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Re: Getting rid of alignment faults in userspace

On 06/17/2011 01:10 PM, Somebody in the thread at some point said:

Hi -

I've recently become aware that a few packages are causing alignment
faults on ARM, and are relying on the alignment fixup emulation code in
the kernel in order to work.

Just a FYI a lot of later ARM chips are solving alignment fixups in hardware in the Bus Interface Unit, so the problems won't show up in kernel stats.

Such faults are very expensive in terms of CPU cycles, and can generally
only result from wrong code (for example, C/C++ code which violates the
relevant language standards, assembler which makes invalid assumptions,
or functions called with misaligned pointers due to other bugs).

Agreed it's usually evidence of something broken and / or evil in the code.

There is still going to be a small cost even in hardware fixup so this is very much worth solving despite it's "becoming invisible" because the chips are hiding / solving it already.


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