Re: Architectures where unaligned access is (not) OK?

[Kurt Roeckx <kurt@roeckx.be>]

On Fri, Nov 21, 2014 at 12:42:34PM +0000, Simon McVittie wrote:
> A couple of questions for people who know low-level things:
> 
> * Of Debian's architectures (official and otherwise), which ones are
>   known/defined/designed to be OK with unaligned accesses from
>   user-space, and which ones (can be configured to) crash or give wrong
>   answers?

This is what OpenSSL uses:
#define STRICT_ALIGNMENT 1
#ifndef PEDANTIC
#if defined(__i386)     || defined(__i386__)    || \
    defined(__x86_64)   || defined(__x86_64__)  || \
    defined(_M_IX86)    || defined(_M_AMD64)    || defined(_M_X64) || \
    defined(__aarch64__)                        || \
    defined(__s390__)   || defined(__s390x__)
# undef STRICT_ALIGNMENT
#endif
#endif

I assume that's the list they ended up with not having issues with
it so far. I think I've seen one issue or an other on almost
all the architectures, even if the wiki claims it works.

man prctl says:
       PR_SET_UNALIGN
              (Only  on:  ia64,  since  Linux  2.3.48;  parisc,
since  Linux  2.6.15;  PowerPC,  since  Linux  2.6.18; Alpha,
since Linux 2.6.22) 



Kurt