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>

1 files changed, 4 insertions, 6 deletions

diff --git a/arch/arm/mm/cache-v7.S b/arch/arm/mm/cache-v7.S
index a655d3da386d..39e3fb3db801 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 @@ ENTRY(v7_coherent_user_range)
         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 @@ ENTRY(v7_coherent_user_range)
 
 /*
  * 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)