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The alignment round-up used rz + align - (rz % align) which is wrong when rz is already a multiple of align as it ends up as rz + align. On 32-bit targets align may be size_of::<GuestAddr>() == 4, which is smaller than the 8-byte shadow alignment. The over-alignment then leaves data at 4 mod 8. Use rz + ((align - (rz % align)) % align) so the pointer is only advanced when it is not already aligned.
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Description
The alignment round-up used
rz + align - (rz % align)which is wrong whenrzis already a multiple ofalignas it ends up asrz + align. On 32-bit targetsalignmay besize_of::<GuestAddr>() == 4, which is smaller than the 8-byte shadow alignment. The over-alignment then leavesdataat 4 mod 8.Use
rz + ((align - (rz % align)) % align)so the pointer is only advanced when it is not already aligned.Checklist
./scripts/precommit.shand addressed all comments