acpi_protect: Fix unaligned memory access

[PG-MANA]

This PR fixes unaligned access while protecting ACPI tables.
This fixes #19 .

[fukai-t]

LGTM

[fukai-t]

@PG-MANA
I approved this PR. Please merge this PR.
By the way, do you have any idea to find this kind of bugs efficiently?

[PG-MANA]

By the way, do you have any idea to find this kind of bugs efficiently?

It may be efficient to replace memory accesses like unsafe{*&(address as *const ...)} to read_unaligned or write_unaligned , but it may cause some overheads.

[fukai-t]

In my understanding, replacing all unsafe memory access with *_unaligned may cause performance overhead, but there is no trivial method to find memory access that may not be alingned.

If so, I think following is interesting items for MilvusVisor (just idea, not todo).

• Revealing the performance overhead of *_unaligned by some experiments
• Considering some method to automatically finding unaligned memory access if the *_unaligned cause non-negligible performance overhead.