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SubjectRe: [PATCH 4.4 12/23] ARC: [arcompact] handle unaligned access delay slot corner case
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On Tue, 2017-01-31 at 06:37 +0100, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
>
> ------------------
>
> From: Vineet Gupta <vgupta@synopsys.com>
>
> commit 9aed02feae57bf7a40cb04ea0e3017cb7a998db4 upstream.
>
> After emulating an unaligned access in delay slot of a branch, we
> pretend as the delay slot never happened - so return back to actual
> branch target (or next PC if branch was not taken).
>
> Curently we did this by handling STATUS32.DE, we also need to clear the
> BTA.T bit, which is disregarded when returning from original misaligned
> exception, but could cause weirdness if it took the interrupt return
> path (in case interrupt was acive too)
>
> One ARC700 customer ran into this when enabling unaligned access fixup
> for kernel mode accesses as well
>
> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> ---
>  arch/arc/kernel/unaligned.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> --- a/arch/arc/kernel/unaligned.c
> +++ b/arch/arc/kernel/unaligned.c
> @@ -241,8 +241,9 @@ int misaligned_fixup(unsigned long addre
>   if (state.fault)
>   goto fault;
>  
> + /* clear any remanants of delay slot */
>   if (delay_mode(regs)) {
> - regs->ret = regs->bta;
> + regs->ret = regs->bta ~1U;

Unless you're doing something terrible with macros, this is missing an
& operator. I doubt this even compiled (looks like it's only used in
some ARC configurations).

Ben.

>   regs->status32 &= ~STATUS_DE_MASK;
>   } else {
>   regs->ret += state.instr_len;



--
Ben Hutchings
It's easier to fight for one's principles than to live up to them.

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