[PATCH] ARM: fix PTRACE_SETVFPREGS on SMP systems

[Will Deacon]

On Tue, May 31, 2016 at 07:15:03PM +0100, Russell King wrote:
> PTRACE_SETVFPREGS fails to properly mark the VFP register set to be
> reloaded, because it undoes one of the effects of vfp_flush_hwstate().
> 
> Specifically vfp_flush_hwstate() sets thread->vfpstate.hard.cpu to
> an invalid CPU number, but vfp_set() overwrites this with the original
> CPU number, thereby rendering the hardware state as apparently "valid",
> even though the software state is more recent.
> 
> Fix this by reverting the previous change.
> 
> Cc: <stable at vger.kernel.org>
> Fixes: 8130b9d7b9d8 ("ARM: 7308/1: vfp: flush thread hwstate before copying ptrace registers")
> Signed-off-by: Russell King <rmk+kernel at armlinux.org.uk>
> ---
> Will, please ack this.

Acked-by: Will Deacon <will.deacon at arm.com>

Will

> 
>  arch/arm/kernel/ptrace.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
> index ef9119f7462e..4d9375814b53 100644
> --- a/arch/arm/kernel/ptrace.c
> +++ b/arch/arm/kernel/ptrace.c
> @@ -733,8 +733,8 @@ static int vfp_set(struct task_struct *target,
>  	if (ret)
>  		return ret;
>  
> -	vfp_flush_hwstate(thread);
>  	thread->vfpstate.hard = new_vfp;
> +	vfp_flush_hwstate(thread);
>  
>  	return 0;
>  }
> -- 
> 2.1.0
> 
> 
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