[PATCH 0/2] ARM VFP exception handling and state corruption fixes

[Tim Gardner]

Brad Figg wrote:
> As requested by Loic Minier:
> 
> This CPU generates synchronous VFP exceptions in a non-standard way -the
> FPEXC.EX bit set but without the FPSCR.IXE bit being set like in the VFP
> subarchitecture 1 or just the FPEXC.DEX bit like in VFP subarchitecture
> 2. The main problem is that the faulty instruction will be re-executed
> indefinitely without being emulated. This patch ensures that the
> VFP exception is treated as synchronous.
> 
> Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
> 
> On Wed, Jan 28, 2009 at 01:09:37PM +0000, Catalin Marinas wrote:
>  > > BTW, the VFP_bounce() function isn't preemption safe (problems and
>  > > suggested fix reported by Lineo in private e-mails but I didn't have
>  > > time to post them to the list yet).
> 
> We've also observed that ARM VFP state can be corrupted during VFP exception
> handling when PREEMPT is enabled.  The exact conditions are difficult
> to reproduce but appear to occur during VFP exception handling when a
> task causes a VFP exception which is handled via VFP_bounce and is then
> preempted by yet another task which in turn causes yet another VFP
> exception.  Since the VFP_bounce code is not preempt safe, VFP state then
> becomes corrupt.  In order to prevent preemption from occuring while
> handling a VFP exception, this patch disables preemption while handling
> VFP exceptions.
> 
> Signed-off-by: George G. Davis <gdavis at mvista.com>
> 

applied

-- 
Tim Gardner tim.gardner at canonical.com