[MIPS] Disallow CpU exception in kernel again.

The commit 4d40bff7110e9e1a97ff8c01bdd6350e9867cc10 ("Allow CpU
exception in kernel partially") was broken.  The commit was to fix
theoretical problem but broke usual case.  Revert it for now.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 3 insertions, 18 deletions

diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 7d76a85422b2..6b356f62289e 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -757,11 +757,12 @@ asmlinkage void do_cpu(struct pt_regs *regs)
 {
         unsigned int cpid;
 
+        die_if_kernel("do_cpu invoked from kernel context!", regs);
+
         cpid = (regs->cp0_cause >> CAUSEB_CE) & 3;
 
         switch (cpid) {
         case 0:
-                die_if_kernel("do_cpu invoked from kernel context!", regs);
                 if (!cpu_has_llsc)
                         if (!simulate_llsc(regs))
                                 return;
@@ -772,9 +773,6 @@ asmlinkage void do_cpu(struct pt_regs *regs)
                 break;
 
         case 1:
-                if (!test_thread_flag(TIF_ALLOW_FP_IN_KERNEL))
-                        die_if_kernel("do_cpu invoked from kernel context!",
-                                      regs);
                 if (used_math())        /* Using the FPU again.  */
                         own_fpu(1);
                 else {                  /* First time FPU user.  */
@@ -782,19 +780,7 @@ asmlinkage void do_cpu(struct pt_regs *regs)
                         set_used_math();
                 }
 
-                if (raw_cpu_has_fpu) {
-                        if (test_thread_flag(TIF_ALLOW_FP_IN_KERNEL)) {
-                                local_irq_disable();
-                                if (cpu_has_fpu)
-                                        regs->cp0_status |= ST0_CU1;
-                                /*
-                                 * We must return without enabling
-                                 * interrupts to ensure keep FPU
-                                 * ownership until resume.
-                                 */
-                                return;
-                        }
-                } else {
+                if (!raw_cpu_has_fpu) {
                         int sig;
                         sig = fpu_emulator_cop1Handler(regs,
                                                 &current->thread.fpu, 0);
@@ -836,7 +822,6 @@ asmlinkage void do_cpu(struct pt_regs *regs)
 
         case 2:
         case 3:
-                die_if_kernel("do_cpu invoked from kernel context!", regs);
                 break;
         }