arm64: barriers: introduce nops and __nops macros for NOP sequences

NOP sequences tend to get used for padding out alternative sections and uarch-specific pipeline flushes in errata workarounds. This patch adds macros for generating these sequences as both inline asm blocks, but also as strings suitable for embedding in other asm blocks directly. Signed-off-by: Will Deacon <[email protected]>
joeyli · Sep 9, 2016 · f99a250 · f99a250
1 parent 8a71f0c
commit f99a250
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diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
@@ -86,6 +86,15 @@
 	dmb	\opt
 	.endm
 
+/*
+ * NOP sequence
+ */
+	.macro	nops, num
+	.rept	\num
+	nop
+	.endr
+	.endm
+
 /*
  * Emit an entry into the exception table
  */

diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
@@ -20,6 +20,9 @@
 
 #ifndef __ASSEMBLY__
 
+#define __nops(n)	".rept	" #n "\nnop\n.endr\n"
+#define nops(n)		asm volatile(__nops(n))
+
 #define sev()		asm volatile("sev" : : : "memory")
 #define wfe()		asm volatile("wfe" : : : "memory")
 #define wfi()		asm volatile("wfi" : : : "memory")