_abi_align", unadjusted_abi_align)
.field("randomization_seed", randomization_seed)
.finish()
}
}
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_middle/src/ty/layout.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -770,6 +770,7 @@ where
size: Size::ZERO,
max_repr_align: None,
unadjusted_abi_align: tcx.data_layout.i8_align.abi,
randomization_seed: 0,
})
}

Expand Down
10 changes: 10 additions & 0 deletions compiler/rustc_ty_utils/src/layout.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -347,6 +347,7 @@ fn layout_of_uncached<'tcx>(
size,
max_repr_align: None,
unadjusted_abi_align: element.align.abi,
randomization_seed: element.randomization_seed.wrapping_add(count),
})
}
ty::Slice(element) => {
Expand All @@ -360,6 +361,8 @@ fn layout_of_uncached<'tcx>(
size: Size::ZERO,
max_repr_align: None,
unadjusted_abi_align: element.align.abi,
// adding a randomly chosen value to distinguish slices
randomization_seed: element.randomization_seed.wrapping_add(0x2dcba99c39784102),
})
}
ty::Str => tcx.mk_layout(LayoutData {
Expand All @@ -371,6 +374,8 @@ fn layout_of_uncached<'tcx>(
size: Size::ZERO,
max_repr_align: None,
unadjusted_abi_align: dl.i8_align.abi,
// another random value
randomization_seed: 0xc1325f37d127be22,
}),

// Odd unit types.
Expand Down Expand Up @@ -542,6 +547,7 @@ fn layout_of_uncached<'tcx>(
align,
max_repr_align: None,
unadjusted_abi_align: align.abi,
randomization_seed: e_ly.randomization_seed.wrapping_add(e_len),
})
}

Expand Down Expand Up @@ -999,6 +1005,9 @@ fn coroutine_layout<'tcx>(
BackendRepr::Memory { sized: true }
};

// this is similar to how ReprOptions populates its field_shuffle_seed
let def_hash = tcx.def_path_hash(def_id).0.to_smaller_hash().as_u64();

let layout = tcx.mk_layout(LayoutData {
variants: Variants::Multiple {
tag,
Expand All @@ -1019,6 +1028,7 @@ fn coroutine_layout<'tcx>(
align,
max_repr_align: None,
unadjusted_abi_align: align.abi,
randomization_seed: def_hash,
});
debug!("coroutine layout ({:?}): {:#?}", ty, layout);
Ok(layout)
Expand Down
4 changes: 4 additions & 0 deletions src/tools/rust-analyzer/crates/hir-ty/src/layout.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -197,6 +197,7 @@ fn layout_of_simd_ty(
align,
max_repr_align: None,
unadjusted_abi_align: align.abi,
randomization_seed: 0,
}))
}

Expand Down Expand Up @@ -313,6 +314,7 @@ pub fn layout_of_ty_query(
size,
max_repr_align: None,
unadjusted_abi_align: element.align.abi,
randomization_seed: 0,
}
}
TyKind::Slice(element) => {
Expand All @@ -326,6 +328,7 @@ pub fn layout_of_ty_query(
size: Size::ZERO,
max_repr_align: None,
unadjusted_abi_align: element.align.abi,
randomization_seed: 0,
}
}
TyKind::Str => Layout {
Expand All @@ -337,6 +340,7 @@ pub fn layout_of_ty_query(
size: Size::ZERO,
max_repr_align: None,
unadjusted_abi_align: dl.i8_align.abi,
randomization_seed: 0,
},
// Potentially-wide pointers.
TyKind::Ref(_, _, pointee) | TyKind::Raw(_, pointee) => {
Expand Down
2 changes: 2 additions & 0 deletions tests/ui/abi/c-zst.aarch64-darwin.stderr
View file
Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
},
max_repr_align: None,
unadjusted_abi_align: $SOME_ALIGN,
randomization_seed: 0,
},
},
mode: Ignore,
Expand Down Expand Up @@ -49,6 +50,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
},
max_repr_align: None,
unadjusted_abi_align: $SOME_ALIGN,
randomization_seed: 0,
},
},
mode: Ignore,
Expand Down
2 changes: 2 additions & 0 deletions tests/ui/abi/c-zst.powerpc-linux.stderr
View file
Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
},
max_repr_align: None,
unadjusted_abi_align: $SOME_ALIGN,
randomization_seed: 0,
},
},
mode: Indirect {
Expand Down Expand Up @@ -60,6 +61,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
},
max_repr_align: None,
unadjusted_abi_align: $SOME_ALIGN,
randomization_seed: 0,
},
},
mode: Ignore,
Expand Down
2 changes: 2 additions & 0 deletions tests/ui/abi/c-zst.s390x-linux.stderr
View file
Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
},
max_repr_align: None,
unadjusted_abi_align: $SOME_ALIGN,
randomization_seed: 0,
},
},
mode: Indirect {
Expand Down Expand Up @@ -60,6 +61,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
},
max_repr_align: None,
unadjusted_abi_align: $SOME_ALIGN,
randomization_seed: 0,
},
},
mode: Ignore,
Expand Down
2 changes: 2 additions & 0 deletions tests/ui/abi/c-zst.sparc64-linux.stderr
View file
Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
},
max_repr_align: None,
unadjusted_abi_align: $SOME_ALIGN,
randomization_seed: 0,
},
},
mode: Indirect {
Expand Down Expand Up @@ -60,6 +61,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
},
max_repr_align: None,
unadjusted_abi_align: $SOME_ALIGN,
randomization_seed: 0,
},
},
mode: Ignore,
Expand Down
2 changes: 2 additions & 0 deletions tests/ui/abi/c-zst.x86_64-linux.stderr
View file
Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
},
max_repr_align: None,
unadjusted_abi_align: $SOME_ALIGN,
randomization_seed: 0,
},
},
mode: Ignore,
Expand Down Expand Up @@ -49,6 +50,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
},
max_repr_align: None,
unadjusted_abi_align: $SOME_ALIGN,
randomization_seed: 0,
},
},
mode: Ignore,
Expand Down
2 changes: 2 additions & 0 deletions tests/ui/abi/c-zst.x86_64-pc-windows-gnu.stderr
View file
Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
},
max_repr_align: None,
unadjusted_abi_align: $SOME_ALIGN,
randomization_seed: 0,
},
},
mode: Indirect {
Expand Down Expand Up @@ -60,6 +61,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
},
max_repr_align: None,
unadjusted_abi_align: $SOME_ALIGN,
randomization_seed: 0,
},
},
mode: Ignore,
Expand Down
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