[PATCH v2 02/19] arm64: implement ifence_array_ptr()

[Dan Williams]

From: Mark Rutland <mark.rutland@xxxxxxx>

This patch implements ifence_array_ptr() for arm64, using an
LDR+CSEL+CSDB sequence to inhibit speculative use of the returned value.

Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 arch/arm64/include/asm/barrier.h |   24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
index 77651c49ef44..74ffcddb26e6 100644
--- a/arch/arm64/include/asm/barrier.h
+++ b/arch/arm64/include/asm/barrier.h
@@ -40,6 +40,30 @@
 #define dma_rmb()	dmb(oshld)
 #define dma_wmb()	dmb(oshst)
 
+#define ifence_array_ptr(arr, idx, sz)					\
+({									\
+	typeof(&(arr)[0]) __nap_arr = (arr);				\
+	typeof(idx) __nap_idx = (idx);					\
+	typeof(sz) __nap_sz = (sz);					\
+									\
+	unsigned long __nap_ptr = (unsigned long)__nap_arr +		\
+				  sizeof(__nap_arr[0]) * idx;		\
+									\
+	asm volatile(							\
+	"	cmp	%[i], %[s]\n"					\
+	"	b.cs	1f\n"						\
+	"	ldr	%[p], %[pp]\n"					\
+	"1:	csel	%[p], %[p], xzr, cc\n"				\
+	"	hint	#0x14 // CSDB\n"				\
+	: [p] "=&r" (__nap_ptr)						\
+	: [pp] "m" (__nap_ptr),						\
+	  [i] "r" ((unsigned long)__nap_idx),				\
+	  [s] "r" ((unsigned long)__nap_sz)				\
+	: "cc");							\
+									\
+	(typeof(&(__nap_arr)[0]))__nap_ptr;				\
+})
+
 #define __smp_mb()	dmb(ish)
 #define __smp_rmb()	dmb(ishld)
 #define __smp_wmb()	dmb(ishst)