[kvm-unit-tests PATCH 3/3] arm: fpu: Fix the input/output args for inline asm in fpu.c

[Raghavendra Rao Ananta <rananta@google.com>]

The macros fpu_reg_{read,write} post-increment the '__val'
pointer register as a part of 'stp' and 'ldp' instructions.
As a result, mark it with "+r" for the compiler to treat it
as read-write operand.

On the contrary, sve_reg_read() never updates the value of the
pointer/register. Hence, mark this as "r" for the compiler to
treat it as read-only operand.

Without these adjustments, the compiler can potentially perform
optimizations over the registers holding the pointers that could
lead to data aborts.

Fixes: d47d370c8f ("arm: Add test for FPU/SIMD context save/restore")
Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
---
 arm/fpu.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arm/fpu.c b/arm/fpu.c
index 587b6ea3..6b0411d3 100644
--- a/arm/fpu.c
+++ b/arm/fpu.c
@@ -54,7 +54,7 @@ static inline bool arch_collect_entropy(uint64_t *random)
 		     "stp q26, q27, [%0], #32\n\t"	\
 		     "stp q28, q29, [%0], #32\n\t"	\
 		     "stp q30, q31, [%0], #32\n\t"	\
-		     : "=r" (__val)			\
+		     : "+r" (__val)			\
 		     :					\
 		     : "v0", "v1", "v2", "v3",		\
 			"v4", "v5", "v6", "v7",		\
@@ -87,8 +87,8 @@ do {							\
 		     "ldp q26, q27, [%0], #32\n\t"	\
 		     "ldp q28, q29, [%0], #32\n\t"	\
 		     "ldp q30, q31, [%0], #32\n\t"	\
+		     : "+r" (__val)			\
 		     :					\
-		     : "r" (__val)			\
 		     : "v0", "v1", "v2", "v3",		\
 			"v4", "v5", "v6", "v7",		\
 			"v8", "v9", "v10", "v11",	\
@@ -138,8 +138,8 @@ do {							\
 		     "str z29, [%0, #29, MUL VL]\n"	\
 		     "str z30, [%0, #30, MUL VL]\n"	\
 		     "str z31, [%0, #31, MUL VL]\n"	\
-		     : "=r" (__val)			\
 		     :					\
+		     : "r" (__val)			\
 		     : "z0", "z1", "z2", "z3",		\
 			"z4", "z5", "z6", "z7",		\
 			"z8", "z9", "z10", "z11",	\
-- 
2.47.0.105.g07ac214952-goog