ARM: 7408/1: cacheflush: return error to userspace when flushing syscall fails

The cacheflush syscall can fail for two reasons:

(1) The arguments are invalid (nonsensical address range or no VMA)

(2) The region generates a translation fault on a VIPT or PIPT cache

This patch allows do_cache_op to return an error code to userspace in
the case of the above. The various coherent_user_range implementations
are modified to return 0 in the case of VIVT caches or -EFAULT in the
case of an abort on v6/v7 cores.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mm/cache-v7.S b/arch/arm/mm/cache-v7.S
index a655d3d..39e3fb3 100644
--- a/arch/arm/mm/cache-v7.S
+++ b/arch/arm/mm/cache-v7.S
@@ -13,6 +13,7 @@
 #include <linux/linkage.h>
 #include <linux/init.h>
 #include <asm/assembler.h>
+#include <asm/errno.h>
 #include <asm/unwind.h>
 
 #include "proc-macros.S"
@@ -198,7 +199,6 @@
 	add	r12, r12, r2
 	cmp	r12, r1
 	blo	2b
-3:
 	mov	r0, #0
 	ALT_SMP(mcr	p15, 0, r0, c7, c1, 6)	@ invalidate BTB Inner Shareable
 	ALT_UP(mcr	p15, 0, r0, c7, c5, 6)	@ invalidate BTB
@@ -208,13 +208,11 @@
 
 /*
  * Fault handling for the cache operation above. If the virtual address in r0
- * isn't mapped, just try the next page.
+ * isn't mapped, fail with -EFAULT.
  */
 9001:
-	mov	r12, r12, lsr #12
-	mov	r12, r12, lsl #12
-	add	r12, r12, #4096
-	b	3b
+	mov	r0, #-EFAULT
+	mov	pc, lr
  UNWIND(.fnend		)
 ENDPROC(v7_coherent_kern_range)
 ENDPROC(v7_coherent_user_range)