diff --git a/kani-compiler/src/kani_middle/transform/check_values.rs b/kani-compiler/src/kani_middle/transform/check_values.rs index 4888e032af4f..a620dfabb72e 100644 --- a/kani-compiler/src/kani_middle/transform/check_values.rs +++ b/kani-compiler/src/kani_middle/transform/check_values.rs @@ -440,7 +440,13 @@ impl<'a> MirVisitor for CheckValueVisitor<'a> { // The write bytes intrinsic may trigger UB in safe code. // pub unsafe fn write_bytes(dst: *mut T, val: u8, count: usize) // - // We don't support this operation yet. + // This is an over-approximation since writing an invalid value is + // not UB, only reading it will be. + assert_eq!( + args.len(), + 3, + "Unexpected number of arguments for `write_bytes`" + ); let TyKind::RigidTy(RigidTy::RawPtr(target_ty, Mutability::Mut)) = args[0].ty(self.locals).unwrap().kind() else { @@ -449,6 +455,19 @@ impl<'a> MirVisitor for CheckValueVisitor<'a> { let validity = ty_validity_per_offset(&self.machine, target_ty, 0); match validity { Ok(ranges) if ranges.is_empty() => {} + Ok(ranges) => { + let sz = Const::try_from_uint( + target_ty.layout().unwrap().shape().size.bytes() + as u128, + UintTy::Usize, + ) + .unwrap(); + self.push_target(SourceOp::BytesValidity { + target_ty, + rvalue: Rvalue::Repeat(args[1].clone(), sz), + ranges, + }) + } _ => self.push_target(SourceOp::UnsupportedCheck { check: "write_bytes".to_string(), ty: target_ty, diff --git a/tests/kani/ValidValues/maybe_uninit.rs b/tests/kani/ValidValues/maybe_uninit.rs new file mode 100644 index 000000000000..620ad8ef5ba3 --- /dev/null +++ b/tests/kani/ValidValues/maybe_uninit.rs @@ -0,0 +1,21 @@ +// Copyright Kani Contributors +// SPDX-License-Identifier: Apache-2.0 OR MIT +// kani-flags: -Z valid-value-checks +//! Check that Kani can identify UB when converting from a maybe uninit(). + +use std::mem::MaybeUninit; +use std::num::NonZeroI64; + +#[kani::proof] +pub fn check_valid_zeroed() { + let maybe = MaybeUninit::zeroed(); + let val: u128 = unsafe { maybe.assume_init() }; + assert_eq!(val, 0); +} + +#[kani::proof] +#[kani::should_panic] +pub fn check_invalid_zeroed() { + let maybe = MaybeUninit::zeroed(); + let _val: NonZeroI64 = unsafe { maybe.assume_init() }; +} diff --git a/tests/kani/ValidValues/write_bytes.rs b/tests/kani/ValidValues/write_bytes.rs new file mode 100644 index 000000000000..e4f73b1f3479 --- /dev/null +++ b/tests/kani/ValidValues/write_bytes.rs @@ -0,0 +1,21 @@ +// Copyright Kani Contributors +// SPDX-License-Identifier: Apache-2.0 OR MIT +// kani-flags: -Z valid-value-checks +//! Check that Kani can identify UB when using write_bytes for initializing a variable. +#![feature(core_intrinsics)] + +#[kani::proof] +#[kani::should_panic] +pub fn check_invalid_write() { + let mut val = 'a'; + let ptr = &mut val as *mut char; + // Should fail given that we wrote invalid value to array of char. + unsafe { std::intrinsics::write_bytes(ptr, kani::any(), 1) }; +} + +#[kani::proof] +pub fn check_valid_write() { + let mut val = 10u128; + let ptr = &mut val as *mut _; + unsafe { std::intrinsics::write_bytes(ptr, kani::any(), 1) }; +}