ARM: spectre-v1: add speculation barrier (csdb) macros

Add assembly and C macros for the new CSDB instruction.
Signed-off-by: NRussell King <rmk+kernel@armlinux.org.uk>
Acked-by: NMark Rutland <mark.rutland@arm.com>
Boot-tested-by: NTony Lindgren <tony@atomide.com>
Reviewed-by: NTony Lindgren <tony@atomide.com>

arch/arm/include/asm/assembler.h

@@ -447,6 +447,14 @@ THUMB(	orr	\reg , \reg , #PSR_T_BIT	)
 	.size \name , . - \name
 	.endm
 
+	.macro	csdb
+#ifdef CONFIG_THUMB2_KERNEL
+	.inst.w	0xf3af8014
+#else
+	.inst	0xe320f014
+#endif
+	.endm
+
 	.macro check_uaccess, addr:req, size:req, limit:req, tmp:req, bad:req
 #ifndef CONFIG_CPU_USE_DOMAINS
 	adds	\tmp, \addr, #\size - 1

arch/arm/include/asm/barrier.h

@@ -17,6 +17,12 @@
 #define isb(option) __asm__ __volatile__ ("isb " #option : : : "memory")
 #define dsb(option) __asm__ __volatile__ ("dsb " #option : : : "memory")
 #define dmb(option) __asm__ __volatile__ ("dmb " #option : : : "memory")
+#ifdef CONFIG_THUMB2_KERNEL
+#define CSDB	".inst.w 0xf3af8014"
+#else
+#define CSDB	".inst	0xe320f014"
+#endif
+#define csdb() __asm__ __volatile__(CSDB : : : "memory")
 #elif defined(CONFIG_CPU_XSC3) || __LINUX_ARM_ARCH__ == 6
 #define isb(x) __asm__ __volatile__ ("mcr p15, 0, %0, c7, c5, 4" \
 				    : : "r" (0) : "memory")
@@ -37,6 +43,13 @@
 #define dmb(x) __asm__ __volatile__ ("" : : : "memory")
 #endif
 
+#ifndef CSDB
+#define CSDB
+#endif
+#ifndef csdb
+#define csdb()
+#endif
+
 #ifdef CONFIG_ARM_HEAVY_MB
 extern void (*soc_mb)(void);
 extern void arm_heavy_mb(void);