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hypervisor: aarch64: remove undefined behaviour in offset__of
The variable tmp was never initialized. Calling assume_init when the content is not yet initialized causes immediate undefined behaviour. We also cannot create any intermediate references because they will be subject to the same requirements for references -- the referred object must be valid. Signed-off-by: Wei Liu <liuwe@microsoft.com>
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@ -36,13 +36,23 @@ pub use {kvm_ioctls::Cap, kvm_ioctls::Kvm};
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macro_rules! offset__of {
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macro_rules! offset__of {
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($str:ty, $($field:ident)+) => ({
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($str:ty, $($field:ident)+) => ({
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let tmp: std::mem::MaybeUninit<$str> = std::mem::MaybeUninit::uninit();
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let tmp: std::mem::MaybeUninit<$str> = std::mem::MaybeUninit::uninit();
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let tmp = unsafe { tmp.assume_init() };
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let base = tmp.as_ptr();
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let base = &tmp as *const _ as usize;
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let member = &tmp.$($field)* as *const _ as usize;
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member - base
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// Avoid warnings when nesting `unsafe` blocks.
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#[allow(unused_unsafe)]
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// SAFETY: The pointer is valid and aligned, just not initialised. Using `addr_of` ensures
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// that we don't actually read from `base` (which would be UB) nor create an intermediate
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// reference.
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let member = unsafe { core::ptr::addr_of!((*base).$($field)*) } as *const u8;
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// Avoid warnings when nesting `unsafe` blocks.
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#[allow(unused_unsafe)]
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// SAFETY: The two pointers are within the same allocated object `tmp`. All requirements
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// from offset_from are upheld.
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unsafe { member.offset_from(base as *const u8) as usize }
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});
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});
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}
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}
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// Get the ID of a core register
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// Get the ID of a core register
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#[macro_export]
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#[macro_export]
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macro_rules! arm64_core_reg_id {
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macro_rules! arm64_core_reg_id {
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