[PATCH] powerpc/fscr: Enable interrupts earlier before calling get_user()

[Anshuman Khandual <khandual@linux.vnet.ibm.com>]

The function get_user() can sleep while trying to fetch instruction
from user address space and causes the following warning from the
scheduler.

BUG: sleeping function called from invalid context

Though interrupts get enabled back but it happens bit later after
get_user() is called. This change moves enabling these interrupts
earlier covering the function get_user(). While at this, lets check
for kernel mode and crash as this interrupt should not have been
triggered from the kernel context.

Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
---
 arch/powerpc/kernel/traps.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 1e48d15..4d5a55e 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -1611,6 +1611,13 @@ void facility_unavailable_exception(struct pt_regs *regs)
 	else
 		value = mfspr(SPRN_FSCR);
 
+	/* We should not have taken this interrupt in kernel */
+	BUG_ON(!user_mode(regs));
+
+	/* We restore the interrupt state now */
+	if (!arch_irq_disabled_regs(regs))
+		local_irq_enable();
+
 	status = value >> 56;
 	if (status == FSCR_DSCR_LG) {
 		/*
@@ -1683,10 +1690,6 @@ void facility_unavailable_exception(struct pt_regs *regs)
 	    facility_strings[status])
 		facility = facility_strings[status];
 
-	/* We restore the interrupt state now */
-	if (!arch_irq_disabled_regs(regs))
-		local_irq_enable();
-
 	pr_err_ratelimited("%sFacility '%s' unavailable (%d), exception at 0x%lx, MSR=%lx\n",
 		hv ? "Hypervisor " : "", facility, status, regs->nip, regs->msr);
 
-- 
2.9.3