Re: [PATCH for-6.2 12/43] target/sh4: Implement do_unaligned_access for user-only

[Richard Henderson]

On 7/29/21 3:52 AM, Peter Maydell wrote:
> sh4 kernel default for unaligned accesses seems to be "warn and fixup",
> not SIGBUS, unless the user changes that by writing to /proc/cpu/alignment
> or the process changes it via prctl().

We will still need this for load-locked/store-conditional (MOVLI/MOVCO).

It appears that the sh4 kernel fails to decode these properly, and will do something ugly, 
like interpreting MOVLI as a multiple-store instead of a load.

There are also other instructions that the kernel does not attempt to handle, such as MAC. 
 I suppose we could begin with turning off TARGET_ALIGNED_ONLY for sh4-linux-user, then 
re-enabling MO_ALIGN for the atomics (at least).


r~