mm::read_phys alignment bug

[Qubasa]

mm::read_phys uses read_volatile, read_volatile however requires the pointer to be aligned by the size of the pointer given when in debug mode.
This will break in situations like acpi discovery where table pointers are not necessarily 32 bit aligned in memory.

pub unsafe fn read_volatile<T>(src: *const T) -> T {
    if cfg!(debug_assertions) && !is_aligned_and_not_null(src) {
        // Not panicking to keep codegen impact smaller.
        abort();
    }
    // SAFETY: the caller must uphold the safety contract for `volatile_load`.
    unsafe { intrinsics::volatile_load(src) }
}

/// Checks whether `ptr` is properly aligned with respect to
/// `align_of::<T>()`.
pub(crate) fn is_aligned_and_not_null<T>(ptr: *const T) -> bool {
    !ptr.is_null() && ptr as usize % mem::align_of::<T>() == 0
}

active toolchain
----------------

nightly-x86_64-unknown-linux-gnu (default)
rustc 1.49.0-nightly (ffa2e7ae8 2020-10-24)