MIPS: Allow kernel to use coprocessor 2

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@broadcom.com>
Cc: linux-mips@linux-mips.org
Cc: ddaney.cavm@gmail.com
Patchwork: https://patchwork.linux-mips.org/patch/5415/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 5 insertions, 10 deletions

diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index beba1e616b6e..142d2bede024 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;
 }
@@ -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);