arm64: explicitly mask all exceptions

There are a few places where we want to mask all exceptions. Today we
do this in a piecemeal fashion, typically we expect the caller to
have masked irqs and the arch code masks debug exceptions, ignoring
serror which is probably masked.

Make it clear that 'mask all exceptions' is the intention by adding
helpers to do exactly that.

This will let us unmask SError without having to add 'oh and SError'
to these paths.

Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Julien Thierry <julien.thierry@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

2 files changed, 86 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 3128a9ca5701..a4aa22241dd1 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -32,6 +32,23 @@
 #include <asm/ptrace.h>
 #include <asm/thread_info.h>
 
+	.macro save_and_disable_daif, flags
+	mrs	\flags, daif
+	msr	daifset, #0xf
+	.endm
+
+	.macro disable_daif
+	msr	daifset, #0xf
+	.endm
+
+	.macro enable_daif
+	msr	daifclr, #0xf
+	.endm
+
+	.macro	restore_daif, flags:req
+	msr	daif, \flags
+	.endm
+
 /*
  * Enable and disable interrupts.
  */
diff --git a/arch/arm64/include/asm/daifflags.h b/arch/arm64/include/asm/daifflags.h
new file mode 100644
index 000000000000..55e2598a8c4c
--- /dev/null
+++ b/arch/arm64/include/asm/daifflags.h
@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2017 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_DAIFFLAGS_H
+#define __ASM_DAIFFLAGS_H
+
+#include <linux/irqflags.h>
+
+/* mask/save/unmask/restore all exceptions, including interrupts. */
+static inline void local_daif_mask(void)
+{
+	asm volatile(
+		"msr	daifset, #0xf		// local_daif_mask\n"
+		:
+		:
+		: "memory");
+	trace_hardirqs_off();
+}
+
+static inline unsigned long local_daif_save(void)
+{
+	unsigned long flags;
+
+	asm volatile(
+		"mrs	%0, daif		// local_daif_save\n"
+		: "=r" (flags)
+		:
+		: "memory");
+	local_daif_mask();
+
+	return flags;
+}
+
+static inline void local_daif_unmask(void)
+{
+	trace_hardirqs_on();
+	asm volatile(
+		"msr	daifclr, #0xf		// local_daif_unmask"
+		:
+		:
+		: "memory");
+}
+
+static inline void local_daif_restore(unsigned long flags)
+{
+	if (!arch_irqs_disabled_flags(flags))
+		trace_hardirqs_on();
+	asm volatile(
+		"msr	daif, %0		// local_daif_restore"
+		:
+		: "r" (flags)
+		: "memory");
+	if (arch_irqs_disabled_flags(flags))
+		trace_hardirqs_off();
+}
+
+#endif