On Mon, Jun 10, 2013 at 01:00:01PM +0530, Jayachandran C wrote:
> Kernel threads should be able to use COP2 if the platform needs it.
> Do not call die_if_kernel() for a coprocessor unusable exception if
> the exception due to COP2 usage. Instead, the default notifier for
> COP2 exceptions is updated to call die_if_kernel.
>
> Signed-off-by: Jayachandran C <jchandra@xxxxxxxxxxxx>
> ---
> arch/mips/kernel/traps.c | 15 +++++----------
> 1 file changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
> index beba1e6..142d2be 100644
> --- a/arch/mips/kernel/traps.c
> +++ b/arch/mips/kernel/traps.c
> @@ -1056,15 +1056,9 @@ static int default_cu2_call(struct notifier_block *nfb, unsigned long action,
> {
> struct pt_regs *regs = data;
>
> - switch (action) {
> - default:
> - die_if_kernel("Unhandled kernel unaligned access or invalid "
> + die_if_kernel("COP2: Unhandled kernel unaligned access or invalid "
> "instruction", regs);
> - /* Fall through */
> -
> - case CU2_EXCEPTION:
> - force_sig(SIGILL, current);
> - }
> + force_sig(SIGILL, current);
>
> return NOTIFY_OK;
> }
The idea for cu2_chain notifiers is that they should return a value with
NOTIFY_STOP_MASK set. That would prevent further calls to other notifiers.
The default_cu2_call() notifier is installed with the lowest possible
priority and is meant to only be called if there is no other notifier was
installed, that is on a bog standard MIPS core with no CP2.
> @@ -1080,10 +1074,11 @@ asmlinkage void do_cpu(struct pt_regs *regs)
> unsigned long __maybe_unused flags;
>
> prev_state = exception_enter();
> - die_if_kernel("do_cpu invoked from kernel context!", regs);
> -
> cpid = (regs->cp0_cause >> CAUSEB_CE) & 3;
>
> + if (cpid != 2)
> + die_if_kernel("do_cpu invoked from kernel context!", regs);
> +
> switch (cpid) {
> case 0:
> epc = (unsigned int __user *)exception_epc(regs);
I'm ok with this segment.
Ralf
