Subject: [PATCH 18/24] powerpc/mm: Move/simplify faulthandler_disabled() and !mm check

From: Benjamin Herrenschmidt <[email-masked]>
Date: Wed, 19 Jul 2017 14:49:40 +1000

Do the check before we re-enable interrupts and clean the code
up a bit.

Signed-off-by: Benjamin Herrenschmidt <[email-masked]>
---
 arch/powerpc/mm/fault.c | 27 +++++++++++++--------------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 6f3a2437008a..c5859ffd3a96 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -355,24 +355,23 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
 	if (unlikely(!is_user && bad_kernel_fault(is_exec, error_code, address)))
 		return SIGSEGV;
 
+	/*
+	 * If we're in an interrupt, have no user context or are running
+	 * in a region with pagefaults disabled then we must not take the fault
+	 */
+	if (unlikely(faulthandler_disabled() || !mm)) {
+		if (is_user)
+			printk_ratelimited(KERN_ERR "Page fault in user mode"
+					   " with faulthandler_disabled()=%d"
+					   " mm=%=p\n",
+					   faulthandler_disabled(), mm);
+		return bad_area_nosemaphore(regs, address);
+	}
+
 	/* We restore the interrupt state now */
 	if (!arch_irq_disabled_regs(regs))
 		local_irq_enable();
 
-	if (faulthandler_disabled() || mm == NULL) {
-		if (!is_user)
-			return SIGSEGV;
-
-		/* faulthandler_disabled() in user mode is really bad,
-		   as is current->mm == NULL. */
-		printk(KERN_EMERG "Page fault in user mode with "
-		       "faulthandler_disabled() = %d mm = %p\n",
-		       faulthandler_disabled(), mm);
-		printk(KERN_EMERG "NIP = %lx  MSR = %lx\n",
-		       regs->nip, regs->msr);
-		die("Weird page fault", regs, SIGSEGV);
-	}
-
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 
 	/*
-- 
2.13.3