[PATCH] ARM: fix PTRACE_SETVFPREGS on SMP systems

[PATCH] ARM: fix PTRACE_SETVFPREGS on SMP systems

[Russell King]

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@vger.kernel.org>
Fixes: 8130b9d7b9d8 ("ARM: 7308/1: vfp: flush thread hwstate before copying ptrace registers")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
---
Will, please ack this.

 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

[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@vger.kernel.org>
> Fixes: 8130b9d7b9d8 ("ARM: 7308/1: vfp: flush thread hwstate before copying ptrace registers")
> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
> ---
> Will, please ack this.

Acked-by: Will Deacon <will.deacon@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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