linux-kernel - [PATCH 4.20 152/183] ARCv2: Enable unaligned access in early ASM code

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Date:   Mon, 25 Feb 2019 22:12:05 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        Vineet Gupta <vgupta@...opsys.com>
Subject: [PATCH 4.20 152/183] ARCv2: Enable unaligned access in early ASM code

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>

commit 252f6e8eae909bc075a1b1e3b9efb095ae4c0b56 upstream.

It is currently done in arc_init_IRQ() which might be too late
considering gcc 7.3.1 onwards (GNU 2018.03) generates unaligned
memory accesses by default

Cc: stable@...r.kernel.org #4.4+
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
[vgupta: rewrote changelog]
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arc/kernel/head.S |   10 ++++++++++
 1 file changed, 10 insertions(+)

--- a/arch/arc/kernel/head.S
+++ b/arch/arc/kernel/head.S
@@ -17,6 +17,7 @@
 #include <asm/entry.h>
 #include <asm/arcregs.h>
 #include <asm/cache.h>
+#include <asm/irqflags.h>
 
 .macro CPU_EARLY_SETUP
 
@@ -47,6 +48,15 @@
 	sr	r5, [ARC_REG_DC_CTRL]
 
 1:
+
+#ifdef CONFIG_ISA_ARCV2
+	; Unaligned access is disabled at reset, so re-enable early as
+	; gcc 7.3.1 (ARC GNU 2018.03) onwards generates unaligned access
+	; by default
+	lr	r5, [status32]
+	bset	r5, r5, STATUS_AD_BIT
+	kflag	r5
+#endif
 .endm
 
 	.section .init.text, "ax",@progbits