70 lines
2.6 KiB
Rust
70 lines
2.6 KiB
Rust
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use rustc_miri::interpret::{
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Pointer,
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EvalResult, EvalError,
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PrimVal,
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EvalContext,
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};
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use rustc::ty::Ty;
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pub trait EvalContextExt<'tcx> {
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fn wrapping_pointer_offset(
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&self,
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ptr: Pointer,
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pointee_ty: Ty<'tcx>,
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offset: i64,
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) -> EvalResult<'tcx, Pointer>;
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fn pointer_offset(
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&self,
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ptr: Pointer,
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pointee_ty: Ty<'tcx>,
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offset: i64,
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) -> EvalResult<'tcx, Pointer>;
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}
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impl<'a, 'tcx> EvalContextExt<'tcx> for EvalContext<'a, 'tcx, super::Evaluator> {
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fn wrapping_pointer_offset(
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&self,
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ptr: Pointer,
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pointee_ty: Ty<'tcx>,
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offset: i64,
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) -> EvalResult<'tcx, Pointer> {
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// FIXME: assuming here that type size is < i64::max_value()
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let pointee_size = self.type_size(pointee_ty)?.expect("cannot offset a pointer to an unsized type") as i64;
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let offset = offset.overflowing_mul(pointee_size).0;
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ptr.wrapping_signed_offset(offset, self)
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}
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fn pointer_offset(
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&self,
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ptr: Pointer,
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pointee_ty: Ty<'tcx>,
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offset: i64,
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) -> EvalResult<'tcx, Pointer> {
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// This function raises an error if the offset moves the pointer outside of its allocation. We consider
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// ZSTs their own huge allocation that doesn't overlap with anything (and nothing moves in there because the size is 0).
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// We also consider the NULL pointer its own separate allocation, and all the remaining integers pointers their own
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// allocation.
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if ptr.is_null()? { // NULL pointers must only be offset by 0
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return if offset == 0 { Ok(ptr) } else { Err(EvalError::InvalidNullPointerUsage) };
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}
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// FIXME: assuming here that type size is < i64::max_value()
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let pointee_size = self.type_size(pointee_ty)?.expect("cannot offset a pointer to an unsized type") as i64;
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return if let Some(offset) = offset.checked_mul(pointee_size) {
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let ptr = ptr.signed_offset(offset, self)?;
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// Do not do bounds-checking for integers; they can never alias a normal pointer anyway.
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if let PrimVal::Ptr(ptr) = ptr.into_inner_primval() {
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self.memory.check_bounds(ptr, false)?;
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} else if ptr.is_null()? {
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// We moved *to* a NULL pointer. That seems wrong, LLVM considers the NULL pointer its own small allocation. Reject this, for now.
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return Err(EvalError::InvalidNullPointerUsage);
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}
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Ok(ptr)
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} else {
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Err(EvalError::OverflowingMath)
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}
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}
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}
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